JP2005168000A - Receiving apparatus and reception timing detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiving apparatus and a reception timing detecting method to detect symbol synchronous timing at high detection precision according to the state of a propagation path even in an environment that a multipath interference exists therein. <P>SOLUTION: The receiving apparatus uses an orthogonal frequency/code division multiple (OFCDM) transmission system or a multicarrier transmission system. It comprises a received signal information calculating means to calculate receiving signal information expressing the reception state of the received signal, an output composing means to compose received signal information in a prescribed section, and a symbol timing detecting means to detect the symbol synchronous timing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a reception apparatus and reception timing detection method used in a mobile communication system, and more particularly, to a reception apparatus and reception timing detection method using an orthogonal frequency / code division multiplexing (OFCDM) transmission system or a multicarrier transmission system. .

  At present, studies are being made on a wireless transmission system for a fourth generation mobile communication system aiming at higher speed and larger capacity than the third generation mobile communication system (W-CDMA system). For example, a multi-carrier CDMA (Code Division Multiple Access) system that performs multiplication of spreading codes in the frequency axis direction has tolerance against frequency selectivity of a propagation path due to multipath, which is a problem in mobile communication. This is a method that is actively studied for application to a radio transmission system of a generation mobile communication system (for example, see Non-Patent Document 1).

  The OFCDM (Orthogonal Frequency and Code Division Multiplexing) wireless transmission system is based on the above-described multi-carrier CDMA (Code Division Multiple Access) wireless transmission system, and replicates information symbols in the time axis direction and the frequency axis direction. Is multiplied by one chip of each spreading code, and then the spread signal is transmitted in parallel by OFCDM symbols having different times and a plurality of subcarriers having different frequencies. Accordingly, in this method, as a result, multiplication of spreading codes is performed in the time axis direction and the frequency axis direction, so that code multiplexing of a plurality of information channels can be realized by multiplying orthogonal spreading codes.

  In addition, parallel transmission using multiple subcarriers reduces the symbol rate and increases the symbol length.Therefore, the transmitted signal is a problem in the mobile communication environment. It is possible to reduce the influence of so-called multipath interference in which the signals arrive at the receiving unit at different timings through the propagation path) and the signals interfere with each other to deteriorate characteristics.

  Further, by providing a redundant portion called a guard interval that repeatedly transmits the portion after the symbol at the head portion of each OFCDM symbol, the influence of intersymbol interference caused by the influence of the multipath propagation path is reduced. Can do.

  Further, in the above multipath propagation path, frequency selective fading in which the propagation path varies depending on the frequency occurs, and the signal transmission quality changes depending on the frequency, but in OFCDM, the signal is spread in the frequency axis direction. The signal transmission quality can be improved by the frequency diversity effect.

On the other hand, the received signal of the OFCDM transmission system is FFT (Fast Fourier Transform).
Is restored to an information symbol for each subcarrier. Then, the same code as the spread code multiplied on the transmission side is multiplied in the time direction and the frequency direction, and despread by synthesizing the reception signal of each subcarrier over the spread code period. Here, the start position of the received signal input to the FFT, so-called symbol synchronization timing, is ideally the end of the guard interval, that is, the beginning of the information symbol section of the OFCDM signal, as shown in FIG. By making the portion ((1)), the signal of each delayed wave (here, the signals of the delayed waves 1 and 2) is received in the signal interval input to the FFT, that is, the FFT window interval ((2)). Thus, extraction can be performed without causing intersymbol interference.

However, as shown in FIG. 24B, when the detected symbol synchronization timing deviates from the ideal position due to the influence of the propagation path or the like, intersymbol interference occurs in the FFT window interval, and adjacent OFCDM signal components are Since they are extracted at the same time, transmission characteristics deteriorate due to intersymbol interference. For this reason, it is important to appropriately estimate the symbol synchronization timing. As a method for detecting the symbol synchronization timing, in the conventional multicarrier transmission in which information symbols are transmitted using a plurality of subcarriers having different frequencies, as in OFCDM transmission, the guard interval is a repetition of the portion after the multicarrier transmission signal. A method of detecting the symbol synchronization timing using the autocorrelation of the repetitive portion by using the signal is shown (for example, see Non-Patent Documents 2 and 3).
Also, from this point of view, a method is described in which a repetitive signal is inserted at the head of an information signal section, and symbol synchronization timing is detected using the autocorrelation of the received signal measured in this portion (for example, non-patent) Reference 4).

  Further, after cross-correlation between the known pilot signal and the received signal at the receiving side, the position where the maximum correlation value is obtained is detected from the obtained correlation value sequence, and the correlation value is searched forward from the position, A method of detecting, as timing, the position of a correlation value that is in the forefront that exceeds a threshold value (see, for example, Non-Patent Document 5).

In the multi-carrier CDMA mobile communication system, a plurality of candidates are provided as optimum base stations on the mobile station side, and the FFT timing of the optimum cell is detected by obtaining the respective correlations, and the scramble code is detected. Thus, a technique has been proposed that can detect a spread code at high speed and high accuracy on the receiving station side (see, for example, Patent Document 1).
JP 2003-152681 A “Multi-carrier CDMA in indoor wireless radio networks,” N. Yee et al., 1993 IEEE Personal and Indoor Mobile Radio Communication “ML estimation of time and frequency offset in OFDM system” J.-J. v. De Beek, M. Sandell, PO Brjesson, IEEE Trans. Signal Proc., Vol. 45, no.7, pp. 1800-1805, July 1997 “Maximum Likelihood Symbol Timing / Frequency Offset Estimation Method for Multi-Carrier Modulated Signals” Okada, Hara, Komaki, Morinaga: IEICE Technical Report, RCS95-118, pp45-50, January 1996 “A fast synchronization scheme of OFDM signals for high-rate wireless LAN” T. Onizawa et al., IEICE Transactions on Communications, vol.E82-B, no.2, pp.455-463, February 1999 "Timing synchronization method of OFDM communication system in frequency selective fading environment" Hira, Ishizu, Miyake: IEICE Transactions, B Vol.J84-B No.7 pp.1255-1264 July 2001

  However, when the OFCDM transmission scheme is applied to a mobile communication environment, it is difficult to detect ideal symbol synchronization timing due to the influence of multipath interference. In the method described in Non-Patent Document 2 described above, no study has been made assuming multipath interference. In addition, in the conventional method of detecting the symbol synchronization timing using the autocorrelation of the repetitive portion, including Non-Patent Document 3, when the correlation sequence is gentle, the timing is shifted and a delayed wave having a large power is incident. However, there is a problem that the synchronization position is shifted backward. In particular, in a transmission line with a large delay spread, interference occurs from the preceding and following symbols, and the autocorrelation characteristics are greatly degraded.

  Further, in the conventional technique described in Non-Patent Document 4, in order to detect the maximum value of the autocorrelation output of the received signal and reduce the influence of multipath interference, the timing ahead by a certain timing is used as the symbol synchronization timing. Although the detection method is shown, in this conventional method, it is necessary to optimize the timing value shifted forward according to the propagation path, and it is possible to flexibly cope with the situation of the propagation path that changes from moment to moment. It is difficult.

  In the conventional technique described in Non-Patent Document 5, a correlation value exceeding a threshold corresponding to 1 / a of the maximum correlation value is searched forward from the position where the maximum correlation value is obtained. When a large delay wave exists, the received power after FFT cannot be maximized, and intersymbol interference increases. In addition, since the optimum threshold value varies greatly depending on the transmission path model, it is necessary to optimize the threshold value, and it is difficult to flexibly cope with the propagation path situation that changes every moment.

  On the other hand, the conventional example described in Japanese Patent Laid-Open No. 2003-152681 describes that the FFT timing of the optimum cell can be detected by providing a plurality of candidates as a base station. The FFT timing is obtained based on the timing for obtaining the maximum correlation value for detecting the correlation between the received signal including all the subcarrier components before the synchronization and the synchronization signal replica, and the correlation value after the FFT is maximized. Therefore, it is considered difficult to accurately detect the symbol synchronization timing according to the propagation path condition.

  The present invention has been made in view of the above problems, and the problem is that even in an environment where multipath interference exists, symbol synchronization is performed with high detection accuracy in accordance with propagation path conditions. It is an object of the present invention to provide a receiving apparatus and a receiving timing detection method capable of detecting timing.

In order to solve the above-described problems, a receiving apparatus according to the present invention calculates received signal information indicating a reception state of a received signal in a receiving apparatus using an orthogonal frequency / code division multiplexing (OFCDM) transmission method or a multicarrier transmission method. Received signal information calculating means; output combining means for combining correlation values detected based on the received signal information in a predetermined interval; and symbol timing detecting means for detecting symbol synchronization timing based on the combined values; It is characterized by providing.
According to an embodiment of the present invention, the symbol timing detecting unit uses the value synthesized by the output synthesizing unit so that the received signal power to interference power ratio or the received power after FFT is maximized. Detect synchronization timing.

According to an embodiment of the present invention, the reception signal information calculation unit calculates a cross-correlation value of a known pilot signal as the reception signal information.
According to an embodiment of the present invention, the reception signal information calculation unit calculates an autocorrelation value of the reception signal as the reception signal information.
According to one embodiment of the present invention, the received signal information calculating means calculates a propagation path fluctuation estimated value estimated based on a known pilot signal transmitted by the transmitting side as the received signal information.
According to an embodiment of the present invention, the receiving device includes a replica signal generating unit that generates a replica signal of a desired signal and an interference signal based on a calculation result of the received signal information, and the output combining unit includes: The replica signal is synthesized in a predetermined section, and the symbol timing detection means detects symbol synchronization timing using the synthesized replica signal.
According to an embodiment of the present invention, the output combining unit sets reception timings of a plurality of delayed waves in a received signal as a plurality of symbol synchronization timing candidates, and uses the replica signal generated by the replica signal generating unit as the plurality of replica signals. The symbol timing detection means detects, as a symbol synchronization timing, a timing at which the combined value of the replica signal is maximum among the plurality of symbol synchronization timing candidates. To do.

  Alternatively, the output synthesizing unit sets a timing obtained by shifting a reception timing of a plurality of delayed waves in the received signal by a predetermined amount as a plurality of symbol synchronization timing candidates, and uses the replica signal generated by the replica signal generating unit as the plurality of The symbol timing detection means detects a timing at which a composite value of the replica signal is maximum among the plurality of symbol synchronization timing candidates as a symbol synchronization timing. .

  Alternatively, the output synthesizing means sets a timing obtained by shifting a reception timing of at least one delayed wave in the received signal and a reception timing of at least one other delayed wave in the received signal as a plurality of symbol synchronization timing candidates. The replica signal generated by the replica signal generation means is synthesized in a predetermined section related to each of the plurality of symbol synchronization timing candidates, and the symbol timing detection means includes the symbol synchronization timing candidates among the plurality of symbol synchronization timing candidates. The timing at which the composite value of the replica signal is maximized is detected as the symbol synchronization timing.

  Further, according to one embodiment of the present invention, the symbol timing detection means includes SIR estimation means for estimating a received signal power to interference power ratio after FFT using the synthesized replica signal, and the estimation result The symbol synchronization timing is detected based on the above.

A reception timing detection method according to the present invention is a reception timing detection method in a reception apparatus using an orthogonal frequency / code division multiplexing (OFCDM) transmission system or a multicarrier transmission system, and receives reception signal information indicating a reception state of a reception signal. A calculating step;
Synthesizing correlation values detected based on the received signal information in a predetermined interval; and detecting symbol synchronization timing based on the synthesized values.

  According to the embodiment of the present invention, in the case of OFCDM transmission or multicarrier transmission, when there is multipath interference, it is possible to detect an appropriate symbol synchronization timing according to the propagation path condition, and to detect a symbol accompanying a timing shift. Interference can be reduced. As a result, it is possible to improve signal transmission characteristics.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an OFCDM receiving apparatus to which an OFCDM transmission system, which is a receiving apparatus according to an embodiment of the present invention, is applied. Here, the OFCDM transmission method means that information symbols are duplicated and arranged in the time direction and the frequency direction, and the spread information symbols are multiplied by spreading codes in the time axis direction and the frequency axis direction to spread each symbol. Is a signal transmission method using a plurality of symbols having different times and a plurality of subcarriers having different frequencies. Moreover, this OFCDM transmission system is one of typical multiplexing systems using a plurality of carriers in the downlink channel in a mobile communication system.

  In this figure, this OFCDM receiving apparatus 1 includes a symbol synchronization timing detection unit 10, a guard interval removal unit 11, a time / frequency conversion unit (FFT) 12, a spread signal generation unit 13, and multipliers 14-1 to 14-1. 14-l, 15-1 to 15-m, 16-1 to 16-n, symbol synthesis units 17-1 to 17-n, parallel-serial conversion unit 18, data demodulation unit 19, and error correction decoding unit 20 and an information symbol restoration unit 21.

  In this embodiment, when the received OFCDM signal is input to the timing detection circuit 10 (hereinafter referred to as a symbol synchronization timing detection unit), the symbol synchronization timing is detected in the same unit 10. Thereafter, the guard interval removing unit 11 removes the guard interval, and the time / frequency converting unit (FFT) 12 separates the received OFCDM signal into components of each subcarrier frequency. Then, in the multipliers 14-1 to 16-n, after being spread with spread signals (spread codes generated by the spread signal generator 13) corresponding to each information channel on the time axis and the frequency axis, symbol synthesis is performed. The signals before being spread are restored by being input to the units 17-1 to 17-n and synthesizing symbols over the spreading period. The signal restored in this manner is subjected to parallel-to-serial conversion by the parallel-serial converter 18, data demodulation by the data demodulator 19, error correction decoding by the error correction decoder 20, and information symbol recovery unit 21. The information signal transmitted at is restored.

  Next, the symbol synchronization timing detection unit shown in FIG. 1 will be described. FIG. 2 is a block diagram illustrating a first embodiment of the symbol synchronization timing detection unit.

  In the figure, the symbol synchronization timing detection unit 10 according to the first embodiment includes a correlation detection unit 31, an output synthesis unit 32, and a received signal power-to-interference power ratio maximum value detection unit 33. A function is provided for detecting the symbol synchronization timing so that the received signal power to interference power ratio after FFT is maximized using information. In the present embodiment, an example is shown before the OFCDM received signal is input to the guard interval removing unit 11.

  The operation of the symbol synchronization timing detection unit configured as described above will be described. The received OFCDM signal is input to the correlation detection unit 31, and the obtained correlation output is combined by the output combining unit 32 over a certain interval. Thereafter, the received signal power to interference power ratio maximum value detection unit 33 detects the timing at which the received signal power to interference power ratio is maximized as the symbol synchronization timing.

  FIG. 3 is a block diagram showing a second embodiment of the symbol synchronization timing detector shown in FIG.

  As shown in the figure, the symbol synchronization timing detection unit 10 according to the present embodiment includes a correlation detection unit 41, an output synthesis unit 42, and a reception signal power maximum value detection unit 43, and uses reception signal information. Thus, a function of detecting the symbol synchronization timing is provided so that the received signal power after the FFT is maximized. In the present embodiment, as in the case of FIG. 2 described above, an example before the OFCDM received signal is input to the guard interval removing unit 11 is shown.

  The operation of the symbol synchronization timing detection unit configured as described above will be described. The received OFCDM signal is input to the correlation detection unit 41, and the obtained output is combined by the output combining unit 42 over a certain interval. Thereafter, the maximum received signal power value detection unit 43 detects the timing at which the received signal power is maximum as the symbol synchronization timing.

  FIG. 4 shows that a pilot signal for detecting symbol synchronization timing is transmitted separately from the information signal in order to cause the symbol synchronization timing detection unit of the OFCDM receiving apparatus to detect the symbol synchronization timing using the correlation value of the received signal. It is a block diagram which shows the structure of the OFCDM transmission apparatus which is a transmission side apparatus in the case of performing.

  In this figure, the OFCDM transmission apparatus 2 includes an information signal generation unit 50, a symbol synchronization timing detection pilot signal generation unit 51, a serial-parallel conversion unit 52, a spread signal generation unit 53, and a symbol duplication unit 54-1. To 54-m, multipliers 55-1 to 57-n, a frequency / time conversion unit (IFFT) 58, and a guard interval insertion unit 59.

  In the present embodiment, the information signal generated by data modulation by the information signal generation unit 50 and the pilot signal generated by the symbol synchronization timing detection pilot signal generation unit 51 are the same procedure, that is, by the serial-parallel conversion unit 52. Series-parallel conversion, duplication in the time axis direction and frequency axis direction in the symbol duplication units 54-1 to 54-n, time axis direction and frequency axis by the spread signal generation unit 53 and the multipliers 55-1 to 57-n This is multiplication of spread signals in the direction and frequency / time conversion processing in the frequency / time conversion unit (IFFT) 58. When frequency / time conversion processing is performed in the frequency / time conversion unit (IFFT) 58, it is converted into an OFCDM signal. Note that the transmission form of the pilot signal may be a transmission form added to the information signal, or may be transmitted in a signal form different from the information signal.

  FIG. 5 is a diagram showing a transmission form of a symbol synchronization timing detection pilot signal transmitted by the OFCDM transmission apparatus shown in FIG. As shown in the figure, in the present embodiment, the symbol signal timing detection pilot signal is time-multiplexed with an information signal period and a pilot signal period.

  In the embodiment shown in FIG. 4 and FIG. 5, the mode in which the pilot signal for detecting the symbol synchronization timing is time-multiplexed is illustrated. However, the present invention is not limited to this mode. For example, FIG. As in the embodiment shown in FIG. 2, a code multiplexing type configuration in which an information signal (signals of information channels # 1 to #n in this example) and a pilot signal for symbol synchronization timing detection are spread and multiplexed by different spreading codes Alternatively, as in the embodiment shown in FIGS. 8 and 9, a symbol synchronization timing detection pilot signal is input to the frequency / time conversion unit (IFFT) 97, and the pilot signal is multiplexed on a specific subcarrier frequency. A frequency multiplexing configuration may be used.

  The pilot signal may have a configuration of a common pilot signal that is multiplied by a common spreading code in all information channels, or may have a configuration of an individual pilot signal that is multiplied by an individual spreading code for each information channel.

  FIG. 10 shows symbol synchronization timing using a cross-correlation value of a received signal as received signal information when a pilot signal for symbol synchronization timing detection is transmitted from any of the OFCDM transmitting apparatuses of FIG. 4, FIG. 6, and FIG. 2 is a block diagram illustrating a configuration of a symbol synchronization timing detection unit of an OFCDM receiving apparatus that detects a signal.

  In the figure, the symbol synchronization timing detector 10 includes an OFCDM signal generator 110, a correlation detector 111, an output combiner 112, and a combined output maximum value detector 113. In the present embodiment, an example is shown before the OFCDM received signal is input to the guard interval removing unit 11.

  In the present embodiment, first, a known pilot signal is input to the OFCDM signal generation unit 110 to generate a reference OFCDM signal. Then, correlation detection section 111 obtains a cross-correlation output between the generated reference OFCDM signal and the pilot signal section of the received OFCDM signal. The cross-correlation output obtained in this way by the correlation detection unit is combined over a certain interval in the output combination unit 112, and the combined output maximum value detection unit 113 detects the symbol synchronization timing at which the combined output is maximum. Is done.

  In the embodiment shown in FIG. 10, the mode of detecting the symbol synchronization timing using the cross-correlation value of the received signal as the received signal information is exemplified. However, in the embodiment shown in FIG. 11, the symbol synchronization timing of the OFCDM receiving apparatus is used. The detection unit has a function of detecting the symbol synchronization timing using the guard interval section of the received OFCDM signal as the received signal information.

  In the figure, the symbol synchronization timing detector 10 includes a delay circuit 120, a correlation detector 121, an output combiner 122, and a combined output maximum value detector 123. In the present embodiment, an example is shown before the OFCDM received signal is input to the guard interval removing unit 11.

  In the present embodiment, the received OFCDM signal is input to the delay circuit 120 and the correlation detection unit 121. In the delay circuit 120, for example, a delay time of time T is set. The received OFCDM signal and the output signal of delay circuit 120 are input to correlation detection section 121, and an autocorrelation output between the guard interval section and the information symbol section is obtained. The autocorrelation output obtained in this way by the correlation detection unit 121 is synthesized over a certain interval by the output synthesis unit 122, and the synthesized output maximum value detection unit 123 detects the symbol synchronization timing at which the synthesized output becomes maximum. Is done.

  FIG. 12 shows, in addition to the information signal, a known pilot signal for estimating the propagation path fluctuation value, in order to cause the symbol synchronization timing detection unit of the OFCDM receiving apparatus to detect the symbol synchronization timing using the estimation value of the propagation path fluctuation. It is a block diagram which shows the structure of the OFCDM transmission apparatus in the case of transmitting.

  In this figure, this OFCDM transmission apparatus 5 includes an information signal generation unit 130, a propagation path fluctuation value estimation pilot signal generation unit 131, a serial-parallel conversion unit 132, a spread signal generation unit 133, and a symbol duplication unit 134- 1 to 134-m, multipliers 135-1 to 137-n, a frequency / time conversion unit (IFFT) 138, and a guard interval insertion unit 139.

In this embodiment, the information signal generated by data modulation by the information signal generation unit 130 and the pilot signal generated by the propagation path fluctuation value estimation pilot signal generation unit 131 are the same procedure, that is, by the serial-parallel conversion unit 52. Serial-parallel conversion, duplication in time axis direction and frequency axis direction in symbol duplication units 134-1 to 134-m, time axis direction and frequency axis direction by spread signal generation unit 133 and multipliers 135-1 to 137-n Multiplication of the spread signal at, and frequency / time conversion processing at the frequency / time conversion unit (IFFT) 138. When the frequency / time conversion process is performed in the frequency / time conversion unit (IFFT) 138, the signal is converted into an OFCDM signal. Note that the transmission form of the pilot signal may be a transmission form added to the information signal, or may be transmitted in a signal form different from the information signal.

  FIG. 13 is a diagram showing a transmission form of a propagation path fluctuation value estimation pilot signal transmitted by the OFCDM transmission apparatus shown in FIG. As shown in the figure, in this embodiment, the pilot signal for propagation path fluctuation value estimation is time-multiplexed with the information signal section and the pilot signal section. However, as in the embodiment shown in FIGS. In addition, a code multiplexing configuration in which the information signal and the pilot signal are spread and multiplexed by different spreading codes may be used, or the pilot signal may be multiplexed on a specific subcarrier frequency as in the embodiment shown in FIGS. A frequency multiplexing configuration may be used.

  Note that the propagation path fluctuation value estimation pilot signal may have a configuration of a common pilot signal multiplied by a common spreading code in all information channels, or an individual pilot signal multiplied by an individual spreading code for each information channel. A configuration may be taken.

  FIG. 14 shows symbols of the OFCDM receiving apparatus that estimates the propagation path fluctuation based on the pilot signal for estimating the propagation path fluctuation value transmitted from the OFCDM transmission apparatus shown in FIG. 12, and detects the symbol synchronization timing using the estimated value. It is a block diagram which shows the structure of a synchronous timing detection part.

  In the figure, the symbol synchronization timing detector 10 includes a propagation path fluctuation value estimator 150, a frequency / time converter (IFFT) 151, an output combiner 152, and a combined output maximum value detector 153. Is done. In the present embodiment, an example is shown before the OFCDM received signal is input to the guard interval removing unit 11.

  In this embodiment, first, in the propagation path fluctuation value estimation unit 150, the influence of the propagation path fluctuation received by the signal transmitted while reaching the OFCDM reception apparatus from the OFCDM transmission apparatus is used to estimate the received propagation path fluctuation value. It estimates for every subcarrier frequency using the signal area of a pilot signal. This can be estimated from the fluctuation amount of the signal by utilizing the fact that the pilot signal for estimating the propagation path fluctuation value and the like has known amplitude, phase and pattern.

  The propagation path fluctuation value for each subcarrier frequency estimated by the propagation path fluctuation value estimation unit 150 as described above is input to the frequency / time conversion unit (IFFT) 151, and an impulse response of the propagation path, that is, a complex delay profile. Is required. The delay profile obtained in this manner, that is, the propagation path fluctuation value for each subcarrier frequency is synthesized over a certain section by the output synthesis unit 152, and the synthesized output maximum value detection unit 153 has the maximum synthesized output. Synchronization timing is detected.

  As described above, in this embodiment, an example in which a delay profile is obtained from a propagation path fluctuation value for each subcarrier is illustrated. However, a propagation path delay profile is directly set using a pilot signal for propagation path fluctuation estimation. You may ask for it.

  FIG. 15 is a configuration diagram of a symbol synchronization timing detection unit for explaining a case where symbol synchronization timing is detected using a value obtained by combining the received signal information over a certain interval. As shown in the figure, the symbol synchronization timing detector 10 includes a correlation detector 161, an output combiner 162, and a combined output maximum value detector 163.

  In general, since the OFCDM signal is a signal obtained by superimposing the information signals of the subcarriers, the signal waveform is a Gaussian noise signal by the central limit theorem. For this reason, the received signal information ((1) the cross-correlation value of the known pilot signal, (2) the autocorrelation value of the received signal, and (3) the channel shown in the embodiment of FIGS. In the case where the estimated signal is used as received signal information), when the delay spread of the received signal in the multipath propagation path is small, the maximum value of the correlation output substantially coincides with the ideal symbol synchronization timing as shown in FIG. Therefore, an appropriate symbol synchronization timing can be detected by estimating the timing at which the correlation output is maximized.

  However, in general, in a multipath propagation path, as shown in FIG. 17, the delay spread of the received signal may increase due to the geographical condition of the communication path. Therefore, in such a case, the probability that the maximum value of the correlation output greatly deviates from the ideal symbol synchronization timing becomes high, and there is a problem that intersymbol interference occurs.

  Therefore, in the present invention, as shown in FIG. 18, the obtained received signal information is synthesized over a certain interval in the output synthesis unit 162, and the synthesis start position at which the synthesized value output becomes the maximum is the synthesized output maximum. The value detection unit 163 detects the timing as symbol synchronization timing. Thereby, even when the timing of the maximum value of the correlation output greatly deviates from the ideal symbol synchronization timing due to the influence of multipath interference, the power of the direct wave component and the delayed wave component of the OFCDM signal 1 symbol can be generated in the FFT window section. Since it is possible to detect the symbol synchronization timing that can be secured as much as possible according to the propagation path condition, it is possible to reduce interference from adjacent symbols.

  FIG. 19 is a block diagram illustrating a configuration of a symbol synchronization timing detection unit having a function of creating a replica signal of a desired signal and an interference signal using the received signal information and detecting a symbol synchronization timing using the replica signal FIG.

  In the figure, the symbol synchronization timing detection unit 10 includes an OFCDM signal generation unit 170, a correlation detection unit 171, a path detection unit 172, a desired / interference replica signal generation unit 173, an output combining unit 174, and a combined output. And a maximum value detection unit 175.

  An example of the operation of the symbol synchronization timing detection unit 10 configured as shown in FIG. 19 will be described with reference to FIG. FIG. 20 is a diagram illustrating a first example of the symbol synchronization timing detection method according to the present embodiment.

  FIG. 20 shows, as an example, a case where the received signal power and the interference power ratio are estimated using the received signal information of (1) above.

  In the present embodiment, correlation detection section 171 creates a delay profile based on the cross-correlation value between the reference pilot signal generated by OFCDM signal generation section 170 and the received OFCDM signal. The delay profile is the propagation delay time (= delay time) of the radio wave arriving at the receiving side (in this example, the OFCDM receiving apparatus) on the horizontal axis, the received power on the vertical axis, and each received incoming wave as a short pulse. This is shown on the delay time axis. FIG. 20 (1) shows an example of a delay profile in the present embodiment.

  The delay profile created as described above is input to the path detection unit 172, and the path detection unit 172 detects a delayed wave component (path) having a large signal power by threshold determination. Here, it is assumed that L paths are detected.

The desired / interference replica signal generation unit 173 includes the power value Si (i = 1, 2,..., L) of each of the L paths detected by the path detection unit 172 and the relative delay from the head path. A signal replica with (D _L + N _FFT + N _GI ) samples per path using time Di (i = 1, 2,..., L)

を生成する。ここで、Ｎ_ＦＦＴおよびＮ_ＧＩはそれぞれＦＦＴウィンドウ区間およびガードインターバル区間のサンプル数を表す。ただし、

Is generated. Here, N _FFT and N _GI represent the number of samples in the FFT window section and the guard interval section, respectively. However,

はD_ｉ ＜τ＜D_ｉ+Ｎ_ＦＦＴ+Ｎ_ＧＩで

Is D _i < τ <D _i + N _FFT + N _GI

、その他のタイミングで

At other times

とする。さらに、Ｌ個の信号レプリカ

And In addition, L signal replicas

をサンプル毎に合成することで、希望信号レプリカＳ（τ）を求める。

For each sample, a desired signal replica S (τ) is obtained.

Further, the interference signal replica I (τ) obtains a sample value max {S (τ)} having the maximum value among (D _L + N _FFT + N _GI ) samples of the desired signal replica S (τ), and I (( τ) = max {S (τ)} − S (τ).

  The output synthesizer 174 synthesizes S (τ) and I (τ) obtained as described above in the FFT window section, thereby estimating the SIR of the received signal after the FFT by the following equation.

合成出力最大値検出部１７５は、上記推定されたＳＩＲ（τ）が最大となるサンプルタイミングτ_ｍａｘをシンボル同期タイミングとして検出し、ＦＦＴに出力
する。

The combined output maximum value detection unit 175 detects the sample timing τ _max at which the estimated SIR (τ) is maximum as the symbol synchronization timing, and outputs it to the FFT.

  FIG. 21 is a diagram illustrating a second example of the symbol synchronization timing detection method by the symbol synchronization timing detection unit 10 in FIG.

  As described above, the correlation detection unit 171 creates a delay profile and inputs it to the path detection unit 172. The path detection unit 172 detects L delayed wave components (paths).

The desired / interference replica signal generation unit 173 generates a signal replica for each path.
Further, the desired signal replica S (τ) is obtained by synthesizing L signal replicas for each sample, and the interference signal replica I (τ) is obtained.

Output combining unit 174, the delay time D1, D2, _..., D i, ..., reception timing symbol synchronization timing candidates of each delay wave as a _{D L} (path) (candidate 1, candidate 2, ..., candidate i, .. Candidate L), and the desired signal replica S (τ) and the interference signal replica I (τ) generated by the desired / interference replica signal generation unit 173 are used as the symbol synchronization timing candidate 1, candidate 2,. i,... are synthesized in a predetermined section relating to each of the candidates L, for example, in an FFT window section of each path.

  The combined output maximum value detection unit 175 detects a symbol synchronization timing candidate that maximizes the combined value of the replica signal obtained in the FFT window section of each path as the symbol synchronization timing.

  FIG. 22 is a diagram illustrating a third example of the symbol synchronization timing detection method by the symbol synchronization timing detection unit 10 in FIG.

  Similar to the symbol synchronization timing detection method shown in FIG. 21, the correlation detection unit 171 creates a delay profile and inputs it to the path detection unit 172. The path detection unit 172 detects L paths (delayed wave components). The desired / interference replica signal generation unit 173 obtains a desired signal replica S (τ) and an interference signal replica I (τ).

Output combining unit 174, the delay time D1, D2, ..., D i , ..., a timing obtained by shifting a predetermined section of the reception timing of the delay wave as a D _L (path), for example, the timing shifted by guard interval Symbol synchronization timing candidates (candidate 1, candidate 2,..., Candidate i,... Candidate L), and desired signal replica S (τ) and interference signal replica I (τ) generated by desired / interference replica signal generation section 173 are used. , Symbol synchronization timing candidate 1, candidate 2,..., Candidate i,..., And candidate L, for example, FFT windows in each path.

  The combined output maximum value detection unit 175 detects a symbol synchronization timing candidate that maximizes the combined value of the replica signal obtained in the FFT window section of each path as the symbol synchronization timing.

  Furthermore, the symbol synchronization timing can be detected by combining the methods shown in FIGS.

  FIG. 23 is a diagram illustrating a fourth example of the symbol synchronization timing detection method performed by the symbol synchronization timing detection unit 10 in FIG.

  Similar to the symbol synchronization timing detection method shown in FIGS. 21 and 22, correlation detection section 171 creates a delay profile and inputs it to path detection section 172. The path detection unit 172 detects L paths (delayed wave components). The desired / interference replica signal generation unit 173 obtains a desired signal replica S (τ) and an interference signal replica I (τ).

In the delay profile in FIG. 23, D from the delay time D _{i L} is leading path exceeds the guard interval fraction viewed from (delay time D1), the delay time D2 is the guard interval fraction as viewed from the head path Not exceeded.

As shown in FIG. 23, for example, the output combining unit 174 sets the reception timing of the delay wave (path) with the delay time D1 as the symbol synchronization timing candidate (candidate 1), and the delay time when viewed from the head path is reception timing of arbitrary path among the paths that exceed the guard interval fraction, for example, the timing of shifting the D _i constant interval, for example, the symbol synchronization timing candidates timing shifted by guard interval (candidate 2), also , for example, the timing of the reception timing of the delay wave is shifted a predetermined interval corresponding to the delay time D _L, which exceeds the guard interval fraction, for example, the symbol synchronization timing candidates (candidate L) also the timing shifted by guard interval . The output synthesizer 174 uses the above timing candidates, converts the desired signal replica S (τ) and the interference signal replica I (τ) generated by the desired / interference replica signal generation unit 173 into a symbol synchronization timing candidate 1 and a candidate. 2,... Are combined in a predetermined section relating to each of the candidates L, for example, in the FFT window section of each path.

  The combined output maximum value detection unit 175 detects a symbol synchronization timing candidate that maximizes the combined value of the replica signal obtained in the FFT window section of each path as the symbol synchronization timing.

That is, according to the present embodiment, in the FFT window period, the symbol synchronization that secures as much as possible the power of the direct wave component and the delayed wave component of one symbol of the OFCDM signal while minimizing the influence of intersymbol interference. The timing can be detected according to the propagation path condition. Therefore, even when the maximum correlation output timing deviates significantly from the ideal symbol synchronization timing due to the influence of multipath interference,
Highly accurate symbol synchronization can be realized.

  In the present embodiment, the aspect of using the cross-correlation value of a known pilot signal is exemplified as the received signal information. However, an autocorrelation value of the received signal or a channel estimated value estimated from the received signal may be used. .

  In each of the above-described embodiments, the aspect of the OFCDM receiving apparatus to which the OFCDM transmission system is applied is illustrated as a preferred example. However, in the receiving apparatus to which the multicarrier transmission system that transmits information symbols by using a plurality of subcarriers having different frequencies Also, the present invention can be applied.

  In the above embodiment, the symbol synchronization timing is detected so that the received signal power after the FFT is maximized. However, the received signal power may be obtained by actual measurement or using a propagation path profile or the like. May be estimated.

  There is also an aspect in which reception quality information (or communication quality information) such as BER (bit error rate) is used as reception signal information, and symbol synchronization timing is detected so that reception quality after FFT is maximized. Conceivable.

It is a block diagram which shows the structure of the OFCDM receiving apparatus which is a receiving apparatus which concerns on one embodiment of this invention. It is a block diagram which shows 1st Embodiment of a symbol synchronization timing detection part. It is a block diagram which shows 2nd Embodiment of a symbol synchronization timing detection part. It is a block diagram which shows 1st Embodiment of an OFCDM transmission apparatus. It is a figure which shows the transmission form of the pilot signal for a 1st symbol synchronization timing detection. It is a block diagram which shows 2nd Embodiment of an OFCDM transmission apparatus. It is a figure which shows the transmission form of the 2nd pilot signal for a symbol synchronization timing detection. It is a block diagram which shows 3rd Embodiment of an OFCDM transmission apparatus. It is a figure which shows the transmission form of the pilot signal for the 3rd symbol synchronization timing detection. It is a block diagram which shows 3rd Embodiment of a symbol synchronization timing detection part. It is a block diagram which shows 4th Embodiment of a symbol synchronization timing detection part. It is a block diagram which shows 4th Embodiment of an OFCDM transmission apparatus. It is a figure which shows the transmission form of the pilot signal for propagation path fluctuation value estimation. It is a block diagram which shows 5th Embodiment of a symbol synchronization timing detection part. It is a block diagram of the symbol synchronization timing detection part for demonstrating the case where a symbol synchronization timing is detected using the synthesized value of received signal information. It is a figure for demonstrating the case where the maximum value of a correlation output substantially corresponds with an ideal symbol synchronous timing. It is a figure for demonstrating the case where the maximum value of a correlation output shift | deviates largely from an ideal symbol synchronous timing. It is a figure which shows the concept which detects a symbol synchronization timing based on the synthesized value of received signal information. It is a block diagram which shows 6th Embodiment of a symbol synchronization timing detection part. It is a figure which shows the 1st example of the symbol synchronization timing detection method by the symbol synchronization timing detection part 10 in FIG. It is a figure which shows the 2nd example of the symbol synchronization timing detection method by the symbol synchronization timing detection part 10 in FIG. It is a figure which shows the 3rd example of the symbol synchronization timing detection method by the symbol synchronization timing detection part 10 in FIG. It is a figure which shows the 4th example of the symbol synchronization timing detection method by the symbol synchronization timing detection part 10 in FIG. It is a figure which shows the concept of symbol synchronization timing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 OFCDM receiver 2-5 OFCDM transmitter 10 Symbol synchronization timing detection part 11 Guard interval removal part 12 Time and frequency conversion part (FFT)
13 Spreading signal generators 14-1 to 14-l, 15-1 to 15-m, 16-1 to 16-n, 55-1 to 55-l, 56-1 to 56-m, 57-1 to 57 -N, 75-1 to 75-l, 76-1 to 76-m, 77-1 to 77-n, 94-1 to 94-l, 95-1 to 95-m, 96-1 to 96-n , 135-1 to 135-1, 136-1 to 136 -m, 137-1 to 137 -n multipliers 17-1 to 17-n Symbol synthesis unit 18 Parallel-serial conversion unit 19 Data demodulation unit 20 Error correction decoding unit 21 Information symbol restoration unit 31, 41, 111, 121, 161, 171 Correlation detection unit 32, 42, 112, 122, 152, 162, 174 Output combining unit 33 Received signal power to interference power ratio maximum value detection unit 43 Received signal Maximum power detection unit 50, 71, 90, 130 Information signal Generator 51, 98 Symbol synchronization timing detection pilot signal generator 52, 72, 91, 132 Series-parallel converter 53, 73, 92, 133 Spread signal generator 54-1 to 54-m, 74-1 to 74- m, 93-1 to 93-m, 134-1 to 134-m Symbol duplication unit 58, 79, 97, 138, 151 Frequency / time conversion unit (IFFT)
59, 80, 99, 139 Guard interval insertion section 78 Each information channel and pilot signal combining section 110, 170 OFCDM signal generating section 113, 123, 153, 163, 175 Combined output maximum value detecting section 120 Delay circuit 131 Propagation path fluctuation value Pilot signal generation unit for estimation 150 Channel fluctuation value estimation unit 172 Path detection unit 173 Desired / interference replica signal generation unit

Claims (11)

In a receiver using an orthogonal frequency / code division multiplexing (OFCDM) transmission system or a multicarrier transmission system,
Received signal information calculating means for calculating received signal information representing the received state of the received signal;
Output combining means for combining the correlation values detected based on the received signal information in a predetermined section;
Symbol timing detection means for detecting symbol synchronization timing based on the synthesized value;
A receiving apparatus comprising: The receiving device according to claim 1,
The symbol timing detecting means detects symbol synchronization timing so that the received signal power to interference power ratio or received power after FFT is maximized using the value synthesized by the output synthesizing means. Receiver device. The receiving apparatus according to claim 1 or 2,
The reception signal information calculation means calculates a cross-correlation value of a known pilot signal as the reception signal information. The receiving apparatus according to claim 1 or 2,
The reception signal information calculating means calculates an autocorrelation value of a reception signal as the reception signal information. The receiving apparatus according to claim 1 or 2,
The received signal information calculating means calculates a propagation path fluctuation estimated value estimated based on a known pilot signal transmitted by a transmitting side as the received signal information. The receiving device according to claim 1,
Based on the calculation result of the received signal information, comprising a replica signal generating means for generating a replica signal of a desired signal and an interference signal,
The output combining means combines the replica signal in a predetermined section,
The symbol timing detection means detects a symbol synchronization timing using the synthesized replica signal. The receiving device according to claim 6,
The output synthesizing unit sets reception timings of a plurality of delayed waves in the received signal as a plurality of symbol synchronization timing candidates, and sets the replica signal generated by the replica signal generation unit to a predetermined number related to each of the plurality of symbol synchronization timing candidates. In the interval
The symbol timing detection unit detects a timing at which a composite value of the replica signal is maximum among the plurality of symbol synchronization timing candidates as a symbol synchronization timing. The receiving device according to claim 6,
The output synthesizing unit sets a timing obtained by shifting a reception timing of a plurality of delayed waves in the received signal by a predetermined amount as a plurality of symbol synchronization timing candidates, and uses the replica signal generated by the replica signal generating unit as the plurality of symbol synchronizations Combining in a predetermined section related to each of the timing candidates,
The symbol timing detection means detects, as a symbol synchronization timing, a timing at which a composite value of the replica signal is maximum among the plurality of symbol synchronization timing candidates. The receiving device according to claim 6,
The output synthesizing means sets a reception timing of at least one delayed wave in the received signal and a timing obtained by shifting a reception timing of at least one other delayed wave in the received signal by a predetermined amount as a plurality of symbol synchronization timing candidates, The replica signal generated by the replica signal generating means is combined in a predetermined section related to each of the plurality of symbol synchronization timing candidates,
The symbol timing detection means detects, as a symbol synchronization timing, a timing at which a composite value of the replica signal is maximum among the plurality of symbol synchronization timing candidates. The receiving device according to claim 6,
The symbol timing detection means includes SIR estimation means for estimating a received signal power to interference power ratio after FFT using the synthesized replica signal,
A receiver that detects symbol synchronization timing based on the estimation result. In a reception timing detection method in a receiver using an orthogonal frequency / code division multiplexing (OFCDM) transmission method or a multicarrier transmission method,
Calculating received signal information representing a reception state of the received signal;
Synthesizing correlation values detected based on the received signal information in a predetermined section;
Detecting symbol synchronization timing based on the synthesized value;
A reception timing detection method comprising:

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