JP2010154417A - Wireless communication system, wireless communication method, and wireless transmitting and receiving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication system, a wireless communication method and a wireless transmitting and receiving apparatus in which reduction in communication quality can be suppressed when a subcarrier is subjected to an interference. <P>SOLUTION: There are provided an estimation section (an interfered subcarrier detection section 9) for estimating the propagation path status of each sub channel based on received data, and a selection section (a channel control section 10) for selecting a sub channel to be used among a plurality of sub channels based on the estimated propagation path status of each sub channel so that the information of the selected sub channel is transmitted to an opponent station. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radio communication system, a radio communication method, and a radio transmission / reception device, and in particular, a given frequency band is divided into a plurality of subchannels on the frequency axis, and a plurality of orthogonal channels assigned to each subchannel are orthogonal to each other. The present invention relates to a wireless communication system, a wireless communication method, and a wireless transmission / reception apparatus that perform wireless communication by assigning transmission data to subcarriers.

  In a wireless communication system using OFDM, a frequency band given to the system is divided into a plurality of narrow sub-channels (frequency bands), and transmission data is assigned to sub-carriers (sub-carriers) assigned to each sub-channel. To communicate.

Japanese Patent Laid-Open No. 2001-24616

In OFDM, since transmission data is distributed to a plurality of subcarriers and transmitted, it is possible to reduce the probability of losing transmission data due to multipath frequency selective fading. However, when interference waves are continuously generated in the subchannel, the subcarriers that have been disturbed cannot continuously contribute to data transmission, resulting in a problem that communication quality is deteriorated.

  The present invention has been made in view of such a conventional situation, and provides a wireless communication system, a wireless communication method, and a wireless transmission / reception apparatus that suppress a decrease in communication quality when a subcarrier is disturbed. The purpose is to provide.

  In order to achieve the above object, in the wireless communication system according to the present invention, a given frequency band is divided into a plurality of subchannels on the frequency axis, and a plurality of sub-channels assigned to each subchannel are orthogonal to each other. In a wireless communication system that performs wireless communication by assigning transmission data to a carrier, an estimation unit that estimates a propagation path state of each subchannel based on received data, and according to the estimated propagation path state of each subchannel A selection unit that selects a subchannel to be used from among the plurality of subchannels, and transmits information on the selected subchannel to a partner station.

  Here, the estimation unit estimates an amplitude phase error of a symbol point of data assigned to the subcarrier, and the selection unit determines whether there is an interference wave for each subcarrier based on the estimated amplitude phase error. It is preferable to select a subchannel that is determined not to have an interference wave as a subchannel to be used for transmitting effective data.

  In the radio communication method according to the present invention, a given frequency band is divided into a plurality of subchannels on the frequency axis, and transmission data is transmitted to a plurality of subcarriers orthogonal to each other assigned to each subchannel. In a wireless communication method for performing wireless communication by assigning, a propagation path condition of each subchannel is estimated based on received data, and a plurality of subchannels are selected according to the estimated propagation path condition of each subchannel. A subchannel to be used is selected, and information on the selected subchannel is transmitted to a partner station.

  In the radio transmission / reception apparatus according to the present invention, a given frequency band is divided into a plurality of subchannels on the frequency axis, and transmission data is transmitted to a plurality of subcarriers orthogonal to each other assigned to each subchannel. In a wireless transmission / reception apparatus that performs wireless communication by allocating, a data division unit that divides the transmission data according to a data amount corresponding to the usage status of the subchannel, and symbolizes the divided transmission data, A mapping unit that maps on the signal point arrangement and allocates subcarriers, a pilot allocation unit that allocates pilot symbols to subcarriers at regular intervals on the frequency axis, and a symbol point for each subcarrier allocated to the received subchannel The amplitude phase error of each subkey is calculated based on the amplitude phase error. An interference wave determination unit that determines presence / absence of an interference wave with respect to the rear, and a selection unit that selects a subchannel to be used so that the data symbol and the pilot symbol are not allocated to a subcarrier determined to have an interference wave; And transmitting information on the selected subchannel to the partner station, and further, when receiving the subchannel information transmitted from the partner station, the subchannel being used based on the subchannel information. And a demapping unit for performing carrier demapping.

  In the wireless communication system, the wireless communication method, and the wireless transmission / reception apparatus according to the present invention, the communication quality when the subcarrier is disturbed is selected by selecting the subchannel to be used according to the state of the subchannel. The decrease can be suppressed.

  Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing a configuration example of a radio transmission / reception apparatus constituting the radio communication system of the present invention. 2 is a diagram showing an example of the configuration of a frame used in the apparatus shown in FIG. 1, and FIG. 3 is a diagram showing an example of an OFDM symbol used in the apparatus shown in FIG. FIG. 4 is a diagram showing an example of symbol arrangement on the frequency axis-time axis executed by the apparatus shown in FIG.

  As shown in FIG. 1, the radio transmission / reception apparatus 1 includes a data division unit 2, a subcarrier mapping unit 3, a pilot insertion unit 4, a channel allocation unit 5, an IFFT (Inverse Fast Fourier Transform) unit 6, and a GI. A (Guard interval) insertion unit 7, an RF (radio) unit 8, an interference subcarrier detection unit 9, and a channel control unit 10 are provided.

  Digital data (transmission data) input to the data dividing unit 2 is divided into data corresponding to the number of subchannels to be used. The output of the data dividing unit 2 is input to the subcarrier mapping unit 3. The subcarrier mapping unit 3 performs mapping processing of transmission symbols assigned to the subcarriers according to the number of subcarriers to be used. Also, the pilot insertion unit 4 inserts pilot symbols (known symbols on both the transmission side and the reception side) at regular intervals in the frequency direction as shown in FIG. This pilot symbol is used to estimate the channel distortion in the frequency direction and time direction of data symbols arranged between pilot symbols.

  The outputs of the subcarrier mapping unit 3 and the pilot insertion unit 4 are input to the channel arrangement unit 5, respectively. The channel arrangement unit 5 arranges pilot symbols and subcarrier mapped data symbols according to the arrangement of subchannels to be used (arranged in the frequency direction). Here, the subchannel to be used is selected (determined) by the channel control unit 10 based on the disturbing subcarrier detected by the disturbing subcarrier detection unit 9, and the information is the data dividing unit 2, the subcarrier mapping unit 3, It is sent to the pilot insertion unit 4 and the channel placement unit 5. Further, as shown in FIG. 2, the selected subcarrier information is arranged in the transmission frame together with the transmission data. The selection of the subcarrier to be used will be described in detail later.

  The channel placement unit 5 forms null subchannels by placing zeros in unused subchannels. That is, data that is effective as transmission data is allocated to subcarriers to be used, and null data is allocated to subcarriers that are not used.

  The output of the channel arrangement unit 5 is input to the IFFT unit 6. The IFFT unit 6 converts transmission symbols arranged in the frequency direction into time domain signals, and generates transmission OFDM symbols having a certain time length. The output of the IFFT unit 6 is further input to the GI insertion unit 7. As shown in FIG. 3, the GI insertion unit 7 copies a certain length from the latter half of the OFDM symbol and arranges it at the head of the OFDM symbol as a guard interval. For this guard interval length, for example, 1/4 or 1/8 of an OFDM symbol is used in consideration of propagation delay. The OFDM symbol in which the guard interval is inserted is converted into a high-frequency signal by the RF unit 8 and transmitted from the antenna 11 to the wireless transmission path.

  The radio transmission / reception unit 1 further includes a synchronization unit 12, a GI (Guard interval) removal unit 13, an FFT (Fast Fourier Transform) unit 14, a channel separation unit 15, a propagation path compensation unit 16, and a propagation path estimation unit. 17 and a subcarrier demapping unit 18.

  The high frequency signal transmitted from the counterpart station is received by the antenna 11, and the baseband OFDM symbol is generated by the RF unit 8. The baseband OFDM symbol is input to the synchronization unit 12. The synchronization unit 12 performs correlation processing between the guard interval inserted at the head of the baseband OFDM symbol and the effective OFDM symbol (OFDM symbol of valid data), and detects the head of the effective OFDM symbol.

  The GI removal unit 13 removes the guard interval by cutting out an effective OFDM symbol from the head detected by the synchronization unit 12. The effective OFDM symbol from which the guard interval is removed is input to the FFT unit 14, converted from a time domain signal to a frequency domain signal, and further divided into subchannels. The channel separation unit 15 separates the subchannel divided by the FFT unit 14 into data symbols and pilot symbols. At this time, the channel separation unit 15 also extracts subcarrier information included in the transmission data.

  The output of the channel separation unit 15 is input to the propagation path compensation unit 16 and the propagation path estimation unit 17. The propagation path estimation unit 17 estimates the distortion generated in the propagation path in the frequency axis direction and the time axis direction from the inserted pilot symbols, and estimates the amplitude phase error (EVM) in both the pilot symbols and the data symbols. (measure. The propagation path compensation unit 16 removes the transmission path distortion of the data symbol by superimposing the inverse characteristic of the propagation path distortion estimated by the propagation path estimation unit 17 on the data symbol.

  The jamming subcarrier detector 9 detects the jamming subcarrier based on the channel status estimated by the channel estimator 17, that is, the EVM. As shown in FIG. 4, since the normal interference wave is continuously generated for a specific frequency, the interference wave has an average of EVM estimated by the propagation path estimation unit 17 and a threshold value for determining interference / non-interference. This can be determined by comparison.

For example, when the interference wave detection time (number of symbols) is 5 symbols and the interference received by the subcarrier number 7 in FIG. 4 is detected, it can be expressed by the following equation (1).
(EVM _{f7 # 0} + EVM _{f7 # 1} + EVM _{f7 # 2} + EVM _{f7 # 3} + EVM _{f7 # 4} ) / 5 <Threshold ・ ・ ・ (1)

Here, EVM _{fm # n} indicates the EVM value in the subcarrier number m-th and OFDM symbol number _{# n-} th subcarrier. Threshold is a threshold that is optimally set in the radio propagation environment in the target radio transmission system. In the above equation (1), only the subcarrier number 7 is calculated, but in reality, the same calculation as described above is performed for the detection of jamming waves for all subcarrier numbers used for radio transmission.

  The channel control unit 10 selects a subchannel to be used based on the presence / absence of the interference wave determined as described above by the interference subcarrier detection unit 9. Specifically, the subchannel determined to have no interference wave is selected as a subchannel to be used, and the subchannel determined to have interference wave is a null subchannel. Information on the subchannel selected by the channel control unit 10 in this way is sent to the data division unit 2, subcarrier mapping unit 3, pilot insertion unit 4, and channel allocation unit 5.

  Further, the subcarrier information extracted by the channel separation unit 15 is sent to the subcarrier demapping unit 18. The subcarrier demapping unit 18 receives the output of the propagation path compensation unit 16, performs demapping processing based on the subcarrier information, and obtains digital data.

  As described above, in the wireless communication system according to the present invention, the estimation unit (disturbance subcarrier detection unit 9) that estimates the propagation path condition of each subchannel based on the received data, and the estimated each A selection unit (channel control unit 10) that selects a subchannel to be used from among a plurality of subchannels based on a propagation path condition of the subchannel, and transmits information on the selected subchannel to the partner station Thus, wireless communication can be performed using only the selected subchannel, and deterioration in communication quality when the subcarrier is disturbed can be suppressed.

  Further, the estimation unit estimates an amplitude phase error of a symbol point of data allocated to the subcarrier, and the selection unit determines whether there is an interference wave for each subcarrier based on the estimated amplitude phase error. Since it is configured to select the subchannel determined to have no interference wave as the subchannel to be used for transmitting effective data, it is possible to accurately determine the presence or absence of the interference wave with a simple configuration.

  Further, in the wireless communication method according to the present invention, the propagation path condition of each subchannel is estimated based on the received data, and a plurality of subchannels are determined according to the estimated propagation path condition of each subchannel. Since the sub-channel to be used is selected and the information on the selected sub-channel is transmitted to the other station, wireless communication can be performed using only the selected sub-channel. It is possible to suppress deterioration in communication quality when the carrier is disturbed.

  Further, in the radio transmission / reception apparatus according to the present invention, the data division unit (2) that divides the transmission data according to the data amount corresponding to the usage status of the subchannel, and symbolizes the divided transmission data, A mapping unit (subcarrier mapping unit 3) that maps the data symbols on the signal point allocation and allocates subcarriers, and a pilot allocation unit (pilot insertion unit 3) that allocates pilot symbols to subcarriers at regular intervals on the frequency axis For each subcarrier assigned to the received subchannel, an interference phase determination unit (interference subcarrier) that determines an amplitude phase error at a symbol point and determines the presence or absence of an interference wave for each subcarrier based on the amplitude phase error. Detecting unit 9) and the data symbol in the subcarrier determined to have an interfering wave. A selection unit (channel control unit 10) that selects a subchannel to be used so that the pilot symbols are not allocated, and transmits information on the selected subchannel to the counterpart station and further transmits from the counterpart station When the received subchannel information is received, based on the subchannel information, a demapping unit (subcarrier demapping unit 18) that performs demapping of the used subcarrier is provided. Thus, it is possible to perform radio communication using only the selected subchannel, and it is possible to suppress a decrease in communication quality when the subcarrier is disturbed.

It is a block diagram which shows one structural example of the radio | wireless transmission / reception apparatus which comprises the radio | wireless communications system of this invention. It is a figure which shows the structural example of the flame | frame used with the apparatus shown in FIG. It is a figure which shows an example of the OFDM symbol used with the apparatus shown in FIG. It is a figure which shows an example of the symbol arrangement | positioning on the frequency axis-time axis performed with the apparatus shown in FIG.

Explanation of symbols

1: wireless transceiver, 2: data division unit, 3: subcarrier mapping unit, 4: pilot insertion unit, 5: channel allocation unit, 6: IFFT unit, 7: GI insertion unit, 8: RF unit, 9: interference Subcarrier detection section, 10: channel control section, 12: synchronization section, 13: GI removal section, 14: FFT section, 15: channel separation section, 16: propagation path compensation section, 17: propagation path estimation section, 18: sub Carrier demapping part

Claims (4)

In a wireless communication system that divides a given frequency band into a plurality of subchannels on the frequency axis and performs transmission by assigning transmission data to a plurality of subcarriers that are orthogonal to each other assigned to each subchannel.
An estimation unit that estimates the propagation path condition of each subchannel based on the received data;
A selection unit that selects a subchannel to be used from among the plurality of subchannels based on the estimated propagation path condition of each subchannel;
A wireless communication system comprising: transmitting information on the selected subchannel to a partner station. The estimation unit estimates an amplitude phase error of a symbol point of data allocated to the subcarrier;
The selection unit determines the presence / absence of an interfering wave for each subcarrier based on the estimated amplitude phase error, and selects a subchannel determined to have no interfering wave as a subchannel to be used for transmission of effective data.
The wireless communication system according to claim 1. In a wireless communication method for performing wireless communication by dividing a given frequency band into a plurality of subchannels on the frequency axis, and assigning transmission data to a plurality of subcarriers assigned to each subchannel and orthogonal to each other,
Estimate the channel conditions of each subchannel based on the received data,
Selecting a subchannel to be used from among the plurality of subchannels according to the estimated propagation path condition of each subchannel;
Transmitting information of the selected subchannel to the partner station;
A wireless communication method characterized by the above. In a radio transmission / reception apparatus that divides a given frequency band into a plurality of subchannels on the frequency axis and performs transmission by assigning transmission data to a plurality of subcarriers that are orthogonal to each other assigned to each subchannel,
A data dividing unit that divides the transmission data according to a data amount corresponding to the usage status of the subchannel;
A mapping unit that converts the divided transmission data into symbols, maps the data symbols on a signal point arrangement, and assigns subcarriers;
A pilot allocation unit that allocates pilot symbols to subcarriers at regular intervals on the frequency axis;
For each subcarrier assigned to the received subchannel, an interference phase determination unit that determines an amplitude phase error at a symbol point and determines the presence or absence of an interference wave for each subcarrier based on the amplitude phase error;
A selection unit that selects a subchannel to be used so that the data symbol and the pilot symbol are not allocated to a subcarrier determined to have an interference wave;
And transmitting information on the selected subchannel to the partner station, and
A demapping unit that performs demapping of subcarriers used when receiving information on the subchannel transmitted from the counterpart station, based on the information on the subchannel;
A wireless transmission / reception apparatus comprising: