JP2007110478A - CDMA receiver - Google Patents

Abstract

Provided is a CDMA receiver which can reduce processing after a useless second-stage search and can detect a weak electric field cell.
In a profile creation unit, the correlation power output from a PSCH correlation power calculation unit is accumulated and accumulated for each phase point, and the result is obtained when the accumulation of correlation power of a desired number of symbols is completed. It is output to the peak detection / path management processing unit 104. The path management table 103 holds path table information detected and managed in the past. The peak detection / path management processing unit 104 repeatedly executes slot timing detection in the first stage cell search of the three stage cell search, refers to the path management table 103, and determines the path from the correlation power value information of the past detection results. State management is performed every time, and candidate paths after the second stage cell search are determined according to the state.
[Selection] Figure 1

Description

  The present invention relates to a CDMA (Code Division Multiple Access) receiving apparatus applied to a mobile communication system that performs multiple access using spread spectrum, and in particular, a CDMA reception that performs a three-stage cell search to detect an unknown cell. Relates to the device.

  Conventionally, various literatures have disclosed cell search methods by W-CDMA receivers that employ a W-CDMA (Wideband-Code Division Multiple Access) system (see, for example, Patent Document 1). This technique detects the maximum correlation detection path from the detection paths, and corrects the correlation value for the multipath around the received maximum correlation detection path, so that the top n paths in the corrected correlation value And the reception timings of the extracted n paths are assigned to the second synchronization establishing means. As a result, the most probable path can be extracted in the shortest time as much as necessary. Also, according to the cell search method according to this technique, a mobile device such as a mobile terminal receives a PSCH (Primary Synchronization CHannel) and an SSCH (Secondary Synchronization Channel) in order to establish synchronization with the base station. .

  FIG. 4 is a diagram illustrating transmission timings of PSCH, SSCH, and CPiCH (Common Pilot CHannel) by a general W-CDMA receiver. In FIG. 4, PSCH is the same code for each slot. In the W-CDMA receiver of the mobile device, the slot phase is acquired by detecting the PSCH transmitted from the base station. Such processing corresponds to the first stage cell search of a general three stage cell search. The SSCH is a code different for each slot, and the combination is determined for each scrambling code group. A W-CDMA receiver of a mobile device acquires a frame phase and a scrambling code group by detecting a combination of SSCHs transmitted from a base station. Such processing corresponds to the second stage cell search of a general three stage cell search. Also, the W-CDMA receiver of the mobile device identifies the scrambling code by detecting the CPiCH using the acquired frame phase for the scrambling code narrowed down by the acquired scrambling code group. Such processing corresponds to a third stage cell search of a general three stage cell search.

  FIG. 5 is a diagram showing a configuration of a first stage cell search processing function of a three stage cell search in a conventional W-CDMA receiver. In FIG. 5, the first stage cell search processing function 1 in the conventional W-CDMA receiver includes a PSCH correlation value power calculator 2, a profile generator 3, and a peak detector 4. The PSCH correlation value power calculation unit 2 has a function of calculating the correlation power of the PSCH from the received signal (the signal after the reception amplifier) and outputting the calculated correlation power to the profile creation unit 3. The profile creation unit 3 accumulates and accumulates the correlation power output from the PSCH correlation value power calculation unit 2 for each phase, creates a correlation power delay profile as a result, and sends the correlation power delay profile to the peak detection unit 4. It has a function to output. The peak detection unit 4 detects a peak value exceeding a predetermined threshold based on the correlation power delay profile output from the profile creation unit 3, and performs a cell search for the detected peak value and peak phase (slot phase information). It has a function to output as a one-stage result.

  Next, the process flow of the first stage cell search processing function 1 in the conventional W-CDMA receiver configured as described above will be described. The PSCH correlation value power calculation unit 2 receives a reception signal that has been subjected to AGC (Automatic Gain Control) processing by an RF unit (not shown), performs PSCH despreading by a sliding correlator, and the like, and performs correlation power for each sample point. Is output to the profile creation unit 3. In the profile creation unit 3, the correlation power output from the PSCH correlation value power calculation unit 2 is accumulated and accumulated for each phase point. Then, when the accumulation of correlation power for the desired number of symbols is completed, the result is output to the peak detector 4. FIG. 6 is a diagram illustrating an example of peak detection processing in the peak detection unit 4 of FIG. 5, where the horizontal axis represents the phase and the vertical axis represents the correlation power value. As shown in an example of the peak detection process in FIG. 6, the peak detection unit 4 shown in FIG. 5 generally detects a correlation power value p1 exceeding a predetermined threshold value p0, and the slot phase information is the cell search first. Output as one-step result. In such a cell search, an unknown cell is detected through a second-stage cell search and a third-stage cell search process based on the cell search first-stage result.

In mobile devices, it is important to keep the power consumption and search time required for such a three-stage cell search small, and various proposals have been studied to reduce power consumption and search time during cell search. (For example, refer to Patent Document 2). In the technique of Patent Document 2, the phase information of the wind search result of the captured perch is used as an input, the phase periphery of the path of the captured perch is masked, and the search results of the other parts after the second stage cell search Therefore, the total amount applied to the cell search process is reduced, thereby reducing the power consumption and the search time during the cell search. In other words, according to this technology, in the asynchronous inter-station system in a plurality of base stations, while taking advantage of the advantages, the power consumption and search time required for the mobile device to perform cell search are reduced, and the cost of the entire communication system is increased. Neighboring cell search is controlled so as not to be caused.
JP 2002-141886 A JP 2001-78245 A

  However, it is difficult to optimize the threshold setting for peak detection in the configuration of the conventional W-CDMA receiver in the mobile device. For example, if the threshold value is high, a cell with a weak electric field cannot be detected. Conversely, if the threshold value is low, noise is detected as a detection candidate, and a wasteful search operation is performed after the second-stage cell search process. In addition, when a plurality of cell detection candidates are found, in general, they are targeted for processing after the second stage cell search in descending order of the correlation power value. For this reason, detection of a potential candidate cell of HHO (Hard Hand Over) in the moving direction of the mobile device is delayed, so that it is impossible to perform processing suitable for high-speed movement of the mobile device.

  The present invention has been made in view of such a point, and by providing the cell search in the first stage with a path management processing function that takes into account information of past detection results, the unnecessary second and subsequent stages are provided. An object of the present invention is to provide a CDMA receiver that eliminates cell search processing and can detect weak electric field cells.

  In order to solve the above-described conventional problems, a CDMA receiver of the present invention is a CDMA receiver in a mobile device of an asynchronous system between CDMA base stations that performs a three-stage cell search using spread spectrum, and has been detected in the past. The slot timing detection in the first-stage cell search of the three-stage cell search and the path management table with reference to the path management table to correlate the detection results of the past multiple times. A configuration is adopted in which state management is performed for each path from the power value information, and a peak detection / path management processing unit that determines candidate paths after the second-stage cell search according to the state.

  In the CDMA receiver according to the present invention, in the configuration of the invention, the peak detection / path management processing unit performs path state management by adding phase change information of a plurality of past times to an element, and the phase is advanced to a predetermined value or more. The path is preferentially selected as a candidate after the second stage search.

  According to the CDMA receiver of the present invention, in the first stage cell search, the ratio of detecting noise and performing unnecessary operations after the second stage cell search is reduced, and the detection of weak electric field cells is also possible. . As a result, it is possible to provide a CDMA receiver with low power consumption and short search time. In addition, by enabling preferential detection of cells in the destination direction that are highly likely to be suitable for the HHO destination, it is possible to provide a CDMA receiving apparatus in which communication is not easily interrupted even when a mobile device moves at high speed. .

<Summary of invention>
The CDMA receiving apparatus of the present invention has a path management processing function that takes into account information of past detection results in the first stage cell search processing function. This makes it possible to perform candidate path detection that takes into account past correlation power values for each path, instead of just determining correlation power values in a single cell detection. Therefore, the ratio of noise as detection candidates can be reduced, and weak electric field cells can be detected. Also, not only the correlation power value but also the phase information is managed for each path, and the path whose phase is faster than a certain speed (that is, the path that is likely to be close to the mobile device) is given priority. By using the candidate path as a candidate path, it is possible to preferentially detect a cell that seems to be in the destination direction. As a result, even if the mobile device is moving at a high speed, it is difficult to disconnect communication.

  Hereinafter, some of the embodiments of the CDMA receiver according to the present invention will be described in detail with reference to the drawings. However, the description overlapping in each embodiment is omitted as much as possible.

<Embodiment 1>
FIG. 1 is a diagram showing a configuration of a first stage cell search processing function of a three stage cell search in the W-CDMA receiver according to Embodiment 1 of the present invention. In FIG. 1, the first stage cell search processing function 100 calculates PSCH correlation power from a received signal (signal after reception amplifier) and outputs the calculated correlation power, and a PSCH. A profile creation unit 102 that accumulates and accumulates the correlation power output from the correlation value power calculation unit 101 for each phase, creates a correlation power delay profile as a result, and outputs the correlation power delay profile, and detects in the past The path management table 103 that holds the path table information managed and the output result of the correlation power delay profile of the PSCH from the profile creation unit 102, and the phase update (tracking) and correlation value for each path in the path management table 103 Peak detection / path management that updates power history information and performs integrated processing of close paths, etc. It has a configuration that includes a processing section 104.

  Next, the process flow of the first stage cell search processing function 100 in the conventional W-CDMA receiver configured as shown in FIG. 1 will be described. When the PSCH correlation value power calculation unit 101 inputs the signal after the receiving amplifier, the profile generation unit 102 accumulates and accumulates the correlation power output from the PSCH correlation value power calculation unit 101 for each phase point, thereby obtaining a desired symbol. When the accumulation of the number of correlation powers is completed, the result is output to the peak detection / path management processing unit 104. The path management table 103 holds path table information detected and managed in the past, and the peak detection / path management processing unit 104 repeatedly executes slot timing detection in the first stage cell search of the three stage cell search. Then, state management is performed for each path from the correlation power value information of a plurality of past detection results with reference to the path management table 103, and candidate paths after the second stage cell search are determined according to the state. In this way, the path management table 103 and the peak detection / path management processing unit 103 are provided in order to detect path candidates that are output to the second stage search, and the past detection result information is also used for detection determination. I have to.

  The process flow of the first stage cell search processing function 100 will be described in more detail. The PSCH correlation value power calculation unit 101 receives a reception signal after reception amplifier that has been subjected to AGC processing or the like by an RF unit (not shown), performs despreading of PSCH by a sliding correlator, etc., and calculates correlation power for each sample point. Output to the profile creation unit 102. The profile creation unit 102 accumulates and accumulates the correlation power output from the PSCH correlation value power calculation unit 101 for each phase point. Then, when the accumulation of correlation power for the desired number of symbols is completed, the result is output to the peak detection / path management processing unit 104.

  On the other hand, the path management table 103 is information of a path table that has been detected and managed in the past, and includes phase information, correlation power history information, information on known cells and unknown cells, and cell IDs and unknowns for known cells. Information such as the elapsed time since the previous second-stage cell search process for a cell is executed is held. Information stored in the path management table 103 is updated by the peak detection / path management processing unit 104 as needed.

  The peak detection / path management processing unit 104 receives the output result of the PSCH correlation power delay profile from the profile creation unit 102, updates the phase for each path (tracking) and the correlation value power history information in the path management table 103. Also, the integrated processing of closer paths is performed.

  In addition, the peak detection / path management processing unit 104 detects the peak of the correlation power value, and newly registers a new path that is not registered in the path management table 103. Further, the peak detection / path management processing unit 104 updates the known cell / unknown cell information from the known cell / path information and the information on the path that failed to be detected in the second stage search / third stage search, The elapsed time since the cell search process in the second stage of the previous cell ID / unknown cell is updated.

  Finally, the peak detection / path management processing unit 104, if there is an unknown cell and a probable detection candidate in the path management table 103, proceeds to the cell search process of the second stage, and the result candidate path of the cell search first stage. Send out as The path information that failed in the second stage cell search / third stage cell search is information in which a probable candidate path sent as a detection result to the second stage cell search in the past failed to detect an unknown cell. Therefore, the cells are classified as undetected and known cells.

  Note that the known cell / path information input to the peak detection / path management processing unit 104 is information obtained from a window search result using CPiCH for periodic measurement of known cells and finger assignment of a cell in communication. Assumed.

  FIG. 2 is a diagram showing an example of path management processing performed by the first stage cell search processing function according to the first embodiment of the present invention. In other words, this figure shows the correlation power value / phase of the output result of the correlation power delay profile of the PSCH for the registered path after the update of the path management table 103. The phase in the slot is shown, and the correlation power value is shown on the vertical axis.

  The peak detection / path management processing unit 104 performs state management by evaluating the correlation power value of the path by using two types of threshold values, threshold value H and threshold value L, in the upper diagram of FIG. The threshold value H is a threshold value for a path that exceeds the value (that is, the threshold value H) and is sufficiently strong to output a detection result to processing after the cell search in the second stage, unlikely to be considered as noise. The threshold value L that instantaneously exceeds the value (that is, the threshold value L) may be noise, but if the threshold value L stably exceeds the value (threshold value L) over multiple detections, the candidate path As a threshold for a second-stage search candidate.

  The lower diagram of FIG. 2 shows an enlarged correlation power delay profile in which the path (2) of the unknown cell in the upper diagram is enlarged. As shown in the lower diagram of FIG. 2, there is a path (noise) exceeding the threshold L in addition to the path of the cell to be detected, but these paths are unlikely to exceed the threshold L in the next delay profile creation. If only the paths exceeding the number of consecutive times are picked up, the possibility of outputting noise as a candidate becomes very small.

  Next, in this case, it is evaluated whether the result is output as a candidate path to the second stage search except for the path of the known cell in the upper diagram of FIG. First, the path (1) of the unknown cell having the maximum correlation power value is evaluated. Since the path (1) of this unknown cell exceeds the threshold value H, it is immediately output as a candidate path for the second stage search.

  Next, the path (2) of the unknown cell is evaluated. Since the threshold value H is not exceeded but the threshold value L is exceeded, the past state is confirmed, and if it exceeds the threshold value L for a certain number of times, it is output as a candidate path for the second stage search. Similarly, since the path (3) of the unknown cell does not exceed the threshold value H but exceeds the threshold value L, the past state is confirmed, and if the threshold value L is continuously exceeded a predetermined number of times, the second stage search is performed. Are output as candidate paths.

  In addition, there is a high possibility that a path that has been output as a candidate path but could not be detected in the second-stage search and third-stage search will not be detected next time. Do not execute the correct operation.

  According to the cell search of the first embodiment, if the path is a weak electric field cell, the effectiveness is evaluated through a plurality of first-stage search results and output as candidate paths after the second-stage search. Unnecessary operations after the second stage search can be reduced, and a weak electric field cell can be detected.

<Embodiment 2>
The configuration of the first stage cell search processing function 100 of the three stage cell search in the W-CDMA receiving apparatus of the second embodiment of the present invention is the same as that of the first embodiment, but the second embodiment is the first embodiment. The path management table 103 is configured to have phase history information so as to grasp the phase change of the path based on the past first-stage search results.

  That is, when detecting a candidate path to the second-stage cell search from the unknown cell path, the history information of the phase is evaluated in addition to the evaluation of the magnitude of the correlation power value. Then, from the evaluation result of the phase history information, the priority order of the path candidates to be output to the second stage search is set as follows.

The first priority is a path that exceeds the threshold value H and that has a phase that is earlier than a certain time in a certain period.
The second priority is a path that exceeds the threshold value H and is a path other than the condition of the first priority.
The third priority is a path other than the first priority and the second priority that has exceeded the threshold L over a plurality of past detections, and whose phase is earlier than a certain time in a certain period.
The fourth priority order is a path other than the first priority order and the second priority order, and is a path other than the third priority order that has exceeded the threshold L over the past multiple detections.

  As described above, the cell search according to the second embodiment makes it possible to preferentially detect a cell in the moving destination direction that is highly likely to be suitable for the HHO destination, and CDMA is difficult to disconnect even when the mobile device moves at high speed. A receiving device can be realized.

  FIG. 3 is a diagram showing an example of path management processing performed by the first stage cell search processing function according to the second embodiment of the present invention. As shown in FIG. 3, a mobile station MS that is moving at high speed is communicating with Cell # A, and an unknown cell Cell # B that is in the moving direction and a direction opposite to the moving direction of the mobile station are in the vicinity. An unknown cell Cell # C exists.

  At present, as shown in FIG. 3, the unknown cell Cell # C is closer to the mobile station MS than the unknown cell Cell # B, and the first-stage search result shows that the unknown cell Cell # C has higher correlation value power. ing. In general, since a path having a large correlation value power is preferentially detected, the second stage search is detected in the order of the path of unknown cell Cell # C and the path of unknown cell Cell # B. In the example of the form 2, the path of the unknown cell Cell # B has an earlier phase, and the path of the unknown cell Cell # C has a slower phase. Therefore, the path of the unknown cell Cell # B, the unknown cell Cell # B It becomes the detection target of the second stage search in the order of the C path. As a result, the unknown cell Cell # B existing in the moving direction suitable for the HHO destination can be detected earlier.

  In addition, when there are many effective cells being captured, a candidate path whose phase is delayed (that is, a path of a cell that is likely to be further away from the mobile station) is a candidate path for the second stage search. By not outputting, it is possible to reduce power consumption while maintaining communication quality.

  The CDMA receiving apparatus according to the present invention can eliminate unnecessary processing in cell search and perform cell detection of a weak electric field, so that it can be effectively used for a mobile device for high-speed movement.

The figure which shows the structure of the 1st step cell search processing function of the 3 step | paragraph cell search in the W-CDMA receiver of Embodiment 1 and Embodiment 2 of this invention. The figure which shows an example of the path management process which the 1st step cell search process function of Embodiment 1 in this invention performs The figure which shows an example of the path management processing which the 1st step cell search processing function of Embodiment 2 in this invention performs The figure which shows the transmission timing of PSCH, SSCH, and CPiCH by a general W-CDMA receiver. The figure which shows the structure of the 1st step cell search processing function of the 3 step | paragraph cell search in the conventional W-CDMA receiver. The figure which shows an example of the peak detection process in the peak detection part of FIG.

Explanation of symbols

100 First Stage Cell Search Processing Function 101 PSCH Correlation Value Power Calculation Unit 102 Profile Creation Unit 103 Path Management Table 104 Peak Detection / Path Management Processing Unit

Claims (2)

A CDMA receiver in a mobile device of an asynchronous system between CDMA base stations that performs a three-stage cell search using spread spectrum,
A path management table having path table information detected and managed in the past;
The slot timing detection in the first stage cell search of the three stage cell search is repeatedly executed, the state management is performed for each path from the correlation power value information of the past detection results by referring to the path management table, and the state A peak detection / path management processing unit for determining candidate paths after the second stage cell search according to
A CDMA receiving apparatus comprising:   The peak detection / path management processing unit performs path state management by adding phase change information of a plurality of past times to an element, and preferentially selects a path whose phase is earlier than a predetermined value as a candidate after the second stage search. The CDMA receiver according to claim 1, wherein:

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