JP5595952B2 - Cell search apparatus and method, and mobile station - Google Patents

Description

  The present invention relates to a technical field of a cell search apparatus that performs a cell search for a communication destination base station or the like in a mobile station or the like that performs wireless communication.

  As a technology related to a cell search apparatus, a measurement set by a base station in communication when a mobile station performs cell search or measurement of received power for a base station in a band different from the frequency band of the base station in communication A different frequency cell search using a predetermined time interval called Gap is known.

  The Measurement Gap is a section that is set by a communicating base station and is a so-called non-transmission section in which data transmission from the base station to the mobile station stops. In the Measurement Gap, the mobile station performs another cell search from a communication frequency band (hereinafter simply referred to as a communication band) of a base station that is communicating with a reception frequency band (hereinafter simply referred to as a reception band). By changing to the communication band of the station, cell search is performed, and SCH (Synchronization Channel) data transmitted from the other base station is detected.

  The SCH is a downlink common channel and includes a P-SCH (Primary Synchronization Channel) and an S-SCH (Secondary Synchronization Channel). For example, in the prior art documents described later, P-SCH and S-SCH in a communication system such as LTE (Long Term Evolution) are described.

  For example, in Frame structure type 2 of the LTE system, a synchronization signal PSS (Primary Synchronization Signal) in P-SCH includes a sequence common to all cells. This series of data is used in the mobile station for timing synchronization during cell search. A synchronization signal SSS (Secondary Synchronization Signal) in S-SCH includes transmission parameters unique to each cell such as a cell number and scrambling code information. When the mobile station starts communication with the base station, the mobile station synchronizes timing by receiving the PSS, and acquires transmission parameters that differ from cell to cell by receiving the SSS based on the synchronization timing. Specifically, since PSS and SSS are transmitted in a common period separated by a predetermined number of symbols according to the frame structure and transmission format for each system, the mobile station receives SSS by receiving PSS. Synchronization is possible. Thereby, the mobile station can start communication with the base station.

  Prior art documents shown below include a method for detecting a cell-specific number by performing a correlation operation on a plurality of SSS candidates using the reception timing acquired from the PSS, and a channel estimation value acquired from the PSS. A method of performing SCH channel compensation is described.

  In such channel estimation and channel compensation, the mobile station can improve the cell search performance by accurately estimating the channel state of the S-SCH. For this reason, when the channel state changes according to time due to the influence of fading or the like, it is desirable to perform channel estimation using a PSS transmitted periodically that is closer to the SSS targeted for detection processing. It is said.

JP2009-89185A

3GPP TS 36.211 v8.9.0 3GPP TS36.133 v8.10.0

  In order to perform the above-described different frequency cell search, the mobile station detects the SCH data by switching the reception band from the communication band of the communicating base station to the communication band of the base station performing the cell search in the Measurement Gap. Again, it is necessary to switch the reception band to the communication band of the communicating base station. At this time, in a period in which the reception band is changed, such as the beginning and end of the Measurement Gap, the mobile station may be in a band switching transient state, and the signal reception level may deteriorate.

  Depending on the relationship between the Measurement Gap set in the base station and the transmission timing of the SCH data for the different frequency cell search, the mobile station can receive the SCH data during the period near the beginning or end of the Measurement Gap. There is sex. At this time, there is a technical problem that the cell search performance in the mobile station deteriorates due to the influence of the band switching transient state.

  Such band switching time and band stability after switching often depend on the RF performance of the mobile station. To achieve high performance, cost increases due to the use of expensive parts, and complexity Demerits such as an increase in power consumption due to use of various processes may occur.

  In view of the above technical problems, an object of the present invention is to provide a cell search apparatus and method, and a mobile station, which enable different frequency cell search with relatively simple processing.

  In order to solve the above-described problem, the disclosed cell search apparatus communicates with one cell at a predetermined frequency, and is different from the one cell by switching the reception frequency to a frequency different from the predetermined frequency in a specific time interval. This is a cell search device in a mobile station that performs cell search of another cell. The cell search device includes a reception unit, a first detection unit, a synchronization signal selection unit, and a second detection unit.

  The reception unit receives a signal including a first synchronization signal that is a candidate for a signal used for specifying another cell in a specific time interval. The first detection unit detects reception timing of the first synchronization signal. The synchronization signal selection unit determines a reception timing of a signal used for specifying another cell included in the signal based on the reception timing of the first synchronization signal within a specific time interval. A 2nd detection part specifies another cell using the signal used for the specification of the other cell acquired based on the determined reception timing.

  According to the above configuration, in a mobile station that performs a different frequency cell search, it is possible to avoid cell search performance deterioration due to a transient state when switching the reception frequency at the beginning and end of a specific time interval, and to perform an appropriate cell search It becomes.

It is a figure which shows the radio | wireless communication network containing the mobile station which has a cell search apparatus, and a base station. It is a block diagram which shows the structural example of a cell search apparatus. It is a block diagram which shows the structure of a PSS detection part. It is a block diagram which shows the structure of a SSS detection part. It is a figure which shows the aspect of the different frequency cell search using Measurement Gap. It is a figure which shows the synchronizing signal in the received signal in Measurement Gap. It is a figure which shows the mode of the selection of a synchronizing signal. It is a figure which shows the mode of the selection of a synchronizing signal. It is a figure which shows the mode of the selection of a synchronizing signal. It is a figure which shows the mode of the selection of a synchronizing signal. It is a block diagram which shows the modification of a cell search apparatus. It is a block diagram which shows the structure of a channel fluctuation | variation estimation part.

  Embodiments for carrying out the invention will be described below.

(1) Configuration Example A configuration example of the disclosed cell search apparatus will be described with reference to the drawings. FIG. 1 is a diagram illustrating a wireless communication network including a mobile station 100 having a cell search device 1 which is a configuration example of the disclosed cell search device, and base stations 200a and 200b.

  As shown in FIG. 1, the cell search device 1 is provided in a mobile station 100 capable of wireless communication with a base station 200a or 200b. The mobile station 100 and the base stations 200a and 200b can wirelessly communicate with each other using a communication system such as 3GPP-LTE (Third Generation Partnership Project-Long Term Evolution). In the example shown in FIG. 1, each of the base stations 200a and 200b transmits a radio wave to a subordinate service area to form a cell, and the mobile station 100 is located within the cell of the base station 200a and the base station 200a. Communicating with. The base stations 200a and 200b are connected to the core network via a host device such as a gateway (not shown).

  Here, when performing a handover to the base station 200b having a communication band different from that of the base station 200a with which the mobile station 100 is communicating, a measurement gap section for the base station 200b (hereinafter referred to as a GAP section). A process in the case of performing a different frequency cell search using the will be described.

  In the GAP section, the cell search device 1 refers to the two types of synchronization signals PSS and SSS transmitted from the base station 200b and detects information such as a cell ID that identifies the base station 200b. For example, in a wireless communication system such as 3GPP-LTE, there are three types of candidates for the synchronization signal used as the PSS, but in the example shown below, one type of PSS candidate is used to simplify the description. The SSS has Nsss candidates corresponding to the cell ID of the base station. Further, it is assumed that the end positions of the symbols of SSS and PSS are separated by ΔT (m). Here, the number m is a number for distinguishing between a plurality of formats defined as frame formats.

  A specific configuration example and function of the cell search device 1 will be described with reference to FIG. FIG. 2 is a block diagram illustrating hardware included in the cell search device 1 and functional units that represent functions of the hardware for convenience.

  As shown in FIG. 2, the cell search device 1 includes RF 10, a frequency setting unit 20, a GAP control unit 30, a reception signal buffer 40, a PSS detection unit 50, a synchronization signal selection unit 60, and an SSS detection unit 70. Is provided. Each functional unit may realize a function by a unique hardware configuration, or may realize a function by processing of a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or the like. Good. For example, in the example shown in FIG. 2, the GAP control unit 30 and the synchronization signal selection unit 60 are shown as functions realized by the processing of the CPU. Note that the hardware corresponding to the CPU and other functional units may be provided independently by the cell search device 1 or may share the hardware included in the mobile station 100.

  The RF 10 is a high frequency circuit that receives a signal transmitted from the base station 200 a or 200 b based on the reception band set by the frequency setting unit 20. The RF 100 outputs the received reception signal to the reception signal buffer 40.

  The frequency setting unit 20 sets the reception band used by the RF 10 to receive the received signal according to the GAP section instructed by the GAP control unit 30, the reception band f1 in communication with the communicating base station 200a, and the base station 200b. Is appropriately switched between the reception band f2 in the communication with the network. For example, the frequency setting unit 20 changes the reception band from f1 to f2 at the start of the GAP section, and changes the reception band from f2 to f1 at the end of the GAP section. As will be described later, switching of the reception band takes a predetermined time, and during the switching, the reception band is in a transient state between f1 and f2. The manner of switching the reception band will be described later with reference to FIG.

  The GAP control unit 30 acquires GAP interval information from a signal transmitted by the base station 200 a received by the mobile station 100 and notifies the frequency setting unit 20 and the reception buffer 40 of the GAP interval information.

  The reception signal buffer 40 is a buffer memory that buffers the reception signal input from the RF 10 and outputs the received signal to the PSS detection unit 50 and the SSS detection unit 70 based on the GAP period notified from the GAP control unit 30. . For example, the reception signal buffer 40 may hold only the signal received in the GAP period according to the timing of the GAP period notified from the GAP control unit 30.

The PSS detection unit 50 detects the PSS reception timing T _PSS based on the time correlation between the time domain waveform of the PSS and the received signal. FIG. 3 is a block diagram illustrating a configuration of the PSS detection unit 50. In order to perform the above-described processing, the PSS detection unit 50 includes a time correlation calculation unit 51 and a peak detection unit 52.

  Unlike the example shown in FIG. 1, when the mobile station 100 receives received signals from a plurality of other cells during communication with the base station 200a, the received signal is mixed, so that the PSS detector 50 may detect the reception timing T1 for each cell and separately execute the subsequent cell search operation for each cell.

  The synchronization signal selection unit 60 selects the synchronization signals PSS and SSS used for detection of the cell ID based on the detected reception timing T1. In other words, the synchronization signal selection unit 60 determines the reception timing of the signal SSS used for the processing of the SSS detection unit 70 using the synchronization signal PSS. A more detailed operation of the synchronization signal selector 60 will be described later.

  The SSS detection unit 70 detects the cell ID of the base station 200b using the synchronization signals PSS and SSS selected by the synchronization signal selection unit 60. FIG. 4 is a block diagram illustrating a configuration of the SSS detection unit 70. In order to perform the above-described processing, the SSS detection unit 70 includes FFT units 71a and 71b, a channel estimation unit 72, an equivalent unit 73, a plurality of correlation calculation units 74, and a cell ID determination unit 75.

  The FFT units 71a and 72b perform FFT (Fast Fourier Transform) on the symbol positions of the synchronization signals PSS and SSS selected by the synchronization signal selection unit 60 to generate subcarrier signals. The FFT unit 71 a performs FFT on the received signal at the PSS timing, and outputs the generated subcarrier signal to the channel estimation unit 72.

The channel estimation unit 72 performs channel estimation on the PSS subcarrier k using the PSS subcarrier signal, thereby obtaining the channel estimation value h (k). The channel estimation value h (k) is calculated using the following equation using, for example, the received subcarrier signal r _PSS (k) for the PSS subcarrier k and the PSS subcarrier pattern replica P _PSS (k) that is a known pattern. Indicated by 1.

また、チャネル推定部７２は、ノイズの影響を除去するためにサブキャリアｋの周辺のサブキャリアで上記式（１）により特定されるチャネル推定値ｈ（ｋ）を重み付け平均化した上でチャネルの推定を行ってもよい。このような場合、チャネルの推定値ｈ（ｋ）は、重み係数をａ（ｌ）とすると、以下の数式２により示される。

Further, the channel estimation unit 72 performs weighted averaging of the channel estimation value h (k) specified by the above equation (1) with subcarriers around the subcarrier k in order to remove the influence of noise, and then performs channel averaging. An estimation may be performed. In such a case, the estimated value h (k) of the channel is expressed by Equation 2 below, where a (l) is a weighting factor.

ＦＦＴ部７１ｂは、ＳＳＳのシンボル位置において、受信信号に対してＦＦＴを行い、生成したサブキャリア信号を等価部７３に出力する。尚、１つのＰＳＳに対して複数のＳＳＳのシンボル位置候補が存在する場合、つまり、受信信号を規定するフレームフォーマットが複数通り（例えば、ｍ通り）あって、ＰＳＳとＳＳＳとの夫々のシンボル末尾の間隔ΔＴ（ｍ）がフレームフォーマットｍに応じて複数通り（ｍ通り）存在する場合には、ＦＦＴ部７１ｂは、夫々のＳＳＳのシンボル位置に対してＦＦＴを行う。

The FFT unit 71 b performs FFT on the received signal at the SSS symbol position, and outputs the generated subcarrier signal to the equivalent unit 73. When there are a plurality of SSS symbol position candidates for one PSS, that is, there are a plurality of frame formats (for example, m) that define the received signal, and the end of each symbol of PSS and SSS. When there are a plurality of (m) intervals ΔT (m) according to the frame format m, the FFT unit 71b performs FFT on each SSS symbol position.

The equivalent unit 73 generates the weight coefficient w (k) using the channel estimation value h (k) output from the channel estimation unit 72. The equivalent unit 73 performs an equivalent process by multiplying the received subcarrier signal r _SSS (k) for the SSS symbol by the generated weight coefficient w (k) to generate an equivalent subcarrier signal y (k). The multiplication of the weight coefficient w (k) is performed using the following Equation 3.

また、重み係数ｗ（ｋ）は、例えば、以下の数式４を参照して生成される。

Further, the weight coefficient w (k) is generated with reference to the following Expression 4, for example.

尚、重み係数ｗ（ｋ）は、以下の数式５に示されるように、受信サブキャリア信号ｒ_ＳＳＳ（ｋ）の位相だけを補正するように生成されてもよい。

Note that the weighting factor w (k) may be generated so as to correct only the phase of the received subcarrier signal r _SSS (k), as shown in Equation 5 below.

その他、重み係数ｗ（ｋ）は、雑音電力σ^２を用いて、以下の数式６に示されるようにＭＭＳＥ(minimum mean-square-error：最小二乗誤差)係数を用いるものであってもよく、その他の方法を用いて生成されるものであってよい。

In addition, the weight coefficient w (k) may be a noise mean σ ² and a MMSE (minimum mean-square-error) coefficient as shown in Equation 6 below. It may be generated using other methods.

相関演算部７４は、等価サブキャリア信号ｙ（ｋ）について、複数のＳＳＳパターン＃ｎ（ｎ＝０，１，２，・・・，Ｎｓｓｓ−１）に対する相関を演算する。具体的には、以下の数式７に示されるように相関値の電力Ｃ（ｎ）を算出する。

The correlation calculation unit 74 calculates the correlation for a plurality of SSS patterns #n (n = 0, 1, 2,..., Nsss−1) for the equivalent subcarrier signal y (k). Specifically, the power C (n) of the correlation value is calculated as shown in Equation 7 below.

セルＩＤ判定部７５は、算出された相関値の電力｜Ｃ（ｎ）｜が最大となるｎを検出し、該ｎに基づいてＳＳＳ番号（つまり、セルＩＤを示す情報）を検出する。尚、上述のように複数のフレームフォーマットｍに対応してΔＴ（ｍ）の値が複数通り存在し、各ΔＴ（ｍ）に対応して対してブラインドでｍを判定する場合、上記の相関演算を各ｍに対して個別に行う。相関演算部７４は、このような複数のフレームフォーマットｍに対応して個別の相関演算を行えるよう、複数設けられていてよい。相関演算の結果、セルＩＤ判定部７５は、相関値の電力｜Ｃ（ｍ，ｎ）｜が最大となるｍ及びｎに基づいて、所望のフレームフォーマットｍ（ｆｏｒｍａｔ ＃ｍ）と、ＳＳＳ番号（＃ｎ）とを検出する。

The cell ID determination unit 75 detects n that maximizes the calculated correlation value power | C (n) |, and detects the SSS number (that is, information indicating the cell ID) based on the n. As described above, when there are a plurality of values of ΔT (m) corresponding to a plurality of frame formats m, and m is determined blindly for each ΔT (m), the above correlation calculation is performed. For each m individually. A plurality of correlation calculators 74 may be provided so as to perform individual correlation calculations corresponding to such a plurality of frame formats m. As a result of the correlation calculation, the cell ID determination unit 75 determines the desired frame format m (format #m) and the SSS number (based on m and n where the power of correlation value | C (m, n) | #N) is detected.

(2) Example of synchronization signal selection processing FIG. 5 shows a state of a received signal from each base station when performing a different frequency cell search for the base station 200b using the GAP section of the signal transmitted from the base station 200a. Show.

  Moreover, regarding the received signal from the base station 200b, PSS and SSS included in the received signal are indicated. In FIG. 5, a transmission pattern of a synchronization signal in Frame structure type 2 of the 3GPP-LTE system is shown as an example of a received signal from base station 200b. In the transmission pattern of the synchronization signal in Frame structure type 2, one frame is 10 ms, and the synchronization signal including PSS and SSS is transmitted in a cycle of 5 ms. In the LTE system, a frame is divided into sections of 1 ms and called subframes. In each subframe, other data and a pilot signal called a common pilot are arranged and transmitted. Also, there is a 3 symbol separation between SSS and PSS.

  When an OFDM (Orthogonal Frequency-Division Multiplexing) system such as an LTE system is adopted, a guard interval corresponding to the delay time of the delayed wave is used for each symbol in order to avoid the influence of multipath fading. Or a cyclic prefix (CP) is added. On the other hand, since CP does not contribute to data demodulation, it can be considered that data transmission efficiency is reduced by adding CP. For this reason, the CP length is preferably determined in consideration of the delay time of the delayed wave, the transmission efficiency of the transmission signal, and the like.

  Thus, since a CP can take a plurality of CP lengths depending on the situation, a plurality of frame formats m are also defined according to each CP length. For this reason, even if the interval between the PSS and the SSS in the synchronization signal described above is 3 symbols, it is conceivable that the actual time interval changes according to the CP length.

  A dotted line in FIG. 5 shows a state in which the reception band of the mobile station 100 is switched. The reception band of the mobile station 100 is switched between the communication band f1 of the base station 200a and the base station 200b communication band f2 according to the GAP section. When the reception band is switched, specifically, in a predetermined period after the start of the GAP section and a predetermined period before the end, the reception band of the mobile station 100 is in a transient state that changes between f1 and f2. Search performance is degraded.

  FIG. 6 shows a plurality of examples of the relationship between the GAP period and the reception timing of the synchronization signal from the base station 200b that is subject to cell search. For example, as shown in FIG. 6A, when the reception timing of the synchronization signal PSS or SSS is included in a period related to such a transient state, a part or all of the symbols of the synchronization signal are included in a region where deterioration is large. . For this reason, when performing a cell search using these synchronizing signals, detection performance deteriorates. On the other hand, when the reception timing of the synchronization signal is not included in the period related to the transient state as shown in FIG. 6B, the cell search device 1 can execute an appropriate cell search using the synchronization signal.

The synchronization signal selection unit 60 selects the PSS and the SSS used for the cell ID determination based on the detected reception timing _{TPSS of the PSS} and the relative positional relationship between the GAP sections. To be precise, PSS and SSS are names indicating the signals themselves, and the synchronization signal selection unit 60 is not the synchronization signals PSS and SSS itself, but the time interval of the received signal used for detection of each signal, Alternatively, the head timing is selected. However, in the present embodiment, the phrase “select PSS or SSS” is used to select the timing or symbol position in the received signal used to detect PSS or SSS in relation to the operation of the synchronization signal selector 60. It is described as a purpose indicating the processing to be performed. Specifically, a process for selecting which period, in other words, PSS or SSS at the symbol position, to perform cell search for the synchronization signal transmitted at a predetermined period is shown.

(2-1) Synchronization signal selection method when the interval between PSS and SSS is determined as a whole Referring to FIG. 7, PSS reception timing T _PSS and relative of GAP interval by synchronization signal selection unit 60 In the selection method of PSS and SSS used for the determination of the cell ID based on the positional relationship, the operation when the interval ΔT between the PSS and SSS is determined will be described.

  FIG. 7 is a diagram illustrating the reception timing of the synchronization signal from the base station 200b in the GAP section of the base station 200a. In FIG. 7, the top timing of the GAP section is T0, the end timing is T ', and the PSS detection timing transmitted from the base station 200a is T1. In the example shown in FIG. 7, since the synchronization signal is transmitted based on a predetermined frame format m, the interval between PSS and SSS is determined to be unique ΔT (m).

The synchronization signal selection unit 60 determines the head position T _SSS (m) of the SSS symbol in the frame format m by determining the head position T _PSS of the PSS symbol used for SSS detection. Specifically, T _SSS (m) = T _PSS −ΔT (m). Further, it is conceivable that the head position T _PSS of the PSS symbol becomes T _PSS = T1 when the PSS reception timing in the cell search device 1 is T1.

However, as described above, the cell search performance may be deteriorated due to the transition state of the reception band switching between the head part and the tail part of the GAP section. Therefore, the synchronization signal selection unit 60 selects T _PSS and T _SSS as shown below according to the PSS reception timing T1.

  First, as shown in FIG. 7A, the synchronization signal selection unit 60 divides the GAP section T′-T0 by setting predetermined threshold values A1, A2, A3, and A4. Here, each time is T0 <A1 <A2 <A3 <A4 <T ′. In the GAP section, the section from T0 to A1 and the section from A4 to T ′ are greatly deteriorated in cell search performance due to the influence of the transient state described above, and an appropriate cell search using the synchronization signal detected in the corresponding section can be performed. There is no possibility. The synchronization signal selection unit 60 compares the PSS reception timing T1 with the timings A1, A2, A3, and A4, and selects the detection timings of signals used as PSS and SSS.

As shown in FIG. 7B, when the PSS reception timing T1 is a section from T0 to A1 (T1-T0 <A1), the synchronization signal selection unit 60 is a candidate for the leading position T _PSS of the PSS symbol. PSS symbol position candidates (specifically, coincident with the PSS detection timing T1 as described above) and SSS symbol position candidates (specifically, the above-described SSS symbol head position T _SSS (m)). Thus, it is determined that there is a possibility that deterioration due to a transient state may occur because both of them are close to the head portion of the GAP section. At this time, the synchronization signal selection unit 60 sets T _PSS = T1 + 5 ms and T _SSS (m) = T1−ΔT (m) +5 ms so that signals outside the interval from T0 to A1 are used. Here, 5 ms is the transmission period of the synchronization signal in Frame structure type 2 as described above. That is, when the PSS is detected in the section from T0 to A1, the synchronization signal selection unit 60 determines that both the SSS and the SSS arranged at a time earlier by ΔT than the PSS are included in the region where the deterioration is large. By using PSS and SSS transmitted in a cycle, a synchronization signal with little deterioration is selected.

As shown in FIG. 7C, when the PSS is detected in the section from A1 to A2 (A1 ≦ T1-T0 <A2), the synchronization signal selection unit 60 makes a transient transition at the symbol position of T1 for PSS. It is determined that deterioration due to the state does not occur, and T _PSS = T1 is set. On the other hand, in the synchronization signal selection unit 60, the SSS arranged at the time before the arrangement position of the PSS is close to the head part of the GAP section and may be arranged in a region where deterioration occurs due to a transient state. From this, it is determined that the arrangement after 5 ms has less deterioration, and T _SSS (m) = T1−ΔT (m) +5 ms is set.

As shown in FIG. 7D, when the PSS is detected in the section from A2 to A3 (A2 ≦ T1-T0 <A3), the synchronization signal selection unit 60 makes a transient transition at the symbol position of T1 for PSS. It is determined that deterioration due to the state does not occur, and T _PSS = T1 is set. Also, regarding SSS, it is determined that deterioration due to a transient state does not occur, and T _SSS (m) = T1−ΔT (m) is set.

As shown in FIG. 7E, when the PSS is detected in the section from A3 to A4 (A3 ≦ T1-T0 <A4), the synchronization signal selection unit 60 performs GAP at the symbol position of T1 for PSS. It is determined that there is a possibility of deterioration due to a transient state near the end of the section, and the PSS reception timing is set to a position one cycle before, that is, T _PSS = T1-5 ms. On the other hand, the SSS arranged at the time before the arrangement position of the PSS is determined not to be affected by deterioration due to the transient state, and is set to T _SSS (m) = T1−ΔT (m).

As shown in FIG. 7F, when the PSS is detected in the section from A4 to T ′ (A4 ≦ T1-T0 <T ′), the synchronization signal selection unit 60 determines the symbol position of T1 for PSS. Then, it is close to the end of the GAP section, and it is determined that there is a possibility of deterioration due to the transient state, and the PSS reception timing is set to T _PSS = T1-5 ms. Further, regarding SSS arranged at a time ΔT before the arrangement position of the PSS, it is determined that the influence of deterioration due to the transient state may occur, and T _SSS (m) = T1−ΔT (m) −5 ms is set. .

  The threshold values A1, A2, A3, and A4 are set in consideration of the time required for switching the reception band in the mobile station 100. In particular, when it is necessary to consider individual differences of RF components, it is preferable to set a value optimized individually for each apparatus. For example, each threshold of A1, A2, A3, and A4 distinguishes between a section in which cell search performance may be degraded due to a transient state of reception band switching and a section other than that in the GAP section. An appropriate value may be set so that FIG. 7 shows an example in which the GAP section is divided into five using four threshold values A1, A2, A3, and A4. However, the GAP interval may be divided into an arbitrary number using an arbitrary number of thresholds. However, from the viewpoint of distinguishing between a section in which cell search performance degradation may occur due to a transient state of reception band switching and a section other than that in the GAP section, at least two threshold values are used. It is preferable to divide the section into at least three.

(2-2) Synchronization signal selection method in the case where a plurality of intervals between PSS and SSS are set A plurality of intervals corresponding to a plurality of frame formats (for example, m) with respect to the interval ΔT between PSS and SSS When ΔT (for example, m) is set, the synchronization signal selection unit 60 selects the detection timing of PSS and SSS in consideration of ΔT (m).

  FIG. 8 is a diagram illustrating a state in which the synchronization signal is selected based on the relationship between the PSS reception timing T1 and the threshold when a plurality of intervals ΔT (m) between the PSS and the SSS are set.

As shown in FIG. 8 (a), the synchronization signal selection unit 60 is a threshold value for distinguishing between the head portion and the tail portion of the GAP section from T0 to T ′ and the region where deterioration due to the transient state is determined to occur. A1 _PSS and A2 _PSS are set. That is, the section from T0 to A1 _{PSS and} the section from A2 _PSS to T ′ are areas in which the synchronization signal selection unit 60 determines that deterioration due to a transient state occurs.

As shown in FIG. 8A, when the PSS is detected in the section from T0 to A1 _PSS (T1-T0 <A1 _PSS ), the synchronization signal selection unit 60 has the symbol position of T1 as the head part of the GAP section. It is determined that there is a possibility of deterioration due to a transient state, and T _PSS = T1 + 5 ms is set.

As shown in FIG. 8B, when the PSS is detected in the interval from A1 _PSS to A2 _PSS (A1 _PSS ≦ T1-T0 <A2 _PSS ), deterioration due to the transient state occurs at the symbol position of T1. _Therefore , T _PSS = T1 is determined.

As shown in FIG. 8C, when the PSS is detected in the interval from A2 _PSS to T ′ (A2 _PSS ≦ T1-T0 <T ′), the symbol position of T1 is close to the end portion of the GAP interval, It is determined that there is a possibility of deterioration due to a transient state, and T _PSS = T1-5 ms is set.

Further, as shown in FIG. 8D, the synchronization signal selection unit 60 selects thresholds A1 _SSS (m) and A2 _SSS for selecting the _SSS timing T _SSS (m) according to the PSS reception timing T1. (M) is set for each frame format m.

Here, the thresholds A1 _SSS (m) and A2 _SSS (m) are thresholds related to T1, respectively, and the SSS reception timing T1-ΔT (m) specified from the PSS reception timing T1 depends on the transient state. This is a threshold value for distinguishing areas where degradation is determined to occur. That is, when T1 is received in the section from T0 to A1 _SSS (m) and the section from A2 _SSS (m) to T ′ for the synchronization signal of frame format m, the reception timing T1-ΔT (m ) Is included in a region where deterioration due to a transient state occurs. Since the timing on the received signal that is a candidate for SSS is earlier than the reception timing of _PSS , A1 _PSS <A1 _SSS and A2 _PSS <A2 _SSS (m).

As shown in FIG. 8D, when the PSS is detected in a section from T0 to A1 _SSS (T1-T0 <A1 _SSS (m)), the synchronization signal selection unit 60 is a candidate for SSS T1- Since it is determined that the symbol position of ΔT (m) is close to the head portion of the GAP section and there is a possibility of deterioration due to a transient state, T _SSS (m) = T1−ΔT (m) +5 ms.

As shown in FIG. 8E, when PSS is detected in a section from A1 _SSS (m) to A2 _SSS (m) (A1 _SSS (m) ≦ T1-T0 <A2 _SSS (m)), T1 It is determined that deterioration due to the transient state does not occur at the symbol position of −ΔT (m), and T _SSS (m) = T1−ΔT (m).

As shown in FIG. 8F, when the PSS is detected in the interval from A2 _SSS to T ′ (A2 _SSS (m) ≦ T1-T0 <T ′), the symbol position of T1-ΔT (m) is It is determined that there is a possibility of deterioration due to a transient state near the end of the GAP section, and T _SSS (m) = T1−ΔT (m) −5 ms is set.

The synchronization signal selection unit 60 sets the thresholds A1 _SSS (m) and A2 _SSS (m) for each frame format m, and selects the threshold to be applied according to the frame format m of the actual received signal.

In the above-described T _SSS selection method, the synchronization signal selection unit 60 sets thresholds A1 _SSS (m) and A2 _SSS (m) for each frame format m, and compares each with T1 that is a PSS symbol position candidate. doing. On the other hand, the synchronization signal selection unit 60 may set an SSS symbol position candidate instead of a PSS symbol position candidate, and select an SSS symbol position from comparison with a threshold value.

For example, the synchronization signal selection unit 60 sets a temporary SSS symbol position T _tmp (m) for each frame format m. Also, common threshold values A1 _SSS and A2 _SSS that do not depend on the frame format m are set, and the symbol position T _SSS of the _SSS is selected by comparing this T _tmp (m) with each threshold value. In this aspect, it is not necessary to individually set the threshold value for each frame format, and T _SSS can be selected more easily.

Specifically, the synchronization signal selection unit 60 sets T _tmp (m) = T1−ΔT (m) as a temporary SSS symbol position for each frame format m. ΔT (m) indicates the time length between the PSS and the SSS in consideration of the CP length corresponding to the frame format m. The synchronization signal selection unit 60 may hold various data in advance in a memory or the like so that an appropriate ΔT (m) can be selected corresponding to a plurality of frame formats m.

As illustrated in FIG. 9A, the synchronization signal selection unit 60 detects T _tmp (m), which is an SSS symbol position candidate, in a section from T0 to A1 _SSS (T1−T0 <T _tmp ( m)), the symbol position of T _tmp (m) is close to the head part of the GAP section, and it is determined that there is a possibility of deterioration due to the transient state, and T _SSS = T _tmp (m) +5 ms.

As shown in FIG. 9B, when T _tmp (m), which is an SSS symbol position candidate, is detected in the section from A1 _SSS to A2 _SSS (A1 _SSS ≦ T1-T0 <A2 _SSS ), T _tmp It is determined that the deterioration due to the transient state does not occur at the symbol position of (m), and T _SSS = T _tmp (m).

As shown in FIG. 9C, when T _tmp (m), which is a symbol position candidate of SSS, is detected in a section from A2 _SSS to T ′ (A2 _SSS ≦ T1-T0 <T ′), T _tmp It is determined that the symbol position of (m) is close to the end portion of the GAP section and there is a possibility of deterioration due to the transient state, and T _SSS = T _tmp (m) −5 ms.

When considering fading or the like whose influence on the cell search performance changes with time, it is conceivable that the cell search performance changes due to a change in the value of ΔT (m) corresponding to the frame format m. In such a case, by using individual threshold values A1 _SSS (m) and A2 _SSS (m) for each frame format m when selecting a symbol to be used for SSS detection processing, The cell search performance can be suitably adjusted. On the other hand, in the actual frame format, the difference between the values of ΔT (m) corresponding to each other is not so large. Therefore, even when the common threshold values A1 _SSS and A2 _SSS are used, it can be said that there is no significant decrease in performance. .

(2-3) Synchronization signal selection method when the synchronization signal detection timing is limited in advance In the above example, the PSS detection unit 50 detects the PSS at an arbitrary timing within the GAP interval, and performs cell detection according to the detection timing T1. The example in which the PSS and SSS used for the search are selected has been described. However, for example, since the _PSS detected in the section from T0 to A1 _{PSS and} the section from A2 _PSS to T ′ is determined to be affected by the transient state, the symbols in such a section are subjected to cell search. Not selected for use.

Therefore, for suitable selection of the synchronization signal, T1 may be detected after limiting the PSS detection timing in advance. Specifically, as shown in FIG. 10, in the cell search device 1 of this aspect, the received signal interval held by the received signal buffer 40 or the peak detection interval of the peak detecting unit 52 of the PSS detecting unit 50 is A1 in advance. It is limited to the section from _PSS to A2 _PSS . Therefore, the PSS detection timing T1 always satisfies A1 _PSS ≦ T1 <A2 _PSS .

As described above, since it is determined that there is no influence of the transient state on the symbol position of T1 in this section, the synchronization signal selection unit 60 sets T _PSS = T1.

On the other hand, the synchronization signal selection unit 60 selects T _SSS from the comparison between T _tmp (m) and A1 _SSS and A2 _SSS as described above. Depending on the detection position of T1, even if A1 _PSS ≦ T1 <A2 _PSS is established, T _tmp (m) = T1−ΔT (m), which is a candidate SSS symbol position, is arranged at a position affected by the transient state. Because there is a possibility that.

(3) Modified Example With reference to the drawings, a cell search device 1 ′ that is a modified example of the disclosed cell search device will be described.

In the configuration example described above, the symbol position used for the cell search is selected based on the relationship between the PSS detection timing T1 and the GAP interval head timing T0. For this reason, for example, while T _PSS = T1, T1-ΔT-5ms or T1-ΔT + 5ms may be selected for T _SSS instead of the T1-ΔT symbol position closest to T1. At this time, channel equivalence is performed using SSS at a timing farther from the detection timing of the PSS than T1-ΔT closest to T1 used conventionally. In such a case, it is conceivable that the influence of fading appears more remarkably due to the spread of the timing difference, and the cell search performance deteriorates. Therefore, by selecting the symbol position used for cell search in consideration of the trade-off between performance degradation due to the transient state of reception band switching, such as the head part and tail part of the GAP section, and performance degradation due to such fading. The cell search performance can be realized with higher accuracy.

  In the modified example of the disclosed cell search apparatus, the size of temporal channel fluctuation is estimated using a conventionally known technique and the like, and the above-described PSS and SSS selection modes are taken into account. By adjusting, a symbol position capable of realizing a more accurate cell search is selected.

  FIG. 11 is a block diagram illustrating hardware included in the cell search device 1 ′ and functional units that represent functions of the hardware for convenience. As shown in FIG. 11, the cell search device 1 ′ includes a channel fluctuation estimation unit 80 in addition to the configuration of the cell search device 1. For example, the channel fluctuation estimation unit 80 receives an input of a common pilot of a cell that has already been detected in a period other than the GAP period, and performs channel estimation on the common pilot. At this time, the channel fluctuation estimation unit 80 performs channel estimation for each subframe, and calculates a temporal correlation of channel fluctuations from the calculated channel estimation value. A predetermined threshold value is set for the calculated temporal correlation, and the channel fluctuation magnitude determined in a plurality of stages is output to the synchronization signal selection unit 60 as the channel fluctuation estimation result. The synchronization signal selection unit 60 selects thresholds A1, A2, and the like related to the above-described selection of PSS and SSS based on the estimation result of channel fluctuation.

  FIG. 12 is a block diagram showing the configuration of the channel fluctuation estimation unit 80. In order to perform the above-described processing, the channel fluctuation estimation unit 80 includes an FFT unit 81, a pilot extraction unit 82, a channel estimation unit 83, and a fluctuation estimation unit 84.

  The FFT unit 81 performs FFT on the input received signal and outputs the generated subcarrier signal to the pilot extraction unit 82.

  Pilot extraction section 82 extracts a subcarrier component of a pilot arranged in the first symbol of each subframe of a cell that has already been detected from the received signal.

Channel estimation section 83 cancels the pilot pattern arranged in the first symbol of subframe #n of base station 200b subject to cell search, and calculates a channel estimation value. Channel estimation value h (n, k) for common pilot subcarrier k in subframe #n is, for example, common pilot reception subcarrier signal r _Pilot (n, k) and common pilot subcarriers that are known patterns. Using the pattern replica P _Pilot (k), it is calculated as shown in Equation 8 below.

チャネル推定値ｈ（ｎ，ｋ）について、ｋの周辺のパイロットサブキャリアで平均化してもよい。チャネル推定部８３は、このように算出された周波数軸上でｋ番目のパイロットについてのチャネル推定値ｈ（ｎ，ｋ）を複数のｋについて算出し、サブフレーム間の時間相関値を算出する。時間相関値Ｃ_ｔは、以下の数式９に示されるように算出される。

The channel estimation value h (n, k) may be averaged with pilot subcarriers around k. The channel estimation unit 83 calculates a channel estimation value h (n, k) for the kth pilot on the frequency axis calculated in this way for a plurality of k, and calculates a time correlation value between subframes. The time correlation value C _t is calculated as shown in Equation 9 below.

変動推定部８４は、このように算出される時間相関値Ｃ_ｔを、予め設定した閾値と比較することで、チャネル変動の大きさの判別を行う。例えば、変動推定部８４は、閾値Ｂ（ｘ）について、ｘ＝０乃至Ｎｍａｘのように複数通り設定する。ここで、Ｂ（０）＝０≦Ｂ（１）≦Ｂ（２）≦・・・≦Ｂ（Ｎｍａｘ）とする。変動推定部８４は、時間相関値Ｃ_ｔと閾値とを比較し、例えば、Ｂ（Ｎｍａｘ）≦Ｃ_ｔの場合は、Δｈ＝Ｎｍａｘとし、Ｃ_ｔ＜Ｂ（Ｎｍａｘ）の場合、Ｂ（ｎ）≦Ｃ_ｔ＜Ｂ（ｎ＋１）に対して、Δｈ＝ｎとするように同期信号選択部６０において用いる閾値の決定に係る要素Δｈを設定する。

Variation estimation unit 84, the thus calculated is the time correlation value C _t, is compared with a preset threshold value, it performs a determination of the magnitude of channel fluctuation. For example, the fluctuation estimation unit 84 sets a plurality of threshold values B (x) such as x = 0 to Nmax. Here, B (0) = 0.ltoreq.B (1) .ltoreq.B (2) .ltoreq..ltoreq.B (Nmax). The fluctuation estimation unit 84 compares the time correlation value C _t with a threshold value. For example, if B (Nmax) ≦ C _t , Δh = Nmax, and if C _t <B (Nmax), B (n) For ≦ C _t <B (n + 1), an element Δh related to determination of a threshold value used in the synchronization signal selection unit 60 is set so that Δh = n.

The synchronization signal selection unit 60 adjusts the threshold for detecting the SSS symbol position in accordance with the channel fluctuation magnitude estimated in this way. For example, the thresholds A1 _SSS (m) and A2 _SSS (m) are set as A1 _SSS (Δh, m) and A2 _SSS (Δh, m), respectively, and the coefficient is changed for each channel fluctuation magnitude Δh.

  The channel fluctuation estimation unit 80 estimates the magnitude of the channel fluctuation in the time direction. As described above, the method for estimating the magnitude of the channel fluctuation can be diverted from various conventional techniques and is not the gist of the present invention, and thus detailed description thereof is omitted.

  As described above, the synchronization signal selection unit 60 of the cell search device 1 ′ according to the modified example performs deterioration in cell search performance when the channel variation with respect to time is large, and transients at the beginning and end portions of the GAP section. The synchronization signal selection operation is changed in consideration of a trade-off with deterioration of cell search performance depending on the state. For this reason, it is possible to select a synchronization signal that can realize a highly accurate cell search according to the situation.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the scope or spirit of the invention that can be read from the claims and the entire specification. The method and the mobile station are also included in the technical scope of the present invention.

As mentioned above, the following additional remarks are further described about embodiment described in this specification.
(Appendix 1)
A cell search apparatus that communicates with one cell at a predetermined frequency, switches a reception frequency to a frequency different from the predetermined frequency in a specific time interval, and performs a cell search for another cell different from the one cell. And
A reception unit that receives a reception signal including a first synchronization signal that is a candidate for a specific signal used for specifying the other cell in the specific time interval;
A first detector for detecting a reception timing of the first synchronization signal;
A synchronization signal selection unit that determines a reception timing of a specific signal used for specifying the other cell included in the reception signal based on a reception timing of the first synchronization signal within the specific time interval;
A cell search device comprising: a second detection unit configured to specify the other cell using a specific signal used for specifying the other cell acquired based on the determined reception timing.
(Appendix 2)
The receiving unit receives the signal further including a second synchronization signal that is a candidate for a specific signal used for specifying the other cell,
The synchronization signal selection unit, based on the detected reception timing of the first synchronization signal and the relative relationship between the specific time interval, the reception timing of the specific signal used for specifying the other cell, Among the received signals received in a specific time interval, (i) the corrected timing obtained by correcting the detected reception timing of the first synchronization signal and the detected reception timing of the first synchronization signal (Ii) paired with the detected timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal and the detected first synchronization signal. The cell search device according to claim 1, wherein the cell search device is determined as a combination with any one of the corrected timings obtained by correcting the reception timing of the transmitted second synchronization signal. Place.
(Appendix 3)
The synchronization signal selection unit may be configured such that the detected reception timing of the first synchronization signal is included in a transition period from the start to the completion of the frequency switching in the specific time interval. A reception timing of a specific signal used for specifying the other cells; (i) a corrected timing obtained by correcting the reception timing of the detected first synchronization signal; and (ii) the detected timing The reception timing of the second synchronization signal transmitted in pairs with the first synchronization signal and the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal are corrected. Determined to be a combination with one of the corrected timing obtained by
The synchronization signal selection unit, when the detected reception timing of the first synchronization signal is not included in the transient period, (i) detects the reception timing of the specific signal used for specifying the other cell. The reception timing of the first synchronization signal, and (ii) the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal and the detected first synchronization. The supplementary note 2 is characterized in that it is determined to be a combination with any one of the corrected timings obtained by correcting the reception timing of the second synchronization signal transmitted in pairs with the signal. Cell search device.
(Appendix 4)
The synchronization signal selection unit starts switching the frequency in the specific time interval when the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal is received. Included in the transition period from completion to completion, the reception timing of the specific signal used to specify the other cell is (i) the reception timing of the detected first synchronization signal and the detected detection timing Either of the corrected timing obtained by correcting the reception timing of the first synchronization signal, and (ii) the second synchronization signal transmitted in pairs with the detected first synchronization signal. Decide to be a combination with the corrected timing obtained by correcting the reception timing,
When the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal is not included in the transient period, the synchronization signal selection unit identifies the other cell. The reception timing of the specific signal used in (1) is either one of the corrected timing obtained by correcting (i) the detected reception timing of the first synchronization signal and the detected reception timing of the first synchronization signal And (ii) the reception timing of the second synchronization signal transmitted in pairs with the first synchronization signal detected by the first detection unit, and the first detection unit detected by the first detection unit. Note that it is determined so as to be a combination with any one of the corrected timings obtained by correcting the reception timing of the second synchronization signal transmitted in pairs with one synchronization signal. The cell search device according to 2 or 3.
(Appendix 5)
The corrected timing obtained by correcting the detected reception timing of the first synchronization signal corresponds to the detected reception timing of the first synchronization signal in accordance with the transmission cycle of the first synchronization signal. It is the timing obtained by advancing or delaying by a period,
The corrected timing obtained by correcting the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal is paired with the detected first synchronization signal. Supplementary notes 2 to 4 characterized in that the timing is obtained by advancing or delaying the reception timing of the second synchronization signal to be transmitted by a period corresponding to the transmission cycle of the second synchronization signal. The cell search device according to any one of the above.
(Appendix 6)
The receiving unit receives the signal further including a second synchronization signal that is a candidate for a specific signal used for specifying the other cell,
The synchronization signal selection unit, based on the detected reception timing of the first synchronization signal and the relative relationship between the specific time interval, the reception timing of the specific signal used for specifying the other cell, Among reception signals received in a specific time interval, a reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal and a pair with the detected first synchronization signal The cell search device according to supplementary note 1, wherein the cell search device is determined as one of the corrected timings obtained by correcting the reception timing of the second synchronization signal transmitted in the above manner.
(Appendix 7)
The synchronization signal selection unit starts switching the frequency in the specific time interval when the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal is received. The second signal transmitted in pairs with the detected first synchronization signal, the reception timing of the specific signal used to identify the other cell is included Determined to be the corrected timing obtained by correcting the synchronization signal reception timing,
When the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal is not included in the transient period, the synchronization signal selection unit identifies the other cell. Wherein the reception timing of the specific signal used for the second synchronization signal is determined to be the reception timing of the second synchronization signal transmitted in a pair with the first synchronization signal detected by the first detection unit. The cell search device according to appendix 6.
(Appendix 8)
The corrected timing obtained by correcting the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal is paired with the detected first synchronization signal. Supplementary note 6 or 7, wherein the timing is a timing obtained by advancing or delaying the reception timing of the second synchronization signal transmitted in a period corresponding to the transmission cycle of the second synchronization signal. The cell search device described in 1.
(Appendix 9)
The synchronization signal selection unit, based on the detected reception timing of the first synchronization signal and the relative relationship between the specific time interval, the reception timing of the specific signal used for specifying the other cell, Of the reception signals received in a specific time interval, the reception timing of the first synchronization signal detected by the first detection unit and the reception timing of the first synchronization signal detected by the first detection unit The cell search device according to appendix 1 or 2, wherein the cell search device is determined as one of the post-correction timings obtained by the correction.
(Appendix 10)
The synchronization signal selection unit may be configured such that the detected reception timing of the first synchronization signal is included in a transition period from the start to the completion of the frequency switching in the specific time interval. , Determining the reception timing of the specific signal used for specifying the other cells to be a corrected timing obtained by correcting the reception timing of the detected first synchronization signal,
When the detected reception timing of the first synchronization signal is not included in the transient period, the synchronization signal selection unit detects the reception timing of the specific signal used for specifying the other cell. 10. The cell search device according to appendix 9, wherein the cell search device is determined so as to be the reception timing of one synchronization signal.
(Appendix 11)
The corrected timing obtained by correcting the detected reception timing of the first synchronization signal corresponds to the detected reception timing of the first synchronization signal in accordance with the transmission cycle of the first synchronization signal. The cell search device according to appendix 9 or 10, wherein the timing is obtained by advancing or delaying by a period.
(Appendix 12)
The synchronization signal selection unit sets a plurality of threshold values for dividing the specific time section into a plurality of sections, and compares the plurality of threshold values with the detected reception timing of the first synchronization signal. 12. The cell search device according to any one of appendices 1 to 11, wherein a reception timing of a specific signal used for specifying the other cell included in the received signal is determined.
(Appendix 13)
The synchronization signal selection unit can distinguish between a transition period from the start of switching of the frequency in the specific time section to the completion thereof and a period other than the transition period. The cell search device according to appendix 12, wherein the plurality of threshold values for dividing the specific time section into the plurality of sections are set.
(Appendix 14)
The receiving unit receives the received signal transmitted in a plurality of different frame formats;
14. The cell search device according to appendix 12 or 13, wherein the synchronization signal selection unit sets the plurality of thresholds according to the frame format.
(Appendix 15)
A channel fluctuation estimation unit for estimating a time-series channel fluctuation of the signal;
The cell search device according to any one of appendices 12 to 14, wherein the synchronization signal selection unit sets the plurality of thresholds according to the estimated channel fluctuation.
(Appendix 16)
A cell search method that communicates with one cell at a predetermined frequency and performs a cell search for another cell different from the one cell by switching the reception frequency to a frequency different from the predetermined frequency in a specific time interval. And
A reception step of receiving a reception signal including a first synchronization signal that is a candidate for a specific signal used for specifying the other cells in the specific time interval;
A first detection step of detecting a reception timing of the first synchronization signal;
A synchronization signal selection step of determining a reception timing of a specific signal used for specifying the other cell included in the reception signal based on a reception timing of the first synchronization signal in the specific time interval;
A cell search method comprising: a second detection step of specifying the other cell using a specific signal used for specifying the other cell acquired based on the determined reception timing.
(Appendix 17)
A cell search device that communicates with one cell at a predetermined frequency and performs a cell search for another cell different from the one cell by switching a reception frequency to a frequency different from the predetermined frequency in a specific time interval. A mobile station,
The cell search device includes:
A reception unit that receives a reception signal including a first synchronization signal that is a candidate for a specific signal used for specifying the other cell in the specific time interval;
A first detector for detecting a reception timing of the first synchronization signal;
A synchronization signal selection unit that determines a reception timing of a specific signal used for specifying the other cell included in the reception signal based on a reception timing of the first synchronization signal within the specific time interval;
A mobile station, comprising: a second detection unit configured to identify the other cell using a specific signal used to identify the other cell acquired based on the determined reception timing.

1 Cell search device 10 RF,
20 frequency setting section,
30 GAP controller,
40 Receive signal buffer,
50 PSS detector,
60 Sync signal selector,
70 SSS detector,
80 channel fluctuation estimation unit,
100 Mobile station 200a, 200b Base station.

Claims (10)

A cell search apparatus that communicates with one cell at a predetermined frequency, switches a reception frequency to a frequency different from the predetermined frequency in a specific time interval, and performs a cell search for another cell different from the one cell. And
A reception unit that receives a reception signal including a first synchronization signal that is a candidate for a specific signal used for specifying the other cell in the specific time interval;
A first detector for detecting a reception timing of the first synchronization signal;
A synchronization signal selection unit that determines a reception timing of a specific signal used for specifying the other cell included in the reception signal based on a reception timing of the first synchronization signal within the specific time interval;
A second detection unit that specifies the other cell using a specific signal used to specify the other cell acquired based on the determined reception timing ;
The synchronization signal selection unit sets a plurality of threshold values for dividing the specific time section into a plurality of sections, and compares the plurality of threshold values with the detected reception timing of the first synchronization signal. , cell search apparatus characterized that you determine the reception timing of a specific signal to be used for certain of the other cells included in the received signal. The receiving unit receives the signal further including a second synchronization signal that is a candidate for a specific signal used for specifying the other cell,
The synchronization signal selection unit, based on the detected reception timing of the first synchronization signal and the relative relationship between the specific time interval, the reception timing of the specific signal used for specifying the other cell, Among the received signals received in a specific time interval, (i) the corrected timing obtained by correcting the detected reception timing of the first synchronization signal and the detected reception timing of the first synchronization signal (Ii) paired with the detected timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal and the detected first synchronization signal. 2. The cell search according to claim 1, wherein the cell search is determined as a combination with any one of the corrected timings obtained by correcting the reception timing of the transmitted second synchronization signal. apparatus. The synchronization signal selection unit may be configured such that the detected reception timing of the first synchronization signal is included in a transition period from the start to the completion of the frequency switching in the specific time interval. A reception timing of a specific signal used for specifying the other cells; (i) a corrected timing obtained by correcting the reception timing of the detected first synchronization signal; and (ii) the detected timing The reception timing of the second synchronization signal transmitted in pairs with the first synchronization signal and the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal are corrected. Determined to be a combination with one of the corrected timing obtained by
The synchronization signal selection unit, when the detected reception timing of the first synchronization signal is not included in the transient period, (i) detects the reception timing of the specific signal used for specifying the other cell. The reception timing of the first synchronization signal, and (ii) the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal and the detected first synchronization. 3. The method according to claim 2, wherein the timing is determined so as to be a combination with one of the corrected timings obtained by correcting the reception timing of the second synchronization signal transmitted in pairs with the signal. Cell search device. The synchronization signal selection unit starts switching the frequency in the specific time interval when the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal is received. Included in the transition period from completion to completion, the reception timing of the specific signal used to specify the other cell is (i) the reception timing of the detected first synchronization signal and the detected detection timing Either of the corrected timing obtained by correcting the reception timing of the first synchronization signal, and (ii) the second synchronization signal transmitted in pairs with the detected first synchronization signal. Decide to be a combination with the corrected timing obtained by correcting the reception timing,
When the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal is not included in the transient period, the synchronization signal selection unit identifies the other cell. The reception timing of the specific signal used in (1) is either one of the corrected timing obtained by correcting (i) the detected reception timing of the first synchronization signal and the detected reception timing of the first synchronization signal And (ii) the reception timing of the second synchronization signal transmitted in pairs with the first synchronization signal detected by the first detection unit, and the first detection unit detected by the first detection unit. And determining a combination with any one of the corrected timings obtained by correcting the reception timing of the second synchronization signal transmitted in a pair with the one synchronization signal. Item 4. The cell search device according to Item 2 or 3. The corrected timing obtained by correcting the detected reception timing of the first synchronization signal corresponds to the detected reception timing of the first synchronization signal in accordance with the transmission cycle of the first synchronization signal. It is the timing obtained by advancing or delaying by a period,
The corrected timing obtained by correcting the reception timing of the second synchronization signal transmitted in pairs with the detected first synchronization signal is paired with the detected first synchronization signal. 3. The timing obtained by advancing or delaying the reception timing of the second synchronization signal transmitted in a manner corresponding to the transmission period of the second synchronization signal. 5. The cell search device according to any one of 4. The synchronization signal selection unit can distinguish between a transition period from the start of switching of the frequency in the specific time section to the completion thereof and a period other than the transition period. The cell search device according to claim 1 , wherein the plurality of threshold values for dividing the specific time section into the plurality of sections are set. The receiving unit receives the received signal transmitted in a plurality of different frame formats;
The synchronization signal selecting unit, in accordance with the frame format, the cell search apparatus according to claim 1 or 6, characterized in that to set a plurality of threshold values. A channel fluctuation estimation unit for estimating a time-series channel fluctuation of the signal;
The synchronization signal selector in response to the channel fluctuation estimated, the cell search apparatus according to claim 1, 6 or 7, characterized in that to set a plurality of threshold values. A cell search method that communicates with one cell at a predetermined frequency and performs a cell search for another cell different from the one cell by switching the reception frequency to a frequency different from the predetermined frequency in a specific time interval. And
A reception step of receiving a reception signal including a first synchronization signal that is a candidate for a specific signal used for specifying the other cells in the specific time interval;
A first detection step of detecting a reception timing of the first synchronization signal;
A synchronization signal selection step of determining a reception timing of a specific signal used for specifying the other cell included in the reception signal based on a reception timing of the first synchronization signal in the specific time interval;
A second detection step of specifying the other cell using a specific signal used for specifying the other cell acquired based on the determined reception timing ,
The synchronization signal selection step sets a plurality of threshold values for dividing the specific time interval into a plurality of intervals, and compares the plurality of threshold values with the detected reception timing of the first synchronization signal. , cell search method characterized that you determine the reception timing of a specific signal to be used for certain of the other cells included in the received signal. A cell search device that communicates with one cell at a predetermined frequency and performs a cell search for another cell different from the one cell by switching a reception frequency to a frequency different from the predetermined frequency in a specific time interval. A mobile station,
The cell search device includes:
A reception unit that receives a reception signal including a first synchronization signal that is a candidate for a specific signal used for specifying the other cell in the specific time interval;
A first detector for detecting a reception timing of the first synchronization signal;
A synchronization signal selection unit that determines a reception timing of a specific signal used for specifying the other cell included in the reception signal based on a reception timing of the first synchronization signal within the specific time interval;
A second detection unit that specifies the other cell using a specific signal used to specify the other cell acquired based on the determined reception timing ;
The synchronization signal selection unit sets a plurality of threshold values for dividing the specific time section into a plurality of sections, and compares the plurality of threshold values with the detected reception timing of the first synchronization signal. , mobile station, wherein that you determine the reception timing of a specific signal to be used for certain of the other cells included in the received signal.

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