JP3746029B2 - Wireless communication apparatus and wireless communication method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio communication apparatus and a radio communication method, and more particularly to a radio communication apparatus and a radio communication method suitable for use in OFDM communication.
[0002]
[Prior art]
In wireless communication, there is a diversity technique as a technique for positively improving error rate characteristics. The diversity technique is a technique for improving error rate characteristics by combining a plurality of received signals including the same information.
[0003]
One of the diversity techniques is transmission diversity. In transmission diversity, signals are transmitted from two antennas (branches) having a low fading correlation to the same communication partner, so that high-quality reception can be achieved by a tie diversity effect without making the receiving apparatus complex. it can.
[0004]
In a transmission diversity system using a plurality of transmission antennas (for example, STTD-Space Time Transmit Diversity), if the fading correlation between branches is high, the diversity gain is reduced and the effect cannot be sufficiently obtained. In particular, regarding the mobile device, considering the size of the housing, it is highly likely that it is difficult to dispose a plurality of antennas with a sufficiently wide interval, and the above problem becomes significant. Also, in the H-ARQ system that resends the same packet and combines with the already received packet when an error in the packet is detected on the receiving side, when the retransmission interval is short or the maximum Doppler frequency is low, the time direction , And the diversity gain at the time of packet combining cannot be sufficiently obtained.
[0005]
In a conventional wireless communication apparatus, when transmitting a plurality of bursts in time, a multi-carrier modulation method is adopted, and interleaving is performed for each burst so that a time interval is longer than necessary in a low-speed fading transmission path environment and a high transmission speed environment. Some have the same effect as when the time interval is released without being released. (For example, refer to Patent Document 1).
[0006]
However, in the above example, in order to change the interleave pattern without distinguishing whether or not the data is correctly received, even when the data rearranged in the interleave pattern suitable for the transmission path environment is transmitted, the data to be transmitted next is Since rearrangement is performed using different interleaving patterns, there is a possibility that the interleaving effect may not be sufficiently obtained.
[0007]
[Patent Document 1]
JP 2000-269929 A
[Problems to be solved by the invention]
As described above, in the conventional apparatus, the diversity gain decreases and reception error decreases due to reasons such as a high correlation between branches, a short retransmission interval, a low maximum Doppler frequency, and a high fading correlation in the time direction. Occurs and sufficient throughput cannot be obtained.
[0009]
The present invention has been made in view of this point, and provides a wireless communication apparatus and a wireless communication method capable of improving throughput characteristics by simultaneously increasing diversity gains during transmission and packet combining in multicarrier communication such as OFDM. Objective.
[0010]
[Means for Solving the Problems]
A radio communication apparatus of the present invention is a radio communication apparatus that transmits data from a plurality of different antennas, a transmission diversity encoder and a mapper that form a space-time block code symbol from transmission data, and a space-time block code symbol. An interleaving unit that interleaves in the frequency axis direction for each retransmission, and an orthogonal transform unit that superimposes interleaved transmission symbols on a plurality of subcarriers, and the interleaving unit performs the previous processing for symbols in the same space-time block. A configuration is adopted in which symbol sequences arranged on the first subcarrier at the time of transmission are collectively arranged on the second subcarrier different from the first subcarrier in the same order as at the previous transmission .
[0026]
A base station apparatus according to the present invention employs a configuration including the wireless communication apparatus. A communication terminal apparatus according to the present invention employs a configuration including the wireless communication apparatus.
[0028]
The radio communication method of the present invention is a radio communication method for transmitting multicarrier signals from a plurality of antennas, respectively, a step of forming a space-time block code symbol from transmission data, and a frequency of the space-time block code symbol for each retransmission. An interleaving step of interleaving in the axial direction and a step of superimposing the interleaved transmission symbols on a plurality of subcarriers. In the interleaving step, symbols in the same space-time block are transferred to the first subcarrier at the previous transmission. The arranged symbol strings are collectively arranged on the second subcarrier different from the first subcarrier in the same order as in the previous transmission.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
In the case where an error occurs in received data, the present inventor cannot increase the transmission diversity effect even if transmission is performed on the same subcarrier, whereas the correlation in transmission diversity differs for each subcarrier. It came to invent, paying attention to the point.
[0031]
That is, the gist of the present invention is to reduce correlation between branches by changing and retransmitting a subcarrier for transmitting data when an error occurs in received data in multicarrier communication to which transmission diversity is applied. The opportunity is to increase diversity gain and improve throughput.
[0032]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a radio communication apparatus according to Embodiment 1 of the present invention. 1 includes a wireless reception unit 101, a counter 102, an encoder 103, a storage unit 104, a modulator 105, a transmission diversity encoder 106-1, and a transmission diversity encoder 106-2. Mapping controller 107, mapping unit 108-1, mapping unit 108-2, interleaver controller 109, interleaving unit 110-1, interleaving unit 110-2, IFFT unit 111-1, and IFFT unit 11-2, a wireless transmission unit 112-1, and a wireless transmission unit 112-2.
[0033]
In FIG. 1, a radio reception unit 101 converts a received radio signal into a baseband frequency and demodulates it, takes out an ACK signal or a NACK signal, and outputs it to the counter 102. Here, the ACK signal is a signal indicating that the transmitted signal has been correctly received, and the NACK signal is a signal indicating that the transmitted signal has not been correctly received. The counter 102 measures the number of times the NACK signal has been received in units of data to be transmitted, and outputs this number to the storage unit 104, the mapping controller 107, and the interleaver controller 109.
[0034]
The encoder 103 performs error correction encoding on the data to be transmitted and outputs the data to the storage unit 104. The storage unit 104 stores the encoded data. When a counter value (for example, “1”) indicating initial transmission is received from the counter 102, the storage unit 104 outputs the next encoded data to the modulator 105. Further, when a counter value indicating retransmission (for example, other than “1”) is received from the counter 102, the storage unit 104 outputs the previously stored data to the modulator 105 again.
[0035]
Modulator 105 modulates the data and outputs the data to transmission diversity encoder 106-1 and transmission diversity encoder 106-2. Transmission diversity encoder 106-1 outputs the input data series as it is to mapper 108-1. The transmission diversity encoder 106-2 takes the complex conjugate of the data, rearranges the order of two adjacent symbols, performs x (-1) operation on one symbol, and outputs the result to the mapper 108-2.
[0036]
The mapping controller 107 determines a subcarrier to which data is mapped based on the number of times the NACK signal is received in units of data to be transmitted, and instructs the mapping unit 108-1 and the mapping unit 108-2. The subcarrier indicated by the mapping controller 107 differs depending on the number of times the NACK signal is received.
[0037]
The mapping unit 108-1 maps the phase and amplitude of the transmitted data with the subcarriers indicated by the mapping controller 107 and outputs the mapped data to the interleaving unit 110-1. Similarly, mapper 108-2 maps the phase and amplitude of the data to be transmitted with the subcarriers indicated by mapping controller 107, and outputs the result to interleaving section 110-2.
[0038]
Interleaver controller 109 instructs interleaving section 110-1 and interleaving section 110-2 based on the number of times the NACK signal is received in units of data to be transmitted. The interleave pattern instructed by the interleaver controller 109 differs depending on the number of times the NACK signal is received.
[0039]
The interleaving unit 110-1 includes a selection circuit 121 and interleavers 122-1 to 122-n, and rearranges data by changing the interleave pattern in accordance with instructions from the interleaver controller 109. Then, interleaving section 110-1 outputs the rearranged data to IFFT section 111-1.
[0040]
The selection circuit 121 outputs data to an interleaver that rearranges the interleaver according to the instruction of the interleaver controller 109 among the interleavers 122-1 to 122-n. The interleavers 122-1 to 122-n rearrange the data order with different interleave patterns, and output the rearranged data to the IFFT unit 111-1.
[0041]
For example, at the first transmission, the selection circuit 121 outputs data to the interleaver 122-1, and at the first retransmission, the selection circuit 121 outputs data to the interleaver 122-2, at the second retransmission, The selection circuit 121 outputs data to the interleaver 122-3. When the data transmission is successful and the next data is transmitted, the selection circuit 121 outputs the data to the interleaver 122-1 again.
[0042]
Similarly, interleaving section 110-2 rearranges data by changing the interleave pattern in accordance with the instruction from interleaver controller 109. Then, interleaving section 110-2 outputs the rearranged data to IFFT section 111-2.
[0043]
IFFT section 111-1 performs orthogonal transform on the data rearranged in interleave section 110-1 to convert the data in the frequency domain into a signal in the time domain, and outputs the signal to radio transmission section 112-1. IFFT section 111-2 converts the data rearranged in interleaving section 110-2 into a frequency domain signal by orthogonal transform and outputs it to radio transmission section 112-2. For example, the IFFT unit 111-1 and the IFFT unit 111-2 perform fast Fourier inverse transform on the data.
[0044]
The radio transmission unit 112-1 converts the signal output from the IFFT unit 111-1 into a radio frequency and transmits it. Similarly, radio transmission section 112-2 converts the signal output from IFFT section 111-2 into a radio frequency and transmits it.
[0045]
Next, a carrier changing operation in the radio communication apparatus according to the present embodiment will be described. 2 to 7 are diagrams illustrating examples of symbol arrangement. 2 to 7, the vertical axis represents the subcarrier frequency, and the horizontal axis represents time.
[0046]
2, 3, and 4 are diagrams illustrating symbol arrangements transmitted from the wireless transmission unit 112-1. 5, FIG. 6, and FIG. 7 are diagrams of symbol arrangements transmitted from the wireless transmission unit 112-2. Here, a branch that transmits a signal from the wireless transmission unit 112-1 is referred to as branch # 1, and a branch that transmits a signal from the wireless transmission unit 112-2 is referred to as branch # 2.
[0047]
2 and 5 are diagrams showing symbol arrangements when data is first transmitted. 3 and 6 are diagrams of symbol arrangements when the same data is retransmitted. 4 and 7 are diagrams of symbol arrangement in the case of second retransmission.
[0048]
When transmitting data first, as shown in FIG. 2, radio communication apparatus 100 transmits symbols S0, S1, S2, and S3 in order of subcarriers of frequency f6 from radio transmission section 112-1, and subcarriers of frequency f3. The symbols S4, S5, S6, and S7 are transmitted in the order of the carrier.
[0049]
Further, as shown in FIG. 5, the wireless communication device 100, a symbol from the radio transmitting section 112-2 subcarrier frequency ^{f6 -S1 *, S0 *, -S3} *, and sends the order of S2 ^*, the frequency f3 The subcarriers are transmitted in the order of symbols -S5 ^* , S4 ^* , -S7 ^* , S6 ^* . These symbols -S1 ^* , S0 ^* , -S3 ^* , S2 ^* , -S5 ^* , S4 ^* , -S7 ^* , S6 ^* are symbols S0, S1, S2, S3, S4, S5, S6, S7, respectively. A symbol having a complex conjugate and having a “−” sign added is obtained by performing an operation of × (−1).
[0050]
Here, the two branches # 1 and # 2 may have a high correlation or a low correlation depending on the subcarrier to be transmitted. When the correlation between the branches is high, the transmission diversity effect cannot be obtained sufficiently.
[0051]
For example, when an error occurs when data is transmitted at the frequencies f3 and f6 when the correlation between the branches of the frequencies f3 and f6 is high, transmission diversity effect is obtained even if data is transmitted again at the frequencies f3 and f6. There is a high possibility that an error will occur again.
[0052]
Therefore, when an error occurs on the receiving side, radio communication apparatus 100 according to the present embodiment retransmits data using a subcarrier different from that at the time of initial data transmission. As illustrated in FIG. 3 and FIG. 6, the wireless communication apparatus 100 transmits data transmitted on the f3 subcarrier at f5 during retransmission, and transmits data transmitted on the f6 subcarrier at f2 upon retransmission.
[0053]
Specifically, radio communication apparatus 100 transmits symbols S0, S1, S2, and S3 in order of subcarriers at frequency f2 from radio transmission section 112-1, and symbols S4, S5, S6, and subcarriers at frequency f5. Transmit in the order of S7. Further, the symbol from the radio transmitting section 112-2 subcarrier frequency ^{f2 -S1 *, S0 *, -S3} *, and sends the order of S2 ^*, the symbol subcarrier frequencies f5 -S5 ^*, S4 ^*, -S7 ^{* And} S6 ^* are transmitted in this order.
[0054]
Further, even if the data is retransmitted, if an error occurs in the received data, radio communication apparatus 100 of the present embodiment further retransmits the data at a frequency different from the subcarrier used at the time of retransmission. For example, as shown in FIGS. 4 and 7, data transmitted on the subcarrier of f2 is transmitted at f4 at the time of retransmission, and data transmitted on the subcarrier of f5 is transmitted at f2 at the time of retransmission.
[0055]
Next, the receiving side will be described. FIG. 8 is a block diagram showing a configuration of the wireless communication apparatus according to Embodiment 1 of the present invention. 8 includes a radio reception unit 201, an FFT unit 202, a deinterleaving unit 203, a demapping unit 204, a transmission diversity decoder 205, a combining circuit 206, a demodulator 207, and a decoding unit. Unit 208, error detector 209, counter 210, deinterleaver controller 211, demapping controller 212, and wireless transmission unit 213.
[0056]
Radio receiving section 201 receives a radio signal, converts it to a baseband frequency, and outputs the obtained baseband signal to FFT section 202. The FFT unit 202 converts the baseband signal from the time domain signal to the frequency domain data by orthogonal transform and outputs the converted signal to the deinterleaving unit 203.
[0057]
The deinterleaver 203 includes a selection circuit 231 and deinterleavers 232-1 to 232-n. The deinterleaver 203 rearranges data according to instructions from the deinterleaver controller 211, and the radio communication apparatus 100 transmits the data. Restore the original order of the data Then, the deinterleaving unit 203 outputs the rearranged data to the demapping unit 204. The selection circuit 231 outputs the data to any of the deinterleavers 232-1 to 232-n according to the number of NACKs. The deinterleavers 232-1 to 232-n rearrange the data order with different interleave patterns.
[0058]
The demapping unit 204 demaps the rearranged data and outputs it to the transmission diversity decoder 205. The transmission diversity decoder 205 decodes the demapped data and outputs the decoded data to the combining circuit 206.
[0059]
The combining circuit 206 stores the data, and when the data is retransmitted, combines the data combining result up to the previous reception and the data received this time and outputs the combined data to the demodulator 207. Specifically, the synthesis circuit 206 includes a synthesizer 241 and a storage unit 242. The combiner 241 combines the data output from the transmission diversity decoder 205 and the data stored in the storage unit 242 and outputs the combined data to the storage unit 242 and the demodulator 207. The storage unit 242 stores the symbols output from the combiner 241. In addition, when the storage unit 242 receives an ACK signal from the error detector 209, the storage unit 242 resets the stored content.
[0060]
The demodulator 207 demodulates the data and outputs it to the decoder 208. The decoder 208 decodes the data and outputs it to the error detector 209. The error detector 209 determines whether there is an error in the data. The error detector 209 transmits a NACK signal to the combining circuit 206, the counter 210, and the wireless transmission unit 213 when there is an error in the data, and transmits ACK when there is no error in the data.
[0061]
The counter 210 counts the number of times the NACK signal is received for each received data, and outputs this number to the deinterleaver controller 211 and the demapping controller 212.
[0062]
The deinterleaver controller 211 instructs the deinterleaver 203 on a deinterleave pattern based on the number of times the NACK signal is received in units of data to be received, that is, the number of times an error has occurred in the data. The deinterleave pattern instructed by the deinterleaver controller 211 differs depending on the number of times the NACK signal is received, and is a pattern for deinterleaving the data interleaved by the interleaver controller 109.
[0063]
The demapping controller 212 determines a subcarrier for demapping data based on the number of times the NACK signal is received in units of data to be transmitted, and instructs the demapping unit 204. The subcarrier indicated by the demapping controller 212 differs depending on the number of times the NACK signal is received, and corresponds to the mapping pattern indicated by the mapping controller 107. The radio transmission unit 213 modulates an ACK signal or a NACK signal, converts it to a radio frequency, and transmits it.
[0064]
As described above, according to the wireless communication apparatus of this embodiment, in communication using transmission space diversity using a plurality of carriers, when an error occurs in data received on the receiving side, the subcarrier transmitted on the transmitting side By changing the correlation value between the branches for each retransmission and lowering the average of the correlation values, the transmission space diversity gain can be increased, and the throughput of the entire communication can be increased. Can be improved.
[0065]
Also, according to the radio communication apparatus of this embodiment, when an error occurs in data received on the receiving side, temporal fading at the time of retransmission is performed by changing an interleave pattern for rearranging data to be transmitted on the transmitting side. Since the correlation value can be lowered and the diversity effect is increased, the throughput of the entire communication can be improved.
[0066]
In the above description, the interleave pattern to be rearranged when data is first transmitted is fixed. However, the interleave pattern that has been successfully transmitted first can be rearranged by using the next data for the first transmission. Good. For example, when correct data can be transmitted by the second retransmission, the first transmission is performed by rearranging data to be transmitted next with the interleave pattern used in the second retransmission.
[0067]
As described above, according to the wireless communication apparatus of the present embodiment, the interleave pattern that has been successfully transmitted first is rearranged using the next data when it is first transmitted, so that it is suitable for the situation of the transmission path. Data can be transmitted using an interleave pattern, and the overall communication throughput can be improved even in an environment where burst errors occur.
[0068]
In the above description, the fast Fourier transform is used in the process of transforming the data in the frequency domain to the signal in the time domain by orthogonal transform. However, other transforms may be used as long as the transform is orthogonal. For example, discrete cosine transform, discrete Fourier transform, or the like may be used.
[0069]
Also, the number of transmission diversity branches is not limited to two, but may be any number.
[0070]
Further, in the wireless communication apparatus 200, the counter 210 is provided to count the number of transmissions. However, the wireless communication apparatus 100 may notify the wireless communication apparatus 200 of the number of transmissions of the transmission data.
[0071]
Also, in a system where retransmission is not performed or in a situation where the propagation environment is so good that retransmission is not necessary, even if a fixed interleaver is used, the correlation between branches is lowered by the mapping of the present invention, and a transmission diversity effect can be obtained. Can do.
[0072]
In the wireless communication apparatus 200, the combining circuit 206 performs packet combining at the time of retransmission, and then demodulates by the demodulator 207. After demodulating by the demodulator 207, the demodulated output is output by the combining circuit 206. The composition may be combined.
[0073]
The present invention is not limited to the above-described embodiment, and can be implemented with various modifications. For example, in the above-described embodiment, the case of performing as a wireless communication device has been described. However, the present invention is not limited to this, and the wireless communication method can be performed as software.
[0074]
For example, a program for executing the wireless communication method may be stored in advance in a ROM (Read Only Memory), and the program may be operated by a CPU (Central Processor Unit).
[0075]
In addition, a program for executing the wireless communication method is stored in a computer-readable storage medium, the program stored in the storage medium is recorded in a RAM (Random Access Memory) of the computer, and the computer operates according to the program. You may make it let it.
[0076]
【The invention's effect】
As described above, according to the wireless communication device and the wireless communication method of the present invention, in multicarrier communication to which a transmission diversity system is applied, when an error occurs in received data, a subcarrier for transmitting data is changed. By retransmitting, the opportunity to reduce the correlation between branches is increased, and the diversity gain at the time of transmission and packet combining is increased at the same time, thereby improving the throughput characteristics.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a radio communication apparatus according to Embodiment 1 of the present invention. FIG. 2 is a diagram showing an example of symbol arrangement. FIG. 3 is a diagram showing an example of symbol arrangement. FIG. 5 is a diagram showing an example of a symbol arrangement. FIG. 6 is a diagram showing an example of a symbol arrangement. FIG. 8 is a diagram showing an example of a symbol arrangement. Block diagram showing the configuration of the wireless communication device
101, 201 Wireless reception unit 102, 210 Counter 103 Encoder 104, 242 Storage unit 106-1, 106-2 Transmission diversity encoder 107 Mapping controller 108-1, 108-2 Mapping unit 109 Interleaver controller 110-1, 110-2 Interleave unit 111-1, 111-2 IFFT unit 112, 213 Radio transmission unit 121, 231 Selection circuit 122-1 to 122-n Interleaver 202 FFT unit 203 Deinterleave unit 204 Demapper 205 Transmission diversity decoder 206 Combining Circuit 209 Error detector 211 Deinterleaver controller 212 Demapping controller 232-1 to 232-n Deinterleaver 241 Synthesizer

Claims (4)

A wireless communication device that transmits data from a plurality of different antennas,
A transmission diversity encoder and mapper that forms space-time block code symbols from transmission data, an interleaving unit that interleaves the space-time block code symbols in the frequency axis direction for each retransmission, and superimposes the interleaved transmission symbols on a plurality of subcarriers An orthogonal transform unit,
The interleave unit performs the following for symbols in the same space-time block:
A radio communication apparatus characterized in that symbol sequences arranged on a first subcarrier at the time of previous transmission are collectively arranged on a second subcarrier different from the first subcarrier in the same order as at the time of previous transmission. . The wireless communication apparatus according to claim 1, wherein the interleave unit uses the same interleave pattern between the plurality of antennas.   The wireless communication apparatus according to claim 1, wherein the interleave unit uses an interleave pattern when data is correctly transmitted for rearrangement of data to be transmitted next. A wireless communication method for transmitting a multicarrier signal from each of a plurality of antennas,
Forming a space-time block code symbol from transmission data, an interleaving step of interleaving the space-time block code symbol in the frequency axis direction for each retransmission, and superimposing the interleaved transmission symbol on a plurality of subcarriers. ,
In the interleaving step, for symbols in the same space-time block,
A radio communication method characterized in that symbol sequences arranged on the first subcarrier at the previous transmission are arranged together in the same order as at the previous transmission on a second subcarrier different from the first subcarrier. .

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