JP5541551B1 - Signal separating apparatus and signal separating method used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal separation device capable of correcting a carrier frequency error between an interference signal and a replica without using a delay control means for frequency correction of the replica.
A signal separation device that generates a replica of a signal component included in a received interference signal and subtracts the replica from the interference signal, thereby separating the interference signal from the signal having the highest strength included in the interference signal. Means for estimating the information sequence as one signal (decoder 12), means for generating a replica of the first signal from the estimated information sequence (modulator 14), means for correcting the frequency of the interference signal (demodulation) 11), means for subtracting the replica of the first signal from the frequency-corrected interference signal (adaptive canceller 15), and means for estimating the information sequence of the second signal from the difference between the interference signal and the replica (decoder) 17).
[Selection] Figure 1

Description

  The present invention relates to a signal separation device and a signal separation method used for the signal separation device, and more particularly, to an improvement in capability of a separation technique for a mixed communication signal used on a reception side of a wireless communication device.

  In recent years, in a wireless communication system, improvement in frequency use efficiency is required for effective utilization of limited radio wave resources. For this purpose, it is desirable to transmit a plurality of signals mixed at the same frequency, and the receiver needs a function of easily separating the interference signals.

  When the radio waves that have interfered with each other arrive from different directions, it is possible to separate the interference signals based on the arrival directions. For example, in the technique described in Patent Document 1 below, a technique for signal separation by independent component analysis is shown.

  Further, in the technique described in Patent Document 2, a method of bidirectional communication at the same frequency has been proposed in order to improve the bandwidth utilization rate in satellite communication. In this communication method, two ground stations transmit signals in the same band to the same communication satellite, and the two signals are mixed and received in the satellite.

  Since the interference signal is directly frequency-converted and transmitted to the ground station, the ground station cannot perform signal separation based on the direction of arrival. Therefore, the ground station uses the transmission signal of its own station as a replica of one of the interference signals, and subtracts it from the interference signal to separate the signals of the other stations.

  With respect to the communication method of Patent Document 2, a method of separating an interference signal without storing a replica of a transmission signal has been proposed with the technique described in Patent Document 3. In the method described in Patent Document 3, a signal having the highest strength included in an interference signal is used as a first signal, and a replica is generated by encoding and modulating an information sequence obtained by demodulating and decoding the first signal. The signal is separated by subtracting the replica from the interference signal.

  Further, as described in FIG. 6, in Patent Document 3, the means for generating a replica uses the carrier wave signal reproduced when demodulating the first signal to generate a replica of the first signal, thereby causing interference. It is characterized by reducing the carrier frequency error between the first signal component in the signal and the replica and improving the signal separation accuracy.

JP 2008-092363 A US 6859641 B2 Japanese Patent Application No. 2012-061556

  However, in the method described in Patent Document 2 described above, in order to use the carrier signal reproduced at the time of demodulation for replica generation, the carrier signal and the modulation signal must be synchronized. As is apparent from FIG. 6, there are a decoder 12 and an encoder 13 between the demodulator 11 and the modulator 14, and the modulator 13 includes a low-pass filter. There is a delay.

  Since the amount of delay varies depending on the communication specifications such as the communication speed and error correction code to be used, it is indispensable to change the delay amount according to the setting in the case of a device that can freely set the communication parameters such as a general-purpose modem. is there. Therefore, as shown in FIG. 7, it is obvious that a delay unit 18 for eliminating this delay and a delay controller 19 for controlling the delay amount are necessary.

  Since there is no correlation between the carrier wave and the modulated signal and it is difficult to estimate the delay amount from the two signals, it is necessary to cause the apparatus to hold an accurate delay amount in all combinations of communication specifications. In that case, it is necessary to estimate and measure the delay amount corresponding to many communication specifications, and there is a problem that the cost for development increases.

  Accordingly, an object of the present invention is to solve the above-described problems, and a signal separation device capable of correcting a carrier frequency error between an interference signal and a replica without using a delay control means for correcting the frequency of the replica, and The object is to provide a signal separation method used therefor.

The signal separation device according to the present invention is a signal separation device that generates a replica of a signal component included in a received interference signal and separates the interference signal by subtracting it from the interference signal.
Means for estimating the information sequence of the signal having the highest strength included in the interference signal as a first signal, means for generating a replica of the first signal from the estimated information sequence, and frequency of the interference signal Means for correcting, means for subtracting the replica of the first signal from the frequency-corrected interference signal, and means for estimating the information sequence of the second signal from the difference between the interference signal and the replica. .

A signal separation method according to the present invention is a signal separation method used in a signal separation device that generates a replica of a signal component included in a received interference signal and subtracts the replica from the interference signal to separate the interference signal.
A process in which the signal separation device estimates the information sequence using the strongest signal included in the interference signal as a first signal, and a process of generating a replica of the first signal from the estimated information sequence; , A process of correcting the frequency of the interference signal, a process of subtracting a replica of the first signal from the frequency-corrected interference signal, and an information sequence of the second signal from a difference between the interference signal and the replica Processing and executing.

  The present invention is configured and operated as described above, so that the carrier frequency error between the interference signal and the replica can be corrected without using the delay control means for correcting the frequency of the replica. can get.

It is a block diagram which shows the structural example of the signal separation apparatus by the 1st Embodiment of this invention. FIG. 2 is a block diagram illustrating a configuration example of a demodulator and a modulator illustrated in FIG. 1. It is a block diagram which shows the structural example of the signal separation apparatus by the 2nd Embodiment of this invention. It is a block diagram which shows the structural example at the time of adding communication quality information to the isolation | separation function shown in FIG. It is a block diagram which shows the structural example of the signal separation apparatus by the 3rd Embodiment of this invention. FIG. 10 is a block diagram illustrating a configuration of an embodiment of a technique described in Patent Literature 3. FIG. 7 is a block diagram in which a delay control unit originally necessary for the configuration shown in FIG. 6 is added.

  Next, embodiments of the present invention will be described with reference to the drawings. First, an outline of a signal separation device according to the present invention will be described. A signal separation device according to the present invention is a signal separation device that generates a replica of a signal included in an interference signal and separates the interference signal.

  The signal separation device according to the present invention includes means for estimating the information sequence of the strongest signal included in the interference signal, means for generating a replica of the first signal from the estimated information sequence, and frequency correcting the interference signal. And means for subtracting the replica from the frequency-corrected interference signal and means for estimating the information sequence of the second signal from the difference between the frequency-corrected interference signal and the replica.

  Thus, in the signal separation device according to the present invention, since the replica of the first signal is subtracted from the frequency-corrected interference signal, it is not necessary to correct the frequency error in replica generation. Therefore, the signal separation device according to the present invention can correct the carrier frequency error between the interference signal and the replica without using the delay control means for correcting the replica frequency.

  FIG. 1 is a block diagram showing a configuration example of a signal separation device according to a first embodiment of the present invention. In FIG. 1, the signal separation device according to the present embodiment includes a demodulator 11, a decoder 12, an encoder 13, a modulator 14, an adaptive canceller 15, a demodulator 16, and a decoder 17. Has been.

  The demodulator 11 demodulates the first signal included in the interference signal, and the decoder 12 decodes the output of the demodulator 11 to estimate the first information sequence. The encoder 13 re-encodes the first information sequence, and the modulator 14 re-modulates the output of the encoder 13 to generate a replica of the first signal.

  The adaptive canceller 15 subtracts the replica of the first signal from the interference signal, and the demodulator 16 demodulates the output of the adaptive canceller 15. The decoder 17 decodes the output of the demodulator 16 and estimates the second information sequence.

  In the present embodiment, the demodulator 11 demodulates the first signal having the highest strength on the premise that there is a sufficient strength difference in the signals included in the interference signal. Further, in the present embodiment, the demodulated signal is subjected to error correction decoding by the decoder 12, thereby estimating a high-quality information sequence related to the first signal. In the present embodiment, the estimated information sequence is re-encoded by the encoder 13 and further re-modulated by the modulator 14 to generate a replica of the first signal.

  Further, in the present embodiment, the demodulator 11 estimates the carrier frequency error of the first signal in the interference signal, generates an interference signal corrected for this, and outputs it to the adaptive canceller 15.

  The adaptive canceller 15 estimates the amplitude and phase difference between the first signal component included in the frequency-corrected interference signal and the replica, and corrects the replica so that these are minimized. By subtracting the amplitude and phase corrected replica from the interference signal, the second signal component is extracted.

  FIG. 2 is a block diagram showing a configuration example of the demodulator and modulator shown in FIG. The operation of the demodulator 11 and the modulator 14 shown in FIG. 1 will be described with reference to FIG. Since functions other than the demodulator 11 and the modulator 14 are the same as those in the above-mentioned Patent Document 2, no particular description will be given. Moreover, the double line in FIG. 2 means a complex signal.

  In FIG. 2, the demodulator 11 includes multipliers 21 and 22, low-pass filters 23 and 24, a local oscillator 25, a phase shifter 26, a complex multiplier 27, a clock regenerator 28, and a downsampler 29. , 30 and a carrier regenerator 31.

  Multipliers 21 and 22 multiply the interference signal and the carrier signal, and low-pass filters 23 and 24 block the high-frequency component of the multiplication result and output a demodulated interference signal. The local oscillator 25 generates a carrier signal, and the phase shifter 26 shifts the phase of the carrier signal by 90 °.

  The complex multiplier 27 multiplies the demodulated interference signal by the frequency correction signal, and the clock regenerator 28 extracts the symbol timing from the frequency corrected interference signal. The down samplers 29 and 30 thin out the frequency-corrected interference signal at the symbol timing extracted by the clock regenerator 28. The carrier regenerator 31 estimates a carrier frequency error from the thinned interference signal and generates a frequency correction signal.

  The demodulator 11 demodulates the received interference signal with a carrier signal generated by the local oscillator 25 first. Since the oscillation frequency of the local oscillator 25 is fixed and there is an error in the oscillation frequency of the transmitter of the first signal, there is an error between the carrier signal and the carrier of the first signal included in the interference signal. An error occurs.

  In the demodulator 11, the carrier wave regenerator 31 estimates this frequency error to generate a frequency correction signal, and repeats complex multiplication of this and the demodulated interference signal, thereby changing the carrier frequency of the first signal. Follow and correct the frequency error of the interference signal. The interference signal after the frequency correction is output from the demodulator 11 and input to the adaptive canceller 15.

  The modulator 14 includes a symbol converter 32, upsamplers 33 and 34, and low-pass filters 35 and 36.

  The symbol converter 32 converts the information sequence of the first signal after re-encoding into symbol information for modulation, and the upsamplers 33 and 34 increase the sampling frequency of the symbol information. The low-pass filters 35 and 36 block the high-frequency component of the output of the upsamplers 33 and 34 and output a modulation signal.

  The modulator 14 modulates the information sequence of the first signal after re-encoding and outputs it as a replica of the first signal without frequency correction.

  As described above, as a means for reducing the error of the carrier frequency between the first signal and the replica in the interference signal, Patent Document 3 corrects the frequency of the replica, but in this embodiment, the interference signal is Correct the frequency. Since both are corrections based on the result of carrier wave recovery in the demodulation of the first signal, there is no difference in performance between the two means.

  Further, in the present embodiment, since the frequency correction of the replica is not performed, no delay control means for realizing this is required. Although there is also a delay between the frequency-corrected interference signal and the replica, since these two signals have high correlation, it is easy to use cross-correlation as shown in Patent Document 2. The delay amount can be estimated.

  FIG. 3 is a block diagram showing a configuration example of a signal separation device according to the second exemplary embodiment of the present invention. In FIG. 3, the signal separation device according to the present embodiment switches the first separation function 51, the second separation function 52, the output of the first separation function 51, and the output of the second separation function 52. And a switch 53 for outputting.

  The first separation function 51 and the second separation function 52 have the same configuration as that of the signal separation apparatus according to the first embodiment of the present invention shown in FIG. In addition, since the interference signal after frequency correction is input to the adaptive cancellers 15 and 16 of the first separation function 51 and the second separation function 52, the interference separation performance is higher than that in the embodiment of Patent Document 3 described above. The improvement is realized.

  In the present embodiment, the operation of the first separation function 51 is the same as that of the signal separation device according to the first embodiment of the present invention described above. On the other hand, the second separation function 52 first demodulates and decodes the second signal to generate a replica, and estimates an information sequence related to the first signal from the difference between the second signal and the interference signal.

  The two separation functions have a relationship in which the first separation function 51 outputs a desirable estimation result when the first signal strength is relatively high, and the second separation function 52 outputs a desirable estimation result when the second signal strength is high. . Therefore, by appropriately switching the outputs of the two separation functions by the switch 53, it becomes possible to follow relative signal intensity fluctuations.

  Switching between the two separation function outputs can be realized, for example, by comparing the communication quality of the first signal and the communication quality of the second signal and selecting the higher quality. Even when a change occurs in the communication quality of the received crosstalk signal by constantly monitoring the output of each communication quality estimator of the first separation function 51 and the second separation function 52, the output of the switch 53 Get the best output.

  Next, an example of means for generating communication quality information will be described with reference to FIG. FIG. 4 is a block diagram showing a configuration example when communication quality information is added to the separation function shown in FIG. More specifically, it is a block diagram showing the configuration of the first separation function 51 when a function for estimating the communication quality of the first signal is added.

  In FIG. 4, the communication quality estimator 101 calculates a bit unit difference between the output of the demodulator 11 and the output of the encoder 13. When the communication quality of the first signal is high, the number of error bits corrected by the decoder 12 is small, so that the difference between the output of the demodulator 11 and the output of the encoder 14 is also small. Conversely, when the communication quality is low, the difference becomes large.

  FIG. 5 is a block diagram showing a configuration example of a signal separation device according to the third exemplary embodiment of the present invention. In FIG. 5, the present embodiment has a configuration in which a switch 61, an adaptive canceller 62, a demodulator 63, and a demodulator 64 are added to the above-described second embodiment of the present invention. .

  Thereby, even when the signal strength of the interference signal is small, signal separation can be realized with high accuracy. Specifically, in order to generate a highly accurate replica signal of the first signal, the information sequence of the first signal is estimated using the replica signal of the second signal that is the output of the adaptive canceller 15.

  By inputting the output to the switch 61, it is possible to generate the first replica signal based on the information sequence of the first signal with higher accuracy than the output of the decoder 12. This process is repeated in a feedback manner, and as a result, highly accurate first and second information series signals are realized.

  Further, since the interference signal after frequency correction is input to the adaptive cancellers 15 and 62, the interference separation performance is improved as compared with the embodiment of Patent Document 3 described above.

  Thus, in the present invention, since the replica of the first signal is subtracted from the frequency-corrected interference signal, it is not necessary to correct the frequency error in replica generation. Therefore, in the present invention, it is possible to correct the carrier frequency error between the interference signal and the replica without using the delay control means for correcting the frequency of the replica.

11, 16, 63 Demodulator 12, 17, 64 Decoder
13 Encoder
14 Modulator
15,62 Adaptive canceller
21 multiplier
22 Multiplier 23, 24, 35, 36 Low-pass filter
25 Local oscillator
26 Phase Shifter
27 Complex multiplier
28 Clock regenerator
29,30 Downsampler
31 Carrier wave regenerator
32 symbol converter
33, 34 Upsampler
51 First separation function
52 Second separation function
53, 61 selector
101 Communication quality estimator
63 Demodulator
64 decoder

Claims (8)

A signal separation device that generates a replica of a signal component included in a received interference signal and separates the interference signal by subtracting it from the interference signal,
Means for estimating the information sequence of the signal having the highest strength included in the interference signal as a first signal, means for generating a replica of the first signal from the estimated information sequence, and frequency of the interference signal Means for correcting, means for subtracting the replica of the first signal from the frequency-corrected interference signal, and means for estimating the information sequence of the second signal from the difference between the interference signal and the replica. A characteristic signal separation device. A signal separation device comprising first and second separation functions for generating a replica of a signal component included in each received interference signal and subtracting this from the interference signal to separate the interference signal,
Each of the first and second separation functions includes means for estimating the information sequence using a signal having the highest strength included in the interference signal as the first signal, and the first signal from the estimated information sequence. Means for generating a replica; means for correcting the frequency of the interference signal; means for subtracting a replica of the first signal from the frequency-corrected interference signal; and a second signal based on a difference between the interference signal and the replica. Means for estimating the information sequence of
One of the first and second separation functions estimates the information sequence of the second signal by subtracting a replica of the first signal from the interference signal,
The other of the first and second separation functions is to estimate the information sequence of the first signal by subtracting the replica of the second signal from the interference signal.   When the intensity of the first signal is higher than that of the second signal, one of the outputs of the first and second separation functions is selected, and the intensity of the second signal is higher than that of the first signal. 3. The signal separation device according to claim 2, wherein the other output of the first and second separation functions is selected.   4. The signal separation device according to claim 1, wherein when the level difference between the interference signals is small, the separated second signal is fed back as a replica signal. 5. A signal separation method used for a signal separation device that generates a replica of a signal component included in a received interference signal and separates the interference signal by subtracting the replica from the interference signal,
A process in which the signal separation device estimates the information sequence using the strongest signal included in the interference signal as a first signal, and a process of generating a replica of the first signal from the estimated information sequence; , A process of correcting the frequency of the interference signal, a process of subtracting a replica of the first signal from the frequency-corrected interference signal, and an information sequence of the second signal from a difference between the interference signal and the replica And a signal separation method. This is a signal separation method used in a signal separation device having first and second separation functions for generating a replica of a signal component included in each received interference signal and subtracting this from the interference signal to separate the interference signal. And
Each of the first and second separation functions estimates the information sequence using the signal having the highest strength included in the interference signal as the first signal, and the first signal is derived from the estimated information sequence. A process of generating a replica; a process of correcting the frequency of the interference signal; a process of subtracting a replica of the first signal from the frequency-corrected interference signal; and a second signal based on a difference between the interference signal and the replica. The process of estimating the information series of
One of the first and second separation functions estimates a second signal information sequence by subtracting a replica of the first signal from the interference signal;
A signal separation method, wherein the other of the first and second separation functions subtracts a replica of the second signal from the interference signal to estimate an information sequence of the first signal.   When the intensity of the first signal is higher than that of the second signal, one of the outputs of the first and second separation functions is selected, and the intensity of the second signal is higher than that of the first signal. 7. The signal separation method according to claim 6, wherein the other output of the first and second separation functions is selected.   8. The signal separation method according to claim 5, wherein when the level difference between the interference signals is small, the separated second signal is fed back as a replica signal.

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