JP2010141812A - Receiver, and receiving method - Google Patents

Abstract

Kind Code: A1 In an OFDM-MIMO wireless communication system that performs simultaneous communication combining a OFDM method and a MIMO method between a plurality of base stations and one wireless terminal, each of the antennas between the antenna of each base station and the antenna of the wireless terminal is provided. To cope with the difference in radio wave propagation distance and to prevent deterioration of bit error rate.
A replica generator 16 that generates a replica signal for each base station for each subcarrier of the OFDM system, and a propagation time of an incoming wave from a base station other than the reference base station with respect to an incoming wave from the reference base station The phase difference corresponding to the detected arrival wave time difference is shifted for each sub-carrier of the OFDM scheme with respect to the replica signal associated with the base station other than the reference base station and the arrival wave detector 18 for detecting the difference between A phase shifter 19 and an MLD detector 14 that performs reception processing of the MIMO scheme using the subcarrier reception signal and the phase-replicated replica signal are provided for each OFDM scheme subcarrier.
[Selection] Figure 2

Description

  The present invention relates to a receiver and a receiving method in a wireless communication system using a multiple input multiple output (MIMO) technique.

  Conventionally, the MIMO technology is known as one of the technologies for improving the frequency utilization efficiency of a wireless communication system. FIG. 5 shows a basic conceptual diagram of a MIMO wireless communication system. In FIG. 5, a transmitting station wirelessly transmits different data signals from a plurality of transmitting antennas at the same frequency. The receiving station receives and restores the transmitted radio signal by a plurality of receiving antennas. At the time of restoration, if the channel matrix H is ideally known, the transmission signal can be separated by multiplying the reception signal by the inverse matrix of the channel matrix H. As shown in the example of FIG. When different data signals are transmitted from the transmission antennas, data communication can be performed at a maximum speed of four times. Thereby, the frequency utilization efficiency is improved.

Patent Document 1 discloses a MIMO wireless communication system that performs simultaneous communication by MIMO between a plurality of base stations and one wireless terminal. Patent Document 2 discloses an OFDM-MIMO wireless communication system that combines an Orthogonal Frequency Division Multiplexing (OFDM) system, which is one of multicarrier transmission systems, and a MIMO system. .
JP 2007-134844 A Special table 2008-523665 gazette

  When performing simultaneous communication combining the OFDM method and the MIMO method between one base station and one wireless terminal, the difference in radio wave propagation distance between each antenna of the base station and each antenna of the wireless terminal is generally In addition, it is fixed regardless of the position of the wireless terminal and is not so large as to adversely affect the bit error rate (BER) of the communication bit. However, when performing simultaneous communication combining a OFDM method and a MIMO method between a plurality of base stations and one wireless terminal, the difference in radio wave propagation distance between the antenna of each base station and the antenna of the wireless terminal However, it varies depending on the position of the wireless terminal, and can be large enough to cause deterioration of the bit error rate.

  The present invention has been made in view of such circumstances, and an object of the present invention is OFDM-MIMO wireless communication that performs simultaneous communication combining a OFDM method and a MIMO method between a plurality of base stations and one wireless terminal. It is an object of the present invention to provide a receiver and a receiving method capable of dealing with a difference in radio wave propagation distance between an antenna of each base station and an antenna of a wireless terminal and preventing deterioration of a bit error rate.

  In order to solve the above problems, a receiver according to the present invention provides a wireless communication system that performs simultaneous downlink communication using a combination of OFDM and MIMO between a plurality of base stations and one wireless terminal. In the receiver of the terminal, for each OFDM subcarrier, replica generation means for generating a replica signal for each base station, and propagation of incoming waves from base stations other than the reference base station for incoming waves from the reference base station An arrival wave time difference detection means for detecting a time difference, and a phase difference corresponding to the detected arrival wave time difference for each OFDM subcarrier with respect to a replica signal related to a base station other than the reference base station. Phase shift means, and for each OFDM scheme subcarrier, a MIMO scheme reception process using the subcarrier received signal and the phase-shifted replica signal. And it performs.

  The receiver according to the present invention includes an arrival wave power value detection unit that detects a reception power value of an arrival wave from each base station, and determines a reference base station based on the detected arrival wave power value It is characterized by.

  The receiver according to the present invention is characterized in that a main wave among a plurality of incoming waves coming from one base station is used for the detection.

  In the receiver according to the present invention, the reference base station is a base station having a maximum received power value of the main wave.

  The receiver according to the present invention includes propagation path estimation means for estimating the transfer function of the radio wave propagation path for each subcarrier using the received signal of each subcarrier, and the estimated transfer function for the replica signal. The phase-shifting means is provided in a step subsequent to the step of performing propagation path equalization using.

  The receiver according to the present invention includes propagation path estimation means for estimating the transfer function of the radio wave propagation path for each subcarrier using the received signal of each subcarrier, and the estimated transfer function for the replica signal. The phase-shifting means is provided in a step before the step of performing propagation path equalization using the.

  A receiving method according to the present invention is a receiving method of the wireless terminal in a wireless communication system that performs simultaneous downlink communication using a combination of OFDM and MIMO between a plurality of base stations and one wireless terminal, The step of generating a replica signal for each base station for each subcarrier of the system, and the difference in the propagation time (arrival time difference) of the arrival wave from the base station other than the reference base station with respect to the arrival wave from the reference base station A step of detecting, a step of shifting a phase difference corresponding to the detected arrival wave time difference for each subcarrier of the OFDM scheme with respect to a replica signal related to a base station other than the reference base station, And performing a MIMO reception process using a reception signal of a subcarrier and a replica signal after the phase shift for each carrier. To.

  According to the present invention, in an OFDM-MIMO radio communication system that performs simultaneous communication combining a OFDM scheme and a MIMO scheme between a plurality of base stations and one radio terminal, between the antenna of each base station and the antenna of the radio terminal. Thus, it is possible to deal with the difference in the respective radio wave propagation distances and to prevent the bit error rate from being deteriorated.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram showing a configuration of an OFDM-MIMO wireless communication system according to an embodiment of the present invention. The OFDM-MIMO wireless communication system shown in FIG. 1 combines an OFDM scheme and a MIMO scheme between a plurality of base stations 2 (two base stations # 1 and # 2 in the example of FIG. 1) and one wireless terminal 1. Simultaneous communication is performed. Each base station 2 is connected to the base station controller 3 via a communication line. The base station control device 3 is connected to the backbone network 4.

  Hereinafter, wireless communication in the downlink direction (direction from the base station 2 to the wireless terminal 3) will be described.

  The wireless terminal 1 performs simultaneous downlink communication combining the OFDM scheme and the MIMO scheme with the two base stations 2 (# 1, # 2). Each base station 2 (# 1, # 2) performs simultaneous downlink communication using cooperative MIMO. The base station control device 3 controls each base station 2 (# 1, # 2) and realizes cooperation between the base stations. Specifically, the base station controller 3 performs space-time coding (STC) and spatial multiplexing (SM) according to the radio wave reception environment (for example, received power) of the wireless terminal 1. ) And the data transmitted from each base station 2 (# 1, # 2) are changed.

  Each base station 2 (# 1, # 2) has an OFDM transmitter and one antenna, and transmits MIMO transmission data from one transmission antenna by OFDM according to the control of the base station controller 3. Wireless transmission. The base station 2 (# 1) wirelessly transmits MIMO transmission data from the antenna Ant1T using the OFDM scheme. The base station 2 (# 2) wirelessly transmits MIMO transmission data from the antenna Ant2T using the OFDM scheme.

  The wireless terminal 1 includes a receiver that performs OFDM-type reception processing and MIMO-type reception processing, and two antennas Ant1R and Ant2R, and is transmitted from each base station 2 (# 1, # 2). A signal is received by each of the antennas Ant1R and Ant2R, and an OFDM reception process and a MIMO reception process are performed.

  Next, some examples of the receiver included in the wireless terminal 1 according to the present embodiment will be described.

  FIG. 2 is Example 1 of the receiver 10 included in the wireless terminal 1 according to the present embodiment. In FIG. 2, a receiver 10 includes a CP (cyclic prefix) remover 11, a serial / parallel signal converter (S / P converter) 12, a discrete Fourier transformer (DFT) 13, an MLD (Maximum Likelihood). Detection) detector 14, propagation path estimator 15, replica generator 16, multiplier 17, incoming wave detector 18 and phase shifter 19. The CP remover 11, the S / P converter 12, and the DFT 13 are provided corresponding to each of the two antennas Ant1R and Ant2R. The MLD detector 14 is provided corresponding to each of the OFDM subcarriers (the number of subcarriers is n).

  The CP remover 11 removes the CP from the received signal received by the antenna connected to itself. The S / P converter 12 converts the received signal (serial signal) after CP removal into a parallel signal. The DFT 13 performs a discrete Fourier transform on the received signal after CP removal input as a parallel signal, and outputs a received signal of each subcarrier.

  The MLD detector 14 uses the reception signal of its own subcarrier input from each DFT 13 and the propagation path equalization / phase adjustment replica signal related to the subcarrier input from the phase shifter 19, to By detecting the OFDM symbol of the subcarrier transmitted by the base station 2 (# 1) and the OFDM symbol of the subcarrier transmitted by the base station 2 (# 2) by the likelihood estimation (MLD) method, An OFDM symbol detection signal 21 of the subcarrier related to base station 2 (# 1) and an OFDM symbol detection signal 22 of the subcarrier related to base station 2 (# 1) are output. The OFDM symbol detection signals 21-1 to 21-n of each subcarrier related to the base station 2 (# 1) and the OFDM symbol detection signals 21-1 to n of each subcarrier related to the base station 2 (# 2) are demodulated. (Not shown) and demodulated.

  The propagation path estimator 15 estimates the transfer function of the radio wave propagation path for each subcarrier using the received signal of each subcarrier input from each DFT 13. The replica generator 16 generates all OFDM symbols (replica signals) that can be transmitted from each base station 2 (# 1, # 2) for each subcarrier.

  The multiplier 17 is provided corresponding to each of the subcarriers. Each multiplier 17 receives the transfer function estimated by the propagation path estimator 15 and the replica signal generated by the replica generator 16 for each corresponding subcarrier. The multiplier 17 multiplies the transfer function and the replica signal. A signal (hereinafter referred to as a propagation path equalization replica signal) resulting from multiplication by each multiplier 17 for each subcarrier is input to the phase shifter 19.

  The incoming wave detector 18 receives an incoming wave from the base station 2 (# 1) and a base station 2 (# 2) from a received signal received by one antenna (antenna Ant2R in the example of FIG. 2). The difference in radio wave propagation time from the incoming wave (hereinafter referred to as the incoming wave time difference) and the received power value of the incoming wave from each base station 2 (# 1, # 2) (hereinafter referred to as the incoming wave power value) ) Is detected. The arrival wave detector 18 outputs the detected arrival wave time difference and the arrival wave power value of each base station 2 (# 1, # 2) to the phase shifter 19.

  For detection of the arrival wave time difference and the arrival wave power value, a main wave of a plurality of arrival waves coming from one base station is used. The main wave is detected by using a known signal unique to each base station 2 (# 1, # 2). Specifically, an incoming wave having a maximum correlation between a received signal and a known signal is set as a main wave. As the known signal, a signal of a specific channel (for example, BCH) broadcast from each base station 2 (# 1, # 2) can be used. As another method for detecting the main wave, the main wave can be detected using the autocorrelation value of the CP portion of each OFDM signal.

The incoming wave power value is the received power value of the main wave. As the arrival wave time difference, the difference in the propagation time of the main wave from the other base station 2 is detected with reference to the base station 2 having the maximum received power value of the main wave (that is, the incoming wave power value). To do. Since transmission data of the MIMO scheme is transmitted from each base station 2 (# 1, # 2) at the same time, the difference in the arrival time of the main wave is used as the difference in the propagation time of the main wave. The arrival wave time difference is given a positive sign when the main wave from another base station 2 arrives early (that is, the propagation time is short) with reference to the base station 2 having the maximum arrival wave power value. On the other hand, if it arrives late (that is, the propagation time is long), a negative sign is added.
Note that the default base station 2 is determined in advance, and when the incoming wave power value of each base station 2 is the same, the default base station 2 is used as a reference.

  The phase shifter 19 changes the phase of the propagation path equalized replica signal of each subcarrier input from each multiplier 17. The phase shift method is based on the arrival wave time difference and the arrival wave power value input from the arrival wave detector 18 so as to match the phase difference of the main wave from each base station 2 (# 1, # 2). The phase of the propagation path equalization replica signal of each subcarrier related to each base station 2 (# 1, # 2) is advanced or delayed. If there is no phase difference of the main wave from each base station 2 (# 1, # 2), the phase of the channel equalization replica signal is not changed.

  FIG. 3 is a block diagram of the phase shifter 19 shown in FIG. In FIG. 3, the phase shifter 19 includes a comparator 31, a phase shift amount calculator 32, switches SW- 1 to SWn and a multiplier 33. The switches SW-1 to SW-n are for switching whether the phase is changed for the propagation path equalization replica signal related to the base station 2 of the two base stations 2 (# 1, # 2). The switches SW-1 to SW-n are provided for each subcarrier, but the switching is performed all at once. The multiplier 33 is for changing the phase of the propagation path equalized replica signal. A total of 4n multipliers 33 are provided for each combination of two base stations 2 (# 1, # 2), n subcarriers, and two reception antennas Ant1R and Ant2R.

The phase shifter 19 receives a channel equalization replica signal of each subcarrier. Here, the propagation path equalized replica signal will be described. The propagation path equalized replica signal is calculated as a product of the replica signal related to each base station 2 and the transfer function between the antennas for each subcarrier (f _{1 to} f _n ). The replica signal at time t of each subcarrier (f _{1 to} f _n ) related to the base station 2 (# 1) is x ₁ (t, f _{1 to} f _n ), and each subcarrier related to the base station 2 (# 2). The replica signal at time t of (f _{1 to} f _n ) is x ₂ (t, f _{1 to} f _n ). The transfer function at time t of each subcarrier (f _{1 to} f _n ) from the antenna Ant1T to the receiving antenna Ant1R of the base station 2 (# 1) is h ₁₁ (t, f _{1 to} f _n ), and the base station 2 (# 1) The transfer function at time t of each subcarrier (f _{1 to} f _n ) from the antenna Ant1T to the reception antenna Ant2R is h ₁₂ (t, f _{1 to} f _n ), and the antenna Ant2T of the base station 2 (# 2) From the antenna Ant2T of the base station 2 (# 2) to the receiving antenna Ant2R. The transfer function at time t of each subcarrier (f _{1 to} f _n ) from the receiving antenna Ant1R to the receiving antenna Ant1R is h ₂₁ (t, f _{1 to} f _n ). The transfer function of each subcarrier (f _{1 to} f _n ) at time t is h ₂₂ (t, f _{1 to} f _n ).

Thus, for example, for the subcarrier (f ₁ ), the propagation path equalization replica signal for the received signal transmitted from the antenna Ant1T of the base station 2 (# 1) and received by the receiving antenna Ant1R is “h ₁₁ (t , F ₁ ) * x ₁ (t, f ₁ ) ”, the propagation path equalized replica signal for the received signal transmitted from the antenna Ant1T of the base station 2 (# 1) and received by the receiving antenna Ant2R is“ h ₁₂ (T, f ₁ ) * x ₁ (t, f ₁ ) ”, the propagation path equalization replica signal for the received signal transmitted from the antenna Ant2T of the base station 2 (# 2) and received by the receiving antenna Ant1R is“ _{h 21 (t, f 1)} * x 2 (t, f 1) ", the received signal has been received is transmitted by the receiving antenna Ant2R from antenna Ant2T base station 2 (# 2) Nitsu Propagation path equalization replica signal of Te is _{"h 22 (t, f 1)} * x 2 (t, f 1) ", is. These propagation path equalization replica signals are input to the corresponding multipliers 33.

  Next, the operation of the phase shifter 19 shown in FIG. 3 will be described.

  The comparator 31 compares the incoming wave power value of the base station 2 (# 1) with the incoming wave power value of the base station 2 (# 2). A signal indicating the magnitude relation of the comparison result is output as the simultaneous switching signal 34 of the switches SW-1 to SWn. When the incoming wave power value of the base station 2 (# 1) and the incoming wave power value of the base station 2 (# 2) are the same, the incoming wave power value of the default base station 2 is assumed to be larger. , Switches SW-1 to SWn are simultaneously output.

  The switches SW-1 to SW-n connect the output signals 35-1 to 35-n of the phase shift amount calculator 32 to the multiplier 33 corresponding to the base station 2 (# 1) or the base station 2 (# 2). Are connected to the multiplier 33 corresponding to. The simultaneous switching of the switches SW-1 to SW-n is performed so that the output signals 35-1 to 35-n of the phase shift amount calculator 32 are connected to the multiplier 33 corresponding to the base station 2 having the smaller incoming wave power value. .

  For example, the comparator 31 has a sign of a difference (positive sign or negative sign when the incoming wave power value of the base station 2 (# 2) is subtracted from the incoming wave power value of the base station 2 (# 1). Is zero, that is, a positive sign (that is, the default is base station 2 (# 1)) is output as the simultaneous switching signal 34 of the switches SW-1 to SWn. When 34 is a positive sign (that is, when the incoming wave power value of the base station 2 (# 2) is smaller), the output signals 35-1 to 35-n of the phase shift amount calculator 32 are transmitted to the base station 2 (# 2 On the other hand, when the simultaneous switching signal 34 has a negative sign (that is, when the incoming wave power value of the base station 2 (# 1) is smaller), the phase shift amount is connected. The output signals 35-1 to 35-n of the calculator 32 are configured to be connected to the multiplier 33 corresponding to the base station 2 (# 1). Keep.

The phase shift amount calculator 32 calculates the phase shift amount θ for each subcarrier based on the arrival wave time difference. The phase shift amount θ indicates the amount and direction (whether the phase is advanced or delayed) with respect to the propagation path equalized replica signal related to the base station 2 having the smaller incoming wave power value. The phase shift amount θ related to each subcarrier is calculated by the equation (1).
θ = e ^{j2πΔk / n} (1)
However, (DELTA) is an arrival wave time difference (with a positive / negative sign), n is the number of subcarriers. k is a value “0, 1, 2,..., n−1” corresponding to the subcarrier (“k = 0” corresponds to the DC subcarrier).

  The amount of phase shift θ corresponds to the arrival wave time difference of the main wave from each base station 2 (# 1, # 2) when the main wave from the base station 2 having the larger incoming wave power value is used as a reference. This is a phase difference and differs between adjacent subcarriers by an amount corresponding to the subcarrier interval.

  The phase shift amount calculator 32 outputs the phase shift amount θ related to each subcarrier as output signals 35-1 to 35-n. The phase shift amount θ related to each subcarrier is input to the switches SW-1 to SWn corresponding to each subcarrier. The switches SW-1 to SW-n use the simultaneous switching signal 34 to output the output signals 35-1 to 35-n corresponding to the phase shift amount θ of each subcarrier to the multiplier 33 corresponding to the base station 2 having the smaller incoming wave power value. To be connected to. Thus, for each subcarrier, the multiplier 33 corresponding to the base station 2 with the smaller incoming wave power value has a phase shift amount θ, and the propagation path corresponding to the base station 2 with the smaller incoming wave power value. Multiplication is performed on the normalized replica signal. Thereby, the propagation path equalization replica signal of each subcarrier corresponding to the base station 2 having the smaller incoming wave power value is phase-shifted by the phase shift amount θ related to each subcarrier. Note that the propagation path equalization replica signal of each subcarrier corresponding to the base station 2 with the larger incoming wave power value is output from the multiplier 33 as it is, and therefore is not phase-shifted.

  The output signal (propagation channel equalization / phase adjustment replica signal) from each multiplier 33 is sent to the MLD detector 14 corresponding to each subcarrier.

  According to the first embodiment, by changing the phase of the channel equalization replica signal related to the base station 2 with the smaller incoming wave power value by the phase shift amount θ, the base station with the larger incoming wave power value 2 and the phase-relationship between the main wave from the base station 2 with the smaller incoming wave power value and the propagation path equalized replica signal for the base station 2 with the larger incoming wave power value. The phase relationship between the propagation path equalized replica signal related to the base station 2 having the smaller wave power value can be matched. As a result, each MLD detector 14 transmits a propagation path equalization replica signal (propagation path equalization / phase adjustment) that matches the phase relationship of the main wave from each base station 2 (# 1, # 2) in each subcarrier. Replica signal) can be used. This is equivalent to correcting the difference in radio wave propagation distance between the antenna of each base station 2 (# 1, # 2) and the antenna of the wireless terminal 1 (that is, the phase difference of the incoming wave). This improves the accuracy when the OFDM symbol transmitted from each base station 2 (# 1, # 2) is detected by the MLD method, and can prevent the bit error rate from being degraded after the demodulation.

  FIG. 4 is Example 2 of the receiver 10 included in the wireless terminal 1 according to the present embodiment. 4 is different from FIG. 2 according to the first embodiment in that the phase shifter 19 is unnecessary. In the second embodiment, the replica generator 40 has a phase shift function. In FIG. 4, parts corresponding to those in FIG. 2 are assigned the same reference numerals and explanations thereof are omitted. Hereinafter, differences from the first embodiment will be described.

  The replica generator 40 receives the arrival wave time difference and the arrival wave power value from the arrival wave detector 18. When the replica generator 40 generates a replica signal of each subcarrier related to each base station 2 (# 1, # 2), based on the arrival wave time difference and the arrival wave power value, each base station 2 (# 1, # 2) The phase of the replica signal of each subcarrier related to each base station 2 (# 1, # 2) is advanced or delayed so as to match the phase difference of the main wave from # 2). Specifically, the phase shift amount θ of each subcarrier is calculated by the above equation (1). Then, the replica signal of each subcarrier related to the base station 2 having the smaller incoming wave power value is multiplied by the phase shift amount θ of each subcarrier. As a result, the phase of the replica signal of each subcarrier related to the base station 2 with the smaller incoming wave power value is changed by the phase shift amount θ, so that the main wave from the base station 2 with the larger incoming wave power value And the main signal from the base station 2 with the smaller incoming wave power value, the replica signal related to the base station 2 with the larger incoming wave power value and the base station with the smaller incoming wave power value The phase relationship between the replica signals according to 2 can be matched.

  The replica signal (phase adjusted replica signal) of each subcarrier generated and phase-adjusted by the replica generator 40 is transferred to each subcarrier estimated by the propagation path estimator 15 by the multiplier 17 related to each subcarrier. And multiplied. The propagation channel equalization / phase adjustment replica signal of each subcarrier, which is the multiplication result, is sent to the MLD detector 14 corresponding to each subcarrier.

  In the second embodiment, the replica signal is phase-shifted before being multiplied by the transfer function. As in the first embodiment, the main signal from each base station 2 (# 1, # 2) is sent to the MLD detector 14. A propagation path equalization replica signal (propagation path equalization / phase adjustment replica signal) that matches the phase relationship of waves can be supplied. This improves the accuracy when the OFDM symbol transmitted from each base station 2 (# 1, # 2) is detected by the MLD method, and can prevent the bit error rate from being degraded after the demodulation.

  As described above, according to the present embodiment, in the OFDM-MIMO wireless communication system that performs simultaneous communication combining the OFDM scheme and the MIMO scheme between a plurality of base stations 2 and one wireless terminal 1, each base station 2 It is possible to deal with a difference in radio wave propagation distance between the antenna and the antenna of the wireless terminal 1 and to prevent the bit error rate from being deteriorated. This can contribute to expanding the service area of the OFDM-MIMO wireless communication system.

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, in the above-described embodiment, the base station with the maximum received power value of the main wave is the reference base station, but the method of determining the reference base station is not limited to this. For example, a base station whose received power value of the main wave is a predetermined number (for example, second) largest may be used as the reference base station. Alternatively, the reference base station may be determined and fixed in advance. Note that, by setting the base station having the maximum received power value of the main wave as the reference base station, improvement in detection efficiency by the MLD method can be expected.

It is a conceptual diagram which shows the structure of the OFDM-MIMO radio | wireless communications system which concerns on one Embodiment of this invention. It is Example 1 of the receiver 10 which the radio | wireless terminal 1 shown in FIG. 1 has. It is a block diagram of the phase shifter 19 shown in FIG. This is a second embodiment of the receiver 10 included in the wireless terminal 1 shown in FIG. 1 is a basic conceptual diagram of a MIMO wireless communication system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wireless terminal, 2 ... Base station, 3 ... Base station control apparatus, 10 ... Receiver, 11 ... CP remover, 12 ... Serial / parallel signal converter (S / P converter), 13 ... Discrete Fourier transformer (DFT), 14 ... MLD detector, 15 ... propagation path estimator, 16, 40 ... replica generator, 17, 33 ... multiplier, 18 ... incoming wave detector, 19 ... phase shifter, 31 ... comparator, 32 ... Phase shift amount calculator, Ant1T, Ant2T, Ant1R, Ant2R ... antenna, SW-1 to n ... switch

Claims (7)

In the receiver of the wireless terminal in the wireless communication system that performs simultaneous downlink communication that combines the OFDM scheme and the MIMO scheme between a plurality of base stations and one wireless terminal,
Replica generating means for generating a replica signal related to each base station for each OFDM subcarrier,
An arrival wave time difference detection means for detecting a difference in propagation time of an arrival wave from a base station other than the reference base station with respect to an arrival wave from the reference base station;
Phase shift means for shifting the phase difference corresponding to the detected arrival wave time difference for each subcarrier of the OFDM scheme with respect to the replica signal related to the base station other than the reference base station,
For each OFDM system subcarrier, perform a MIMO system reception process using the received signal of the subcarrier and the replica signal after the phase shift.
A receiver characterized by that. An incoming wave power value detecting means for detecting a received power value of an incoming wave from each base station,
Determining a reference base station based on the detected incoming wave power value;
The receiver according to claim 1.   3. The receiver according to claim 1, wherein a main wave among a plurality of incoming waves coming from one base station is used for the detection.   The receiver according to claim 3, wherein the reference base station is a base station having a maximum received power value of the main wave. Providing propagation path estimation means for estimating the transfer function of the radio wave propagation path for each subcarrier using the received signal of each subcarrier,
5. The phase shift means is provided in a step subsequent to the step of performing channel equalization using the estimated transfer function with respect to a replica signal, according to claim 1. Receiving machine. Providing propagation path estimation means for estimating the transfer function of the radio wave propagation path for each subcarrier using the received signal of each subcarrier,
5. The phase shift means according to claim 1, wherein the phase shift means is provided in a step prior to a step of performing channel equalization using the estimated transfer function with respect to a replica signal. Receiving machine. A method of receiving the wireless terminal in a wireless communication system that performs simultaneous downlink communication using a combination of OFDM and MIMO between a plurality of base stations and a single wireless terminal,
Generating a replica signal for each base station for each OFDM subcarrier;
Detecting a difference in propagation time (arrival time difference) of incoming waves from base stations other than the reference base station with respect to incoming waves from the reference base station;
For the replica signal related to the base station other than the reference base station, for each subcarrier of the OFDM scheme, phase-shifting by a phase difference corresponding to the detected arrival wave time difference;
For each OFDM system subcarrier, performing a MIMO system reception process using the received signal of the subcarrier and the replica signal after the phase shift;
A receiving method comprising:

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