JP6275177B2 - Master station communication device, communication method, and network system - Google Patents

Description

  The present invention relates to a master station communication device, a communication method, and a network system, and can be applied to, for example, communication using an orthogonal frequency multiplexing (OFDM) in which transmission capacity is expanded and contracted (OFDM: Orthogonal Frequency Multiple Division Multiplexing).

  The orthogonal frequency division multiplexing (OFDM) system is a communication system that is practically used in wireless communication. Currently, an optical OFDM system in which the carrier frequency is increased to the optical frequency is actively studied in the optical communication field. In addition, research on networks that efficiently use bandwidth resources by dynamically changing the signal parameters (number of subcarriers, number of modulation multi-levels, etc.) of this optical OFDM signal according to the network conditions has been conducted in recent years. ing. Hereinafter, such a communication scheme is referred to as a “dynamic variable optical OFDM scheme”.

  Conventionally, there is a system described in Patent Document 1 in which a dynamic variable optical OFDM method is applied to a data transmission method in a one-to-many optical network (a so-called PON (Passive Optical Network) type network). . In the PON type network, one accommodating station side device (OLT (Optical Line Terminal); master station communication device) and a plurality of subscriber side devices (ONU (Optical Network Unit); slave station communication device) are branched. The configuration is such that the optical fibers are connected (configuration of one-to-many optical network). The OLT is connected to a higher-level network. Each ONU is connected to a user side network (user terminal).

  Next, a configuration outline of a network (one-to-many optical network) to which a conventional OFDM scheme is applied will be described.

  The network described in Patent Document 1 includes one OLT (station side device), a plurality of ONUs (subscriber side devices), and an optical multiplexer / demultiplexer that optically connects these devices. In the network described in Patent Document 1, ONUs having the same number of modulation levels used for communication are grouped. Hereinafter, this ONU group is referred to as an “ONU group” or simply a “group”. As an example of ONU grouping, in Patent Document 1, grouping according to the distance between OLT and ONU is cited.

  Next, an optical OFDM signal transmitted and received in a network (PON type network) to which a conventional dynamic variable optical OFDM system is applied will be described with reference to FIG.

  OFDM transmission is a method in which a plurality of subcarriers (subcarriers) are independently modulated and data signals are superimposed and transmitted. Subcarriers are modulated periodically. In a network to which a conventional dynamic variable optical OFDM scheme is applied, subcarriers are distributed for each ONU group.

Hereinafter, this modulated subcarrier is referred to as an “OFDM symbol”, and the modulation period is referred to as an “OFDM symbol period”. In the following description, the total number of subcarriers arranged at equal intervals (called subcarrier intervals) on the frequency axis is N [SC]. Further, in the following description, identification numbers (any integer of 1 to N) are attached to these subcarriers. Furthermore, in the following description, the total number of ONU groups on the network is k, and each ONU group is assigned an identification number (any integer from 1 to k). In the following description, the modulation multilevel number of subcarriers assigned to ONU group i (i is an integer of 1 to k) (that is, the number of information bits that can be transmitted per OFDM symbol per subcarrier) is represented by A _i [bit / symbol. / SC]. Further, hereinafter, the number of subcarriers assigned to ONU group i is represented as N _i [SC].

In FIG. 9, each square (cell) represents one OFDM symbol of an optical OFDM signal and one subcarrier, and a value described in each square represents a multi-value number for modulating the subcarrier. Then, in a network to which a conventional dynamic variable optical OFDM scheme is applied, if the OFDM symbol period is T _s [s], the transmission bit rate of the optical OFDM signal in the network can be calculated by the following equation (1).

In a network to which a conventional dynamic variable optical OFDM scheme is applied, the multi-value number A _i is selected according to the distance between the OLT and the ONU, and the number of subcarriers N _i is changed according to the amount of traffic at that time. Thus, it is possible to provide a bandwidth that matches the communication demand. 9, which is an example of changing the value of N _i at time T _1.

  The ONU (that is, the receiving side) can restore the original signal by demodulating the subcarriers belonging to its own ONU group with the same multilevel number as that of the transmitting side (OLT).

JP 2014-120788 A

By the way, in the network to which the dynamic variable optical OFDM system is applied, the transmission bit rate of the optical OFDM signal is expressed by the multi-value number A _i and the number of subcarriers N _i of the ONU group i as shown in the above equation (1). It changes when you change. On the other hand, in a conventional ONU or OLT, a packet is connected to an interface (hereinafter referred to as an “optical transceiver”) that transmits and receives an optical OFDM signal by connecting to an optical fiber and various media (for example, a LAN cable). In many cases, the transmission bit rate of a signal flowing through an interface with a transmission / reception interface (hereinafter referred to as “media access processing unit”) is constant. Therefore, in an OLT or ONU that constitutes a network (one-to-many network) to which a conventional dynamic variable optical OFDM scheme is applied, the transmission bit rate on the optical transceiver side (transmission bit rate of the optical OFDM signal) and media access When the transmission bit rate on the processing unit side is different, there is a possibility that a problem occurs in communication.

  For example, in the conventional OLT, when the transmission bit rate of the downstream signal from the media access processing unit to the optical transceiver is larger than the transmission bit rate of the optical transceiver (the transmission bit rate of the optical OFDM signal), The transmission signal may overflow and data may be lost. However, the conventional OLT and ONU have not yet disclosed an interface that absorbs this difference in transmission bit rate.

Further, in the network to which the dynamic variable optical OFDM system is applied as described above, it is possible to provide a band that matches the communication demand by changing the number of subcarriers N _i of the ONU group i. Further, in the conventional network, when the number of subcarriers in one ONU group is changed, the number of subcarriers in another ONU group is often changed at the same time. This is because the total number N of subcarriers in an optical OFDM signal is constant, and therefore, for example, if the number of subcarriers in a certain ONU group is increased, the number of subcarriers in another ONU group must be decreased. Therefore, in a network to which the dynamically variable optical OFDM scheme is applied, it is desired that the number of subcarriers be changed in synchronization with the entire network system.

  In the network to which the dynamic variable optical OFDM system is applied as described above, each subcarrier transmits independent information at the same time. That is, a parallel transmission scheme in which each subcarrier behaves like an independent transmission path is obtained. Therefore, in a network to which the dynamic variable optical OFDM method is applied as described above, when a plurality of packet data is transmitted on different transmission paths (that is, subcarriers), the transmission side depends on the degree of congestion of the transmission paths and the throughput. It is possible that the arrival order of packets is reversed on the receiving side. In a conventional network, there is a service (for example, a stream video distribution service) whose quality is likely to be deteriorated due to the order reversal. Therefore, it is desirable that the packet order not be reversed.

  In view of the above problems, a master station communication apparatus, communication method, and network system capable of performing traffic control flexibly and stably in a network to which a dynamically variable optical OFDM (Orthogonal Frequency Multiplexing) system is applied Is desired.

A first aspect of the present invention is a master station communication device connected to a plurality of slave station communication devices via branched optical fibers, wherein (1) a receiving unit that receives downlink data; and (2) the receiving unit A data distribution processing unit that distributes the data received in step 1 for each group related to the slave station communication device, (3) a storage unit that temporarily stores the data distributed by the data distribution processing unit, and (4) the data distribution A control unit that instructs the processing unit to distribute the received data, and that instructs the read timing of the divided data temporarily stored in the storage unit; and (5) multivalued data read from the storage unit possess a multi-level modulator modulating the number, and (6) a signal modulated by the M-ary modulation section, a conversion unit for converting the OFDM signal to the slave station communication apparatus side, (7) the Data distribution process Distributes the data received by the receiving unit for each group related to the slave station communication device, divides the allocated data into a predetermined division size for each group, acquires divided data, and (8) stores the data The unit temporarily stores the divided data acquired by the data distribution processing unit, (9) the control unit instructs the data distribution processing unit to distribute the received data and the predetermined size, The read timing of the divided data temporarily stored in the storage unit is instructed .

According to a second aspect of the present invention, there is provided a communication method performed by a master station communication device connected to a plurality of slave station communication devices via branched optical fibers. (1) The master station communication device includes a receiver, a data distribution process A storage unit, a control unit, a multi-level modulation unit, and a conversion unit, (2) the reception unit receives downlink data, and (3) the data distribution processing unit is the reception unit The received data is distributed for each group related to the slave station communication device, (4) the storage unit temporarily stores the data distributed by the data distribution processing unit, and (5) the control unit stores the data The distribution processing unit is instructed to distribute the received data, and the read timing of the divided data temporarily stored in the storage unit is instructed. (6) The multi-level modulation unit is read from the storage unit Data with multiple values , (7) the conversion unit, said signal modulated by M-ary modulation section converts the OFDM signal and outputs it to the slave station communication apparatus side (8) the data distribution processor is received by the receiving unit And the divided data is divided into a predetermined division size for each group to obtain divided data, and (9) the storage unit performs the data distribution process. (10) The control unit instructs the data distribution processing unit to distribute the received data and the predetermined size, and temporarily stores the divided data in the storage unit. It is characterized by instructing the read timing of the divided data .

  According to a third aspect of the present invention, there is provided a network system including a plurality of slave station communication devices and a master station communication device connected to each slave station communication device by a branched optical fiber. The master station communication device according to the first aspect of the present invention is applied as the station communication device.

  According to the present invention, traffic control can be performed flexibly and stably in a network to which a dynamic variable optical OFDM (Orthogonal Frequency Multiplexing) scheme is applied.

It is the block diagram shown about the functional structure of OLT which concerns on 1st Embodiment. 1 is a block diagram illustrating an overall configuration of a network system according to a first embodiment. It is the block diagram shown about the functional structure of ONU which concerns on 1st Embodiment. It is explanatory drawing shown about the structure of the optical OFDM signal of the downlink direction produced | generated by OLT based on 1st Embodiment. It is the block diagram shown about the functional structure of OLT which concerns on 2nd Embodiment. It is the block diagram shown about the functional structure of OLT which concerns on 3rd Embodiment. It is explanatory drawing shown about the structure of the serial signal output from the media access process part (parallel serial converter) of OLT which concerns on 2nd Embodiment. It is explanatory drawing shown about the structure of the serial signal output from the media access process part (parallel serial converter) of OLT which concerns on 3rd Embodiment. It is explanatory drawing shown about the structure of the optical OFDM signal of the downlink direction produced | generated by the conventional OLT.

(A) First Embodiment Hereinafter, a first embodiment of a master station communication device, a communication method, and a network system according to the present invention will be described in detail with reference to the drawings. Below, the example which applied the parent station communication apparatus of this invention to OLT is demonstrated.

(A-1) Configuration of the First Embodiment FIG. 2 is a block diagram showing the overall configuration of the network system 100 of this embodiment. Note that the reference numerals in parentheses in FIG. 2 are the reference numerals used in second and third embodiments described later.

  The network system 100 has a configuration of a one-to-many optical network (so-called PON type network) to which the dynamic variable optical OFDM method is applied.

  In the network system 100, one OLT 2 and a plurality of ONUs 5 are arranged.

  An optical fiber F is connected (optically connected) to the OLT 2, and the optical fiber F is branched by the optical multiplexer / demultiplexer 3 and connected to each ONU 5.

It is assumed that the ONUs 5 arranged in the network system 100 are managed by being divided into k ONU groups 4 (4-1 to 4-k). The identification numbers of the ONU groups 1 to k shown in FIG. Further, it is assumed that m _{1 to} m _k ONUs 5 are arranged in the ONU groups 1 to _k , respectively.

  Note that FIG. 2 illustrates a configuration related to a downlink communication scheme (communication from the upper network 1 to each user terminal), and does not illustrate a configuration related to uplink communication. In the network system 100, various configurations can be applied to configurations related to uplink communication, and detailed description thereof will be omitted.

  The OLT 2 is connected to the upper network 1 and the optical fiber F. Each ONU 5 is connected to the optical fiber F branched by the optical multiplexer / demultiplexer 3 and the user terminal 6 constituting the lower network. The network configuration on the lower side of each ONU 5 is not limited, and various network configurations can be applied. In FIG. 2, each ONU 5 is illustrated as a configuration in which each ONU 5 is directly connected to the user terminal 6 for simplicity of illustration, but in actuality, it is connected via various network configurations such as switches and routers (wireless access points). (It is not limited whether it is wired or wireless). Further, the configuration of the upper network 1 to which the OLT 2 is connected is not limited, and various network configurations can be applied.

  As described above, the network system 100 configured by the OLT 2 and each ONU 5 is configured to relay communication between the user terminal 6 (lower network) of each ONU 5 and the upper network 1.

  The OLT 2 is a medium connected to the upper network 1 using an OFDM optical receiver 21 as an interface for connecting to the optical fiber F and transmitting / receiving an optical OFDM signal, and an arbitrary medium (for example, Ethernet (registered trademark) interface). And an access processing unit 20.

  The downlink data signal supplied from the upper network 1 to the OLT 2 is converted into an optical OFDM signal via the media access processing unit 20 and the OFDM optical receiver 21 inside the OLT 2 and output to the optical fiber F. The media access processing unit 20 classifies packet-like downlink data signals for each destination, and performs transmission / reception control of the entire network system 100 (transmission / reception control with each ONU 5). The OFDM optical receiver 21 also has a function of modulating an OFDM signal subcarrier according to the information bit string sent from the media access processing unit 20 to generate an optical OFDM signal.

  For the downstream signal, the optical multiplexer / demultiplexer 3 demultiplexes the optical OFDM signal transmitted from the OLT 2 to each ONU 5. Further, the optical multiplexer / demultiplexer 3 multiplexes the optical OFDM signals transmitted from the respective ONUs 5 and supplies them to the OLT 2 side.

  Each ONU 5 is connected to the optical fiber F branched by the optical multiplexer / demultiplexer 3 and uses an OFDM optical receiver 50 as an interface for transmitting and receiving an optical OFDM signal, and an arbitrary medium (for example, Ethernet interface). A media access processing unit 51 connected to the user terminal 6 (lower network) is included.

  The optical OFDM signal (downlink signal) input from the optical fiber F to the ONU 5 is converted into the original downlink data signal via the OFDM optical receiver 50 and the media access processing unit 51 inside the ONU 5. The OFDM optical receiver 50 has a function of demodulating an optical OFDM signal and restoring an information bit string. Further, the media access processing unit 51 extracts a signal addressed to itself from the signal transmitted from the OFDM optical receiver 50, reconstructs the original packet-like downlink data signal, and the user terminal 6 (lower network side). It also has a function to send to the. The media access processing unit 51 also has a function of controlling processing operations inside the ONU 5 in response to an instruction from the media access processing unit 20 of the OLT 2.

  Next, a detailed configuration inside the OLT 2 will be described with reference to FIG.

  In FIG. 1, a configuration related to a downlink communication scheme (communication from the upper network 1 to each user terminal) is illustrated, and a configuration related to uplink communication is not shown. In the OLT 2, the same configuration as that of various OLTs can be applied to the configuration for processing the upstream signal.

  As described above, the OLT 2 includes the OFDM optical receiver 21 and the media access processing unit 20.

  The media access processing unit 20 includes a control unit 22, a data distribution processing unit 23, and N memories 24 (24-1 to 24-N). The OFDM optical receiver 21 includes a multilevel modulator 27 (27-1 to 27-N) corresponding to each of the N memories 24 (24-1 to 24-N), and an IDFT (Inverse Discrete Fourier Transform). 28, a parallel-serial converter 29, and an electro-optical converter 30.

  The control unit 22 has a function of controlling each component in the OLT 2. The control unit 22 instructs each memory 24 to read data at a timing and a reading amount. In addition, the control unit 22 instructs the data distribution processing unit 23 on the method of distributing the input downlink data signal. Further, the control unit 22 instructs the OFDM optical receiver 21 of a multi-level number when performing multi-level modulation of each subcarrier. Furthermore, the control unit 22 notifies each ONU 5 of the number of subcarriers to be received and the number of modulation levels.

  The data distribution processing unit 23 has a function of dividing the downlink data signal input in accordance with an instruction from the control unit 22 and outputting the divided data signal to the memory 24. The data distribution processing unit 23 is functionally divided into a group distribution processing unit 31 and k subcarrier distribution processing units 32 (32-1 to 32-k). The group distribution processing unit 31 has a function of reading destination information included in a downlink data signal input in accordance with an instruction from the control unit 22, and distributing and outputting the downlink data signal for each ONU group. The subcarrier distribution processing unit 32-i (i is an integer from 1 to k) has a bit length (division size) designated by the control unit 22 from the head for the downlink data signal addressed to the ONU group i. It has a function to divide and distribute.

  Each of the memories 24-1 to 24-N temporarily stores signals input from the data distribution processing unit, and has a function of sequentially reading and outputting in accordance with instructions from the control unit.

Each of the multilevel modulators 27-1 to 27 -N has a function of modulating input data to a corresponding subcarrier. Specifically, the multi-level modulator 27-j (j is an integer from 1 to N) specifies the subcarrier j of the optical OFDM signal according to the input data, as the multi-level number A _i (specified from the control unit 22). Multi-valued). The correspondence between subcarriers and multi-level numbers will be described later.

  The IDFT 28 performs a discrete inverse Fourier transform, and has a function of converting a frequency domain input signal into a time domain output signal.

  The parallel-serial converter 29 has a function of converting the parallel time domain signal from the IDFT 28 into a serial signal (serial signal).

  The electro-optical converter 30 has a function of converting an electric signal from the parallel-serial converter 29 into an optical signal.

  Next, a detailed configuration inside the ONU 5 will be described with reference to FIG.

  In FIG. 3, a configuration related to a downlink communication scheme (communication from the upper network 1 to each user terminal) is illustrated, and a configuration related to uplink communication is not shown. In the ONU 5, the same configuration as various ONUs can be applied to the configuration for processing the upstream signal.

  As described above, the ONU 5 includes the OFDM optical receiver 50 and the media access processing unit 51.

  The OFDM optical receiver 50 includes an optical / electrical converter 52, a serial / parallel converter 53, a DFT 54, and N multilevel demodulators 55-1 to 55-N.

  The photoelectric converter 52 has a function of converting an optical OFDM signal into an electrical signal.

  The serial / parallel converter 53 has a function of converting a serial signal from the photoelectric converter 52 into a parallel signal.

  The DFT 54 has a function of performing a discrete Fourier transform on the time domain signal input from the serial / parallel converter 53 and outputting it as a frequency domain signal.

The multi-level demodulator 55-j (j is an integer from 1 to N) receives the sub-carrier j of the received optical OFDM signal, the multi-level number A _j specified from the control unit 58 (specified from the control unit 22). A multi-valued number) and a function of extracting a data signal superimposed on the subcarrier.

  The media access processing unit 51 includes N memories 56 (56-1 to 56-N), a data combination processing unit 57, and a control unit 58. Furthermore, the data combination processing unit 57 includes k subcarrier combination processing units 59 (59-1 to 59-k) and a data selection processing unit 60.

  Each of the memories 56-j (j is an integer from 1 to N) temporarily stores signals input from the multilevel demodulator 55-j and has a function of sequentially reading them in accordance with instructions from the control unit 58.

The data combination processing unit 57 has a function of combining data signals input from the memory 56 and outputting the data signals to the user terminal 6 in accordance with instructions from the control unit 58. The inside of the data combination processing unit 57 is functionally divided into k subcarrier combination processing units 59 (59-1 to 59-k) and a data selection processing unit 60. The subcarrier combination processing unit 59-i (i is an integer from 1 to k) has a function of arranging and combining signals input from the N _i input ports in order and restoring the original downlink data signal. Yes. The data selection processing unit selects an input signal from the subcarrier combination processing unit 59 of the ONU group to which the data selection processing unit belongs, designated by the control unit 58, and outputs the selected signal.

  The control unit 58 has a function of controlling each component of the ONU 5. The control unit 58 instructs the timing and amount to be read to the memory 56. Further, the control unit 58 instructs the data combination processing unit 57 on the data combination method and the group number to which the control unit 58 belongs. Also, it receives the number of subcarriers to be received notified from the OLT 2 and its demodulated multilevel number, and instructs them to the OFDM optical receiver 50.

(A-2) Operation of the First Embodiment Next, the operation of the network system 100 according to the first embodiment having the above configuration will be described with reference to FIGS.

  A signal processing procedure performed until the downlink data signal reaches the user terminal 6 from the upper network 1 via the OLT 2 and the ONU 5 will be described. Hereinafter, the signal processing operation (particularly, the operation of the data distribution processing unit 23 and the memory 24) performed in the OLT 2 will be mainly described. In the network system 100, the same processing as various OLTs and ONUs can be applied to the upstream signal processing, and thus detailed description thereof is omitted.

  First, a signal processing procedure in the OLT 2 will be described with reference to FIG.

  A packet-like downlink data signal input from the higher-level network 1 is distributed by the group distribution processing unit 31 for each ONU group. For example, the group distribution processing unit 31 reads destination information included in downlink signal data, and performs distribution with reference to a table (not shown) in which correspondence between the destination information and the ONU group is registered. The correspondence table is separately instructed (input) from the control unit 22.

Downlink data signals distributed to the ONU group i (i = 1 to k) are divided for each M · A _i [bit] from the top by the subcarrier distribution processing unit 32-i, and then transmitted from different ports. Is output.

Here, M is an arbitrary natural number. Also, A _i [bit / symbol / SC] is a multi-value number when modulating subcarriers belonging to ONU group i.

In FIG. 1, the reference numeral 41 is assigned to the downlink data signal distributed to the subcarrier distribution processing unit 32-1 by the group distribution processing unit 31. Further, in FIG. 1, N ₁ divided data (divided blocks) obtained by dividing the downlink data signal 41 by M · A ₁ [bit] in order from the top are respectively given reference numerals 41-1 to 41-N ₁ . doing. Further, in FIG. 1, downlink data signals distributed by the subcarrier allocation processing unit 32-1 and supplied to the memories 24-1 to 24 -N ₁ are denoted by reference numerals 42-1 to 42-N ₁ , respectively. ing.

In FIG. 1, 45 is assigned to the downlink data signal distributed to the subcarrier distribution processing unit 32-k by the group distribution processing unit 31. In FIG. 1, 45 _k (N−N _k +1) to 45−N are divided into N _k divided data (divided blocks) _obtained by dividing the downlink data signal 45 in order from the top by M · A ₁ [bit]. The sign is attached. Further, in FIG. 1, is distributed by the sub-carrier distribution processing unit 32-k, a memory _24- (N-N k +1) respectively into downlink data signal supplied to _{~24-N 46- (N-N} k +1 ) To 46-N.

For example, the downlink data signal 41 assigned to the ONU group 1 in FIG. 1 is divided for each M · A ₁ [bit] from the top by the subcarrier distribution processing unit 32-1. Then, the first divided data signal 41-1 of the downlink data signal 41 is output toward the memory 24-1. That is, in FIG. 1, the downlink data signal 42-1 is the same as the divided data signal 41-1. Similarly, the second divided data signal 41-2 is output toward the memory 24-2. Thereafter, the same processing is performed, and the N _1st divided data signal 41-N ₁ is output toward the memory 24-N ₁ . The media access processing unit 20 performs the above operation for each ONU group. That is, the N ₁ + 1-th divided data is output again to the memory 24-1. In FIG. 1, the downlink data signal 45 distributed to the ONU group k is also subjected to the same processing as that of the ONU group 1 described above.

The divided downlink data signal is temporarily stored in each memory 24 in units of M · A _i [bit]. And according to the instruction | indication of the control part 22, the memory 24-1-24-N outputs the oldest one among the preserve | saved division signals simultaneously. That is, the signals output from the memories 24-1 to 24-N are a group of signals (referred to as burst signals) surrounded by a frame labeled 40 in FIG.

The multilevel modulator 27-j (j is an integer from 1 to k) determines the subcarrier j as the multilevel number A _i (specified by the control unit 22) according to the divided data signal output from the memory 24-j. Multi-valued). After being converted into a time domain signal by the IDFT 28, it is converted into an optical OFDM signal through the parallel-serial converter 29 and the electro-optical converter 30. Since these operations are the same as the conventional OFDM signal processing operations, description thereof is omitted.

  Next, the configuration of a downstream optical OFDM signal generated by OLT 2 will be described with reference to FIG.

In the OLT 2, as shown in FIG. 1 described above, the downlink data signal is converted into an optical OFDM signal. As a result, the optical OFDM signal has M OFDM symbol periods on the time axis as shown in FIG. This is a periodic configuration called “OFDM signal block”. For each optical OFDM signal block, the data for one burst signal described in FIG. 1 is loaded. Therefore, the correspondence between the optical OFDM signal block and the burst signal of the interface becomes clear. Also, the boundaries between the optical OFDM signal blocks (time points T _{S1 to} T _{S4 in} FIG. 4) are all synchronized on the time axis. Further, in the example of FIG. 4, (either A ₁ to A _K) multi-level number corresponding to each sub-carrier (1 to N sub-carriers) at each timing is also defined.

  Next, a signal processing procedure in the ONU 5 will be described with reference to FIG.

  FIG. 3 illustrates the configuration and operation of the ONU 5-1 belonging to the ONU group 1 as an example. The processing in the ONU 5 is basically the reverse of the signal processing procedure in the OLT 2 described above.

  In each ONU 5, the received optical OFDM signal is restored to the original downlink data signal by the photoelectric converter 52, the serial / parallel converter 53, the DFT 54, and the multilevel demodulator 55. In the ONU 5, parameters related to the subcarriers assigned to the ONU group 4 to which the own apparatus belongs (that is, the number of subcarriers to be received and the multi-value number used for demodulation of the subcarriers) are transmitted via the control unit 58 to the OFDM light. The signal is transmitted to the receiver 50. In the ONU 5, the OFDM optical receiver 50 sets the multilevel demodulator 55 according to these pieces of information. Since the ONU 5 does not need to demodulate other subcarriers (subcarriers assigned to other than the ONU group 4 to which the own device belongs), the function of the multilevel demodulator 55 corresponding to the other subcarriers is stopped. May not be output. In this embodiment, it is assumed that the control unit 58 is notified in advance of information such as the number of subcarriers to be received and the demodulation multilevel number of the subcarriers from the OLT 2. For example, a communication path (logical path) for transmitting and receiving a control signal related to network control is provided in advance between the OLT 2 and the ONU 5 separately from the user data signal, and communication control is performed between the OLT 2 and the ONU 5 via this control signal. Such information may be exchanged.

  The data signal output from the multilevel demodulator 55 is temporarily stored in the memory 56 and output to the subsequent stage according to a signal (trigger) from the control unit 58. This is a process performed for adjusting the processing speed and the reception bit rate in the data combination processing unit 57 subsequent to the multi-level demodulator 55. When the processing speed in the data combination processing unit 57 is sufficiently high, this process may be omitted.

In FIG. 3, the downlink data signals supplied to the subcarrier combination processing unit 59-1 from the multilevel demodulators 55-1 to 55-N ₁ through the memories 56-1 to 56-N ₁ are respectively changed to 62-1. It is denoted by the reference character through _{62-N 1.}

  The subcarrier combination processing unit 59 constituting the data combination processing unit 57 combines and recovers the supplied downlink data signal (divided packet data signal). The subcarrier combination processing unit 59 may assemble a packet by finding, for example, a delimiter representing the beginning and end of the packet from the received downlink data signal.

In Figure 3, the sub-carrier binding process unit 59-1 are denoted by the reference character 61 in the assembled packet by combining the downlink data signal 62-1 to _{62-N 1.}

  The data selection processing unit 60 determines from the signals (packets) output from the subcarrier combination processing units 59-1 to 59-k, the ONU group-4 to which the own device belongs (ONU group-4 notified by the control unit 58). Is output to the user terminal 6 (user network side). Thus, the downlink data signal transmitted from the upper network 1 finally reaches the user terminal 6.

(A-3) Effects of First Embodiment According to the first embodiment, the following effects can be achieved.

  In the first embodiment, the interface signal output from the media access processing unit 20 of the OLT 2 is in a burst form. The media access processing unit 20 can easily adjust the data transfer amount corresponding to the transmission bit rate of the changing optical OFDM signal by appropriately adjusting the transmission interval of the burst signal.

  In the first embodiment, the optical OFDM signal (downlink signal) in OLT 2 has a periodic configuration with M OFDM symbol periods as basic units (optical OFDM signal blocks) on the time axis. Therefore, in OLT 2, the correspondence between the optical OFDM signal block and the burst signal of the interface becomes clear. In OLT2, the boundaries of the optical OFDM signal block are all synchronized on the time axis. If the number of subcarriers of each ONU group 4 is changed in accordance with this boundary, the change synchronized with the entire communication system can be easily performed.

  In the first embodiment, the media access processing unit 20 of the OLT 2 processes and transmits and receives a plurality of packet data signals in the order of arrival. Therefore, in the OLT 2, the packet order always matches in the transmission order and the reception order. In OLT 2, the packet order is not reversed between the reception side and the transmission side.

(B) Second Embodiment Hereinafter, a second embodiment of a master station communication device, a communication method, and a network system according to the present invention will be described in detail with reference to the drawings. In the following description, it is assumed that the master station communication device of the present invention is applied to OLT.

(B-1) Configuration of Second Embodiment The overall configuration of the network system 100A of the second embodiment can also be shown using FIG. In the following, the second embodiment will be described focusing on differences from the first embodiment, and description of the same configuration and operation as those of the first embodiment will be omitted.

  The network system 100A is different from the first embodiment in that the OLT 2 is replaced with the OLT 2A.

  FIG. 5 is a block diagram illustrating a functional configuration of the OLT 2A according to the second embodiment. In FIG. 5, the same or corresponding parts as those in FIG.

  The OLT 2A is different in that the interface between the media access processing unit 20 and the OFDM optical receiver 21 is converted (serialized) into a serial interface. Specifically, as shown in FIG. 5, in the OLT 2A of this embodiment, a parallel-serial converter 25 and a serial-parallel converter 26 are added as an interface between the media access processing unit 20 and the OFDM optical receiver 21. This is different from the first embodiment.

  The parallel-serial converter 25 has a function of converting parallel signals from the memories 24-1 to 24-N into serial signals.

  The serial / parallel converter 26 has a function of converting a serial signal from the parallel / serial converter 25 into a parallel signal.

(B-2) Operation of the Second Embodiment Next, the operation of the network system 100A of the second embodiment having the above configuration will be described. Hereinafter, the difference between the operation of the second embodiment and the first embodiment will be described.

  Hereinafter, a signal processing procedure performed until the downlink data signal reaches the user terminal 6 from the upper network 1 via the OLT 2 and the ONU 5 will be described with reference to FIG.

In the OLT 2A, the divided downlink data signal is temporarily stored in each memory 24 in units of M · A _i [bit]. In the OLT 2A, in accordance with an instruction from the control unit 22, the memories 24-1 to 24-N simultaneously output the oldest one of the stored divided signals to the subsequent stage. The divided signals output from the memories 24-1 to 24-N are time-multiplexed in order by the parallel-serial converter 25 and output in series to the subsequent stage.

  FIG. 7 is an explanatory diagram showing a configuration example of a serial signal supplied from the media access processing unit 20 (parallel / serial converter 25) to the OFDM optical receiver 21 (serial / parallel converter 26).

  In FIG. 7, a batch of burst signals 40 supplied from the parallel-serial converter 25 to the serial-parallel converter 26 is shown.

  As shown in FIG. 7, the burst signal 40 output from the parallel-serial converter 25 is parallelized again in order by the serial-parallel converter 26 in the OFDM optical receiver 21. That is, the divided signal output from the memory 24-j is supplied to the multilevel modulator 27-j.

  In the second embodiment, the configuration of the downstream optical OFDM signal output from the OLT 2A is the same as that of the first embodiment, and the description thereof is omitted. In the second embodiment, the processing of the ONU 5 is also the same as that of the first embodiment, and detailed description thereof is omitted.

(B-3) Effects of Second Embodiment According to the second embodiment, the following effects can be obtained in addition to the effects of the first embodiment.

  In the second embodiment, in the OLT 2A, the interface between the media access processing unit 20 and the OFDM optical receiver 21 is converted (serialized) into a serial interface. As a result, in the second embodiment, the number of interface wirings between the OFDM optical receiver 21 and the media access processing unit 20 can be reduced from N to one. That is, in the second embodiment, the wiring space of the interface between the OFDM optical receiver 21 and the media access processing unit 20 is saved. In the second embodiment, even when the number N of subcarriers is changed in the future, it is not necessary to change the number of wires of the interface between the OFDM optical receiver 21 and the media access processing unit 20.

(C) Third Embodiment Hereinafter, a third embodiment of the master station communication device, the communication method, and the network system according to the present invention will be described in detail with reference to the drawings. Hereinafter, an example in which the master station communication apparatus of the present invention is applied to OLT and the slave station communication apparatus of the present invention is applied to an ONU will be described.

(C-1) Configuration of the Third Embodiment The overall configuration of the network system 100B of the third embodiment can also be shown using FIG. In the following, the third embodiment will be described focusing on differences from the second embodiment, and description of the same configuration and operation as those of the second embodiment will be omitted.

  The network system 100B is different from the second embodiment in that the OLT 2A is replaced with the OLT 2B.

  In the OLT 2B of the third embodiment, the data signal dividing method in the data distribution processing unit 23 is different from that of the second embodiment. Specifically, in the OLT 2B of the third embodiment, the subcarrier distribution processing unit 32 inside the data distribution processing unit 23 is excluded, and the number of memories 24 is changed from N to k. This is different from the second embodiment.

(C-2) Operation of Third Embodiment Next, the operation of the network system 100B of the third embodiment having the above configuration will be described. Hereinafter, the difference between the operation of the third embodiment and the second embodiment will be described.

  Hereinafter, a signal processing procedure performed until the downlink data signal reaches the user terminal 6 from the upper network 1 via the OLT 2B and the ONU 5 will be described with reference to FIG.

In the OLT 2B, the downlink data signal assigned to the ONU group i (i = 1 to k) is temporarily stored in the memory 24-i in units of M, N _i, and A _i [bit] from the top. Here, M is an arbitrary natural number, Ni [SC] is the number of subcarriers belonging to ONU group i, and A _i [bit / symbol / SC] is a multi-value number when modulating subcarriers belonging to ONU group i. And in OLT2B, according to the instruction | indication of the control part 22, the memory 24-1-24-k outputs the oldest thing among the preserve | saved division | segmentation signals simultaneously.

For example, in FIG. 6, the downlink data signal 41 assigned to the ONU group 1 is divided for each of M · N ₁ · A ₁ [bit] from the top. The downlink data signal 41 is temporarily stored in the memory 24-1 and then supplied to the parallel-serial converter 25. That is, in FIG. 6, the downlink data signal 42-1 is the same as the divided data signal 41-1 divided from the downlink data signal 41.

  FIG. 8 is an explanatory diagram showing a configuration example of a burst signal 40B supplied from the media access processing unit 20 (parallel / serial converter 25) to the OFDM optical receiver 21 (serial / parallel converter 26) in the OLT 2B.

In the OLT 2B, the divided signals output from the memories 24-1 to 24-k are time-multiplexed in order by the parallel-serial converter 25, and the burst signal 40B is output in series. The burst signal 40B output from the parallel / serial converter 25 is again parallelized in turn by the serial / parallel converter 26 in the OFDM optical receiver 21. The serial / parallel converter 26 divides the burst signal for each M · A _i [bit] from the head, and outputs the j-th divided signal from the head to the multi-level modulator 27-j.

  In the third embodiment, the configuration of the downstream optical OFDM signal output from the OLT 2B is the same as in the first and second embodiments, and the description thereof is omitted. In the third embodiment, the processing of the ONU 5 is also the same as that of the first and second embodiments, and detailed description thereof is omitted.

(C-3) Effects of the Third Embodiment According to the third embodiment, the following effects can be obtained in addition to the effects of the second embodiment.

  In the OLT 2B of the third embodiment, the subcarrier distribution processing unit 32 inside the data distribution processing unit 23 is excluded, and the number of memories 24 is changed from N to k. Thereby, in OLT2B of 3rd Embodiment, the circuit corresponded to the subcarrier allocation process part 32 can be reduced.

  In the OLT 2B of the third embodiment, the number of memories 24 can be changed from N to k. Furthermore, in the OLT 2B of the third embodiment, the total number k of ONU groups is equal to or less than the total number of subcarriers N. Therefore, when k <N, the number of memories 24 can be reduced.

(D) Other Embodiments The present invention is not limited to the above-described embodiments, and may include modified embodiments as exemplified below.

  (D-1) In the second and third embodiments, the parallel-serial converter 25 is configured as a part of the media access processing unit 20, but is configured as a component different from the media access processing unit 20. You may do it. Similarly, the serial / parallel converter 26 may be configured as a separate component from the OFDM optical receiver 21.

  (D-2) In each of the embodiments described above, the inside of the OLT is illustrated as a configuration roughly divided into a media access processing unit and an OFDM optical receiver, but specific components for each configuration inside the OLT are illustrated. The method of dividing (module) is not limited.

  DESCRIPTION OF SYMBOLS 100 ... Network system, 1 ... Host network, 2 ... OLT, 21 ... OFDM optical receiver, 27-1 to 27-N ... Multi-value modulator, 28 ... IDFT, 29 ... Parallel serial converter, 30 ... Electro-optical conversion 20 ... Media access processing unit, 22 ... Control unit, 23 ... Data distribution processing unit, 31 ... Group distribution processing unit, 32-1 to k ... Subcarrier distribution processing unit, 24-1 to 24-N ... Memory DESCRIPTION OF SYMBOLS 3 ... Optical multiplexer / demultiplexer, 5 ... ONU, 50 ... OFDM optical receiver, 51 ... Media access processing part, 52 ... Photoelectric converter, 53 ... Serial parallel converter, 54 ... DFT, 55-1 to 55- N: Multilevel demodulator, 56-1 to 56-N ... Memory, 57 ... Data combination processing unit, 58 ... Control unit, 59-1 to 59-k ... Subcarrier combination processing unit, 60 ... Data selection processing unit, ... user terminal, 4,4-1~4-k ... ONU group.

Claims (5)

In a master station communication device that connects to a plurality of slave station communication devices via branched optical fibers,
A receiving unit for receiving downlink data;
A data distribution processing unit that distributes data received by the reception unit for each group related to the slave station communication device;
A storage unit for temporarily storing data distributed by the data distribution processing unit;
A control unit that instructs the data distribution processing unit to distribute the received data, and that instructs the read timing of the divided data temporarily stored in the storage unit;
A multi-level modulation unit that modulates data read from the storage unit with a multi-level number;
A signal that is modulated by the multi-level modulation unit, converted to an OFDM signal and output to the slave station communication device side ,
The data distribution processing unit distributes the data received by the reception unit for each group related to the slave station communication device, divides the distributed data into a predetermined division size for each group, and acquires divided data,
The storage unit temporarily stores the divided data acquired by the data distribution processing unit,
The control unit instructs the data distribution processing unit to distribute the received data and the predetermined size, and instructs the read timing of the divided data temporarily stored in the storage unit. Station communication device. The control unit determines a subcarrier to be assigned for each group and a multi-value number used for modulation, determines a division size based on the multi-value number for each group, and instructs the data distribution processing unit. The master station communication device according to claim 1 . A parallel-serial converter that outputs the divided data read from the storage unit as a serial signal;
Wherein acquires the divided data from the serial signal output from the parallel-serial converter, the master station according to claim 1 or 2, characterized in that it further comprises a serial-parallel converter to be supplied to the M-ary modulation section Communication device. In a communication method performed by a master station communication device connected via a branched optical fiber with a plurality of slave station communication devices,
The master station communication device includes a receiving unit, a data distribution processing unit, a storage unit, a control unit, a multi-level modulation unit, and a conversion unit,
The receiving unit receives downlink data,
The data distribution processing unit distributes the data received by the receiving unit for each group related to the slave station communication device,
The storage unit temporarily stores the data distributed by the data distribution processing unit,
The control unit instructs the data distribution processing unit to distribute the received data, and instructs the read timing of the divided data temporarily stored in the storage unit,
The multi-level modulation unit modulates data read from the storage unit with a multi-level number,
The conversion unit converts the signal modulated by the multi-level modulation unit into an OFDM signal and outputs it to the slave station communication device side ,
The data distribution processing unit distributes the data received by the reception unit for each group related to the slave station communication device, divides the distributed data into a predetermined division size for each group, and acquires divided data,
The storage unit temporarily stores the divided data acquired by the data distribution processing unit,
The control unit instructs the data distribution processing unit to distribute the received data and the predetermined size, and instructs the storage unit to read the division data temporarily stored in the storage unit. Method. 4. In a network system having a plurality of slave station communication devices and a master station communication device connected to each of the slave station communication devices by a branched optical fiber, each of the master station communication devices of claim 1-3 . A network system, wherein the master station communication device according to any one of the above is applied.

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