JP2007166172A - Radio communication device and synchronization acquisition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute the acquisition of synchronization with improved performance even if patterns similar to a fixed pattern are present before and after utilizing the repetition fixed pattern in a preamble section and even if CNR is small, when using the repetition fixed pattern when synchronizing the receiver of a radio communication system. <P>SOLUTION: The complex correlation value is calculated between a reception signal and the repetition fixed pattern (S32); A values separated by N symbols in the complex correlation value are added successively to obtain a sum (S33); and the difference of the added results of the peak positions separated by N symbols is calculated (S35, S36) to each of the maximum peak position and the next maximum peak position of the added result. Then the differences are compared (S37), a peak position (either the maximum peak position or the next maximum peak position) having a smaller difference is adopted as a true maximum peak position, and a synchronization position is determined in reference to the position (S38). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus used in a wireless communication system such as a digital cellular phone and a wireless LAN, and a synchronization acquisition method in the wireless communication apparatus.

  A wireless communication system in which a fixed pattern of a certain length is repeatedly inserted into a communication signal on the transmission side during transmission / reception of wireless communication, and synchronization can be acquired using the fixed pattern inserted into the communication signal on the reception side. Exists.

  As a conventional technique for performing synchronization acquisition using the above-described repeated fixed pattern (FP), there is one disclosed in Patent Document 1, for example. Hereinafter, this will be described as a conventional example with reference to FIGS.

  FIG. 8 is a diagram illustrating an example of a transmission frame format having a repetitive fixed pattern used for wireless communication. The transmission frame format of the communication signal includes a preamble period for performing frame synchronization detection and the like and an information data period, and a known fixed pattern FP having a symbol length of N symbols is repeatedly transmitted during the preamble period.

FIG. 9 shows an example of a received sample sequence when the repetitive fixed pattern corresponding to the transmission frame format of FIG. 8 is for five periods (FP _{0 to} FP ₄ ). In FIG. 9, (a) shows a transmission frame format, (b) shows a received sample sequence, and (c) shows a complex conjugate of a repetitive fixed pattern. S _x in (b) is a received sample string (symbol time interval) of the x sample of the repetitive fixed pattern. In (c), F _x ^* is a complex conjugate (symbol time interval) of a repetitive fixed pattern. The actual received sample sequence is oversampled with respect to the symbol rate, but is simplified because it is not directly related to the technical description.

  On the receiving side, cross-correlation vectors with N symbol repetitive fixed patterns are successively calculated for the samples received during the preamble period of the communication signal.

When the symbols shown in FIG. 9 are used, the calculated complex correlation vector corr _i (i is an arbitrary integer) is calculated as shown in Equation 1 below.

Here, the complex correlation value corr _i is a position where the known fixed pattern inserted on the transmission side and the pattern of the received sample data overlap, that is, the position of i = aN (a = 0, 1, 2, 3, 4). Peak at an interval of N symbols. FIG. 10 is a diagram illustrating the complex correlation values calculated in the example of FIG.

Then, on the receiving side, with respect to the calculated complex correlation values corr _i, sequentially calculates the complex correlation value five sum of N symbols away. The sum corr5 _{i of the} five complex correlation values is calculated as shown in Equation 2 below.

  FIG. 11 is a diagram illustrating an example of the sum of five complex correlation values separated by N symbols calculated based on the complex correlation values of FIG. As shown in FIG. 11, the sum of five complex correlation values has nine peaks at N symbol intervals at the position i = aN (a = 0, ± 1, ± 2, ± 3, ± 4). Among these, the peak position (position where i = 0) having the maximum value is a position including all the repeated fixed patterns for five cycles. Therefore, the synchronization position can be determined based on the maximum peak position.

  Now, consider the case where the data before and after the repeated fixed pattern is the same data as the fixed pattern (data whose complex correlation value with the fixed pattern is large). Here, as an example, a case where a transmission signal in which the data behind the repeated fixed pattern as shown in FIG. 12 is the same data as the repeated pattern is received is shown. FIG. 12 is a diagram illustrating an example of a transmission signal. FIG. 13 is a diagram showing the complex correlation values calculated in the example of FIG. 12, and FIG. 14 is an example of the sum of five complex correlation values separated by N symbols calculated based on the complex correlation values of FIG. FIG.

  In the case of this example, as shown in FIG. 13, a peak pa occurs in the complex correlation value between the received sample sequence and the fixed pattern even in the information data period. That is, when data similar to the fixed pattern is included in the information data period, the peak of the complex correlation value stands up even though it is not a fixed pattern as in the position of i = 5N.

Further, as shown in FIG. 14, the maximum value of the two peak positions pb1 and pb2 antagonizes the sum of five complex correlation values separated by N symbols. Therefore, when the synchronization position is determined by searching for the peak position of the sum of five complex correlation values, the maximum of a plurality of peak positions, such as the value of corr5 _i at the position of i = 0 and the position of i = N, is determined. Since the values compete with each other, when the CNR is small, the selection of the maximum peak position may be wrong and synchronization acquisition may fail.

JP 2003-110523 A

  The present invention has been made in view of the above circumstances, and when using a repeated fixed pattern in a preamble section in acquiring synchronization of a wireless receiver, when a pattern similar to the fixed pattern exists before and after or when the CNR is small The purpose of the present invention is to provide a wireless communication apparatus and a synchronization acquisition method capable of acquiring synchronization with high performance.

  The wireless communication apparatus of the present invention receives a communication signal transmitted by repeating a fixed pattern having a known N symbol length (N is an integer of 1 or more) A times (A is an integer of 1 or more) and performs demodulation processing. A wireless communication apparatus having a receiving unit, a complex correlation value calculating means for calculating a complex correlation value between a received signal of the communication signal and a fixed pattern having an N symbol length, and an A symbol separated by N symbols of the complex correlation value An adding means for adding a plurality of values; a peak position detecting means for detecting a maximum peak position of the complex correlation value and a maximum peak position of the next point; and a maximum peak position and a maximum peak position of the next point, respectively. On the other hand, a difference means for calculating a difference between addition results of peak positions separated by N symbols before and after, a difference between addition results before and after the maximum peak position, and an addition before and after the maximum peak position of the next point. Comparing means for comparing the difference between the results, and a synchronization position determining means for adopting the smaller difference as the true maximum peak position based on the comparison result and determining the synchronization position based on the maximum peak position, It is to be prepared.

  With the above configuration, erroneous determination of the maximum peak position of the complex correlation value addition result can be reduced, so that synchronization can be obtained with good performance even when there is a pattern similar to a fixed pattern before and after or when the CNR is small. It becomes possible.

  The wireless communication system of the present invention includes a first wireless communication having a transmission unit that repeatedly transmits a fixed pattern having a known N symbol length (N is an integer of 1 or more) A times (A is an integer of 1 or more). The apparatus and the second wireless communication apparatus using the wireless communication apparatus are included in the configuration.

  With the above configuration, it is possible to construct a radio communication system with good reception performance as a whole system.

  The synchronization acquisition method of the present invention receives a communication signal transmitted by repeating a fixed pattern having a known N symbol length (N is an integer of 1 or more) A times (A is an integer of 1 or more), and performs demodulation processing. A synchronization acquisition method in a wireless communication apparatus having a receiving unit, wherein a complex correlation value calculating step of calculating a complex correlation value between a received signal of the communication signal and a fixed pattern of the N symbol length, and N of the complex correlation value An addition step of adding A values apart from the symbol, a peak position detection step of detecting a maximum peak position and a maximum peak position of the next point of the addition result of the complex correlation values, and a maximum of the maximum peak position and the next point For each peak position, a difference step for calculating a difference between addition results between peak positions separated by N symbols before and after, a difference between addition results before and after the maximum peak position, and The comparison step for comparing the difference of the addition result before and after the maximum peak position of the point, and the smaller difference is adopted as the true maximum peak position based on the comparison result, and the synchronization position is determined based on the maximum peak position. And a synchronization position determination step for determining.

  As a result, when using the repeated fixed pattern of the preamble section in the synchronization acquisition of the wireless receiver, the synchronization acquisition can be performed with good performance even when there are patterns similar to the fixed pattern before and after or when the CNR is small. It becomes possible.

  According to the present invention, when a repeated fixed pattern of a preamble section is used for synchronization acquisition of a wireless receiver, synchronization acquisition is performed with good performance even when there are patterns similar to the fixed pattern before and after or when the CNR is small. A wireless communication apparatus and a synchronization acquisition method that can be performed can be provided.

  FIG. 1 is a block diagram showing a configuration of a main part of a wireless communication apparatus according to an embodiment of the present invention. First, the transmission system of the wireless communication device will be described. The wireless communication apparatus according to the present embodiment includes a waveform generator 101, a root Nyquist filter (RNF) 102, a D / A converter 103, a quadrature modulator 104, a mixer 105, an amplifier 106, a duplexer 107, and transmission / reception as a transmission system. An antenna 108 is provided.

  In this transmission system, the transmission bit string U is input to the waveform generator 101, and control data is added to generate modulation data for transmission that becomes a communication signal. The modulated data is subjected to baseband band limitation by the root Nyquist filter 102 and then input to the D / A converter 103, where the modulated data is converted from a digital signal to an analog signal. Further, in the quadrature modulator 104, the transmission signal converted into the analog signal is quadrature modulated.

  The transmission signal orthogonally modulated by the orthogonal modulator 104 is up-converted to a radio frequency by a mixer 105 that converts it to a predetermined transmission frequency, and the up-converted signal is amplified by an amplifier 106. The amplified transmission signal is output to the transmission / reception shared antenna 108 via the duplexer 107 that branches the transmission / reception signal, and is transmitted from the transmission / reception shared antenna 108 as a radio signal (communication signal).

  Next, a reception system of the wireless communication device will be described. The wireless communication apparatus according to the present embodiment includes, as a reception system, a transmission / reception shared antenna 108, a duplexer 107, a mixer 109, an orthogonal demodulator 110, an A / D converter 111, a root Nyquist filter (RNF) 112, a synchronization unit 113, and a frequency. An offset amount estimator 114 and a demodulator 115 are provided.

  In this reception system, a reception signal (communication signal) received by the transmission / reception shared antenna 108 is input to the mixer 109 via the duplexer 107, down-converted to a baseband frequency by the mixer 109, and further by the orthogonal demodulator 110. Quadrature demodulated.

  The quadrature demodulated received signal is converted from an analog signal to a digital signal by the A / D converter 111, band-limited by the root Nyquist filter 112, and then sent to the synchronization unit 113, the frequency offset amount estimator 114 and the demodulator 115. Entered.

  The synchronization unit 113 uses the digital signal to execute a process according to a synchronization acquisition method of the present embodiment described later to acquire synchronization, and the symbol timing signal is input to the frequency offset amount estimator 114 and the demodulator 115. The The frequency offset amount estimator 114 estimates a transmission / reception frequency offset amount. Based on this estimated frequency offset amount, the input phase to the root Nyquist filter 112 is corrected.

  As the demodulator 115, a waveform equalizer that compensates for frequency selective fading and a detector corresponding to the modulation method are used. The demodulator 115 performs demodulation processing using the output signal of the root Nyquist filter 112 and the symbol timing signal from the synchronization unit 113 and outputs a received bit string D.

Next, the synchronization acquisition process in the synchronization unit 113 will be described in detail. Here, as in the conventional example of the background art described above, the transmission-side radio communication apparatus transmits a communication signal in the transmission frame format shown in FIG. 8, and the reception-side radio communication apparatus as shown in FIG. This shows a case where a sample sequence of 5 repeated fixed patterns (FP _{0 to} FP ₄ ) (the number of repeated fixed patterns R = 5) is received. That is, here, a process in which a fixed pattern of N symbol length (N is an integer of 1 or more) is repeatedly transmitted A times (A is an integer of 1 or more and A = 5) and this communication signal is received will be described. .

In FIG. 9, (a) shows a transmission frame format, (b) shows a received sample sequence, and (c) shows a complex conjugate of a repetitive fixed pattern. S _x in (b) is a received sample string (symbol time interval) of the x sample of the repetitive fixed pattern. In (c), F _x ^* is a complex conjugate (symbol time interval) of a repetitive fixed pattern.

FIG. 2 is a flowchart showing a synchronization acquisition processing procedure in the synchronization unit according to the embodiment of the present invention. The received sample sequence of received signals is also input to the synchronization unit 113, where synchronization of the reception unit is acquired. First, the synchronization unit 113 sequentially inputs the received sample sequence (step S31). The synchronization unit 113 calculates the complex correlation values corr _i and repeating fixed pattern of the received sample sequence and N symbol length (step S32). Next, using the complex correlation value corr _i , the synchronization unit 113 adds A complex correlation values (here, five) separated by N symbol intervals to calculate the sum thereof (step S33).

  At this time, as shown in FIG. 12, the data before and after the repetitive fixed pattern (in this case) is the same as the repetitive fixed pattern (the complex correlation value with the repetitive fixed pattern becomes large). Data) is considered.

In this case, the complex correlation value corri _i between the received sample sequence and the fixed pattern shown in FIG. 9 is as shown in FIG. 3, and the complex correlation value 5 separated by N symbols is calculated based on the complex correlation value corri _i. The sum of the pieces is as shown in FIG. However, an ideal state in the absence of thermal noise is shown here.

  In this embodiment, the maximum peak position at the position where i = 0 and the maximum peak position at the next position at the position where i = N are also candidates for the maximum peak position for determining the synchronization position. Therefore, the synchronization unit 113 detects the maximum peak position of this value and the maximum peak position of the next point using the addition result of five complex correlation values separated by N symbols (step S34). Then, for each of the maximum peak position (i = 0 position) and the next maximum peak position (i = N position), a difference between values of peak positions separated by N symbols before and after is calculated.

That is, the synchronization unit 113 first calculates the difference between the addition result values of the peak positions that are N symbols away from each other before and after the maximum peak position (position where i = 0) (step S35). At this time, with respect to the position of i = 0, the difference between the addition result corr5− _{N of} 5 complex correlation values at the position of i = _−N and the addition result corr5N of 5 complex correlation values at the position of i = N The diffA is calculated as the following formula 3.

Also, a difference between the addition result values of peak positions separated by N symbols before and after the maximum peak position of the next point (i = N position) is calculated (step S36). At this time, for the position i = N, the difference diffB between the addition result corr50 of 5 complex correlation values at the position i = ₀ and the addition result corr52 _2N of the 5 complex correlation values at the position i = 2N is The following equation 4 is calculated.

  Next, the synchronization unit 113 compares the difference diffA before and after the maximum peak position with the difference diffB before and after the maximum peak position of the next point (step S37). Then, based on the comparison result, the synchronization unit 113 determines the synchronization position based on either the maximum peak position or the next maximum peak position (step S38).

  At this time, based on the comparison result of the difference, the peak position from which the smaller difference is calculated is adopted as the true maximum peak position. That is, if diffA ≦ diffB, the position of i = 0 is adopted as the true maximum peak position and is set as a reference position for determining the synchronization position. On the other hand, if diffA> diffB, the position of i = N is adopted as the true maximum peak position and is set as a reference position for determining the synchronization position.

  Here, for easy understanding, the peak value of the complex correlation value shown in FIG. 5 is a diagram showing an example in which the peak value of the complex correlation value in FIG. 3 is digitized. FIG. 6 is a numerical example of the sum of five complex correlation values separated by N symbols calculated based on the complex correlation value in FIG. FIG. In the example of FIG. 5, the peak value of the complex correlation value between the received sample and the fixed pattern is set to 10, and the complex correlation value between the information data whose data pattern is similar to the fixed pattern and the fixed pattern is set to 8. The sum of the five complex correlation values separated by N symbols at this time (corresponding to FIG. 4) is digitized as shown in FIG. This numerical example is applied to the synchronization acquisition process.

First, regarding the maximum peak position of corr5 _i in FIG. 6 (i = 0 position), the difference diffA between the addition result values of the peak positions separated by the preceding and following N symbols is calculated as shown in Equation 5 below.

Further, for the maximum peak position of the next point of corr5 _i in FIG. 6 (i = N position), the difference diffB of the addition result values between the peak positions separated by the preceding and following N symbols is calculated as shown in the following Expression 6. Become.

  In this case, when the difference between the two is compared, diffA <diffB, and therefore, the position of i = 0 is selected as the maximum peak position, and the synchronization position is determined based on this position.

  In the above example, the numerical value when the CNR is large and the reception state is good is illustrated. However, when the CNR is small, the probability that the maximum peak value and the maximum peak value of the next point in FIG. Therefore, the synchronization acquisition method of this embodiment exhibits a great effect.

  As described above, in this embodiment, when performing transmission / reception using a repetitive fixed pattern and acquiring synchronization, complex correlation is performed based on a complex correlation value between a repetitive fixed pattern on the transmission side and a received symbol on the reception side. Rather than determining the synchronization position only from the maximum peak position of the addition result of A values separated by N symbols of the value, in addition to the maximum peak position, the maximum peak position of the next point is once entered as a synchronization position candidate, and For each of the maximum peak position and the maximum peak position of the next point, the synchronization position is determined in consideration of the complex correlation value of the peak positions separated by N symbols before and after. For this reason, it becomes resistant to thermal noise, and synchronization can be acquired with good performance even when the CNR is small. In particular, when the data before and after the repeated fixed pattern in the preamble section becomes data similar to the repeated pattern, the probability of erroneously selecting the maximum peak position is greatly reduced, and a great improvement effect is obtained.

  Therefore, by using the synchronization acquisition method of the present embodiment, it is possible to perform synchronization acquisition with higher performance even under conditions where the thermal noise is large and the CNR is small. In addition, when the synchronization acquisition method of the present embodiment is applied to a wireless communication device, it can be realized with an extremely small amount of calculation and an increase in circuit scale as compared with the conventional example.

  As described above, according to the wireless communication device of the present embodiment, by applying the above-described synchronization acquisition method in the synchronization unit 113, good synchronization acquisition can be performed even when the CNR is small. A wireless communication apparatus having good reception performance can be realized.

  FIG. 7 is a diagram showing a configuration of a wireless communication system using the wireless communication apparatus according to the embodiment of the present invention. The wireless communication system includes a wireless communication device BS of a base station and a wireless communication device of a mobile station or a fixed station used for a wireless LAN according to the IEEE802.11a / g standard, a municipal digital broadcast communication system according to ARIB-STD-T86, and the like. RS1, RS2,..., RSm. In this wireless communication device RS1, RS2,..., RSm, the wireless communication device of the present embodiment shown in FIG. be able to.

  Note that this embodiment can be widely applied to a wireless communication apparatus of a digital wireless communication system having a transmission format in which a known fixed pattern is repeatedly transmitted. For example, high-performance synchronization can be obtained by applying the above-described wireless communication apparatus of the present embodiment to a wireless LAN such as the IEEE802.11a / g standard or the municipal digital broadcast communication system of ARIB-STD-T86. Thus, reception performance in the wireless communication system can be improved.

  As described above, according to the present embodiment, when a repeated fixed pattern of a preamble section is used in a wireless communication apparatus for acquisition of synchronization of a receiving unit, a pattern similar to a fixed pattern exists before and after the pattern, Even when the CNR is small, synchronization can be acquired with good performance.

  The present invention performs synchronization acquisition with good performance even when there is a pattern similar to the fixed pattern before and after or when the CNR is small when using the repeated fixed pattern in the preamble section in the synchronization acquisition of the radio receiver. And is useful for a wireless communication apparatus and a synchronization acquisition method used in a wireless communication system such as a digital cellular phone and a wireless LAN.

The block diagram which shows the structure of the principal part of the radio | wireless communication apparatus which concerns on embodiment of this invention. The flowchart which shows the synchronization acquisition process procedure in the synchronization part which concerns on embodiment of this invention. The figure which shows the example of the calculated complex correlation value in this embodiment The figure which shows the example of the sum of five complex correlation values of the N symbol distance calculated based on the complex correlation value of FIG. The figure which shows the example which digitized the peak value of the complex correlation value of FIG. The figure which shows the numerical example of the sum (corresponding to FIG. 4) of five complex correlation values separated by N symbols calculated based on the complex correlation value of FIG. The figure which shows the structure of the radio | wireless communications system using the radio | wireless communication apparatus which concerns on embodiment of this invention. The figure which shows the example of the transmission frame format which has the repetition fixed pattern used for radio | wireless communication The figure which shows the example of the reception sample sequence of the repetition fixed pattern in a prior art example The figure which shows the complex correlation value calculated in the example of FIG. The figure which shows the example of the sum of five complex correlation values of the N symbol distance calculated based on the complex correlation value of FIG. The figure which shows an example of the transmission signal in which the data behind the repetition fixed pattern became the same data as the repetition pattern The figure which shows the complex correlation value calculated in the example of FIG. The figure which shows the example of the sum of five complex correlation values of the N symbol distance calculated based on the complex correlation value of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Waveform generator 102 Root Nyquist filter 103 D / A converter 104 Quadrature modulator 105 Mixer 106 Amplifier 107 Duplexer 108 Transmission / reception shared antenna 109 Mixer 110 Quadrature demodulator 111 A / D converter 112 Root Nyquist filter 113 Synchronizer 114 Frequency Offset amount estimator 115 Demodulator

Claims (3)

A wireless communication apparatus having a receiving unit that receives a communication signal transmitted by repeating a fixed pattern of a known N symbol length (N is an integer of 1 or more) A times (A is an integer of 1 or more) and performs demodulation processing. There,
Complex correlation value calculating means for calculating a complex correlation value between the received signal of the communication signal and the fixed pattern of the N symbol length;
Adding means for adding A values N symbols apart of the complex correlation value;
Peak position detection means for detecting the maximum peak position of the addition result of the complex correlation value and the maximum peak position of the next point;
A difference means for calculating a difference between addition results of peak positions separated by N symbols before and after the maximum peak position and the next maximum peak position;
Comparison means for comparing the difference between the addition results before and after the maximum peak position and the difference between the addition results before and after the maximum peak position of the next point;
Based on the comparison result, adopting the smaller difference as the true maximum peak position, the synchronization position determination means for determining the synchronization position based on the maximum peak position,
A wireless communication device comprising: A first wireless communication apparatus having a transmitter that repeatedly transmits a fixed pattern of a known N symbol length (N is an integer of 1 or more) A times (A is an integer of 1 or more);
A wireless communication system including, in its configuration, a second wireless communication device using the wireless communication device according to claim 1. In a wireless communication apparatus having a receiving unit that receives a communication signal transmitted by repeating a fixed pattern of a known N symbol length (N is an integer of 1 or more) A times (A is an integer of 1 or more) and performs demodulation processing A synchronization acquisition method,
A complex correlation value calculating step of calculating a complex correlation value between the received signal of the communication signal and the fixed pattern of the N symbol length;
An adding step of adding A values N symbols apart of the complex correlation value;
A peak position detecting step for detecting the maximum peak position of the addition result of the complex correlation value and the maximum peak position of the next point;
A difference step for calculating a difference between addition results of peak positions separated by N symbols before and after each of the maximum peak position and the next maximum peak position;
A comparison step for comparing the difference between the addition results before and after the maximum peak position and the difference between the addition results before and after the maximum peak position of the next point;
Based on the comparison result, the one having a smaller difference is adopted as a true maximum peak position, and a synchronization position determining step for determining a synchronization position based on the maximum peak position;
A synchronization acquisition method comprising:

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