JP4245330B2 - Wireless transmission apparatus and wireless communication method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless transmission device and a wireless communication method used in a digital wireless communication system.
[0002]
[Prior art]
Currently, broadband wireless access systems are being developed with the aim of becoming a global standard. Furthermore, for the quasi-millimeter wave band, establishment of a next-generation mobile broadband wireless access scheme that utilizes abundant frequency resources is desired.
[0003]
As the current broadband wireless access system, under the world standard, 5 GHz band is used, the modulation system is frequency orthogonal multi-frequency (OFDM), and modulation for each subcarrier is performed depending on the quality of the propagation path. There is one in which the multi-value number is adaptively controlled. According to this method, the number of modulation multi-levels can be increased under conditions where the propagation path condition is good. For example, a transmission rate of 54 Mbps can be achieved using 64-value QAM in a frequency band of 20 MHz. .
[0004]
In recent years, in order to make more efficient use of frequencies, application of an SDM (Space Division Multiplex) scheme in which space division multiplexing is performed at the same frequency using a plurality of antennas has been studied (for example, see Non-Patent Document 1). . In this type of scheme, the modulation scheme is the same as in the prior art, but since different information is transmitted from a plurality of antennas at the same frequency and multiplexed in space, for example, when using two antennas, the frequency band to be used is The transmission capacity is doubled without increasing, and thus the transmission speed is also doubled.
[0005]
[Non-Patent Document 1]
Sugiyama, Umehira, “Proposal of Wideband PDM-COFDM System Using Orthogonal Polarization”, 2001 IEICE Communication Society, SB-3-7
[0006]
[Problems to be solved by the invention]
However, in the above-described conventional method, depending on the interference from other cells and the condition of the propagation path, in principle, the spatially multiplexed transmission signal may not be separated and reproduced on the receiving side, so that the communication capacity necessarily increases. However, there is a possibility that not only a situation in which an expected transmission speed requirement cannot be satisfied but also a situation in which communication is impossible may occur.
[0007]
The present invention has been made in view of this point, and an object of the present invention is to provide a wireless transmission device and a wireless communication method capable of further improving frequency use efficiency and transmission speed while maintaining communication quality. .
[0008]
[Means for Solving the Problems]
The radio transmission apparatus of the present invention includes a transmission unit that transmits the same or different information using a plurality of antennas, an interference wave detection unit that detects the presence or absence of an interference wave for each of a plurality of usable frequencies, and a propagation Propagation path status acquisition means for acquiring a path status, and each transmission frequency of the plurality of antennas is set to a non-interference frequency in which no interference wave detected by the interference wave detection means exists, and the propagation path status Control means for controlling the number of information transmitted from the plurality of antennas according to the propagation path condition acquired by the acquisition means, and the control means, when the propagation path condition is good, When the transmission frequencies of the plurality of antennas are set to the same non-interference frequency and different information is transmitted from the plurality of antennas, and the propagation path condition is poor, the plurality of antennas The transmission frequency is set to a different non-interference frequency and different information is transmitted from the plurality of antennas, or the transmission frequency of the plurality of antennas is set to the same non-interference frequency and the same from the plurality of antennas. Information is transmitted, or the transmission frequencies of the plurality of antennas are set to different non-interference frequencies, and the same information is transmitted from the plurality of antennas. If not, the transmission frequencies of the plurality of antennas are set to different non-interfering frequencies, and when different information is transmitted from the plurality of antennas, and the propagation path condition is extremely poor, the transmission frequencies of the plurality of antennas Are set to the same non-interference frequency and the same information is transmitted from the plurality of antennas, or each of the plurality of antennas is transmitted. Set incoherent different frequencies signal frequency, and employs a configuration to transmit the same information from the plurality of antennas.
[0009]
The wireless communication method of the present invention includes a transmission step of transmitting the same or different information using a plurality of antennas, an interference wave detection step of detecting presence or absence of an interference wave for each of a plurality of usable frequencies, and propagation A propagation path condition acquisition step for acquiring a road condition, and each transmission frequency of the plurality of antennas is set to a non-interference frequency in which there is no interference wave detected in the interference wave detection step, and the propagation path condition acquisition is performed A control step for controlling the number of pieces of information transmitted from the plurality of antennas according to the propagation path conditions acquired in the step, and in the control step, when the propagation path conditions are good, When the transmission frequencies of the antennas are set to the same non-interference frequency and different information is transmitted from the plurality of antennas, the propagation path condition is poor. Each transmission frequency of the plurality of antennas is set to a different non-interference frequency, and different information is transmitted from the plurality of antennas, or the transmission frequencies of the plurality of antennas are set to the same non-interference frequency, and The same information is transmitted from a plurality of antennas, or the transmission frequencies of the plurality of antennas are set to different non-interference frequencies, and the same information is transmitted from the plurality of antennas. If it is not very bad, the transmission frequencies of the plurality of antennas are set to different non-interfering frequencies, and different information is transmitted from the plurality of antennas. Set the transmission frequency of the antennas to the same non-interference frequency and transmit the same information from the plurality of antennas, or Set incoherent different frequencies each transmission frequency of the number of antennas, and were from the plurality of antennas so as to transmit the same information.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
The essence of the present invention is that when transmitting the same or different information using a plurality of antennas, the transmission frequency of the plurality of antennas and the number of pieces of information transmitted from the plurality of antennas are controlled according to the state of the propagation path. For example, different information is transmitted from multiple antennas at the same frequency (spatial multiplexing), different information is transmitted from multiple antennas at different frequencies (frequency multiplexing), and the same information is transmitted from multiple antennas at the same frequency. Or transmitting the same information from a plurality of antennas at different frequencies (frequency diversity) is adaptively switched according to the state of the propagation path.
[0031]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0032]
FIG. 1 is a block diagram showing a configuration of a radio transmission apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a radio reception apparatus that performs radio communication with the radio transmission apparatus shown in FIG. . The wireless transmission device shown in FIG. 1 and the wireless reception device shown in FIG. 2 can be mounted on the same wireless communication device.
[0033]
This wireless communication apparatus is, for example, an OFDM wireless communication apparatus. The wireless transmission apparatus 100 shown in FIG. 1 is an OFDM signal transmitter, and the wireless reception apparatus 200 shown in FIG. 2 receives an OFDM signal. Machine. The OFDM scheme is attracting attention as a next-generation mobile broadband radio access scheme because the influence of multipath delay spread in high-speed digital signal transmission can be reduced by multi-carrier and insertion of guard intervals. Here, the OFDM signal is obtained by multiplexing a plurality of orthogonal carrier wave (subcarrier) signals.
[0034]
In the present embodiment, in the OFDM scheme, when the same or different information is transmitted using a plurality of antennas, information transmitted from each transmission frequency of the plurality of antennas and the plurality of antennas according to the state of the propagation path By controlling the number of signals, frequency utilization efficiency and transmission speed are further improved while maintaining communication quality. Here, a case where the number of antennas is two will be described as an example.
[0035]
A wireless transmission device (transmitter) 100 illustrated in FIG. 1 includes a system 1 that transmits a transmission signal A and a system 2 that transmits a transmission signal B. The system 1 includes an encoding unit 101, a subcarrier modulation unit 102, an inverse fast Fourier transform (IFFT) unit 103, a slot assembly unit 104, a frequency conversion unit 105, and an antenna 106. The system 2 includes an encoding unit 111. , Subcarrier modulation section 112, inverse fast Fourier transform (IFFT) section 113, slot assembly section 114, frequency conversion section 115, and antenna 116. The transmitter 100 includes a carrier frequency control unit 121, a transmission signal switching unit 122, and an overall control unit 123.
[0036]
2 receives the transmission signal A from the transmitter 100 and obtains the reception signal A, and the transmission signal B from the transmitter 100. The radio reception apparatus (receiver) 200 shown in FIG. System 2 for obtaining the received signal B. However, when the transmission signal A and the transmission signal B have the same frequency, both the transmission signal A and the transmission signal B are received in each system. System 1 includes antenna 201, frequency conversion unit 202, fast Fourier transform (FFT) unit 203, subcarrier demodulation unit 204, and decoding unit 205, and system 2 includes antenna 211, frequency conversion unit 212, fast Fourier transform. A conversion (FFT) unit 213, a subcarrier demodulation unit 214, and a decoding unit 215 are included. The receiver 200 includes a carrier frequency control unit 221, a symbol synchronization timing unit 222, an interference compensation unit 223, an interference detection unit 224, and an error detection unit 225.
[0037]
When the transmitter 100 and the receiver 200 are mounted on the same wireless communication device, the antennas 106 and 116 for the transmitter 100 and the antennas 201 and 211 for the receiver 200 are of a transmission / reception shared type. There may be.
[0038]
Next, operations of the transmitter 100 and the receiver 200 having the above configuration will be described.
[0039]
First, the operation of the transmitter 100 is as follows.
[0040]
The transmission signal A of the system 1 is subjected to, for example, convolutional encoding by the encoding unit 101. The encoded signal is modulated for each subcarrier by subcarrier modulation section 102 and then output to IFFT section 103. In IFFT section 103, the output signal of subcarrier modulation section 102 is subjected to inverse fast Fourier transform (IFFT) to generate an OFDM signal. The generated OFDM signal is output to the frequency converter 105 after the guard interval and preamble are inserted by the slot assembler 104. The frequency conversion unit 105 up-converts the output signal of the slot assembly unit 104 to a radio frequency (transmission frequency) controlled independently by the carrier frequency control unit 121. The upconverted transmission signal is transmitted via the antenna 106. Further, the transmission signal B of the system 2 is processed in the same manner as the transmission signal A of the system 1, and the output signal of the slot assembly unit 114 is independently controlled by the carrier frequency control unit 121 in the frequency conversion unit 115. After being up-converted to the transmitted radio frequency (transmission frequency), it is transmitted from the antenna 116. At this time, transmission signal switching section 122 switches whether transmission signal A of system 1 and transmission signal B of system 2 are the same or not. Both carrier frequency control unit 121 and transmission signal switching unit 122 are adaptively controlled by control unit 123. The contents of the adaptive control by the control unit 123 will be described in detail later.
[0041]
Next, the operation of the receiver 200 is as follows.
[0042]
The OFDM signal received via the antenna 201 of the system 1 is a radio frequency independently controlled by the carrier frequency control unit 221 by the frequency conversion unit 202 (the same frequency as the transmission frequency of the antenna 106 that transmitted the transmission signal A). ) And then output to the FFT unit 203 through a guard interval removing unit (not shown). The FFT unit 203 uses the timing signal output from the symbol synchronization timing unit 222 to perform fast Fourier transform (FFT) on the OFDM signal after removal of the guard interval. The same processing is performed on the OFDM signal received via the antenna 211 of the system 2, and the radio frequency (the antenna that has transmitted the transmission signal B is independently controlled by the carrier frequency control unit 221 in the frequency conversion unit 212. 116), the guard interval is removed, and FFT processing is performed. The interference compensation unit 223 separates the spatially multiplexed signals by estimating the transfer function between the antennas 201 and 211. In the system 1 and the system 2, the separated signals are demodulated for each subcarrier by the subcarrier demodulation units 204 and 214, respectively, and then decoded by the decoding units 205 and 215. Thereby, the reception signal A and the reception signal B are obtained.
[0043]
At this time, the interference detection unit 224 detects a frequency that is not assigned to another user from a plurality of usable frequencies by measuring the interference level and detecting the presence or absence of an interference wave for each system. Further, the error detection unit 225 detects, for example, an error rate (for example, BER (Bit Error Rate)) as an index indicating the state of the propagation path. The interference detection result (presence / absence of interference wave in each system) by the interference detection unit 224 and the error detection result (error rate in each system) by the error detection unit 225 are the transmitters (see FIG. (Not shown) and a receiver (not shown) mounted on the wireless communication apparatus of the communication partner, the signal is given to the control unit 123 of the transmitter 100 of the communication partner.
[0044]
Next, the contents of the adaptive control in the transmitter 100 will be described in detail with reference to FIGS. Here, as an example, a case where there are four channels (frequency bands) from channel 1 (CH1) to channel 4 (CH4) as usable frequencies (more precisely, frequency bands) will be described. . 3 to 6, the antenna # 1 is the antenna 106 of the system 1, and the antenna # 2 is the antenna 116 of the system 2.
[0045]
In this embodiment, transmitter 100 can take four wireless communication schemes. The first is the case of spatial multiplexing, that is, the case where different information (transmission signal A ≠ transmission signal B) is transmitted from the two antennas 106 and 116 at the same frequency (for example, see FIG. 3), and the second In the case of frequency multiplexing, that is, when different information (transmission signal A ≠ transmission signal B) is transmitted from two antennas 106 and 116 at different frequencies (for example, see FIG. 4), the third is spatial diversity. In other words, the same information (transmission signal A = transmission signal B) is transmitted from the two antennas 106 and 116 at the same frequency (for example, see FIG. 5), and the fourth is the case of frequency diversity. That is, the same information (transmission signal A = transmission signal B) is transmitted from two antennas 106 and 116 at different frequencies (see, for example, FIG. 6). Based on the interference detection result (presence / absence of interference wave in each system) and error detection result (error rate in each system) from the receiver 200 mounted on the wireless communication device of the communication partner, the control unit 123 The four wireless communication systems are adaptively switched.
[0046]
Specifically, for example, when the error detection result is good, that is, when the propagation path condition is good, different information (transmission signal A ≠ transmission) from the two antennas 106 and 116 as shown in FIG. Spatial multiplexing is performed by transmitting the signal B) at the same frequency. In the example shown in FIG. 3, the antennas of the system 1 using CH1, CH2, and CH4 in which interference waves exist, that is, the vacant same channel (CH3) avoiding the frequencies (channels) allocated to other users. The transmission signals A and B that are different from the antenna 106 and the antenna 116 of the system 2 are multiplexed and transmitted. At this time, the receiver 200 performs a reception operation using the frequency used in the transmitter 100 (CH3 frequency in the example of FIG. 3).
[0047]
According to this method, when the propagation path condition is good, spatial multiplexing is performed, so that the frequency usage efficiency and transmission speed are further increased without increasing the frequency to be used, that is, while maintaining the frequency band to be used. The improvement can be maximized. In addition, a frequency where no interference wave is present is detected from a plurality (four in this case) of usable frequencies (CH1 to CH4), and a plurality of (two here) antennas are detected from the detected frequencies. Since each transmission frequency is set, the frequency utilization efficiency and the transmission speed can be further improved without being affected by interference from other users, that is, while maintaining communication quality.
[0048]
Further, for example, when the error detection result is bad, that is, when the propagation path condition is bad, as shown in FIG. 4, different information (transmission signal A ≠ transmission signal B) from the two antennas 106 and 116. Are transmitted at different frequencies to perform frequency multiplexing. In the example shown in FIG. 4, CH1 and CH4 in which interference waves exist, that is, frequencies (channels) assigned to other users are avoided, and among the two vacant channels CH2 and CH3, the antenna 106 of the system 1 Transmits the transmission signal A using one channel (CH2), and transmits the transmission signal B different from the system 1 from the antenna 116 of the system 2 using the other channel (CH3) different from the system 1. To do. At this time, the receiver 200 performs a receiving operation using the frequency of each system used in the transmitter 100 (in the example of FIG. 4, the system 1 is the CH2 frequency and the system 2 is the CH3 frequency).
[0049]
According to this method, frequency multiplexing is performed when the channel condition is poor, so that frequency utilization efficiency is maintained without being affected by communication quality degradation due to spatial multiplexing of each system, that is, while maintaining communication quality. Further improvement in transmission speed can be achieved. In addition, a frequency where no interference wave is present is detected from a plurality (four in this case) of usable frequencies (CH1 to CH4), and a plurality of (two here) antennas are detected from the detected frequencies. Since each transmission frequency is set, the frequency utilization efficiency and the transmission speed can be further improved without being affected by interference from other users, that is, while maintaining communication quality.
[0050]
Further, for example, when the error detection result is extremely bad, that is, when the propagation path condition is so bad that different information cannot be transmitted from a plurality of antennas, two cables are selectively used as shown in FIG. Space diversity by transmitting the same information (transmission signal A = transmission signal B) from the antennas 106 and 116 at the same frequency, or the same information from the two antennas 106 and 116 as shown in FIG. Frequency diversity is performed by transmitting (transmission signal A = transmission signal B) at different frequencies. In the example shown in FIG. 5, the antennas of the system 1 using CH1, CH2, and CH4 in which interference waves exist, that is, the vacant same channel (CH3) avoiding the frequencies (channels) allocated to other users. The same transmission signal (transmission signal A = transmission signal B) is transmitted from the antenna 106 of system 106 and the system 2 with space diversity. Moreover, in the example shown in FIG. 6, CH1 and CH4 in which interference waves exist, that is, avoiding the frequency (channel) assigned to other users, out of two vacant channels CH2 and CH3, The antenna 106 transmits a transmission signal using one channel (CH2), and the antenna 116 of the system 2 uses the other channel (CH3) different from the system 1 to transmit the same transmission signal (system 1). Transmit transmission signal A = transmission signal B). At this time, in the former case, the receiver 200 performs a reception operation using the frequency used in the transmitter 100 (in the example of FIG. 5, the frequency of CH3), and in the latter case, the receiver 200 uses the frequency. The reception operation is performed using the frequency of each system (in the example of FIG. 6, the system 1 is the CH2 frequency and the system 2 is the CH3 frequency).
[0051]
According to these methods, when the propagation path condition is extremely poor, that is, when it is necessary to ensure the communication quality even at the expense of the improvement of the transmission speed, the space diversity or the frequency diversity is performed. Even when the propagation path condition is so bad that different information cannot be transmitted from the antenna, the communication quality can be maintained by diversity.
[0052]
As described above, according to the present embodiment, when the same or different information is transmitted using the plurality of antennas 106 and 116, the transmission frequencies of the plurality of antennas 106 and 116 and The number of pieces of information transmitted from the plurality of antennas 106 and 116 is controlled. For example, spatial multiplexing, frequency multiplexing, spatial diversity, and frequency diversity are adaptively switched in accordance with propagation path conditions, so that communication quality is maintained. However, the frequency utilization efficiency and transmission speed can be further improved. In other words, it is possible to achieve both maintenance of communication quality and further improvement of frequency utilization efficiency and transmission speed.
[0053]
In the present embodiment, the adaptive control in transmitter 100 uses the same frequency even if there is a vacant frequency (to make it easier for other users to enter later), and this cannot ensure communication quality. In this case, it is based on the idea that different frequencies are used (however, it is necessary to detect the absence of interference waves), but the control idea of adaptive control is not limited to this.
[0054]
For example, it is possible to adopt a concept of transmitting at different frequencies when there is no interference wave, regardless of whether the propagation path condition is good or not. Specifically, for example, first, the presence / absence of an interference wave is detected, and when there is no interference wave, a different frequency is used. When the interference wave is detected during operation, the same frequency is used. After that, when it is detected that there is no interference wave, it is possible to use a different frequency again. In this case, regardless of the state of the propagation path, each transmission frequency of multiple antennas is set to a different frequency using a frequency that does not have an interference wave. And the influence of interference from other users can be reduced.
[0055]
In this embodiment, an OFDM wireless communication apparatus has been described as an example. However, the present invention is not limited to the case where the present invention is applied to the OFDM system. For example, the present invention is also applicable to a CDMA (Code Division Multiple Access) wireless communication apparatus.
[0056]
The radio transmission apparatus according to the present invention can be mounted on a radio communication apparatus in a mobile communication system, for example, a radio base station apparatus or a radio terminal apparatus.
[0057]
【The invention's effect】
As described above, according to the present invention, it is possible to further improve frequency utilization efficiency and transmission speed while maintaining communication quality.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a radio transmission apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of a radio reception apparatus that performs radio communication with the radio transmission apparatus shown in FIG. FIG. 4 is a diagram for explaining the case of spatial multiplexing among the radio communication systems that can be taken by the radio transmission apparatus shown in FIG. 1. FIG. 4 shows the case of frequency multiplexing among the radio communication systems that can be taken by the radio transmission apparatus shown in FIG. FIG. 5 is a diagram for explaining a case of spatial diversity among radio communication schemes that can be taken by the radio transmission apparatus shown in FIG. 1. FIG. 6 is a radio communication that can be taken by the radio transmission apparatus shown in FIG. Diagram for explaining frequency diversity among methods [Explanation of symbols]
100 Radio transmission devices 105, 115, 202, 212 Frequency conversion units 106, 116, 201, 211 Antennas 121, 221 Carrier frequency control unit 122 Transmission signal switching unit 123 Control unit 200 Radio reception device 223 Interference compensation unit 224 Interference detection unit 225 Error detector

Claims (4)

Transmission means for transmitting the same or different information using a plurality of antennas;
Interference wave detecting means for detecting the presence or absence of an interference wave for each of a plurality of usable frequencies;
A propagation path condition acquisition means for acquiring a propagation path condition;
Each transmission frequency of the plurality of antennas is set to a non-interference frequency where there is no interference wave detected by the interference wave detection means, and according to the propagation path situation acquired by the propagation path situation acquisition means, Control means for controlling the number of information transmitted from the plurality of antennas ,
The control means includes
If the propagation path condition is good,
Each transmission frequency of the plurality of antennas is set to the same non-interference frequency, and different information is transmitted from the plurality of antennas,
If the propagation path condition is bad,
Setting each transmission frequency of the plurality of antennas to a different non-interference frequency and transmitting different information from the plurality of antennas,
The transmission frequency of the plurality of antennas is set to the same non-interference frequency and the same information is transmitted from the plurality of antennas, or
Each transmission frequency of the plurality of antennas is set to a different non-interference frequency, and the same information is transmitted from the plurality of antennas,
If the propagation path condition is bad but not very bad,
Each transmission frequency of the plurality of antennas is set to a different non-interference frequency, and different information is transmitted from the plurality of antennas,
If the propagation path condition is extremely poor,
The transmission frequency of the plurality of antennas is set to the same non-interference frequency and the same information is transmitted from the plurality of antennas, or
Each transmission frequency of the plurality of antennas is set to a different non-interference frequency, and the same information is transmitted from the plurality of antennas.
A wireless transmitter characterized by the above. A radio base station apparatus comprising the radio transmission apparatus according to claim 1 . A wireless terminal device comprising the wireless transmission device according to claim 1 . A transmission step of transmitting the same or different information using a plurality of antennas;
An interference wave detection step for detecting the presence or absence of an interference wave for each of a plurality of usable frequencies;
A propagation path condition acquisition step for acquiring a propagation path condition;
Each transmission frequency of the plurality of antennas is set to a non-interference frequency in which there is no interference wave detected in the interference wave detection step, and the plurality of antennas are set according to the propagation path state acquired in the propagation path state acquisition step. has a control step of controlling the number of information transmitted from an antenna, a,
In the control step,
If the propagation path condition is good,
Each transmission frequency of the plurality of antennas is set to the same non-interference frequency, and different information is transmitted from the plurality of antennas,
If the propagation path condition is bad,
Setting each transmission frequency of the plurality of antennas to a different non-interference frequency and transmitting different information from the plurality of antennas,
The transmission frequency of the plurality of antennas is set to the same non-interference frequency and the same information is transmitted from the plurality of antennas, or
Each transmission frequency of the plurality of antennas is set to a different non-interference frequency, and the same information is transmitted from the plurality of antennas,
If the propagation path condition is bad but not very bad,
Each transmission frequency of the plurality of antennas is set to a different non-interference frequency, and different information is transmitted from the plurality of antennas,
If the propagation path condition is extremely poor,
The transmission frequency of the plurality of antennas is set to the same non-interference frequency and the same information is transmitted from the plurality of antennas, or
Each transmission frequency of the plurality of antennas is set to a different non-interference frequency, and the same information is transmitted from the plurality of antennas.
A wireless communication method.

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