JP4440141B2 - Receiving machine - Google Patents

Description

  The present invention relates to a receiving-side communication apparatus (hereinafter referred to as a receiver) provided with an adaptive equalizer, and more particularly to a receiver that estimates a frequency error using a signal after adaptive equalization processing. It is.

  Hereinafter, a conventional receiver including an adaptive equalizer will be described. In wireless communication or the like, there is adaptive equalization processing as a technique that can cope with the case where the influence of delay waves or the like cannot be ignored and intersymbol interference occurs. In particular, it is important to remove the frequency error in order to stably execute the operation of the adaptive equalizer.

  A specific example of a conventional receiver including an adaptive equalizer is a receiver described in Non-Patent Document 1 below. Here, the operation of the conventional receiver will be briefly described. First, in the receiver, the transmission path characteristic is estimated using the received signal that has received the intersymbol interference. A predetermined sequence called a synchronization word is inserted in the received signal, and the channel characteristics are estimated using this known sequence.

  The received signal is also input to an MF (matched filter) circuit in the receiver. The MF circuit is a transversal filter having tap coefficients obtained by taking complex conjugates by reversing the transmission path characteristics in terms of time, and maximizing the SN ratio at the sampling point (interference caused by intersymbol interference is side effects). Remains as a lobe). In this receiver, frequency error elimination is performed by approximating that no side lobe caused by intersymbol interference occurs in the MF circuit output. That is, the frequency error is estimated after removing the modulation component of the MF circuit output by the multiplication circuit, and the frequency error is removed using this estimated value.

  The receiver performs predetermined adaptive equalization processing and demodulation processing on the signal from which the frequency error has been removed, and finally outputs a demodulated signal. As described above, in the conventional receiver, adaptive equalization processing and demodulation processing are performed using transmission path characteristics estimated before removing the frequency error.

Okanoue et al., “Configuration of MLSE receiver with frequency offset correction function in TDMA digital mobile communication”, IEICE Transactions B, pp.736-744, 1990

However, the receiver described in Non-Patent Document 1 has the following problems.
(1) Since interference due to intersymbol interference remains in the signal for estimating the frequency error, the frequency estimation accuracy decreases.
(2) Since the transmission path characteristic used for adaptive equalization is the transmission path characteristic estimated before removing the frequency error, the operation characteristic of adaptive equalization deteriorates.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a receiver that can realize higher frequency estimation accuracy and obtain better operational characteristics of adaptive equalization.

  In order to solve the above-described problems and achieve the object, a receiver according to the present invention is a receiver in wireless communication, and performs a predetermined adaptive equalization process using a known sequence included in a received signal. Based on the first adaptive equalization means, the first frequency error estimation means for estimating the frequency error from the output of the first adaptive equalization means, and the frequency error estimation value by the first frequency error estimation means, First frequency error correction means for performing frequency correction on the received signal, and second adaptive equalization for performing predetermined adaptive equalization processing on the frequency error correction value by the first frequency error correction means Means, and demodulation means for demodulating the output of the second adaptive equalization means.

  According to the present invention, the frequency error is estimated using the signal in which the intersymbol interference component is suppressed. In addition, the signal after frequency error removal is used for adaptive equalization.

  According to the present invention, since the frequency error is estimated using the signal in which the intersymbol interference component is suppressed, there is an effect that higher frequency estimation accuracy can be realized. In addition, since the transmission path characteristic used for adaptive equalization is the transmission path characteristic after frequency error removal, it is possible to obtain better adaptive equalization operation characteristics.

  Embodiments of a communication apparatus (hereinafter referred to as a receiver) according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a receiver according to the present invention. This receiver has a frequency error correction block 6 comprising an adaptive equalization circuit 3, a frequency error estimation circuit 4, and a frequency error correction circuit 5. And an adaptive equalization circuit 7 and a demodulation circuit 8.

  The receiver receives a reception signal subjected to intersymbol interference from the reception signal input terminal 1, and the adaptive equalization circuit 3 performs a known equalization process on the received reception signal. Further, the frequency error estimation circuit 4 estimates the frequency error using the adaptive equalization output. Then, the frequency error correction circuit 5 corrects the frequency error of the received signal using the frequency error estimated value. These blocks of the adaptive equalization circuit 3, the frequency error estimation circuit 4, and the frequency error correction circuit 5 are referred to as a frequency error correction block 6.

  Here, the operations of the adaptive equalization circuit 3 and the frequency error estimation circuit 4 will be described in more detail. As shown in FIG. 2, a predetermined sequence called a synchronization word (known sequence) is inserted in the received signal, and the adaptive equalization circuit 3 estimates an equalization parameter using this known sequence, Perform adaptive equalization processing. The adaptive equalization output is a signal from which intersymbol interference is removed. Then, the frequency error estimation circuit 4 uses this adaptive equalization output, for example, H. Kubo et al. “A multiple open-loop frequency estimation based on differential detection for MPSK” IEICE Transactions on Communications, pp. 136-144, As described in 1999, this is performed by performing delay detection on the multiplied signal. Also, as shown in FIG. 3, when a pilot signal is inserted in the received signal, the frequency error can be estimated without using a multiplication process using only the pilot signal and the synchronization signal (corresponding to the unmodulated signal in the same document).

  Subsequently, after correcting the frequency error in the frequency error correction block 6, the adaptive equalization circuit 7 performs a known adaptive equalization process on the corrected signal. Finally, the demodulation circuit 8 A determination value 2 for the equalization processing result is output.

  Thus, in the present embodiment, the frequency error is estimated using the signal after the adaptive equalization processing (output of the adaptive equalization circuit 3), that is, the signal in which the intersymbol interference component is suppressed. Therefore, higher frequency estimation accuracy can be realized. Further, since the transmission path characteristic used for adaptive equalization (processing of the adaptive equalization circuit 7) is the transmission path characteristic after removing the frequency error, better adaptive equalization operation characteristics can be obtained.

  In the present embodiment, the present invention is not limited to the above configuration, and for example, better results can be obtained by cascading the frequency error correction blocks 6 in a plurality of stages. Further, in the present embodiment, as an example of the adaptive equalization circuit, for example, a “linear equalizer” that suppresses an intersymbol interference component using a transversal filter with respect to a received signal can be cited. It is also possible to employ a “decision feedback equalizer”.

Embodiment 2. FIG.
Next, the receiver according to the second embodiment will be described. This embodiment is a further extension of the first embodiment described above. It should be noted that the same configuration (frequency error correction block 6, adaptive equalization circuit 7 and demodulation circuit 8) as in FIG. Here, only processing different from that of the first embodiment will be described.

  FIG. 4 is a diagram showing a configuration example of a receiver according to the present invention. This receiver further includes a frequency error estimation circuit 9 and a frequency error correction circuit 10 in addition to the configuration of the first embodiment. Yes. For example, a frequency error estimation circuit 9 and a frequency error correction circuit 10 are inserted between the adaptive equalization circuit 7 and the demodulation circuit 8 to perform frequency error estimation and correction on the output signal of the adaptive equalization circuit 7. The frequency error estimation process by the frequency error estimation circuit 9 is equivalent to the frequency error estimation circuit 4 described above.

  As a result, the frequency error can be estimated with higher accuracy, and the demodulation characteristics of the demodulation circuit 8 can be further improved.

  As described above, the receiver according to the present invention is useful for a system in which reception characteristics may be deteriorated due to distortion due to intersymbol interference, and in particular, reception including an adaptive equalizer corresponding to the intersymbol interference. Suitable for machine.

It is a figure which shows the structural example (Embodiment 1) of the receiver concerning this invention. It is a figure which shows an example of a received signal. It is a figure which shows an example of a received signal. It is a figure which shows the structural example (Embodiment 2) of the receiver concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reception signal input terminal 2 Determination value 3 Adaptive equalization circuit 4 Frequency error estimation circuit 5 Frequency error correction circuit 6 Frequency error correction block 7 Adaptive equalization circuit 8 Demodulation circuit 9 Frequency error estimation circuit 10 Frequency error correction circuit

Claims (3)

In the communication device (receiver) on the receiving side in wireless communication,
First adaptive equalization means for performing predetermined adaptive equalization processing using a known sequence included in the received signal;
First frequency error estimation means for estimating a frequency error from the output of the first adaptive equalization means;
First frequency error correcting means for performing frequency correction on the received signal based on the frequency error estimated value by the first frequency error estimating means;
Second adaptive equalization means for performing a predetermined adaptive equalization process on the frequency error correction value by the first frequency error correction means;
Demodulation means for demodulating the output of the second adaptive equalization means;
A receiver comprising: In the communication device (receiver) on the receiving side in wireless communication,
First adaptive equalization means for performing predetermined adaptive equalization processing using a known sequence included in the received signal;
First frequency error estimation means for estimating a frequency error from the output of the first adaptive equalization means;
First frequency error correcting means for performing frequency correction on the received signal based on the frequency error estimated value by the first frequency error estimating means;
Second adaptive equalization means for performing a predetermined adaptive equalization process on the frequency error correction value by the first frequency error correction means;
Second frequency error estimation means for estimating a frequency error from the output of the second adaptive equalization means;
Second frequency error correction means for performing frequency correction on the output of the second adaptive equalization means based on the frequency error estimated value by the second frequency error estimation means;
Demodulation means for demodulating a frequency error correction value by the second frequency error correction means;
A receiver comprising: The first adaptive equalization means, the first frequency error estimation means, and the first frequency error correction means are frequency error correction blocks,
3. The receiver according to claim 1, wherein the frequency error correction blocks are cascaded over a predetermined number.

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