JP2008167304A - Receiver, mobile station and base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To synchronize time with downlink OFDMA radio communication for which three P-SCHs are introduced, within a detection time same as in the case of one P-SCH and furthermore, to reduce computational complexity required for computing an inter-correlation value for the time synchronization. <P>SOLUTION: The present invention relates to a receiver 10 which is applied to a multicarrier communication system, comprising receiving units 11, 12 for receiving a multicarrier signal transmitted from at least one base station and containing at least one type of synchronization channel and a synchronizing unit 14 for synchronizing time using at least one common part with a different time division and the same time waveform among a plurality of types of synchronization channels. As a result of the time synchronization, a communication apparatus with optimal communication properties can be selected from among communication apparatuses corresponding to a plurality of communication control areas. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to mobile communication employing a multicarrier communication system, and in particular, for establishing time synchronization and maintaining time synchronization using a synchronization channel (SCH) included in a downlink (downlink transmission) signal. To receivers, mobile stations and base stations.

  In recent years, the third generation mobile communication (3G) including the W-CDMA system has become widespread worldwide, and the fourth generation that realizes a communication speed of 100 Mb / s to 1 Gb / s in the downlink. Mobile communication (4G) is being studied. Furthermore, in order to make a complete transition from the 3rd generation (3G) to the 4th generation (4G) smoothly, we introduced a communication system with high compatibility with 4G new technology while using the 3G frequency band. The standardization of E-UTRA (Evolved-UTRA) that speeds up communication is also underway.

  In a mobile communication system, a mobile station needs to detect a base station to which the mobile station is to connect and an antenna of the base station for initial synchronization establishment or for handover. In this way, the time synchronization performed for establishing a connection with the base station with which the mobile station is to communicate, that is, the work for adjusting the timing for accurately receiving the communication frame transmitted from the base station, The operation of acquiring information such as communication parameters required for communication with a base station is generally called “cell search”. The cell search is normally performed from time synchronization. Further, even after the connection with the base station is established, synchronization is maintained using a known signal (for example, SCH) by the same method as the cell search.

  For example, the cell search in the third generation mobile communication using the W-CDMA system is executed by a method divided into three steps called a three-stage cell search. In general, the three-step cell search uses a synchronization channel (SCH) and a common pilot channel (CPICH: Common Pilot Channel). First, the SCH reception timing is detected (first stage), then the frame timing and the scramble code group are identified by detecting the correlation of the SCH code (second stage), and then the correlation detection using the CPICH is performed. The scramble code is identified by (step 3). The three-stage cell search is performed by such a three-stage procedure.

  In addition, although E-UTRA, which is a next-generation mobile communication standard, uses OFDM (Orthogonal Frequency Division Multiplexing) as a modulation scheme, the cell search follows the above-described three-stage cell search concept. Have been proposed (see, for example, Non-Patent Document 1). In Non-Patent Document 1, time synchronization is performed by a first synchronization channel (P-SCH) in a three-stage cell search in a multicarrier communication system (using an OFDM communication system).

  On the other hand, in Non-Patent Document 2, three types of P-SCHs are arranged so as not to interfere between adjacent cells (3 cell reuse), and accurate acquisition of time synchronization and initial connection information for a desired base station, that is, A P-SCH structure that can perform cell search has also been proposed. In particular, in Non-Patent Document 2, by using the three different P-SCHs among three cells controlled by the same base station, that is, between sectors, the mobile station can select an optimal base station for communication. Proposals to try have been made.

Thus, even in E-UTRA, which is the next generation communication standard, proposals have been made to adopt a technology that follows 3G three-step cell search using SCH.
3GPP contributions “R1-0627222”, “Three-Step Cell Search Method for E-UTRA”, [November 1, 2006], Internet (URL: ftp://ftp.3gpp.org/TSG_RAN/WG1_RL1/TSG1_RL1/TSR1 Docs / R1-0662722.zip) 3GPP contributions “R1-062783”, “SCH Structure and Initial Cell Search Procedure for E-UTRA”, [searched on November 1, 2006], Internet (URL: ftp: //ftp.3gpp.org1/TSG_R1/L1/WSG1/RG/RSG TSGR1_46bis / Docs / R1-062783.zip)

  In the three-stage cell search of E-UTRA shown in Non-Patent Document 1, time synchronization is performed using the P-SCH in the first stage. Time synchronization is generally performed by observing a cross-correlation value between a received signal and a replica signal held in the mobile station. In other words, the mobile station trying to establish time synchronization first observes the transmission timing of the P-SCH, which is a known signal, so that the received signal is the same signal as that transmitted from the base station in the mobile station. The correlation value of the replica signal is calculated. A matched filter (sometimes referred to as a matched filter or a matched filter) is used to observe the correlation value between the received signal and the known replica signal.

  Next, the mobile station determines the point at which the correlation value is highest in a certain time interval (for example, one radio frame) as the time when the P-SCH is received. Usually, the P-SCH is transmitted in a predetermined cycle, and more accurate time synchronization can be performed by averaging in the cycle.

  FIG. 13 is a diagram illustrating a configuration of a general matched filter. In the matched filter, the time-direction signal waveform of the input signal is multiplied by the complex conjugate of the replica signal held on the receiver side. The time direction signal waveform is shifted every sample point, and the correlation value in the time direction is detected. In general, the P-SCH used for timing synchronization of cell search uses a code with good autocorrelation characteristics, and is designed so that a sharp correlation value peak can be obtained when the timing of the matched filter matches. The In the above-described OFDM communication, the same number of multipliers as the number of sampling points in the symbol interval of P-SCH is required, so that a complicated circuit configuration is required when the code length (the number of sampling points) is long.

  In addition, when using a plurality of P-SCHs as proposed in Non-Patent Document 2, generally, the operation of observing the correlation value between the above-mentioned replica signal and the received signal is simultaneously performed on a plurality of replica signals. By performing, it is possible to observe correlation values for a plurality of P-SCH signals. However, since the operation for detecting such a cross-correlation value requires a plurality of correlators to be installed in parallel, the amount of calculation for calculating the correlation value becomes very large. In addition, the circuit for performing this calculation becomes very large, which places a heavy burden on the mobile station. The method using three P-SCHs proposed in Non-Patent Document 2 simply requires three times the calculation amount and circuit scale, that is, three matched filters, which further increases the burden on the mobile station. There's a problem.

  The present invention has been made in view of such circumstances, and establishes time synchronization with downlink OFDMA wireless communication in which three P-SCHs are introduced with the same detection time as in the case of one P-SCH. It is another object of the present invention to provide a receiver, a mobile station, and a base station that can reduce the amount of calculation required for calculating cross-correlation values for time synchronization.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, the receiver of the present invention is a receiver that is applied to a multicarrier communication system, and a receiver that receives a multicarrier signal transmitted from at least one base station and including at least one type of synchronization channel; A synchronization unit that performs time synchronization using at least one common part having different time divisions and the same time waveform among a plurality of types of synchronization channels, and as a result of the time synchronization, a plurality of communication control regions Among the corresponding communication devices, a communication device having an optimum communication characteristic can be selected.

  As described above, time synchronization is performed using at least one common portion having a different time section and the same time waveform among the synchronization channels, and therefore, one symbol-length matched filter is provided by the number of types of synchronization channels. Compared to the above, it is possible to reduce the load of the computation processing of the matched filter.

  (2) Further, in the receiver of the present invention, the synchronization unit calculates a correlation value using at least one common part in which the time segments of the respective synchronization channels are different and the time waveform is the same, and the common part is calculated. A matched filter unit that outputs a correlation value every time, a timing detection unit that detects timing of the synchronization channel based on a correlation value output from the matched filter unit, a correlation value output from the matched filter unit, and the And a determination unit that determines a communication control region with optimal communication characteristics based on the timing detection result output from the timing detection unit.

  With this configuration, it is possible to detect timing for a plurality of types of synchronization channels by inputting a received signal to one matched filter unit. In addition, it is possible to determine and select a communication control region with optimal communication characteristics based on the correlation value and the detected timing.

  (3) In the receiver of the present invention, the matched filter unit is characterized in that time-related correction is performed so that a common part of each synchronization channel belongs to the same time segment.

  With this configuration, a conventionally used matched filter having a symbol length of 1 symbol is used in a short section (number of samples), and, for example, correction is performed by delaying addition, thereby reducing the processing load of the matched filter. It becomes possible.

  (4) In the receiver of the present invention, each synchronization channel has a plurality of common portions that are in a cyclic delay relationship, and the matched filter unit calculates a correlation value for each common portion. A plurality of matched filters, and a correction unit that corrects and adds time relationships of correlation values output from the respective matched filters, are provided.

  In this way, in the matched filter, the correlation value is calculated for each common part of the synchronization channel, and the correction unit corrects (for example, delays and adds) the time relationship of the correlation value. The correlation value of the time direction signal waveform of the cell or sector can be adjusted correctly to be the same.

  (5) Further, the receiver of the present invention is characterized in that the matched filters are arranged in parallel, and the synchronization channels are simultaneously input to the matched filters.

  Thus, in each matched filter arranged in parallel, the correlation value is calculated for each common part of the synchronization channel, and the correction unit corrects the temporal relationship of the correlation value (for example, adds with delay). It can be correctly adjusted to be the same as the correlation value of the time direction signal waveform of the desired communication control region (cell or sector).

  (6) In the receiver according to the present invention, the matched filters are arranged in series, and the synchronization channels are sequentially input to the matched filters.

  In this way, since each matched filter is arranged in series, a signal input to one matched filter is delayed by an internal delay element and then input to the next-stage matched filter. Become. As a result, it is possible to reduce the number of blocks required for delay in the correction unit as compared with the case where matched filters are arranged in parallel. For this reason, when the circuit required for the delay becomes large, it is possible to suppress the expansion of the circuit scale by adopting this form.

  (7) In the receiver of the present invention, each synchronization channel has a plurality of common portions that are in a cyclic delay relationship, and the matched filter units are arranged in series in the order based on the cyclic delay. And a plurality of matched filters that calculate correlation values for each common part, and an adder that adds the correlation values output from the matched filters.

  In this way, a plurality of matched filters are arranged in series in the order based on the cyclic delay, calculate the correlation value for each common part, and add the correlation values output from each matched filter in the adding unit. Thus, it is possible to reduce the number of blocks for delay required after the adder.

  (8) In the receiver of the present invention, the timing detection unit selects a base station having the optimum communication characteristics based on a value obtained by adding a plurality of correlation values corresponding to the plurality of types of synchronization channels. It is characterized by.

  With this configuration, it is possible to select a base station with optimal communication characteristics.

  (9) In the receiver of the present invention, the timing detection unit calculates absolute values of a plurality of correlation values corresponding to the plurality of types of synchronization channels, adds the calculated absolute values, and adds the calculated values. The base station is characterized in that the base station having the optimum communication characteristics is selected.

  With this configuration, it is possible to select a base station with optimal communication characteristics.

  (10) In the receiver of the present invention, the determination unit is based on absolute values of a plurality of correlation values corresponding to the plurality of types of synchronization channels at the timing of the synchronization channel detected by the timing detection unit. It is characterized by determining a communication control area with optimal communication characteristics.

  With this configuration, it is possible to determine a communication control area with optimal communication characteristics.

  (11) Moreover, the mobile station of this invention is provided with the receiver in any one of Claim 1-10. It is characterized by the above-mentioned.

  With this configuration, time synchronization is performed using at least one common portion having a different time segment and the same time waveform among the synchronization channels, so that one matched symbol filter is provided for each synchronization channel type. Compared to the above, it is possible to reduce the load of the computation processing of the matched filter.

  (12) Further, the base station of the present invention is a base station applied to a multicarrier communication system, and differs from the mobile station according to claim 11 in a plurality of common parts having different time segments and the same time waveform. Is characterized by transmitting a multi-carrier signal including a plurality of types of synchronization channels that are in a cyclic delay relationship with each other.

  With this configuration, time synchronization is performed using at least one common portion having a different time segment and the same time waveform among the synchronization channels, so that one matched symbol filter is provided for each synchronization channel type. Compared to the above, it is possible to reduce the load of the computation processing of the matched filter.

  According to the present invention, time synchronization is performed using at least one common portion having different time divisions and the same time waveform among the synchronization channels, so that one symbol-length matched filter is provided by the number of synchronization channel types. Compared with the case where it is provided, it is possible to reduce the load of calculation processing of the matched filter.

  Next, embodiments of the present invention will be described with reference to the drawings. First, basic techniques and basic concepts of multicarrier communication used in the present invention will be described.

(Basic access method)
In the following description, OFDMA is used as the access method. In the OFDMA communication system used in the description of the present invention, it is considered that a base station that controls one cell as three communication control areas (sectors) performs communication simultaneously with a plurality of mobile stations in the cell. A wireless communication frame described below (hereinafter referred to as a frame) is divided into small parts so that it can be used by a plurality of mobile stations (hereinafter, this division unit is referred to as a resource block). The communication speed is improved by assigning to a good mobile station.

  Also, in each sector controlled by one base station, the frame transmission / reception timing is simultaneous, that is, synchronized, and the same frequency band is used as the frequency band to be used. In general, such a communication system that repeatedly uses the same frequency is referred to as a “one-cell repetitive communication system”. A signal used in an adjacent cell or an adjacent sector near a cell boundary and a sector boundary, and a desired received signal Are known to cause interference and decrease in communication speed (throughput).

(Cell search)
Each mobile station has good reception characteristics among a plurality of sectors controlled by a plurality of base stations when communication is started in an environment where a plurality of cells are arranged as described above, that is, reception power of a received signal is low. A sector with a high or high received signal to noise ratio is selected and connected to the base station, and then wireless communication is started. In practice, a plurality of sectors are controlled by the same base station, and a mobile station that wants to communicate selects a transceiver that controls a plurality of one sector as a target of wireless communication (hereinafter, referred to as a wireless communication target). In some cases, the mobile station selects one of the transceivers as a communication target from the transceivers corresponding to a plurality of sectors in the cell controlled by the base station is simply selected as a sector). Such an operation at the start of wireless communication is generally called a cell search. The cell search includes selection of a cell (sector) having good communication characteristics, acquisition of base station information including information such as a cell ID, frame synchronization, and symbol synchronization. As shown in the non-patent document 1, in E-UTRA, a synchronization channel (SCH) is used to execute this cell search, and in particular, P-, which is one of the channels constituting the SCH for performing time synchronization. SCH is used. A detailed description of the P-SCH used in the present invention will be given later.

(Description of frame)
FIG. 1 is a diagram illustrating a downlink frame configuration of an OFDMA communication system used in the present invention. The frame configuration is the same as the general frame configuration used in the OFDMA communication system as shown in FIG. That is, a configuration is used in which a certain time interval (frame interval) is divided into a plurality of frequencies and the frequency domain is also divided into a certain bandwidth composed of a plurality of subcarriers. These divided areas are referred to as resource blocks in this specification. In general, a unit obtained by dividing a frame in the time domain is called a subframe (SF), and a unit divided in the frequency domain may be called a subchannel (SC).

  In FIG. 1, the frequency axis direction is composed of six frequency resource blocks SC1 to SC6 and the time axis direction is composed of ten subframes SF1 to SF10. However, the block division number and the block size are not limited to this. Also, each mobile station uses these blocks in common, and each block is scheduled to a mobile station with a good propagation path environment, in particular, in order to improve communication characteristics (throughput). Further, when there are a plurality of mobile stations performing communication with a small amount of data, it is possible to further divide and share one resource block.

(Description of SCH)
Next, the synchronization channel (SCH) in the OFDMA communication of the present invention will be described. Various studies have been made on the SCH in the OFDMA communication system. In the present invention, the description will be made on the assumption that the three P-SCHs shown in the system of Non-Patent Document 2 are applied. The SCH shown in Non-Patent Document 2 is composed of P-SCH and S-SCH. The P-SCH focused in the present invention is a channel used for time synchronization and frequency synchronization of a mobile station at the time of cell search. It is. Further, as will be described later, by using three types of P-SCH in a one-to-one correspondence with the sector number, it is possible to use the sector number for determination.

  As described above, different P-SCHs are transmitted between sectors controlled by the same base station, as described above. As for the P-SCH, three types of P-SCH correspond to the sectors 1 to 3 on a one-to-one basis as shown in the cell arrangement shown in FIG. For example, P-SCHs transmitted at the same timing reach a mobile station almost at the same time to a mobile station located in an area close to a plurality of sectors such as the vicinity of a sector boundary, such as the mobile station in FIG. Since different P-SCHs are transmitted, it is possible to select a desired sector and perform time synchronization using the P-SCH transmitted in the desired sector.

  As shown in FIG. 2, a base station (base station a to base station c) is installed at the center of one cell (cell a to cell c), and each cell (cell a to cell c) has 3 It is divided into one sector (sector 1 to sector 3). Each base station is provided with a plurality (three in this case) of communication devices corresponding to the sector, and the communication device communicates with the mobile stations existing in the sector. Each cell has a plurality of mobile stations (mobile station 1 and the like), and each mobile station selects a sector with the highest reception quality and performs wireless communication with a communication apparatus corresponding to the sector. P-SCH can be used for sector selection. In the example of FIG. 2, P-SCH from sector 1 and sector 2 of cell a is expected to be observed most strongly, and communication with cell a can be performed by performing time synchronization with these P-SCHs. . Thus, it is necessary to perform a cell search in order to select and connect a sector having the best communication quality from a plurality of sectors.

(Description of P-SCH)
FIG. 3 shows a time synchronization channel (P-SCH) of the multicarrier communication system used in the present invention. In this specification, it is assumed that P-SCH is arranged in the last symbol of SF10 that is the tenth subframe. The arrangement of the P-SCH in the time direction is assumed to be known to all mobile stations in advance or in advance by some means. Further, it is assumed that correlation values are arranged at the same position in consecutive frames and the correlation values for performing timing synchronization in the frame period can be averaged. However, the arrangement used in this specification is not necessarily limited to this, and the time synchronization of cell search can be achieved by arranging one symbol in a frame or an arrangement having periodicity once every several frames. Can be performed.

(Configuration of frequency direction of P-SCH)
FIG. 4 shows an example of the configuration of the P-SCH in the frequency direction. The P-SCH data is allocated to 72 subcarriers, which are composed of 73 subcarriers, except for the subcarrier whose center index is 0. The center subcarrier (DC subcarrier) is used as a null subcarrier (a subcarrier to which power and data are not allocated). In order to create three P-SCHs, phase rotation θ as shown in FIG. 4 is performed between adjacent subcarriers. As an example, θ is 0 in sector 1, π / 2 in sector 2, and π in sector 3.

  FIG. 5 shows a time direction waveform of the P-SCH symbol of each sector when the phase rotation θ used in this specification is applied. By applying a phase rotation of θ, a time waveform in which a cyclic delay of θ / (2π) symbols is applied in each sector is formed. The configuration in the frequency domain of P-SCH as described above is an example, and the configuration is not necessarily limited to such a configuration. The present invention is based on the assumption that a plurality of P-SCHs are in a cyclic delay relationship in the time domain, and the configuration of each of the plurality of P-SCHs is that the signal waveforms in the time domain are cyclic delays. Any configuration is acceptable.

  In the embodiment described below, the time synchronization method of the mobile station and the optimum sector determination procedure are shown based on the transmission method described above. The number of sectors is 3, that is, three types of P-SCH are transmitted, and phase rotation θ of 0, π / 2, and π is applied, respectively.

  The present invention realizes a matched filter with reduced computational complexity without degrading the characteristics of cell search performance using three P-SCHs of downlink OFDMA wireless communication transmitted under such preconditions. An object is to perform time synchronization in cell search. In addition, by installing the matched filter of the present invention in a mobile station, it is possible to determine the optimum cell (sector) at a higher speed with less power consumption of the mobile station due to the effect of reducing the amount of calculation at the time of cell search. Become.

(First embodiment)
FIG. 6 is a block diagram showing an example of a receiver applicable to the mobile station (including a mobile phone terminal, a PDA terminal, and a portable personal computer) according to the present invention. As illustrated in FIG. 6, the mobile station receiver 10 includes an antenna unit 11, an analog circuit unit 12, an A / D conversion unit 13, a synchronization unit 14, and a GI (Guard Interval) removal unit. 15, an S / P (serial / parallel) converter 16, and an FFT unit 17. Further, a channel estimation / equivalence unit 18, a demodulation / decoding unit 19, and a MAC unit 20 are provided.

  The receiver 10 detects the P-SCH timing from the received signal in order to perform time synchronization with the signal transmitted from the base station. That is, the radio signal transmitted from the base station is received by the antenna unit 11, the received radio signal is converted from the radio frequency band to the baseband frequency band by the analog circuit unit 12, and the signal converted to the baseband frequency band Is converted by an A / D (analog / digital) converter 13 that converts analog signals into digital signals.

  Next, P-SCH is detected from the received data converted into digital data by the A / D converter 13 and a P-SCH detection process is performed by the synchronization unit 14 (timing detection unit included therein) in order to perform symbol synchronization. Apply. Here, an example of a block configuration for symbol synchronization will be described.

  FIG. 7 is a block diagram illustrating a configuration of the synchronization unit. As shown in FIG. 7, the synchronization unit 14 includes a matched filter unit 71, a timing detection unit 72, and an optimum sector determination unit 73. As is clear from this configuration, the synchronization unit 14 can detect the timings for the three P-SCHs by inputting the received signal to one matched filter unit 71, and the three sectors. The optimum sector can be selected by comparing the three outputs of the matched filter section. The detailed configuration of the matched filter is shown in the second and subsequent embodiments. In the present embodiment, since the P-SCH is arranged at the last symbol of the frame, the frame synchronization is performed simultaneously with the symbol synchronization.

  Returning to FIG. 6, the description of the receiving operation will be continued. After the symbol synchronization is completed, processing can be continuously performed including the subsequent data symbols in accordance with the symbol period described above. The GI removal unit 15 removes the GI added before the effective symbol from each symbol. The symbol from which GI has been removed is converted from a serial signal to a parallel signal by an S / P (serial / parallel) converter 16 and subjected to FFT processing by an FFT unit 17. However, the GI length is assumed to be known to the mobile station.

  The signal output from the FFT unit 17 is sequentially input to the channel estimation / equivalent unit 18, the demodulation / decoding unit 19, and the MAC unit 20, and subsequent processing such as data demodulation and decoding is performed. The receiver 10 also performs demodulation and decoding processing on the data other than P-SCH at the timing described above. When the mobile station makes an initial connection to the base station, it is common to preferentially process the SCH signal because initial parameters such as cell information and sector information are not acquired.

  The timing synchronization is performed as described above, and the FFT-processed received data is sequentially sent to the channel estimation / equivalent unit 18, the demodulation / decoding unit 19, and the MAC unit 20. Thereby, information necessary for connection with the base station can be obtained from the SCH signal.

  Next, the operation of “timing synchronization and optimum sector determination” performed by the OFDM receiver 10 configured as described above will be described with reference to the flowchart shown in FIG. FIG. 8 is a flowchart showing an example of main procedures of cell search time synchronization and sector determination processing according to the present invention.

  First, a mobile station (including a mobile phone terminal, a PDA terminal, and a portable personal computer) receives an OFDM signal from the base station and performs frequency conversion and A / D conversion (step S10). Next, symbol synchronization and frame synchronization are established by detecting the correlation with the received signal using a matched filter (step S11). Furthermore, the optimum sector is determined by comparing the correlation value observed by the matched filter at the P-SCH timing detected in the previous step between the P-SCHs corresponding to each sector (step S12). Subsequently, GI removal (step S13) and data demodulation are performed (step S14).

  The receiver according to the present embodiment can perform subsequent processing based on the sector specific information corresponding to the P-SCH determined as the optimum sector during the data demodulation and SCH symbol demodulation / decoding processing. Further, even when the reference signal for data demodulation is sector specific, it is possible to select the reference signal based on information from the optimum sector determination unit and use it for data demodulation.

(Second Embodiment)
In the present embodiment, the cell search method including time synchronization and optimum sector determination is more specifically described by taking the case where the P-SCH is arranged at the rear end of the last subframe constituting the frame as in the previous embodiment. I will explain it.

  The cellular system (mobile communication system composed of a plurality of cells) used in this embodiment is a one-cell repetitive communication system in which each cell uses the same frequency band and the OFDMA communication method is used as a communication method. In addition, as shown in FIG. 2, the cell is divided into three communication areas (sectors), and one base station installed at the center of the cell performs wireless communication with mobile stations located in a plurality of sectors. Do. The downlink communication method is the same OFDM communication method as described above. The resource block configuration in which the communication frame and the P-SCH are arranged has the same format as that shown in FIGS. 1 and 3, respectively.

  In the present embodiment, a plurality of P-SCH signals transmitted from each sector have a one-to-one correspondence with the sector index (sector number), and the P-SCH of each sector is transmitted at the same time, and is transmitted by the same base station. It is assumed that a CDM (Code Division Multiplex: hereinafter simply referred to as “CDM”) in which the P-SCH of the controlled sector is multiplied by the phase rotation code is transmitted. The multiplication method of the phase rotation code has the same format as that shown in FIG. The mobile station performs time synchronization with the base station based on the P-SCH signal from the base station, and can determine the optimum sector based on the correlation value calculated for time synchronization.

  In this embodiment, a procedure for performing time synchronization and optimum sector determination using a P-SCH signal transmitted from a base station will be described, but the basic operation follows the procedure shown in the first embodiment. In particular, a detailed description will be given of the synchronization unit of the mobile station.

  FIG. 7 shows the synchronization unit 14 of the mobile station in the present embodiment. As in the first embodiment, the synchronization unit 14 includes a matched filter unit 71, a timing detection unit 72, and an optimum sector determination unit 73. When the received signal is input to the matched filter unit 71, a correlation value corresponding to each sector is calculated. FIG. 9 shows details of the matched filter unit 71 shown in FIG.

  As described above, when it is desired to calculate correlation values for three types of P-SCHs, three matched filters of 1 symbol length are usually required in parallel. However, in the present invention, attention is paid to the fact that P-SCH is CDMed by an orthogonal code of phase rotation, and the feature that the time direction waveform is a cyclic delay is utilized. By using a normal 1-symbol matched filter in a short interval (number of samples) and adding after delay, it is possible to reduce the processing load of the matched filter. Specifically, by using four matched filters having a length of ¼ of the symbol length in parallel, time synchronization with three P-SCH signals having a cyclic delay relationship is attempted. . The 1/4 symbol that is a division unit of the matched filter in the present embodiment is a value determined in association with θ multiplied by the transmission P-SCH. In other words, when a value other than the three values of 0, π / 2, and π used in the present embodiment is used for the relationship between P-SCH subcarriers, the unit of division is changed and configured. Can be done.

MF _n (n is a positive integer) in FIG. 9 is a block for calculating a correlation value corresponding to each part obtained by dividing the P-SCH symbol by 1 / n. In the present embodiment, since the minimum delay difference is 1/4 symbols of sector 1 and sector 2, n = 4 is set, and four blocks MF ₁ to MF ₄ are configured. MF ₁ is a block corresponding to waveform 1 of the time waveform of the P-SCH symbol shown in FIG. 5, and MF ₂ , MF ₃ , and MF ₄ are also for calculating correlation values corresponding to waveform 2, waveform 3, and waveform 4, respectively. It is a block.

The output values from each correlation value calculating block MF _n is added after having been subjected to the desired delay through the delay element. In addition processing, blocks corresponding to each sector are prepared, and the amount of delay applied to each block is different. In the present embodiment, the delay element D _1n shown in FIG. 9 is a block for outputting a value delayed by an integral multiple of a delay amount (D _S ) of ¼ symbol time. That is, the correlation value obtained when the three P-SCH time waveforms shown in FIG. 5 are received is calculated for each ¼ symbol, and the overall correlation value is calculated. It is added after being correctly adjusted to be the same as the correlation value of the time direction signal waveform of the sector.

For example, in FIG. 9, if the signal shown in FIG. 5 is input, the following operation is performed before the signal for sector 1 is output. When the signal of FIG. 5 is received by the receiver of the mobile station, it is converted into digital data by the A / D converter and then input to the matched filter unit. The signal shown in FIG. 5 is input to the matched filter unit from the beginning of the P-SCH symbol, that is, from the left end of the figure. In the matched filter shown in FIG. 9, the input signal is sequentially input to each of MF ₁ to MF ₄ for each sampling point. At the time when a signal corresponding to the first ¼ symbol of P-SCH is input, the correlation value calculated from MF ₁ to MF ₄ increases depending on the received power values of P-SCHa to P-SCHc. For example, when the received power of the P-SCH symbol in sector 1 is relatively higher than the received power of the P-SCH symbol in other sectors, the correlation value of waveform 1 corresponding to the first 1/4 symbol of P-SCHa matched filter portion for detecting, that is, that the output of the MF ₁ increases. On the other hand, although high signal from the MF ₂ received power of the first quarter symbol of similarly sectors 1 to MF ₄ is input, the MF ₄ from MF ₂ high correlation value is not detected.

Next, consider the second quarter symbol interval. Here a quarter symbol time interval and _{D s.} As described above, considering the case where the received power of the signal of sector 1 is strong, the output from the matched filter corresponding to waveform 2 becomes high. That is, the output of MF ₂ increases after D _s time after the above-described peak at MF ₁ is detected.

Similarly, output values from MF ₃ and MF ₄ corresponding to waveform 3 and waveform 4 of sector 1 are observed after 2 × D _s and 3 × D _s hours with reference to the peak observation time in MF ₁ described above. Will be. Therefore, in order to align and add the times of these peaks, the output of MF ₁ is 3 × D _s , the output of MF ₂ is 2 × D _s , the output of MF ₃ is 1 × D _s , and the output of MF ₄ is unchanged. By adding, the same result as that obtained when the correlation value is calculated for the waveform of the entire P-SCH symbol in sector 1 can be obtained.

In the present embodiment, although the four prepared correlation value calculating block MF _n, waveform 1 and waveform 2 corresponding to MF ₁ and MF ₂ As is clear from FIG 5 the time waveform of each sector In any case, since it is continuous, it is not always necessary to use another block. That is, it is also possible to configure a correlation value calculation block that combines MF ₁ and MF ₂ .

Next, FIG. 10 shows a general circuit configuration for the MF _n shown in FIG. However, in this embodiment, the number of points per symbol is 128 points. The example shown in FIG. 10 shows a circuit that multiplies a general input signal by a complex conjugate signal of a signal for which a correlation value is desired to be calculated, and calculates a sum. In addition to this, there is a case where a correlation value is calculated only by sign inversion and addition in order to reduce the amount of calculation without performing complex calculation. However, the present invention is not a method for particularly limiting the method of calculating the correlation value. Therefore, an example of multiplying a general complex conjugate is shown here. (A) to (d) shown in FIG. 10 show circuits for calculating correlation values of signals corresponding to waveform 1 to waveform 4, respectively.

  Returning to FIG. 7, the description will be continued. The correlation value corresponding to each sector output from the matched filter unit 71 is input to the timing detection unit 72 and the optimum sector determination unit 73. The timing detector 72 detects the timing of the P-SCH symbol from the three correlation values. For example, in a multi-cell environment in which sectors controlled by the same base station are synchronized, when it is desired to select an optimal base station, that is, when any sector controlled by the optimal base station is not limited, three correlations are used. The sum of the values is calculated, and the time with the highest value in one frame time interval is detected as the P-SCH timing. When high-precision detection is desired, the noise is reduced by averaging one frame time interval over several frames. When summing three correlation values, there are a method of adding complex correlation values as they are to obtain an absolute value, and a method of adding absolute values.

  In the present embodiment, frame synchronization can also be performed simultaneously by detecting P-SCH symbol timing arranged at the same time period as the frame.

  Next, the timing detection unit 72 notifies the optimum sector determination unit 73 of the P-SCH symbol timing. The optimum sector determination unit 73 selects the optimum sector from the correlation value at the notified time. The optimum sector is selected by comparing the absolute values of the three correlation values, and the sector having the highest correlation value is usually selected as the optimum sector.

  As described above, P-SCH symbol timing, that is, symbol timing, frame timing information, and optimum sector information are used for subsequent control from the GI removal unit 15 to the MAC unit 20. Since GI removal and data demodulation are general OFDM reception methods, description thereof is omitted.

(Third embodiment)
In this embodiment, as in the case of the second embodiment, the case where the P-SCH is arranged at the rear end of the last subframe constituting the frame is taken as an example. A cell search method including sector determination will be described.

  In this embodiment, the cellular system (mobile communication system composed of a plurality of cells) used in the same manner as in the second embodiment uses the same frequency band for each cell, and uses the OFDMA communication method as the communication method. It is the 1-cell iterative communication system used. The preconditions of the communication system shown in FIGS. 1, 2 and 3 are based on the second embodiment. Also in this embodiment, a plurality of P-SCH signals transmitted from each sector correspond to a sector index (sector number) on a one-to-one basis, and the P-SCH of each sector is transmitted at the same time, and is transmitted by the same base station. It is assumed that CDM transmission in which the P-SCH of the sector to be controlled is multiplied by the phase rotation code is transmitted. The multiplication method of the phase rotation code has the same format as that shown in FIG.

  FIG. 7 shows the synchronization unit of the mobile station in the present embodiment. As in the second embodiment, the synchronization unit 14 includes a matched filter unit 71, a timing detection unit 72, and an optimum sector determination unit 73. When the received signal is input to the matched filter unit 71, a correlation value corresponding to each sector is calculated.

  FIG. 11 shows details of the matched filter unit 71 shown in FIG. As described above, when it is desired to calculate correlation values for three types of P-SCHs, three matched filters of 1 symbol length are usually required in parallel. However, in the present invention, attention is paid to the fact that the P-SCH is CDMed by an orthogonal code of phase rotation, and the feature that the waveform in the time direction is a cyclic delay is used. By using a normal 1-symbol matched filter in a short interval (number of samples) and adding after delay, it is possible to reduce the processing load of the matched filter. Specifically, four matched filters having a length of ¼ of the symbol length are used in series, and appropriate delays are added to the respective outputs and added, to thereby add three P-SCH signals having a cyclic delay relationship, It is intended to synchronize the time.

MF _n (n is a positive integer) in FIG. 11 is a block for calculating a correlation value corresponding to each part obtained by dividing the P-SCH symbol by 1 / n. Also in this embodiment, since n = 4 as in the second embodiment, the block is composed of four blocks MF ₁ to MF ₄ .

The output values from each correlation value calculating block MF _n is added after having been subjected to the desired delay through the delay element. In addition processing, blocks corresponding to each sector are prepared, and the amount of delay applied to each block is different. In the present embodiment, the delay element k * D _S shown in FIG. 11 is a block for outputting a value that is delayed by an integer (k) times the delay amount (D _S ) of ¼ symbol time. . That is, the correlation value obtained when the three P-SCH time waveforms shown in FIG. 5 are received is calculated for each ¼ symbol, and the overall correlation value is calculated. It is added after being correctly adjusted to be the same as the correlation value of the time direction signal waveform of the sector. The block MF _n correlation value calculation are connected in series, the input signal, after being subjected to through delaying internal delay elements is output is input to the next stage of MF _n.

For example, in FIG. 11, if the signal shown in FIG. 5 is input, the following operation is performed before the signal for sector 1 is output. When the signal of FIG. 5 is received by the receiver of the mobile station, it is converted into digital data by the A / D converter and then input to the matched filter unit. The signal shown in FIG. 5 is input to the matched filter unit from the beginning of the P-SCH symbol, that is, from the left end of the figure. In the matched filter shown in FIG. 11, the input signal is input to MF ₄ at every sampling point, and the signal output from MF ₄ is connected to MF ₃ , so that the received signal output from MF ₄ is immediately is input to the MF ₃ in. Subsequently MF _2, MF ₁ also matched filter are connected in series, the correlation value is input to each is calculated. When a signal corresponding to the first 1/4 symbol of P-SCH is input, the correlation value calculated in MF ₄ is calculated from the received power values of P-SCHa to P-SCHc.

For example, when the received power of the P-SCH symbol in sector 1 is relatively higher than the received power of the P-SCH symbol in other sectors, waveform 1 and MF ₄ corresponding to the first 1/4 symbol of P-SCHa However, since MF ₄ is a matched filter having a high correlation value in waveform 4, a high peak is not observed in this case. Next, the signal output from MF ₄ is input to MF ₃ , but in this case, a high peak is not observed. In this way, since in the case the signal of the sector 1 is strong matching MF corresponding to the respective quarter wave when the P-SCH symbol is one symbol input, adding without delaying them with sigma _S1 By doing so, the peak of the correlation value can be observed.

The feature of this embodiment is that the number of blocks required for the delay is smaller than that of the second embodiment, and therefore this embodiment is used when the circuit required for the delay element becomes large. Is desirable. Although prepared four correlation value calculation block MF _n in this embodiment, as in the second embodiment, the waveform 1 and waveform 2 corresponding to MF ₁ and MF ₂ is any of the time waveform of each sector Even in this case, since it is continuous, it is not always necessary to use another block. That is, it is also possible to configure a correlation value calculation block that combines MF ₁ and MF ₂ .

A general circuit configuration for the MF _n shown in FIG. 11 is the configuration shown in FIG. 10 as in the first embodiment. Also in this embodiment, the number of points per symbol is 128 points.

(Fourth embodiment)
In this embodiment, as in the case of the second embodiment, the case where the P-SCH is arranged at the rear end of the last subframe constituting the frame is taken as an example. A cell search method including sector determination will be described.

  In this embodiment, the cellular system (mobile communication system composed of a plurality of cells) used in the same manner as in the second embodiment uses the same frequency band for each cell, and uses the OFDMA communication method as the communication method. It is the 1-cell iterative communication system used. The preconditions of the communication system shown in FIGS. 1, 2 and 3 are based on the second embodiment.

  Also in this embodiment, a plurality of P-SCH signals transmitted from each sector correspond to a sector index (sector number) on a one-to-one basis, and the P-SCH of each sector is transmitted at the same time, and is transmitted by the same base station. It is assumed that CDM transmission in which the P-SCH of the sector to be controlled is multiplied by the phase rotation code is transmitted. The multiplication method of the phase rotation code has the same format as that shown in FIG.

  FIG. 7 shows the synchronization unit of the mobile station in the present embodiment. As in the third embodiment, the synchronization unit 14 includes a matched filter unit 71, a timing detection unit 72, and an optimal sector determination unit 73. When the received signal is input to the matched filter unit 71, a correlation value corresponding to each sector is calculated. FIG. 12 shows details of the matched filter unit 71 shown in FIG. As described above, when it is desired to calculate correlation values for three types of P-SCHs, three matched filters of 1 symbol length are usually required in parallel. However, in the present invention, attention is paid to the fact that the P-SCH is CDMed by the orthogonal code of the phase rotation, and the feature that the waveform in the time direction is a cyclic delay is used.

  By using a normal 1-symbol matched filter in a short interval (number of samples) and adding after delay, it is possible to reduce the processing load of the matched filter. Specifically, four matched filters having a length of ¼ of the symbol length are used in series, and appropriate delays are added to the respective outputs and added, to thereby add three P-SCH signals having a cyclic delay relationship, It is intended to synchronize the time.

  The feature of this embodiment is a method that requires the least number of delay blocks since the delay blocks are arranged after the block for calculating the sum of the sectors.

MF _n (n is a positive integer) in FIG. 12 is a block for calculating a correlation value corresponding to each part obtained by dividing the P-SCH symbol by 1 / n. Also in this embodiment, since n = 4 as in the second embodiment, it is composed of four types of blocks MF ₁ to MF _4. However, the difference from the previous embodiment is the correlation value obtained by summing up each sector. MF ₃ and MF ₄ are repeatedly used so that a delay block is not required before calculating.

The output values from each correlation value calculating block MF _n after being added without passing through the delay element, the delay by the delay block to align the relative time of the correlation values between each sector is performed. In addition processing, blocks corresponding to each sector are prepared, and the amount of delay applied to each block is different. Also in the present embodiment, the delay element k * D _S shown in FIG. 12 is a block for outputting a value delayed by an integer (k) times the delay amount (D _S ) of ¼ symbol time. is there. That is, after calculating the correlation values obtained when receiving the three P-SCH time waveforms shown in FIG. 5 at different timings, the delay block is used to align the correlation values of the sectors in time. Has been placed.

For example, in FIG. 12, if the signal shown in FIG. 5 is input, the following operation is performed before the signal for sector 1 is output. When the signal of FIG. 5 is received by the receiver of the mobile station, it is converted into digital data by the A / D converter and then input to the matched filter unit. The signal shown in FIG. 5 is input to the matched filter unit from the beginning of the P-SCH symbol, that is, from the left end of the figure. In the matched filter shown in FIG. 12, the input signal is input to MF ₄ at every sampling point, and the signal output from MF ₄ is connected to MF ₃ , so that the received signal output from MF ₄ is immediately is input to the MF ₃ in.

Subsequently, a matched filter connected in series to MF ₂ , MF ₁ , and again MF ₄ , MF ₃ is input and a correlation value is calculated. When a signal corresponding to the first 1/4 symbol of P-SCH is input, the correlation value calculated in MF ₄ is calculated from the received power values of P-SCHa to P-SCHc. For example, when the received power of the P-SCH symbol in sector 1 is relatively higher than the received power of the P-SCH symbol in other sectors, waveform 1 and MF ₄ corresponding to the first 1/4 symbol of P-SCHa However, since MF ₄ is a matched filter having a high correlation value in waveform 4, a high peak is not observed in this case.

Next, the signal output from MF ₄ is input to MF ₃ , but in this case, a high peak is not observed. In this way, since in the case the signal of the sector 1 is strong matching MF corresponding to the respective quarter wave when the P-SCH symbol is one symbol input, adding without delaying them with sigma _S1 By doing so, the peak of the correlation value can be observed. Against it, sector 2, respectively 1/4 symbol if you want to observe the correlation value of the signal waveform of the sectors 3, 1/2 symbol time interval (each _{1 × D s, 2 × D} s) the correlation value after the lapse since There are observable, finally block for the delay of 2 × D _s in the case of sector 1 after Σ to compare the correlation value for each sector in one symbol, 1 × D _s is the sector 2 Arrange blocks for delays.

The feature of this embodiment is that fewer blocks are required for delay compared to the third embodiment. However, since the arranged overlapping blocks MF _n to calculate the correlation value, it is necessary to consider these circuit scale and the actual power consumption.

A general circuit configuration for the MF _n shown in FIG. 12 is the configuration shown in FIG. 10 as in the first embodiment. Also in this embodiment, the number of points per symbol is 128 points.

  In the above description, the case where the time waveform shown in FIG. 5 is a cyclic delay in each time segment is taken up, but the present invention is not limited to this. The time waveform does not necessarily have a cyclic delay relationship, and may be arranged at random as long as the time division is different among a plurality of synchronization channels.

It is a figure which shows the frame structure of the downlink of an OFDMA communication system used by this invention. It is a figure which shows cell arrangement | positioning. 1 shows a time synchronization channel (P-SCH) of a multicarrier communication system used in the present invention. An example of the structure of the frequency direction of P-SCH is shown. It is a time direction waveform of the P-SCH symbol of each sector when phase rotation θ is applied. It is a block diagram which shows an example of the receiver applicable to the mobile station (a mobile telephone terminal, a PDA terminal, and a portable personal computer) of this invention. It is a block diagram which shows the structure of a synchronizer. It is a flowchart which shows the operation | movement of the timing synchronization and optimal sector determination which an OFDM receiver performs. It is a figure which shows the detail of the matched filter part 71 shown in FIG. It is a figure which shows the general circuit structure of a matched filter. It is a figure which shows the detail of the matched filter part shown in FIG. It is a figure which shows the detail of the matched filter part shown in FIG. It is a figure which shows the structure of a general matched filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Receiver 11 Antenna part 12 Analog circuit part 13 A / D conversion part 14 Synchronization part 15 GI (Guard Interval) removal part 16 S / P conversion part 17 FFT part 18 Channel estimation / equivalent part 19 Demodulation / decoding part 20 MAC part 71 Matched Filter Unit 72 Timing Detection Unit 73 Optimal Sector Determination Unit D _1n Delay Element MF _n Each Correlation Value Calculation Block

Claims (12)

A receiver applied to a multi-carrier communication system,
A receiver for receiving a multicarrier signal transmitted from at least one base station and including at least one type of synchronization channel;
A synchronization unit that performs time synchronization using at least one common part having different time divisions and the same time waveform among a plurality of types of synchronization channels,
As a result of the time synchronization, a receiver capable of selecting a communication device having an optimum communication characteristic among communication devices corresponding to a plurality of communication control areas can be selected. The synchronization unit is
A matched filter unit that calculates a correlation value using at least one common part having a different time division of each synchronization channel and the same time waveform, and outputs a correlation value for each common part; and
A timing detection unit that detects timing of the synchronization channel based on a correlation value output from the matched filter unit;
2. A determination unit that determines a communication control region having an optimum communication characteristic based on a correlation value output from the matched filter unit and a timing detection result output from the timing detection unit. The listed receiver.   3. The receiver according to claim 2, wherein the matched filter unit corrects the time relationship so that a common part of each synchronization channel belongs to the same time segment. Each of the synchronization channels has a plurality of common parts each having a cyclic delay relationship;
The matched filter section is
A plurality of matched filters for calculating a correlation value for each common part;
The receiver according to claim 3, further comprising: a correction unit that corrects and adds a time relationship between correlation values output from the matched filters.   5. The receiver according to claim 4, wherein the matched filters are arranged in parallel, and the synchronization channels are simultaneously input to the matched filters.   5. The receiver according to claim 4, wherein the matched filters are arranged in series, and the synchronization channels are sequentially input to the matched filters. Each of the synchronization channels has a plurality of common parts each having a cyclic delay relationship;
The matched filter section is
A plurality of matched filters arranged in series in an order based on the cyclic delay and calculating a correlation value for each common part;
The receiver according to claim 2, further comprising: an addition unit that adds the correlation values output from the matched filters.   8. The timing detector according to claim 2, wherein the timing detector selects a base station having optimal communication characteristics based on a value obtained by adding a plurality of correlation values corresponding to the plurality of types of synchronization channels. The receiver in any one.   The timing detector calculates absolute values of a plurality of correlation values corresponding to the plurality of types of synchronization channels, adds the calculated absolute values, and determines a base station with optimal communication characteristics based on the added values. The receiver according to claim 2, wherein the receiver is selected.   The determination unit determines a communication control region with optimal communication characteristics based on absolute values of a plurality of correlation values corresponding to the plurality of types of synchronization channels at the timing of the synchronization channel detected by the timing detection unit. 10. The receiver according to claim 8 or 9, wherein:   A mobile station comprising the receiver according to claim 1. A base station applied to a multi-carrier communication system,
For the mobile station according to claim 11,
A base station that transmits a multicarrier signal including a plurality of types of synchronization channels in which a plurality of common portions having different time segments and the same time waveform are in a cyclic delay relationship with each other.

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