JP3678930B2 - OFDM transmission apparatus and OFDM transmission method - Google Patents

OFDM transmission apparatus and OFDM transmission method Download PDF

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Publication number
JP3678930B2
JP3678930B2 JP00766999A JP766999A JP3678930B2 JP 3678930 B2 JP3678930 B2 JP 3678930B2 JP 00766999 A JP00766999 A JP 00766999A JP 766999 A JP766999 A JP 766999A JP 3678930 B2 JP3678930 B2 JP 3678930B2
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Prior art keywords
signal
symbol
correlation value
ofdm
synchronization
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JP00766999A
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JP2000209179A (en
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浩章 須藤
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松下電器産業株式会社
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Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is used for OFDM wireless communication. OFDM transmission apparatus and OFDM transmission method About.
[0002]
[Prior art]
In general, in OFDM wireless communication, a transmission signal is added immediately before a guard symbol for removing an effect of an effective symbol including user data, a delay wave added immediately before the effective symbol, and a guard wave. A phase reference symbol that is a known symbol for symbol synchronization, a synchronization symbol that is the same signal as the phase reference symbol added immediately before the phase reference symbol, and an AGC (Auto Gain) added immediately before the synchronization symbol AGC symbols for performing control).
[0003]
In OFDM wireless communication, symbol synchronization is performed on the receiving station side using a synchronization symbol and a phase reference symbol. That is, a correlation is obtained between the received signal and the received signal delayed by one symbol, and the timing at which the correlation value reaches a peak is detected.
[0004]
However, in this case, since the AGC symbol is inserted immediately before the synchronization symbol, interference occurs between the AGC symbol and the synchronization symbol, and the accuracy of the symbol synchronization timing detected on the receiving station side is deteriorated. Problem arises. Since the symbol synchronization timing is used as the FFT processing start timing, deterioration in detection accuracy of the symbol synchronization timing causes a synchronization shift.
[0005]
Therefore, in the conventional OFDM transmitter / receiver, the first half of the AGC symbol is the same signal as the first half of the synchronization symbol, and the second half of the AGC symbol is a signal obtained by inverting the polarity of the second half of the synchronization symbol. By suppressing the correlation value in front of the symbol synchronization timing to be detected and in the vicinity of the peak to be small, deterioration of symbol synchronization timing detection accuracy due to the influence of the AGC symbol is prevented.
[0006]
Hereinafter, a conventional OFDM transmission / reception apparatus will be described with reference to FIGS. FIG. 8 is a principal block diagram showing a schematic configuration of a conventional OFDM transmitting / receiving apparatus, FIG. 9 is a schematic diagram showing a frame configuration of a transmission signal in conventional OFDM wireless communication, and FIG. It is a schematic diagram which shows the correlation result of the received signal in the receiving system of OFDM transmission / reception apparatus.
[0007]
In the OFDM transmitter / receiver shown in FIG. 8, first, an information signal for each subcarrier is digitally modulated by a modulation unit 801, for example, by QPSK (Quadrature Phase Shift Keying) or QAM (Quadrature Amplitude Modulation). An AGC symbol insertion unit 802 inserts an AGC symbol, and a synchronization symbol insertion unit 803 inserts a synchronization symbol.
[0008]
The signal in which the synchronization symbol is inserted is subjected to IFFT processing in an IFFT (Inverse Fast Fourier Transform) unit 804 to become an OFDM signal. In this OFDM signal, a guard interval is inserted by a guard interval insertion unit 805.
[0009]
In this way, the transmission signal has the frame configuration shown in FIG. 9, and the AGC symbol 901, the synchronization symbol 902, the phase reference symbol 903 that is the same signal as the synchronization symbol 902, the guard interval 904, and the effective signal Symbol 905.
[0010]
Here, the synchronization symbol 902 and the phase reference symbol 903 are the same signal and are known signals. The phase reference symbol 903 is, for example, a pilot symbol.
[0011]
The first half of the AGC symbol 901 is the same signal as the first half of the synchronization symbol 902, and the second half of the AGC symbol 901 is a signal obtained by inverting the polarity of the second half of the synchronization symbol 902.
[0012]
The signal with the guard interval inserted is D / A converted by the D / A converter 806 to become a baseband signal. This baseband signal is subjected to normal wireless transmission processing by a wireless transmission unit (not shown) and transmitted as a transmission signal via an antenna.
[0013]
On the other hand, in the reception system, a signal received via an antenna is subjected to normal wireless reception processing by a wireless reception unit (not shown) to become a baseband signal. This baseband signal is subjected to quadrature detection processing by a quadrature detector, and unnecessary frequency components are removed by a low-pass filter (both the quadrature detector and the low-pass filter are not shown). This baseband signal is A / D converted by an A / D converter 807. Although the received signal is divided into an in-phase component and a quadrature component by the quadrature detection processing, it is shown as one signal path in FIG.
[0014]
This baseband signal is subjected to FFT processing in an FFT (Fast Fourier Transform) unit 813, and a signal assigned to each subcarrier is obtained. At this time, the baseband signal is delayed by the delay unit 808 and sent to the multiplier 809, and the multiplication results are accumulated by the accumulation unit 810. Then, the integration result is sent to the subtracter 811, subtracted from the threshold value, and the threshold value is determined by the determination unit 812. The determination result is sent to the FFT unit 813.
[0015]
The signal subjected to the FFT processing by the FFT unit 813 is sent to the demodulation unit 814, subjected to delay detection processing, and the determination unit 815 determines whether it is different from the signal one bit before and becomes a demodulated signal.
[0016]
When symbol synchronization is performed in the OFDM transmitter / receiver having the above configuration, first, a baseband signal before FFT processing and a signal obtained by delaying the signal before FFT processing by a delay unit 808 by one symbol are sent to a multiplier 809. Therefore, complex multiplication processing is performed.
[0017]
Next, the output of the multiplication unit 809 is sent to the integration unit 810, and the complex multiplication results are integrated. The integration result is shown in FIG.
[0018]
Here, since the phase reference symbol 903 is the same signal as the synchronization symbol 902, the integration result of both, that is, the integration result of the integration interval c in FIG. 10, is 1 as shown in the correlation result in FIG. Since a peak occurs in the phase reference symbol 903 of the signal delayed by the symbol, symbol synchronization can be established by detecting the timing at which the integration result exceeds the threshold value.
[0019]
Furthermore, since the latter half of the AGC symbol 901 is obtained by inverting the polarity of the latter half of the synchronization symbol 902, the integration result in the integration interval a and the integration interval b in FIG. Thus, it is possible to prevent the synchronization symbol 902 from interfering with it and detecting an erroneous peak.
[0020]
As described above, the conventional OFDM transmitter / receiver uses the same signal as the first half of the synchronization symbol 902 for the first half of the AGC symbol 901 and reverses the polarity of the second half of the synchronization symbol 902 for the second half of the AGC symbol 901. The accuracy of the symbol synchronization timing can be increased by using the signal.
[0021]
[Problems to be solved by the invention]
However, the conventional OFDM transmitter / receiver has the following problems. That is, since the first half portion and the second half portion of the AGC symbol 901 have different polarities, the signal becomes discontinuous and the spectrum of the transmission signal spreads. When the spectrum of the transmission signal spreads, not only does it interfere with other users' bands, but also excess transmission power is consumed due to the influence of unnecessary frequency components.
[0022]
Also, since the phase between a plurality of, for example, 20 subcarriers varies independently, the latter half of the AGC symbol 901 generated by inverting the polarity of the latter half of the synchronization symbol 902 depends on the subcarrier. It may be in phase with or out of phase with the synchronization symbol 902.
[0023]
When the latter half of the AGC symbol 901 is in phase with the synchronization symbol 902 due to phase fluctuation, the correlation value is increased, and the peak of the correlation value is shifted forward in time, making it impossible to detect an appropriate symbol synchronization timing.
[0024]
In addition, when the latter half of the AGC symbol 901 is out of phase with the synchronization symbol 902 due to phase fluctuation, the correlation value is suppressed, so the correlation value peak shifts backward in time and the appropriate symbol synchronization timing is detected. become unable.
[0025]
The present invention has been made in view of the above points, and detects symbol synchronization timing accurately even in a multipath environment to prevent synchronization deviation. OFDM transmission apparatus and OFDM transmission method The purpose is to provide.
[0026]
[Means for Solving the Problems]
The essence of the present invention is that a reception signal delayed by one symbol from the reception signal on the receiving station side by inserting a correlation value suppression signal of, for example, 0 symbol between the AGC symbol and the synchronization symbol of the transmission signal. When the symbol synchronization timing is detected by taking the correlation between the received signal and the AGC symbol of the received signal delayed by one symbol, the magnitude of the correlation result is suppressed, and the phase reference of the received signal is suppressed. A peak appears only in the correlation result between the symbol and the synchronization symbol of the received signal delayed by one symbol.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
An OFDM transmission apparatus according to the first aspect of the present invention includes: An OFDM transmitter that transmits an automatic gain control symbol and transmits a synchronization symbol after the automatic gain control symbol, Of the automatic gain control symbol Immediately after and immediately before the synchronization symbol Insert correlation value suppression signal To generate OFDM signal Correlation value suppression signal inserting means for Generated OFDM signal And a transmission means for transmitting. The OFDM transmitter according to the second aspect of the present invention is a receiver that detects a symbol synchronization timing by performing threshold determination on a correlation value between a received signal and a signal obtained by delaying the received signal by a unit symbol. An OFDM transmission apparatus for transmitting a signal, the automatic gain control symbol inserting means for inserting an automatic gain control symbol into an effective symbol including user data to be transmitted to the receiving apparatus, and the automatic gain control symbol Immediately after Correlation value suppression signal insertion means for inserting a correlation value suppression signal; and Immediately after Synchronization symbol insertion means for inserting a synchronization symbol, and transmission means for OFDM transmission of the signal obtained by inserting the automatic gain control symbol, the correlation value suppression signal and the synchronization symbol into the effective symbol. Take the configuration.
[0028]
these According to the configuration of A correlation value suppression signal can be inserted between the automatic gain control symbol and the synchronization symbol. The correlation value in front of the symbol synchronization timing and near the peak is kept small. So you can The symbol synchronization timing can be detected accurately, Between the transmitter and receiver Synchronization loss can be prevented.
[0031]
According to the third aspect of the present invention In OFDM transmitter Said Correlation value suppression signal The inserting means adopts a configuration that adaptively changes the section length of the correlation value suppression signal according to the channel quality of the received signal.
[0032]
According to this configuration, since the insertion of the correlation value suppression signal can be switched, the interval of the correlation value suppression signal in the signal frame can be made adaptively variable, depending on the channel quality. Can be handled flexibly.
[0033]
According to the fourth aspect of the present invention The OFDM transmitter comprises an averaging means for averaging the line quality of the received signal, and the correlation value suppression signal inserting means is averaged Received signal line quality Use Take the configuration.
[0034]
According to this configuration, by using the average value of a plurality of bursts for channel quality estimation, it is possible to prevent the correlation value suppression signal from being lengthened when a value exceeding the threshold is suddenly obtained.
[0035]
According to the fifth aspect of the present invention In OFDM transmitter Said Correlation value suppression signal insertion Means that the line quality of the received signal is poor The longer the section length of the correlation value suppression signal is controlled Take the configuration.
[0036]
According to this configuration, when it is determined that the channel quality is poor, it is determined that the section length of the current correlation value suppression signal is short, and control is performed to lengthen the section of the correlation value suppression signal. The error can be eliminated. In addition, when it is determined that the channel quality is good, since the control for shortening the interval of the correlation value suppression signal is performed, the transmission efficiency can be improved.
[0037]
According to the sixth aspect of the present invention In OFDM transmitter Said Correlation value suppression signal insertion The means is the correlation value suppression signal. As Null symbol or null signal Use Take the configuration.
[0038]
According to this configuration, since the correlation value in front of the symbol synchronization timing and near the peak can be suppressed, the symbol synchronization timing can be accurately detected.
[0039]
The base station apparatus according to the seventh aspect of the present invention is: OFDM transmission apparatus according to any of the above aspects The structure which comprises is taken.
[0040]
According to this configuration, since the symbol synchronization timing can be accurately detected, for example, it is possible to prevent a synchronization shift with a communication partner station that is a communication terminal device.
[0041]
A communication terminal device according to the eighth aspect of the present invention provides: OFDM transmission apparatus according to any of the above aspects The structure which comprises is taken.
[0042]
According to this configuration, since the symbol synchronization timing can be accurately detected, for example, it is possible to prevent a synchronization shift with a communication partner station that is a base station apparatus.
[0043]
An OFDM transmission method according to the ninth aspect of the present invention includes: A transmission method of an OFDM transmitter for transmitting an automatic gain control symbol and transmitting a synchronization symbol after the automatic gain control symbol, Of the automatic gain control symbol Immediately after and immediately before the synchronization symbol Insert correlation value suppression signal To generate OFDM signal And the step of Generated OFDM signal And a step of transmitting.
[0044]
According to this method, the correlation value suppression signal is inserted between the AGC symbol and the synchronization symbol in the transmission signal, and the symbol synchronization timing is reduced in order to suppress the correlation value in front of the symbol synchronization timing and near the peak. It is possible to detect accurately, and to prevent synchronization deviation between the transmitting station and the receiving station.
[0045]
According to the tenth aspect of the present invention OFDM transmission method The section length of the correlation value suppression signal is adaptively changed according to the line quality of the received signal.
[0046]
According to this method, since it is possible to switch the insertion of the correlation value suppression signal, the interval of the correlation value suppression signal in the signal frame can be made adaptively variable, depending on the channel quality. Can be handled flexibly.
[0047]
According to the eleventh aspect of the present invention OFDM transmission method Is The line quality of the average received signal I used it.
[0048]
According to this method, by using the average value of a plurality of bursts for channel quality estimation, it is possible to prevent the correlation value suppression signal from being lengthened when a value exceeding the threshold value is suddenly obtained.
[0049]
According to the twelfth aspect of the present invention OFDM transmission method The line quality of the received signal is poor The longer the section length of the correlation value suppression signal is, I tried to control it.
[0050]
According to this method, when it is determined that the channel quality is poor, it is determined that the section length of the current correlation value suppression signal is short, and control is performed to lengthen the section of the correlation value suppression signal. The error can be eliminated. In addition, when it is determined that the channel quality is good, since the control for shortening the interval of the correlation value suppression signal is performed, the transmission efficiency can be improved.
[0051]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
The OFDM transmitter / receiver according to the present embodiment inserts 0 symbols (null symbols) as correlation value suppression signals between AGC symbols and synchronization symbols of transmission signals.
[0052]
Hereinafter, the OFDM transmission / reception apparatus according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a principal block diagram showing a schematic configuration of an OFDM transceiver apparatus according to Embodiment 1 of the present invention, and FIG. 2 shows transmission signals generated by the OFDM transceiver apparatus according to Embodiment 1 of the present invention. FIG. 3 is a schematic diagram showing a frame configuration, and FIG. 3 is a schematic diagram showing a correlation result of received signals in the reception system of the OFDM transceiver apparatus according to Embodiment 1 of the present invention.
[0053]
In the OFDM transmission / reception apparatus shown in FIG. 1, a modulation section 101 performs digital modulation processing on an information signal for each subcarrier using, for example, QPSK or QAM.
[0054]
AGC symbol insertion section 102 inserts AGC symbols in the transmission signal, synchronization symbol insertion section 103 inserts synchronization symbols and phase reference symbols, and correlation value suppression signal insertion section 104 inserts 0 symbols. . Each insertion part is comprised with a switch, each switched by the control signals 1-3, and inserts each signal in a transmission signal.
[0055]
The IFFT unit 105 performs IFFT processing on the transmission signal in which the predetermined symbol is inserted. The guard interval insertion unit 106 inserts a guard interval into the IFFT-processed transmission signal.
[0056]
The D / A conversion unit 107 performs D / A conversion on the transmission signal in which the guard interval is inserted to obtain a baseband signal.
[0057]
On the other hand, in the reception system, the A / D converter 108 performs A / D conversion on the baseband signal of the received signal, and the FFT unit 114 performs FFT processing on the baseband signal. The delay unit 109 delays the baseband signal by one symbol and outputs the delayed signal to the multiplier 110. The multiplier 110 outputs the baseband signal output from the A / D conversion unit 108 and the one symbol output from the delay unit 109. Complex multiplication processing is performed on the delayed baseband signal.
[0058]
The integration unit 111 integrates the output of the multiplier 110. The subtractor 112 subtracts the output of the integrating unit 111 and the threshold value, and the determination unit 113 determines the threshold value of the output of the subtractor 112 and outputs the determination result to the FFT unit 114.
[0059]
The FFT unit 114 performs FFT processing on the baseband signal that is output from the A / D conversion unit 108 at a timing based on the output of the determination unit 113, and the demodulation unit 115 performs processing on the received signal after the FFT processing. Delay detection processing is performed, and the determination unit 116 determines whether the signal is different from the signal one bit before, and becomes a demodulated signal.
[0060]
Next, the operation of the OFDM transmitter / receiver having the above configuration will be described.
[0061]
In FIG. 1, the information signal for each subcarrier is first digitally modulated by the modulation unit 101.
[0062]
In the digitally modulated transmission signal, an AGC symbol insertion unit 102 inserts an AGC symbol before an effective symbol including user data, and a synchronization symbol insertion unit 102 inserts an AGC symbol between the effective symbol and the effective symbol. The synchronization symbol and the phase reference symbol are inserted into the signal, and the correlation value suppression signal insertion unit 104 inserts 0 symbol between the AGC symbol and the synchronization symbol.
[0063]
Here, the phase reference symbol is a known signal which is, for example, a pilot symbol, and the synchronization symbol is the same signal as the phase reference symbol.
[0064]
The IFFT unit 105 performs IFFT processing, that is, IFFT processing on the time axis of complex number data including phase and amplitude information on the frequency axis is performed on the transmission signal in which the predetermined symbol is inserted. It becomes a signal waveform on the time axis.
[0065]
Next, a guard interval is inserted between the phase reference symbol and the effective symbol by the guard interval insertion unit 106 in the signal waveform after IFFT processing. The guard interval is the same as the waveform of a part of the rear end portion of the effective symbol, which eliminates the influence of the delayed wave, suppresses an increase in the bit error rate, and contributes to improving the multipath resistance.
[0066]
FIG. 2 shows the frame structure of the transmission signal after insertion of the guard interval. The transmission signal is composed of AGC symbol 201, 0 symbol 202, synchronization symbol 203, phase reference symbol 204, guard interval 205, and effective symbol 206 in order from the front in time.
[0067]
The transmission signal in which the guard interval is inserted is D / A converted by the D / A conversion unit, frequency-converted and amplified by a radio transmission unit (not shown), and transmitted from the antenna.
[0068]
On the other hand, the signal received from the antenna is amplified by a radio reception unit (not shown), frequency-converted, A / D converted by the A / D conversion unit 108, and becomes a baseband signal. As described above, the received signal is processed by being divided into an in-phase component and a quadrature component by a quadrature detector (not shown), but is represented by one path in the figure.
[0069]
Hereinafter, symbol synchronization timing detection in the reception system will be described. The symbol synchronization timing is a start timing when the FFT unit 114 performs FFT processing on the baseband signal.
[0070]
First, the baseband signal before FFT processing, which is the output of the A / D conversion unit 108, is delayed by a delay unit 109 by one unit symbol, for example, one symbol.
[0071]
Next, the multiplier 110 multiplies the baseband signal before FFT processing, which is the output of the A / D conversion unit 108, and the baseband signal before FFT processing, which is the output of the delay unit 109, by one symbol. It is processed.
[0072]
Next, the output of the multiplier 110 is integrated by the integration unit 111. The state of the integration process is shown in FIG.
[0073]
In the integration interval a and the integration interval b in FIG. 3, the calculated correlation value is kept low because one of the symbols to be correlated is 0 symbol.
[0074]
On the other hand, in the integration period c in FIG. 3, since the phase reference symbol 204 and the synchronization symbol 203 are the same signal, the integration result of both is a unit symbol (here, one symbol) as shown in FIG. A peak occurs at the phase reference symbol of the delayed received signal.
[0075]
In order to detect this peak, the integration result, which is the output of the integration 111, is output to the subtraction unit 112, subtracted from the predetermined threshold value by the subtraction unit 112, and the determination unit 113 determines the magnitude of the subtraction result. Thus, a threshold determination is made for the integration result, and a peak, that is, a timing when the threshold value is exceeded is detected.
[0076]
In this case, since the 0 symbol is inserted, the correlation result is very small in front of the symbol synchronization timing to be detected and in the vicinity of the peak, specifically, in the integration interval a and the integration interval b in FIG. Therefore, the peak can be accurately identified.
[0077]
The detected peak can be used as the FFT processing start timing in the FFT unit 114 as the symbol synchronization timing. In this way, it is possible to start FFT with symbol synchronization between the transmission side and the reception side.
[0078]
Based on the symbol synchronization timing detected in this way, the baseband signal subjected to A / D conversion processing is subjected to FFT processing by the FFT section 114, and a signal assigned to each subcarrier is obtained. This signal is subjected to delay detection processing by the demodulator 115, and is compared with the signal one bit before by the determination unit 116 to become a demodulated signal.
[0079]
As described above, according to the present embodiment, a symbol of 0 is inserted between the AGC symbol and the synchronization symbol in the transmission signal, and the correlation value in front of the symbol synchronization timing and near the peak is kept small. The synchronization timing can be accurately detected, and a synchronization shift between the transmitting station and the receiving station can be prevented.
[0080]
(Embodiment 2)
The apparatus according to the present embodiment has the same configuration as that of the first embodiment, except that the correlation value suppression signal inserted between the AGC symbol and the synchronization symbol in the transmission signal is shorter than the unit symbol length. The section length is 0 signal (null signal).
[0081]
Hereinafter, the OFDM transmission / reception apparatus according to the present embodiment will be described with reference to FIG. 4 and FIG. FIG. 4 is a principal block diagram showing a schematic configuration of an OFDM transceiver apparatus according to Embodiment 2 of the present invention, and FIG. 5 shows transmission signals generated by the OFDM transceiver apparatus according to Embodiment 2 of the present invention. It is a schematic diagram which shows a frame structure. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 1, and detailed description is abbreviate | omitted.
[0082]
In FIG. 4, a correlation value suppression signal insertion unit 401 provided immediately after the guard interval insertion unit 106 transmits a 0 signal between the AGC symbol 201 and the synchronization symbol 203 of the transmission signal in which the guard interval is inserted. insert.
[0083]
FIG. 5 shows the frame structure of the transmission signal after the 0 signal is inserted. Here, the section length of the 0 signal 501 is made shorter than the unit symbol length. The section length of the 0 signal 501 is preferably set to the same length as the guard section, for example.
[0084]
In this case, since the zero signal is inserted, the correlation result in front of the symbol synchronization timing to be detected and in the vicinity of the peak becomes a very small value, so that the peak can be accurately identified.
[0085]
As described above, according to the present embodiment, a zero signal is inserted between the AGC symbol and the synchronization symbol in the transmission signal, and the correlation value in front of the symbol synchronization timing and near the peak is kept small. The synchronization timing can be accurately detected, and a synchronization shift between the transmitting station and the receiving station can be prevented.
[0086]
Further, since the section length of the correlation value suppression signal inserted into the transmission signal is shorter than the unit symbol length, it is possible to prevent a decrease in transmission efficiency compared to the first embodiment.
[0087]
(Embodiment 3)
The OFDM transmission / reception apparatus according to the present embodiment has the same configuration as that of the second embodiment, except that the section length of the 0 signal to be inserted is changed according to the line quality.
[0088]
Hereinafter, the OFDM transmission / reception apparatus according to the present embodiment will be described with reference to FIG. FIG. 6 is a principal block diagram showing a schematic configuration of an OFDM transceiver apparatus according to Embodiment 3 of the present invention. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 1, and detailed description is abbreviate | omitted.
[0089]
In FIG. 6, a subtractor 605 subtracts the input signal and output signal of the determination unit 116, a subtractor 604 subtracts the calculated subtraction result and the threshold value, and the determination unit 603 A threshold value is determined for the calculated subtraction result. Here, if the output of the subtracter 605 is larger than the threshold value, it is determined that the line quality is poor.
[0090]
The switch 602 outputs the control signal 5 or the control signal 6 to the correlation value suppression signal insertion unit 601 based on the output of the determination unit 603 that is the estimated channel quality. Correlation value suppression signal insertion section 601 inserts a 0 signal into the transmission signal after the guard interval is inserted based on the control signal sent from switch 602.
[0091]
Here, it is assumed that correlation value suppression signal insertion section 601 inserts a 0 signal when control signal 5 is input, and does not insert a 0 signal when control signal 6 is input. Therefore, the control signal 5 or the control signal 6 is appropriately output from the switch 602 based on the output of the determination unit 603 that is the estimated channel quality, so that the length of the 0 signal inserted into the transmission signal is determined as the channel quality. It can be changed according to.
[0092]
Specifically, if it is determined that the line quality is poor, it is determined that the current 0 signal interval is short, and control is performed to increase the 0 signal interval to eliminate timing errors. Conversely, when it is determined that the channel quality is good, control is performed to shorten the 0 signal interval in order to improve transmission efficiency.
[0093]
As described above, according to the present embodiment, a zero signal is inserted between the AGC symbol and the synchronization symbol in the transmission signal, and the correlation value in front of the symbol synchronization timing and near the peak is kept small. The synchronization timing can be accurately detected, and a synchronization shift between the transmitting station and the receiving station can be prevented.
[0094]
In addition, since a configuration capable of switching insertion of 0 signal is adopted, the section of 0 signal in the signal frame can be made adaptively variable, and processing can be flexibly handled according to the line quality. .
[0095]
(Embodiment 4)
The OFDM transmission / reception apparatus according to the present embodiment has the same configuration as that of the third embodiment, but is averaged.
[0096]
Hereinafter, the OFDM transmission / reception apparatus according to the present embodiment will be described with reference to FIG. FIG. 7 is a principal block diagram showing a schematic configuration of an OFDM transceiver apparatus according to Embodiment 4 of the present invention. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 1 and 3, and detailed description is abbreviate | omitted.
[0097]
In FIG. 7, the averager 701 calculates the burst average of the subtraction result that is the output of the subtractor 605. Therefore, it is possible to prevent the 0 signal section from being lengthened when a value exceeding the threshold value is suddenly obtained.
[0098]
As described above, according to the present embodiment, a zero signal is inserted between the AGC symbol and the synchronization symbol in the transmission signal, and the correlation value in front of the symbol synchronization timing and near the peak is kept small. The synchronization timing can be accurately detected, and a synchronization shift between the transmitting station and the receiving station can be prevented.
[0099]
In addition, since a configuration capable of switching insertion of 0 signal is adopted, the section of 0 signal in the signal frame can be made adaptively variable, and processing can be flexibly handled according to the line quality. .
[0100]
Further, by using an average value of a plurality of bursts for channel quality estimation, it is possible to prevent the 0 signal from being lengthened when a value exceeding the threshold value is suddenly obtained.
[0101]
Note that the correlation value suppression signal as described in the first to fourth embodiments can be input immediately after the phase reference symbol. In this case, since the correlation value behind the symbol synchronization timing and in the vicinity of the peak can be suppressed small, it contributes to the accurate detection of the symbol synchronization timing as in the present invention. Of course, these can be used in combination.
[0102]
The OFDM transmission / reception apparatus of the present invention can be applied to a communication terminal apparatus and a base station apparatus in an OFDM wireless communication system.
[0103]
【The invention's effect】
As described above, according to the present invention, it is possible to accurately detect the symbol synchronization timing even in a multipath environment and prevent synchronization deviation.
[Brief description of the drawings]
FIG. 1 is a principal block diagram showing a schematic configuration of an OFDM transceiver apparatus according to Embodiment 1 of the present invention;
FIG. 2 is a schematic diagram showing a frame configuration of a transmission signal generated by the OFDM transceiver apparatus according to Embodiment 1 of the present invention;
FIG. 3 is a schematic diagram showing a correlation result of received signals in the receiving system of the OFDM transceiver apparatus according to Embodiment 1 of the present invention;
FIG. 4 is a principal block diagram showing a schematic configuration of an OFDM transceiver apparatus according to Embodiment 2 of the present invention.
FIG. 5 is a schematic diagram showing a frame configuration of a transmission signal generated by an OFDM transceiver apparatus according to Embodiment 2 of the present invention;
FIG. 6 is a principal block diagram showing a schematic configuration of an OFDM transceiver apparatus according to Embodiment 3 of the present invention.
FIG. 7 is a principal block diagram showing a schematic configuration of an OFDM transceiver apparatus according to Embodiment 4 of the present invention;
FIG. 8 is a principal block diagram showing a schematic configuration of a conventional OFDM transmitting / receiving apparatus.
FIG. 9 is a schematic diagram showing a frame structure of a transmission signal in conventional OFDM wireless communication.
FIG. 10 is a schematic diagram showing a correlation result of received signals in a receiving system of a conventional OFDM transmitting / receiving apparatus.
[Explanation of symbols]
102 Symbol insertion part for AGC
103 Symbol insertion part for synchronization
104 Correlation Value Suppression Signal Insertion Unit
201 Symbol for AGC
202 0 symbols
203 Symbol for synchronization
204 Phase reference symbol
401 Correlation Value Suppression Signal Insertion Unit
501 0 signal
601 Correlation value suppression signal insertion unit

Claims (12)

  1. An OFDM transmitter that transmits an automatic gain control symbol and transmits a synchronization symbol after the automatic gain control symbol,
    Correlation value suppression signal insertion means for generating an OFDM signal by inserting a correlation value suppression signal immediately after the automatic gain control symbol and immediately before the synchronization symbol, and transmission means for transmitting the generated OFDM signal An OFDM transmitter characterized by comprising:
  2. An OFDM transmitter that transmits a signal to a receiver that detects a symbol synchronization timing by performing threshold determination on a correlation value between a received signal and a signal obtained by delaying the received signal by a unit symbol,
    Automatic gain control symbol inserting means for inserting an automatic gain control symbol into an effective symbol including user data to be transmitted to the receiving apparatus; and a correlation value for inserting a correlation value suppression signal immediately after the automatic gain control symbol. Suppression signal insertion means, synchronization symbol insertion means for inserting a synchronization symbol immediately after the correlation value suppression signal, the automatic gain control symbol, the correlation value suppression signal, and the synchronization symbol in the effective symbol An OFDM transmission apparatus comprising: transmission means for OFDM transmission of a signal in which is inserted.
  3.   3. The OFDM transmitter according to claim 1, wherein the correlation value suppression signal inserting means adaptively changes a section length of the correlation value suppression signal in accordance with a channel quality of a received signal.
  4.   4. The OFDM transmitter according to claim 3, further comprising: averaging means for averaging the channel quality of the received signal, wherein the correlation value suppression signal inserting means uses the averaged channel quality of the received signal. .
  5.   5. The OFDM transmission according to claim 3, wherein the correlation value suppression signal inserting means performs control to increase a section length of the correlation value suppression signal as the channel quality of the received signal is poor. apparatus.
  6.   6. The OFDM transmission apparatus according to claim 1, wherein the correlation value suppression signal inserting means uses a null symbol or a null signal as the correlation value suppression signal.
  7.   A base station apparatus comprising the OFDM transmission apparatus according to any one of claims 1 to 6.
  8.   A communication terminal apparatus comprising the OFDM transmission apparatus according to claim 1.
  9. A transmission method of an OFDM transmitter for transmitting an automatic gain control symbol and transmitting a synchronization symbol after the automatic gain control symbol,
    A step of generating an OFDM signal by inserting a correlation value suppression signal immediately after the automatic gain control symbol and immediately before the synchronization symbol, and transmitting the generated OFDM signal. A characteristic OFDM transmission method.
  10.   10. The OFDM transmission method according to claim 9, wherein the section length of the correlation value suppression signal is adaptively changed according to the channel quality of the received signal.
  11.   11. The OFDM transmission method according to claim 10, wherein the channel quality of the average received signal is used.
  12.   12. The OFDM transmission method according to claim 10, wherein control is performed such that the section length of the correlation value suppression signal becomes longer as the channel quality of the received signal is worse.
JP00766999A 1999-01-14 1999-01-14 OFDM transmission apparatus and OFDM transmission method Expired - Fee Related JP3678930B2 (en)

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