WO2022038689A1

WO2022038689A1 - Reception device, reception method, program, and transmission device

Info

Publication number: WO2022038689A1
Application number: PCT/JP2020/031171
Authority: WO
Inventors: 友規村上; 匡史岩渕; 陸大宮; 智明小川; 泰司鷹取
Original assignee: 日本電信電話株式会社
Priority date: 2020-08-18
Filing date: 2020-08-18
Publication date: 2022-02-24
Also published as: JP7468667B2; JPWO2022038689A1

Abstract

A reception device according to the present invention comprises: a reconfigurable antenna that, while switching antenna characteristics, receives radio signals transmitted from a transmission device; a notification unit that determines a setting related to the transport of the radio signals on the basis of information related to the antenna characteristics of the reconfigurable antenna used when receiving the radio signals and that notifies the transmission device of the determined setting; and a signal extracting unit that extracts, from the radio signals transmitted from the transmission device by use of the setting, first signals received at times when the reconfigurable antenna exhibits a first antenna characteristic and second signals received at times when the reconfigurable antenna exhibits a second antenna characteristic.

Description

Receiver, receiving method, program, and transmitter

This disclosure relates to a receiving device, a receiving method, a program, and a transmitting device.

Wireless communication traffic continues to increase due to the rapid spread of wireless devices. In order to stably accommodate this wireless communication traffic, it is required to increase the capacity of the wireless communication system. In order to realize a large capacity of a wireless communication system, MIMO (Multiple Input Multiple Output), which performs spatial division multiplex transmission at the same frequency and at the same time using a plurality of antennas, has been put into practical use. Furthermore, for future wireless communication systems, research and development of large-scale (Massive) MIMO using a large number of antennas is underway for further expansion of the capacity realized by MIMO.

Non-Patent Document 1 discloses a technique called Virtual Massive MIMO (VM-MIMO). In this VM-MIMO, the radio base station receives a signal while periodically switching the antenna characteristics by the characteristic variable antenna. Then, each signal sampled at the timing when the antenna characteristics become the same is extracted, and each extracted signal is subjected to signal processing similar to that of normal MIMO. As a result, for example, the number of antennas and the like can be reduced, so that the size and cost of the radio base station can be reduced.

When receiving a signal while periodically switching the antenna characteristics with a variable characteristic antenna, it is considered that the quality of wireless communication may not be appropriate due to the switching of the antenna characteristics.

It is an object of the present disclosure to provide a technique capable of appropriately performing wireless communication in a receiving device that receives wireless signals transmitted from a plurality of antennas at the same frequency and at the same time with a variable characteristic antenna.

According to the disclosed technology, a characteristic variable antenna that receives a radio signal transmitted from a transmitting device while switching antenna characteristics, and a characteristic variable antenna.
A notification unit that determines a setting related to transmission of the wireless signal based on information on the antenna characteristic of the characteristic variable antenna when receiving the wireless signal, and notifies the transmitting device of the determined setting.
From the radio signal transmitted from the transmitter according to the setting, the first signal received at each time point in which the characteristic variable antenna has the first antenna characteristic and the first signal received at each time point in which the characteristic variable antenna has the second antenna characteristic. A signal extraction unit that extracts the received second signal, and
A receiving device is provided.

According to the disclosed technology, it is possible to appropriately perform wireless communication in a receiving device that receives wireless signals transmitted from a plurality of antennas at the same frequency and at the same time with a variable characteristic antenna.

It is a system configuration diagram in this embodiment. It is a system configuration diagram in this embodiment. It is a figure for demonstrating the operation of VM-MIMO. It is a block diagram of a wireless terminal station. It is a block diagram of a radio base station. It is a block diagram of the characteristic variable antenna. It is a block diagram of a radio base station. It is a sequence diagram which shows the operation of a wireless communication system. It is a figure which shows the example of a table. It is a figure for demonstrating operation of a signal extraction part.

Hereinafter, an embodiment of the present disclosure (the present embodiment) will be described with reference to the drawings. The embodiments described below are merely examples, and the embodiments to which the present disclosure applies are not limited to the following embodiments.

The disclosed technology can be applied to various receiving devices (equipment) that receive radio signals transmitted from a plurality of antennas at the same frequency and at the same time. For example, it can be applied to the case where the wireless terminal station 1 is used as the receiving device. In this case, the transmitting device may be, for example, a wireless base station 2, a smart glass, a peripheral device such as a smart watch, or the like.

In the following, an example in which the wireless terminal station 1 is used as the transmitting device and the wireless base station 2 is used as the receiving device will be described.

(overall structure)
1 and 2 show a configuration example of a wireless communication system according to the present embodiment. As shown in FIGS. 1 and 2, the wireless communication system according to the present embodiment has a wireless terminal station 1 and a wireless base station 2. The radio terminal station 1 has one or more antennas, and the radio base station 2 has one characteristic variable antenna. The number of characteristic variable antennas in the radio base station 2 may be plural. As shown in the figure, in the present embodiment, uplink communication (uplink) from the wireless terminal station 1 to the wireless base station 2 is targeted.

FIG. 1 shows an example in the case where the radio base station 2 receives a signal transmitted from a radio terminal station 1 having one or more antennas (single user MIMO). Further, FIG. 2 shows an example in which the radio base station 2 receives a signal transmitted from a plurality of radio terminal stations 1 having one or more antennas (in the case of multi-user MIMO or the like).

(Outline of operation of wireless communication system)
For example, the radio base station 2 receives each radio signal with a virtual multi-antenna using one characteristic variable antenna by the technique of Visual Massive MIMO (VM-MIMO) disclosed in Non-Patent Document 1. You may.

As shown in FIG. 3, the radio base station 2 changes the antenna characteristics of the variable characteristic antenna at high speed and periodically by changing the signal transmitted from each antenna of one or more radio terminal stations 1 at the same frequency and at the same time. Receive while. The radio base station 2 samples the received signal at a higher speed than in the case of general MIMO, divides and extracts the received signal at the timing when the antenna characteristics are the same from the sampled received signal, and extracts the extracted received signal. On the other hand, general MIMO reception processing is performed. Each extracted received signal can be regarded as a signal arriving from different propagation paths, although a slight delay occurs due to sampling deviation. Therefore, each radio signal arriving from each propagation path with one characteristic variable antenna. Can be received.

In the example of FIG. 3, the radio base station 2 receives a signal while periodically changing the four antenna characteristics 1 to 4. In the example of FIG. 3, the timing signal of the antenna characteristic 1 is indicated by "1", the timing signal of the antenna characteristic 2 is indicated by "2", the timing signal of the antenna characteristic 3 is indicated by "3", and the antenna characteristic is indicated. The signal of the timing of 4 is indicated by "4".

Also, the antennas with antenna characteristics 1 to 4 are called virtual antennas 1 to 4, respectively. In FIG. 3, the waveform of the signal indicated by "1" is shown as the waveform of the virtual antenna 1.

(Wireless terminal station 1)
FIG. 4 shows a configuration example of the wireless terminal station 1 according to the present embodiment. As shown in FIG. 4, the radio terminal station 1 has one or more antennas 10, a plurality of RF units 11, a plurality of D / A conversion units 12, a MIMO signal generation unit 13, and a setting unit 14. It should be noted that the functional block generally mounted on the wireless terminal station 1 is omitted.

The setting unit 14 sets various parameters related to transmission in the MIMO signal generation unit 13 based on various parameters related to transmission from the wireless terminal station 1 to the wireless base station 2 (hereinafter, referred to as “transmission parameters”). The transmission parameter is notified from the radio base station 2.

The MIMO signal generation unit 13 generates a plurality of MIMO signals from the transmission data based on various parameters related to transmission set by the setting unit 14, and inputs each MIMO signal to the D / A conversion unit 12.

The D / A conversion unit 12 converts the input MIMO signal into an analog signal and outputs the analog signal to the RF unit 11.

The RF unit 11 performs analog processing such as amplification, frequency conversion, and filtering on the analog signal, and outputs the processed signal to each antenna 10. It is assumed that the RF unit 11 here is equipped with the function of the RF front end of a general wireless device. The antenna 10 radiates the input signal into the air as a radio signal.

(Wireless base station 2)
FIG. 5 shows a configuration example of the radio base station 2 in the present embodiment. As shown in FIG. 5, the radio base station 2 in the present embodiment includes a variable characteristic antenna 20, an RF unit 21, an A / D conversion unit 22, an antenna control unit 23, a signal extraction unit 24, and a MIMO signal demodulation unit 25. It has an index value calculation unit 26 and a determination unit 27 (an example of a “notification unit”). It should be noted that the functional blocks generally mounted on the radio base station are not shown. The functions of each part are as follows.

((About the variable characteristic antenna 20))
The characteristic variable antenna 20 is an antenna capable of switching the characteristics of the antenna, and receives the radio signal transmitted from the wireless terminal station 1 while switching the antenna characteristics. The variable characteristic antenna 20 may periodically switch the antenna characteristics (directivity, output power, phase, etc.) according to the control information input from the antenna control unit 23, for example.

FIG. 6 shows a configuration example of the variable characteristic antenna 20. The characteristic variable antenna 20 shown in FIG. 6 has a feeding element (Antenna element) such as a dipole antenna arranged at the center, and one or more non-feeding elements (Parastic elements) arranged around the feeding element (Antenna element).

The characteristic variable antenna 20 may change the reflection characteristic of the non-feeding element by, for example, periodically rotating the non-feeding element based on the control information input from the antenna control unit 23. As a result, the propagation path to the feeding element fluctuates periodically, so that the characteristics of the antenna can be switched.

The characteristic variable antenna 20 outputs the received signal to one RF unit 21. The RF unit 21 performs processing such as amplification, frequency change, and filtering on the signal input from the characteristic variable antenna 20, and outputs the processed signal to the A / D conversion unit 22. It is assumed that the RF unit 21 here is equipped with the function of the RF front end of a general wireless device.

The A / D conversion unit 22 converts an analog signal input from the RF unit 21 into a digital signal by sampling the analog signal, and outputs the digital signal to the signal extraction unit 24 and the index value calculation unit 26. Further, the A / D conversion unit 22 notifies the antenna control unit 23 of the sampling period. The A / D conversion unit 22 may determine the timing for sampling the analog signal input from the RF unit 21 based on the information indicating the timing at which the preamble signal received from the wireless terminal station 1 is detected. Thereby, for example, the radio signal received from the radio terminal station 1 that transmitted the preamble signal can be sampled at a more appropriate timing.

The antenna control unit 23 outputs an antenna control signal according to the sampling cycle of the A / D conversion unit 22 to the characteristic variable antenna 20.

The signal extraction unit 24, for example, extracts each signal received by the characteristic variable antenna 20 at each periodic time point having different antenna characteristics from the signal input from the A / D conversion unit 22.

More specifically, the signal extraction unit 24 uses the signal input from the A / D conversion unit 22 at each time point in the cycle in which the antenna characteristics of the variable characteristic antenna 20 change, as described with reference to FIG. Divide into each sampled signal. As a result, each signal sampled at the timing when the antenna characteristics of the variable characteristic antenna 20 become the same is extracted (generated).

Then, the signal extraction unit 24 extracts (selects) the signal to be output to the MIMO signal demodulation unit 25 from the plurality of signals obtained by division based on the information input from the determination unit 27. Then, the signal extraction unit 24 outputs the extracted signal to the MIMO signal demodulation unit 25. As a result, it is possible to acquire a radio signal similar to a radio signal received by a plurality of antennas having different antenna characteristics from one characteristic variable antenna 20.

The MIMO signal demodulation unit 25 performs demodulation processing on the signal received from the signal extraction unit 24. The MIMO signal demodulation unit 25 may perform demodulation processing similar to demodulation processing in general MIMO or the like, for example. Thereby, for example, one characteristic variable antenna 20 can be used as a plurality of virtual antennas to receive a radio signal.

The index value calculation unit 26 calculates various index values related to the transmission quality of the uplink according to the antenna characteristics of the characteristic variable antenna 20 when the radio base station 2 receives the radio signal transmitted from the radio terminal station 1. do. The index value calculation unit 26 includes, for example, a channel correlation value, a transmission capacity based on the virtual antenna used (channel capacity, transmission line capacity, throughput), a received power for each spatial transmission based on the virtual antenna used, and the like. And the received power to noise power ratio (SNR) based on the virtual antenna used, the propagation channel response, and the like may be calculated as index values.

The channel correlation value is a numerical representation of the difference between different antenna characteristics. For example, the index value calculation unit 26 may calculate the propagation channel response in each antenna characteristic from the signal input from the A / D conversion unit 22 based on the control information of the antenna input from the antenna control unit 23. good. Then, the index value calculation unit 26 may calculate the channel correlation value based on the propagation channel response of each antenna characteristic set by the characteristic variable antenna 20.

The index value calculation unit 26 outputs the calculated index value to the determination unit 27.

The determination unit 27 determines the transmission parameter based on the index value input from the index value calculation unit 26, and notifies the wireless terminal station 1 of the determined transmission parameter by wireless communication. Further, the determination unit 27 calculates the number of extraction signals based on the index value input from the index value calculation unit 26 and outputs the number to the signal extraction unit 24. An example of a method for calculating the number of extracted signals will be described later.

Here, in the characteristic variable antenna 20, when the antenna characteristics are periodically switched by, for example, one of four virtual antennas is periodically selected, the A / D conversion unit 22 is a general radio base. Signals 1 to 4 corresponding to each antenna characteristic are sampled and output at a sampling period that is four times or more the sampling period of the A / D conversion unit 22 of the station. Then, the antenna control unit 23 selects one of the four virtual antennas in the sampling cycle of the A / D conversion unit 22 and switches the antenna characteristics.

For convenience, it is assumed here that the number of extraction signals determined by the determination unit 27 is 4. At this time, the signal extraction unit 24 divides and extracts the signals 1 to 4 corresponding to each antenna characteristic in the same sampling period as the sampling period of the A / D conversion unit 22, and outputs the signals to the MIMO signal demodulation unit 25. As a result, signals 1 to 4 having the same antenna characteristics are periodically output to the four output ports of the signal extraction unit 24.

(Other configuration examples)
The function of each functional block in the radio base station 2 shown in FIG. 5 may be realized by dedicated hardware (LSI or the like), or "characteristic variable antenna 20, RF unit 21, A / D conversion unit 22, reference antenna" may be realized. A part other than "28" (that is, a part that processes a digital signal) may be realized by a general-purpose computer including a processor (CPU, DSP, etc.) and a memory, and software running on the computer.

FIG. 7 shows a configuration example of the wireless base station 2 when the wireless base station 2 is realized by using a computer and software.

As shown in FIG. 7, the radio base station 2 includes a processor 101, a memory 102, an auxiliary storage device 103, an input / output device 104, a characteristic variable antenna 20, an RF unit 21, and an A / D conversion unit 22. Has a configuration connected by a bus.

For example, the auxiliary storage device 103 (storage medium) stores a program that realizes the operation of the radio base station 2. During the operation of the radio base station 2, the program is read into the memory 102, and the processor 101 reads the program from the memory 102 and executes it. For example, the processor 101 executes the processing of the antenna control unit 23, the signal extraction unit 24, the MIMO signal demodulation unit 25, the index value calculation unit 26, and the determination unit 27 by the program.

The input / output device 104 outputs, for example, the signal obtained by the MIMO signal demodulation unit 25. Further, the information set in advance may be input from the input / output device 104.

(Operation example)
Next, an operation (processing) example of the wireless communication system will be described more specifically with reference to the sequence diagram of FIG. The process related to the determination of the number of extracted signals and the actual process (process for providing the communication service) are executed in parallel. Therefore, the number of extracted signals can be changed at any time during the communication service provision.

The antenna control unit 23 outputs an antenna control signal synchronized with the sampling cycle of the A / D conversion unit 22 to the characteristic variable antenna 20, and the characteristic variable antenna 20 periodically switches the antenna characteristics according to the antenna control signal. ing.

<S1>
In S1 (step 1), the radio terminal station 1 transmits a radio signal to the radio base station 2. Here, the radio terminal station 1 may transmit, for example, a radio signal of a random access preamble (PRACH: Physical Random Access Channel) to the radio base station 2. The PRACH is a channel for first transmitting a preamble signal when establishing a connection with the radio terminal station 1 and the radio base station 2 and when performing resynchronization.

<S2>
In S2, the radio base station 2 receives signals simultaneously transmitted from each antenna of one or more radio terminal stations 1. Here, the signal received by the characteristic variable antenna 20 of the radio base station 2 is input to the RF unit 21, and the signal processed by the RF unit 21 is output to the A / D conversion unit 22.

The A / D conversion unit 22 samples the input signal (analog signal) and acquires the sampled signal (digital signal). The "signal" described below is a signal acquired by sampling. The signal obtained by the A / D conversion unit 22 is output to the signal extraction unit 24 and the index value calculation unit 26. The A / D conversion unit 22 may perform sampling a predetermined number of times in the cycle of change in antenna characteristics.

<S3>
In S3, the index value calculation unit 26 of the radio base station 2 has a propagation channel in each antenna characteristic from the signal input from the A / D conversion unit 22 based on the control information of the antenna input from the antenna control unit 23. In addition to calculating the response, the correlation value (channel correlation value) between the propagation channel responses at each antenna characteristic set by the characteristic variable antenna 20 is calculated.

The index value calculation unit 26 may calculate the correlation value between the propagation channel responses at each antenna characteristic, for example, by the following equation 1.

In Equation 1, _ai is the propagation channel response vector between the antenna at a certain antenna characteristic and the _i -th antenna of the radio terminal station 1, and bi is the antenna and the radio terminal station 1 at an antenna characteristic different from _ai . It is a propagation channel response vector to and from the i-th antenna of. The index value calculation unit 26 calculates the channel correlation value in all the antenna characteristics by obtaining the channel correlation value by the equation 1 for each set of antenna characteristics and adding the channel correlation values of all the sets.

For example, assuming that the characteristic variable antenna 20 switches between four antenna characteristics, the antennas in each characteristic are referred to as a virtual antenna 1, a virtual antenna 2, a virtual antenna 3, and a virtual antenna 4.

In this case, the index value calculation unit 26 uses the channel correlation value between the virtual antenna 1 and the virtual antenna 2, the channel correlation value between the virtual antenna 1 and the virtual antenna 3, and the interval between the virtual antenna 1 and the virtual antenna 4. Channel correlation value, channel correlation value between virtual antenna 2 and virtual antenna 3, channel correlation value between virtual antenna 2 and virtual antenna 4, and channel correlation value between virtual antenna 3 and virtual antenna 4. By calculating and calculating the sum of these channel correlation values, the channel correlation value between the virtual antennas 1 to 4 is calculated.

Further, depending on the calculation method of the number of extracted signals, in addition to the channel correlation value between the two virtual antennas and the channel correlation value between the virtual antennas 1 to 4 as described above, the

virtual antennas

1, 2 and 3 are used. The channel correlation value, the channel correlation value between the

virtual antennas

1, 2 and 4, and the channel correlation value between the

virtual antennas

2, 3 and 4 may be calculated. That is, the channel correlation value may be calculated for all combinations.

<S4>
In S4, the determination unit 27 of the radio base station 2 determines various parameters based on various index values input from the index value calculation unit 26. Here, the determination unit 27 of the radio base station 2 calculates the number of extraction signals based on the channel correlation value input from the index value calculation unit 26, and outputs the calculation result to the signal extraction unit 24, for example.

In this case, the determination unit 27 holds, for example, a table showing the relationship between the channel correlation value calculated in advance by simulation or actual measurement and the transmission capacity, and is based on the channel correlation value calculated by the index value calculation unit 26. Refer to the table to determine the minimum number of extracted signals that will reduce the amount of transmission capacity degradation below the threshold. The threshold value is a value given in advance.

The meaning of "the minimum number of extracted signals whose transmission capacity deterioration amount is less than the threshold value" is as follows.

The larger the number of extracted signals (that is, the larger the number of virtual antennas used to receive the signal input to the MIMO signal demodulation unit 25), the larger the transmission capacity, but if the number of extracted signals becomes too large, MIMO The processing load of the signal demodulation unit 25 becomes excessive. The degree of increase in transmission capacity with respect to the increase in the number of extracted signals decreases as the number of extracted signals increases. For example, the amount of increase in transmission capacity when the number of extracted signals increases from 16 to 18 is smaller than the amount of increase in transmission capacity when the number of extracted signals increases from 10 to 12.

That is, the transmission capacity in the number of extracted signals M smaller than N is deteriorated as compared with the transmission capacity when the number of extracted signals equal to the number of virtual antennas used for switching (referred to as N for convenience) is used. In the present embodiment, the "minimum number of extracted signals whose transmission capacity deterioration amount is equal to or less than the threshold value" is set so that the processing load of the MIMO signal demodulation unit 25 does not become excessive while reducing the deterioration of the transmission capacity. It is decided and notified to the signal extraction unit 24.

For example, when N = 16, the amount of deterioration of the transmission capacity of the number of extraction signals = 14 with respect to the transmission capacity when the number of extraction signals = 16 is equal to or less than the threshold value (that is, it does not deteriorate much), and the extraction signal The amount of deterioration of the transmission capacity of the number = 12 is also equal to or less than the threshold value, but when the amount of deterioration of the transmission capacity of the number of extracted signals = 10 exceeds the threshold value, the number of extracted signals = 12.

More specifically, for example, the determination unit 27 holds a table as shown in FIG. 9 for each number of virtual antennas used for signal reception while switching. In the table shown in FIG. 9, the number of extracted signals corresponding to the channel correlation value obtained by the index value calculation unit 26 (= “minimum number of extracted signals whose transmission capacity deterioration is equal to or less than the threshold value”) is determined by channel correlation. It is a table that holds each value.

For example, when the number of virtual antennas = N and "A" is calculated as the channel correlation value, the determination unit 27 refers to the table of FIG. 9 held by itself as the number of extracted signals. N1 "is decided.

In S4, the determination unit 27 may determine only the number of extracted signals as described above, or determine the number of virtual antennas (which virtual antenna signal is used) in addition to the number of extracted signals. You may.

When determining the number of virtual antennas in addition to the number of extracted signals, the determination unit 27 selects, for example, a set of virtual antennas having the minimum channel correlation value (weak correlation) between the number of virtual antennas (weak correlation). decide.

For example, it is assumed that the number of extracted signals = 3 when the four virtual antennas 1 to 4 are switched and used. In this case, for example, among the channel correlation values between the

virtual antennas

1, 2 and 3, the channel correlation values between the

virtual antennas

1, 2 and 4, and the channel correlation values between the

virtual antennas

2, 3 and 4, the virtual antenna 1 Assuming that the channel correlation value between 2 and 3 is minimized, the determination unit 27 determines

virtual antennas

1, 2 and 3 as virtual antennas having a determined number of extracted signals. When the determination unit 27 determines the number of virtual antennas in addition to the number of extraction signals, the determination unit 27 also notifies the signal extraction unit 24 of information indicating the virtual antennas of the determined number of extraction signals.

Further, in S4, the determination unit 27 corresponds to the antenna characteristics of the characteristic variable antenna 20 when receiving the radio signal transmitted from the wireless terminal station 1 based on the index value input from the index value calculation unit 26. Determine the transmission parameters. The index value may include the channel correlation value described above. Further, as will be described later, the index values include the transmission capacity C based on the virtual antenna used, the received power for each spatial transmission based on the virtual antenna used, and the reception based on the virtual antenna used. The power-to-noise power ratio (SNR) and the like may be included.

Here, as transmission parameters, the determination unit 27 may use, for example, a spatial multiplex of MIMO transmission, a modulation method, and a coding method (code) in uplink communication (uplink) from the radio terminal station 1 to the radio base station 2. The conversion method), the coding rate, the band, and the like may be determined.

(Example of making higher quality communication when the transmission environment is good)
For example, the determination unit 27 may determine various parameters for performing higher quality communication when it can be determined that the transmission environment is better based on the index value input from the index value calculation unit 26. In this case, for example, the determination unit 27 may determine various parameters for performing higher quality communication as the channel correlation value is lower (smaller). Further, the determination unit 27 has, for example, a transmission capacity C based on the virtual antenna used, received power for each spatial transmission based on the virtual antenna used, and received power vs. noise power based on the virtual antenna used. The higher (larger) the value of the ratio (SNR), the more various parameters may be determined to enable higher quality communication.

In this case, the determination unit 27 may determine, for example, to perform communication with a larger number of spatial multiplex (for example, 4 or more) as various parameters for performing higher quality communication. Further, the determination unit 27 causes communication by, for example, a modulation method having a higher degree of modulation (for example, 64QAM (Quadrature Amplitude Modulation), 256QAM, 1024QAM, etc.) as various parameters for performing higher quality communication. May be decided.

Further, the determination unit 27 performs communication with a higher efficiency coding rate (code rate, information rate, for example, 5/6, 7/8, etc.) as various parameters for performing higher quality communication. You may decide to do it. Further, the determination unit 27 may determine, for example, to perform communication in a wider bandwidth (for example, 20 MHz or more) as various parameters for performing higher quality communication.

(Example of making lower quality communication when the transmission environment is bad)
The determination unit 27 may determine various parameters for performing lower quality communication, for example, when it can be determined that the transmission environment is worse based on the transmission quality information. In this case, for example, the determination unit 27 may determine various parameters that cause lower quality communication as the channel correlation value is higher (larger). Further, the determination unit 27 has, for example, a transmission capacity C based on the virtual antenna used, received power for each spatial transmission based on the virtual antenna used, and received power vs. noise power based on the virtual antenna used. The lower (smaller) the value of the ratio (SNR), the various parameters that cause lower quality communication may be determined.

In this case, the determination unit 27 may determine, for example, to perform communication with a smaller number of spatial multiplex (for example, less than 4) as various parameters for performing lower quality communication. Further, the determination unit 27 uses, for example, a modulation method with a lower modulation degree (for example, BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM) as various parameters for performing lower quality communication. May be decided to communicate.

Further, the determination unit 27 determines as various parameters for performing communication with lower quality, for example, to perform communication with a lower efficiency coding rate (for example, 1/2, 2/3, etc.). You may. Further, the determination unit 27 may determine, for example, to perform communication with a narrower bandwidth (for example, less than 20 MHz) as various parameters for performing lower quality communication.

<S5>
In S5, the determination unit 27 of the radio base station 2 notifies the wireless terminal station 1 of the determined transmission parameter by wireless communication. Here, the determination unit 27 of the radio base station 2 may notify the transmission parameter by using, for example, an uplink control channel or the like.

<S6>
In S6, the setting unit 14 of the wireless terminal station 1 sets various parameters related to transmission in the MIMO signal generation unit 13 based on the transmission parameters notified from the wireless base station 2.

<S7>
In S7, the radio terminal station 1 transmits an uplink radio signal to the radio base station 2 based on the transmission parameters set in the setting unit 14.

<S8>
In S8, the radio base station 2 receives signals simultaneously transmitted from each antenna of one or more radio terminal stations 1. Here, similarly to the processing of S2 described above, the signal received by the characteristic variable antenna 20 of the radio base station 2 is input to the RF unit 21, and the signal processed by the RF unit 21 is input to the A / D conversion unit 22. It is output. The A / D conversion unit 22 samples the input signal (analog signal) and acquires the sampled signal (digital signal).

Then, the signal extraction unit 24 divides the signal input from the A / D conversion unit 22 into the same sampling period as the sampling period of the A / D conversion unit 22 based on the number of extraction signals received from the determination unit 27. A signal with the number of extracted signals is extracted (selected) from the divided signals, and the extracted signal is output to the MIMO signal demodulator 25.

The maximum number of signals that can be extracted by the signal extraction unit 24 may be predetermined. In that case, when the signal extraction unit 24 is notified of the number of extraction signals larger than the maximum number of signals, the signal extraction unit 24 extracts the signal with the maximum number of signals and uses the extracted signal as a MIMO signal. Output to the demodulation unit 25.

When the signal extraction unit 24 receives only the number of extraction signals from the determination unit 27, which signal is extracted from the divided signals is not limited to a specific method, but for example, which signal is to be extracted is determined in advance. It may be decided.

For example, when using virtual antennas 1 to 4, it is assumed that the

virtual antennas

1, 2, 3, and 4 are selected in this order. In this case, assuming that the number of extracted signals = 3, the signal extraction unit 24 extracts the signals of the

virtual antennas

1, 2 and 3 from the signals of the virtual antennas 1 to 4 and outputs them to the MIMO signal demodulation unit 25. do.

Further, when the signal extraction unit 24 receives the information of the virtual antenna (information of the signal to be extracted) from the determination unit 27, the signal extraction unit 24 extracts the signal notified by the determination unit 27 from the divided signals. Then, it is output to the MIMO signal demodulation unit 25.

FIG. 10 shows an image of the operation by the signal extraction unit 24. In the example shown in FIG. 10, it is assumed that virtual antennas 1 to 8 are used. The signals corresponding to the virtual antennas 1 to 8 are the signals 1 to 8 (in the figure, the circles with numbers indicate the signals).

The signal extraction unit 24 receives the signal sampled by the A / D conversion unit 22. The signal extraction unit 24 divides the input signal in the same cycle as the sampling cycle, so that the

signals

1, 2, 3, 4, 5, 6, 7, 8, ... Are sequentially acquired (identified).

In the example of FIG. 10, it is assumed that the determination unit 27 is specified to the signal extraction unit 24 to extract

signals

1, 4, 7, and 8 from the signals 1 to 8. In this case, the signal extraction unit 24 extracts signals 1, 4, 7, and 8 from the signals 1 to 8, and outputs these signals to the MIMO signal demodulation unit 25.

<S9>
In S9, the MIMO signal demodulation unit 25 performs the MIMO demodulation processing defined in a general wireless communication system with respect to the signal received from the signal extraction unit 24. Information required for MIMO demodulation processing (number of antennas of wireless terminal station 1 and the like) may be given in advance or may be estimated.

(Example of index value other than channel correlation value)
In the above example, the channel correlation value between virtual antennas is used as an index value for determining the number of extracted signals, but this is an example. The number of extracted signals may be determined using an index value other than the channel correlation value.

For example, in S3 of the flow of FIG. 8, the index value calculation unit 26 uses the following equation 2 in place of or in addition to the channel correlation value to provide a theoretical transmission capacity C based on the virtual antenna used. May be calculated as an index value.

INr in the above equation 2 is an identity matrix of _Nr × Nr. Nr is the number of receiving antennas (= the number of virtual antennas used (the number of antenna characteristics to be switched)). Nt is the number of transmitting antennas (= the number of antennas of the wireless terminal station 1). Pt is the transmission power. σ ² _n is noise power. H is a Nr × Nt channel matrix (a matrix having a propagation channel response as an element), and det is a determinant of the matrix in parentheses.

For example, it is assumed that the characteristic variable antenna 20 switches between four antenna characteristics. That is, it is assumed that the virtual antenna 1, the virtual antenna 2, the virtual antenna 3, and the virtual antenna 4 are used.

In this case, the index value calculation unit 26 calculates the transmission capacity when the virtual antennas 1 to 4 are used by using the equation 2.

Further, depending on the calculation method of the number of extracted signals, in addition to the transmission capacity when all the virtual antennas are used as described above, the transmission capacity when the virtual antenna 1 and the virtual antenna 2 are used, and the virtual antenna 1 and the virtual antenna 1 are virtual. The transmission capacity when the antenna 3 is used, the transmission capacity when the virtual antenna 1 and the virtual antenna 4 are used, the transmission capacity when the virtual antenna 2 and the virtual antenna 3 are used, and the virtual antenna 2 and the virtual antenna 4 are used. Transmission capacity in the case, transmission capacity when the virtual antenna 3 and the virtual antenna 4 are used, transmission capacity when the

virtual antennas

1, 2 and 3 are used, transmission capacity when the

virtual antennas

1, 2 and 4 are used, The transmission capacity when the

virtual antennas

2, 3 and 4 are used may be calculated. That is, the transmission capacity may be calculated for all combinations.

In S4, the determination unit 27 calculates the number of extraction signals from the transmission capacity input from the index value calculation unit 26, and outputs the calculation result to the signal extraction unit 24.

For example, the determination unit 27 holds a table in which the transmission capacity is associated with the "minimum number of extracted signals whose deterioration of the transmission capacity is equal to or less than the threshold value" for each number of virtual antennas to be used.

Here, it is assumed that the "minimum number of extracted signals whose deterioration of the transmission capacity is equal to or less than the threshold value" corresponding to the transmission capacity C in the table corresponding to the number of virtual antennas = N is "N1".

At this time, when C is calculated as the transmission capacity by the calculation according to Equation 2, the determination unit 27 determines "N1" as the number of extracted signals by referring to the table.

When determining the number of virtual antennas in addition to the number of extracted signals, the determination unit 27 selects (determines), for example, the set of virtual antennas that maximizes the transmission capacity of the number of virtual antennas.

For example, it is assumed that the number of extracted signals = 3 when the four virtual antennas 1 to 4 are switched and used. In this case, for example, among the transmission capacities of the

virtual antennas

1, 2, and 3, the transmission capacities of the

virtual antennas

1, 2, and 4, and the transmission capacities of the

virtual antennas

2, 3, and 4, the

virtual antennas

1, 2, and 3. Assuming that the transmission capacity in the above is maximized, the determination unit 27 determines the

virtual antennas

1, 2, and 3 as the virtual antennas having the determined number of extracted signals.

The index value calculation unit 26 uses the index value as the index value in place of or in addition to the channel correlation value and the transmission capacity described so far, for example, as the received power for each spatial transmission based on the virtual antenna used. The corresponding value or the like may be calculated. The value corresponding to the received power for each spatial transmission based on the virtual antenna used may be, for example, an eigenvalue obtained by decomposing the above channel matrix H into eigenvalues.

Further, the index value calculation unit 26 may calculate, for example, the received power to noise power ratio (SNR) based on the virtual antenna used as the index value. The received power to noise power ratio (SNR) based on the virtual antenna used may be a value obtained by dividing the above eigenvalues by the noise power.

(Modification example)
Although the basic configuration has been described above as a basic example, the configuration and operation as described in the following modification examples 1 and 2 may be adopted for further improvement and the like. In addition, a part or all of the

modification

1 and 2 may be combined. Further, the above-mentioned basic example may be applied to the portions not described in the modified examples 1 and 2.

<Modification 1>
The determination unit 27 of the radio base station 2 determines the transmission parameter so as to perform transmission using the antenna which is an index value indicating a better transmission environment among the antennas 10 of the plurality of radio terminal stations 1. May be good. As a result, it is possible to appropriately perform wireless communication in the receiving device that receives the wireless signals transmitted from the plurality of antennas at the same frequency and at the same time by the characteristic variable antenna.

In this case, for example, the determination unit 27 selects an antenna having a low channel correlation value from the antennas 10 of the plurality of wireless terminal stations 1 and performs transmission using the selected antenna according to the transmission parameter. You may instruct the wireless terminal station 1.

Further, the determination unit 27 is, for example, among the antennas 10 of the plurality of wireless terminal stations 1, the transmission capacity C based on the virtual antenna used, the received power for each space transmission, and the received power to noise power ratio (SNR). ) May be selected, and the wireless terminal station 1 may be instructed to perform transmission using the selected antenna by the transmission parameter.

<Modification 2>
The radio base station 2 may be an optical overhanging base station. In this case, the slave station having the characteristic variable antenna 20 and the RF unit 21 and the A / D conversion unit 22 may be connected by an optical fiber. In this case, the A / D conversion unit 22 may determine the timing for sampling the analog signal input from the RF unit 21 via the optical fiber based on the delay time of transmission by the optical fiber.

(Effect of embodiment)
According to the technique according to the present embodiment, it is possible to appropriately perform wireless communication in a receiving device that receives wireless signals transmitted from a plurality of antennas at the same frequency and at the same time by a characteristic variable antenna.

(Summary of embodiments)
This specification describes at least the receiving device, the receiving method, and the program described in each of the following sections.
(Section 1)
A variable antenna with characteristics that receives the wireless signal transmitted from the transmitter while switching the antenna characteristics,
A notification unit that determines a setting related to transmission of the wireless signal based on information on the antenna characteristic of the characteristic variable antenna when receiving the wireless signal, and notifies the transmitting device of the determined setting.
From the radio signal transmitted from the transmitter according to the setting, the first signal received at each time point in which the characteristic variable antenna has the first antenna characteristic and the first signal received at each time point in which the characteristic variable antenna has the second antenna characteristic. A signal extraction unit that extracts the received second signal, and
A receiver equipped with.
(Section 2)
The information about the antenna characteristic of the variable characteristic antenna includes at least one of the correlation value between the propagation channel responses of each antenna characteristic of the variable characteristic antenna and the propagation channel response of each antenna characteristic of the variable characteristic antenna.
The receiving device according to paragraph 1.
(Section 3)
Information on the antenna characteristics of the variable characteristic antenna includes the transmission capacity of each antenna characteristic of the variable characteristic antenna, the received power for each spatial transmission based on each antenna characteristic of the variable characteristic antenna, and each antenna of the variable characteristic antenna. Includes at least one of the received power to noise power ratios based on the characteristics.
The receiving device according to the first or second paragraph.
(Section 4)
The above settings include
Includes settings for at least one of the spatial multiplex, modulation scheme, code rate, and band.
The receiving device according to any one of paragraphs 1 to 3.
(Section 5)
A receiving device equipped with a characteristic variable antenna that receives a wireless signal transmitted from a transmitting device while switching antenna characteristics
A process of determining a setting related to transmission of the wireless signal based on information on the antenna characteristic of the characteristic variable antenna when receiving the wireless signal, and notifying the transmitting device of the determined setting.
From the radio signal transmitted from the transmitter according to the setting, the first signal received at each time point in which the characteristic variable antenna has the first antenna characteristic and the first signal received at each time point in which the characteristic variable antenna has the second antenna characteristic. The process of extracting the received second signal and
Receiving method to execute.
(Section 6)
A program for causing a computer to function as the notification unit and the signal extraction unit in the receiving device according to any one of the items 1 to 4.
(Section 7)
Spatial multiplex, modulation method, coding factor, and band based on the setting information according to the antenna characteristics of the characteristic variable antenna notified from the receiver having the characteristic variable antenna that receives the radio signal while switching the antenna characteristics. And the setting part that sets for at least one of
A generator that generates a MIMO (Multiple Input Multiple Output) signal based on the settings made by the setting unit, and a generation unit.
A transmitter equipped with.

Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It is possible.

1 Wireless terminal station 10 Antenna 11 RF unit 12 D / A conversion unit 13 MIMO signal generation unit 14 Setting unit 2 Wireless base station 20 Characteristic variable antenna 21 RF unit 22 A / D conversion unit 23 Antenna control unit 24 Signal extraction unit 25 MIMO Signal demodulator 26 Index value calculation unit 27 Determination unit 101 Processor 102 Memory 103 Auxiliary storage device 104 Input / output device

Claims

A variable antenna with characteristics that receives the wireless signal transmitted from the transmitter while switching the antenna characteristics,
A notification unit that determines a setting related to transmission of the wireless signal based on information on the antenna characteristic of the characteristic variable antenna when receiving the wireless signal, and notifies the transmitting device of the determined setting.
From the radio signal transmitted from the transmitter according to the setting, the first signal received at each time point in which the characteristic variable antenna has the first antenna characteristic and the first signal received at each time point in which the characteristic variable antenna has the second antenna characteristic. A signal extraction unit that extracts the received second signal, and
A receiver equipped with.
The information about the antenna characteristic of the variable characteristic antenna includes at least one of the correlation value between the propagation channel responses of each antenna characteristic of the variable characteristic antenna and the propagation channel response of each antenna characteristic of the variable characteristic antenna.
The receiving device according to claim 1.
Information on the antenna characteristics of the variable characteristic antenna includes the transmission capacity of each antenna characteristic of the variable characteristic antenna, the received power for each spatial transmission based on each antenna characteristic of the variable characteristic antenna, and each antenna of the variable characteristic antenna. Includes at least one of the received power to noise power ratios based on the characteristics.
The receiving device according to claim 1 or 2.
The above settings include
Includes settings for at least one of the spatial multiplex, modulation scheme, code rate, and band.
The receiving device according to any one of claims 1 to 3.
A receiving device equipped with a characteristic variable antenna that receives a wireless signal transmitted from a transmitting device while switching antenna characteristics.
A process of determining a setting related to transmission of the wireless signal based on information on the antenna characteristic of the characteristic variable antenna when receiving the wireless signal, and notifying the transmitting device of the determined setting.
From the radio signal transmitted from the transmitter according to the setting, the first signal received at each time point in which the characteristic variable antenna has the first antenna characteristic and the first signal received at each time point in which the characteristic variable antenna has the second antenna characteristic. The process of extracting the received second signal and
Receiving method to execute.
A program for making a computer function as the notification unit and the signal extraction unit in the receiving device according to any one of claims 1 to 4.
Spatial multiplex, modulation method, coding factor, and band based on the setting information according to the antenna characteristics of the characteristic variable antenna notified from the receiver having the characteristic variable antenna that receives the radio signal while switching the antenna characteristics. And the setting part that sets for at least one of
A generator that generates a MIMO (Multiple Input Multiple Output) signal based on the settings made by the setting unit, and a generation unit.
A transmitter equipped with.