JPH0683103B2 - Communication method - Google Patents

Description

DETAILED DESCRIPTION [Outline] The modulation method of a radio used for a line forming a closed loop is changed to change the communication capacity, and the reduced communication capacity is diverted to another line.

[Industrial application field]

According to the present invention, interspersed relay stations form a closed loop network,
The present invention relates to a communication system of a transmission line in which these stations communicate with each other.

[Conventional technology]

As shown in FIG. 1, there is a system in which a plurality of node stations A, B, ... Draw lines to each other to form a network. Each station transmits / receives a signal to / from each other, or a certain specific station collects the signal into a signal, and only a control signal is transmitted as a loop signal to all stations.

In such a communication network, for example, when the line is disconnected due to a failure at A / B, the communication between AB is secured by using the optical cable installed side by side or by using the other routes ACB and ADB. Is normal.

If the frequency protection method is used between A and B,
As shown in the figure, a system is prepared in which one standby machine is provided for n active machines and the system is switched to the standby machine when one active machine fails.

[Problems to be solved by the invention]

However, in the system shown in FIG. 6, it is necessary to prepare a spare device, and if this is placed in each node station, a large number of radio devices are additionally required as a whole. Further, as shown in FIG. 1, the method of installing an optical cable and the like also requires extra equipment, and the method of passing through other routes cannot be implemented unless there is always a margin.

The present invention aims to improve these points and cope with a line failure with a small number of radios.

[Means for solving problems]

In the present invention, when a certain line, for example, the line between the A station and the B station in FIG. 1 is deteriorated due to rain or the like, the modulation method of the radio equipment of the A and B stations is changed to reduce the transmission capacity but the required C / N. To secure the line and reduce the transmission capacity to bypass other lines to secure the line capacity.

That is, according to the present invention, a working line is formed between opposing stations of a plurality of stations (A, B, ...), and a signal is received by demodulating at the receiving side after modulating and transmitting the signal at the transmitting side. In the communication system, a working line is provided between all two stations, and the working line between each station normally communicates with a modulation method that does not satisfy the maximum communication capacity, and the working line communication between a certain two stations When the quality deteriorates, the modulation method on the transmitting side is changed so that the communication capacity is lower than that in normal times, and the communication capacity of the deteriorated working line is reduced, and the required C / N is lowered to continue the communication of the working line. In addition, the reduced communication capacity is supplemented by allocating the reduced communication capacity to the redundant communication capacities of a plurality of working lines between the other stations to make the deteriorated working line communication capacity unchanged. It is a thing.

[Action]

According to this method, even if a line fault occurs, the faulty line is used within the usable range without providing a spare radio,
By using the other line for the shortage, communication becomes possible without reducing the transmission amount of the faulty line.

〔Example〕

There are 64QAM, 16QAM, 4PSK, 2PSK, etc. as the modulation method used in the digital microwave radio line, and the line is configured by arbitrarily changing these modulation methods. As a specific example, if the maximum wireless transmission rate is 1 Mb / s, in 64QAM it is approximately 1 Mb / s x 6 at the modulator input, and in 16QAM, 4PSK, 2PSK it is 1 Mb / s x
4, 1Mb / s × 2, 1Mb / s. Also, the theoretical value of the required C / N (Carrier / Noise) to secure an error rate of 1 × 10 ^-4 is 64QA.
About 24.5dB, 18.5dB, 11.4 for M, 16QAM, 4PSK, 2PSK
dB and 8.4 dB.

Thus, for example, the incoming level (C / N) in 64QAM and 16QAM
Since there is a difference of 6 dB, if the transmission line deteriorates and the required error rate (1 × 10 ^-4 ) cannot be secured in 64QAM, the modulation method is changed to 16QAM. In this way, the required error rate can be secured if the transmission line deterioration is within 6 dB. However, due to the change from 64QAM to 16QAM, the transmission capacity is
Reduced to 2/3. Therefore, the reduced amount (1 Mb / s × 2 lines) is transmitted by using the line between AC, CB or AD, DB if another line, for example, between A and B has a line failure and the above is performed. As a result, the transmission capacity between AB can be secured. However, since the transmission capacity of the other lines will increase, always operate with a margin and absorb the detour. Or it is possible to operate up to 256QAM modulation system at all times, and always operate with 64QAM modulation system.
If it becomes necessary to absorb the detour, change 64QAM → 256QAM to make room.

FIG. 2 shows the format of a transmission signal, and one frame (F) is composed of a sync signal SV (for monitoring and control) bits and data. To change the transmission line, determine the deterioration state of the transmission line with the wireless line, send and receive signals with the SV bit to the opposite station,
After confirming the status of this communication network in the reference station, for example, station A, the signal input to the wireless device is converted and input to another wireless device. The deterioration status may be monitored not by the reference station (station A) in the loop but by a station having a line control mechanism outside the loop.

FIG. 3 shows the configuration of a radio device provided in each station, which comprises a logic unit 12, a radio device 14, an antenna 16, and a control unit 18.
A wireless device (shown by 20) of the same configuration is provided for each line (in FIG. 1, each station has three lines, so each station has three lines).
Group), these are connected to a packet switch (which automatically routes the signal to the normal surplus line when the line dies) 10. FIG. 4 shows the main part of the transmitting side for one set.
After detecting the wireless link status of the own station, the input signal sequence change is sent to the reference station through the SV signal. After that, if there is a signal sequence that can be ignored, the amplitude level of the data that enters the 4-phase modulator is controlled to control from 64QAM to 2PSK (other modulation methods (16PS
K, 8PSK, etc. are also possible). Although not shown, the receiving side knows the change of the modulation method due to the signal loss.

Fig. 5 shows the signal sequence of I and Q, 16 values (16QAM) can be obtained by using 1 and 3 vectors respectively, and 4 values by combining only 3 of I and Q (ignoring 1). (4PSK). The conversion from 16-value to 4-value is performed by the logic unit 12. S ₁ is a reception state signal which is the source of this switching. Similarly, 64QAM and 256QAM modulation schemes can be applied.

16QAM of each line is the standard transmission capacity, 64QAM is used when the line condition is good, and 4PSK or 2 when the line deteriorates.
If PSK is used, 1 Mb / s x 2 lines is always available for each line in the above example, and this line can be used as the capacity of the degraded line.

〔The invention's effect〕

As described above, according to the present invention, even if a line fault occurs, the faulty line is used within a usable range without providing a spare radio, and the shortage is prevented by using another line. Communication is possible without reducing the transmission amount of the line. Even if space diversity is not used, if the channel capacity is reduced, it is possible to improve the C / N by about 16 dB with 64QAM → 2PSK, and it is possible to secure the faulty line to some extent with this method. It is effective as a countermeasure against the deterioration of transmission capacity due to the occurrence of obstacles.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a circuit network to which the present invention is applied, FIG. 2 is an explanatory diagram of a format of a transmission signal, FIG. 3 is a block diagram showing a configuration of each node station, and FIG. 4 is transmission for one line. FIG. 5 is a block diagram showing the configuration of the device, FIG. 5 is an explanatory diagram of 16QAM, and FIG. 6 is an explanatory diagram of an example of a conventional system. A in FIG. 1, B, ...... node station, l _1, l _2, ...... the line, third
In the figure, 10 is an exchange, and 16 is an antenna.

Claims (1)

[Claims] 1. A working line is formed between opposing stations of a plurality of stations (A, B, ...), and when a transmitting side modulates and transmits a signal, the receiving side demodulates and receives the signal. In the communication system, a working line is provided between all two stations, and the working line between each station normally communicates with a modulation method that does not satisfy the maximum communication capacity, and the working line communication between a certain two stations When the quality deteriorates, the modulation method on the transmitting side is changed so that the communication capacity is lower than that in normal times, and the communication capacity of the deteriorated working line is reduced, and the required C / N is lowered to continue the communication of the working line. In addition, the reduced communication capacity is supplemented by allocating the reduced communication capacity to the redundant communication capacities of a plurality of working lines between the other stations to make the deteriorated working line communication capacity unchanged. Communication method.