JP5474875B2 - Wireless communication system - Google Patents

Description

The present invention relates to a wireless communication system that diversity reception of radio signals transmitted over a plurality of slave stations from one wireless terminal in the parent station.

FIG. 2 shows a configuration example of a wireless communication system to which the present invention is applied (Patent Document 1).
In FIG. 2, the wireless terminal 1 and the master station device 20 are connected via a plurality of slave station devices 10-1 to 10 -N. The wireless terminal 1 and the plurality of slave station devices 10-1 to 10-N are connected via a wireless line, and the plurality of slave station devices 10-1 to 10-N including a plurality of M antennas and transmission systems are connected to the master station. The device 20 is connected via M × N network cables. The radio signal transmitted from the radio terminal 1 is received by at least one of the plurality of slave station devices 10-1 to 10 -N, and transmitted from the received slave station device to the master station device 20. In the master station device 20, the same signal transmitted from the wireless terminal 1 via two or more slave station devices is subjected to reception diversity by maximum ratio combining. Thereby, even when the transmission power of the wireless terminal 1 is low or the loss of the wireless transmission path is large, the signal can be received. Further, the transmission signal from the master station device 20 to the wireless terminal 1 takes the reverse path, and transmission diversity by the master station device 20 is also possible. The plurality of slave station apparatuses 10-1 to 10-N and the master station apparatus 20 are not limited to a form in which the slave station apparatuses 20 are connected via M × N network cables, but a PON (Passive) having an N: 1 transmission path form. An optical network system or an Ethernet (registered trademark) system may be used.

  FIG. 3 shows a configuration example of a slave station device and a master station device of the wireless communication system. Here, it corresponds to a configuration in which reception diversity is performed in the master station device 20, and wirelessly transmits from the wireless terminal 1 to the master station device 20 via the three slave station devices 10-1 to 10-3 (when N = 3). The structural example about the uplink direction which transmits a signal is shown. Each of the slave station devices 10-1 to 10-3 includes M antennas (M = 2 in FIG. 3) and a transmission system, and the slave station devices 10-1 to 10-3 and the master station device 20 have three. X A configuration in which two network cables are connected. That is, even when there is one slave station device that can communicate with the wireless terminal 1, the master station device 20 can perform reception diversity.

  In FIG. 3, the slave station devices 10-1 to 10-3 convert the received signals from the wireless terminals 1 received by the antennas 11-1 to 11-2 using the AD conversion processing units 12-1 to 12-2. , Filtering, AD conversion (sampling, digitization), etc., and the obtained digital signal is packetized by the packetization processing units 13 to 13-2, and the transmission / reception device numbers and the like by the header processing units 14-1 to 14-2 Is added. Thereafter, it is converted into an Ethernet packet by the network interfaces 15-1 to 15-2 and transmitted to the master station device 20.

  The master station device 20 extracts the Ethernet packet from the signal received by the network interface 21, extracts the transmission / reception device number by the header processing unit 22, and reproduces the digital signal by the packetization processing unit 23. The frame synchronization processing unit 24 extracts a radio signal transmitted from the radio terminal 1 by autocorrelation processing or the like with respect to the reproduced digital signal. The synchronous detection circuit 25 performs synchronous detection processing on the radio signal and outputs a soft decision value. The processing up to this point is processed independently for each radio signal received by each of the antennas 11-1 to 11-2 of each of the slave station devices 10-1 to 10-3.

  The combination detection unit 26 determines whether, for example, the received power exceeds a threshold for the soft decision values of the radio signals received by the antennas 11-1 to 11-2 of the slave station devices 10-1 to 10-3. Based on such a criterion, one (combination) to be used for the subsequent processing is selected and output to the soft decision maximum ratio composition processing unit 27. The soft decision maximum ratio combining processing unit 27 performs maximum ratio combining on the combinations of the soft decision values of the radio signals received by the antennas 11-1 to 11-2 of the slave station devices 10-1 to 10-3, Output to likelihood calculation processing unit 29. The likelihood calculation processing unit 28 calculates the likelihood of the soft decision value subjected to the maximum ratio synthesis and outputs the likelihood to the Viterbi decoding processing unit 29. The Viterbi decoding processor 29 decodes the input likelihood sequence according to the Viterbi algorithm.

  With the configuration of the slave station devices 10-1 to 10-3 and the master station device 20, the modulation / demodulation function can be integrated into the master station device 20, and the cost and maintenance cost of the slave station device can be reduced. Can be flexibly handled, which is advantageous for rapid deployment of new systems. Further, since wireless signals are transferred on a packet basis, it is possible to use an existing packet-based network service and to operate at a low cost. By using this method, it is possible to widen the radio access network of about several kilometers.

JP 2007-166278 A

  In the master station apparatus, the maximum ratio combining process of radio signals transmitted from a radio terminal transmitted through a plurality of slave station apparatuses is performed, so that the number of slave station apparatuses that relay radio signals from the radio terminals and each slave station Diversity gain according to the number of antennas of the device can be obtained. However, since the radio signal transmitted from each slave station device is a sampling value of the radio signal waveform, the amount of information is large, and the transmission capacity of the line or network system connecting each slave station device and the master station device is reduced. .

  On the other hand, when demodulating the radio signal received by each slave station device and transferring it to the master station device, the amount of information is reduced, but the diversity effect due to the maximum ratio combining of the slave station devices cannot be obtained, Reception quality deteriorates.

The present invention reduces the amount of information when transmitting a radio signal transmitted from the wireless terminal to the master station through a plurality of slave station devices, and a wireless communication system capable of obtaining a required diversity gain The purpose is to provide.

  A first aspect of the present invention is a wireless communication system in which a master station apparatus receives diversity signals transmitted from a single wireless terminal via a plurality of slave station apparatuses. The slave station apparatus receives a wireless signal transmitted from the wireless terminal. A plurality of antennas to be received, a frame synchronization processing means for extracting a radio signal transmitted from a wireless terminal by performing autocorrelation processing on each of the reception signals of the plurality of antennas, and a radio signal output by the frame synchronization processing means , Synchronous detection means for outputting a soft decision value corresponding to each antenna, first soft decision maximum ratio combining processing means for combining the maximum soft decision values corresponding to each antenna, and a first soft decision maximum First likelihood calculation processing means for calculating the likelihood of the maximum ratio combined soft decision value output from the ratio combining processing means, and the likelihood of the soft decision value output from the first likelihood calculation processing means The master station First interface means for transmitting to the master station device, the master station device receiving second soft interface decision means for receiving the likelihood of the soft decision value transmitted from the slave station device, and the soft decision received by the second interface device A second soft decision maximum ratio combining unit that combines the likelihoods of the values in a maximum ratio; and a decoding unit that decodes and outputs the likelihood of the soft decision values output from the second soft decision maximum ratio combining unit. .

  According to the present invention, a diversity gain equivalent to the maximum ratio combining of the soft decision values of the radio signals received by the antennas of the slave station devices can be obtained in the master station device.

  Further, since the signal transmitted from each slave station device to the master station device is the likelihood (about several bits at most) obtained from the soft decision value of the radio signal received by each antenna, the digital signal of the conventional radio signal is obtained. Compared with the case of transmitting values, the amount of information can be significantly reduced. Further, since the likelihood is obtained by combining the soft decision values of the radio signals received by the respective antennas with the maximum ratio, the information amount corresponding to one antenna is collected regardless of the number of antennas of each slave station device. Therefore, the amount of information can be further reduced.

It is a figure which shows the structural example of the sub_station | mobile_unit apparatus of a radio | wireless communications system of this invention, and a main | base station apparatus. It is a figure which shows the structural example of the radio | wireless communications system to which this invention is applied. It is a figure which shows the structural example of the subunit | mobile_unit apparatus and parent | base station apparatus of the conventional radio | wireless communications system.

FIG. 1 shows a configuration example of a slave station device and a master station device of a wireless communication system of the present invention.
Here, a configuration example in the uplink direction in which a radio signal is transmitted from the wireless terminal 1 to the master station device 20 via the three slave station devices 10-1 to 10-3 (when N = 3) is shown. Also, a configuration example in which each of the slave station devices 10-1 to 10-3 includes M antennas (M = 2 in FIG. 1) and a transmission system is shown.

  In FIG. 1, the slave station devices 10-1 to 10-3 perform frame synchronization processing between the AD conversion processing units 12-1 to 12-2 and the packetization processing unit 13 similar to the conventional configuration shown in FIG. 3. Units 41-1 to 41-2, synchronous detection circuits 42-1 to 42-2, soft decision maximum ratio synthesis processing unit 43, likelihood calculation processing unit 44, packetization processing unit 13, header processing unit 14, The network interface 15 is configured as one system.

  The frame synchronization processing units 41-1 to 41-2 extract radio signals transmitted from the radio terminal 1 by autocorrelation processing or the like with respect to the digital signals output from the AD conversion processing units 12-1 to 12-2. . The synchronous detection circuits 42-1 to 42-2 perform synchronous detection processing on the radio signal and output a soft decision value. The processing so far is performed independently for each radio signal received by each of the antennas 11-1 to 11-2.

  The soft decision maximum ratio combining processing unit 43 performs maximum ratio combining on the soft decision values of the radio signals received by the antennas 11-1 to 11-2 and outputs the result to the likelihood calculation processing unit 44. The likelihood calculation processing unit 44 generates likelihood information including a quantization bit and a received signal level from the soft decision value obtained by maximum ratio synthesis, and outputs the likelihood information to the packetization processing unit 13. The packetization processing unit 13 packetizes the likelihood information of the soft decision value, and the transmission / reception device number and the like are added by the header processing unit 14. Thereafter, the packet is converted into an Ethernet packet by the network interface 15 and transmitted to the master station device 20 via the network cable.

  The master station device 20 extracts an Ethernet packet from a signal received by the network interface 21, extracts a transmission / reception device number by the header processing unit 22, and a packetization processing unit 23 from each of the slave station devices 10-1 to 10-3. The likelihood information of the transmitted soft decision value is reproduced. The processing up to this point is processed independently for each piece of soft decision value likelihood information transmitted from each slave station device.

  The combination detection unit 26 uses the soft decision value likelihood information transmitted from each slave station device for subsequent processing based on, for example, a criterion such as whether or not the likelihood exceeds a threshold ( Combination) is selected and output to the soft decision maximum ratio composition processing unit 27. The soft decision maximum ratio combining processing unit 27 performs maximum ratio combining on the likelihood combinations of the soft decision values transmitted from the respective slave station devices, and outputs the result to the likelihood calculating processing unit 29. The likelihood calculation processing unit 28 calculates the likelihood of the soft decision value subjected to the maximum ratio synthesis and outputs the likelihood to the Viterbi decoding processing unit 29. The Viterbi decoding processor 29 decodes the input likelihood sequence according to the Viterbi algorithm.

  As described above, the slave station devices 10-1 to 10-3 calculate the likelihood by combining the soft decision values generated by synchronously detecting the radio signals received by the antennas 11-1 to 11-2 with the maximum ratio. Then, each is transmitted to the master station device 20. The master station device 20 combines the likelihoods transmitted from the slave station devices 10-1 to 10-3 with a maximum ratio. Thereby, in the master station device 20, the diversity gain equivalent to the maximum ratio combining of the soft decision values of the radio signals received by the antennas 11-1 to 11-2 of the slave station devices 10-1 to 10-3. Can be obtained.

  In addition, signals transmitted from the slave station devices 10-1 to 10-3 to the master station device 20 are likelihoods (at most) obtained from soft decision values of radio signals received by the antennas 11-1 to 11-2. Therefore, the amount of information can be remarkably reduced as compared with the case where a digital value of a conventional radio signal is transmitted. Furthermore, since it is the likelihood obtained by combining the soft decision values of the radio signals received by the respective antennas 11-1 to 11-2 with the maximum ratio, the amount of information corresponding to one antenna system can be obtained regardless of the number of antennas. As a result, the amount of information can be further reduced.

DESCRIPTION OF SYMBOLS 1 Radio | wireless terminal 10 Slave station apparatus 11 Antenna 12 AD conversion process part 13 Packetization process part 14 Header process part 15 Network interface 20 Master station apparatus 21 Network interface 22 Header process part 23 Packetization process part 24 Frame synchronization process part 25 Synchronous detection Circuit 26 Combination detection unit 27 Soft decision maximum ratio synthesis processing unit 28 Likelihood calculation processing unit 29 Viterbi decoding processing unit 41 Frame synchronization processing unit 42 Synchronous detection circuit 43 Soft decision maximum ratio synthesis processing unit 44 Likelihood calculation processing unit

Claims (1)

In a wireless communication system in which a master station apparatus receives diversity signals transmitted from a single wireless terminal via a plurality of slave station apparatuses,
The slave station device is
A plurality of antennas for receiving radio signals transmitted from the radio terminal;
Frame synchronization processing means for performing autocorrelation processing on each of the reception signals of the plurality of antennas and extracting a wireless signal transmitted from the wireless terminal;
Synchronous detection means for synchronously detecting a radio signal output by the frame synchronization processing means and outputting a soft decision value corresponding to each antenna;
First soft decision maximum ratio combining processing means for combining a maximum soft decision value corresponding to each antenna;
First likelihood calculation processing means for calculating the likelihood of the maximum ratio combined soft decision value output from the first soft decision maximum ratio combining processing means;
First interface means for transmitting the likelihood of the soft decision value output from the first likelihood calculation processing means to the master station device;
The master station device is
Second interface means for receiving the likelihood of the soft decision value transmitted from the slave station device;
Second soft decision maximum ratio combining means for combining the likelihoods of the soft decision values received by the second interface means with a maximum ratio;
A wireless communication system comprising: decoding means for decoding and outputting the likelihood of the soft decision value output from the second soft decision maximum ratio combining means.

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