JP2009218718A - Transmitter and receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve communication characteristics when transmission antennas are highly correlated, by spreading and multiplexing transmission signals by a rotation orthogonal code having a rotation angle as an adjustment parameter. <P>SOLUTION: The transmitter includes: a rotation code multiplier 5 for calculating two spread multiplexed signals r<SB>1</SB>and r<SB>2</SB>by spreading and multiplexing two input signals s<SB>1</SB>and s<SB>2</SB>by the rotation orthogonal code having the rotation angle θ as the adjustment parameter; and a radio transmission means for simultaneously transmitting the two spread multiplexed signals r<SB>1</SB>and r<SB>2</SB>separately to the two transmission antennas Tx#1 and Tx#2 at the same frequency. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transmitter and a receiver of a MIMO wireless communication system.

  In recent years, a MIMO wireless communication system using a multiple input multiple output (MIMO) technique has been studied as a means for realizing high-speed and highly reliable wireless communication. The MIMO wireless communication system is characterized by transmitting a plurality of signals from a plurality of antennas at the same frequency at the same time. As a typical scheme of the MIMO wireless communication system, for example, a space time coding (STC) scheme, a spatial multiplexing (SM) scheme, and the like are known.

FIG. 14 shows a configuration of transmitter 100 in a conventional SM-type MIMO wireless communication system. In FIG. 14, an error correction encoder 2 performs error correction encoding on input transmission data. The symbol mapper (modulator) 3 maps the bit string of the error correction encoded data to the modulation symbol. For example, QPSK (Quadrature Phase Shift Keying) modulation method is used and mapped to QPSK modulation symbols. The bit string of the modulation symbol data is converted into parallel signals s ₁ and s ₂ by the serial / parallel converter 4. One signal _{s 1} is transmission antenna Tx # OFDM provided corresponding to 1: input to the (Orthogonal Frequency Division Multiplexing orthogonal frequency division multiplexing) modulator 6-1. The other signal _{s 2} is input to the OFDM modulator 6-2 provided corresponding to the transmission antenna Tx # 2. The OFDM modulators 6-1 and 6-2 modulate the input signal by an orthogonal frequency division multiplexing method. The signal after OFDM modulation is transmitted from each of the transmission antennas Tx # 1 and Tx # 2. According to this SM system, the transmission rate can be improved.

  In general, it is known that a MIMO wireless communication system can obtain good communication characteristics in a low-correlation environment, that is, in a multipath rich environment. For this reason, when the correlation between transmitting antennas is high, the communication characteristics deteriorate. This point will be described with reference to FIGS. 15 and 16 show examples of constellation (signal point arrangement) when the QPSK modulation method is used. FIG. 15 shows an example when the correlation between the transmission antennas is low, and FIG. 16 shows an example when the correlation between the transmission antennas is high.

  In FIG. 15 (when the correlation between the transmission antennas is low), the constellation Con-A of the signal transmitted from the transmission antenna Tx # 1 is constellation Con when reaching the receiver under the influence of the radio propagation path. -B. The constellation Con-C of the signal transmitted from the transmission antenna Tx # 2 is the constellation Con-D when reaching the receiver under the influence of the radio propagation path. Thereby, the signal received by the receiver becomes constellation Con-E. When the correlation between the transmitting antennas is low, as shown in the constellation Con-E in FIG. 15, the 16 received symbol points are arranged without being overlapped and can be identified.

  In FIG. 16 (when the correlation between the transmission antennas is high), the constellation Con-A of the signal transmitted from the transmission antenna Tx # 1 is constellation Con when it reaches the receiver under the influence of the radio propagation path. -B. The constellation Con-C of the signal transmitted from the transmission antenna Tx # 2 is the constellation Con-D when reaching the receiver under the influence of the radio propagation path. Thereby, the signal received by the receiver becomes constellation Con-E. However, when the correlation between the transmission antennas is high, a plurality of reception symbol points (inner reception symbol points surrounded by broken lines in FIG. 16) overlap as shown in constellation Con-E in FIG. Therefore, it is difficult to accurately identify the 16 received symbol points. This occurs because when the correlation between the transmission antennas is high, when the signals transmitted from the plurality of transmission antennas are mixed, the distance between the symbol points of each transmission signal becomes extremely short. The correlation between transmission antennas tends to be high when the transmission antenna interval is narrow or in a LOS (Line of Sight) environment.

  For example, a “Precoding MIMO” technique is known as one of countermeasures against communication characteristic degradation when the correlation between transmission antennas is high. In the “Precoding MIMO” technique, deterioration of communication characteristics is suppressed by multiplying a unitary matrix or the like before transmission. However, in order to determine what kind of matrix (Precoder) is used on the transmission side, it is necessary to receive feedback of radio propagation path information from the reception side, which causes an increase in network load and communication delay.

On the other hand, Patent Document 1 discloses a technique for adjusting a frequency diversity effect in a multicarrier transmission system. In the technique described in Patent Document 1, a transmission signal is spread and multiplexed by a rotation orthogonal code having a rotation angle as an adjustment parameter.
International Publication No. 2007/000964 Pamphlet

  However, the above-described conventional “Precoding MIMO” technique has a problem of an increase in network load and communication delay in order to feed back radio propagation path information from the reception side to the transmission side. On the other hand, if the technique described in Patent Document 1 is applied to cope with the high correlation between transmitting antennas, the problem of increase in network load and communication delay can be solved.

  The present invention has been made in consideration of such circumstances, and the object of the present invention is to perform the case where the correlation between the transmission antennas is high by spreading and multiplexing the transmission signal by the rotation orthogonal code having the rotation angle as an adjustment parameter. An object of the present invention is to provide a transmitter and a receiver of a MIMO wireless communication system capable of improving communication characteristics.

In order to solve the above problems, a transmitter according to the present invention is a transmitter of a MIMO wireless communication system, and N (N = 2 ^m , m is an integer of 1 or more) by a rotating orthogonal code having a rotation angle as an adjustment parameter. ) Rotating orthogonal code spread multiplexing means for calculating N spread multiplexed signals by spreading and multiplexing the N input signals, and dividing the N spread multiplexed signals into N transmit antennas and transmitting them simultaneously at the same frequency And a wireless transmission means.

  The transmitter according to the present invention is characterized by comprising rotation angle control means for controlling the rotation angle.

  In the transmitter according to the present invention, the rotation angle control means changes the rotation angle according to a coding rate and a modulation method of the input signal.

  The transmitter according to the present invention is characterized by comprising storage means for holding the set value of the rotation angle for each combination of coding rate and modulation method.

  In the transmitter according to the present invention, when the N is 2, and the input signal has a QPSK modulation scheme and a coding rate of “1/3”, the rotation angle is 0.5 × π / 4. To 0.9 × π / 4 radians.

  In the transmitter according to the present invention, when the N is 2, and the input signal has a QPSK modulation scheme and a coding rate of “½”, the rotation angle is 0.3 × π / 4. To 0.7 × π / 4 radians.

  In the transmitter according to the present invention, when the N is 2, and the input signal has a QPSK modulation scheme and a coding rate of “2/3”, the rotation angle is 0.2 × π / 4. And 0.6 × π / 4 radians.

  In the transmitter according to the present invention, when the N is 2, and the input signal has a QPSK modulation scheme and a coding rate of “3/4”, the rotation angle is 0.2 × π / 4. And 0.6 × π / 4 radians.

  In the transmitter according to the present invention, when the N is 2, and the input signal has a QPSK modulation scheme and a coding rate of “1”, the rotation angle ranges from 0.1 × π / 4 to 0. The value is up to 5 × π / 4 radians.

  In the transmitter according to the present invention, when the N is 2, and the input signal has a 16QAM modulation scheme and a coding rate of “1/3”, the rotation angle is 0.6 × π / 4. To 1.0 × π / 4 radians.

  In the transmitter according to the present invention, when the N is 2, and the input signal has a 16QAM modulation scheme and a coding rate of “1/2”, the rotation angle is 0.6 × π / 4. To 1.0 × π / 4 radians.

  In the transmitter according to the present invention, when the N is 2, and the input signal has a 16QAM modulation scheme and a coding rate of “2/3”, the rotation angle is 0.6 × π / 4. To 1.0 × π / 4 radians.

  In the transmitter according to the present invention, when the N is 2, and the input signal has a 16QAM modulation scheme and a coding rate of “3/4”, the rotation angle is 0.4 × π / 4. To 0.8 × π / 4 radians.

  In the transmitter according to the present invention, when the N is 2, and the input signal has a 16QAM modulation scheme and a coding rate of “1”, the rotation angle is 0.2 × π / 4 to 0. It is a value up to .6 × π / 4 radians.

  The receiver according to the present invention is a receiver of a MIMO wireless communication system, wireless receiving means for receiving signals of the same frequency by a plurality of receiving antennas, and transmission path estimating means for performing transmission path estimation processing based on pilot signals. A symbol replica that obtains a reception reference reference point by applying the transmission path estimation processing result to a known pilot signal that is spread-multiplexed by the same rotational orthogonal code as that used for spread-multiplexing of the transmission signal in the transmitter And a reception processing unit configured to determine reception points from signals received by the plurality of reception antennas based on the reception reference reference points.

  The receiver according to the present invention is characterized by comprising rotation angle control means for controlling the rotation angle in accordance with the transmitter.

  According to the present invention, it is possible to improve the communication characteristics when the correlation between the transmission antennas is high by spreading and multiplexing the transmission signal with the rotation orthogonal code having the rotation angle as the adjustment parameter.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a transmitter 1 of an SM-type MIMO wireless communication system according to an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of the receiver 20 of the SM-type MIMO wireless communication system according to the embodiment.

First, the transmitter 1 according to the present embodiment will be described with reference to FIG.
In FIG. 1, an error correction encoder 2 performs error correction encoding on input transmission data. The symbol mapper (modulator) 3 maps the bit string of the error correction encoded data to the modulation symbol. In this embodiment, a QPSK modulation method or a 16-QAM (16-positions Quadrature Amplitude Modulation) modulation method is used as the modulation method.

The bit string of the modulated symbol data after the output of the symbol mapper 3 is converted into parallel signals s ₁ and s ₂ by the serial / parallel converter 4. The parallel signals s ₁ and s ₂ are input to the rotation code multiplier 5. The rotation code multiplier 5 multiplies the parallel signals s ₁ and s ₂ by the rotation orthogonal code, and outputs spread multiplexed signals r ₁ and r ₂ as multiplication results.

  The OFDM modulators 6-1 and 6-2 and the multiplexers 7-1 and 7-2 are provided corresponding to each of the two transmission antennas Tx # 1 and Tx # 2. As a result, the first wireless transmission system including the OFDM modulator 6-1, the multiplexer 7-1, and the transmission antenna Tx # 1, and the transmission antenna Tx # of the OFDM modulator 6-2, the multiplexer 7-2. And a second wireless transmission system consisting of two.

One output signal r ₁ of the rotary code multiplier 5 is input to the OFDM modulator 6-1 of the first radio transmission system. OFDM modulator 6-1 modulates the input signal _{r 1} by the OFDM method. The multiplexer 7-1 time-multiplexes a predetermined pilot signal with respect to the OFDM modulated signal. The multiplexed signal output from the multiplexer 7-1 is transmitted from the transmission antenna Tx # 1. The output signal r ₂ of the other rotary code multiplier 5 is input to the OFDM modulator 6-2 of the second radio transmission systems. OFDM modulator 6-2 modulates the input signal _{r 2} by the OFDM method. The multiplexer 7-2 time-multiplexes a predetermined pilot signal with respect to the OFDM modulated signal. The multiplexed signal output from the multiplexer 7-2 is transmitted from the transmission antenna Tx # 2. As a result, the two spread multiplexed signals r ₁ and r ₂ are transmitted to the two transmission antennas Tx # 1 and Tx # 2 and simultaneously transmitted at the same frequency.

  The rotation angle controller 8 instructs the rotation code multiplier 5 on the rotation angle θ of the rotation orthogonal code. The rotation angle controller 8 receives information on the coding rate R from the error correction encoder 2. This information indicates the coding rate R used in the error correction encoder 2. Further, the rotation angle controller 8 receives the modulation method information A from the symbol mapper 3. The modulation scheme information A indicates the modulation scheme used by the symbol mapper 3. The rotation angle controller 8 reads the set value of the rotation angle θ from the rotation angle table 9 based on the coding rate R and the modulation method information A. The rotation angle table 9 stores a set value of the rotation angle θ for each combination of coding rate and modulation method.

The rotation code multiplier 5 applies the rotation orthogonal code of the rotation angle θ indicated by the rotation angle controller 8 to the parallel signals s ₁ and s ₂ . Thus, rotation orthogonal code of the rotation angle θ corresponding to the coding rate R and the modulation scheme of the parallel signals s _1, s ₂ is applied to said parallel signals s _1, s _2.

In the transmitter 1 of FIG. 1 described above, _two spread multiplexed signals r ₁ and r ₂ obtained by spreading and multiplexing the input signals s ₁ and s ₂ using a rotation orthogonal code having the rotation angle θ as an adjustment parameter are represented by 2 The transmission antennas Tx # 1 and Tx # 2 are simultaneously transmitted at the same frequency. In that case, it is configured such that an appropriate rotation angle θ according to the coding rate R and the modulation method of the input signals s ₁ and s ₂ can be given.

Next, the receiver 20 according to the present embodiment will be described with reference to FIG.
As shown in FIG. 2, the receiver 20 includes a rotation angle controller 8 and a rotation angle table 9 as in the transmitter 1. In FIG. 2, the receiver 20 has two receiving antennas Rx # 1 and Rx # 2. Separators 21-1 and 21-2 and OFDM demodulators 22-1 and 22-2 are provided corresponding to each of the two receiving antennas Rx # 1 and Rx # 2. Thus, from the first radio reception system including the reception antenna Rx # 1, the separator 21-1, and the OFDM demodulator 22-1, the reception antenna Rx # 2, the separator 21-2, and the OFDM demodulator 22-2. And a second radio receiving system.

  The reception signal received by one reception antenna Rx1 is input to the separator 20-1. Separator 20-1 separates the time-multiplexed pilot signal from the received signal. The separated pilot signal is input to the transmission path estimator 25. The OFDM demodulator 21-1 performs OFDM demodulation on the received signal after the pilot signal separation. This OFDM demodulated signal is input to a maximum likelihood estimation (MLD) unit 23. The received signal received by the other receiving antenna Rx2 is input to the separator 20-2. Separator 20-2 separates the time-multiplexed pilot signal from the received signal. The separated pilot signal is input to the transmission path estimator 25. The OFDM demodulator 21-2 performs OFDM demodulation on the received signal after the pilot signal separation. This OFDM demodulated signal is input to the maximum likelihood estimator 23.

  The maximum likelihood estimator 23 performs SM-type reception processing and symbol demapping on the OFDM demodulated signal to obtain a soft decision value. Here, the maximum likelihood estimator 23 receives the received symbol reference standard point from the symbol replica generator 26, and softly determines the received symbol point based on the reference standard point. The error correction decoder 24 performs error correction decoding on the soft decision value.

  The transmission path estimator 25 performs transmission path estimation processing based on the pilot signal. The symbol replica generator 26 calculates a reference reference point of the received symbol based on the transmission path estimation processing result. Here, the symbol replica generator 26 receives an instruction of the rotation angle θ from the rotation angle controller 8, multiplies the known pilot signal by the rotation orthogonal code of the rotation angle θ, and applies the result of the multiplication to the pilot signal. The received symbol reference reference point is obtained by applying the transmission path estimation processing result. The symbol replica generator 26 has a rotation code multiplier similar to the rotation code multiplier 5 of FIG.

  The rotation angle controller 8 receives the modulation method information A from the maximum likelihood estimator 23. Further, the rotation angle controller 8 receives information on the coding rate R from the error correction decoder 24. The rotation angle controller 8 and the rotation angle table 9 are the same as those of the transmitter 1 described above, and the setting value of the rotation angle θ included in the rotation angle table 9 is the same as that of the transmitter 1. The rotation angle controller 8 acquires the set value of the rotation angle θ corresponding to the modulation scheme information A from the maximum likelihood estimator 23 and the coding rate R from the error correction decoder 24 from the rotation angle table 9, and The angle θ is indicated to the symbol replica generator 26. As a result, the received symbol reference reference point calculated by the symbol replica generator 26 is obtained by applying a rotation orthogonal code having a rotation angle θ corresponding to the corresponding coding rate R and modulation scheme.

  In the receiver 20 of FIG. 2 described above, the received symbol reference reference point is obtained by the same rotational orthogonal code used in the transmitter 1 for spreading multiplexing of the transmission signal. At this time, the rotation angle θ corresponding to the transmission signal can be given.

  Although the above-described receiver 20 uses maximum likelihood estimation (MLD), a soft decision value may be obtained using a linear filter or the like.

Next, the rotation orthogonal code according to the present embodiment will be described.
The rotation orthogonal code of the rotation angle θ according to the present embodiment is shown in equation (1). In the equation (1), the rotation orthogonal code is represented as a rotation matrix of the rotation angle θ.

In the rotation code multiplier 5 in FIG. 1 and the rotation code multiplier in the symbol replica generator 26 in FIG. ₂ , the rotation angle θ is rotated with respect to the input signals s ₁ and s ₂ as shown in the equation (1). The result of multiplying the orthogonal code is the output signals r ₁ and r ₂ . For example, in the transmitter 1 of FIG. 1, the bit string of the signal s ₁ output in parallel from the serial-to-parallel converter 4 is “s ₁₁ , s ₁₂ , s ₁₃ ,...”, And the bit string of the signal s ₂ is “s _21. , _{s 22, s} 23, When ... ", the bit string" _r 11 of the signal _{r 1} that is parallel output from the rotation code multiplier _5, r _{12, r} 13,... ", the bit string of the signal _{r 2} ' “r ₂₁ , r ₂₂ , r ₂₃ ,...

Next, the setting range of the rotation angle θ according to this embodiment will be described.
The rotation angle θ is expressed by equation (5).
θ = x × π / 4 (5)
However, the unit of the rotation angle θ is radians. x is a variable and is a value corresponding to a combination of a coding rate and a modulation method.

  FIG. 3 shows a setting range of the value of the variable x in equation (5) in combination with each coding rate R when the QPSK modulation method and the 16QAM modulation method are adopted as the modulation method.

[Setting range of variable x in case of QPSK modulation method]
In the case of the QPSK modulation method, the value of the variable x is set as follows from the setting range shown in FIG.
When the coding rate R is “1/3”, the value of the variable x is set from a range of 0.5 to 0.9.
When the coding rate R is “1/2”, the value of the variable x is set from a range of 0.3 to 0.7.
When the coding rate R is “2/3”, the value of the variable x is set from a range of 0.2 to 0.6.
When the coding rate R is “3/4”, the value of the variable x is set from the range of 0.2 to 0.6.
When the coding rate R is “1”, the value of the variable x is set from a range from 0.1 to 0.5.

[Setting range of variable x in case of 16QAM modulation system]
In the case of the 16QAM modulation system, the value of the variable x is set as follows from the setting range shown in FIG.
When the coding rate R is “1/3”, the value of the variable x is set from a range of 0.6 to 1.0.
When the coding rate R is “1/2”, the value of the variable x is set from the range of 0.6 to 1.0.
When the coding rate R is “2/3”, the value of the variable x is set from the range of 0.6 to 1.0.
When the coding rate R is “3/4”, the value of the variable x is set from a range of 0.4 to 0.8.
When the coding rate R is “1”, the value of the variable x is set from a range of 0.2 to 0.6.

  In the present embodiment, the value of the variable x is set from the range shown in FIG. 3 for the rotation angle table 9 of FIGS. Therefore, the value of the variable x is selected from the set range in FIG. 3 for each combination of the QPSK modulation method and each coding rate R, and stored in the rotation angle table 9. Similarly, the value of the variable x is selected from the setting range in FIG. 3 for each combination of the 16QAM modulation method and each coding rate R, and stored in the rotation angle table 9. The rotation angle table 9 is created in advance.

4 to 13 show data obtained by verifying the setting range of the variable x shown in FIG. 3 for each of the QPSK modulation method and the 16QAM modulation method with respect to the rotation angle θ according to the present embodiment.
The graphs of FIGS. 4 to 13 are packet error rates measured by reproducing the MIMO wireless communication system composed of the transmitter 1 of FIG. 1 and the receiver 20 of FIG. 2 by simulation and changing the value of the variable x. Indicates. In this measurement, the average received energy to noise power density ratio (Es / N0) per symbol is fixed. The correlation value between the transmitting antennas and the correlation value between the receiving antennas are both 0.9. Even when the correlation value between the transmission antennas or the correlation value between the reception antennas was changed, the verification result was the same.

[Verification results for QPSK modulation method]
FIG. 4 shows a case where the modulation scheme is the QPSK modulation scheme and the coding rate R is “1/3”. As shown in FIG. 4, the packet error rate is relatively good when the value of the variable x is in the range of 0.5 to 0.9.
FIG. 5 shows a case where the modulation scheme is the QPSK modulation scheme and the coding rate R is “1/2”. As shown in FIG. 5, the packet error rate is relatively good when the value of the variable x is in the range of 0.3 to 0.7.
FIG. 6 shows a case where the modulation scheme is the QPSK modulation scheme and the coding rate R is “2/3”. As shown in FIG. 6, the packet error rate is relatively good when the value of the variable x is in the range of 0.2 to 0.6.
FIG. 7 shows a case where the modulation scheme is the QPSK modulation scheme and the coding rate R is “3/4”. As shown in FIG. 7, the packet error rate is relatively good when the value of the variable x is in the range of 0.2 to 0.6.
FIG. 8 shows a case where the modulation scheme is the QPSK modulation scheme and the coding rate R is “1”. As shown in FIG. 8, the packet error rate is relatively good when the value of the variable x is in the range of 0.1 to 0.5.

[Verification result in the case of 16QAM modulation system]
FIG. 9 shows a case where the modulation scheme is the 16QAM modulation scheme and the coding rate R is “1/3”. As shown in FIG. 9, the packet error rate is relatively good when the value of the variable x is in the range of 0.6 to 1.0.
FIG. 10 shows a case where the modulation scheme is the 16QAM modulation scheme and the coding rate R is “½”. As shown in FIG. 10, the packet error rate is relatively good when the value of the variable x is in the range of 0.6 to 1.0.
FIG. 11 shows a case where the modulation scheme is the 16QAM modulation scheme and the coding rate R is “2/3”. As shown in FIG. 11, the packet error rate is relatively good when the value of the variable x is in the range of 0.6 to 1.0.
FIG. 12 shows a case where the modulation scheme is the 16QAM modulation scheme and the coding rate R is “3/4”. As shown in FIG. 12, the packet error rate is relatively good when the value of the variable x is in the range of 0.4 to 0.8.
FIG. 13 shows a case where the modulation scheme is the 16QAM modulation scheme and the coding rate R is “1”. As shown in FIG. 13, the packet error rate is relatively good when the value of the variable x is in the range of 0.2 to 0.6.

  As described above, according to the present embodiment, two spread multiplexed signals are calculated by spreading and multiplexing two input signals using a rotation orthogonal code having the rotation angle θ as an adjustment parameter. Then, the two spread multiplexed signals are divided into two transmission antennas and simultaneously transmitted at the same frequency. At this time, by providing an appropriate rotation angle θ according to the coding rate and modulation method of the input signal, it is possible to improve the communication characteristics when the correlation between the transmission antennas is high. As a result, it is not necessary to feed back the radio propagation path information from the reception side to the transmission side, and the problems of increase in network load and communication delay are solved.

As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.
For example, although two transmission antennas are used in the above-described embodiment, the number of transmission antennas may be four or more (provided that the number N of transmission antennas is a power of 2). A rotation orthogonal code G _N (where N = 2 ⁿ , where n is an integer of 2 or more) when the number N of transmission antennas is 4 or more is expressed by Expression (6). Note that the rotational orthogonal code G ₂ when the number N of transmission antennas is 2 (N = 2 ¹ ) is expressed by Equation (7). Further, when the number N of transmission antennas is 4 (N = 2 ² ), the rotation orthogonal code G ₄ is expressed by equation (8).

Thus, the present invention is applicable when the number of transmitting antennas N is a power of 2 (N = 2 ^m , where m is an integer equal to or greater than 1).

It is a block diagram which shows the structure of the transmitter 1 of the SM system MIMO radio | wireless communications system which concerns on one Embodiment of this invention. 2 is a block diagram showing a configuration of a receiver 20 of the SM-type MIMO wireless communication system according to the embodiment. FIG. This is a setting range of the variable x corresponding to the rotation angle θ according to the embodiment. It is verification data of the setting range of the variable x shown in FIG. It is verification data of the setting range of the variable x shown in FIG. It is verification data of the setting range of the variable x shown in FIG. It is verification data of the setting range of the variable x shown in FIG. It is verification data of the setting range of the variable x shown in FIG. It is verification data of the setting range of the variable x shown in FIG. It is verification data of the setting range of the variable x shown in FIG. It is verification data of the setting range of the variable x shown in FIG. It is verification data of the setting range of the variable x shown in FIG. It is verification data of the setting range of the variable x shown in FIG. It is a block diagram which shows the structure of the transmitter 100 in the conventional MIMO radio communication system of SM system. This is a constellation when the correlation between transmitting antennas in a conventional SM-type MIMO wireless communication system is low. This is a constellation when the correlation between transmitting antennas in a conventional SM-type MIMO wireless communication system is high.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transmitter, 5 ... Rotation code multiplier (rotation orthogonal code spreading | diffusion multiplexing means), 6-1, 6-2 ... OFDM modulator (radio transmission means), 7-1, 7-2 ... Multiplexer (radio transmission) Means), 8 ... Rotation angle controller, 9 ... Rotation angle table, Tx # 1, Tx # 2 ... Transmission antenna (radio transmission means), 20 ... Receiver, Rx # 1, Rx # 2 ... Reception antenna (radio reception) Means), 21-1, 21-2 ... separator (radio reception means), 22-1, 22-2 ... OFDM demodulator (radio reception means), 23 ... maximum likelihood estimator (reception processing means), 25 ... Transmission path estimator, 26 ... symbol replica generator

Claims (16)

In a transmitter of a MIMO wireless communication system,
Rotating orthogonal code spread multiplexing that calculates N spread multiplexed signals by spreading and multiplexing N (N = 2 ^m , m is an integer equal to or greater than 1) input signals with a rotation orthogonal code having a rotation angle as an adjustment parameter. Means,
Wireless transmission means for dividing the N spread multiplexed signals into N transmission antennas and transmitting them simultaneously at the same frequency;
A transmitter characterized by comprising:   The transmitter according to claim 1, further comprising a rotation angle control unit that controls the rotation angle.   The transmitter according to claim 2, wherein the rotation angle control means changes the rotation angle in accordance with a coding rate and a modulation method of the input signal.   4. The transmitter according to claim 3, further comprising storage means for holding a set value of the rotation angle for each combination of a coding rate and a modulation method. In the case where N is 2,
When the input signal has a QPSK modulation scheme and a coding rate of “1/3”, the rotation angle has a value from 0.5 × π / 4 to 0.9 × π / 4 radians. The transmitter according to any one of claims 1 to 4. In the case where N is 2,
When the input signal has a QPSK modulation scheme and a coding rate of “1/2”, the rotation angle is a value from 0.3 × π / 4 to 0.7 × π / 4 radians. The transmitter according to any one of claims 1 to 4. In the case where N is 2,
When the input signal has a QPSK modulation scheme and a coding rate of “2/3”, the rotation angle is a value from 0.2 × π / 4 to 0.6 × π / 4 radians. The transmitter according to any one of claims 1 to 4. In the case where N is 2,
When the input signal has a QPSK modulation scheme and a coding rate of “3/4”, the rotation angle is a value from 0.2 × π / 4 to 0.6 × π / 4 radians. The transmitter according to any one of claims 1 to 4. In the case where N is 2,
The rotation angle is a value from 0.1 × π / 4 to 0.5 × π / 4 radians when the input signal has a QPSK modulation scheme and a coding rate of “1”. The transmitter according to any one of claims 1 to 4. In the case where N is 2,
When the input signal is a 16QAM modulation system and a coding rate is “1/3”, the rotation angle is a value from 0.6 × π / 4 to 1.0 × π / 4 radians. The transmitter according to any one of claims 1 to 4. In the case where N is 2,
When the input signal is a 16QAM modulation system and a coding rate is “1/2”, the rotation angle is a value from 0.6 × π / 4 to 1.0 × π / 4 radians. The transmitter according to any one of claims 1 to 4. In the case where N is 2,
When the input signal is a 16QAM modulation system and a coding rate is “2/3”, the rotation angle is a value from 0.6 × π / 4 to 1.0 × π / 4 radians. The transmitter according to any one of claims 1 to 4. In the case where N is 2,
When the input signal has a 16QAM modulation method and a coding rate of “3/4”, the rotation angle has a value from 0.4 × π / 4 to 0.8 × π / 4 radians. The transmitter according to any one of claims 1 to 4. In the case where N is 2,
The rotation angle is a value from 0.2 × π / 4 to 0.6 × π / 4 radians when the input signal has a 16QAM modulation scheme and a coding rate of “1”. The transmitter according to any one of claims 1 to 4. In a receiver of a MIMO wireless communication system,
Wireless receiving means for receiving signals of the same frequency by a plurality of receiving antennas;
Transmission path estimation means for performing transmission path estimation processing based on the pilot signal;
Symbol replica generation for obtaining a reception reference reference point by applying the result of the transmission path estimation processing to a known pilot signal spread-multiplexed by the same rotational orthogonal code as that used for spread-multiplexing of a transmission signal in a transmitter Means,
Reception processing means for determining a reception point from signals received by the plurality of reception antennas based on the reception reference reference point;
A receiver comprising:   The receiver according to claim 15, further comprising a rotation angle control unit that controls the rotation angle according to the transmitter.

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