JP2008206058A - Radio communication method and equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide highly reliable radio communication method and equipment which can quickly follow up variation in received field strength due to high-speed time fading, and can perform communication stably without lowering the communication speed of data even during high-speed movement of a mobile. <P>SOLUTION: In a received frame having a preamble region where a first known signal is arranged, and a following data region where a plurality of second known signals are arranged in the data region at least in the time base direction, the data region is grasped as a plurality of segments including the second known signal in the time base direction, and while sequentially updating the initial weighting factors calculated based on the first known signal in the preamble region in the sequential segments of the data region based on the second known signal included in that segment, the data signal in each segment is weighted again based on the second known signal included in that segment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless communication method and a wireless communication apparatus using a multi-antenna.

  As a wireless communication apparatus using a multi-antenna, for example, one having the configuration shown in FIGS. 4 and 5 is known. FIG. 4 shows a functional block diagram of the receiving unit, and FIG. 5 shows a functional block diagram of the transmitting unit. This wireless communication apparatus is installed as a base station, for example, has a plurality of antennas 101-1 to 101-k constituting a multi-antenna, and can transmit and receive by a TDD (Time Division Duplexing) method. Implementing OFDM (Orthogonal Frequency Division Multiplexing) using multiple carriers as a modulation method while performing antenna diversity, and realizing three-way SDMA (Spatial Division Multiple Access) It is.

  FIG. 6 shows an example of an OFDM frame configuration by the wireless communication apparatus shown in FIGS. This frame configuration is proposed as band AMC (Adaptive Modulation and Coding) in IEEE 802.16-2005, and includes an uplink subframe UL, a downlink subframe DL, and a guard time TTg provided therebetween. And have.

  The uplink subframe UL has a preamble area having a preamble Pre that is a first known signal corresponding to the terminal, and a data area that follows the preamble area. The data area includes a time axis direction and a frequency axis direction. A plurality of pilots Pt (subcarriers) are inserted as second known signals (known symbols) which are reference signals for establishing synchronization. Also, in the downlink subframe DL, a pilot Pt (subcarrier) of a known symbol that is a reference signal for establishing synchronization is inserted in the data area. FIG. 6 shows a case where one band is composed of two subchannels, and one subchannel is composed of two bins (Bin), and one bin is composed of nine subcarriers.

  In the reception unit shown in FIG. 4, signals received by antennas 101-1 to 101-k are input to reception mapping processing units 102-1 to 102-k for each antenna. The reception mapping processing units 102-1 to 102-k are configured in the same manner. As shown in FIG. 4, the CP removal unit 103, the S / P conversion unit, as representative of the configuration of the reception mapping processing unit 102-1. 104, an FFT 105, and a logical mapping unit 106.

  The received signal from the antenna 101-1 is removed from the cyclic prefix (CP) by the CP removal unit 103, and then is serially parallel (S / P) converted into a data sequence of the number of subcarriers by the S / P conversion unit 104. The After that, fast Fourier transform is performed by the FFT 105, the time domain signal is converted to a baseband signal for each subcarrier in the frequency domain, and the frequency mapping is performed by the logic mapping unit 106.

  The signal subjected to frequency mapping by the logical mapping unit 106 is supplied to the preamble extracting unit 107 and the synthesizing unit 108 together with signals from the reception mapping processing units 102-2 to 102-k corresponding to other antennas. , The preamble signal is extracted and supplied to the reception weight vector calculation unit 109, and the reception weight vector calculation unit 109 obtains the maximum reception gain for each terminal (for each band) based on the preamble signal. A reception weight vector (reception array weight) is calculated. Note that this reception weight vector is calculated according to the antenna diversity scheme using the antennas 101-1 to 101-k, for example, adaptive antenna system (AAS) or MIMO.

  Here, the reception weight vector can be obtained by the following equation (1) when expressed by W (m).

In the above equation (1), R _xx (m) represents an autocorrelation matrix in the preamble signal and can be calculated by the following equation (2). R _xr (m) represents a cross-correlation vector between the preamble signal and the reference signal, and can be calculated by the following equation (3).

  The reception weight vector for each terminal calculated by the reception weight vector calculation unit 109 is supplied to the transmission unit as a transmission weight vector and is also supplied to the synthesis unit 108, and the synthesis unit 108 receives the received signal of the corresponding terminal. Synthesized. The reception signal for each terminal, for which the reception weight vector is combined by the combining unit 108, is supplied to the decoding units 110-1 to 110-3 for each terminal.

  The decoding units 110-1 to 110-3 are configured in the same manner. As shown in FIG. 4, the P / S conversion unit 111, the demodulation unit 112, and the decoder 113 are configured to represent the configuration of the decoding unit 110-1. Have. The combined received signal from the combining unit 108 is parallel-serial (P / S) converted by the P / S conversion unit 111, demodulated by the demodulation unit 112, further decoded by the decoder 113, and output as reception data.

  In this way, the receiving unit suppresses fluctuations due to frequency selective fading with respect to the received signals from the antennas 101-1 to 101-k based on the preamble received signal in the uplink subframe UL, and is high. A reception process is performed to perform weighting so as to obtain a diversity gain.

  On the other hand, in the transmission unit shown in FIG. 5, transmission data for each terminal is encoded by the corresponding encoders 121-1 to 121-3, further modulated by the modulation units 122-1 to 122-3, and then transmitted. The transmission weight vectors supplied to the beam generation units 123-1 to 123-3 and calculated in the reception unit are combined here.

  The outputs of the transmission beam generating units 123-1 to 123-3 are combined for each antenna by the combining unit 124, and then supplied to the transmission mapping processing units 125-1 to 125-k for each antenna. The transmission mapping processing units 125-1 to 125-k are configured in the same manner. As shown in FIG. 5, the physical mapping unit 126, IFFT 127, P / S are representative of the configuration of the transmission mapping processing unit 125-1. A conversion unit 128 and a CP insertion unit 129 are included.

  The combined signal for each antenna combined by the combining unit 124 is mapped in subcarrier units by the physical mapping unit 126, and further subjected to inverse fast Fourier transform by the IFFT 127, so that the time domain signal corresponding to the number of subcarriers is obtained from the frequency domain signal. Then, the P / S conversion unit 128 performs parallel serial (P / S) conversion, and then the CP insertion unit 129 inserts a cyclic prefix (CP), and the corresponding antennas 101-1 to 101-101. k.

  In this way, the transmission unit weights transmission signals transmitted from the antennas 101-1 to 101-k in the next downlink subframe DL based on the transmission weight vector for each terminal calculated on the reception unit side. By doing so, the highest combined gain is obtained on the required terminal side.

  That is, in the conventional wireless communication apparatus described above, as schematically shown in FIG. 7, the reception weight vector calculated based on the preamble reception signal received in the uplink subframe UL is used as the data of the uplink subframe UL. By applying to the reception of the area and the transmission array weight of the data area of the downlink subframe DL, for example, as shown in FIG. 8, the directivity patterns by the antennas 101-1 to 101-k are multiplexed in three. In addition to performing adaptive beamforming that controls the direction of arrival of desired signals from the terminals UT0 to UT2, adaptive null steering is performed to control the null point of the directivity pattern in the direction of the disturbing wave. . FIG. 8 shows a directivity pattern in a horizontal plane, with the horizontal axis representing gain and the vertical axis representing distance in the 0 ° direction.

  The wireless communication apparatus shown in FIGS. 4 and 5 uses a plurality of subcarriers, and thus is effective for fluctuations in received electric field strength due to frequency selective fading, but the mobile body (terminal) moves at high speed. Because the tracking performance for multipath fluctuations, that is, temporal fading depends on the frame size, when temporal fading faster than the frame size occurs, it is not possible to follow the fluctuation of the received electric field strength. Reception quality will deteriorate.

As a wireless communication device that compensates for fluctuations in the received electric field strength due to temporal fading of the propagation path, for example, in communication of a data stream such as a packet, some weights calculated at the time of successful reception are stored. When retransmitting data with a reception error, select the weight that maximizes the antenna diversity gain at the time of retransmission from among the stored weights, and perform the retransmission process to reduce the received electric field strength due to temporal fading of the propagation path. A device that ensures the follow-up performance with respect to fluctuations is known (see, for example, Patent Document 1).
JP 2004-1112098 A

  However, the wireless communication device disclosed in Patent Document 1 compensates for variations in received electric field strength due to temporal fading using a weight calculated in the past during retransmission processing of a data stream in which a reception error has occurred. Therefore, it is not possible to quickly cope with temporal fading. For this reason, in particular, it is impossible to follow fluctuations caused by high-speed temporal fading caused by high-speed movement of a moving body, and as a result, retransmission processing is frequently performed, resulting in a decrease in communication speed. There is concern.

  Therefore, an object of the present invention made in view of such circumstances is to be able to quickly follow fluctuations in the received electric field strength due to high-speed temporal fading, and to reduce the data communication speed even when the mobile body is moving at high speed. An object of the present invention is to provide a wireless communication method and a wireless communication apparatus which are capable of stably communicating without fail and which are excellent in reliability.

The invention of a wireless communication method according to claim 1 that achieves the above object is a wireless communication method that has a plurality of antennas and performs wireless communication by a multicarrier system.
A preamble region in which a first known signal is arranged, and a data region that follows the preamble region, and a signal of a received frame in which a plurality of second known signals are arranged at least in the time axis direction in the data region, A receiving step for receiving via a plurality of antennas;
Grasping the data area as a plurality of divided areas each including the second known signal in the time axis direction;
An initial weighting factor calculating step for calculating an initial weighting factor for the data signal in the data region based on the first known signal in the preamble region;
The initial weighting factor is sequentially updated based on the second known signal included in the divided area in the sequential divided areas of the data area, and the data signal of each divided area is included in the divided area. A weighting step of weighting the updated weighting factor updated based on the second known signal;
It is characterized by including.

The invention according to claim 2 is the wireless communication method according to claim 1,
The wireless communication is a time division duplex method,
In transmission, the initial weighting factor calculated in the initial weighting factor calculating step is weighted to the transmission signal with respect to the immediately preceding received frame.

The invention according to claim 3 is the wireless communication method according to claim 1,
The wireless communication is a time division duplex method,
In transmission, the transmission signal is weighted with the last update weight coefficient sequentially updated in the weighting step with respect to the immediately preceding received frame.

Further, the invention of a wireless communication device according to claim 4 that achieves the above object is a wireless communication device that has a plurality of antennas and performs wireless communication by a multicarrier scheme.
A preamble region in which a first known signal is arranged, and a data region that follows the preamble region, and a signal of a received frame in which a plurality of second known signals are arranged at least in the time axis direction in the data region, Receiving means for receiving via a plurality of antennas;
Initial weight coefficient calculating means for calculating an initial weight coefficient for a data signal in the data area based on the first known signal in the preamble area;
The data area is grasped as a plurality of divided areas each including the second known signal in the time axis direction, and the initial weighting coefficient calculated by the initial weighting coefficient calculating means is used as the sequential divided areas of the data area. A weight coefficient updating means for sequentially updating based on the second known signal included in the divided area;
Weighting means for weighting the update weighting coefficient updated by the weighting coefficient updating means based on the second known signal included in the divisional area to the data signal of each divided area;
It is characterized by having.

  According to the present invention, the data area in the received frame is grasped as a plurality of divided areas including the second known signal in the time axis direction, and the initial weight coefficient calculated based on the first known signal in the preamble area is determined as the data area. Update sequentially based on the second known signal included in the divided area while updating the data signal of each divided area sequentially based on the second known signal included in the divided area. Since the weighting coefficient is weighted, it is possible to quickly follow fluctuations caused by high-speed temporal fading. Therefore, it is possible to realize a wireless transmission / reception method and a wireless transmission / reception apparatus that are communicable and have excellent reliability even when the mobile body is moving at high speed without reducing the data communication speed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a functional block diagram showing a configuration of a main part of a receiving unit of a wireless communication apparatus according to an embodiment of the present invention. The radio communication apparatus according to the present embodiment is installed as a base station, for example, similarly to the radio communication apparatuses shown in FIGS. 4 and 5 and includes a plurality of antennas 1-1 to 1-k constituting a multi-antenna. And implementing OFDM diversity system while implementing antenna diversity for both transmission and reception by TDD (Time Division Duplex) system to realize 3 multiplex SDMA. Note that the OFDM frame configuration is the Band AMC shown in FIG.

  In FIG. 1, signals received by antennas 1-1 to 1-k are supplied to reception mapping processing units 2-1 to 2-k for each antenna. The reception mapping processing units 2-1 to 2-k are configured in the same manner, and as shown in FIG. 1, the CP mapping unit 3 and the S / P conversion unit are representative of the configuration of the reception mapping processing unit 2-1. 4, an FFT 5 and a logic mapping unit 6.

  The received signal from the antenna 1-1 is removed from the cyclic prefix (CP) by the CP removal unit 3, and then is serially parallel (S / P) converted into a data sequence of the number of subcarriers by the S / P conversion unit 4. Thereafter, fast Fourier transform is performed by FFT 5 to convert the time domain signal into a baseband signal for each subcarrier in the frequency domain, and further, frequency mapping is performed by the logic mapping unit 6. Therefore, in the present embodiment, receiving means is configured by the antennas 1-1 to 1-k and the reception mapping processing units 2-1 to 2-k.

  The signal frequency-mapped by the logical mapping unit 6 is supplied to the preamble extraction unit 7 and the pilot extraction unit 8 together with the signals from the reception mapping processing units 2-2 to 2-k corresponding to other antennas, and is combined with the synthesis unit. 9 is supplied.

  The preamble extracting unit 7 extracts a preamble signal from the received signal and supplies the extracted preamble signal to the received weight vector calculating unit 10, and the received weight vector calculating unit 10 performs, based on the preamble signal, for each terminal (band) according to (1) described above. An initial reception weight vector (reception array weight) that obtains the maximum reception gain every time, that is, an initial weight coefficient is calculated. Therefore, in this embodiment, the preamble extraction unit 7 and the reception weight vector calculation unit 10 constitute an initial weight coefficient calculation unit. The reception weight vector is calculated according to an antenna diversity scheme using the antennas 1-1 to 1-k, for example, an adaptive antenna system (AAS) or MIMO (Multiple Input Multiple Output).

  The pilot extraction unit 8 extracts a pilot from the reception signal and supplies the pilot to the reception weight vector update unit 11, and the reception weight vector update unit 11 sequentially uses the initial reception weight vector calculated by the reception weight vector calculation unit 10. Update. Therefore, in this embodiment, the pilot extraction unit 8 and the reception weight vector update unit 11 constitute a weight coefficient update unit.

  The reception weight vector for each terminal updated by the reception weight vector update unit 11 is supplied to the synthesis unit 9 constituting the weighting means, and the synthesis unit 9 synthesizes the received signal of the corresponding terminal. The reception signal for each terminal, for which the reception weight vector is combined by the combining unit 9, is supplied to the decoding units 12-1 to 12-3 for each terminal. Also, the reception weight vector update unit 11 supplies the reception weight vector for each terminal updated last in the uplink subframe as a transmission weight vector (transmission array weight) to a transmission unit (not shown).

  The decoding units 12-1 to 12-3 are configured in the same manner. As shown in FIG. 1, the P / S conversion unit 13, the demodulation unit 14, and the decoder 15 are configured to represent the configuration of the decoding unit 12-1. Have. The combined received signal from the combining unit 9 is parallel-serial (P / S) converted by the P / S conversion unit 13, demodulated by the demodulation unit 14, further decoded by the decoder 15, and output as received data.

  In the present embodiment, the data area of the uplink subframe UL is divided into a plurality of data blocks in the time axis direction, as shown in FIG. FIG. 2 shows a case where the data is divided into four data blocks B1 to B4 for every three symbols that are the number of symbols in the time axis direction of one slot in Band AMC.

  In this way, when receiving the uplink subframe UL, first, the reception weight vector calculation unit 10 first receives the reception weight vector (reception array weight) based on the reception signal of the preamble Pre according to the above equation (1). Is calculated. Next, with respect to the first data block B1 in the data area, the reception weight vector updating unit 11 receives the received weight vector calculation unit 10 based on the received signal of the preamble Pre of the data block B1 extracted by the pilot extraction unit 8. The initial reception weight vector calculated in (1) is updated, and the updated reception weight vector is immediately applied to the reception signal in the data block B1 of the corresponding terminal in the combining unit 9 and combined.

  Similarly, for the next data block B2, the reception weight vector update unit 11 receives the reception data updated in the immediately preceding data block B1 based on the reception signal of the preamble Pre of the data block B2 extracted by the pilot extraction unit 8. The weight vector is further updated, and the updated reception weight vector is immediately applied to the received signal in the data block B2 of the corresponding terminal by the combining unit 9 and combined.

  As described above, in the uplink subframe UL, the initial weighting vector W (m) calculated based on the received signal of the preamble Pre by the reception weight vector calculating unit 10 is used as the sequential data blocks B1 to B1 in the data area. In B4, based on the reception signal of the pilot Pt extracted by the pilot extraction unit 8, the reception weight vector update unit 11 sequentially updates the received signal and the combining unit 9 immediately applies it to the reception signal of each data block.

  In the transmission of the downlink subframe DL, the reception weight updated by the reception weight vector update unit 11 using the reception signal of the pilot Pt in the last data block B4 of the data area in the immediately previous uplink subframe UL. The vector is output to the transmission unit as a transmission weight vector (transmission array weight).

  Although not shown, the transmission unit is configured in the same manner as in FIG. 1, and based on the transmission weight vector for each terminal calculated on the reception side, in the next downlink subframe DL, the antennas 1-1 to 1-1 are provided. By weighting the transmission signal transmitted from -k, the highest combined gain is obtained on the required terminal side.

Here, assuming that the reception weight vector (update weight coefficient) updated in each data block of the uplink subframe UL is W _B (n), W _B (n) is calculated by the following equation (4), for example. .

In the above formula (4), R _{xx, B} (n) can be calculated by the following formula (5), and r _{xr, B} (n) can be calculated by the following formula (6). Can do.

  Note that the data block of the data area in the uplink subframe UL for updating the reception weight vector may be arbitrarily set, an estimated value such as a Doppler shift amount, a speed of a mobile unit (terminal), or a delay. You may make it change automatically following the degree of a wave.

  The reception weight vector update process is preferably performed only when the terminal is moving at a predetermined speed or higher, for example, at a speed faster than the frame size. Note that the moving speed of the terminal can be calculated based on, for example, the phase difference between the upper and lower pilots on the frequency axis in the data area of the uplink subframe UL, or the phase difference between the pilots before and after the time axis.

  FIG. 3 is a flowchart showing the operation of the receiving unit shown in FIG. Since the flowchart shown in FIG. 3 overlaps with the above description, it will be briefly described here. In the reception operation, first, the cyclic prefix (CP) is removed from the received signal (step S1), and then the serial received signal is subjected to S / P conversion in parallel to a data sequence of the number of subcarriers (step S2). Thereafter, FFT (Fast Fourier Transform) processing is performed to convert the time domain signal into a baseband signal for each subcarrier in the frequency domain (step S3), and further frequency mapping (step S4). Next, a preamble signal is extracted from the received signal (step S5), and an initial reception weight vector is calculated (step S6).

  Thereafter, the presence / absence of a data block is determined (step S7). If there is a data block, a pilot is extracted from the data block (step S8), and the reception weight vector is updated (step S9). The reception weight vector is combined with the reception signal of the data block (step S10), and the process proceeds to step S7.

  If it is determined in step S7 that there is no data block, the weighting of the received data in the uplink subframe UL has been completed. Next, the parallel received signals combined with the received weight vectors are serially connected. P / S conversion (step S11), then demodulation (step S12) and decoding (step S13), and the reception process ends.

  Thus, in the present embodiment, the data area of the uplink subframe UL is divided into a plurality of data blocks in the time axis direction, and the initial reception weight vector calculated based on the reception signal of the preamble Pre is Since sequential data blocks are sequentially updated based on the received signal of pilot Pt and synthesized with the received signal of each data block, reception by temporal fading that is faster than the frame size while realizing SDMA. It is possible to quickly follow fluctuations in the electric field intensity and perform stable wireless communication that can maintain high-speed data transfer even when the mobile body (terminal) moves at high speed.

  In addition, this invention is not limited only to the said embodiment, Many deformation | transformation or a change is possible. For example, in the above embodiment, the reception weight vector updated using the received signal of pilot Pt in the last data block of the uplink subframe UL is used as the transmission weight vector (transmission array weight) in the next downlink subframe DL. However, as this transmission weight vector, an initial reception weight vector calculated based on the reception signal of the preamble Pre of the uplink subframe UL can also be applied.

  Further, the present invention can be applied not only when SDMA is not performed, but also effectively when not only the Band AMC frame configuration but also other frame configurations such as FUSC. Furthermore, the duplex system is not limited to the TDD system, but can be applied to an FDD (frequency division duplex) system.

It is a functional block diagram which shows the structure of the principal part of the receiving part of the radio | wireless communication apparatus which concerns on one embodiment of this invention. It is a figure which shows typically the weighting operation | movement by the radio | wireless communication apparatus shown in FIG. 3 is a flowchart illustrating an operation of a receiving unit illustrated in FIG. 1. It is a functional block diagram which shows the structure of the principal part of the receiving part of the conventional radio | wireless communication apparatus. It is a functional block diagram which shows the structure of the principal part of the transmission part of the conventional radio | wireless communication apparatus. FIG. 6 is a diagram illustrating an example of an OFDM frame configuration by the wireless communication device illustrated in FIGS. 4 and 5. It is a figure which shows typically the weighting operation | movement by the conventional radio | wireless communication apparatus. It is a figure which shows the example of control of the directivity pattern of the antenna by the conventional radio | wireless communication apparatus.

Explanation of symbols

1-1 to 1-k antenna 2-1 to 2-k reception mapping processing unit 3 CP removal unit 4 S / P conversion unit 5 FFT
DESCRIPTION OF SYMBOLS 6 Logical mapping part 7 Preamble extraction part 8 Pilot extraction part 9 Synthesis | combination part 10 Reception weight vector calculation part 11 Reception weight vector update part 12-1 to 12-3 Decoding part 13 P / S conversion part 14 Demodulation part 15 Decoder

Claims (4)

In a wireless communication method having a plurality of antennas and performing wireless communication by a multicarrier method,
A preamble region in which a first known signal is arranged, and a data region that follows the preamble region, and a signal of a received frame in which a plurality of second known signals are arranged at least in the time axis direction in the data region, A receiving step for receiving via a plurality of antennas;
Grasping the data area as a plurality of divided areas each including the second known signal in the time axis direction;
An initial weighting factor calculating step for calculating an initial weighting factor for the data signal in the data region based on the first known signal in the preamble region;
The initial weighting factor is sequentially updated based on the second known signal included in the divided area in the sequential divided areas of the data area, and the data signal of each divided area is included in the divided area. A weighting step of weighting the updated weighting factor updated based on the second known signal;
A wireless communication method comprising: The wireless communication is a time division duplex method,
2. The wireless communication method according to claim 1, wherein, in transmission, the initial weighting factor calculated in the initial weighting factor calculating step is weighted to the transmission signal for the immediately preceding received frame. The wireless communication is a time division duplex method,
2. The wireless communication method according to claim 1, wherein, in transmission, the transmission signal is weighted with the last update weight coefficient sequentially updated in the weighting step with respect to the immediately preceding received frame. In a wireless communication apparatus having a plurality of antennas and performing wireless communication by a multicarrier system,
A preamble region in which a first known signal is arranged, and a data region that follows the preamble region, and a signal of a received frame in which a plurality of second known signals are arranged at least in the time axis direction in the data region, Receiving means for receiving via a plurality of antennas;
Initial weight coefficient calculating means for calculating an initial weight coefficient for a data signal in the data area based on the first known signal in the preamble area;
The data area is grasped as a plurality of divided areas each including the second known signal in the time axis direction, and the initial weighting coefficient calculated by the initial weighting coefficient calculating means is used as the sequential divided areas of the data area. A weight coefficient updating means for sequentially updating based on the second known signal included in the divided area;
Weighting means for weighting the update weighting coefficient updated by the weighting coefficient updating means based on the second known signal included in the divisional area to the data signal of each divided area;
A wireless communication apparatus comprising:

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