JP3197736B2 - Wireless communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a point-to-multipoint wireless communication system for transmitting a signal between one master station and a plurality of slave stations. The present invention relates to a radio communication system for performing multimedia transmission for allocating a carrier to each slave station and transmitting a plurality of types of signals having different requirements regarding transmission quality.

[0002]

2. Description of the Related Art In a conventional point-to-multipoint communication system, TDMA or FDM is used in which each mobile station divides a radio frequency by time or frequency.
A has been applied.

FIG. 9 shows the principle of FDMA among conventional techniques. In the figure, reference numeral 910 denotes a master station, which performs wireless communication between the master station and a plurality of slave stations. In this figure, 2
The figure shows a case where there are two slave stations 931 and 932. 92
1 and 922 are transmission lines between the master station and the slave stations. At this time, a plurality of carrier waves are prepared, and each slave station transmits a signal using the assigned carrier wave.

[0004] The assignment of carriers is performed irrespective of transmission path characteristics. The characteristics of the transmission path 1 and the transmission path 2 are as shown by the numerals 950 and 970, respectively. Here, the horizontal direction indicates frequency, and the vertical direction indicates power. In this figure, six carrier waves are prepared, and the center frequency of each carrier is f
_{1, f 2, f 3,} f 4, f 5, is f _6.

In the transmission path characteristic 1 indicated by numeral 950, the power spectrum when each carrier transmits is 9
51, 952, 953, 954, 955, 956. On the other hand, when the transmission path 1 has frequency characteristics as shown by 960 due to the influence of multipath, the reception spectrum when each carrier is received is 961, 962, 96
3,964,965,966.

In this case, the 951 has almost no influence of the multipath on the reception spectrum, whereas the 951 has a significant deterioration. Similarly, in transmission path characteristic 2, 97
6 has almost no multipath effect, while 971 has significant degradation.

[0007]

In the case of the prior art,
Even in the case where the transmission path characteristics are degraded as described above, which carrier is allocated to each slave station is irrelevant to the transmission path characteristics or the type of signal being transmitted. When 954 and 962 carriers are allocated to the slave station 2, both slave stations are greatly deteriorated by the influence of multipath.

Accordingly, when the transmission path characteristics of the carrier used by a certain slave station deteriorate, the transmission quality deteriorates, and the condition relating to the quality required of the signal or the service using the signal cannot be satisfied. was there.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem that the transmission quality is deteriorated due to the deterioration of the transmission path quality or the case where the required conditions of the service cannot be satisfied. It is another object of the present invention to provide a point-to-multipoint wireless communication system that can satisfy the requirements of each service.

[0010]

According to the invention, the above-mentioned object is solved by the means described in the claims. The most important feature of the present invention is to determine the transmission path characteristics or the type of signal being transmitted for each slave station, and to select a carrier to use in accordance with these. Oh Ru. That is, in the wireless communication system for transmitting a signal between one master station and a plurality of slave stations by a plurality of wireless carriers, the characteristics of the transmission path between the master station and each slave station are described. And the type of signal to be transmitted.
Means to provide the characteristics and transmission of the transmission path between the master station and each slave station.
This is a wireless communication method in which a wireless carrier is assigned to each slave station according to the type of signal being transmitted .

According to a second aspect of the present invention, there is provided a wireless communication system according to the first aspect.
In the communication system, the signal transmitted between the master station and a certain slave station is
If the signal requires high quality, transmit it from other slave stations.
Configured to preferentially assign carriers with good channel characteristics
It was done.

According to a third aspect of the present invention, there is provided a wireless communication system according to the first aspect.
In Shin scheme, the signals are transmitted by the master station and the slave station rear
Real-time signals require real-time
Configuration so that a carrier with better transmission path characteristics is assigned preferentially over other slave stations transmitting signals that do not require
It is a thing.

According to a fourth aspect of the present invention, there is provided a wireless communication system according to the first aspect.
In Shin scheme, the signals are transmitted by the master station and the slave station image
A communication signal if, which is constituted a good carrier of channel characteristics from the other slave stations to assign with priority.

[0014]

[0015]

FIG. 1 is a diagram for explaining the operation of the present invention.
110 is a master station, 121 is transmission line 1, 122 is transmission line 2,
131 is a slave station 1, 132 is a slave station 2, 150 is a transmission path characteristic 1, 151 is a transmission spectrum of a first carrier,
152 is the transmission spectrum of the second carrier, and 153 is the third transmission spectrum.
154 represents the transmission spectrum of the fourth carrier, 155 represents the transmission spectrum of the fifth carrier, and 156 represents the transmission spectrum of the sixth carrier.

Further, 160 is a multipath frequency characteristic of the transmission line 1, 161 is a reception spectrum of the first carrier, 16
2 is the received spectrum of the second carrier, 163 is the received spectrum of the third carrier, 164 is the received spectrum of the fourth carrier, 165 is the received spectrum of the fifth carrier, 1
66 is a reception spectrum of the sixth carrier, 170 is a diagram showing transmission path characteristics 2, 171 to 176 are transmission spectra,
180 represents the multipath frequency characteristic of the transmission path 2, and 181 to 186 represent the reception spectrum.

The operation of the present invention will be described below with reference to FIG. Referring to FIG.
Signals are transmitted using the transmission lines 121 and 122, and the characteristics of the transmission lines are indicated by numerals 150 and 170.
This is the same as in the case of the prior art described above with reference to FIG. However, in the present invention, by monitoring the transmission path characteristics, a carrier that is not easily degraded by multipath is selected. Therefore, in the slave station 1, 151 carrier waves are
By selecting and using 171 carrier waves in the slave station 2, the influence of multipath can be reduced in either slave station.

In the point-to-multipoint communication, the position of the transmitting / receiving antenna is different for each slave station, and the transmission path is changed. Therefore, the deterioration of the transmission characteristics due to the generated frequency selective fading or the multipath differs for each slave station. That is, the radio carrier that deteriorates differs for each slave station. Therefore, by selecting a wireless carrier that has not deteriorated from the characteristics of the propagation path for each slave station, a carrier having good characteristics can be selected for each slave station, and the frequency can be effectively used as a whole.

Also, there is a case where the quality required by the information transmitted by each slave station for the transmission path is different. This is a case of multimedia communication or the like, and transmits signals such as real-time voice or image or non-real-time data transfer to the same transmission path as necessary. In this case, if the information being transmitted is data transfer or the like, high quality can be ensured by means such as retransmission, so the quality required for the transmission path is relatively low.

However, in the case of real-time transmission, retransmission is impossible, and high quality is required for the transmission path. In this case, the frequency can be effectively used as a whole by, for example, giving a high quality wireless carrier preferentially to real-time transmission. Further, even in the case of the same real-time transmission, image communication requires higher transmission path quality than voice communication. Therefore, the frequency can be effectively used as a whole by, for example, giving a high quality wireless carrier preferentially to image communication.

FIG. 2 is a diagram for explaining the operation in such a case, where 210 is a master station, 221 and 222 are transmission paths, 231 and 232 are slave stations, and 250 and 270 are transmission path characteristics. 251, 252, 271 and 272 represent carrier transmission spectra, 260 and 280 represent multipath frequency characteristics 261, 262, 281 and 282 of transmission lines, and carrier reception spectra.

Referring to FIG.
Transmission to transmission paths 221 and 222 to
It is the same as FIG. In this figure, only two carriers are provided.
Indicates the case. The center circumference of two prepared carrier waves
The wave number is f₁, F_TwoIt is. In this figure, the transmission line characteristic 25
As shown at 0 and 270, f
₁The carrier wave of frequency is deteriorated by fading.

The signal transmitted by the slave station 1 is 241
The signal transmitted by the slave station 2 is 242. At this time, when 241 requests higher quality than 242, by assigning 252 to slave station 1 and 271 to slave station 2, transmission quality according to each request can be provided.

[0024] performs the transmission of real-time service in the slave station 1, When performing data transfer in the slave station 2, may be given the radio carrier of f ₂ which is not deteriorated in the slave station 1. In other words, high transmission path quality is required for real-time services, but data transmission can be delayed, so data can be retransmitted.
This is because high quality is obtained, and the quality required for the transmission path may be lower than that of the real-time service.

Further, performs transmission of the image in the slave station 1, in the slave station 2 when doing the other signal such as speech, gives the radio carrier of f ₂ which is not deteriorated in the slave station 1 Thereby, high transmission quality can be obtained for image transmission.

Although various methods are conceivable for a practical method of monitoring the transmission path quality and allocating a carrier, a typical example will be described below.

1. The process of establishing a line for the first time (when some slave stations are trying to establish a new line while several slave stations are establishing a line) How to select the optimal carrier Try to establish a line before establishing a line Monitor the characteristics of each carrier between the slave station and the master station, select the optimal carrier,
use. There are the following two methods.

(A) Select from vacant carriers Before establishing a line, only the characteristics of vacant carriers are monitored, and the optimum one is selected. Do not change the carrier that is already in use. As a specific example, in the case of monitoring in the slave station by TDD, first, the master station transmits a dummy signal to an empty carrier. The slave station monitors the dummy signal of each carrier and selects an optimum carrier. The result is transferred to the master station, and the carrier to be used is determined.

(B) Select from all The tables regarding the availability of each carrier are stored as the monitoring result of the carrier for the slave station with the established channel.

When a new line is established, the master station transmits a dummy signal to an empty carrier in addition to transmitting an information signal to a carrier in use. The slave station monitors the used carrier wave and selects an available carrier wave. First, a carrier to be used is selected from empty carriers based on the monitoring result. If none of the available carriers are available,
Change the carrier by referring to the already established line table.

Method of Selecting Random Carrier When establishing a line, a line is established with a carrier randomly selected from empty carriers. If the characteristics of the carrier are bad, the carrier is changed by the monitor after the establishment shown in (2).

2. Monitoring after line establishment Monitoring all carriers (a) Monitoring at slave stations (TDD) The master station transmits all carriers. The master station transmits each information signal to the used carrier, and transmits a dummy signal or the like to the unused carrier. The slave station performs reception on each carrier wave and monitors each characteristic. Based on the result, a table as to whether or not each carrier can be used is created for each slave station. This is transferred to the master station. The master station determines a carrier to be assigned to each slave station from the table of each slave station.

(B) Monitoring at the master station (TDD) The signal transmission is periodically stopped for a fixed time, and each carrier is sequentially transmitted from the slave station. The master station monitors this sequentially, monitors the characteristics of all carriers of all slave stations, and creates a table.

(C) Up and Down Separate Frequency The characteristics from the master station to the slave station are performed by the method (a), and the characteristics from the slave station to the master station are performed by the method (b). Monitor only the carrier being used. And monitor only the characteristics of the assigned carrier. If the characteristics are deteriorated on the way, Return to the process.

[0035]

FIG. 3 is a diagram showing a first embodiment of the present invention, wherein 310 is a received signal, 320 is a transmission line characteristic monitor,
31 is filter 1, 332 is filter 2, 333 is filter 3, 334 is filter 4, 341 is power monitor 1,
342 is the power monitor 2, 343 is the power monitor 3, 344
Denotes a power monitor 4, 350 denotes a frequency selection circuit, 351 denotes an output of the frequency selection circuit, 360 denotes an oscillator, 370 denotes an information signal, 380 denotes a transmitter, and 381 denotes a transmission signal.

As is clear from the drawing, this embodiment shows a case where four carrier waves are prepared. The received signal 310 in the slave station is input to the transmission path characteristic monitor 320, is divided into four, and has numeral codes 331, 332, 33
A frequency component corresponding to each carrier is extracted by a filter indicated by 3,334. The extracted components are input to power monitors indicated by numerals 341, 342, 343, and 344, and the results are output to the frequency selection circuit 350.
Sent to According to the frequency selection circuit output 351, the local oscillator 360 outputs the frequency of the selected carrier. Transmitter 380 receives the output of information signals 370 and 360,
A transmission signal 381 is obtained.

This figure is applied to the case of so-called TDD transmission in which the uplink from the slave station to the master station and the downlink from the master station to the slave station use the same frequency. , An optimal carrier can be selected.

That is, the receiver input for each slave station is split for each frequency corresponding to each radio carrier, and the power is monitored. Thereby, it is possible to determine which radio carrier is degraded due to fading. Based on the result, the frequency selection circuit selects a frequency to be used in each slave station.

In this embodiment, only the power in each radio carrier is monitored.
By monitoring the amplitude / delay deviation or measuring the bit error rate or the like using the dummy signal, it is possible to select a frequency with higher accuracy.

Here, since the slave station has a power monitor,
The frequency characteristics of the downlink from the master station to the slave station can be selected. In the case of the uplink from the slave station to the master station, if the transmission and reception are on the same propagation path, they have the same frequency characteristics. Therefore, it is sufficient that one of the master station and the slave station has a power monitor.

Further, if the output of the frequency selection circuit is transferred to another slave station or master station through the transceiver, the control can be performed in consideration of the whole situation, so that the effect can be further enhanced.

FIG. 4 is a diagram showing a second embodiment of the present invention, in which the uplink and the downlink use different frequencies. In the figure, 401 is a diagram of station 1, 402 is a diagram of station 2, 410 is a received signal 1, 411 is a transmission line characteristic monitor, 421, 422, 423, and 424 are filters, 431, 432, 433, and 434 are power. The monitor 440 is a frequency selection circuit, 441 is a frequency selection signal, 450 is an information signal, 451 is a selection signal addition circuit,
52 is a transmitter, 453 is a transmission signal, 460 is a reception signal 2, 461 is a receiver, 470 is a selection signal decoding circuit, 47
Reference numeral 1 denotes a selection signal decoding circuit output, 472 denotes an oscillator, 481 denotes an information signal, 482 denotes a transmitter, and 483 denotes a transmission signal.

In the case of this embodiment, the result of monitoring the power at the partner station is transmitted to the own station, and a carrier is selected based on the result. A received signal 401 at the station 1 indicated by a numeral 401 in FIG.
The frequency components of the respective carrier waves extracted by the filters 21, 422, 423, 424 are respectively 411, 412, 413, 41
4 and the optimum frequency is selected by the frequency selection circuit 440 based on the result, as in FIG.

The resultant frequency selection signal 441 is added to the information signal 450 transmitted from the station 1 to the station 2 by the selection signal adding circuit 451. This signal is transmitted from the transmitter 452 as a transmission signal 453. At station 2 at 402, the signal transmitted from 452 is received
Received at 61.

The received signal is input to the selection signal decoding circuit 470, which reads the frequency selection signal and sends information 471 as a result to the oscillator 472. The oscillator 472 outputs the frequency of the carrier selected according to the information 471.
Based on this, the transmitter 482 that has received the information signal 481 outputs a transmission signal 483.

In the above example, a case has been described in which the optimum carrier is individually selected for each slave station. However, it is determined comprehensively from the optimum carrier wave conditions of each slave station to determine the optimum carrier wave for each slave station. Selecting the carrier to be used is more efficient. This is shown in FIG. That is, FIG. 5 shows a third embodiment of the present invention. Here, a master station when there are three slave stations is shown.

In the figure, reference numerals 501, 502 and 503 denote received signals, 511, 512 and 513 denote transmission line characteristic monitors, 520 denotes a frequency selection circuit, 531, 532 and 533.
Is an information signal, 541, 542, 543 are oscillators, 55
1,552,553 are transmitters, 561,562,563
Indicates a transmission signal.

Received signals 501, 502, 5 from each slave station
03 to the transmission line characteristic monitors 511, 512, 5
13 to monitor the characteristics of each transmission path. The result is input to the frequency selection circuit 520, and a carrier used by each slave station is allocated. This result is sent to each slave station 5
41, 542 and 543 to output the respective carrier frequencies. By this carrier, the information signals 531 and 5
32,533 pass through transmitters 551,552,553,
These are output as transmission signals 561, 562, and 563.

Since the master station can always output the frequencies of all the carrier waves, it is easy to monitor on the slave station side. However, since the slave station transmits only the allocated frequency in a steady state, when monitoring is performed on the master station side, it is necessary to sequentially transmit a test signal in each slave station in a certain time zone.

FIG. 6 is a diagram showing a fourth embodiment of the present invention. According to the second, third, and fourth aspects of the present invention, the type of signal is identified, and the optimum carrier is selected based on the signal type and the transmission path characteristics. The present embodiment corresponds to this.

In the figure, reference numeral 610 denotes a received signal;
Is a transmission line characteristic monitor, 631, 632, 633, 634
Is a filter, 641, 642, 643 and 644 are power monitors, 650 is a frequency selection circuit 651 output of the frequency selection circuit, 660 is an oscillator, 670 is an information signal, 670 is a signal type identification circuit, 672 is a signal type identification signal, and 680. Indicates an information signal, 681 indicates a transmitter, and 682 indicates a transmission signal.

In FIG. 6, the input of the received signal 610 and the input of the transmission path characteristic obtained by the transmission path characteristic monitor 620 to the frequency selection circuit 650 are the same as those described above with reference to FIG. Further, a signal type identification signal 672 is input to the frequency selection circuit 650. The signal type identification signal 672 is the result of the signal type identification circuit 671 that receives the information signal 670 identifying the quality condition required by the information signal.

The output of the frequency selection circuit 650 is
0, which is sent to the transmitter 681 to obtain a transmission signal 682 as in FIG. This is also the case where the uplink and downlink have the same frequency, as in FIG. In the case where the frequency of the uplink is different from the frequency of the downlink, the fifth embodiment shown in FIG.

In the figure, reference numerals 701 and 702 denote a station 1, stations 2 and 710 a received signal 1, 711 a transmission path characteristic monitor, 721, 722, 723 and 724 a filter,
731, 732, 733, 734 are power monitors, 740
Is a frequency selection circuit, 741 is a frequency selection signal, 742 is a signal type identification signal, 750 is an information signal, 751 is a signal type identification circuit, 752 is a selection signal addition circuit, 753 is a transmitter, 754 is a transmission signal, and 750 is reception. Signals 2 and 761 are a receiver, 770 is a selection signal decoding circuit, 771 is a selection signal decoding circuit output, 772 is an oscillator, 781 is an information signal, 7
82 indicates a transmitter and 783 indicates a transmission signal.

This embodiment is the same as FIG. 4 except that the signal type identification signal is input to the frequency selection circuit of the circuit of FIG. 4 described above. FIG. 8 shows a sixth embodiment of the present invention, in which a master station monitors the transmission path characteristics of each slave station and selects a carrier to be assigned to each slave station.
Reference numerals 801, 802 and 803 denote received signals, 811, 812 and
813 is a transmission line characteristic monitor, 820 is a frequency selection circuit,
831,832,833 are information signals 841,842,8
43, a signal type identification circuit; 851, 852, 853, signal type identification signals; 861, 862, 863, an oscillator;
71, 872, 873 are transmitters, 881, 882, 88
3 represents a transmission signal.

This embodiment is the same as FIG. 5 except that the signal type identification signal 672 is input to the frequency selection circuit.

[0057]

As described above, according to the present invention,
In the point-to-multipoint communication, there is an advantage that a signal can be transmitted with high quality for each slave station or for each piece of information being transmitted, and the entire frequency can be used effectively.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the operation of the present invention.

FIG. 2 is a diagram illustrating the operation of the present invention.

FIG. 3 is a diagram showing a first embodiment of the present invention.

FIG. 4 is a diagram showing a second embodiment of the present invention.

FIG. 5 is a diagram showing a third embodiment of the present invention.

FIG. 6 is a diagram showing a fourth embodiment of the present invention.

FIG. 7 is a diagram showing a fifth embodiment of the present invention.

FIG. 8 is a diagram showing a sixth embodiment of the present invention.

FIG. 9 is a diagram illustrating a conventional technique.

[Explanation of symbols]

110, 210 Master station 121, 122, 221, 222 Transmission path 131, 132, 231, 232 Slave station 150, 170, 250, 270 Transmission path characteristic 151-156, 171-176, 251, 252, 2
Transmission spectrum 160, 180, 260, 280 after transmission of 71, 272 Multipath frequency characteristics of transmission path 161-166, 181-186, 261,262,2
81, 282 Carrier reception spectrum 310, 410, 460, 501-503, 610, 7
10,750,801-803 Received signals 320,411,511-513,620,711,8
11-813 Transmission line characteristic monitor 331-334, 421-424, 631-634, 7
21 to 724 filters 341 to 344, 431 to 434, 641 to 644, 7
31 to 734 power monitor 350, 440, 520, 650, 740, 820
Frequency selection circuit 351, 651 Frequency selection circuit output 360, 472, 541 to 543, 660, 772, 8
61 to 863 oscillators 370, 450, 481, 531 to 533, 561 to 5
63,680,750,781,831-833 Information signal 380,452,482,551-553,681,7
53,782,871-873 Transmitter 381,453,483,682,754,783,8
81 to 883 Transmission signal 401, 402, 701, 702 Station 441, 741 Frequency selection signal 451 Selection signal addition circuit 461, 761 Receiver 470, 770 Selection signal decoding circuit 471, 771 Selection signal decoding circuit output 742, 851 to 853 Signal Type identification signal 751, 841 to 843 Signal type identification circuit 752 Signal type identification signal

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-196933 (JP, A) JP-A-5-284089 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 7/24-7/26 H04Q 7/00-7/38

Claims (4)

(57) [Claims] A means for monitoring characteristics of a transmission path between a master station and each slave station in a wireless communication system for transmitting a signal between one master station and a plurality of slave stations by a plurality of wireless carriers. And means for identifying the type of signal to be transmitted, and the characteristics of the transmission path between the master station and each slave station and the transmission signal
Depending on the type, a radio communication system, characterized by allocating a radio carrier for each slave station. 2. The signal transmitted between a master station and a certain slave station is high.
If the signal requires high quality, transmit it from another slave station.
2. The wireless communication system according to claim 1, wherein a carrier having a good path characteristic is assigned with priority . 3. The signal transmitted between the master station and the slave station is real.
For signals that require time characteristics , real-time characteristics
Wireless communication system of claim 1, wherein assigning with priority a good carrier of channel characteristics from the other child station which transmits a signal not required. 4. A signal transmitted between a master station and a slave station is an image communication.
A signal signal if the wireless communication system of claim 1, wherein assigning with priority a good carrier of channel characteristics from the other slave stations.