JP2004328065A - Transmission performance simulation program, transmission performance simulation method, and recording medium storing the program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission performance simulation program for automatically evaluating the performance of an ISDN and an xDSL. <P>SOLUTION: A characteristic as to a transmission system to be evaluated, a characteristic as to a transmission system acting like a crosstalk source, a characteristic of line attenuation, a crosstalk characteristic, and a characteristic as to background noise are first inputted to this simulation tool, which executes calculation. This tool calculates a relation between a length of a transmission line and an SNR (signal power to noise power ratio) or (a transmission speed) of a received signal by taking into account the effect of crosstalk or the like. Further, fitting processing is applied to a prescribed module and a prescribed parameter in the simulation tool so as to bring a calculated value closer to an actually measured value thereby adapting a theoretical value obtained from the simulation to the actually measured value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５８】
ただし、上述の（１）式において、Ｓ（ｆ）は送信信号強度で、単位はｍＷ／Ｈｚであり、後に述べるＰＳＤを用いる。このとき、ｄＢｍ／ＨｚからｍＷ／Ｈｚへ単位の変換を行なう必要がある。
【００５９】
Ｎ（ｆ）は雑音強度で、単位はｍＷ／Ｈｚである。
線路減衰の逆特性である｜Ｈ（ｆ）｜^−２は、後に詳述する線路減衰特性の｜Ｈ（ｆ）｜^２の逆数である。
【００６０】
Ｆ（ｆ）は受信フィルタであり、使用する端末機の特性に依存する。なおＩＳＤＮのシミュレーションにおいては、コサインロールオフフィルタを仮定して、Ｆ（ｆ）を以下の（２）式のように与える。
【００６１】
【数２】

【００６２】
なお、上述の（２）式において、シンボルレートｆ_ｓｙｍは、図３に示される値を用いる。
【００６３】
（１−２）ＡＮＳＩによるリニアイコライザ
ＡＮＳＩ（米国規格協会）の規格によるＩＳＤＮ伝送を対象とする手法である。
【００６４】
ＡＮＳＩによるリニアイコライザによって、求めるＳＮＲ（ｄＢ）は次の（３）式に示される。
【００６５】
【数３】

【００６６】
なお、上述の（２）式において、シンボルレートｆ_ｓｙｍは、図３に示される値を用いる。
【００６７】
また、ｆ−ＳＮＲとは、ｆｏｌｄｅｄ ＳＮＲ（折返しＳＮＲ）のことであり、以下の（４）式に示される。
【００６８】
【数４】

【００６９】
ただし、上述の（４）式において、Ｓ（ｆ）は送信信号強度で、単位はｍＷ／Ｈｚであり、後に述べるＰＳＤを用いる。このとき、ｄＢｍ／ＨｚからｍＷ／Ｈｚへ単位の変換を行なう必要がある。Ｎ（ｆ）は雑音強度で、単位はｍＷ／Ｈｚである。｜Ｈ（ｆ）｜^２は線路減衰の特性である。
【００７０】
（１−３）ベースバンド用ＤＥＦ
ＤＦＥが搭載されている場合のｘＤＳＬにおける伝送とは、具体的には、速度固定型の伝送方式である２Ｂ１Ｑ（Ｔｗｏ Ｂｉｎａｒｙ ｔｏ Ｏｎｅ Ｑｕａｔｅｒｎａｒｙ）方式やＰＡＭ（Ｐｕｌｓｅ Ａｍｐｌｉｔｕｄｅ Ｍｏｄｕｌａｔｉｏｎ）方式を採用するｘＤＳＬにおける伝送であって、ＨＤＳＬやＳＨＤＳＬなどが該当する。このときのＤＦＥは、ベースバンド用の伝送方法に使用するＡＮＳＩによるＤＦＥである。この場合の、求めるＳＮＲ（ｄＢ）は次の（５）式に示される。
【００７１】
【数５】

【００７２】
なお、上述の（５）式において、シンボルレートｆ_ｓｙｍは、図３に示される値を用いる。
【００７３】
また、ｆ−ＳＮＲとは、ｆｏｌｄｅｄ ＳＮＲのことであり、以下の（６）式に示される。
【００７４】
【数６】

【００７５】
ただし、上述の（６）式において、Ｓ（ｆ）は送信信号強度で、単位はｍＷ／Ｈｚであり、後に述べるＰＳＤを用いる。このとき、ｄＢｍ／ＨｚからｍＷ／Ｈｚへ単位の変換を行なう必要がある。Ｎ（ｆ）は雑音強度で、単位はｍＷ／Ｈｚである。｜Ｈ（ｆ）｜^２は線路減衰の特性である。
【００７６】
（１−４）パスバンド用ＤＦＥ
ＤＦＥが搭載されている場合のｘＤＳＬにおける伝送として、他のＤＦＥであるパスバンド用のＤＦＥが搭載されている場合のＳＮＲの計算方法についても説明する。
【００７７】
この場合には、ベースバンド用の伝送方法に使用するＡＮＳＩによるＤＦＥを搭載した場合に対して、中心の帯域がｆｃ（ｋＨｚ）に移動したものと考えるとよく、求めるＳＮＲ（ｄＢ）は次の（７）式に示される。
【００７８】
【数７】

【００７９】
なお、上述の（７）式において、シンボルレートｆ_ｓｙｍは、図３に示される値を用い、中心の帯域ｆｃは、欧州向けのｘＤＳＬの技術仕様であるＧ．９９１．１ ＡｎｎｅｘＢ（ＣＡＰ １−ｐａｉｒ）およびＧ．９９１．１ ＡｎｎｅｘＢ（ＣＡＰ ２−ｐａｉｒｓ）では、２２６ｋＨｚおよび１３８ｋＨｚとなる。
【００８０】
また、ｆ−ＳＮＲとは、ｆｏｌｄｅｄ ＳＮＲのことであり、以下の（８）式に示される。
【００８１】
【数８】

【００８２】
ただし、上述の（８）式において、Ｓ（ｆ）は送信信号強度で、単位はｍＷ／Ｈｚであり、後に述べるＰＳＤを用いる。このとき、ｄＢｍ／ＨｚからｍＷ／Ｈｚへ単位の変換を行なう必要がある。Ｎ（ｆ）は雑音強度で、単位はｍＷ／Ｈｚである。｜Ｈ（ｆ）｜^２は線路減衰の特性である。
【００８３】
（１−５）マルチキャリア方式
さらに、マルチキャリア方式でのｘＤＳＬ伝送方式であって、速度可変な伝送方式であるＡＤＳＬやＳＳＤＳＬの場合には、ｍ番目からｎ番目までの各サブキャリアに搭載できるビット数の総和ｂを求めた上で、伝送速度を導き出し、ＳＮＲを求める。なお、ｍ番目からｎ番目までの各サブキャリアに搭載できるビット数の総和ｂは、以下の（９）式に示される。
【００８４】
【数９】

【００８５】
ただし、上述の（９）式において、Ｓｉ（ｆ）はｉ番目のサブキャリアの送信信号強度で、Ｎｉ（ｆ）はｉ番目のサブキャリアの雑音強度で、｜Ｈｉ（ｆ）｜^２はｉ番目のサブキャリアの線路減衰の特性である。また、Γは実効ＳＮＲギャップで、次式を満たす。
【００８６】
Γ＝９．７５−Ｃ＋Ｍ
ただし、Ｃはコーディングゲイン、Ｍはノイズマージンであって、いずれも、各伝送方法を評価するために用いられる固有のパラメータである。
【００８７】
ＡＤＳＬなどバイト単位で伝送されるシステムでは、ビット数の総和ｂは、８の倍数となるよう切り捨てられる。
【００８８】
伝送速度を求めるためには、この値にシンボルレートを乗算すればよい。
（２）次に、本シミュレーションプログラムにおいて挿入されるノイズについて説明を行なう。
【００８９】
ノイズには様々な種類のものがあるが、本シミュレーションプログラムにおいては、漏話と白色雑音とを加法的ノイズとして挿入する。つまり、ノイズＮ（ｆ）は、以下の（１０）式に示される。
【００９０】
【数１０】

【００９１】
ただし、上述の（１０）式において、ＰＳＤ_ＮＥＸＴ（ｆ）およびＰＳＤ_ＦＥＸＴ（ｆ）は、近端漏話および遠端漏話の量を表わす。詳細は後述する。また、Ｗ（ｆ）は、白色雑音の大きさを表わす。通常、白色雑音として−１４０ｄＢｍ／Ｈｚを採用する。
【００９２】
さらに、近端漏話と遠端漏話とについて、図を挙げて説明を行なう。図４は、近端漏話と遠端漏話とを示す図である。
【００９３】
図４を参照して、漏話には、近端漏話および遠端漏話と呼ばれる２種類の漏話がある。通常、遠端漏話よりも近端漏話の方がはるかに大きい。
【００９４】
なお、近端漏話が発生しない場合の例として、時間的に上り信号と下り信号とを分離することにより他の伝送方式と同期をとる場合が挙げられる。具体的には、ＩＳＤＮ（Ｊａｐａｎ）と、日本向けのｘＤＳＬの技術仕様であるＧ．９９２．１／ Ｇ．９９２．２（ＡＤＳＬ）ＡｎｎｅｘＣ−ＦＢＭとＧ．９９２．１ ＡｎｎｅｘＨとは、互いに４００Ｈｚで同期がとられているので、これらの伝送方式による漏話の影響を算出する際には、近端漏話が発生しないものとして近端漏話を計算しない。
【００９５】
なお、漏話の強度は、漏話源の送信信号の強度、同一ケーブル内に存在する漏話源の回線数、および伝送線路の材質に依存し、伝送方式には依存しない。
【００９６】
次に、近端漏話と遠端漏話との各々について説明を行なう。
（２−１）近端漏話
近端漏話のＰＳＤ（強度）（ｍＷ／Ｈｚ）は、以下の（１１）式に示される。
【００９７】
【数１１】

【００９８】
ただし、上述の（１１）式において、ＰＳＤ_{ｄｉｓｔｕｒｂｅｒ}は、漏話源からの送信信号強度（ｍＷ／Ｈｚ）で、後に述べるＰＳＤを用いる。このとき、ｄＢｍ／ＨｚからｍＷ／Ｈｚへ単位の変換を行なう必要がある。
【００９９】
また、ＮＰＳＬは１６０ｋＨｚでの近端漏話減衰量を示す定数であって、ＩＴＵ−ＴＳ（国際電気通信連合）によって定められた所定の値を用いる。
【０１００】
（２−２）遠端漏話
遠端漏話のＰＳＤ（強度）（ｍＷ／Ｈｚ）は、以下の（１２）式に示される。
【０１０１】
【数１２】

【０１０２】
ただし、上述の（１２）式において、ＦＰＳＬは１６０ｋＨｚでの近端漏話減衰量を示す定数であって、ＩＴＵ−ＴＳによって定められた所定の値を用いる。
【０１０３】
（３）次に、線路減衰について説明を行なう。
線路減衰は、減衰定数と伝送線路長とに依存する。
【０１０４】
伝送経路の減数定数をＫ_ＬＯＯＰ（ｄＢ／ｋｍ）、線路長をｄ（ｋｍ）とすると、下線路減衰特性｜Ｈ（ｆ）｜^２は、以下の（１３）式に示される。
【０１０５】
【数１３】

【０１０６】
なお、図５に代表的な材質および直径の伝送線における伝送線路減衰定数のグラフを示す。図５は、４種類の材質および直径の伝送線における伝送線減衰定数を示す図である。
【０１０７】
（４）本シミュレーションプログラムでは、このようにして得られた送信側（自回線側）のＰＳＤと漏話側（漏話回線側）のＰＳＤとからＳ／Ｎ比を求め、ｘＤＳＬおよびＩＳＤＮの伝送特性の評価を行なう。以下に、自回線側の伝送方式がＩＳＤＮおよび具体的なｘＤＳＬである場合の、自回線側の伝送特性の評価を行なうための計算方法について示す。
【０１０８】
（４−１）ＩＳＤＮの伝送特性の評価
ＩＳＤＮの伝送特性の評価は、上述の（１−１）で説明されるリニアイコライザが搭載されている場合のＩＳＤＮにおける伝送でのＳＮＲを用いて行なう。このときのノイズとしては、上述の（２−１）で説明された近端漏話と、（２−２）で説明された遠端漏話と、通常の白色雑音である−１４０ｄＢｍ／Ｈｚの白色雑音との総和を用いる。そして、計算されたＳＮＲをしきい値である２６．４６（ｄＢ）と比較し、計算されたＳＮＲがしきい値以上である場合に、ＩＳＤＮ方式での伝送が可能であるとの評価を行なう。
【０１０９】
（４−２）ＡＤＳＬ（Ｇ．９９２．１／Ｇ．９９２．２ ＡｎｎｅｘＡ）の伝送特性の評価
ＡＤＳＬのうちのＧ．９９２．１／Ｇ．９９２．２ ＡｎｎｅｘＡの伝送特性の評価は、上述の（１−５）で説明されるマルチキャリア方式で伝送を行なうｘＤＳＬにおける伝送でのＳＮＲを用いて行なう。このときのノイズとしては、上述の（２−１）で説明された近端漏話と、（２−２）で説明された遠端漏話と、通常の白色雑音である−１４０ｄＢｍ／Ｈｚの白色雑音との総和を用いる。なお、その他のパラメータとしては、図６に示すパラメータを用いるものとする。
【０１１０】
（４−３）ＡＤＳＬ（Ｇ．９９２．１／Ｇ．９９２．２ ＡｎｎｅｘＣ）の伝送特性の評価
ＡＤＳＬのうちのＧ．９９２．１／Ｇ．９９２．２ ＡｎｎｅｘＣ−ＦＤＭの伝送特性の評価は、同様に、上述の（１−５）で説明されるＳＮＲを用いて行なう。このときのノイズとしては、上述の（２−１）で説明された近端漏話と、（２−２）で説明された遠端漏話と、通常の白色雑音である−１４０ｄＢｍ／Ｈｚの白色雑音との総和を用いる。ただし、漏話源がＩＳＤＮと同期して伝送するような方式である場合には、ＰＳＤ_ＮＥＸＴ（ｆ）として近端漏話と白色雑音との和を、ＰＳＤ_ＦＥＸＴ（ｆ）として遠端漏話と白色雑音との和を用いて、上述の（２−１）で説明された近端漏話と（２−２）で説明された遠端漏話とを漏話源として用いる。なお、その他のパラメータとしては、図６に示すパラメータと同様のパラメータを用いるものとする。
【０１１１】
（４−４）ＳＳＤＳＬ（Ｇ．９９２．１ ＡｎｎｅｘＨ）の伝送特性の評価
ＡＤＳＬ規格の１つであるＧ．９９２．１（Ｇ．ｄｍｔ）の付帯規格で、同規格をベースにした伝送方法であるＳＳＤＳＬ（Ｇ．９９２．１ ＡｎｎｅｘＨ）の伝送特性の評価は、同様に、上述の（１−５）で説明されるＳＮＲを用いて行なう。このときのノイズとしては、上述の（２−１）で説明された近端漏話と、（２−２）で説明された遠端漏話と、通常の白色雑音である−１４０ｄＢｍ／Ｈｚの白色雑音との総和を用いる。ただし、漏話源がＩＳＤＮと同期して伝送するような方式である場合には、ノイズとして遠端漏話と白色雑音との和を用いて、上述の（２−１）で説明された近端漏話と（２−２）で説明された遠端漏話とを漏話源として用いる。なお、その他のパラメータとしては、図７に示すパラメータを用いるものとする。
【０１１２】
（４−５）ＳＨＤＳＬの伝送特性の評価
上下対称型ｘＤＳＬの技術仕様であるＳＨＤＳＬの伝送特性の評価は、上述の（１−３）で説明されるＤＦＥが搭載されている場合のｘＤＳＬにおける伝送でのＳＮＲを用いて行なう。このときのノイズとしては、上述の（２−１）で説明された近端漏話と、（２−２）で説明された遠端漏話と、通常の白色雑音である−１４０ｄＢｍ／Ｈｚの白色雑音との総和を用いる。そして、計算されたＳＮＲをしきい値である２９．７（ｄＢ）と比較し、計算されたＳＮＲがしきい値以上である場合に、ＳＨＤＳＬ方式での伝送が可能であるとの評価を行なう。
【０１１３】
（４−６）２Ｂ１Ｑ方式を採用するＳＤＳＬの伝送特性の評価
２Ｂ１Ｑ方式を採用するＳＤＳＬの伝送特性の評価は、同様に、上述の（１−３）で説明されるＳＮＲを用いて行なう。このときのノイズとしては、上述の（２−１）で説明された近端漏話と、（２−２）で説明された遠端漏話と、通常の白色雑音である−１４０ｄＢｍ／Ｈｚの白色雑音との総和を用いる。そして、計算されたＳＮＲをしきい値である２７．４（ｄＢ）と比較し、計算されたＳＮＲがしきい値以上である場合に、ＳＤＳＬ方式での伝送が可能であるとの評価を行なう。
【０１１４】
（５）次に、漏話側として各伝送方式を想定した場合の、漏話側の伝送信号ＰＳＤについて、説明を行なう。なお、各伝送方式の特性は図８に示される。
【０１１５】
（５−１）漏話源の伝送方式がＴＣＭ−ＡＭＩ ＩＳＤＮ（Ｊａｐａｎ）である場合
ＴＣＭ−ＡＭＩ ＩＳＤＮ（Ｊａｐａｎ）の伝送方式自身がＩＳＤＮの漏話源となる場合の、漏話側の伝送信号ＰＳＤは、以下の（１４）式に示される。なお、この場合の装置インピーダンスは１１０（Ω）である。
【０１１６】
【数１４】

【０１１７】
ただし、上述の（１４）式において、ｆは周波数を示し、ｆ_０＝３２０×１０^３（Ｈｚ）、ｆ_３ｄＢ＝２×ｆ_０とする。また、Ｋ_ＤＳＬは係数で、Ｋ_ＤＳＬ＝Ｖ_ＯＰ ^２／４Ｒ（Ｗ）とする。また、装置インピーダンスが１１０（Ω）のときに、Ｖ_ＯＰはＶ_ＯＰ＝６．００（Ｖ）であるものとする。
【０１１８】
（５−２）漏話源の伝送方式が２Ｂ１Ｑ ＩＳＤＮ（ＵＳＡ）である場合
２Ｂ１Ｑ ＩＳＤＮ（ＵＳＡ）の伝送方式が漏話源となる場合の、漏話側の伝送信号ＰＳＤは、以下の（１５）式に示される。なお、この場合の装置インピーダンスは１３５（Ω）である。
【０１１９】
【数１５】

【０１２０】
さらに、上述のＴＣＭ−ＡＭＩ ＩＳＤＮ（Ｊａｐａｎ）が漏話源となる場合の漏話側の伝送信号ＰＳＤと、２Ｂ１Ｑ ＩＳＤＮ（ＵＳＡ）が漏話源となる場合の漏話側の伝送信号ＰＳＤとについて、図９に示す。
【０１２１】
（５−３）漏話源の伝送方式がＧ．９９２．１／Ｇ．９９２．２（ＡＤＳＬ Ｇ．ｄｍｔ／Ｇ．ｌｉｔｅ）ＡｎｎｅｘＡ／ＡｎｎｅｘＣ−ＤＢＭの下り方向である場合
Ｇ．９９２．１／ Ｇ．９９２．２（ＡＤＳＬ Ｇ．ｄｍｔ／Ｇ．ｌｉｔｅ）ＡｎｎｅｘＡ／ＡｎｎｅｘＣ−ＤＢＭの下り方向の伝送方式が漏話源となる場合の漏話側の伝送信号ＰＳＤは、以下の（１６）式に示される。
【０１２２】
【数１６】

【０１２３】
（５−４）漏話源の伝送方式がＧ．９９２．１／ Ｇ．９９２．２（ＡＤＳＬ Ｇ．ｄｍｔ／Ｇ．ｌｉｔｅ）ＡｎｎｅｘＡ／ＡｎｎｅｘＣ−ＤＢＭの上り方向である場合
Ｇ．９９２．１／ Ｇ．９９２．２（ＡＤＳＬ Ｇ．ｄｍｔ／Ｇ．ｌｉｔｅ）ＡｎｎｅｘＡ／ＡｎｎｅｘＣ−ＤＢＭの上り方向の伝送方式が漏話源となる場合の漏話側の伝送信号ＰＳＤは、以下の（１７）式に示される。
【０１２４】
【数１７】

【０１２５】
さらに、上述のＧ．９９２．１／ Ｇ．９９２．２（ＡＤＳＬ Ｇ．ｄｍｔ／Ｇ．ｌｉｔｅ）ＡｎｎｅｘＡ／ＡｎｎｅｘＣ−ＤＢＭの下り方向が漏話源となる場合の漏話側の伝送信号ＰＳＤと、上り方向が漏話源となる場合の漏話側の伝送信号ＰＳＤとについて、図１０および図１１に示す。図１０は、Ｇ．９９２．１ （ＡＤＳＬ Ｇ．ｄｍｔ）ＡｎｎｅｘＡ／ＡｎｎｅｘＣ−ＤＢＭの下り方向が漏話源となる場合の漏話側の伝送信号ＰＳＤと、上り方向が漏話源となる場合の漏話側の伝送信号ＰＳＤとを示す図であり、図１１は、Ｇ．９９２．２ （ＡＤＳＬ Ｇ．ｌｉｔｅ）ＡｎｎｅｘＡ／ＡｎｎｅｘＣ−ＤＢＭの下り方向が漏話源となる場合の漏話側の伝送信号ＰＳＤと、上り方向が漏話源となる場合の漏話側の伝送信号ＰＳＤとを示す図である。
【０１２６】
（５−５）漏話源の伝送方式がＧ．９９１．１（ＨＤＳＬ） ＡｎｎｅｘＡ（２Ｂ１Ｑ） である場合
Ｇ．９９１．１（ＨＤＳＬ） ＡｎｎｅｘＡ（２Ｂ１Ｑ）の伝送方式が漏話源となる場合の漏話側の伝送信号ＰＳＤは、以下の（１８）式に示される。なお、この場合の装置インピーダンスは１３５（Ω）である。
【０１２７】
【数１８】

【０１２８】
（５−６）ＳＤＳＬ（２Ｂ１Ｑ）
ＡＮＳＩに規定される、ＳＤＳＬ（２Ｂ１Ｑ）の伝送方式が漏話源となる場合の漏話側の伝送信号ＰＳＤは、以下の（１９）式に示される。なお、この場合の装置インピーダンスは１３５（Ω）である。
【０１２９】
【数１９】

【０１３０】
ただし、上述の（１９）式において、シンボルレートｆ_ｓｙｍは、図３に示される値を用いる。
【０１３１】
さらに、上述のＧ．９９１．１（ＨＤＳＬ） ＡｎｎｅｘＡ（２Ｂ１Ｑ）が漏話源となる場合の漏話側の伝送信号ＰＳＤと、ＳＤＳＬ（２Ｂ１Ｑ）が漏話源となる場合の漏話側の伝送信号ＰＳＤとについて、図１２に示す。図１２は、Ｇ．９９１．１（ＨＤＳＬ） ＡｎｎｅｘＡ（２Ｂ１Ｑ）が漏話源となる場合と、ＳＤＳＬ（２Ｂ１Ｑ）が漏話源となる場合とにおいて、ＳＤＳＬ（２Ｂ１Ｑ）におけるデータ伝送速度が７８４（ｋｂｐｓ）、１５５２（ｋｂｐｓ）、および２３２０（ｋｂｐｓ）である場合の漏話側の伝送信号ＰＳＤを示す図である。
【０１３２】
（５−７）漏話源の伝送方式がＧ．９９１．１（ＨＤＳＬ）ＡｎｎｅｘＢ（ＣＡＰ １−ｐａｉｒ／２−ｐａｉｒｓ） である場合
Ｇ．９９１．１（ＨＤＳＬ）ＡｎｎｅｘＢ（ＣＡＰ １−ｐａｉｒ／２−ｐａｉｒｓ） が漏話源となる場合は、図１３および図１４に示されるＰＳＤ平均電力のグラフおよび表を参照して送信電力を求めることで漏話側の伝送信号ＰＳＤを得る。図１３は、ＨＤＳＬ（ＣＡＰ）が漏話源となる場合の漏話側の送信信号ＰＳＤ平均電力のグラフを示し、図１４は表を示す。なお、この場合の装置インピーダンスは１３５（Ω）である。
【０１３３】
（５−８）漏話源の伝送方式がＧ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ａｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの下り方向である場合
Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ａｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの下り方向が漏話源となる場合は、ＰＳＤマスクのグラフと表とを参照して送信電力を求めることで漏話側の伝送信号ＰＳＤを得る。
【０１３４】
図１５および図１６は、Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ａｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの下り方向が漏話源となる場合の、ＰＳＤマスクのグラフおよび表を示す図である。なお、図１５は、Ｐｏｗｅｒ Ｂａｃｋｏｆｆが０（ｄＢ）のときのＰＳＤマスクのグラフを示す図であり、図１６に示される各周波数でのＰＳＤマスクの表に示されるＰＳＤマスク値を直線で結んだものである。なお、この場合の装置インピーダンスは１３５（Ω）である。
【０１３５】
（５−９）漏話源の伝送方式がＧ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ａｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの上り方向である場合
Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ａｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの上り方向が漏話源となる場合は、上述の、Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ａｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの下り方向が漏話源となる場合と同様に、ＰＳＤマスクのグラフと表とを参照して送信電力を求めることで漏話側の伝送信号ＰＳＤを得る。
【０１３６】
図１７および図１８は、Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ａｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの上り方向が漏話源となる場合の、ＰＳＤマスクのグラフおよび表を示す図である。なお、図１７は、Ｐｏｗｅｒ Ｂａｃｋｏｆｆが０（ｄＢ）のときのＰＳＤマスクのグラフを示す図であり、図１８に示される各周波数でのＰＳＤマスクの表に示されるＰＳＤマスク値を直線で結んだものである。なお、この場合の装置インピーダンスは１３５（Ω）である。
【０１３７】
（５−１０）漏話源の伝送方式がＧ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ｓｙｍｍｔｒｉｃ ＰＳＤである場合
Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ｓｙｍｍｔｒｉｃ ＰＳＤの伝送方式が漏話源となる場合の漏話側の伝送信号ＰＳＤは、以下の（２０）式に示される。
【０１３８】
【数２０】

【０１３９】
また、上述の（２０）式において用いられているＳＨＤＳＬ（対称ＰＳＤ）のパラメータを図１９に示す。図１９は、Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ｓｙｍｍｔｒｉｃ ＰＳＤが漏話源となる場合の漏話側の伝送信号ＰＳＤに用いられるパラメータを示す図である。なお、この場合の装置インピーダンスは１３５（Ω）である。
【０１４０】
さらに、ＳＨＤＳＬ（対称ＰＳＤ）の伝送方式における伝送信号ＰＳＤについて、図２０に示す。図２０は、ＳＨＤＳＬ（対称ＰＳＤ）の伝送方式が漏話源となる場合において、データ伝送速度が１５３６（ｋｂｐｓ）、７６８（ｋｂｐｓ）、および３８４（ｋｂｐｓ）のときの漏話側の伝送信号ＰＳＤを示す図である。
【０１４１】
（５−１１）漏話源の伝送方式がＧ．９９２．１ ＡｎｎｅｘＨ（ＳＳＤＳＬ）である場合
Ｇ．９９２．１ ＡｎｎｅｘＨ（ＳＳＤＳＬ）の伝送方式が漏話源となる場合の漏話側の伝送信号ＰＳＤは、上り方向および下り方向とも、Ｇ．９９２．１（ＡＤＳＬ Ｇ．ｄｍｔ） の伝送方式が漏話源となる場合の漏話側の伝送信号ＰＳＤと同じであるため、ここでの説明は繰返さない。
【０１４２】
（６）次に、本実施の形態のシミュレーションプログラムについて説明を行なう。
【０１４３】
本シミュレーションプログラムは、計算装置に上述の計算を行なわせることで、他の伝送方式の影響下でのＩＳＤＮの伝送特性、他の伝送方式の影響下でのＧ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの伝送特性、および他の伝送方式の影響下でのＧ．９９１．１（ＨＤＳＬ）ＡｎｎｅｘＡ（２Ｑ１Ｂ）などのｘＤＳＬの伝送特性について、線路長と受信信号のＳＮＲとの関係を自動的に出力させることで評価を行なう。
【０１４４】
このような本シミュレーションプログラムは、基本となる計算ソフトウェアとして、Ｅｘｃｅｌ（Ｒ）等の表計算ソフトウェアを用いて構成することができる。また、本シミュレーションプログラムで実行されるの計算プログラムは、ブロック単位でモジュール化されており、必要に応じて組合せて用いられる。
【０１４５】
なお、以下に、本シミュレーションプログラムを表計算ソフトウェアを用いて構成した際の、具体的なワークシートについて説明を行なう。
【０１４６】
図２１は、ＩＳＤＮの伝送特性を評価するためのシミュレーションプログラムのワークシートの一部の具体例を示す図である。図２１に示されるワークシートは、メイン画面を示す図である。
【０１４７】
図２１に示されるメイン画面において、実際にシミュレーション計算を行なう。具体的には、すべてのパラメータをワークシートの所定の欄に入力し、「計算実行」のボタンを押下すると計算が開始する。ＩＳＤＮの伝送特性を評価する場合には、上述の（５−１）で述べたように、計算されたＩＳＤＮの伝送特性のＳＮＲをしきい値と比較することで、ＩＳＤＮ方式での伝送の可否を評価する。そのため、図２１に示されるメイン画面においては、各路線長におけるＩＳＤＮの伝送特性のＳＮＲを表示している。さらに、所定のしきい値と比較することで、各路線長において、ＩＳＤＮ方式での伝送の可否を表示してもよい。
【０１４８】
図２１に示すようなシミュレーションプログラムにおいて用いる伝送線路の減衰特性を、一覧表として図２２に示す。
【０１４９】
図２２においては、１（ｋＨｚ）ごとの減衰定数が表１に示され、０．４ｍｍの紙絶縁テーブルの値が示されている。また、４．３１２５（ｋＨｚ）ごとの減衰定数が表２に示され、０．４ｍｍの紙絶縁テーブルを含む９種類のケーブルの値が示されている。
【０１５０】
本シミュレーションプログラムがＥｘｃｅｌ（Ｒ）等の表計算ソフトウェアを用いて構成されているため、図２２に示されるような伝送線路の減衰特性の一覧表をシミュレーションプログラムにワークシートとして含ませることで、シミュレーションプログラムを実行させる際に、当該一覧表を読出しながら実行させることができる。
【０１５１】
また、本シミュレーションプログラムがＥｘｃｅｌ（Ｒ）等の表計算ソフトウェアを用いて構成されているため、任意の計算過程での値を表示させることができる。具体的に、図２３に、本シミュレーションプログラムの実行途中で算出されるすべての伝送方式の送信信号ＰＳＤと近端漏話によるＰＳＤとを出力させるためのワークシートの具体例を示す。
【０１５２】
このように、表計算ソフトウェアを用いて構成されている本シミュレーションにおいては、計算に使用するＰＳＤ値等が正しいか否かを確認するために、任意の計算過程において、図２３に示されるような画面を出力することが可能である。また、図２３に示される表に計算されている伝送方式のうち、漏話源のＮＥＸＴと漏話される伝送方式のＰＳＤとをグラフ化することにより、各伝送方法の漏話の程度を比較することができる。それによって、相対的な漏話のおおよその影響具合を推定することができる。
【０１５３】
このような本シミュレーションプログラムを用いてシミュレーション計算を行なう場合には、図２１に示されるメイン画面のうち、二重線で囲われているセルに、評価する伝送方式についてのパラメータを入力する。また、漏話側のパラメータも入力する。そして、全てのパラメータを入力した後に、「計算実行」のボタンをクリックすると、計算が実行される。
【０１５４】
なお、ここで、評価する伝送方式についてのパラメータとして複数の種類から任意のパラメータを入力することが可能である。その場合、各伝送方法について性能計算を行ない、さらに、それらの比較を行なうこともできる。このことは、図２１に示されるメイン画面において、性能を評価する伝送方式についてのパラメータの入力を、複数種類の伝送方式について受付け、所定の計算式を各伝送方式について実行させることで実現される。
【０１５５】
計算は、図２１には示されない他のデータシートに含まれる上述の計算式を実行させることで実現される。また、さらに他のデータシートに、漏話源の候補である複数の伝送方式についての特性値が記録され、入力された漏話側のパラメータに応じて、対応する伝送方式の特性値を読出して計算を行なう。
【０１５６】
計算が終了すると、伝送線路の距離と受信信号のＳＮＲとの関係を示す表が、図２１に示される画面（「計算実行」ボタンの下）に出力される。また、計算結果が表示される（表の右側）。
【０１５７】
また、図２４および図２５は、ＡＤＳＬの伝送特性を評価するためのシミュレーションプログラムのワークシートの一部の具体例を示す図である。図２４に示されるワークシートは、メイン画面を示す図であって、漏話源や背景雑音等の環境条件に関するパラメータを入力するワークシートである。図２５に示されるワークシートは、ＡＤＳＬ伝送を行なう機器の条件に関するパラメータを入力するワークシートである。そして、全てのパラメータを入力した後に、図２４のメイン画面上の「計算実行」のボタンをクリックすると、計算が実行される。なお、ここでの計算の詳細については、上述のＩＳＤＮの伝送特性を評価するためのワークシートと同様であるため、ここでの説明は繰返さない。
【０１５８】
さらに、本シミュレーションプログラムで用いる各モジュールにおいて実行されている計算について具体的に説明を行なう。本シミュレーションプログラムの各モジュールで用いる計算プログラムは、Ｖｉｓｕａｌ Ｂａｓｉｃ（Ｒ）等のマクロ言語で構成されている。以下には、その具体例として、Ｖｉｓｕａｌ Ｂａｓｉｃ（Ｒ）形式のコードから構成されているモジュールについて説明を行なう。
【０１５９】
Ｖｉｓｕａｌ Ｂａｓｉｃ（Ｒ）では、ユーザ定義のプログラムを用いることにより、プログラムコードのモジュール化が可能である。
【０１６０】
モジュールは、図２に示される各ブロックごと、つまり、送信信号の送信スペクトル計算モジュール、線路減衰特性モジュール、漏話信号の送信スペクトル（近端側、遠端側）計算モジュール、近端漏話特性計算モジュール、遠端漏話特性計算モジュール、Ｓ／Ｎ比計算モジュール、および伝送速度計算モジュール（マルチキャリア方式のみ）からなる。また、常用対数やｓｉｎｃ関数計算モジュールなど、上記計算を補完するモジュールもある。
【０１６１】
本シミュレーションプログラムがこのようなモジュールで構成されていることで、新方式の送信スペクトルや新規イコライザの登場など、プログラムの追加や修正が必要になったとき、該当するモジュールを書換えればよいため、保守や拡張が容易であるという利点がある。
【０１６２】
（７）次に、本シミュレーションプログラムに対する合わせ込みについて説明する。
【０１６３】
本シミュレーションプログラムは、上述のようにＶｉｓｕａｌ Ｂａｓｉｃ（Ｒ）等のマクロ言語で構成された、Ｅｘｃｅｌ（Ｒ）等の表計算ソフトウェアを用いて構成されているため、所定のモジュールや、所定のパラメータを書換えることによって、計算値を実測値により近づけるように合わせ込むことができる。
【０１６４】
このような本シミュレーションプログラムを用いることで、実測による実験と比較して、大幅に手間やコストを削減できる。そのため、ＩＳＤＮやｘＤＳＬの性能を効率的に計算することができる。また、効率的に短時間で様々な漏話条件を想定した結果を得たいときに有効である。
【０１６５】
さらに、本シミュレーションプログラムでは、各種パラメータの計算をモジュール化しているため、容易に他のツールに本シミュレーションプログラムの情報を移植することが可能である。すなわち、通常使用するパラメータをプログラムの中身を変更せずに自由に設定することができ、操作性に優れている。また、既存のシミュレーションプログラムにも対応することができ、互換性にも優れている。
【０１６６】
また、上述の如く、本実施の形態におけるシミュレーションプログラムが、複数のモジュールを組合せた構成であるため、ＩＳＤＮおよび主なｘＤＳＬの全種類、すなわち、主な加入回線の全ての環境下でのＩＳＤＮおよびｘＤＳＬの性能について計算することができる。すなわち、本実施の形態におけるシミュレーションプログラムの、設定値を変更するのみで、ＩＳＤＮおよび主なｘＤＳＬの全種類の性能結果を得ることができる。
【０１６７】
また、本実施の形態におけるシミュレーションプログラムを用いて、ＩＳＤＮおよび異なる種類のｘＤＳＬの性能を、同一の条件下で算出することにより、当該条件でのＩＳＤＮおよびｘＤＳＬの性能を比較することができる。
【０１６８】
さらに、本実施の形態におけるシミュレーションプログラムを用いることで、ＩＳＤＮとｘＤＳＬ間、ｘＤＳＬ間の干渉を計算することができる。そのため、算出された干渉と、判定基準とを比較することによって、スペクトル適合性の大小を、自動判定することができる。
【０１６９】
このように本シミュレーションプログラムにおいては、様々な条件下でのＩＳＤＮやｘＤＳＬの性能をシミュレーションして評価を行なうことができる。また、シミュレーションした値に基づいて上述のフィッティング処理を行なって合わせ込みを実行させることで、実測に近いシミュレーションを得ることができる。さらに、図２６に示されるように、実測を行なうことなく、ＩＳＤＮやｘＤＳＬの性能を予測して評価することができる。以下に、上述のフィッティング処理の具体例として、ＡＤＳＬである、Ｇ９９２．２ ＡｎｎｅｘＣ下りの速度性能の推定を行なう場合について説明を行なう。ここでは、具体的に、実測値と理論値とのそれぞれのビットマップを取得して比較する例について述べる。
【０１７０】
ビットマップとは、ＡＤＳＬのようなマルチキャリア伝送方式の場合、複数のサブキャリアが独立なビット数を搭載できることを特徴とする。例えば、Ｇ９９２．２方式のＡＤＳＬの場合には、トーンナンバーＮｏ．３３〜Ｎｏ．１２７までの９５個のサブキャリアが独立なビット数を搭載できる。この場合、各トーンが各々掲載しているビット数を示すグラフや表をビットマップという。ビットマップの取得の仕方については、一般的な方法を用いることができるため、ここでの説明は行なわない。
【０１７１】
このようなビットマップを用いた比較は、ＡＤＳＬにおける実測値と計算値との比較において効果的な方法であるが、比較方法は、ビットマップでの比較に限定されず、その他の方法を用いた比較であっても構わない。なお、その場合には、以下に述べるフィッティングパラメータは比較方法に応じたものを用いることが好ましい。
【０１７２】
このような、ＡＤＳＬの速度性能の推定を行なう場合のフィッティング処理の具体例について、図２７にフローチャートを示す。なお、以下の処理例においては、具体的に、実測できる条件が、背景雑音（ホワイトノイズ）環境下とＡＤＳＬ漏話環境下との２通りあるものとする。また、ＡＤＳＬ機器がビットマップを表示する機能を備えるものとする。
【０１７３】
図２７を参照して、始めに、ステップＳ１０１において、背景雑音環境下におけるＡＤＳＬ伝送方式でのビットマップの理論値と実測値とを求める。ここでの求め方については、本発明において限定されるものでなく、一般的な方法を用いて構わない。なお、ここでのシミュレーションに用いたパラメータは、図６のＧ９９２．２に示されているパラメータである。
【０１７４】
次に、求めたビットマップの理論値と実測値とについて、有意な乖離が見られる場合（Ｓ１０３でＹＥＳ）、ステップＳ１０５において、それらのビットマップを合致させるように、背景雑音強度、最大トーンナンバー、あるいは最小トーンナンバーを合わせ込む。
【０１７５】
なお、ステップＳ１０５における合わせ込み処理については、後述する。
次に、ステップＳ１０７において、ＡＤＳＬ漏話環境下におけるＡＤＳＬ伝送方式でのビットマップの理論値と実測値とを求める。このとき、上述のステップＳ１０５で合わせ込みを実行した場合には、合わせ込まれた背景雑音強度等を用いてＡＤＳＬ漏話環境下におけるＡＤＳＬ伝送方式でのビットマップの理論値を求める。
【０１７６】
次に、求めたビットマップの理論値と実測値とについて、有意な乖離が見られる場合（Ｓ１０９でＹＥＳ）、ステップＳ１１１において、それらのビットマップを合致させるように、漏話減衰量、あるいはノイズマージンを合わせ込む。
【０１７７】
以上で、フィッティング処理を終了し、このようにして合わせ込まれた値を用いることで、実測できない条件での速度推定を行なうことができる。
【０１７８】
ＡＤＳＬ伝送方式での伝送速度は、ビット数の和にシンボルレートを掛け合わせて得られるため、ＡＤＳＬ伝送方式での伝送速度にはサブキャリアごとに搭載したビット数の和が直接関係する。そのため、実際の環境や機器特性に近づけ、実際の速度を推定する上で、ビットマップの合わせこみは重要であり、大きな助けとなる。
【０１７９】
なお、上述のフィッティング処理のステップＳ１０５およびステップＳ１１１における合わせ込み処理について具体例を挙げながら説明する。
【０１８０】
背景雑音環境下の理論計算でのビットマップと実測でのビットマップとが具体的に図２８のようであった場合、ステップＳ１０３においては、理論計算と実測とでは有意な乖離が見られると判断する。ここでの判断方法については本発明において限定されるものではないが、具体的には、理論計算でのビットマップ上の所定のトーンナンバーにおいて、理論計算でのビットマップと実測でのビットマップとの搭載ビット数に、しきい値以上の差異が存在することを検出することで判断されても構わない。また、その他の方法で判断されても構わない。このように有意な乖離が見られると判断されると、上述のステップＳ１０５にてフィッティングパラメータを用いて、合わせ込みを実行する。
【０１８１】
（最大、最小トーンナンバーの合わせ込み）
図２８を参照して、理論計算でのビットマップと実測でのビットマップとにおいて、最大トーンナンバーおよび最小トーンナンバーが乖離しているので、ステップＳ１０５においては、これらを合わせ込み、使用する周波数帯域を調整する必要がある。具体的には、図２８を参照して、実測では、最小トーンナンバーは３６から開始し、４２まで徐々に搭載ビット数が上昇している。これは、イコライザ等の機器の特性に依存するもので、シミュレーションにおいて模擬することが困難である。そこで、理論計算での最大トーンナンバーおよび最小トーンナンバーを実測でのそれに合わせ込む際、理論計算での最小トーンナンバーを３６と４２との中間の値である３９とし、最大トーンナンバーを１１７と１２２との中間の値である１１９として、シミュレーションでの使用キャリアを変更する。そして、ＡＤＳＬ伝送速度を近似する。このようにすることで、シミュレーションにおいて搭載可能な全ビット数を、実質的に実測に合わせ込むことができる。このような最大、最小トーンナンバーの合わせ込みを行なった後の理論計算でのビットマップと実測でのビットマップとを、図２９に示す。
【０１８２】
（背景雑音強度の合わせ込み）
次に、図２９を参照して、理論計算でのビットマップと実測でのビットマップとを比較して、実測での搭載ビット数が、全体にわたって理論計算における搭載ビット数に対して１ビット低い。このことから、実測の背景雑音が理論計算で想定している背景雑音（−１４０ｄＢｍ／Ｈｚ）より高いと推定し、背景雑音強度の合わせ込みを行なう。背景雑音強度を合わせ込むことにより、漏話ノイズが背景雑音よりも小さいキャリアの搭載ビット数を、一様にフィッティングさせることができる。
【０１８３】
通常、１ビット余分に搭載するには、３ｄＢ分ＳＮＲが高くなることを要求される。このことに基づいて、図２９に示される本具体例においては、実測によるＳＮＲが理論計算によるＳＮＲよりも３ｄＢ分低いものと推定し、背景雑音を−１３７ｄＢｍ／Ｈｚとして再計算する。なお、ここでの推定は、上述のように予め所定の背景雑音を仮定して再計算を行なってもよいし、ある程度の範囲の背景雑音について順次再計算を行なって、その都度実測でのビットマップとフィットするか否かを判定し、最適な背景雑音を検出しても構わない。このような背景雑音強度の合わせ込みを行なった後の理論計算でのビットマップと実測でのビットマップとを、図３０に示す。
【０１８４】
このような合わせ込み処理が上述のステップＳ１０５で行なわれることによって、各サブキャリアの搭載ビット数の和（ビットマップの面積に相当する）は、理論計算と実測とでほぼ一致する。したがって、この合わせ込み処理を行なうことで、伝送速度もほぼ一致する。これで、背景雑音下での速度の合わせ込みが完了する。
【０１８５】
（漏話減衰量、ノイズマージンの合わせ込み）
次に、ＡＤＳＬ漏話環境下の理論計算でのビットマップと実測でのビットマップとが具体的に図３１のようであった場合、ステップＳ１０９においては、理論計算と実測とでは有意な乖離が見られると判断する。ここでの判断方法についても、上述のステップＳ１０３における判断方法と同様であるため、説明は繰返さない。このように有意な乖離が見られると判断されると、上述のステップＳ１１１にてフィッティングパラメータを用いて、合わせ込みを実行する。
【０１８６】
一般的に、漏話が存在する場合は、背景雑音が存在する場合に比べて伝送条件が悪いため、搭載ビット数が低い。また、高周波帯域（トーンナンバーの大なる帯域）ではさらに伝送条件が悪くなるため、最大トーンナンバーまでビットを搭載することができない場合もある。
【０１８７】
具体的には、図３１を参照して、理論計算でのビットマップと実測でのビットマップとを比較して、実測での搭載ビット数が、全体にわたって理論計算における搭載ビット数に対して１ビット低い。また、ＡＤＳＬ伝送方式に対するＡＤＳＬ伝送方式の漏話の干渉は、遠端漏話が支配的であることが知られている。これらのことから、遠端漏話の相対的な強さを調整するパラメータである遠端漏話減衰量の大きさを決定する、遠端漏話の強度に用するパラメータであるＦＰＳＬ（遠端漏話減衰特性）を３ｄＢ小さく（漏話を大きく）し、つまりＦＰＳＬ＝４２．０ｄＢとしてビットマップを再計算する。また、必要に応じてノイズマージンの値を変化させてもよい。ＡＤＳＬ伝送方式におけるノイズマージンは、通常は、上り方向、下り方向ともに４ｄＢであるが、このノイズマージンを調整することにより、全てのキャリアの搭載ビット数を一様にフィッティングさせることができる。
【０１８８】
このように、ＦＰＳＬおよびノイズマージの合わせ込みを行なった後の理論計算でのビットマップと実測でのビットマップとを、図３２に示す。
【０１８９】
このような合わせ込み処理が上述のステップＳ１１１で行なわれることによって、各サブキャリアの搭載ビット数の和（ビットマップの面積に相当する）は、理論計算と実測とでほぼ一致する。したがって、この合わせ込み処理を行なうことで、伝送速度もほぼ一致する。これで、背景雑音下での速度の合わせ込みが完了する。
【０１９０】
なお、ＡＤＳＬ伝送方式のうちのＡｎｎｅｘ Ｃ方式は、ＩＳＤＮ干渉下でも高い伝送速度を維持できるよう、ＮＥＸＴビットマップとＦＥＸＴビットマップという２種類のビットマップを用意している。その２種類のビットマップそれぞれを合わせ込むことにより、合わせ込み精度がより向上すると考えられる。
【０１９１】
なお、ステップＳ１０５およびＳ１１１におけるフィッティング処理の方法は、上述の方法に限定されず、さらに他の方法を用いてもかまわない。例えば、搭載可能なビット数を、実測のビットマップに合わせるためのパラメータであるビットやトーンを用いて合わせ込みを行なうこともできる。
【０１９２】
このように合わせ込んだパラメータを用いて、異なる漏話源下での伝送性能推定、異なるケーブル環境上での伝送性能推定、および異なる伝送システムの伝送性能推定を行なうことが可能である。
【０１９３】
そこで、以下に、ＩＳＤＮ漏話環境下でのＡＤＳＬ（Ｇ９９２．２）の０．４ｍｍ径ＣＣＰケーブル上の下り伝送性能を合わせ込んだ場合について、上述の３通りの推定の具体例について述べる。
【０１９４】
（異なる干渉源下での伝送性能推定）
たとえば、ＳＤＳＬ漏話環境下でのＡＤＳＬ（Ｇ９９２．２）の０．４ｍｍ径ＣＣＰケーブル上の下り伝送性能を推定することが可能である。この場合は、漏話源のスペクトルをＳＤＳＬのものに変更して計算すればよい。
【０１９５】
（異なるケーブル上での伝送性能推定）
ＩＳＤＮ干渉下でのＡＤＳＬ（Ｇ９９２．２）の０．５ｍｍ径ＣＣＰケーブル上の下り伝送性能を推定することが可能である。この場合は、ケーブルパラメータを０．５ｍｍ径ＣＣＰケーブルのものに変更して計算すればよい。
【０１９６】
（異なる伝送システムの伝送性能推定）
たとえば、ＩＳＤＮ漏話環境下でのＡＤＳＬ（Ｇ９９２．１）の０．４ｍｍ径ＣＣＰケーブル上の下り伝送性能を推定することが可能である。Ｇ９９２．１方式の場合、図６に示されるようにＧ９９２．２方式との違いはノイズマージンと最大トーンナンバーとである。ノイズマージンは、Ｇ９９２．１方式の方がＧ９９２．２方式よりも２ｄＢ高いので、Ｇ９９２．２方式を合わせ込んだ値に２ｄＢを加えた値を用いる。また、最大トーンナンバーは、Ｇ９９２．１方式の方がＧ９９２．２方式よりも１２８高いので、Ｇ９９２．２方式を合わせ込んだ値に１２８を加えた値を用いる。このようにすることで、Ｇ９９２．１方式下りの速度推定が可能である。
【０１９７】
さらに、ＩＳＤＮ（ベースバンド方式）の場合も、ＡＤＳＬ（マルチキャリア方式）と同様に、合わせ込んだパラメータを用いて、異なる漏話源下での伝送性能推定、異なるケーブル環境上での伝送性能推定、および異なる伝送システムの伝送性能推定を行なうことが可能である。
【０１９８】
そこで、以下に、ＡＤＳＬ漏話環境下でのＩＳＤＮの０．４ｍｍ径ＣＣＰケーブル上の下り伝送性能を合わせ込んだ場合について、上述の３通りの推定の具体例について述べる。
【０１９９】
（異なる干渉源下での伝送性能推定）
たとえば、ＳＤＳＬ漏話環境下でのＩＳＤＮの０．４ｍｍ径ＣＣＰケーブル上の下り伝送性能を推定することが可能である。この場合は、漏話源のスペクトルをＳＤＳＬのものに変更して計算すればよい。
【０２００】
（異なるケーブル上での伝送性能推定）
ＡＤＳＬ干渉下でのＩＳＤＮの０．５ｍｍ径ＣＣＰケーブル上の下り伝送性能を推定することが可能である。この場合は、ケーブルパラメータを０．５ｍｍ径ＣＣＰケーブルのものに変更して計算すればよい。
【０２０１】
（異なる伝送システムの伝送性能推定）
現在は、ＩＳＤＮと同様の伝送性能計算が可能なＤＳＬ方式は他に見当たらないが、将来新方式が開発された際に、これがＩＳＤＮと類似した伝送システムであった場合、その伝送システムの伝送性能推定を行なうことが可能である。たとえば、ＩＳＤＮの送信スペクトルが変更した場合、スペクトルを置換えて計算すれば伝送性能推定が可能である。
【０２０２】
さらに以下に、ＩＳＤＮの合わせ込みについて、より具体的に説明する。
ＩＳＤＮの速度性能の推定を行なう場合のフィッティング処理の具体例について、図３３にフローチャートを示す。なお、以下の処理例においては、具体的に、実測できる条件が、背景雑音環境下とＡＤＳＬ漏話環境下との２通りあるものとする。この２通りの条件で、ＩＳＤＮが伝送可能な最大距離を理論計算と実測とにより求める。すなわち、理論計算においては、ＳＮＲ＝２６．４６ｄＢ（しきい値）を確保できる最大距離を求め、実測では、実際にＩＤＳＮがつながる最大距離（ＩＳＤＮ到達可能距離）を計測する。
【０２０３】
図３３を参照して、始めに、ステップＳ２０１において、背景雑音環境下におけるＩＳＤＮ伝送方式での伝送可能な最大距離の理論値と実測値とを求める。
【０２０４】
次に、求めた伝送可能な最大距離の理論値と実測値とについて、有意な乖離が見られる場合（Ｓ２０３でＹＥＳ）、ステップＳ２０５において背景雑音強度を合わせ込む。なお、ステップＳ２０５における合わせ込み処理については、後述する。
【０２０５】
次に、ステップＳ２０７において、ＡＤＳＬ漏話環境下におけるＩＳＤＮ伝送方式での伝送可能な最大距離の理論値と実測値とを求める。このとき、上述のステップＳ２０５で合わせ込みを実行した場合には、合わせ込まれた背景雑音強度を用いてＡＤＳＬ漏話環境下におけるＩＳＤＮ伝送方式での伝送可能な最大距離の理論値を求める。
【０２０６】
次に、求めた伝送可能な最大距離の理論値と実測値とについて、有意な乖離が見られる場合（Ｓ２０９でＹＥＳ）、ステップＳ２１１において漏話減衰量を合わせ込む。
【０２０７】
以上で、フィッティング処理を終了し、このようにして合わせ込まれた値を用いることで、実測できない条件での速度推定を行なうことができる。
【０２０８】
なお、上述のフィッティング処理のステップＳ２０５およびステップＳ２１１における合わせ込み処理について具体例を挙げながら説明する。
【０２０９】
（背景雑音強度の合わせ込み）
背景雑音環境下の理論計算でのＩＳＤＮが伝送可能な最大距離の理論計算値が具体的に６．５ｋｍであり、実測値が５．５ｋｍであった場合、ステップＳ２０３においては、理論計算と実測とでは有意な乖離が見られると判断する。なお、ここでのシミュレーション計算に用いたパラメータは、
ＮＰＳＬ（近端漏話特性値）＝４７．０ｄＢ
ＦＰＳＬ（遠端漏話特性値）＝４５．０ｄＢ
背景雑音＝−１４０ｄＢｍ／Ｈｚ
である。ここでの有意な乖離であるか否かの判断方法については本発明において限定されるものではないが、具体的には、理論値と実測値との間に、しきい値以上の差異が存在することを検出することで判断されても構わない。また、その他の方法で判断されても構わない。このように有意な乖離が見られると判断されると、上述のステップＳ２０５にて背景雑音環境下での合わせ込みを実行する。
【０２１０】
上述の具体例の場合、実測でのＩＳＤＮの最大到達可能距離が理論値より小さいことから、実測の背景雑音が理論計算で想定している背景雑音（−１４０ｄＢｍ／Ｈｚ）より高いと推定し、背景雑音を想定している背景雑音より高く再設定して再計算する。
【０２１１】
ここでの背景雑音の再設定の仕方については、以下の方法が挙げられる。すなわち、実測での最大到達可能距離が５．５ｋｍであることから、５．５ｋｍ付近でのＳＮＲがしきい値（２６．４６ｄＢ）程度であると推定できる。一方、理論計算において５．５ｋｍ付近でのＳＮＲを算出すると４３ｄＢであった。このことから、実測の背景雑音は理論計算における背景雑音よりも１６．５ｄＢ程度高いものと推定し、理論計算における背景雑音強度を−１４０ｄＢｍ／Ｈｚから１６．５ｄＢ分程度高い−１２４ｄＢｍ／Ｈｚに再設定し、最大到達距離を再計算する。そして、再度、理論値と実測値との間に有意な乖離が見られるか否かの判断を行なう。この処理を繰返すことで、背景雑音の推定を行ない、理論計算における背景雑音を実測の背景雑音に合わせ込むことができる。
【０２１２】
（漏話減衰量の合わせ込み）
次に、上で再設定された背景雑音を用いて計算されたＡＤＳＬ漏話環境下の理論計算での伝送可能な最大距離と、実測での伝送可能な最大距離とを用いて、理論計算における漏話減衰量を合わせ込む。
【０２１３】
上の具体例において背景雑音は−１２４ｄＢｍ／Ｈｚに再設定されているので、その値を用いて、ＩＳＤＮの最大到達距離を再計算する。その結果、最大到達距離が３．２５ｋｍであり、実測値が３．７５ｋｍであった場合、ステップＳ２０９においては、理論計算と実測とでは有意な乖離が見られると判断する。
【０２１４】
上述の具体例の場合、実測でのＩＳＤＮの最大到達可能距離が理論値より大きいことから、実測での漏話特性が理論計算で想定している漏話特性より小さいと推定し、漏話特性（ＮＰＳＬ、ＦＰＳＬ）を変化させて再設定し、再計算する。
【０２１５】
ここでの漏話特性の再設定の仕方については、上述のステップＳ２０５における処理と同様の方法が挙げられる。すなわち、実測での最大到達可能距離が３．７５ｋｍであることから、３．７５ｋｍ付近でのＳＮＲがしきい値（２６．４６ｄＢ）程度であると推定できる。一方、理論計算において３．７５ｋｍ付近でのＳＮＲを算出すると２１．１ｄＢであった。このことから、実測の漏話減衰量は理論計算で想定している漏話減衰量よりも約５ｄＢ大きい（漏話が小さい）と推定する。ＩＳＤＮ伝送方式に対するＡＤＳＬ伝送方式の漏話の干渉は、近端漏話が支配的であることが知られている。そこで、理論計算における近端漏話減衰量を変化させ、すなわち、ＮＰＳＬを大きく再設定し、最大到達距離を再計算する。そして、再度、理論値と実測値との間に有意な乖離が見られるか否かの判断を行なう。この処理を繰返すことで、ＮＰＳＬの推定を行ない、理論計算における漏話減衰量を実測の漏話減衰量に合わせ込むことができる。なお、上の具体例においては、ＮＰＳＬを６ｄＢ大きい５３．０ｄＢと再設定した場合に、最大到達距離が３．７５ｋｍと再計算され、実測値と一致した。
【０２１６】
このような合わせ込み処理がステップＳ２０５、Ｓ２１１で行なわれることによって、背景雑音、および漏話減衰量（近端漏話特性、遠端漏話特性）は、理論計算と実測とでほぼ一致する。
【０２１７】
このように、本実施の形態におけるシミュレーションプログラムを用いることで、プログラム上の設定パラメータを実機器の特性に合わせた値に変更することのみで、実測では困難な条件での実機器の性能を高精度で推定することができる。
【０２１８】
また、本実施の形態におけるシミュレーションプログラムにおいて、従来の実機器の設定パラメータ値を用いて、開発途上あるいは開発予定の実機器の性能を推定することも可能である。
【０２１９】
さらに、上述のシミュレーションプログラムを、コンピュータに付属するフレキシブルディスク、ＣＤ−ＲＯＭ、ＲＯＭ、ＲＡＭおよびメモリカードなどのコンピュータ読取り可能な記録媒体にて記録させて、プログラム製品として提供することもできる。あるいは、コンピュータに内蔵するハードディスクなどの記録媒体にて記録させて、プログラムを提供することもできる。また、ネットワークを介したダウンロードによって、プログラムを提供することもできる。
【０２２０】
提供されるプログラム製品は、ハードディスクなどのプログラム格納部にインストールされて実行される。
【０２２１】
なお、プログラム製品は、プログラム自体と、プログラムが記録された記録媒体とを含む。
【０２２２】
今回開示された実施の形態はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は上記した説明ではなくて特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。
【図面の簡単な説明】
【図１】回線モデルの具体例を示す図である。
【図２】本シミュレーションプログラムにおけるシミュレーション方法の具体例を示す図である。
【図３】シンボルレートｆ_ｓｙｍを表示した図である。
【図４】近端漏話と遠端漏話とを示す図である。
【図５】４種類の材質および直径の伝送線における伝送線減衰定数を示す図である。
【図６】ＡＤＳＬの伝送特性の評価を行なう際のパラメータを表形式で示す図である。
【図７】ＳＳＤＳＬの伝送特性の評価を行なう際のパラメータを表形式で示す図である。
【図８】各伝送方式の特性を示す図である。
【図９】ＴＣＭ−ＡＭＩ ＩＳＤＮ（Ｊａｐａｎ）が漏話源となる場合の漏話側の伝送信号ＰＳＤと、２Ｂ１Ｑ ＩＳＤＮ（ＵＳＡ）が漏話源となる場合の漏話側の伝送信号ＰＳＤとについて示す図である。
【図１０】Ｇ．９９２．１ （ＡＤＳＬ Ｇ．ｄｍｔ）ＡｎｎｅｘＡ／ＡｎｎｅｘＣ−ＤＢＭの下り方向が漏話源となる場合の漏話側の伝送信号ＰＳＤと、上り方向が漏話源となる場合の漏話側の伝送信号ＰＳＤとを示す図である。
【図１１】Ｇ．９９２．２ （ＡＤＳＬ Ｇ．ｌｉｔｅ）ＡｎｎｅｘＡ／ＡｎｎｅｘＣ−ＤＢＭの下り方向が漏話源となる場合の漏話側の伝送信号ＰＳＤと、上り方向が漏話源となる場合の漏話側の伝送信号ＰＳＤとを示す図である。
【図１２】Ｇ．９９１．１（ＨＤＳＬ） ＡｎｎｅｘＡ（２Ｂ１Ｑ）が漏話源となる場合と、ＳＤＳＬ（２Ｂ１Ｑ）が漏話源となる場合とにおいて、ＳＤＳＬ（２Ｂ１Ｑ）におけるデータ伝送速度が７８４（ｋｂｐｓ）、１５５２（ｋｂｐｓ）、および２３２０（ｋｂｐｓ）である場合の漏話側の伝送信号ＰＳＤを示す図である。
【図１３】ＨＤＳＬ（ＣＡＰ）が漏話源となる場合の漏話側の送信信号ＰＳＤ平均電力をグラフ形式で示す図である。
【図１４】ＨＤＳＬ（ＣＡＰ）が漏話源となる場合の漏話側の送信信号ＰＳＤ平均電力を表形式で示す図である。
【図１５】Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ａｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの下り方向が漏話源となる場合の、ＰＳＤマスクをグラフ形式で示す図である。
【図１６】Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ａｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの下り方向が漏話源となる場合の、ＰＳＤマスクを表形式で示す図である。
【図１７】Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ａｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの上り方向が漏話源となる場合の、ＰＳＤマスクをグラフ形式で示す図である。
【図１８】Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ａｓｙｍｍｔｒｉｃ ＰＳＤ １．５Ｍｂｐｓの上り方向が漏話源となる場合の、ＰＳＤマスクを表形式で示す図である。
【図１９】Ｇ．９９１．２（ＳＨＤＳＬ，ＰＡＭ）ＡｎｎｅｘＡ Ｓｙｍｍｔｒｉｃ ＰＳＤの伝送方式が漏話源となる場合の漏話側の伝送信号ＰＳＤを計算する際のパラメータを示す図である。
【図２０】ＳＨＤＳＬ（対称ＰＳＤ）の伝送方式が漏話源となる場合において、データ伝送速度が１５３６（ｋｂｐｓ）、７６８（ｋｂｐｓ）、および３８４（ｋｂｐｓ）のときの漏話側の伝送信号ＰＳＤを示す図である。
【図２１】ＩＳＤＮの伝送特性を評価するためのシミュレーションプログラムのワークシートの一部の具体例を示す図である。
【図２２】シミュレーションプログラムにおいて用いる伝送線路の減衰特性を、一覧表形式で示す図である。
【図２３】本シミュレーションプログラムの実行途中で算出されるすべての伝送方式の送信信号ＰＳＤと近端漏話によるＰＳＤとを出力させるためのワークシートの具体例を示す図である。
【図２４】ＡＤＳＬの伝送特性を評価するためのシミュレーションプログラムのワークシートの一部の具体例を示す図である。
【図２５】ＡＤＳＬの伝送特性を評価するためのシミュレーションプログラムのワークシートの一部の具体例を示す図である。
【図２６】本シミュレーションプログラムが用いる、各伝送方式において使用されるキャリアを考慮した、性能値推定の手法を示す図である。
【図２７】ＡＤＳＬの速度性能の推定を行なう場合のフィッティング処理の具体例を示すフローチャートである。
【図２８】背景雑音環境下の理論計算でのビットマップと実測でのビットマップとの具体例を示す図である。
【図２９】最大、最小トーンナンバーの合わせ込みを行なった後の理論計算でのビットマップと実測でのビットマップとの具体例を示す図である。
【図３０】背景雑音強度の合わせ込みを行なった後の理論計算でのビットマップと実測でのビットマップとの具体例を示す図である。
【図３１】ＡＤＳＬ漏話環境下の理論計算でのビットマップと実測でのビットマップとの具体例を示す図である。
【図３２】ＦＰＳＬおよびノイズマージの合わせ込みを行なった後の理論計算でのビットマップと実測でのビットマップとの具体例を示す図である。
【図３３】ＩＳＤＮの速度性能の推定を行なう場合のフィッティング処理の具体例を示すフローチャートである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transmission performance simulation program, a transmission performance simulation method, and a recording medium on which the program is recorded, and more particularly, to a transmission performance simulation program for simulating the transmission performance of ISDN or xDSL, a transmission performance simulation method, and recording the program. Related to the recording medium.
[0002]
[Prior art]
2. Description of the Related Art In recent years, xDSL (Digital Subscriber Line), which is a transmission system using a metallic cable (copper wire line) and is a technology for transmitting digital data at high speed, is rapidly spreading.
[0003]
For example, in Japan, a transmission method called ADSL (Asymmetric Digital Subscriber Line) has been put to practical use. ADSL is Asymmetric; as it is called asymmetric, the transmission speed in the downstream direction from the telephone station to the user is 1.5 to 12 Mbps, and the transmission speed in the upstream direction from the user to the telephone station is 16 to 1 Mbps at the maximum. It is characterized by having. Also, as one of xDSL, an optical fiber is used for a part of the route, the transmission speed in the down direction from the telephone station to the user is 13 to 52 Mbps, and the transmission speed in the up direction from the user to the telephone station is 1. There is also a VDSL (Very high-bit-rate Digital Subscriber Line), which is 5 to 30 Mbps and has a maximum transmission distance of 300 m (downstream 52 Mbps) to 1 km (downstream 13 Mbps).
[0004]
In such xDSL, high-speed data transfer of Mbps class can be performed using a high-frequency band not used in voice transmission in a telephone, but transmission performance due to noise called crosstalk depends on the frequency used. The problem of decline has been pointed out.
[0005]
Usually, since a telephone cable has a structure in which a plurality of lines are integrated into one, a signal transmitted on another line in the same cable is taken into the own line as noise. This is called crosstalk, and is a major cause of deteriorating the SNR (signal power to noise power ratio) of the received signal and reducing the length of a line that can be transmitted and the transmission speed. Further, when the crosstalk is large, it may be impossible to provide the xDSL service to a line having a long line length. For this reason, spectrum compatibility between xDSL and ISDN is examined, and as a result, some measures such as restricting a line in a cable are required between transmission systems that are likely to be greatly affected by crosstalk.
[0006]
[Non-patent document 1]
Established by the Telegraph and Telephone Technical Committee, “TDM Standard JJ-100.01 Spectrum Management for Metallic Transmission Systems”, first edition, November 27, 2001.
[0007]
[Problems to be solved by the invention]
However, as in the case of the conventional xDSL performance evaluation method, performing evaluation by actual measurement without using simulation under various conditions requires a great deal of labor and time in preparation for measurement. was there. Also, depending on the conditions, there was a problem that it could not be constructed at the laboratory level. Therefore, there is a problem that the performance evaluation of xDSL under various environments can be performed only in a limited range.
[0008]
Further, as described above, when performance evaluation is performed by actual measurement, the environment differs for each actual measurement evaluation due to the characteristics of the equipment and the factors of the experimental environment. In addition, there has not been a program that can calculate the performance of all main types of xDSL under the same conditions. Therefore, there is a problem that it is difficult to compare the performance of different types of xDSL under the same conditions. Further, there is a problem that it is difficult to determine the magnitude of mutual interference (spectral suitability) generated when different types of xDSL lines are accommodated in the same cable.
[0009]
The present invention has been made in view of these problems, and provides a transmission performance simulation program, a transmission performance simulation method, and a recording medium on which the program is capable of performing ISDN or xDSL performance evaluation by calculation. The purpose is to:
[0010]
[Means for Solving the Problems]
To achieve the above object, according to an aspect of the present invention, a transmission performance simulation program is a transmission performance simulation program that calculates transmission performance in a transmission system using a metallic cable, and a frequency characteristic of a transmission spectrum, A receiving step of receiving a setting value of the transmission system including the crosstalk attenuation and the transmission line length, and a first calculating step of calculating a power spectrum density of a received signal of the transmission system using the received setting value. A second calculating step of calculating an interference noise intensity of another transmission system existing on a line different from the line of the transmission system by using the received set value, a calculated power spectrum density, and a calculated noise The transmission line length and the signal power to noise power ratio of the received signal or the transmission A third calculation step of calculating the relationship between the degree to execute an output step of outputting the calculated result to the computer.
[0011]
By using the above-described transmission performance simulation program, it is possible to efficiently calculate the performance of xDSL or ISDN, which are transmission systems using a metallic cable.
[0012]
Further, in the above-mentioned accepting step, a setting relating to another transmission system is further accepted, and in the first calculating step, another transmission is set by using the setting value relating to the accepted transmission system and the setting relating to the accepted other transmission system. It is desirable to calculate the power spectrum density of the received signal of the transmission system under system interference.
[0013]
By using such a transmission performance simulation program, the performance of all the main types of xDSL and ISDN can be calculated by one program under all environments of the main line. That is, in such a transmission performance simulation program, it is possible to calculate the performance of all types of main xDSL and SDN under all environments of main lines only by changing the set value.
[0014]
Further, the transmission performance simulation program compares the calculation result in the first calculation step with a preset threshold value to determine a spectrum suitability between the transmission system and another transmission system. Further, it is desirable that the program be executed by a computer.
[0015]
By using such a transmission performance simulation program, the performance of different types of xDSL and ISDN can be calculated under the same conditions. Therefore, it is possible to compare the performance of ISDN and xDSL under these conditions.
[0016]
Also, in the above-described receiving step, setting values for a plurality of types of transmission systems are received, and in the first calculation step, the setting values of the plurality of types of transmission systems received in the receiving step are used to determine the transmission system. A power spectrum density of a received signal is calculated for each of a plurality of types of transmission systems under interference of a predetermined other transmission system existing on a separate line from the line, and in a third calculation step, each calculated power spectrum density is calculated. Using the power spectrum density of the transmission system and the calculated noise intensity, the relationship between the transmission line length and the signal-to-noise power ratio or transmission speed of the received signal for a plurality of types of transmission systems is calculated. , The transmission performance simulation program uses the calculation results for multiple types of transmission Possible to execute the comparison step for comparing the performance of the transmission system further computer is desirable.
[0017]
By using such a transmission performance simulation program, the interference between ISDN and a plurality of xDSLs can be calculated and compared with a predetermined criterion. Therefore, the magnitude of spectrum suitability can be automatically determined.
[0018]
In addition, the transmission performance simulation program sets the transmission system received in the receiving step in order to match the calculated result with the actually measured value when a predetermined difference exists between the calculated result and the actually measured value. It is desirable that the computer further execute an adjusting step of adjusting the value.
[0019]
In such a transmission performance simulation program, it is possible to estimate the performance of the device under conditions that are difficult to measure by simply inputting the setting parameters according to the characteristics of the device.
[0020]
Further, the transmission performance simulation program uses the adjusted setting value to cause the computer to execute the first calculation step, the second calculation step, and the third calculation step, and obtains a result obtained by the transmission system. It is desirable to estimate that the calculation result is for a second transmission system different from.
[0021]
In such a transmission performance simulation program, by using the setting parameters of the conventional device, it is possible to estimate the performance of a device which is under development or is to be developed and which does not yet exist.
[0022]
Further, in the case where the above-described transmission system is a transmission system using a multicarrier transmission scheme, the calculated result is on-board bit information, and the setting value for the transmission system to be adjusted is the background noise intensity and the background noise intensity. It is desirable to be at least one of a maximum tone number, a minimum tone number, a crosstalk attenuation amount, and a noise margin.
[0023]
This makes it possible to estimate the performance of a transmission system using a multicarrier transmission scheme such as the xDSL transmission scheme.
[0024]
Alternatively, when the transmission system described above is a transmission system using a single carrier transmission system or a baseband transmission system, the calculated result is the maximum distance information that can be transmitted in the transmission system, and Desirably, the set value for the system is at least one of background noise intensity and crosstalk attenuation.
[0025]
This makes it possible to estimate the performance of a transmission system using a single carrier transmission method such as the ISDN transmission method or a baseband transmission method.
[0026]
According to another aspect of the present invention, a transmission performance simulation method is a transmission performance simulation method for calculating transmission performance in a transmission system using a metallic cable, comprising: a frequency characteristic of a transmission spectrum; a crosstalk attenuation; A receiving step of receiving a set value of the transmission system including the length, a first calculating step of calculating a power spectrum density of a received signal of the transmission system using the received set value, and a step of using the received set value. A second calculating step of calculating the interference noise intensity of another transmission system existing on a line different from the line of the transmission system, the calculated power spectrum density, and the calculated noise intensity. A third calculating step of calculating the relationship between the length and the signal power to noise power ratio or transmission rate of the received signal; And an output step of outputting the computed result.
[0027]
By using the above-described transmission performance simulation method, it is possible to efficiently calculate the performance of xDSL or ISDN, which is a transmission system using a metallic cable.
[0028]
Further, in the above-mentioned accepting step, a setting relating to another transmission system is further accepted, and in the first calculating step, another transmission is set by using the setting value relating to the accepted transmission system and the setting relating to the accepted other transmission system. It is desirable to calculate the power spectrum density of the received signal of the transmission system under system interference.
[0029]
By using such a transmission performance simulation method, the performance of all main types of xDSL and ISDN can be calculated by one program under all environments of the main line. That is, in such a transmission performance simulation method, it is possible to calculate the performance of all the main types of xDSL and ISDN under all the environment of the main line only by changing the set value.
[0030]
In addition, the transmission performance simulation method includes a determining step of determining the spectral compatibility between the transmission system and another transmission system by comparing a calculation result in the first calculation step with a preset threshold value. It is desirable to provide further.
[0031]
By using such a transmission performance simulation method, the performance of different types of xDSL and ISDN can be calculated under the same conditions. Therefore, it is possible to compare the performance of ISDN and xDSL under these conditions.
[0032]
Also, in the above-described receiving step, setting values for a plurality of types of transmission systems are received, and in the first calculation step, the setting values of the plurality of types of transmission systems received in the receiving step are used to determine the transmission system. A power spectrum density of a received signal is calculated for each of a plurality of types of transmission systems under interference of a predetermined other transmission system existing on a separate line from the line, and in a third calculation step, each calculated power spectrum density is calculated. Using the power spectrum density of the transmission system and the calculated noise intensity, the relationship between the transmission line length and the signal-to-noise power ratio or transmission speed of the received signal for a plurality of types of transmission systems is calculated. , Comparing the performance of multiple types of transmission systems using the calculation results for multiple types of transmission systems It may further include a step.
[0033]
By using such a transmission performance simulation method, interference between ISDN and a plurality of xDSLs can be calculated and compared with a predetermined criterion. Therefore, the magnitude of spectrum suitability can be automatically determined.
[0034]
In addition, the transmission performance simulation method is based on the transmission system received in the receiving step in order to match the calculated result with the actually measured value when a predetermined difference exists between the calculated result and the actually measured value. It is preferable that the method further includes an adjusting step of adjusting the set value.
[0035]
In such a transmission performance simulation method, it is possible to estimate the performance of the device under conditions that are difficult to measure by simply inputting the setting parameters according to the characteristics of the device.
[0036]
Further, the transmission performance simulation method uses the adjusted setting value to execute a first calculation step, a second calculation step, and a third calculation step, and obtains a result obtained by executing the first calculation step, the second calculation step, and the third calculation step. Is desirably estimated to be a calculation result for a different second transmission system.
[0037]
In such a transmission performance simulation method, by using the setting parameters of the conventional device, it is possible to estimate the performance of a device which is in the process of being developed or is to be developed and which does not yet exist.
[0038]
Further, in the case where the above-described transmission system is a transmission system using a multicarrier transmission scheme, the calculated result is on-board bit information, and the setting value for the transmission system to be adjusted is the background noise intensity and the background noise intensity. It is desirable to be at least one of a maximum tone number, a minimum tone number, a crosstalk attenuation amount, and a noise margin.
[0039]
This makes it possible to estimate the performance of a transmission system using a multicarrier transmission scheme such as the xDSL transmission scheme.
[0040]
Alternatively, when the transmission system described above is a transmission system using a single carrier transmission system or a baseband transmission system, the calculated result is the maximum distance information that can be transmitted in the transmission system, and Desirably, the set value for the system is at least one of background noise intensity and crosstalk attenuation.
[0041]
This makes it possible to estimate the performance of a transmission system using a single carrier transmission method such as the ISDN transmission method or a baseband transmission method.
[0042]
According to still another aspect of the present invention, a recording medium is a computer-readable recording medium, and records the above-described transmission performance simulation program.
[0043]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0044]
In the present embodiment, a simulation program (hereinafter, simply referred to as a simulation program) capable of evaluating the influence of crosstalk noise under various conditions in a line model as shown in FIG. 1 will be described. . That is, referring to FIG. 1, when transmission is performed from the own line transmitter to the own line receiver via the own line, under the influence of the other line which is a crosstalk source, the influence of background noise, and the like. This is a program that evaluates the transmission of data.
[0045]
The simulation program of the present invention relates to a transmission system using a metallic cable (copper wire line), such as ADSL (Asymmetric Digital Subscriber Line) and VDSL (Very high-bit-rate Digital Subscriber Line). It is characterized by outputting the relationship between the line length and the SNR of the received signal. Also, for xDSL, a relation between a line length and a transmittable speed is output.
[0046]
Further, the simulation program according to the present embodiment is characterized in that, regarding the transmission characteristics of ISDN, which is a transmission system using a digital line, the relationship between the line length and the SNR of the received signal is also output. In addition, a feature of the present invention is to output a relationship between a line length and a transmittable speed for ISDN.
[0047]
Next, FIG. 2 shows a simulation method in the present simulation program.
[0048]
Referring to FIG. 2, in this simulation program, transmission PSD (power spectrum density: S) of a transmission signal of the own line and noise (N) including far-end crosstalk, near-end crosstalk, and white noise are considered. Then, an S / N ratio (signal-to-noise ratio; signal power to noise power ratio) is calculated as a performance calculation, and the transmission performance is evaluated using the calculated S / N ratio.
[0049]
The transmission PSD on the own line and the transmission PSD on the crosstalk line described above are values depending on each transmission method. The signal power (S) is obtained by taking into account the line attenuation depending on the insulating material and the diameter of the transmission line in the transmission PSD. Specifically, when determining the transmission PSD in the own line, the signal power of the transmission signal is obtained in consideration of the line attenuation characteristics including the line attenuation and the insulating material of the own line in the transmission spectrum in the own line. When calculating the transmission PSD in the crosstalk line, the near-end crosstalk spectrum including the line attenuation and the insulation material is considered in the near-end crosstalk spectrum, and the line attenuation and the insulation material and the like are included in the far-end crosstalk spectrum. The signal power due to crosstalk is obtained in consideration of the far-end crosstalk characteristics including the above. The near-end crosstalk and the far-end crosstalk will be described later.
[0050]
Further, white noise constituting noise depends on the intensity of background noise.
As described above, the S / N ratio calculation depends on the transmission method, and further depends on the type of the equalizer (equalizer).
[0051]
The calculation method employed in each process of the simulation program will be described below.
[0052]
(1) First, to calculate the SNR, first, the PSD of the received signal (own line side) and the PSD of the noise intensity (crosstalk line side) are obtained for each frequency.
[0053]
The method of calculating the SNR from the above-mentioned PSD differs depending on the transmission method and the method of the equalizer mounted on the communication device.
[0054]
Therefore, hereinafter, transmission in ISDN when a communication device is equipped with a linear equalizer used for ISDN performance calculation and a linear equalizer used for ISDN performance calculation based on ANSI (American National Standards Institute) standards as equalizers. Will be described below, and the calculation of the SNR in xDSL transmission when a DFE (Decision Feedback Back Equalizer) is mounted. The calculation of the SNR in xDSL transmission in the multicarrier scheme will be described.
[0055]
(1-1) Linear equalizer
The calculation method using the linear equalizer is a method of multiplying the PSD of the received signal by the inverse characteristic (known characteristic) of the line attenuation.
[0056]
Referring to FIG. 2, the PSD of the received signal is obtained by multiplying the PSD of the transmitted signal by the line attenuation. Therefore, when the signal passes through the equalizer and is multiplied by the inverse characteristic of the line attenuation, the PSD of the received signal after passing through the equalizer becomes equal to the PSD of the transmission signal. Therefore, the required SNR (dB) is shown in the following equation (1).
[0057]
(Equation 1)

[0058]
However, in the above equation (1), S (f) is the transmission signal strength, the unit is mW / Hz, and the PSD described later is used. At this time, it is necessary to convert the unit from dBm / Hz to mW / Hz.
[0059]
N (f) is the noise intensity, and the unit is mW / Hz.
| H (f) |, which is the inverse characteristic of line attenuation^-2Is the line attenuation characteristic | H (f) |²Is the reciprocal of
[0060]
F (f) is a reception filter, which depends on the characteristics of the terminal used. In the ISDN simulation, F (f) is given as in the following equation (2), assuming a cosine roll-off filter.
[0061]
(Equation 2)

[0062]
Note that in the above equation (2), the symbol rate f_symUses the values shown in FIG.
[0063]
(1-2) ANSI linear equalizer
This is a method for ISDN transmission according to the standard of ANSI (American Standards Association).
[0064]
The SNR (dB) obtained by the linear equalizer based on ANSI is shown in the following equation (3).
[0065]
(Equation 3)

[0066]
Note that in the above equation (2), the symbol rate f_symUses the values shown in FIG.
[0067]
The f-SNR is a folded SNR (folded SNR), and is represented by the following equation (4).
[0068]
(Equation 4)

[0069]
However, in the above equation (4), S (f) is the transmission signal strength, the unit is mW / Hz, and the PSD described later is used. At this time, it is necessary to convert the unit from dBm / Hz to mW / Hz. N (f) is the noise intensity, and the unit is mW / Hz. | H (f) |²Is the characteristic of the line attenuation.
[0070]
(1-3) DEF for baseband
Specifically, transmission in xDSL in the case where the DFE is installed is specifically transmission in xDSL adopting a 2B1Q (two binary to one quarternary) system or a pulse amplitude modulation (PAM) system which is a fixed-rate transmission system. HDSL, SHDSL, and the like. The DFE at this time is a DFE based on ANSI used for a transmission method for baseband. In this case, the obtained SNR (dB) is shown in the following equation (5).
[0071]
(Equation 5)

[0072]
Note that in the above equation (5), the symbol rate f_symUses the values shown in FIG.
[0073]
The f-SNR is a folded SNR, and is represented by the following equation (6).
[0074]
(Equation 6)

[0075]
However, in the above equation (6), S (f) is the transmission signal strength, the unit is mW / Hz, and the PSD described later is used. At this time, it is necessary to convert the unit from dBm / Hz to mW / Hz. N (f) is the noise intensity, and the unit is mW / Hz. | H (f) |²Is the characteristic of the line attenuation.
[0076]
(1-4) DFE for pass band
As a transmission in xDSL when a DFE is mounted, a method of calculating an SNR when a DFE for a pass band, which is another DFE, is also described.
[0077]
In this case, it is better to consider that the center band has shifted to fc (kHz) with respect to the case where DFE based on ANSI used for the transmission method for baseband is mounted, and the SNR (dB) to be obtained is as follows. It is shown in equation (7).
[0078]
(Equation 7)

[0079]
Note that in the above equation (7), the symbol rate f_symUses the values shown in FIG. 3, and the center band fc is a technical specification of xDSL for Europe. 991.1 Annex B (CAP 1-pair) and G. et al. In the case of 991.1 Annex B (CAP 2-pairs), the frequencies are 226 kHz and 138 kHz.
[0080]
The f-SNR is a folded SNR, and is represented by the following equation (8).
[0081]
(Equation 8)

[0082]
However, in the above equation (8), S (f) is the transmission signal strength, the unit is mW / Hz, and the PSD described later is used. At this time, it is necessary to convert the unit from dBm / Hz to mW / Hz. N (f) is the noise intensity, and the unit is mW / Hz. | H (f) |²Is the characteristic of the line attenuation.
[0083]
(1-5) Multi-carrier system
Further, in the case of ADSL or SSDL, which is a multi-carrier xDSL transmission system and a variable speed transmission system, the sum b of the number of bits that can be mounted on each of the m-th to n-th subcarriers was obtained. Above, the transmission rate is derived, and the SNR is obtained. Note that the sum b of the number of bits that can be mounted on each of the m-th to n-th subcarriers is expressed by the following equation (9).
[0084]
(Equation 9)

[0085]
However, in the above equation (9), Si (f) is the transmission signal strength of the i-th subcarrier, Ni (f) is the noise strength of the i-th subcarrier, and | Hi (f) |²Is the line attenuation characteristic of the i-th subcarrier. Γ is an effective SNR gap which satisfies the following equation.
[0086]
Γ = 9.75-C + M
Here, C is a coding gain, and M is a noise margin, each of which is a unique parameter used for evaluating each transmission method.
[0087]
In a system where data is transmitted in byte units such as ADSL, the total number b of bits is rounded down to a multiple of eight.
[0088]
To determine the transmission rate, this value may be multiplied by the symbol rate.
(2) Next, the noise inserted in the simulation program will be described.
[0089]
There are various types of noise. In this simulation program, crosstalk and white noise are inserted as additive noise. That is, the noise N (f) is expressed by the following equation (10).
[0090]
(Equation 10)

[0091]
However, in the above equation (10), PSD_NEXT(F) and PSD_FEXT(F) represents the amount of near-end crosstalk and far-end crosstalk. Details will be described later. W (f) represents the magnitude of white noise. Usually, -140 dBm / Hz is adopted as white noise.
[0092]
Further, near-end crosstalk and far-end crosstalk will be described with reference to the drawings. FIG. 4 is a diagram illustrating near-end crosstalk and far-end crosstalk.
[0093]
Referring to FIG. 4, there are two types of crosstalk called near-end crosstalk and far-end crosstalk. Typically, near-end crosstalk is much larger than far-end crosstalk.
[0094]
As an example of a case where near-end crosstalk does not occur, there is a case where an uplink signal and a downlink signal are temporally separated to synchronize with another transmission system. To be more specific, ISDN (Japan) and x. 992.1 / G. 992.2 (ADSL) Annex C-FBM and G.I. Since 992.1 AnnexH is synchronized with each other at 400 Hz, when calculating the influence of crosstalk due to these transmission methods, near-end crosstalk is not calculated assuming that near-end crosstalk does not occur.
[0095]
The crosstalk intensity depends on the intensity of the transmission signal of the crosstalk source, the number of crosstalk source lines existing in the same cable, and the material of the transmission line, and does not depend on the transmission method.
[0096]
Next, each of near-end crosstalk and far-end crosstalk will be described.
(2-1) Near-end crosstalk
The PSD (intensity) (mW / Hz) of the near-end crosstalk is expressed by the following equation (11).
[0097]
(Equation 11)

[0098]
However, in the above equation (11), PSD_disturberIs the transmission signal strength (mW / Hz) from the crosstalk source, and uses the PSD described later. At this time, it is necessary to convert the unit from dBm / Hz to mW / Hz.
[0099]
NPSL is a constant indicating the near-end crosstalk attenuation at 160 kHz, and uses a predetermined value defined by ITU-TS (International Telecommunication Union).
[0100]
(2-2) Far-end crosstalk
The PSD (intensity) (mW / Hz) of far-end crosstalk is expressed by the following equation (12).
[0101]
(Equation 12)

[0102]
However, in the above equation (12), FPSL is a constant indicating the near-end crosstalk attenuation at 160 kHz, and uses a predetermined value defined by the ITU-TS.
[0103]
(3) Next, line attenuation will be described.
Line attenuation depends on the attenuation constant and the transmission line length.
[0104]
K is the decrement constant of the transmission path_LOOP(DB / km) and the line length is d (km), the lower line attenuation characteristic | H (f) |²Is represented by the following equation (13).
[0105]
(Equation 13)

[0106]
FIG. 5 shows a graph of the transmission line attenuation constant of a transmission line of a representative material and diameter. FIG. 5 is a diagram showing transmission line attenuation constants for transmission lines of four types of materials and diameters.
[0107]
(4) In this simulation program, the S / N ratio is determined from the PSD on the transmission side (own line side) and the PSD on the crosstalk side (crosstalk line side) obtained in this way, and the transmission characteristics of xDSL and ISDN are determined. Perform an evaluation. A calculation method for evaluating the transmission characteristics of the own line when the transmission method of the own line is ISDN and specific xDSL will be described below.
[0108]
(4-1) Evaluation of ISDN transmission characteristics
The evaluation of the transmission characteristics of the ISDN is performed using the SNR in the transmission in the ISDN when the linear equalizer described in the above (1-1) is mounted. As the noise at this time, the near-end crosstalk described in the above (2-1), the far-end crosstalk described in the above (2-2), and the white noise of -140 dBm / Hz which is a normal white noise Is used. Then, the calculated SNR is compared with a threshold value of 26.46 (dB), and when the calculated SNR is equal to or larger than the threshold value, it is evaluated that transmission by the ISDN method is possible. .
[0109]
(4-2) Evaluation of transmission characteristics of ADSL (G.992.1 / G.992.2 AnnexA)
G. of ADSL 992.1 / G. The evaluation of the transmission characteristics of 992.2 Annex A is performed using the SNR in xDSL transmission performed by the multicarrier method described in the above (1-5). As the noise at this time, the near-end crosstalk described in the above (2-1), the far-end crosstalk described in the above (2-2), and the white noise of -140 dBm / Hz which is a normal white noise Is used. Note that the parameters shown in FIG. 6 are used as the other parameters.
[0110]
(4-3) Evaluation of transmission characteristics of ADSL (G.992.1 / G.992.2 AnnexC)
G. of ADSL 992.1 / G. Similarly, the evaluation of the transmission characteristics of 992.2 Annex C-FDM is performed using the SNR described in the above (1-5). As the noise at this time, the near-end crosstalk described in the above (2-1), the far-end crosstalk described in the above (2-2), and the white noise of -140 dBm / Hz which is a normal white noise Is used. However, if the crosstalk source is a system that transmits in synchronization with ISDN, the PSD_NEXT(F) the sum of near-end crosstalk and white noise as PSD_FEXTUsing the sum of the far-end crosstalk and white noise as (f), the near-end crosstalk described in (2-1) and the far-end crosstalk described in (2-2) are used as crosstalk sources. . The other parameters are the same as the parameters shown in FIG.
[0111]
(4-4) Evaluation of transmission characteristics of SSDL (G.992.1 AnnexH)
One of the ADSL standards, G.100. The evaluation of the transmission characteristics of SSDL (G.992.1 AnnexH), which is a supplementary standard of G.992.1 (G.dmt) and is a transmission method based on the standard, is similarly performed in (1-5) above. This is performed using the described SNR. As the noise at this time, the near-end crosstalk described in the above (2-1), the far-end crosstalk described in the above (2-2), and the white noise of -140 dBm / Hz which is a normal white noise Is used. However, in the case where the crosstalk source is a system that transmits in synchronization with ISDN, the sum of the far-end crosstalk and white noise is used as noise, and the near-end crosstalk described in (2-1) above is used. And the far-end crosstalk described in (2-2) are used as crosstalk sources. As the other parameters, the parameters shown in FIG. 7 are used.
[0112]
(4-5) Evaluation of transmission characteristics of SHDSL
The evaluation of the transmission characteristics of SHDSL, which is the technical specification of the vertically symmetric xDSL, is performed using the SNR in xDSL transmission when the DFE described in (1-3) described above is mounted. As the noise at this time, the near-end crosstalk described in the above (2-1), the far-end crosstalk described in the above (2-2), and the white noise of -140 dBm / Hz which is a normal white noise Is used. Then, the calculated SNR is compared with a threshold value of 29.7 (dB), and when the calculated SNR is equal to or more than the threshold value, it is evaluated that transmission in the SHDSL system is possible. .
[0113]
(4-6) Evaluation of transmission characteristics of SDSL adopting 2B1Q method
Similarly, the evaluation of the transmission characteristics of the SDSL adopting the 2B1Q scheme is performed using the SNR described in the above (1-3). As the noise at this time, the near-end crosstalk described in the above (2-1), the far-end crosstalk described in the above (2-2), and the white noise of -140 dBm / Hz which is a normal white noise Is used. Then, the calculated SNR is compared with a threshold value of 27.4 (dB), and when the calculated SNR is equal to or more than the threshold value, it is evaluated that transmission by the SDSL method is possible. .
[0114]
(5) Next, the transmission signal PSD on the crosstalk side when each transmission method is assumed as the crosstalk side will be described. The characteristics of each transmission scheme are shown in FIG.
[0115]
(5-1) When the transmission method of the crosstalk source is TCM-AMI ISDN (Japan)
When the TCM-AMI ISDN (Japan) transmission system itself is a crosstalk source of the ISDN, the crosstalk-side transmission signal PSD is expressed by the following equation (14). Note that the device impedance in this case is 110 (Ω).
[0116]
[Equation 14]

[0117]
Here, in the above equation (14), f indicates a frequency, and f₀= 320 × 10³(Hz), f_3dB= 2 × f₀And Also, K_DSLIs the coefficient, K_DSL= V_OP ²/ 4R (W). When the device impedance is 110 (Ω), V_OPIs V_OP= 6.00 (V).
[0118]
(5-2) When the transmission method of the crosstalk source is 2B1Q ISDN (USA)
When the transmission system of 2B1Q ISDN (USA) is a crosstalk source, the transmission signal PSD on the crosstalk side is expressed by the following equation (15). In this case, the device impedance is 135 (Ω).
[0119]
(Equation 15)

[0120]
FIG. 9 shows a crosstalk-side transmission signal PSD when the above-described TCM-AMI ISDN (Japan) is a crosstalk source and a crosstalk-side transmission signal PSD when 2B1Q ISDN (USA) is a crosstalk source. Show.
[0121]
(5-3) The transmission method of the crosstalk source is G. 992.1 / G. 992.2 (ADSL G. dmt / G. Lite) Downstream of AnnexA / AnnexC-DBM
G. FIG. 992.1 / G. A transmission signal PSD on the crosstalk side when the downlink transmission system of 992.2 (ADSL G.dmt / G.lite) AnnexA / AnnexC-DBM is a crosstalk source is expressed by the following equation (16).
[0122]
(Equation 16)

[0123]
(5-4) If the transmission method of the crosstalk source is G. 992.1 / G. 992.2 (ADSL G.dmt / G.lite) In the case of an upward direction of AnnexA / AnnexC-DBM
G. FIG. 992.1 / G. A transmission signal PSD on the crosstalk side when the uplink transmission system of 992.2 (ADSL G.dmt / G.lite) AnnexA / AnnexC-DBM is a crosstalk source is expressed by the following equation (17).
[0124]
[Equation 17]

[0125]
Further, the above G.I. 992.1 / G. 992.2 (ADSL G.dmt / G.lite) Transmission signal PSD on the crosstalk side when the downstream direction of AnnexA / AnnexC-DBM is the crosstalk source, and transmission signal on the crosstalk side when the upstream direction is the crosstalk source The PSD is shown in FIGS. 10 and 11. FIG. 992.1 (ADSL G.dmt) shows a transmission signal PSD on the crosstalk side when the downlink direction of AnnexA / AnnexC-DBM is a crosstalk source, and a transmission signal PSD on the crosstalk side when the uplink direction is a crosstalk source. FIG. 992.2 (ADSL G.lite) shows a transmission signal PSD on the crosstalk side when the downstream direction of AnnexA / AnnexC-DBM is a crosstalk source, and a transmission signal PSD on the crosstalk side when the upstream direction is a crosstalk source. FIG.
[0126]
(5-5) The transmission method of the crosstalk source is G. 991.1 (HDSL) AnnexA (2B1Q)
G. FIG. The transmission signal PSD on the crosstalk side when the transmission method of 991.1 (HDSL) Annex A (2B1Q) is a crosstalk source is expressed by the following equation (18). In this case, the device impedance is 135 (Ω).
[0127]
(Equation 18)

[0128]
(5-6) SDSL (2B1Q)
The transmission signal PSD on the crosstalk side when the SDSL (2B1Q) transmission method specified by ANSI is a crosstalk source is represented by the following equation (19). In this case, the device impedance is 135 (Ω).
[0129]
[Equation 19]

[0130]
However, in the above equation (19), the symbol rate f_symUses the values shown in FIG.
[0131]
Further, the above G.I. FIG. 12 shows a transmission signal PSD on the crosstalk side when 991.1 (HDSL) AnnexA (2B1Q) is a crosstalk source and a transmission signal PSD on the crosstalk side when SDSL (2B1Q) is a crosstalk source. FIG. 991.1 (HDSL) When the AnnexA (2B1Q) is the crosstalk source and when the SDSL (2B1Q) is the crosstalk source, the data transmission speed in the SDSL (2B1Q) is 784 (kbps), 1552 (kbps), FIG. 13 is a diagram showing a transmission signal PSD on the crosstalk side when the transmission signal is 2320 (kbps).
[0132]
(5-7) The transmission method of the crosstalk source is G. 991.1 (HDSL) Annex B (CAP 1-pair / 2-pairs)
G. FIG. When 991.1 (HDSL) Annex B (CAP 1-pair / 2-pairs) is a crosstalk source, the transmission power is determined by referring to the PSD average power graphs and tables shown in FIG. 13 and FIG. The transmission signal PSD on the crosstalk side is obtained. FIG. 13 shows a graph of the transmission signal PSD average power on the crosstalk side when HDSL (CAP) is the crosstalk source, and FIG. 14 shows a table. In this case, the device impedance is 135 (Ω).
[0133]
(5-8) When the transmission method of the crosstalk source is G. 991.2 (SHDSL, PAM) AnnexA Asymmetric PSD 1.5 Mbps downstream
G. FIG. 991.2 (SHDSL, PAM) AnnexA Asymmetric PSD In the case where the 1.5 Mbps downlink direction becomes a crosstalk source, the transmission signal is obtained by referring to the graph and table of the PSD mask to obtain the crosstalk-side transmission signal PSD. .
[0134]
FIG. 15 and FIG. 991.2 (SHDSL, PAM) Annex A Asymmetric PSD is a diagram showing a graph and a table of a PSD mask when a crosstalk source of 1.5 Mbps becomes a crosstalk source. FIG. 15 is a diagram showing a graph of the PSD mask when Power Backoff is 0 (dB). The PSD mask values shown in the table of the PSD mask at each frequency shown in FIG. 16 are connected by straight lines. Things. In this case, the device impedance is 135 (Ω).
[0135]
(5-9) The transmission method of the crosstalk source is G. 991.2 (SHDSL, PAM) AnnexA Asymmetric PSD 1.5 Mbps upstream
G. FIG. 991.2 (SHDSL, PAM) AnnexA Asymmetric PSD If the upstream direction of 1.5 Mbps becomes a crosstalk source, the above-mentioned G.99. 991.2 (SHDSL, PAM) AnnexA Asymmetric Psd Similar to the case where the 1.5 Mbps downlink is a crosstalk source, the transmission power is obtained by referring to a graph and a table of the PSD mask to obtain a transmission signal PSD on the crosstalk side. Get.
[0136]
FIG. 17 and FIG. FIG. 99B is a diagram showing a graph and a table of the PSD mask in a case where the crosstalk source is the uplink direction of 991.2 (SHDSL, PAM) AnnexA Asymmetric PSD 1.5 Mbps. FIG. 17 is a diagram showing a graph of the PSD mask when Power Backoff is 0 (dB), and the PSD mask values shown in the PSD mask table at each frequency shown in FIG. 18 are connected by straight lines. Things. In this case, the device impedance is 135 (Ω).
[0137]
(5-10) If the transmission method of the crosstalk source is G. 991.2 (SHDSL, PAM) AnnexA Symmetric PSD
G. FIG. A transmission signal PSD on the crosstalk side when the transmission system of 991.2 (SHDSL, PAM) AnnexA Symmetric PSD is a crosstalk source is expressed by the following equation (20).
[0138]
(Equation 20)

[0139]
FIG. 19 shows SHDSL (symmetric PSD) parameters used in the above equation (20). FIG. It is a figure which shows the parameter used for the transmission signal PSD of 991.2 (SHDSL, PAM) AnnexA Symmetric PSD when it becomes a crosstalk source on the crosstalk side. In this case, the device impedance is 135 (Ω).
[0140]
FIG. 20 shows a transmission signal PSD in the SHDSL (symmetric PSD) transmission method. FIG. 20 shows a transmission signal PSD on the crosstalk side when the data transmission speed is 1536 (kbps), 768 (kbps), and 384 (kbps) in the case where the transmission scheme of the SHDSL (symmetric PSD) is a crosstalk source. FIG.
[0141]
(5-11) The transmission method of the crosstalk source is G. 992.1 AnnexH (SSSL)
G. FIG. When the transmission system of Annex H (SSDSL) is the crosstalk source, the transmission signal PSD on the crosstalk side is G.99 in both the upstream and downstream directions. 992.1 (ADSL G.dmt) is the same as the transmission signal PSD on the crosstalk side when the transmission system is a crosstalk source, and the description thereof will not be repeated.
[0142]
(6) Next, a simulation program according to the present embodiment will be described.
[0143]
This simulation program allows the computing device to perform the above-described calculation, thereby obtaining the transmission characteristics of ISDN under the influence of another transmission method and the G.100 under the influence of another transmission method. 991.2 (SHDSL, PAM) AnnexA Symmetric PSD 1.5 Mbps transmission characteristics, and G.100 under the influence of other transmission schemes. The transmission characteristics of xDSL such as 991.1 (HDSL) Annex A (2Q1B) are evaluated by automatically outputting the relationship between the line length and the SNR of the received signal.
[0144]
Such a simulation program can be configured using spreadsheet software such as Excel® as basic calculation software. The calculation program executed by the simulation program is modularized in block units, and is used in combination as needed.
[0145]
Hereinafter, a specific worksheet when the present simulation program is configured using spreadsheet software will be described.
[0146]
FIG. 21 is a diagram showing a specific example of a part of a worksheet of a simulation program for evaluating the transmission characteristics of ISDN. The worksheet shown in FIG. 21 is a diagram showing a main screen.
[0147]
The simulation calculation is actually performed on the main screen shown in FIG. Specifically, the calculation is started by inputting all the parameters in a predetermined column of the worksheet and pressing a “calculation execution” button. When evaluating the transmission characteristics of the ISDN, as described in (5-1) above, by comparing the calculated SNR of the transmission characteristics of the ISDN with a threshold value, whether or not transmission in the ISDN system is possible or not is determined. To evaluate. Therefore, the SNR of the transmission characteristic of the ISDN at each line length is displayed on the main screen shown in FIG. Furthermore, whether or not transmission by the ISDN method is possible may be displayed at each line length by comparing with a predetermined threshold value.
[0148]
FIG. 22 shows a list of attenuation characteristics of transmission lines used in the simulation program as shown in FIG.
[0149]
In FIG. 22, the attenuation constant for each 1 (kHz) is shown in Table 1, and the value of the 0.4 mm paper insulation table is shown. Table 2 shows the attenuation constant for each 4.3125 (kHz), and the values for nine types of cables including a 0.4 mm paper insulation table are shown.
[0150]
Since this simulation program is configured using spreadsheet software such as Excel (R), the simulation program includes a list of transmission line attenuation characteristics as shown in FIG. 22 as a worksheet in the simulation program. When executing the program, the program can be executed while reading the list.
[0151]
Further, since the present simulation program is configured using spreadsheet software such as Excel (R), values in an arbitrary calculation process can be displayed. Specifically, FIG. 23 shows a specific example of a worksheet for outputting the transmission signals PSD of all transmission schemes calculated during the execution of the simulation program and the PSD due to near-end crosstalk.
[0152]
As described above, in the simulation configured using the spreadsheet software, in order to confirm whether the PSD value or the like used for the calculation is correct, an arbitrary calculation process as shown in FIG. It is possible to output a screen. Also, of the transmission schemes calculated in the table shown in FIG. 23, NEXT of the crosstalk source and PSD of the transmission scheme to be crosstalked can be graphed to compare the degree of crosstalk of each transmission scheme. it can. Thereby, the approximate effect of the relative crosstalk can be estimated.
[0153]
When a simulation calculation is performed using such a simulation program, parameters of a transmission method to be evaluated are input to cells surrounded by double lines in the main screen shown in FIG. Also, the parameters on the crosstalk side are input. Then, when all the parameters are input and the button of “calculation execution” is clicked, the calculation is executed.
[0154]
Here, it is possible to input an arbitrary parameter from a plurality of types as a parameter for the transmission method to be evaluated. In that case, performance calculation can be performed for each transmission method, and further, the comparison can be performed. This is realized by accepting, on the main screen shown in FIG. 21, input of a parameter for a transmission method for which performance is to be evaluated for a plurality of types of transmission methods, and executing a predetermined calculation formula for each transmission method. .
[0155]
The calculation is realized by executing the above-described calculation formula included in another data sheet not shown in FIG. Further, in another data sheet, characteristic values of a plurality of transmission systems that are candidates for the crosstalk source are recorded, and according to the input parameters of the crosstalk side, the characteristic values of the corresponding transmission system are read out and calculated. Do.
[0156]
When the calculation is completed, a table showing the relationship between the distance of the transmission line and the SNR of the received signal is output on the screen shown in FIG. 21 (below the “execute calculation” button). Also, the calculation result is displayed (right side of the table).
[0157]
FIGS. 24 and 25 are diagrams each showing a specific example of a part of a worksheet of a simulation program for evaluating the transmission characteristics of ADSL. The worksheet shown in FIG. 24 is a diagram showing the main screen, and is a worksheet for inputting parameters relating to environmental conditions such as a crosstalk source and background noise. The worksheet shown in FIG. 25 is a worksheet for inputting parameters relating to the conditions of the device performing ADSL transmission. Then, after inputting all the parameters, the user clicks the “execute calculation” button on the main screen in FIG. 24 to execute the calculation. Note that the details of the calculation here are the same as those in the worksheet for evaluating the transmission characteristics of ISDN described above, and thus the description thereof will not be repeated.
[0158]
Further, the calculation executed in each module used in the simulation program will be specifically described. The calculation program used in each module of the simulation program is composed of a macro language such as Visual Basic (R). Hereinafter, as a specific example, a module constituted by a code in the Visual Basic (R) format will be described.
[0159]
In Visual Basic (R), program codes can be modularized by using a user-defined program.
[0160]
The modules are for each block shown in FIG. 2, that is, a transmission signal transmission spectrum calculation module, a line attenuation characteristic module, a crosstalk signal transmission spectrum (near-end side, far-end side) calculation module, and a near-end crosstalk characteristic calculation module , A far-end crosstalk characteristic calculation module, an S / N ratio calculation module, and a transmission rate calculation module (only for the multi-carrier system). There are also modules that complement the above calculation, such as a common logarithm and a sinc function calculation module.
[0161]
Because this simulation program is composed of such modules, when it is necessary to add or modify the program, such as the appearance of a new transmission spectrum or the appearance of a new equalizer, the corresponding module can be rewritten, There is an advantage that maintenance and expansion are easy.
[0162]
(7) Next, adjustment to the simulation program will be described.
[0163]
Since the simulation program is configured using spreadsheet software such as Excel (R) which is configured in a macro language such as Visual Basic (R) as described above, a predetermined module or a predetermined parameter is stored in the simulation program. By rewriting, the calculated value can be adjusted to be closer to the actually measured value.
[0164]
By using such a simulation program, labor and cost can be significantly reduced as compared with an experiment by actual measurement. Therefore, the performance of ISDN or xDSL can be calculated efficiently. It is also effective when it is desired to efficiently obtain a result assuming various crosstalk conditions in a short time.
[0165]
Further, in the present simulation program, since the calculation of various parameters is modularized, information of the present simulation program can be easily ported to other tools. That is, parameters that are normally used can be freely set without changing the contents of the program, and the operability is excellent. In addition, it can cope with existing simulation programs and has excellent compatibility.
[0166]
Further, as described above, since the simulation program according to the present embodiment has a configuration in which a plurality of modules are combined, all types of ISDN and main xDSL, that is, ISDN and xDSL performance can be calculated. That is, only by changing the set values of the simulation program in the present embodiment, all kinds of performance results of ISDN and main xDSL can be obtained.
[0167]
In addition, by using the simulation program according to the present embodiment to calculate the performance of ISDN and different types of xDSL under the same condition, it is possible to compare the performance of ISDN and xDSL under that condition.
[0168]
Further, by using the simulation program according to the present embodiment, it is possible to calculate the interference between ISDN and xDSL and between xDSL. Therefore, the magnitude of spectrum suitability can be automatically determined by comparing the calculated interference with the determination criterion.
[0169]
As described above, in the present simulation program, the performance of ISDN and xDSL under various conditions can be simulated and evaluated. In addition, by performing the above-described fitting processing based on the simulated values and performing the matching, a simulation close to the actual measurement can be obtained. Further, as shown in FIG. 26, the performance of ISDN or xDSL can be predicted and evaluated without performing actual measurement. Hereinafter, as a specific example of the above-described fitting processing, a case where the speed performance of G992.2 AnnexC downlink, which is ADSL, is estimated will be described. Here, a specific example will be described in which bitmaps of actual measured values and theoretical values are obtained and compared.
[0170]
The bitmap is characterized in that, in the case of a multicarrier transmission scheme such as ADSL, a plurality of subcarriers can carry an independent number of bits. For example, in the case of the ADSL of the G992.2 system, the tone number No. 33-No. Up to 127 sub-carriers can carry an independent number of bits. In this case, a graph or table indicating the number of bits included in each tone is called a bitmap. Since a general method can be used for obtaining the bitmap, a description is not given here.
[0171]
The comparison using such a bitmap is an effective method for comparing the measured value and the calculated value in ADSL, but the comparison method is not limited to the comparison using the bitmap, and other methods are used. It may be a comparison. In this case, it is preferable to use the following fitting parameters according to the comparison method.
[0172]
FIG. 27 is a flowchart showing a specific example of the fitting processing when estimating the speed performance of the ADSL. In the following processing example, it is specifically assumed that there are two types of conditions that can be actually measured: a background noise (white noise) environment and an ADSL crosstalk environment. It is assumed that the ADSL device has a function of displaying a bitmap.
[0173]
Referring to FIG. 27, first, in step S101, a theoretical value and a measured value of a bitmap in the ADSL transmission method under a background noise environment are obtained. The method of finding here is not limited in the present invention, and a general method may be used. The parameters used in the simulation here are the parameters shown in G992.2 in FIG.
[0174]
Next, when a significant difference is found between the calculated theoretical value and the measured value of the bitmap (YES in S103), in step S105, the background noise intensity and the maximum tone number are adjusted so that the bitmaps match. Or adjust the minimum tone number.
[0175]
The matching process in step S105 will be described later.
Next, in step S107, a theoretical value and a measured value of the bitmap in the ADSL transmission method under the ADSL crosstalk environment are obtained. At this time, when the matching is performed in the above-described step S105, the theoretical value of the bitmap in the ADSL transmission method under the ADSL crosstalk environment is obtained using the matched background noise intensity and the like.
[0176]
Next, if a significant difference is found between the theoretical value and the actually measured value of the obtained bitmap (YES in S109), in step S111, the crosstalk attenuation or the noise margin is adjusted so that those bitmaps match. Adjust
[0177]
As described above, the fitting process is completed, and by using the value adjusted in this way, it is possible to perform speed estimation under conditions that cannot be measured.
[0178]
Since the transmission rate in the ADSL transmission method is obtained by multiplying the sum of the number of bits by the symbol rate, the transmission rate in the ADSL transmission method is directly related to the sum of the number of bits mounted for each subcarrier. Therefore, in estimating the actual speed by approaching the actual environment and device characteristics, bitmap matching is important and greatly assists.
[0179]
The fitting process in steps S105 and S111 of the fitting process will be described with reference to a specific example.
[0180]
If the bitmap in the theoretical calculation and the bitmap in the actual measurement under the background noise environment are specifically as shown in FIG. 28, it is determined in step S103 that a significant difference is found between the theoretical calculation and the actual measurement. I do. Although the determination method here is not limited in the present invention, specifically, at a predetermined tone number on the bitmap in the theoretical calculation, the bitmap in the theoretical calculation and the bitmap in the actual measurement are compared. May be determined by detecting that there is a difference equal to or greater than the threshold value in the number of mounted bits. Also, the determination may be made by another method. When it is determined that a significant deviation is found, the fitting is performed using the fitting parameters in step S105 described above.
[0181]
(Adjust the maximum and minimum tone numbers)
Referring to FIG. 28, since the maximum tone number and the minimum tone number are different between the bitmap in the theoretical calculation and the bitmap in the actual measurement, in step S105, these are combined and the frequency band to be used is adjusted. Need to be adjusted. Specifically, referring to FIG. 28, in the actual measurement, the minimum tone number starts from 36 and gradually increases to 42 in the number of mounted bits. This depends on the characteristics of equipment such as an equalizer, and is difficult to simulate in a simulation. Therefore, when matching the maximum tone number and the minimum tone number in the theoretical calculation to those in the actual measurement, the minimum tone number in the theoretical calculation is set to 39 which is an intermediate value between 36 and 42, and the maximum tone numbers are 117 and 122. The carrier used in the simulation is changed to 119 which is an intermediate value between the two. Then, the ADSL transmission speed is approximated. In this way, the total number of bits that can be mounted in the simulation can be substantially adjusted to the actual measurement. FIG. 29 shows a bitmap obtained by the theoretical calculation and a bitmap obtained by the actual measurement after the adjustment of the maximum and minimum tone numbers.
[0182]
(Adjustment of background noise intensity)
Next, referring to FIG. 29, the bitmap in the theoretical calculation is compared with the bitmap in the actual measurement, and the number of mounted bits in the actual measurement is one bit lower than the number of mounted bits in the theoretical calculation as a whole. . From this, it is estimated that the actually measured background noise is higher than the background noise (-140 dBm / Hz) assumed in the theoretical calculation, and the background noise intensity is adjusted. By adjusting the background noise intensity, it is possible to uniformly fit the number of mounted bits of a carrier whose crosstalk noise is smaller than the background noise.
[0183]
Usually, in order to mount one extra bit, it is required that the SNR is increased by 3 dB. Based on this, in the specific example shown in FIG. 29, it is estimated that the actually measured SNR is 3 dB lower than the theoretically calculated SNR, and the background noise is recalculated as -137 dBm / Hz. In this estimation, the recalculation may be performed assuming a predetermined background noise in advance as described above, or the recalculation may be performed sequentially for a certain range of the background noise, and the bit may be measured in each measurement. It may be determined whether or not the image fits the map, and an optimum background noise may be detected. FIG. 30 shows a bitmap in the theoretical calculation and a bitmap in the actual measurement after the adjustment of the background noise intensity is performed.
[0184]
By performing such matching processing in step S105 described above, the sum of the number of mounted bits of each subcarrier (corresponding to the area of the bit map) substantially matches between the theoretical calculation and the actual measurement. Therefore, by performing this matching process, the transmission speeds are almost the same. This completes the speed adjustment under the background noise.
[0185]
(Adjust crosstalk attenuation and noise margin)
Next, when the bitmap in the theoretical calculation and the bitmap in the actual measurement under the ADSL crosstalk environment are specifically as shown in FIG. 31, in step S109, a significant difference is found between the theoretical calculation and the actual measurement. It is determined that it can be done. The determination method here is the same as the determination method in step S103 described above, and thus description will not be repeated. When it is determined that a significant difference is found, the fitting is performed using the fitting parameters in step S111 described above.
[0186]
Generally, when crosstalk exists, transmission conditions are worse than in the case where background noise exists, and thus the number of mounted bits is low. Further, in a high frequency band (a band having a large tone number), transmission conditions are further deteriorated, so that it may not be possible to mount bits up to the maximum tone number.
[0187]
Specifically, referring to FIG. 31, the bitmap in the theoretical calculation and the bitmap in the actual measurement are compared, and the number of mounted bits in the actual measurement is 1% of the total number of mounted bits in the theoretical calculation. Bit low. It is known that far-end crosstalk is dominant in crosstalk interference of the ADSL transmission system with respect to the ADSL transmission system. From these facts, FPSL (far-end crosstalk attenuation characteristic) is a parameter used for the strength of far-end crosstalk, which determines the magnitude of the far-end crosstalk attenuation, which is a parameter for adjusting the relative strength of far-end crosstalk ) Is reduced by 3 dB (crosstalk is increased), that is, the bitmap is recalculated with FPSL = 42.0 dB. Further, the value of the noise margin may be changed as needed. The noise margin in the ADSL transmission system is usually 4 dB in both the up direction and the down direction, but by adjusting this noise margin, the number of mounted bits of all carriers can be uniformly fitted.
[0188]
FIG. 32 shows a bitmap obtained by the theoretical calculation and a bitmap obtained by the actual measurement after the FPSL and the noise merge are combined.
[0189]
By performing such matching processing in step S111 described above, the sum of the number of mounted bits of each subcarrier (corresponding to the area of the bit map) substantially matches between the theoretical calculation and the actual measurement. Therefore, by performing this matching process, the transmission speeds are almost the same. This completes the speed adjustment under the background noise.
[0190]
Note that the Annex C method of the ADSL transmission method prepares two types of bitmaps, a NEXT bitmap and a FEXT bitmap, so that a high transmission rate can be maintained even under ISDN interference. It is considered that the alignment accuracy is further improved by adjusting the two types of bitmaps.
[0191]
Note that the method of the fitting processing in steps S105 and S111 is not limited to the above-described method, and another method may be used. For example, the number of bits that can be mounted can be adjusted using bits or tones that are parameters for adjusting to the actually measured bitmap.
[0192]
Using the parameters adjusted in this way, it is possible to perform transmission performance estimation under different crosstalk sources, transmission performance estimation under different cable environments, and transmission performance estimation of different transmission systems.
[0193]
Therefore, hereinafter, three specific examples of the above estimation will be described for the case where the downlink transmission performance on the 0.4 mm diameter CCP cable of ADSL (G992.2) under the ISDN crosstalk environment is combined.
[0194]
(Estimation of transmission performance under different interference sources)
For example, it is possible to estimate the downstream transmission performance on a 0.4 mm diameter CCP cable of ADSL (G992.2) under an SDSL crosstalk environment. In this case, the spectrum of the crosstalk source may be changed to that of SDSL for calculation.
[0195]
(Estimation of transmission performance on different cables)
It is possible to estimate the downstream transmission performance of ADSL (G992.2) on a 0.5 mm diameter CCP cable under ISDN interference. In this case, the calculation may be performed by changing the cable parameters to those of the 0.5 mm diameter CCP cable.
[0196]
(Estimation of transmission performance of different transmission systems)
For example, it is possible to estimate the downlink transmission performance on an ADSL (G992.1) 0.4 mm diameter CCP cable under an ISDN crosstalk environment. The G992.1 system differs from the G992.2 system in the noise margin and the maximum tone number as shown in FIG. Since the noise margin of the G992.1 system is higher than that of the G992.2 system by 2 dB, a value obtained by adding 2 dB to the combined value of the G992.2 system is used. Also, since the maximum tone number is 128 higher in the G992.1 system than in the G992.2 system, a value obtained by adding 128 to the value obtained by combining the G992.2 system is used. In this way, it is possible to estimate the speed of the downlink of the G992.1 system.
[0197]
Further, in the case of ISDN (baseband system), similarly to ADSL (multicarrier system), transmission performance estimation under different crosstalk sources, transmission performance estimation under different cable environments, It is also possible to estimate the transmission performance of different transmission systems.
[0198]
Therefore, hereinafter, three specific examples of the above estimation will be described in the case where the downlink transmission performance on the ISDN 0.4 mm diameter CCP cable under the ADSL crosstalk environment is combined.
[0199]
(Estimation of transmission performance under different interference sources)
For example, it is possible to estimate the downlink transmission performance on an ISDN 0.4 mm diameter CCP cable in an SDSL crosstalk environment. In this case, the spectrum of the crosstalk source may be changed to that of SDSL for calculation.
[0200]
(Estimation of transmission performance on different cables)
It is possible to estimate the downlink transmission performance on a 0.5 mm diameter CCP cable of ISDN under ADSL interference. In this case, the calculation may be performed by changing the cable parameters to those of the 0.5 mm diameter CCP cable.
[0201]
(Estimation of transmission performance of different transmission systems)
At present, there is no other DSL system capable of calculating the same transmission performance as ISDN, but when a new system is developed in the future, if this is a transmission system similar to ISDN, the transmission performance of that transmission system An estimate can be made. For example, when the transmission spectrum of the ISDN is changed, it is possible to estimate the transmission performance by performing the calculation while replacing the spectrum.
[0202]
Further, the adjustment of the ISDN will be described more specifically below.
FIG. 33 is a flowchart showing a specific example of the fitting process when estimating the speed performance of the ISDN. In the following processing example, it is specifically assumed that there are two types of conditions that can be actually measured: a background noise environment and an ADSL crosstalk environment. Under these two conditions, the maximum distance that the ISDN can transmit is obtained by theoretical calculation and actual measurement. That is, in the theoretical calculation, the maximum distance which can secure SNR = 26.46 dB (threshold) is obtained, and in the actual measurement, the maximum distance (ISDN reachable distance) to which the IDSN is actually connected is measured.
[0203]
Referring to FIG. 33, first, in step S201, a theoretical value and a measured value of a maximum transmittable distance in the ISDN transmission method under a background noise environment are obtained.
[0204]
Next, when a significant difference is found between the calculated theoretical value and the measured value of the maximum transmittable distance (YES in S203), the background noise intensity is adjusted in step S205. The matching process in step S205 will be described later.
[0205]
Next, in step S207, a theoretical value and a measured value of the maximum transmittable distance in the ISDN transmission method under the ADSL crosstalk environment are obtained. At this time, if the matching is performed in step S205 described above, the theoretical value of the maximum transmittable distance in the ISDN transmission system under the ADSL crosstalk environment is obtained using the matched background noise intensity.
[0206]
Next, when a significant difference is found between the calculated theoretical value and the measured value of the maximum transmittable distance (YES in S209), the crosstalk attenuation is adjusted in step S211.
[0207]
As described above, the fitting process is completed, and by using the value adjusted in this way, it is possible to perform speed estimation under conditions that cannot be measured.
[0208]
The fitting process in steps S205 and S211 of the above-described fitting process will be described with a specific example.
[0209]
(Adjustment of background noise intensity)
If the theoretical calculation value of the maximum distance that the ISDN can transmit in the theoretical calculation under the background noise environment is specifically 6.5 km and the actual measurement value is 5.5 km, in step S203, the theoretical calculation and the actual measurement are performed. It is determined that a significant difference is seen between and. The parameters used for the simulation calculation here are:
NPSL (Near-end crosstalk characteristic value) = 47.0 dB
FPSL (far end crosstalk characteristic value) = 45.0 dB
Background noise = -140 dBm / Hz
It is. The method of determining whether there is a significant deviation here is not limited in the present invention, but specifically, there is a difference between the theoretical value and the measured value that is equal to or greater than the threshold value. The determination may be made by detecting that the operation is performed. Also, the determination may be made by another method. When it is determined that such a significant difference is found, adjustment is performed in a background noise environment in step S205 described above.
[0210]
In the case of the above specific example, since the maximum reachable distance of the ISDN in the actual measurement is smaller than the theoretical value, it is estimated that the background noise of the actual measurement is higher than the background noise (-140 dBm / Hz) assumed in the theoretical calculation, The background noise is set higher than the assumed background noise and recalculated.
[0211]
The method of resetting the background noise here includes the following method. That is, since the maximum reachable distance in the actual measurement is 5.5 km, it can be estimated that the SNR near 5.5 km is about the threshold value (26.46 dB). On the other hand, when the SNR near 5.5 km was calculated in the theoretical calculation, it was 43 dB. From this, it is estimated that the background noise of the actual measurement is about 16.5 dB higher than the background noise in the theoretical calculation, and the background noise intensity in the theoretical calculation is re-increased from -140 dBm / Hz to -124 dBm / Hz, which is higher by about 16.5 dB. Set and recalculate maximum reach. Then, it is determined again whether a significant difference is found between the theoretical value and the actually measured value. By repeating this processing, the background noise can be estimated, and the background noise in the theoretical calculation can be matched with the actually measured background noise.
[0212]
(Adjust crosstalk attenuation)
Next, the crosstalk in the theoretical calculation is calculated using the maximum transmittable distance in the theoretical calculation under the ADSL crosstalk environment calculated using the background noise reset above and the maximum transmittable distance in the actual measurement. Adjust the attenuation.
[0213]
In the above example, since the background noise has been reset to -124 dBm / Hz, the maximum range of the ISDN is recalculated using the value. As a result, when the maximum reach distance is 3.25 km and the actual measurement value is 3.75 km, it is determined in step S209 that a significant difference is found between the theoretical calculation and the actual measurement.
[0214]
In the case of the above specific example, since the maximum reachable distance of the ISDN in the actual measurement is larger than the theoretical value, it is estimated that the crosstalk characteristic in the actual measurement is smaller than the crosstalk characteristic assumed in the theoretical calculation, and the crosstalk characteristic (NPSL, FPSL) is changed, reset, and recalculated.
[0215]
The method of resetting the crosstalk characteristic here includes a method similar to the processing in step S205 described above. That is, since the maximum reachable distance in actual measurement is 3.75 km, it can be estimated that the SNR near 3.75 km is about the threshold value (26.46 dB). On the other hand, when the SNR near 3.75 km was calculated in the theoretical calculation, it was 21.1 dB. From this, it is estimated that the measured crosstalk attenuation is about 5 dB larger (the crosstalk is smaller) than the crosstalk attenuation assumed in the theoretical calculation. It is known that near-end crosstalk is dominant in crosstalk interference of the ADSL transmission system with respect to the ISDN transmission system. Therefore, the near-end crosstalk attenuation in the theoretical calculation is changed, that is, the NPSL is reset to a large value, and the maximum reach is calculated again. Then, it is determined again whether a significant difference is found between the theoretical value and the actually measured value. By repeating this process, the NPSL can be estimated, and the crosstalk attenuation in the theoretical calculation can be matched with the actually measured crosstalk attenuation. In the above specific example, when the NPSL was reset to 53.0 dB, which is larger by 6 dB, the maximum reach was recalculated to be 3.75 km, which was in agreement with the actually measured value.
[0216]
By performing such matching processing in steps S205 and S211, the background noise and the crosstalk attenuation (near-end crosstalk characteristics and far-end crosstalk characteristics) are almost the same between the theoretical calculation and the actual measurement.
[0217]
As described above, by using the simulation program according to the present embodiment, it is only necessary to change the setting parameters on the program to values that match the characteristics of the actual device, and to improve the performance of the actual device under conditions that are difficult to measure. It can be estimated with accuracy.
[0218]
Further, in the simulation program according to the present embodiment, it is also possible to estimate the performance of a real device that is being developed or is to be developed by using a setting parameter value of a conventional real device.
[0219]
Furthermore, the above-described simulation program can be recorded on a computer-readable recording medium such as a flexible disk, a CD-ROM, a ROM, a RAM, and a memory card attached to a computer, and can be provided as a program product. Alternatively, the program can be provided by being recorded on a recording medium such as a hard disk incorporated in the computer. Further, the program can be provided by downloading via a network.
[0220]
The provided program product is installed and executed in a program storage unit such as a hard disk.
[0221]
Note that the program product includes the program itself and a recording medium on which the program is recorded.
[0222]
The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[Brief description of the drawings]
FIG. 1 is a diagram showing a specific example of a line model.
FIG. 2 is a diagram showing a specific example of a simulation method in the present simulation program.
FIG. 3 shows a symbol rate f_symFIG.
FIG. 4 is a diagram illustrating near-end crosstalk and far-end crosstalk.
FIG. 5 is a diagram showing transmission line attenuation constants for transmission lines of four types of materials and diameters.
FIG. 6 is a diagram showing parameters in a table format when evaluating the transmission characteristics of ADSL.
FIG. 7 is a table showing parameters in a table format when evaluating the transmission characteristics of SSDL;
FIG. 8 is a diagram illustrating characteristics of each transmission scheme.
FIG. 9 is a diagram showing a transmission signal PSD on the crosstalk side when TCM-AMI ISDN (Japan) is a crosstalk source and a transmission signal PSD on the crosstalk side when 2B1Q ISDN (USA) is a crosstalk source. .
FIG. 992.1 (ADSL G.dmt) shows a crosstalk-side transmission signal PSD when the downstream direction of AnnexA / AnnexC-DBM is a crosstalk source, and a crosstalk-side transmission signal PSD when the upstream direction is a crosstalk source. FIG.
FIG. 992.2 (ADSL G.lite) shows a transmission signal PSD on the crosstalk side when the downstream direction of AnnexA / AnnexC-DBM is a crosstalk source, and a transmission signal PSD on the crosstalk side when the upstream direction is a crosstalk source. FIG.
FIG. 991.1 (HDSL) When the AnnexA (2B1Q) is the crosstalk source and when the SDSL (2B1Q) is the crosstalk source, the data transmission speed in the SDSL (2B1Q) is 784 (kbps), 1552 (kbps), FIG. 13 is a diagram showing a transmission signal PSD on the crosstalk side when the transmission signal is 2320 (kbps).
FIG. 13 is a diagram showing, in a graph form, the average power of the transmission signal PSD on the crosstalk side when the HDSL (CAP) is the crosstalk source.
FIG. 14 is a diagram showing, in a table form, a transmission signal PSD average power on the crosstalk side when HDSL (CAP) is a crosstalk source.
FIG. 991.2 (SHDSL, PAM) Annex A Asymmetric PSD A diagram showing a PSD mask in the form of a graph when a 1.5 Mbps downlink direction is a crosstalk source.
FIG. 991.2 (SHDSL, PAM) Annex A Asymmetric PSD is a diagram showing a PSD mask in a table format in a case where a 1.5 Mbps downlink direction becomes a crosstalk source.
FIG. 991.2 (SHDSL, PAM) AnnexA Asymmetric PSD is a diagram showing a PSD mask in the form of a graph when a 1.5 Mbps upstream direction becomes a crosstalk source.
FIG. 991.2 (SHDSL, PAM) AnnexA Asymmetric PSD is a diagram showing a PSD mask in the form of a table when a 1.5 Mbps upstream direction becomes a crosstalk source.
FIG. It is a figure which shows the parameter at the time of calculating the transmission signal PSD of the crosstalk side when the transmission system of 991.2 (SHDSL, PAM) AnnexA Symmetric PSD becomes a crosstalk source.
FIG. 20 shows a transmission signal PSD on the crosstalk side when the data transmission speed is 1536 (kbps), 768 (kbps), and 384 (kbps) in the case where the transmission scheme of the SHDSL (symmetric PSD) is a crosstalk source. FIG.
FIG. 21 is a diagram illustrating a specific example of a part of a worksheet of a simulation program for evaluating transmission characteristics of ISDN.
FIG. 22 is a diagram showing, in a list form, attenuation characteristics of a transmission line used in a simulation program.
FIG. 23 is a diagram showing a specific example of a worksheet for outputting transmission signals PSD of all transmission schemes calculated during execution of the simulation program and PSDs due to near-end crosstalk.
FIG. 24 is a diagram showing a specific example of a part of a worksheet of a simulation program for evaluating the transmission characteristics of ADSL.
FIG. 25 is a diagram showing a specific example of a part of a worksheet of a simulation program for evaluating the transmission characteristics of ADSL.
FIG. 26 is a diagram illustrating a technique for estimating a performance value in consideration of a carrier used in each transmission scheme used by the simulation program.
FIG. 27 is a flowchart illustrating a specific example of a fitting process when estimating the speed performance of ADSL.
FIG. 28 is a diagram showing a specific example of a bitmap in theoretical calculation and a bitmap in actual measurement under a background noise environment.
FIG. 29 is a diagram showing a specific example of a bitmap in theoretical calculation and a bitmap in actual measurement after matching of maximum and minimum tone numbers.
FIG. 30 is a diagram showing a specific example of a bitmap in theoretical calculation and a bitmap in actual measurement after background noise intensity adjustment.
FIG. 31 is a diagram showing a specific example of a bitmap in theoretical calculation and a bitmap in actual measurement under an ADSL crosstalk environment.
FIG. 32 is a diagram showing a specific example of a bitmap in theoretical calculation and a bitmap in actual measurement after performing FPSL and noise merging.
FIG. 33 is a flowchart showing a specific example of fitting processing when estimating speed performance of ISDN.

Claims (17)

A transmission performance simulation program for calculating transmission performance in a transmission system using a metallic cable,
Frequency spectrum characteristics of the transmission spectrum, the amount of crosstalk attenuation, the receiving step of receiving a set value for the transmission system including the transmission line length,
A first calculating step of calculating a power spectrum density of a received signal of the transmission system using the received set value;
A second calculation step of calculating an interference noise intensity of another transmission system existing on a line different from the line of the transmission system using the received set value;
A third calculating step of calculating a relationship between the transmission line length and a signal power-to-noise power ratio or a transmission speed of the received signal using the calculated power spectrum density and the calculated noise intensity; ,
A transmission performance simulation program for causing a computer to execute an output step of outputting the calculated result. In the receiving step, a setting regarding the other transmission system is further received,
In the first calculating step, the power of the received signal of the transmission system under the interference of the other transmission system is determined by using the setting value of the received transmission system and the setting of the received other transmission system. The transmission performance simulation program according to claim 1, which calculates a spectrum density. The computer further executes a determination step of determining the spectral compatibility between the transmission system and the other transmission system by comparing the calculation result in the first calculation step with a preset threshold value. The transmission performance simulation program according to claim 1 or 2. In the receiving step, receiving a set value of a plurality of types of the transmission system,
In the first calculation step, using the set values of the plurality of types of transmission systems received in the reception step, interference with a predetermined other transmission system existing on a line different from a line of the transmission system is used. Calculate the power spectrum density of the received signal for each of the plurality of types of transmission systems at,
In the third calculation step, using the calculated power spectrum density for each of the transmission systems and the calculated noise intensity, the reception of the transmission line length and the plurality of types of transmission systems is performed. Calculating the relationship between the signal power to noise power ratio or the transmission rate of the signal,
The transmission performance according to any one of claims 1 to 3, further comprising causing a computer to execute a comparison step of comparing the performances of the plurality of types of transmission systems using the calculation results of the plurality of types of transmission systems. Simulation program. When there is a predetermined difference between the calculated result and the actual measurement value, in order to match the calculated result with the actual measurement value, the setting value for the transmission system received in the receiving step is adjusted. The transmission performance simulation program according to any one of claims 1 to 4, further causing the computer to execute the embedding step. A result obtained by causing a computer to execute the first calculation step, the second calculation step, and the third calculation step using the adjusted set value is different from that of the transmission system. 6. The transmission performance simulation program according to claim 5, wherein the transmission performance simulation program estimates that the result is a calculation result for the second transmission system. In the case where the transmission system is a transmission system using a multicarrier transmission scheme, the calculated result is on-board bit information, and a setting value for the transmission system performing the matching is a background noise intensity and a maximum value. The transmission performance simulation program according to claim 5, wherein the transmission performance simulation program is at least one of a tone number, a minimum tone number, a crosstalk attenuation amount, and a noise margin. In a case where the transmission system is a transmission system using a single carrier transmission system or a baseband transmission system, the calculated result is maximum distance information that can be transmitted in the transmission system, and the transmission for performing the adjustment is performed. 7. The transmission performance simulation program according to claim 5, wherein the set value of the system is at least one of background noise intensity and crosstalk attenuation. A transmission performance simulation method for calculating transmission performance in a transmission system using a metallic cable,
Frequency spectrum characteristics of the transmission spectrum, the amount of crosstalk attenuation, the receiving step of receiving a set value for the transmission system including the transmission line length,
A first calculating step of calculating a power spectrum density of a received signal of the transmission system using the received set value;
A second calculation step of calculating an interference noise intensity of another transmission system existing on a line different from the line of the transmission system using the received set value;
A third calculating step of calculating a relationship between the transmission line length and a signal power-to-noise power ratio or a transmission speed of the received signal using the calculated power spectrum density and the calculated noise intensity; ,
An output step of outputting the calculated result. In the receiving step, a setting regarding the other transmission system is further received,
In the first calculating step, the power of the received signal of the transmission system under the interference of the other transmission system is determined by using the setting value of the received transmission system and the setting of the received other transmission system. The transmission performance simulation method according to claim 9, wherein a spectrum density is calculated. The method according to claim 1, further comprising: determining a spectrum compatibility between the transmission system and the other transmission system by comparing a calculation result in the first calculation step with a preset threshold value. The transmission performance simulation method according to 9 or 10. In the receiving step, receiving a set value of a plurality of types of the transmission system,
In the first calculation step, using the set values of the plurality of types of transmission systems received in the reception step, interference with a predetermined other transmission system existing on a line different from a line of the transmission system is used. Calculate the power spectrum density of the received signal for each of the plurality of types of transmission systems at,
In the third calculation step, using the calculated power spectrum density for each of the transmission systems and the calculated noise intensity, the reception of the transmission line length and the plurality of types of transmission systems is performed. Calculating the relationship between the signal power to noise power ratio or the transmission rate of the signal,
The transmission performance simulation method according to any one of claims 9 to 11, further comprising a comparing step of comparing the performances of the plurality of types of transmission systems using the calculation results of the plurality of types of transmission systems. When there is a predetermined difference between the calculated result and the actual measurement value, in order to match the calculated result with the actual measurement value, the setting value for the transmission system received in the receiving step is adjusted. The transmission performance simulation method according to claim 9, further comprising an embedding step. Using the adjusted set value, a result obtained by executing the first calculation step, the second calculation step, and the third calculation step is different from the result obtained by the transmission system. 13. The transmission performance simulation method according to claim 9, wherein the transmission performance is estimated to be a calculation result for the second transmission system. In the case where the transmission system is a transmission system using a multicarrier transmission scheme, the calculated result is on-board bit information, and a setting value for the transmission system performing the matching is a background noise intensity and a maximum value. The transmission performance simulation method according to claim 13 or 14, wherein the transmission performance is at least one of a tone number, a minimum tone number, a crosstalk attenuation amount, and a noise margin. In a case where the transmission system is a transmission system using a single carrier transmission system or a baseband transmission system, the calculated result is maximum distance information that can be transmitted in the transmission system, and the transmission for performing the adjustment is performed. 15. The transmission performance simulation method according to claim 13, wherein the set value of the system is at least one of background noise intensity and crosstalk attenuation. A computer-readable recording medium storing the transmission performance simulation program according to claim 1.

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