JP2021145210A - Radio communication device and radio communication method - Google Patents

Abstract

To improve communication quality while suppressing a calculation processing amount to a plurality of reception signals.SOLUTION: A radio communication device comprises: a plurality of antennas each for receiving a transmission signal while changing directivity a plurality of times within one symbol of a modulated transmission signal; a beam forming unit for outputting a reception signal pattern by changing amplitudes and phases of reception signals received by the plurality of antennas; a signal dividing unit for dividing a signal which is outputted by the beam forming unit, into a plurality of signals; an analysis unit which performs analysis for identifying a combination of signals to most improve communication quality in the case where demodulation is performed while reducing the number of signals, from among all the combinations of the plurality of signals divided by the signal dividing unit; a selection unit for selecting a part of the plurality of signals divided by the signal dividing unit on the basis of a result analyzed by the analysis unit; and a demodulation unit which performs MIMO-OFDM demodulation on the signal selected by the selection unit.SELECTED DRAWING: Figure 3

Description

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

As a high-speed wireless access system using radio waves in the 5 GHz band, there is a wireless LAN based on the IEEE802.11a standard, the 11n standard, and the 11ac standard. In the 11a standard, based on the Orthogonal Frequency Division Multiplexing (OFDM) modulation method, the characteristics in a multipath fading environment are stabilized, and a maximum transmission speed of 54 Mbit / s is realized. Furthermore, in the 11n standard, MIMO (Multiple Input Multiple Output), which performs time division multiplexing on the same wireless channel using multiple antennas, and channel bonding, which uses two 20 MHz frequency channels at the same time and uses a 40 MHz frequency channel. Using technology, we have achieved transmission speeds of up to 600 Mbit / s. In addition, in the 11ac standard, channel bonding technology that uses up to eight 20 MHz frequency channels at the same time and uses them as a maximum 160 MHz frequency channel, and downlinks that simultaneously transmit different signals to multiple destinations on the same wireless channel. By utilizing the multi-user MIMO technology of the above, wireless communication that is faster and more efficient than the 11n standard is realized.

Currently, the IEEE802.11ax standard is being formulated with a focus on improving transmission efficiency in addition to improving transmission speed. In 11ax, it is planned to promote spatial frequency reuse by simultaneous transmission, improve the efficiency of OFDM modulation method, and add OFDMA transmission of upper and lower lines and multi-user MIMO transmission of uplink as multi-user transmission.

Further, in order to perform high-speed transmission, a technique of suppressing an interference wave by using a CMA (Constant Modulus Algorithm) adaptive array is known (see, for example, Non-Patent Document 1).

Kentaro Nishimori, 2 outsiders, "Analysis of CMA Adaptive Array Behavior for QAM Signals", IEICE Transactions B-II, December 1996, Vol. J79-B-II No. 12, p. 984-993

However, in the conventional technology using the CMA adaptive array, it is necessary to perform processing using the received signal vectors of all antenna characteristics, so that the communication quality deteriorates depending on the interference of the received signal and the magnitude of noise. It may end up.

Further, in recent wireless communication systems such as 5G, the number of antennas is increasing dramatically as in massive MIMO transmission, and the amount of calculation processing is required to process the received signals of all antennas at once. It can be too much.

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

The wireless communication device according to one aspect of the present invention includes a plurality of antennas for receiving the transmission signal and reception received by the plurality of antennas while changing the directivity a plurality of times within one symbol of the modulated transmission signal. The beam forming unit that outputs a received signal pattern by changing the amplitude and phase of the signal, and the beam forming within one symbol of the received signal while controlling so as to minimize the distortion component of the envelope of the received signal. A control unit that controls the unit to output a plurality of received signal patterns by changing the amplitude and phase of the received signal a plurality of times, and a signal division unit that divides the signal output by the beam forming unit into a plurality of signals. An analysis unit that performs analysis to identify the combination of signals having the highest communication quality when the number of signals is reduced and demodulated from all the combinations of the plurality of signals divided by the signal division unit. It has a selection unit that selects a part of a plurality of signals divided by the signal division unit based on the result analyzed by the analysis unit, and a demodulation unit that demolishes the signal selected by the selection unit by MIMO-OFDM. It is a feature.

In the wireless communication method according to one aspect of the present invention, the reception step of receiving the transmission signal and the amplitude and phase of the received reception signal are changed while changing the directivity a plurality of times within one symbol of the modulated transmission signal. A plurality of amplitudes and phases of the received signal are set within one symbol of the received signal while controlling so as to minimize the distortion component of the envelope of the received signal and the beam forming step of changing and outputting the received signal pattern. A control process that controls to output a plurality of received signal patterns by changing the number of times, a signal dividing process that divides the output multiple received signal patterns into a plurality of signals, and all combinations of the divided plurality of signals. From the analysis process, which identifies the combination of signals with the highest communication quality when the number of signals is reduced and demodulated, and a part of a plurality of divided signals is selected based on the analysis result. It is characterized by including a selection step and a demodulation step of demolishing the selected signal by MIMO-OFDM.

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

It is a figure which shows the configuration example of the wireless communication system which concerns on one Embodiment. It is a figure which shows the configuration example of a wireless terminal station. It is a figure which shows the configuration example of the radio base station which concerns on one Embodiment. (A) is a figure which shows the received signal pattern when the peak direction is 0 degree. (B) is a figure which shows the received signal pattern when the peak direction is 90 degrees. (C) is a figure which shows the received signal pattern when the peak direction is 180 degrees. (D) is a figure which shows the received signal pattern when the peak direction is 270 degrees. It is a figure which shows the outline of the operation principle of CMA. It is a figure which shows an example of the communication sequence of the uplink in the wireless communication system which concerns on one Embodiment. It is a figure which shows the 1st modification of the wireless terminal station which the wireless communication system which concerns on embodiment have. It is a figure which shows the 2nd modification of the wireless terminal station which the wireless communication system which concerns on embodiment have. It is a figure which shows the configuration example of the radio base station of the comparative example.

First, the background leading to the present invention will be described. FIG. 9 is a diagram showing a configuration example of a radio base station of a comparative example. The radio base station 4 has a plurality of antennas 40, a beam forming unit 41, an RF (Radio Frequency) unit 42, an A / D conversion unit 43, a control unit 44, a signal dividing unit 45, and a demodulation unit 46.

Note that, in FIG. 9, only the main functional blocks required for the radio base station 4 to perform reception are shown, and other functional blocks generally mounted on the radio base station are not shown. ..

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

The beam forming unit 41 changes the amplitude and phase of the received signal received by the antenna 40 according to the control signal input from the control unit 44, synthesizes the changed signal (received signal pattern), and RFs the received signal. Output to unit 42. For example, the beam forming unit 41 outputs a plurality of (for example, P) received signal patterns in one symbol of the received signal according to the control of the control unit 44.

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

The A / D conversion unit 43 changes the analog signal input from the RF unit 42 into a digital signal and outputs the analog signal to the signal division unit 45. Further, the A / D conversion unit 43 notifies the control unit 44 of the sampling cycle. Here, the A / D conversion unit 43 performs sampling at a speed P times that of the symbol rate of the received signal.

The control unit 44 controls each unit constituting the radio 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 the signal of one OFDM symbol. The forming unit 41 is made to generate a plurality of (for example, P) received signal patterns.

The signal division unit 45 divides the signal input from the A / D conversion unit 43 according to the antenna characteristics controlled by the control unit 44, and outputs the signal to the demodulation unit 46.

The demodulation unit 46 performs MIMO-OFDM demodulation processing defined by a wireless LAN system or the like on the signal divided by the signal division unit 45.

That is, the radio base station 4 of the comparative example has a configuration in which the beam forming unit 41 synthesizes all the signals whose amplitude and phase are changed, and the demodulating unit 46 demodulates them.

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

Next, a configuration example of the wireless communication system according to the embodiment will be described. FIG. 1 is a diagram showing 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 in a service area within a range in which wireless communication is possible with the wireless base station 1. It has stations 2-1 to 2-n.

The radio terminal stations 2-1 to 2-n asynchronously transmit an uplink signal to the radio base station 1. Hereinafter, when any one of a plurality of configurations such as wireless terminal stations 2-1 to 2-n is not specified, it is simply abbreviated as wireless terminal station 2 and the like.

FIG. 2 is a diagram showing a configuration example of the wireless terminal station 2. As shown in FIG. 2, the radio terminal station 2 has, for example, a modulation unit 20, a D / A conversion unit 21, an RF unit 22, and an antenna 23. Note that, in FIG. 2, only the main functional blocks required for the wireless terminal station 2 to perform transmission are shown, and other functional blocks generally mounted on the wireless terminal station are not shown. ..

The modulation unit 20 performs MIMO-OFDM modulation processing defined by, for example, a wireless LAN system, and outputs the modulated signal to the D / A conversion unit 21.

The D / A conversion unit 21 changes the digital signal input from the modulation unit 20 into an analog signal and outputs it to the RF unit 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 the RF front end of a general wireless communication device.

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

FIG. 3 is a diagram showing a configuration example of the radio base station 1 according to the embodiment. The radio base station 1 has a plurality of antennas 10, a beam forming unit 11, an RF unit 12, an A / D conversion unit 13, a control unit 14, a signal dividing unit 15, a selection unit 16, an analysis unit 17, and a demodulation unit 18. ..

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

The antenna 10 receives, for example, a MIMO-OFDM signal. The antenna 10 is connected to the beam forming unit 11 and outputs the received MIMO-OFDM signal to the beam forming unit 11. More specifically, the antenna 10 receives the transmission signal while changing the directivity a plurality of 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 the control signal input from the control unit 14, synthesizes the changed signal (received signal pattern), and RFs the received signal. Output to unit 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 according to the control of the control unit 14.

FIG. 4 is a diagram showing an example of a received signal pattern (antenna characteristic) output by the beam forming unit 11. FIG. 4A is a diagram showing a received signal pattern when the peak direction is 0 degrees. FIG. 4B is a diagram showing a received signal pattern when the peak direction is 90 degrees. FIG. 4C is a diagram showing a received signal pattern when the peak direction is 180 degrees. FIG. 4D is a diagram showing a received signal pattern when the peak direction is 270 degrees.

For example, the beam forming unit 11 synthesizes so that the main lobe, side lobe, and back lobe are generated in four directions shifted by 90 ° 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 transmits the processed signal to the A / D conversion unit 13. Output. That is, the RF unit 12 is equipped with the function of the RF front end of a general wireless device.

The A / D conversion unit 13 changes the analog signal input from the RF unit 12 into a digital signal and outputs the analog signal to the signal division unit 15. Further, the A / D conversion unit 13 notifies the control unit 14 of the sampling cycle. Here, the A / D conversion unit 13 performs sampling at a speed P times that of the symbol rate of the received signal.

The control unit 14 controls each unit constituting the radio 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 the signal of one OFDM symbol. The forming unit 11 is made to generate a plurality of (for example, P) received signal patterns.

Here, the control unit 14 controls so as to minimize the distortion component of the envelope of the received signal, and the beam forming unit 11 changes the amplitude and phase of the received signal a plurality of times within one symbol of the received signal. Controls to output multiple received signal patterns.

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

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

The analysis unit 17 combines all the combinations of P signals input from the selection unit 16 with Q signals having the highest communication quality when the number of signals is reduced to Q and demodulated. Perform an analysis to identify.

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

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

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

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

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

On the other hand, the radio base station 1 according to the embodiment uses a constant envelope algorithm (CMA) for weight control of the array antenna. In CMA, the weight is controlled so that the distortion component of the envelope of the array output, which utilizes the property that the transmitted signal has a constant envelope, is minimized.

FIG. 5 is a diagram showing an outline of the operating principle of CMA. The CMA is characterized in that the weight is controlled so that the envelope of the output signal of the array antenna is constant. For example, in CMA, the desired first arrival wave and the second arrival wave are combined to generate a composite wave y (output voltage of the array antenna), and the composite wave y and the desired wrapping line value σ are obtained. The evaluation is performed by the evaluation function of CMA represented by the following equation (1). Note that E [・] in the equation (1) represents an operation for obtaining an expected value.

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

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

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

That is, the control unit 14 controls so as to minimize the distortion component of the envelope of the received signal, and the beam forming unit 11 changes the amplitude and phase of the received signal a plurality of times within one symbol of the received signal. It is controlled to output multiple received signal patterns.

FIG. 6 is a diagram showing an example of an uplink communication sequence in the wireless communication system according to the embodiment. As shown in FIG. 6, in the wireless communication system according to the 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 having different antenna characteristics can be obtained, and the received signal can be received. By applying CMA, which realizes interference elimination only by itself, to different branches of a plurality of patterns, timing synchronization and channel estimation become unnecessary.

Next, a modified example of the wireless communication system will be described. FIG. 7 is a diagram showing a first modification (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 radio terminal station 2a has a pilot signal generation unit 24, a modulation unit 25, a D / A conversion unit 21, an RF unit 22, and an antenna 23. The same reference numerals are given to substantially the same configurations as those described above.

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

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

The modulation unit 25 performs the MIMO-OFDM modulation process including the pilot signal input from the pilot signal generation unit 24, and outputs the modulated signal to the D / A conversion unit 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 having the maximum throughput. Identify. Alternatively, the analysis unit 17 calculates the packet error rate using the pilot signal, and specifies the combination of Q signals that minimizes the packet error rate.

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

Further, the wireless terminal station 2a may be further provided with a beam forming unit 26 as in 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 for improving the throughput of the signal transmitted by the wireless terminal station 2b, for example.

As described above, in the wireless communication system according to the embodiment, the wireless base station 1 identifies the combination of Q signals having the highest communication quality, reduces the number of signals from P to Q, and performs demodulation. Therefore, it is possible to improve the communication quality while suppressing the amount of calculation processing for a plurality of received signals.

1 ... Radio base station, 2-1-2-n, 2a, 2b ... Radio terminal station, 10 ... Antenna, 11 ... Beam forming section, 12 ... RF section, 13 ... A / D conversion unit, 14 ... control unit, 15 ... signal division unit, 16 ... selection unit, 17 ... analysis unit, 18 ... demodulation unit, 20, 25 ... modulation Unit, 21 ... D / A conversion unit, 22 ... RF unit, 23 ... antenna, 24 ... pilot signal generation unit

Claims (4)

A plurality of antennas that receive the transmitted signal while changing the directivity a plurality of times within one symbol of the modulated transmission signal.
A beam forming unit that outputs a received signal pattern by changing the amplitude and phase of the received signal received by the plurality of antennas.
A plurality of received signals are received by the beam forming unit changing the amplitude and phase of the received signal a plurality of times within one symbol of the received signal while controlling so as to minimize the distortion component of the envelope of the received signal. A control unit that controls to output a pattern,
A signal dividing unit that divides the signal output by the beam forming unit into a plurality of signals, and a signal dividing unit.
An analysis unit that performs analysis to identify the combination of signals having the highest communication quality when demodulated by reducing the number of signals from all combinations of a plurality of signals divided by the signal division unit.
A selection unit that selects a part of a plurality of signals divided by the signal division unit based on the result analyzed by the analysis unit, and a selection unit.
A wireless communication device including a demodulation unit that demodulates a signal selected by the selection unit by MIMO-OFDM. The analysis unit
Based on the calculation result of the signal power and interference power of the transmission signal or the calculation result of the packet error rate of the transmission signal, the combination of signals having the highest communication quality when demodulated by reducing the number of signals is specified. The wireless communication device according to claim 1, wherein the analysis is performed. A receiving process of receiving the transmitted signal while changing the directivity a plurality of times within one symbol of the modulated transmission signal.
A beam forming process that outputs a received signal pattern by changing the amplitude and phase of the received received signal,
A plurality of received signal patterns are output by changing the amplitude and phase of the received signal a plurality of times within one symbol of the received signal while controlling so as to minimize the distortion component of the envelope of the received signal. Control process and
A signal division process that divides a plurality of output received signal patterns into a plurality of signals, and
An analysis process that identifies the combination of signals with the highest communication quality when demodulated by reducing the number of signals from all combinations of a plurality of divided signals.
A selection process that selects a part of multiple divided signals based on the analysis results,
A wireless communication method comprising a demodulation step of demodulating a selected signal in MIMO-OFDM. The analysis step is
Based on the calculation result of the signal power and interference power of the transmission signal or the calculation result of the packet error rate of the transmission signal, the combination of signals having the highest communication quality when demodulated by reducing the number of signals is specified. The wireless communication method according to claim 3, wherein the analysis is performed.

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