JP7415687B2 - Wireless communication device and wireless communication method - Google Patents

Description

The present invention relates to a wireless communication device and a wireless communication method.

As high-speed wireless access systems using radio waves in the 5 GHz band, there are wireless LANs based on the IEEE802.11a standard, 11n standard, and 11ac standard. The 11a standard is based on an orthogonal frequency division multiplexing (OFDM) modulation method, stabilizes characteristics in a multipath fading environment, and achieves a maximum transmission speed of 54 Mbit/s. Furthermore, the 11n standard supports MIMO (Multiple Input Multiple Output), which performs space division multiplexing on the same radio channel using multiple antennas, and channel bonding, which uses two 20 MHz frequency channels simultaneously and uses a 40 MHz frequency channel. The technology is used to achieve transmission speeds of up to 600 Mbit/s. In addition, the 11ac standard includes channel bonding technology that simultaneously uses up to eight 20MHz frequency channels as a maximum 160MHz frequency channel, and downlink technology that simultaneously transmits different signals to multiple destinations on the same wireless channel. It utilizes multi-user MIMO technology and other technologies to achieve faster and more efficient wireless communication than the 11n standard.

Currently, the IEEE 802.11ax standard is being formulated with a focus on improving transmission efficiency in addition to improving transmission speed. 11ax is scheduled to promote spatial frequency reuse through simultaneous transmission, improve the efficiency of OFDM modulation, and add uplink and downlink OFDMA transmission and uplink multi-user MIMO transmission as multi-user transmission.

Furthermore, in order to perform high-speed transmission, a technique is known in which interference waves are suppressed using a CMA (Constant Modulus Algorithm) adaptive array (see, for example, Non-Patent Document 1).

Kentaro Nishimori and two others, “Operation analysis of CMA adaptive array for QAM signals”, IEICE Transactions B-II, December 1996, Vol. J79-B-II No. 12, p. 984-993

However, with conventional technology using CMA adaptive arrays, it is necessary to perform processing using received signal vectors of all antenna characteristics, so communication quality may deteriorate depending on the amount of received signal interference and noise. Sometimes I put it away.

In addition, in recent years in wireless communication systems such as 5G, the number of antennas has increased dramatically, such as in massive MIMO transmission, and processing the received signals of all antennas at once requires a large amount of calculation processing. It can become too much.

An object of the present invention is to provide a wireless communication device and a wireless communication method that can improve communication quality while suppressing the amount of calculation processing for a plurality of received signals.

A wireless communication device according to one aspect of the present invention includes a plurality of antennas, a beam forming section, a control section, a signal division section, an analysis section, a selection section, and a demodulation section, and includes a plurality of antennas. receives the transmitted signal with the directivity changeable multiple times within one symbol of the modulated transmitted signal under the control of the control unit, and the beam forming unit receives the received signals received by the plurality of antennas . outputting a received signal pattern by changing the amplitude and phase of the received signal; The signal dividing section controls the signal output by the beam forming section to output a plurality of reception signal patterns by changing the amplitude and phase of the reception signal multiple times, and the signal division section outputs a plurality of reception signal patterns by changing the amplitude and phase of the reception signal multiple times. The analysis unit calculates the throughput when demodulating the signals by reducing the number of signals using pilot signals from among all the combinations of the plurality of signals divided by the signal division unit. The selection section performs an analysis to identify a combination of signals with a maximum packet error rate or a combination of signals with a minimum packet error rate, and the selection section selects the combination of signals that the signal division section divides based on the analysis result of the analysis section. The present invention is characterized in that a part of the plurality of signals is selected, and the demodulation section performs MIMO-OFDM demodulation on the signal selected by the selection section.

A wireless communication method according to one aspect of the present invention includes a reception step, a beam forming step, a control step, a signal division step, an analysis step, a selection step, and a demodulation step, and in the reception step, modulation The directivity of a plurality of antennas can be changed multiple times within one symbol of the transmitted signal, and the transmitted signal is received by controlling the directivity of a plurality of antennas within one symbol of the transmitted signal, and in the beam forming step, A received signal pattern is output by changing the amplitude and phase, and in the control step, the beam forming step is performed within one symbol of the received signal while controlling to minimize a distortion component of an envelope of the received signal. control to output a plurality of received signal patterns by changing the amplitude and phase of the received signal multiple times, and in the signal dividing step, the signal output by the beam forming step is controlled to be outputted into a plurality of received signal patterns, respectively. The throughput is determined by dividing into a plurality of corresponding signals, and in the analysis step , demodulating by reducing the number of signals using a pilot signal from among all combinations of the plurality of signals divided by the signal division step. An analysis is performed to identify the combination of signals that has the maximum or the combination of signals that has the minimum packet error rate, and in the selection step, based on the results of the analysis in the analysis step, the plurality of signal combinations divided in the signal division step are The demodulation step performs MIMO-OFDM demodulation on the signal selected in the selection step.

According to the present invention, it is possible to improve communication quality while suppressing the amount of calculation processing for a plurality of received signals.

1 is a diagram illustrating a configuration example of a wireless communication system according to an embodiment. It is a diagram showing an example of the configuration of a wireless terminal station. FIG. 1 is a diagram illustrating an example configuration of a wireless base station according to an embodiment. (a) is a diagram showing a received signal pattern when the peak direction is 0 degrees. (b) is a diagram showing a received signal pattern when the peak direction is 90 degrees. (c) is a diagram showing a received signal pattern when the peak direction is 180 degrees. (d) is a diagram showing a received signal pattern when the peak direction is 270 degrees. FIG. 2 is a diagram showing an overview of the operating principle of CMA. FIG. 3 is a diagram illustrating an example of an uplink communication sequence in a wireless communication system according to an embodiment. It is a figure showing the 1st modification of the radio terminal station which the radio communication system concerning an embodiment has. It is a figure showing the 2nd modification of the radio terminal station which the radio communication system concerning an embodiment has. FIG. 3 is a diagram illustrating a configuration example of a wireless base station of a comparative example.

First, the background of the invention will be explained. FIG. 9 is a diagram illustrating a configuration example of a wireless base station as a comparative example. The radio base station 4 includes a plurality of antennas 40 , a beam forming section 41 , an RF (Radio Frequency) section 42 , an A/D converting section 43 , a control section 44 , a signal dividing section 45 , and a demodulating section 46 .

In addition, in FIG. 9, only the main functional blocks required for the wireless base station 4 to perform reception are described, and other functional blocks that are generally installed in the wireless base station are not described. .

Antenna 40 receives, for example, a MIMO-OFDM signal. The antenna 40 is connected to the beam forming section 41 and outputs the received MIMO-OFDM signal to the beam forming section 41.

The beam forming unit 41 changes the amplitude and phase of the received signal received by the antenna 40 according to a control signal input from the control unit 44, synthesizes the changed signal (received signal pattern), and generates an RF signal. The output signal is output to the section 42. For example, the beam forming unit 41 outputs a plurality of (for example, P) received signal patterns within one symbol of the received signal under the control of the control unit 44.

The RF section 42 performs analog processing such as amplification, frequency change, and filtering on the MIMO-OFDM signal input from the beam forming section 41 and outputs the processed signal to the A/D conversion section 43. In other words, the RF unit 42 is equipped with the RF front end function of a general wireless device.

The A/D conversion section 43 converts the analog signal input from the RF section 42 into a digital signal, and outputs the digital signal to the signal division section 45 . Further, the A/D converter 43 notifies the controller 44 of the sampling period. Here, the A/D converter 43 performs sampling at a rate P times the symbol rate of the received signal.

The control unit 44 controls each unit making up the wireless base station 4. For example, the control unit 44 controls the beam forming unit 41 to change the amplitude and phase of the received signal a plurality of times (for example, P times) while the antenna 40 receives a signal of one OFDM symbol. The forming unit 41 is caused to generate a plurality of (for example, P) received signal patterns.

The signal division section 45 divides the signal input from the A/D conversion section 43 for each antenna characteristic controlled by the control section 44 and outputs the divided signal to the demodulation section 46 .

The demodulator 46 performs MIMO-OFDM demodulation processing defined in wireless LAN systems and the like on the signal divided by the signal divider 45.

That is, the wireless base station 4 of the comparative example has a configuration in which the beam forming unit 41 combines all the signals whose amplitudes and phases have been changed, and the demodulating unit 46 demodulates the combined signals.

At this time, the communication quality of the radio base station 4 may deteriorate depending on the interference of the received signal or the magnitude of noise. Furthermore, in recent years in wireless communication systems such as 5G, the number of antennas has increased dramatically, such as in massive MIMO transmission, and processing the received signals of all antennas at once requires a large amount of calculation processing. It can become too much.

Next, a configuration example of a wireless communication system according to an embodiment will be described. FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to an embodiment. As shown in FIG. 1, the wireless communication system includes, for example, a wireless base station 1 as a wireless communication device, and n wireless terminals existing within a service area that is a range where wireless communication is possible with respect to the wireless base station 1. It has stations 2-1 to 2-n.

The wireless terminal stations 2-1 to 2-n transmit uplink signals to the wireless base station 1 asynchronously. Hereinafter, when one of the plurality of configurations, such as wireless terminal stations 2-1 to 2-n, is not specified, it will simply be abbreviated as wireless terminal station 2, etc.

FIG. 2 is a diagram showing an example of the configuration of the wireless terminal station 2. As shown in FIG. As shown in FIG. 2, the wireless terminal station 2 includes, for example, a modulation section 20, a D/A conversion section 21, an RF section 22, and an antenna 23. In addition, in FIG. 2, only the main functional blocks required for the wireless terminal station 2 to perform transmission are described, and other functional blocks that are generally installed in the wireless terminal station are not described. .

The modulator 20 performs a MIMO-OFDM modulation process defined in, for example, a wireless LAN system, and outputs a modulated signal to the D/A converter 21 .

The D/A converter 21 converts the digital signal input from the modulator 20 into an analog signal, and outputs the analog signal to the RF section 22 .

The RF unit 22 performs processing such as amplification, frequency change, and filtering on the signal input from the D/A conversion unit 21 and outputs the processed transmission signal to the antenna 23. That is, the RF unit 22 has the function of an RF front end of a general wireless communication device.

The antenna 23 radiates the transmission signal input from the RF section 22 into the air.

FIG. 3 is a diagram showing a configuration example of the wireless base station 1 according to an embodiment. The radio base station 1 includes a plurality of antennas 10, a beam forming section 11, an RF section 12, an A/D converting section 13, a controlling section 14, a signal dividing section 15, a selecting section 16, an analyzing section 17, and a demodulating section 18. .

Note that in FIG. 3, only the main functional blocks required for the wireless base station 1 to perform reception are shown, and other functional blocks that are generally installed in a wireless base station are not shown. .

Antenna 10 receives, for example, a MIMO-OFDM signal. The antenna 10 is connected to the beam forming section 11 and outputs the received MIMO-OFDM signal to the beam forming section 11. More specifically, the antenna 10 receives the transmission signal while changing the directivity multiple times within one symbol of the modulated transmission signal.

The beam forming unit 11 changes the amplitude and phase of the received signal received by the antenna 10 according to a control signal input from the control unit 14, synthesizes the changed signals (received signal pattern), and generates an RF signal. It outputs to section 12. For example, the beam forming unit 11 outputs a plurality of (for example, P) received signal patterns within one symbol of the received signal under the control of the control unit 14.

FIG. 4 is a diagram showing an example of a received signal pattern (antenna characteristics) output by the beam forming section 11. FIG. 4(a) is a diagram showing a received signal pattern when the peak direction is 0 degrees. FIG. 4(b) is a diagram showing a received signal pattern when the peak direction is 90 degrees. FIG. 4(c) is a diagram showing a received signal pattern when the peak direction is 180 degrees. FIG. 4(d) is a diagram showing a received signal pattern when the peak direction is 270 degrees.

For example, the beam forming unit 11 performs synthesis so that a main lobe, a side lobe, and a back lobe are generated in four directions shifted by 90 degrees as shown in FIG.

The RF unit 12 (FIG. 3) performs analog processing such as amplification, frequency change, and filtering on the MIMO-OFDM signal input from the beam forming unit 11, and sends the processed signal to the A/D converter 13. Output. That is, the RF unit 12 is equipped with the RF front end function of a general wireless device.

The A/D conversion section 13 converts the analog signal input from the RF section 12 into a digital signal, and outputs the digital signal to the signal division section 15 . The A/D converter 13 also notifies the controller 14 of the sampling period. Here, the A/D converter 13 performs sampling at a rate P times the symbol rate of the received signal.

The control unit 14 controls each unit making up the wireless base station 1. For example, the control unit 14 controls the beam forming unit 11 to change the amplitude and phase of the received signal a plurality of times (for example, P times) while the antenna 10 receives a signal of one OFDM symbol. The forming unit 11 is caused to generate a plurality (for example, P) of received signal patterns.

Here, the control unit 14 controls the beam forming unit 11 to change the amplitude and phase of the received signal multiple times within one symbol of the received signal while controlling to minimize the distortion component of the envelope of the received signal. control to output multiple received signal patterns.

The signal division section 15 divides the signal input from the A/D conversion section 13 into a plurality of signals for each antenna characteristic controlled by the control section 14, and outputs the signals to the selection section 16.

The selection unit 16 outputs the P signals input from the signal division unit 15 to the analysis unit 17, and outputs the P signals input from the signal division unit 15 according to the instruction signal input from the analysis unit 17. Q signals (where 2≦Q<P) are selected from among the following. Then, the selection section 16 outputs the selected Q signals to the demodulation section 18.

The analysis unit 17 selects a combination of Q signals that provides the highest communication quality when the number of signals is reduced to Q and demodulated from among all combinations of the P signals input from the selection unit 16. Perform an analysis to identify the

Here, it is assumed that the combination of signals with the highest communication quality is the combination of signals with the maximum throughput, the combination of signals with the minimum packet error rate, or the like.

More specifically, the analysis unit 17 calculates the communication quality when all combinations of P signals are demodulated, and calculates, for example, the combination of Q signals with the maximum throughput or the packet error rate. A combination of Q signals with the minimum is specified, and the result of the combination of the specified signals is output to the selection section 16 as an instruction signal.

The demodulation unit 18 performs interference wave suppression by CMA processing of received signals (symbols) including communication data and MIMO-OFDM demodulation processing on the Q signals inputted from the selection unit 16.

Note that the radio base station 1 changes the antenna characteristics P times within one symbol of the received signal, and the A/D converter 13 performs A/D conversion at a rate P times the symbol rate of the received signal. Obtain P virtual branches with a plurality of different propagation characteristics.

Conventionally, in order to perform MIMO-OFDM demodulation processing using P different received signals acquired within one OFDM symbol as array data, it was necessary to acquire propagation channels at different times.

In contrast, the wireless base station 1 according to one embodiment uses a constant envelope algorithm (CMA) for weight control of the array antenna. In CMA, the weights are controlled so that the distortion component of the envelope of the array output is minimized using the property that the transmitted signal has a constant envelope.

FIG. 5 is a diagram showing an overview of the operating principle of CMA. CMA is characterized by controlling weights so as to keep the envelope of the output signal of the array antenna constant. For example, in CMA, a first arriving wave, which is a desired wave, and a second arriving wave are combined to generate a composite wave y (output voltage of an array antenna), and the composite wave y and a desired envelope value σ are combined. An evaluation is performed using a CMA evaluation function expressed by the following equation (1). Note that E[·] in equation (1) represents an operation for calculating an expected value.

Then, in CMA, the second arriving wave is suppressed from the composite wave y, and the first arriving wave is extracted. X shown in the above equation (1) becomes the received signal vector of the array antenna.

However, in the wireless base station 1, there is only one system of signals output from the array antenna. Therefore, instead of X obtained from different antennas of the array antenna, the radio base station 1 uses a vector consisting of P received signals with different antenna characteristics.

Since CMA is an algorithm that does not require timing synchronization, it does not require timing synchronization or propagation channel estimation. Note that the basic characteristics of CMA are also described in Non-Patent Document 1.

In other words, the control unit 14 controls the beam forming unit 11 to change the amplitude and phase of the received signal multiple times within one symbol of the received signal while controlling the distortion component of the envelope of the received signal to a minimum. It is controlled to output multiple received signal patterns.

FIG. 6 is a diagram illustrating an example of an uplink communication sequence in a wireless communication system according to an embodiment. As shown in FIG. 6, in the wireless communication system according to one embodiment, it is assumed that, for example, wireless terminal stations 2-1 and 2-2 transmit signals asynchronously. At this time, if the signal transmitted by the wireless terminal station 2-1 is an uplink MIMO-OFDM signal that is a desired wave, the signal transmitted by the wireless terminal station 2-2 is an interference signal.

In the radio base station 1, even if the receiving port is one element, the A/D converter 13 performs conversion by oversampling within one symbol, so that a plurality of branches with different antenna characteristics can be obtained, and the received signal By applying CMA that achieves interference cancellation to different branches of multiple patterns, timing synchronization and channel estimation become unnecessary.

Next, a modification of the wireless communication system will be described. FIG. 7 is a diagram showing a first modification example (wireless terminal station 2a) of the wireless terminal station 2 included in the wireless communication system according to the embodiment.

As shown in FIG. 7, the wireless terminal station 2a includes a pilot signal generation section 24, a modulation section 25, a D/A conversion section 21, an RF section 22, and an antenna 23. In addition, the same code|symbol is attached to the structure substantially the same as the structure mentioned above.

The pilot signal generation unit 24 generates a signal for the radio base station 1 to calculate the ratio of signal power and interference power and a signal for the radio base station 1 to calculate the bit error rate as pilot signals, and generates a signal for the radio base station 1 to calculate the bit error rate. Output for 25.

Here, it is assumed that the pilot signal is a signal in which 0's and 1's are arranged regularly, and that this regularity is also shared by the radio base station 1.

The modulator 25 performs MIMO-OFDM modulation processing including the pilot signal input from the pilot signal generator 24 and outputs the modulated signal to the D/A converter 21.

In a modified example of the wireless communication system, the analysis unit 17 shown in FIG. 3 calculates the desired signal power and interference power for each beam using the pilot signal, and selects a combination of Q signals that maximizes the throughput. Identify. Alternatively, the analysis unit 17 calculates the packet error rate using the pilot signal and identifies a combination of Q signals that minimizes the packet error rate.

That is, in the modified example of the wireless communication system, the wireless terminal station 2a transmits a signal including a pilot signal so as to reduce the calculation processing load on the wireless base station 1.

Furthermore, the wireless terminal station 2a may be further provided with a beam forming section 26 like the wireless terminal station 2b shown in FIG. The beam forming unit 26 controls the amplitude and phase of the signal so that the antenna 23 forms a beam that improves, for example, the throughput of the signal transmitted by the wireless terminal station 2b.

In this way, in the wireless communication system according to one embodiment, the wireless base station 1 identifies a combination of Q signals that provides the highest communication quality, reduces the number of signals from P to Q, and performs demodulation. Therefore, communication quality can be improved while suppressing the amount of calculation processing for a plurality of received signals.

DESCRIPTION OF SYMBOLS 1... Wireless base station, 2-1 to 2-n, 2a, 2b... Wireless terminal station, 10... Antenna, 11... Beam forming section, 12... RF section, 13...・A/D conversion section, 14... Control section, 15... Signal division section, 16... Selection section, 17... Analysis section, 18... Demodulation section, 20, 25... Modulation 21...D/A conversion unit, 22...RF unit, 23...antenna, 24...pilot signal generation unit

Claims (2)

It has a plurality of antennas, a beam forming section, a control section, a signal division section, an analysis section, a selection section, and a demodulation section,
The plurality of antennas include:
receiving the transmitting signal with the directivity changeable multiple times within one symbol of the modulated transmitting signal under the control of the control unit;
The beam forming section is
outputting a received signal pattern by changing the amplitude and phase of the received signal received by the plurality of antennas;
The control unit includes:
The beam forming unit changes the amplitude and phase of the received signal multiple times within one symbol of the received signal, while controlling to minimize the distortion component of the envelope of the received signal, thereby forming a plurality of received signals. control to output the pattern,
The signal dividing section is
dividing the signal output by the beam forming unit into a plurality of signals each corresponding to a plurality of received signal patterns;
The analysis section includes:
Among all the combinations of the plurality of signals divided by the signal division section, the combination of signals that has the maximum throughput or the minimum packet error rate when demodulated by reducing the number of signals using pilot signals. Perform analysis to identify the combination of signals that will result in
The selection section is
Selecting a part of the plurality of signals divided by the signal dividing unit based on the results analyzed by the analyzing unit,
The demodulation section includes:
A wireless communication device, characterized in that the signal selected by the selection unit is subjected to MIMO-OFDM demodulation. including a receiving process, a beam forming process, a control process, a signal division process, an analysis process, a selection process, and a demodulation process,
In the receiving step,
The directivity of the plurality of antennas can be changed multiple times within one symbol of the modulated transmission signal under the control of a control unit, and the transmission signal is received;
In the beam forming step,
outputting a received signal pattern by changing the amplitude and phase of the received signal received in the receiving step;
In the control step,
A plurality of received signals are generated by changing the amplitude and phase of the received signal multiple times by the beam forming step within one symbol of the received signal while controlling to minimize the distortion component of the envelope of the received signal. control to output the pattern,
In the signal dividing step,
dividing the signal output by the beam forming step into a plurality of signals each corresponding to a plurality of received signal patterns;
In the analysis step,
Among all the combinations of the plurality of signals divided by the signal division step, the combination of signals that has the maximum throughput or the minimum packet error rate when demodulated by reducing the number of signals using pilot signals. Perform analysis to identify the combination of signals that will result in
In the selection step,
Selecting a part of the plurality of signals divided by the signal division step based on the results analyzed by the analysis step,
In the demodulation step,
A wireless communication method, comprising performing MIMO-OFDM demodulation on the signal selected in the selection step.

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