JP2013098962A - Receiving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiving device capable of preventing generation of reception errors caused by wrong synchronization even in disturbing wave interference reception, and of stabilizing a wireless communication quality.SOLUTION: A receiving device has a symbol synchronization circuit 1. In the symbol synchronization circuit 1, a synchronization processing part 7 that received peak position information detected by a peak position detector 6 as synchronization position information, outputs a synchronization state that indicates a synchronization maintaining state or a non-synchronization state. A D-power/I-power calculation part 8 acquires a power (D-power) value at reception in the synchronization maintaining state, and acquires a power (I-power) value at non-reception in the non-synchronization state. A maximum gain value calculation part 9 calculates a maximum gain value on the basis of those power values. A gain value calculation part 3 calculates a gain value from the reception power value, compares it with the maximum gain value inputted from the maximum gain value calculation part 9, selects a smaller gain value, and performs control of an AGC 4 at the gain value.

Description

  The present invention relates to a receiving apparatus, and more particularly, to a receiving apparatus that can stably detect symbol synchronization timing even when a received OFDM signal includes an interference wave.

[Conventional technology]
A CP (Cyclic Prefix) guard section is provided as a synchronization method in a conventional OFDM (Orthogonal Frequency Division Multiplexing) receiver, and auto-correlation is performed using the CP to detect the timing of symbol synchronization. Are known.

[Transmission frame: Fig. 3]
A general transmission frame in the OFDM signal will be described with reference to FIG. FIG. 3 is a general transmission frame configuration diagram.
For transmission, frame transmission as shown in FIG. 3 is performed intermittently by burst transmission from the transmission station. At the beginning, a known preamble pattern for mainly performing symbol synchronization, AGC (Auto Gain Control), and AFC (Auto Frequency Control) processing is periodically transmitted continuously in several symbols (5 symbols in the example of FIG. 3).

A plurality of data symbols (Data No. 1 to No. L) for transmitting transmission information continuously after the preamble pattern are transmitted at a symbol period.
After the transmission is completed, there is a non-transmission section, and the transmission signal having the frame structure is intermittently transmitted in response to a transmission request.

[Symbol Synchronization Circuit of Conventional OFDM Receiver: FIG. 4]
Next, the configuration of the symbol synchronization circuit of the conventional OFDM receiver will be described with reference to FIG. FIG. 4 is a configuration block diagram of a symbol synchronization circuit of a conventional OFDM receiver.
As shown in FIG. 4, the symbol synchronization circuit 20 of the conventional OFDM receiver is configured to realize a conventional symbol synchronization method based on CP correlation, and includes a received power calculation unit 21 that calculates a received power value Rxp from a received signal. A gain value calculation unit 22 that calculates the gain value Ga from the received power value, a gain control unit (AGC) 23 that controls the gain according to the calculated gain value, and a CP correlation unit that performs CP correlation processing by autocorrelation 24, a peak position detection unit 25 for detecting a peak position from the CP correlation, and a synchronization processing unit 26 for performing a synchronization process.

  In particular, the synchronization processing unit 26 receives I-phase and Q-phase received signals, receives a gain-controlled signal (normalized signal) from the AGC 23, and receives peak position information from the peak position detection unit 25. Is extracted as synchronization position information, and an FFT (Fast Fourier Transform) section is extracted from the AGC signal by the synchronization position information and output to the FFT processing unit.

The operation of the conventional symbol synchronization circuit will be described.
In the AGC 23, processing operations such as equations (1) and (2) are performed.
Receiving signals I, Q and Rx, received power value = Rx _P, the gain value = Ga, When received amplitude = _{N P} as a reference,
Ga = N _P / √ (Rx _P ) (1)
Received signal after AGC = Ga · Rx (2)

Received signal after AGC is a signal average amplitude is normalized to _{N P} by AGC 23.
CP correlation is performed by the CP correlator 24 from the received signal after AGC, and the peak position having the maximum amplitude in one symbol section is detected by the peak position detector 25 to obtain a symbol synchronization position. Output.
The received signal after AGC is subjected to demodulation processing by cutting out the FFT interval by the synchronization processing unit 26 and outputting the result to the FFT.

[Conventional reception power and CP correlation power after AGC under interference wave reception environment: FIG. 5]
Next, conventional received power and CP correlation power after AGC in an interference wave reception environment will be described with reference to FIG. FIG. 5 is a signal waveform diagram showing received power at the time of interference wave mixing and CP correlation power after AGC.
Upper part of FIG. 5 shows the received power value Rx _P, lower showed a CP correlation power was autocorrelation on the received signal after AGC.

  In the received signal Rx, it is assumed that an interference wave signal (tone signal, interference signal power = transmission frame signal average power−6 dB) is mixed in the transmission frame signal. When attention is paid to the non-transmission (interference wave only) section, although the reception power at the upper stage is low, the CP correlation power at the lower stage shows a higher value than when receiving a frame signal.

This is because an unmodulated tone signal is used as an interfering wave, and a signal that is one symbol interval away has a high correlation characteristic, so the autocorrelation is almost “1”.
Therefore, particularly when receiving interference waves in a narrow band, with the conventional synchronization method, even when there is no transmission (only interference waves), it is determined that there is a peak due to high correlation, and there is a possibility that false synchronization occurs.

[Related technologies]
In addition, there exists Unexamined-Japanese-Patent No. 2008-109450 [patent document 1] as a related prior art.
In Patent Document 1, in the frame synchronization method of the OFDM communication system, the correlation calculation in the symbol is performed using the autocorrelation element included in each OFDM symbol to obtain the synchronization timing for each OFDM symbol, and It is shown that the broadcast channel timing is obtained by executing the correlation calculation, and the broadcast channel is decoded based on the timing with the highest degree of correlation obtained by the unique symbol correlation search.

JP 2008-109450 A

  As described above, the conventional synchronization method in the symbol synchronization circuit of the OFDM receiver has a problem that even if there is no transmission (only the interference wave), it is determined as a peak due to high correlation, and erroneous synchronization occurs. It was.

  The present invention has been made in view of the above circumstances. When a high-level interference signal is included in the band of the received signal, an interference signal (for example, a tone signal) having high autocorrelation is mixed especially in one symbol section. Even in such a case, an object is to provide a receiving device that does not cause false synchronization and obtains high synchronization performance.

  The present invention for solving the problems of the conventional example described above is a D power / I power calculation for calculating D power which is a power value at the time of reception and I power which is a power value at the time of non-reception in the receiving apparatus. A maximum gain value calculation unit that calculates a maximum gain value based on the power value calculated by the D power / I power calculation unit, a received power calculation unit that calculates a received power value from the received signal, and a received power calculation The gain value is calculated from the received power value input from the input unit, the maximum gain value input from the maximum gain value calculation unit is input, both gain values are compared, and the smaller value is output as the gain value. And a gain control unit that performs automatic gain control of the received signal with the gain value from the gain value calculation unit.

  The present invention provides a correlation unit that performs autocorrelation processing on a received signal whose gain is controlled by a gain control unit, and a peak position detection that detects a peak position based on correlation in the correlation unit and outputs synchronization position information. And a synchronization processing unit that performs synchronization processing on the reception signal gain-controlled by the gain control unit based on the synchronization position information and outputs synchronization state information to the D power / I power calculation unit, The power / I power calculation unit calculates a power value in the synchronization maintaining state as D power and a power value in the unsynchronized state as I power based on the synchronization state information.

  The present invention is characterized in that, in the receiving apparatus, the maximum gain value calculation unit calculates a maximum gain value based on a power value between D power and I power.

  According to the present invention, the D power / I power calculation unit calculates the D power that is the power value at the time of reception and the I power that is the power value at the time of non-reception, and the maximum gain value calculation unit calculates the D power -The maximum gain value is calculated based on the power value calculated by the I power calculation unit, the received power calculation unit calculates the received power value from the received signal, and the gain value calculation unit is input from the received power calculation unit. The gain value is calculated from the received power value, the maximum gain value input from the maximum gain value calculation unit is input, both gain values are compared, the smaller one is output as the gain value, and the gain control unit Since it is a receiving device that performs automatic gain control of the received signal with the gain value from the value calculation unit, it is possible to prevent the occurrence of reception errors due to mis-synchronization and stabilize the wireless communication quality even when receiving interference interference is there.

It is a block diagram of the configuration of a symbol synchronization circuit of an OFDM receiver according to an embodiment of the present invention. It is a signal waveform diagram which shows the reception power after AGC and the CP correlation power after AGC according to the embodiment. It is a general transmission frame structural example figure. It is a configuration block diagram of a symbol synchronization circuit of a conventional OFDM receiver. It is a signal waveform diagram which shows the reception power at the time of mixing of an interference wave, and CP correlation power after AGC.

Embodiments of the present invention will be described with reference to the drawings.
[Outline of the embodiment]
In the symbol synchronization method in the OFDM receiver according to the embodiment of the present invention, the synchronization processing unit outputs the synchronization state of the synchronization maintaining state or the unsynchronized state using the peak position information detected by the peak position detection unit as the synchronization position information. The D power / I power calculation unit obtains the power (D power) value at the time of reception in the synchronization maintaining state and the power (I power) value at the time of non-reception in the unsynchronized state, and the maximum gain value calculation unit The gain value calculation unit calculates the gain value from the received power value and compares it with the maximum gain value input from the maximum gain value calculation unit. The value is selected, and the gain is controlled to limit the maximum AGC amplification amount. Even when interference interference is received, the occurrence of reception errors due to mis-synchronization is prevented, and wireless communication quality is stabilized. Can be It is intended.

[Symbol Synchronization Circuit of OFDM Receiver According to Embodiment: FIG. 1]
A symbol synchronization circuit (present symbol synchronization circuit) of an OFDM receiver according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration block diagram of a symbol synchronization circuit of an OFDM receiver according to an embodiment of the present invention.
As shown in FIG. 1, the symbol synchronization circuit 1 includes a received power calculation unit 2, a gain value calculation unit 3, a gain control unit (AGC) 4, a CP correlation unit 5, a peak position detection unit 6, A synchronization processing unit 7, a D power / I power calculation unit 8, and a maximum gain value calculation unit 9 are provided.

[Each part of the symbol synchronization circuit: FIG. 1]
Each part of the symbol synchronization circuit will be specifically described.
It received power calculation section 2, the received signal I, calculates a received power value Rx _P from Q, and outputs the gain value calculator 3 and D power · I power calculation unit 8.

Gain value calculating unit 3 calculates the gain value from the reception power value Rx _P, compared with the maximum gain value MaxG input from the maximum gain value calculating unit 9, and outputs the AGC4 a smaller value as the gain value Ga . In particular, the gain value calculation unit 3 has a function of limiting the maximum value of the gain value Ga using the maximum gain value MaxG.
The gain control unit (AGC) 4 controls the gains of the reception signals I and Q according to the gain value Ga input from the gain value calculation unit 3, and the reception is gain-controlled by the CP correlation unit 5 and the synchronization processing unit 7. Output a signal.

The CP correlation unit 5 performs CP correlation processing by autocorrelation on the received signal from the AGC 4 and outputs a correlation value to the peak detection unit 6.
The peak position detection unit 6 detects the peak position based on the correlation value from the CP correlation unit 5 and outputs the peak position to the synchronization processing unit 7 as synchronization position information.

The synchronization processing unit 7 inputs a gain-controlled signal (normalized signal) from the AGC 4, inputs synchronization position information from the peak position detection unit 6, and performs an FFT interval on the signal after AGC according to the synchronization position information Is cut out and output to FFT.
Further, since the synchronization processing unit 7 can determine whether the synchronization state is the synchronization maintenance state or the unsynchronization state based on the input of the synchronization position information from the peak position detection unit 6. The synchronization state information is output to the D power / I power calculation unit 8.

D Power · I power calculation unit 8, D power value (the power value at the time of reception) and I power value (the power value at the time of non-reception) is calculated based on the received power value Rx _P from the reception power calculation section 2, Output to the maximum gain value calculation unit 9. Specific calculation processing in the D power / I power calculation unit 8 will be described later.
The maximum gain value calculation unit 9 calculates the maximum gain value MaxG based on the D power value and the I power value from the D power / I power calculation unit 8 and outputs the maximum gain value MaxG to the gain value calculation unit 3. Specific calculation processing in the maximum gain value calculation unit 9 will be described later.

[Operation of this symbol synchronization circuit]
[Processing of D power / I power calculation unit 8]
D Power · I power calculation unit 8, the received power value Rx _P, enter a synchronization state information from the synchronization processing unit 7 performs averaging of the following power values.
[When synchronization is maintained]
When the synchronization state information of the synchronization maintenance state (Preamble or Data symbol reception) is the received power value Rx _P determines that the frame received power, the input of the D power averaging to obtain a D power value.
[When not synchronized]
When the synchronization state information of the unsynchronized state (frame non-transmission) is the received power value Rx _P determines that the disturbance power, and the input of the I power averaging to obtain an I power value.

[Process of maximum gain value calculation 9]
The maximum gain value calculation 9 calculates a maximum gain value MaxG from the D power value and the I power value, and outputs it to the gain value calculation unit 3. A calculation example of the maximum gain value MaxG is as follows. IP is the I power value, and DP is the D power value.
M power value = D power * 10 ^{(log (IP) −log (DP)) * 0.4} (3)
MaxG = N _P / √ (M power value) (4)

  The idea of setting the M power value is to obtain a value that satisfies I power value <M power value <D power value (precondition: I power value <D power value). ) It may be other than the formula. That is, the maximum gain value is set based on the power (M power value) between the I power value and the D power value.

[Processing of gain value calculation unit 3]
After calculating Ga = N _P / √ (Rx _P ) in equation (1), the gain value calculation unit 3 selects the smaller one for comparison between Ga and MaxG (suppresses the gain), and sets the gain value Ga to the AGC 4. Output.

[Received power after AGC and CP correlation power after AGC according to the embodiment: FIG. 2]
Next, reception power after AGC and CP correlation power after AGC according to the present embodiment will be described with reference to FIG. FIG. 2 is a signal waveform diagram showing reception power after AGC and CP correlation power after AGC according to the embodiment.
As shown in FIG. 2, it is possible to suppress the CP correlation power at the time of no transmission in the lower stage by suppressing the gain of the interference power at the time of no transmission as in the upper stage, and the problem of false synchronization in the peak position detection unit 6 Can be improved.

[Effect of the embodiment]
According to this OFDM receiver, the maximum gain value that differs depending on whether the synchronization state is the synchronization maintaining state (during reception) or the non-synchronization state (not receiving (when not receiving)) is calculated, and the maximum gain value and reception are calculated. A gain value calculated from the power value is compared, AGC control is performed with the smaller gain value, and a symbol synchronization circuit that performs synchronization processing using the AGC-controlled received signal is provided. Even when receiving interference, it is possible to prevent the occurrence of a reception error due to erroneous synchronization and stabilize the wireless communication quality.

  The present invention is suitable for a receiving apparatus that can prevent occurrence of a reception error due to erroneous synchronization and stabilize wireless communication quality even when receiving interference interference.

  DESCRIPTION OF SYMBOLS 1 ... Symbol synchronous circuit, 2 ... Receive power calculation part, 3 ... Gain value calculation part, 4 ... Gain control part (AGC), 5 ... CP correlation part, 6 ... Peak Position detection unit, 7 ... Synchronization processing unit, 8 ... D power / I power calculation unit, 9 ... Maximum gain value calculation unit, 20 ... Symbol synchronization circuit, 21 ... Received power calculation unit 22 ... Gain value calculation unit, 23 ... Gain control unit (AGC), 24 ... CP correlation unit, 25 ... Peak position detection unit, 26 ... Synchronization processing unit, 30 ... ,

Claims (3)

A D power / I power calculation unit that calculates D power that is a power value at the time of reception and I power that is a power value at the time of non-reception;
A maximum gain value calculation unit that calculates a maximum gain value based on the power value calculated by the D power / I power calculation unit;
A received power calculation unit for calculating a received power value from a received signal;
The gain value is calculated from the received power value input from the received power calculation unit, the maximum gain value input from the maximum gain value calculation unit is input, both gain values are compared, and the smaller one is used as the gain value. A gain value calculator to output;
And a gain control unit that performs automatic gain control of the received signal with the gain value from the gain value calculation unit. A correlation unit that performs autocorrelation processing on the received signal gain-controlled by the gain control unit;
A peak position detection unit that detects a peak position by correlation in the correlation unit and outputs synchronization position information;
A synchronization processing unit that performs synchronization processing based on the synchronization position information for the reception signal gain-controlled by the gain control unit, and outputs synchronization state information to the D power / I power calculation unit,
The D power / I power calculation unit calculates a power value in a synchronization maintaining state as D power and a power value in an unsynchronized state as I power based on the synchronization state information. Item 4. The receiving device according to Item 1.   The receiving apparatus according to claim 1, wherein the maximum gain value calculation unit calculates a maximum gain value based on a power value between the D power and the I power.

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