JP2008053798A - Radio receiving device and radio communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio reception device which causes no deterioration in quality even when respective frequencies do not mach each other in a radio system which transmits signals of the same frequency band in parallel. <P>SOLUTION: The radio reception device comprises: a means of receiving first and second reception signals in which first and second transmission signals are mixed respectively and then detecting a first frequency error of the first transmission signal and a second frequency error of the second transmission signal on the basis of preambles included in the first and second transmission signals, a frequency error compensating means of compensating frequencies of the first and second reception signals on the basis of the first and second frequency errors, and an interference compensating means of calculating a propagation path matrix on the basis of the output of the frequency error compensating means and restores the first and second transmission signals from the first and second reception signals respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radio communication system that uses signals of a plurality of polarizations for improving frequency utilization efficiency and a radio reception apparatus of the radio communication system.

  As shown in FIG. 2, in order to improve frequency utilization efficiency, a wireless communication system that transmits and receives signals with the same frequency shared by a plurality of transmission / reception antennas has been proposed (for example, see Non-Patent Document 1). According to FIG. 2, the wireless communication system has a transmitting station and a receiving station, and the transmitting station includes modulation circuits 40 and 41, frequency conversion circuits 42 and 43, transmission antennas 44 and 45, an oscillation circuit 56, and the like. The receiving station includes receiving antennas 46 and 47, frequency conversion circuits 48 and 49, frequency error detection circuits 50 and 51, frequency error compensation circuits 52 and 53, demodulation circuits 54 and 55, and an oscillation circuit 57. And an averaging circuit 58 and an interference compensation circuit 59.

  Next, the signal flow of the wireless communication system will be described. In the transmission station, the first transmission signal modulated by the modulation circuit 40 is frequency-converted by the frequency modulation circuit 42 and output from the transmission antenna 44 as a first transmission radio signal. Similarly, the second transmission signal modulated by the modulation circuit 41 is frequency-converted by the frequency modulation circuit 43, and the second transmission radio signal having a polarization orthogonal to the first transmission radio signal is transmitted from the transmission antenna 45. Is output as Here, both the frequency conversion circuits 42 and 43 use the output signal of the oscillation circuit 56 for frequency conversion.

  In the receiving station, the first received radio signal received by the receiving antenna 46 is frequency-converted to the first received signal by the frequency converting circuit 48, and the second received radio signal received by the receiving antenna 47 is the frequency converting circuit. 49, the frequency is converted into a second received signal. Similar to the transmitting station, both frequency conversion circuits 48 and 49 use the output signal of the oscillation circuit 57 for frequency conversion.

  Subsequently, the deviation of the first received signal from the desired frequency, that is, the frequency error is detected by the frequency error detection circuit 50, and the frequency error of the second received signal is detected by the frequency error detection circuit 51. Here, since each of the transmitting station and the receiving station performs frequency conversion of each signal with reference to a single oscillation circuit, the frequency error detected by the frequency error detection circuit 50 and the frequency error detection circuit 51 detect the frequency error. The frequency errors are ideally equal. Actually, each signal is individually influenced by noise or the like, and the frequency error detected by the frequency error detection circuits 50 and 51 is smoothed by the averaging circuit 58 in order to smooth the influences generated individually. The average frequency error is output to the frequency error compensation circuits 52 and 53.

  The frequency error included in the first received signal is compensated based on the average frequency error in the frequency error compensation circuit 52, and the frequency error included in the second received signal is converted into the average frequency error in the frequency error compensation circuit 53. The first and second received signals that have been compensated based on the frequency error are input to the interference compensation circuit 59.

  The interference compensation circuit 59 separates the first transmission signal and the second transmission signal included in the first reception signal, and separates the first transmission signal and the second transmission signal included in the second reception signal. Then, the first transmission signals obtained by the separation are combined to output a first transmission restoration signal, and similarly, the second transmission signals obtained by the separation are combined to output the second transmission restoration signal. The first transmission restoration signal is demodulated by the demodulation circuit 54, and the second transmission restoration signal is demodulated by the demodulation circuit 55.

Yusuke Sakurai, Kei Kurosaki, Takatoshi Sugiyama, Masahiro Umehira, “Proposal of AFC method suitable for SDM-COFDM system”, IEICE Technical Report, DSP2001-142, SAT200-100, RCS2001-200, pp. 125-130, January 2002

  Assume that two independent transmission apparatuses are used to realize the transmission station of FIG. The system configuration in this case is shown in FIG. In the configuration of FIG. 2, the frequency conversion circuits 42 and 43 of the transmission station use the same oscillation circuit 56 for frequency conversion processing. However, in the configuration of FIG. 3, two independent transmission devices are used. The frequency conversion circuit 42 uses the oscillation circuit 60, the frequency conversion circuit 43 uses the oscillation circuit 61, and a different oscillation circuit is used for frequency conversion processing.

  Such a situation is common in satellite communications. Since ordinary transmission / reception devices are built on the assumption that only one of the polarized waves is used, when implementing polarization multiplexing communication using an existing device, the transmitting station is shown in FIG. As shown, two independent transmission devices are used together.

When two independent transmission devices are used, an oscillation circuit having a different frequency conversion circuit 42 and frequency conversion circuit 43 is used for frequency conversion processing, and therefore the first transmission radio signal and the second transmission radio signal have different frequencies. It becomes. The first reception radio signal received by the reception antenna 46 is a mixture of the first transmission radio signal and the second transmission radio signal. Therefore, the first reception signal after frequency conversion in the frequency conversion circuit 48 is performed. , the frequency _{f t1} of the oscillation circuit 60, the frequency _{f t2} of the oscillation circuit 61, when the frequency of the oscillation circuit 57 and _{f r,} and _{Δf 1 = f t1 -f r,} Δf 2 = f t2 -f r Thus, signals having two frequency errors are mixed. Similarly, also the second received signal after frequency conversion in the frequency conversion circuit 49, a signal having a Δf ₁ = _f t1 -f _r, of Δf ₂ = _f t2 -f _r, the two frequency error coexist It will be. The frequency error detection circuits 50 and 51 cannot detect a correct frequency error from a signal including two frequency errors. In FIG. 3, the frequency error detection circuit 50 converts the frequency error Δf ₁ ′ into a frequency error. The detection circuit 51 detects the frequency error Δf ₂ ′, the averaging circuit 58 averages the frequency error Δf ₁ ′ and the frequency error Δf ₂ ′, and outputs the average frequency error Δf ₃ to the frequency error compensation circuits 52 and 53. To do.

As a result, since the frequency error compensation circuits 52 and 53 perform frequency error compensation by the average frequency error Δf _3, the signals output from the frequency error compensation circuit 52 include Δf ₄ = Δf ₁ −Δf ₃ and Δf ₅ = Similarly, two different frequency errors of Δf ₂ −Δf ₃ are included, and similarly, the signal output from the frequency error compensation circuit 53 also includes Δf ₄ = Δf ₁ −Δf ₃ and Δf ₅ = Δf ₂ −Δf ₃ . Two different frequency errors will be included. Therefore, it is necessary for the interference compensation circuit 59 to perform propagation path estimation with the frequency error remaining, and the accuracy is deteriorated. As the propagation path estimation accuracy deteriorates, the interference compensation accuracy also deteriorates, resulting in a problem that the demodulated signal quality eventually deteriorates.

  Therefore, the present invention relates to a wireless system that transmits signals in the same frequency band in parallel with different polarizations, where the frequencies of the wireless signals transmitted in parallel do not match due to the use of oscillation circuits that are independent of each other. Even if it exists, it aims at providing the radio | wireless receiver and radio | wireless communications system which do not produce quality degradation.

According to the wireless receiver in the present invention,
The first transmission radio signal obtained by frequency-converting the first transmission signal and the first transmission radio signal having the orthogonal polarization and the second transmission radio signal obtained by frequency-converting the second transmission signal are received. A first receiving antenna, a second receiving antenna, and a first received radio signal received by the first receiving antenna, and frequency-converted to output a first received signal The first reception frequency conversion means and the second reception radio signal received by the second reception antenna are frequency-converted using the same oscillation means used by the first reception frequency conversion means, Second reception frequency converting means for outputting two received signals, a first frequency error received by the first transmission signal included in the first and second received signals, and the first and second received signals The second frequency error received by the second transmission signal included in the Frequency error detection means, first frequency error compensation means for compensating the frequency of the first received signal based on the first frequency error, and frequency compensation of the second received signal based on the first frequency error Second frequency error compensation means, third frequency error compensation means for compensating the frequency of the first received signal based on the second frequency error, and frequency compensation of the second received signal based on the second frequency error A propagation path matrix is calculated based on the outputs of the fourth frequency error compensation means and the first, second, third and fourth frequency error compensation means, and the first received signal and the first frequency are calculated based on the propagation path matrix. And an interference compensation means for restoring the first transmission signal and the second transmission signal from the two received signals.

According to another embodiment of the wireless receiver of the present invention,
Each of the first transmission signal and the second transmission signal includes a section in which there is no signal, and the first frequency error is that the first transmission signal is not a signal and the second transmission signal is not a signal. The second frequency error is detected from the first reception signal and / or the second reception signal in a section that is a signal, and the first transmission signal is no signal and the second transmission signal is no signal. It is also preferable to detect from the first received signal and / or the second received signal in a non-interval.

Further, according to another embodiment of the wireless reception device of the present invention,
The frequency error detection means preferably detects the first frequency error and the second frequency error based on the signal restored by the interference compensation means.

Further, according to another embodiment of the wireless reception device of the present invention,
The first transmission signal includes a first unique word, the second transmission signal includes a second unique word, and the interference compensation means includes the output of the first frequency error compensation means and the first unique word. , The correlation between the output of the second frequency error compensation means and the first unique word, the correlation between the output of the third frequency error compensation means and the second unique word, and the fourth frequency error compensation It is also preferable to calculate the propagation path matrix based on the correlation between the output of the means and the second unique word.

According to the wireless communication system of the present invention,
A wireless communication system including the wireless reception device and a wireless transmission device, wherein the wireless transmission device converts a first transmission frequency to a first transmission frequency, a second transmission signal, Second transmission frequency conversion means for frequency conversion using oscillation means different from the first transmission frequency conversion means, and first transmission for transmitting the first transmission signal after the frequency conversion as a first transmission radio signal An antenna and a second transmission antenna that transmits the second transmission signal after frequency conversion as a second transmission radio signal having a polarization orthogonal to the first transmission radio signal are provided.

  By individually estimating the frequency error of transmission signals with polarizations orthogonal to each other and compensating each received signal with the estimated frequency error, the elements of the channel matrix components to be extracted are compensated for the frequency error. Estimation can be performed, and interference can be accurately compensated from a received signal in which different frequency errors are mixed. Therefore, by combining existing devices, high-speed communication using both polarized waves can be quickly and inexpensively.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a configuration diagram of a wireless communication system according to the present invention, and the wireless communication system includes a wireless transmission device and a wireless reception device. According to FIG. 1, the wireless transmission device includes modulation circuits 11 and 12, frequency conversion circuits 13 and 14, oscillation circuits 15 and 16, and transmission antennas 17 and 18.

The frequency conversion circuit 13 converts the frequency of the first transmission signal modulated by the modulation circuit 11 based on the signal of the frequency f _t1 output from the oscillation circuit 15, and the transmission antenna 17 converts the frequency-converted first transmission signal. Is output as a first transmission radio signal. Similarly, the frequency conversion circuit 14 converts the frequency of the second transmission signal modulated by the modulation circuit 12 based on the signal of the frequency _ft2 output from the oscillation circuit 16, and the transmission antenna 18 converts the frequency-converted second transmission signal. Is transmitted as a second transmission radio signal having a polarization orthogonal to the first transmission radio signal. Since the frequency conversion circuit 13 and the frequency conversion circuit 14 perform frequency conversion using different oscillation circuits, the frequencies of the first transmission radio signal and the second transmission radio signal generally do not match. Deviation occurs. Here, the format shown in FIG. 4A is used as the first transmission signal, and the format shown in FIG. 4B is used as the second transmission signal.

  Further, according to FIG. 1, the radio receiver according to the present invention includes receiving antennas 19 and 20, frequency conversion circuits 21 and 22, a reception frequency error detection circuit 200, frequency error compensation circuits 25, 26, 27, and 28. , An interference compensation circuit 300, demodulation circuits 33 and 34, and an oscillation circuit 35. The reception frequency error detection circuit 200 includes frequency error detection circuits 23 and 24. The interference compensation circuit 300 includes a unique word match. And the MMSE circuit 36.

The frequency conversion circuit 21 performs frequency conversion on the first received radio signal received by the reception antenna 19 based on the signal of the frequency _fr output by the oscillation circuit 35 and outputs the first reception signal. The frequency conversion circuit 22 The second received radio signal received by the receiving antenna 20 is frequency-converted based on the signal of the frequency _fr output from the oscillation circuit 35, and the second received signal is output. Due to the interference between the polarizations, the first transmission signal and the second transmission signal are mixed in the first reception signal and the second reception signal, respectively. Therefore, Δf ₁ = f _t1 −f _r for both signals, Delta] f ₂ = _f t2 will contain two different frequency error -f _r.

However, as shown in FIGS. 4A and 4B, the first preamble period of the first transmission signal overlaps the no-signal section of the second transmission signal, and the second transmission signal Since the period of the second preamble and the no-signal section of the first transmission signal overlap, the radio reception apparatus can receive the first preamble and the second preamble without mixing, The first received signal and the second received signal are as shown in FIGS. 4C and 4D, respectively. The frequency error detection circuit 23 detects the frequency error Δf ₁ from the first preamble period of the first reception signal and / or the second reception signal, notifies the frequency error compensation circuits 25 and 27, and detects the frequency error. The circuit 24 detects the frequency error Δf ₂ from the second preamble period of the first reception signal and / or the second reception signal and notifies the frequency error compensation circuits 26 and 28 of the frequency error Δf ₂ .

The frequency error compensation circuit 25 corrects the frequency of the first reception signal based on the frequency error Δf ₁ , and the frequency error compensation circuit 27 corrects the frequency of the second reception signal based on the frequency error Δf ₁ , The compensation circuits 25 and 27 ideally output a mixed signal of the first transmission signal that has been completely frequency compensated and the _second transmission signal in which a frequency error of Δf ₂ −Δf ₁ remains. Similarly, the frequency error compensation circuit 26 corrects the frequency of the first reception signal based on the frequency error Δf ₂ , and the frequency error compensation circuit 28 corrects the frequency of the second reception signal based on the frequency error Δf _2. The frequency error compensation circuits 26 and 28 output a mixed signal of a first transmission signal in which a frequency error of Δf ₁ −Δf ₂ remains and ideally a second transmission signal that is completely frequency compensated.

The unique word matched filter 29 performs a matched filter process on the first unique word, and indicates the proportion of the first transmission signal included in the first reception signal frequency-compensated by the frequency error compensation circuit 25. The path matrix component h ₁₁ is extracted, and the unique word matched filter 31 performs a matched filter process on the first unique word and is included in the second received signal frequency-compensated by the frequency error compensation circuit 27. The propagation path matrix component h ₂₁ which means the ratio of the transmission signal is extracted. Similarly, the unique word matched filter 30 performs matched filter processing on the second unique word, and calculates the ratio of the second transmission signal included in the first reception signal frequency-compensated by the frequency error compensation circuit 26. A meaning channel matrix component h ₁₂ is extracted, and the unique word matched filter 32 performs a matched filter process on the second unique word and is included in the second received signal frequency-compensated by the frequency error compensation circuit 28. The channel matrix component h ₂₂ which means the ratio of the second transmission signal to be extracted is extracted. The first unique word and the second uniword are selected so as to have a low correlation with each other.

  Matched filter processing for a unique word is a process for obtaining a correlation between a unique word and an input signal, and an extremely high correlation value is output during a period in which the target unique word is included in the input signal. A low correlation value is output during a period other than. Therefore, the propagation path matrix can be extracted by detecting the amplitude phase of this high correlation value and determining the threshold value. In the prior art, matched filter processing is performed at a stage where the frequency error is not compensated for, so that the propagation path matrix cannot be detected correctly was a cause of deterioration of the interference compensation characteristics. Since the frequency error of the transmission signal on the side including the target unique word is ideally completely compensated, a correct channel matrix can be detected.

  The MMSE circuit 36 is provided when further interference compensation is performed by MMSE (Minimum Mean Squared Error) processing. Finally, the interference compensation circuit 300 is based on the propagation path matrix and receives the first reception signal and the second reception signal. From the signal, a first transmission restoration signal obtained by restoring the first transmission signal and a second transmission restoration signal obtained by restoring the second transmission signal are output, and the demodulation circuit 33 demodulates the first transmission restoration signal. The demodulation circuit 34 performs demodulation processing of the second transmission restoration signal. As described above, in the present invention, propagation path estimation is performed in a state where the influence of the frequency error is eliminated, so that interference can be compensated with high accuracy, and thus the signals are demodulated correctly in the demodulation circuits 33 and 34.

Note that it is not always necessary to use a transmission signal as shown in FIG. 4 for frequency error detection. For example, as shown in FIG. 5, if the first transmission restoration signal output from the interference compensation circuit 300 and the second transmission restoration signal are fed back and supplied to the reception frequency error detection circuit 200, the first transmission restoration is performed. Δf ₁ can be detected from the signal and Δf ₂ can be detected from the second transmission restoration signal. Also, a multi-carrier receiver is provided to detect the frequency error of each carrier, and the multi-carrier receiver notifies the frequency error to the frequency error compensation circuits 25, 26, 27, and 28 of the respective wireless receivers. May be.

It is a block diagram of the radio | wireless communications system by this invention. 1 is a configuration diagram of a conventional wireless communication system that transmits and receives signals having the same frequency shared by a plurality of transmission / reception antennas. It is a figure explaining the problem by a prior art. It is a figure which shows the format of a signal. It is a figure which shows other embodiment of the radio | wireless receiver by this invention.

Explanation of symbols

11, 12, 40, 41 Modulation circuit 13, 14, 21, 22, 42, 43, 48, 49 Frequency conversion circuit 15, 16, 35, 56, 57 Oscillation circuit 17, 18, 44, 45 Transmitting antenna 19, 20 , 46, 47 Reception antenna 23, 24, 50, 51 Frequency error detection circuit 25, 26, 27, 28, 52, 53 Frequency error compensation circuit 29, 30, 31, 32 Unique word matched filter 33, 34, 54, 55 Demodulation circuit 36 MMSE circuit 58 Averaging circuit 59 Interference compensation circuit 200 Reception frequency error detection circuit 300 Interference compensation circuit

Claims (5)

A first transmission radio signal obtained by frequency-converting the first transmission signal;
The first transmission radio signal is a radio reception apparatus that receives a second transmission radio signal that is orthogonally polarized and is frequency-converted from the second transmission signal,
A first receiving antenna;
A second receiving antenna;
First reception frequency conversion means for converting the frequency of the first reception radio signal received by the first reception antenna and outputting the first reception signal;
The second reception radio signal received by the second reception antenna is frequency-converted using the same oscillation means used by the first reception frequency conversion means, and the second reception signal is output. Receiving frequency conversion means,
The first frequency error received by the first transmission signal included in the first and second reception signals and the second frequency error received by the second transmission signal included in the first and second reception signals A frequency error detecting means for detecting
First frequency error compensation means for performing frequency compensation of the first received signal based on the first frequency error;
Second frequency error compensation means for performing frequency compensation of the second received signal based on the first frequency error;
Third frequency error compensation means for performing frequency compensation of the first received signal based on the second frequency error;
Fourth frequency error compensation means for performing frequency compensation of the second received signal based on the second frequency error;
A propagation path matrix is calculated based on the outputs of the first, second, third and fourth frequency error compensating means, and the first transmission signal and the first transmission signal are calculated from the first reception signal and the second reception signal based on the propagation path matrix. Interference compensation means for restoring the second transmission signal;
A radio receiving apparatus comprising: Each of the first transmission signal and the second transmission signal includes a section where there is no signal,
The first frequency error is detected from the first reception signal and / or the second reception signal in a section where the first transmission signal is not a no-signal and the second transmission signal is a no-signal,
The second frequency error is detected from the first reception signal and / or the second reception signal in a section where the first transmission signal is no signal and the second transmission signal is not a signal. The wireless receiver according to claim 1.   The radio reception apparatus according to claim 1, wherein the frequency error detection unit detects the first frequency error and the second frequency error based on the signal restored by the interference compensation unit. The first transmission signal includes a first unique word;
The second transmission signal includes a second unique word;
The interference compensation means includes a correlation between the output of the first frequency error compensation means and the first unique word, a correlation between the output of the second frequency error compensation means and the first unique word, and a third frequency error compensation means. Calculating a channel matrix based on the correlation between the output of the second unique word and the correlation between the output of the fourth frequency error compensation means and the second unique word;
The wireless receiver according to claim 1, wherein A wireless communication system comprising the wireless reception device according to any one of claims 1 to 4 and a wireless transmission device,
The wireless transmission device
First transmission frequency converting means for converting the frequency of the first transmission signal;
Second transmission frequency conversion means for converting the frequency of the second transmission signal using oscillation means different from the first transmission frequency conversion means;
A first transmission antenna for transmitting the first transmission signal after frequency conversion as a first transmission radio signal;
A second transmission antenna that transmits the second transmission signal after frequency conversion as a second transmission radio signal having a polarization orthogonal to the first transmission radio signal;
A wireless communication system comprising:

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