JP2006319765A - Receiver for cdma, and cell search method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a receiver for CDMA by which shortening of processing time in cell search is achieved. <P>SOLUTION: The receiver for CDMA is loaded on a mobile machine adopting a CDMA system, performs three-step cell search and has, for example, a control part (5) which controls operations regarding the three-step cell search, a Step 1 processing part (12) which performs a Step 1 in a predetermined non-transmission section, an AD data recording reproduction part (15) which records received data at the same time as performance of the Step 1 and reproduces the recorded received data after completion of the Step 1, a Step 2 processing part (13) which performs a Step 2 using the received data to be reproduced by the AD data recording reproduction part (15) and a Step 3 processing part (14) which performs a Step 3 using the received data to be reproduced by the AD data recording reproduction part (15) after completion of the Step 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a CDMA receiving apparatus (hereinafter referred to as a receiving apparatus) that is mounted on a mobile station that employs a CDMA system and that performs a three-stage cell search, and in particular, a receiving apparatus that performs a cell search at different frequencies. And a cell search method thereof.

  In the W-CDMA system, in order to establish a radio link between a base station and a mobile device, the mobile device needs to establish downlink spread code synchronization. This process of establishing downlink spread code synchronization is called cell search, and detects a cell having a scramble code of a common pilot channel (CPICH: Common Pilot Channel) having the highest received power in the downlink. The cell search can be classified into, for example, an initial cell search for searching for a cell to which a radio link is connected when the power is turned on, a cell search for searching for a handover destination cell, and a cell search for searching for a cell to which a radio link is connected when waiting for communication. . Further, in the W-CDMA system, a three-stage cell search is adopted in order to realize a high-speed cell search.

Here, an outline of the three-stage cell search will be described. The theory of the three-stage cell search is described in detail in Non-Patent Document 1 below, for example.
(1) Step 1: The slot head timing is detected based on the result of correlation detection between the received signal and the PSC (slot timing detection).
(2) Step 2: For the detected slot timing, the frame timing is detected based on the correlation detection result between the received signal and the SSC. Further, the scramble code group is specified based on the SSC arrangement pattern.
(3) Step 3: Despreading is performed for all eight types of scramble code numbers belonging to the specified scramble code group, and the scramble code is specified from the comparison result of the correlation values.

Supervised by Keiji Tachikawa, "W-CDMA mobile communication system" Maruzen, August 10, 2001, P35-P45

According to the above conventional technology, the time that can be used for the cell search process and the cell detection performance are determined by the standard. From the following viewpoints, it is desired to achieve high speed and high performance of the cell search process. ing.
(1) Mobile device startup time reduction (reduction of time until call connection is possible)
(2) Smooth handover by detecting neighboring cells (cell search of the same frequency and different frequencies) that the mobile device can communicate with (3) Power consumption reduction by reducing the operation rate of the cell search processing unit

  Here, the problem in the cell search of the different frequency will be specifically described. FIG. 4 is a diagram illustrating a cell search operation at a different frequency in a conventional mobile device. For example, a cell search of a different frequency is performed in a gap (non-transmission period) when the compressed mode is executed. In FIG. 4, TGL # 1 and TGL # 2 represent gaps, and TGD represents the time until the second gap appears.

  In the cell search for different frequencies, as shown in FIG. 4, the process of “switching the reception frequency of the radio to a different frequency and executing the cell search process to restore the original frequency” is repeatedly executed in the gap. . Therefore, a plurality of gaps are required until cell search for one frequency is completed, and a certain amount of time is required (corresponding to “time required for one cell search process” in FIG. 4). Furthermore, when performing a cell search of a plurality of frequencies, a considerable time is required until all the processes are completed.

  Further, since Step 1, Step 2, and Step 3 in the cell search are distributed in a plurality of gaps, scheduling such as processing timing determination, frequency switching and return processing becomes complicated, and the burden on the control software increases.

  In addition, due to the influence of fading, the reception quality of P-SCH, S-SCH and CPICH signals varies at each stage of cell search Step 1, Step 2 and Step 3 (see the radio quality in FIG. 4), so detection at each stage There is a possibility that the rate varies and the cell detection performance is deteriorated. For example, FIG. 4 shows a case where the detection quality of Step 2 is poor compared to other Steps because the radio quality at the time of Step 2 is poor.

  The present invention has been made in view of the above, and an object of the present invention is to provide a CDMA receiving apparatus and a cell search method that can reduce processing time in cell search. It is another object of the present invention to provide a CDMA receiver and a cell search method capable of reducing the burden of control software related to cell search and improving cell detection performance.

  In order to solve the above-described problems and achieve the object, a CDMA receiving apparatus according to the present invention is installed in a mobile device adopting the CDMA scheme and executes CDMA that performs three-stage cell search (Step 1, Step 2, and Step 3). For example, a control means for controlling operations related to the three-stage cell search, a Step 1 processing means for executing Step 1 in a predetermined non-transmission section under the control of the control means, and a control of the control means Thus, the received data is recorded simultaneously with the execution of Step 1, and after Step 1 is completed, Step 2 is performed using the data recording / reproducing means for reproducing the recorded received data and the received data reproduced by the data recording / reproducing means under the control of the control means. Step 2 processing means for executing the process, and the control of the control means, Data recording and reproducing means is characterized by comprising a Step3 processing means for executing Step3 using the received data to be reproduced.

  According to the present invention, received data is recorded while Step 1 is executed, and after Step 1 is completed, the recorded data is reproduced and Step 2 and Step 3 are executed. There is an effect that the time can be greatly shortened.

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

  FIG. 1 is a diagram showing a configuration example of a receiving apparatus mounted on a mobile device adopting the W-CDMA system, that is, a receiving apparatus according to the present invention. The receiving apparatus includes a radio receiving unit 1 that performs general reception processing such as amplification of a signal received by an antenna and conversion of a radio frequency signal to a baseband frequency, and an A / D converter (A / D) 2. And a searcher unit 3, a finger unit 4, and a control unit (DSP) 5. The searcher unit 3 includes a Step 1 processing unit 12, a Step 2 processing unit 13, a Step 3 processing unit 14, a cell search processing unit 11 having an AD data recording / reproducing unit 15 for recording and reproducing a complex baseband signal, and a path search processing unit. 16.

  In the W-CDMA system, a three-stage cell search is adopted to realize a high-speed cell search, and a cell having a scramble code of a common pilot channel (CPICH: Common Pilot Channel) having the largest received power in the downlink is used. To detect. However, in CPICH, one frame is composed of 15 slots, one slot is composed of 10 symbols, and one symbol is composed of 256 chips. Also, “Primary Synchronization Channel: P-SCH” and “Secondary Synchronization Channel: S-SCH” are code-multiplexed and transmitted in the first 256 chip length section of each slot. Further, “Primary synchronization code: PSC” is used for spreading P-SCH, and “Secondary synchronization code: SSC” is used for spreading S-SCH. Further, PSC is common to all cells, and there are 16 types of SSCs. It is determined which type of SSC is assigned to slot # 0 to slot # 14 corresponding to 64 scramble code groups. (See 3GPP TS 25.213 V3.9.0 (2003-12), P21 to P23). Also, eight types of scramble code numbers are determined for one scramble code group, and the final goal of the cell search is to specify this scramble code.

  Here, a characteristic operation of the receiving apparatus according to the present embodiment will be described with reference to FIG. 1 and FIG. FIG. 2 is a diagram illustrating a cell search operation at a different frequency in the receiving apparatus according to the present embodiment.

  The Step 1 processing unit 12 sets the number of search slots (Ns 1) from the control unit 5, and then, after being instructed to start the search, detects the correlation between the complex baseband signal output from the A / D converter 2 and the PSC. And the number of paths set by the control unit 5, that is, slot timing candidates are selected in the descending order of correlation value (corresponding to “switch to different frequency” → “Step 1” → “return” in FIG. 2). Here, in the gap (corresponding to TGL # 1 in FIG. 2), a process of “switching to a different frequency and executing Step 1 to restore the frequency” is executed. Then, the phase information of each path (slot timing # 1, slot timing # 2,..., Slot timing #N) is notified to the control unit 5.

  At this time, the AD data recording / reproducing unit 15 stores the complex baseband signal output from the A / D converter 2 in the memory over the designated period based on the designated timing under the control of the control unit 5. (Equivalent to “AD data recording” in FIG. 2).

  In order to execute the above processing, the control unit 5 instructs the Step 1 processing unit 12 to start a search, and simultaneously instructs the AD data recording / reproducing unit 15 to store the complex baseband signal in the memory. To do.

  Next, after receiving the position information from the Step 1 processing unit 12 (after completion of the Step 1 processing), the control unit 5 does not wait for the next gap (corresponding to TGL # 2 in FIG. 2) and sends it to the Step 2 processing unit 13 The start of search is instructed, and at the same time, the AD data recording / reproducing unit 15 is instructed to reproduce the complex baseband signal stored in the memory. For example, the control unit 5 selects the slot timing candidate # 1 (maximum correlation path) from the slot timing candidates, obtains the memory start address at the time of reproduction based on the phase information, and sets it in the AD data recording / reproduction unit 15 (Reproduce from slot timing candidate # 1, see FIG. 3).

  The AD data recording / reproducing unit 15 reproduces the complex baseband signal recorded over the designated period from the designated head address under the control of the control unit 5 ("AD data reproduction # 1" in FIG. 2). Equivalent). In cell search Step 2, the frame timing and the scramble code group number cannot be specified unless three or more consecutive SSCs are detected. Therefore, the accumulation / playback period (memory capacity) of the AD data recording / playback unit 15 is 3 slots. The above is set.

  In addition, the Step 2 processing unit 13 sets the number of search slots (Ns2) under the control of the control unit 5 and then instructs the start of the search, and then the complex baseband signal reproduced by the AD data recording / reproducing unit 15 Correlation detection with the SSC is performed, the scramble code group and the frame timing are specified by the SSC arrangement pattern (corresponding to “Step 2” in FIG. 2), and the result is notified to the control unit 5.

  Next, after receiving the scramble code group and the frame timing from the Step 2 processing unit 13 (after completion of the Step 2 processing), the control unit 5 does not wait for the next gap (corresponding to TGL # 2 in FIG. 2) without performing Step 3 processing. The unit 14 is instructed to start the search, and at the same time, the AD data recording / reproducing unit 15 is instructed to reproduce the complex baseband signal stored in the memory again (the start address and the reproduction period are, for example, Step 2 search Set the same as the time).

  Also in this case, the AD data recording / reproducing unit 15 reproduces the complex baseband signal recorded over the designated period from the designated head address under the control of the control unit 5 (“AD data reproduction # in FIG. 2). 2 ”).

  Further, the Step 3 processing unit 14 sets the number of search slots (Ns3) under the control of the control unit 5 and then instructs the start of search, and then the complex baseband signal reproduced by the AD data recording / reproducing unit 15 The scramble code multiplied by the received signal is obtained by despreading the CPICH using the eight scramble codes belonging to the scramble code group specified by the Step 2 processing unit 13 and detecting the maximum correlation value. It identifies (corresponds to “Step 3” in FIG. 2) and notifies the control unit 5 of the result.

  As described above, in the present embodiment, the complex baseband signal is recorded in the memory while executing the cell search Step1, and after the cell search Step1 is completed, the recorded data is reproduced and the cell search Step2 and Step3 are executed. did. As a result, the cell search for different frequencies can be changed per frequency, for example, to the process shown in FIG. 2 (corresponding to “time required for one cell search process” shown in FIG. 2). The time required for this can be greatly reduced.

  Further, in the present embodiment, for example, as shown in FIG. 2, since one frequency cell search can be processed with one gap, scheduling such as processing timing determination, frequency switching and return processing can be simplified, As a result, the burden of the control software related to cell search can be reduced. In addition, since the operation rate related to the cell search process can be reduced by shortening the processing time and reducing the burden of the control software, it is possible to reduce the power consumption of the entire mobile device.

  Furthermore, in the present embodiment, since cell reception Step 1, Step 2, and Step 3 can use received signals in the same interval, cell detection caused by fading or the like compared to the case of using different received signals at each stage. Performance degradation can be suppressed.

  In the above description, the case where there is one Step 2 processing unit 13 has been described. However, in the present embodiment, for example, M Step 2 processing units 13 are prepared and the paths detected by the Step 1 processing unit 12 (slot timing candidates) ) (For example, slot timing # 1, slot timing # 2,..., Slot timing #M), and then each Step 2 processing unit 13 may execute Step 2. Specifically, for example, the control unit 5 sets an address corresponding to the slot timing first found at Step 1 as the memory start address at the time of reproduction given to the AD data recording / reproducing unit 15. Then, the control unit 5 individually assigns slot timing # 1, slot timing # 2,..., Slot timing #M to each Step 2 processing unit 13, and further individually determines the number of search slots (Ns2 (1), Ns2 (2),..., Ns2 (M)) are set. Thereafter, the control unit 5 instructs the AD data recording / reproducing unit 15 to start reproduction, and further instructs each Step 2 processing unit 13 to start searching at the reproduction start time of each slot timing. When performing these processes, M Step 3 processing units 14 are prepared, AD data is reproduced in the same manner as Step 2, and the M Step 3 processing units 14 execute Step 3. Thereby, a cell search can be executed for a plurality of slot timing candidates without increasing the memory (AD data recording / reproducing unit).

  As described above, the receiving apparatus and the cell search method according to the present invention are useful for a mobile device that adopts the CDMA scheme, and are particularly suitable for a mobile device that performs a cell search of a different frequency.

It is a figure which shows the structural example of the receiver concerning this invention. It is a figure which shows the operation | movement of the cell search of the different frequency in the receiver concerning this invention. It is a figure which shows an example of data reproduction. It is a figure which shows the operation | movement of the cell search of the different frequency in the conventional mobile apparatus.

Explanation of symbols

1 Wireless receiver 2 A / D converter (A / D)
3 Searcher part 4 Finger part 5 Control part (DSP)
DESCRIPTION OF SYMBOLS 11 Cell search process part 12 Step1 process part 13 Step2 process part 14 Step3 process part 15 AD data recording / reproducing part 16 Path search process part

Claims (9)

In a CDMA receiving apparatus that is mounted on a mobile device that adopts the CDMA scheme and performs a three-stage cell search (Step 1, Step 2, Step 3),
Control means for controlling operations related to the three-stage cell search;
Step 1 processing means for executing Step 1 in a predetermined no-transmission section under the control of the control means;
Under the control of the control means, data recording / reproducing means for recording the received data simultaneously with the execution of Step 1 and reproducing the recorded received data after Step 1 is completed;
Step 2 processing means for executing Step 2 using received data reproduced by the data recording / reproducing means under the control of the control means;
Step 3 processing means for executing Step 3 using received data reproduced by the data recording / reproducing means after Step 2 is completed under the control of the control means;
A receiving device for CDMA, comprising:   2. The CDMA receiver according to claim 1, wherein reception data in the same section is used in Step 1, Step 2, and Step 3.   3. The CDMA receiver according to claim 1, wherein after completion of Step 1, Step 2 and Step 3 are executed without waiting for a next non-transmission section.   The control means obtains a head address at the time of reproduction of received data based on phase information relating to a slot timing candidate detected by executing Step 1, and designates the head address to the data recording / reproduction means. The CDMA receiver according to claim 1, 2, or 3.   5. The CDMA according to claim 4, wherein the data recording / reproducing means records received data for a specified period, and further reproduces the received data recorded for a specified period from the head address. Receiving device.   M (an integer greater than or equal to 2) Step 2 processing means and Step 3 processing means are prepared, and Step 2 and Step 3 are executed for M candidate units selected from the slot timing candidates detected by the Step 1 processing means. The CDMA receiver according to any one of claims 1 to 5, wherein: A cell search method when a mobile station adopting a CDMA system performs a three-step cell search (Step 1, Step 2, Step 3),
A first step of executing Step 1 in a predetermined non-transmission section;
A second step of recording received data simultaneously with execution of Step 1;
A third step of reproducing the reception data recorded in the second step after Step 1 is completed;
A fourth step of executing Step 2 using the received data reproduced in the third step;
A fifth step of reproducing the received data recorded in the second step after Step 2 is completed;
A sixth step of executing Step 3 using the reception data reproduced in the fifth step;
A cell search method characterized by comprising:   The cell search method according to claim 7, wherein reception data in the same section is used in Step 1, Step 2, and Step 3. The cell search method according to claim 7 or 8, wherein after Step 1 is completed, Step 2 and Step 3 are executed without waiting for the next non-transmission section.

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