JP2006237983A - Path detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a path detector capable of preventing a path from improperly being changed in tracking. <P>SOLUTION: A phase shift amount storage section 108 stores a phase shift amount in past decoding and current decoding. An identical path detection section 109 checks the phase shift of each finger processing section 103 to detect a path whose difference is equal to or less than a certain threshold. A path deletion decision section 110 checks the phase shift amount in the phase shift amount storage section 108 corresponding to paths detected by the identical path detection section 109 to delete a path with a large phase shift amount and outputs the reverse spread result of an undeleted path. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a path detection apparatus in a mobile communication system using a direct spreading code division multiple access (DS-CDMA) system.

  In a path detection circuit in a CDMA receiver, it is known that tracking, which is a process for finely adjusting a path phase, is effective for each path (see Patent Document 1). When tracking is repeatedly performed, the phase of the same path originally assigned to different fingers may have the same value. Assigning multiple fingers in the path of the same phase, since there is only the number of fingers, it is necessary to remove one of the paths can not be assigned to fingers of a valid path that appeared later. Correspondingly, when deleting a path, if a path whose phase has not changed by tracking is deleted and a path whose phase has changed is left, the path appears to be switched. Such a phenomenon is referred to as a path exchange in this specification.

Further, in the path selection, it is said that the reception performance is improved when the path is not selected in the vicinity of the selected path (hereinafter referred to as the same path) (see Non-Patent Document 1).
Japanese Patent Laid-Open No. 10-173630 IEICE technical report RCS97-164

  However, this Non-Patent Document 1 does not disclose a specific improvement method, although there is a suggestion about path selection in the vicinity of the selected path. In addition, in the conventional path detection apparatus, when there are a plurality of identical paths, an arbitrary path is deleted, so that there is a problem that the paths are replaced by tracking and reception performance deteriorates.

  For example, in the DS-CDMA system, generally, when performing synchronous detection, a phase correction value is calculated using known symbols at a plurality of timings before and after in order to improve reliability. However, using a symbol whose phase is changed by tracking is equivalent to correcting with phase information at another timing. In addition, in the phase rotation amount correction and the reception quality detection, if a symbol that varies due to tracking is used, the accuracy deteriorates by an amount corresponding to the variation due to the same reason.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a path detection device capable of preventing paths from being switched by tracking.

  The path detection apparatus of the present invention includes a path selection unit that selects a plurality of paths from a received signal, a tracking control unit that finely adjusts the path phase of the selected path, and a phase at the time of past decoding and a time of current decoding. Phase variation amount storage means for obtaining and storing the amount of change, same path detection means for determining a path having a phase difference within a predetermined range as the same path among the selected paths, and the same path by the same path detection means Between the determined paths, a configuration including path deletion determination means for deleting a path having a relatively large phase change amount is employed.

  According to the present invention, it is possible to prevent paths from being switched by detecting a phase change amount and selecting a path from which a path having a large phase change is deleted.

  Hereinafter, a path detection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram of a path detection apparatus 100 according to Embodiment 1 of the present invention.

  In FIG. 1, a path detection apparatus 100 inputs a digital signal obtained by subjecting an analog signal received by a receiving antenna 101 to frequency conversion processing, filtering processing, A / D conversion processing, and the like. The path detection apparatus 100 includes a plurality of finger processing units 103-1 to 103-n that perform processing for each path. The path selection unit 102 designates the path phase calculated using the delay profile generated from the received signal for each finger processing unit 103.

  The despread code generation unit 104 generates a despread code corresponding to the path phase designated by the path selection unit 102. The delay unit 105 delays the despread code generated by the despread code generation unit 104 by a phase for fine adjustment by tracking, and generates a plurality of sets of tracking despread codes.

  Each of the despreading units 106-1 to 106-m performs despreading by multiplying the reception signal from the reception antenna 101 by the tracking despreading code output from the delay unit 105, and the result is obtained as a correlation value. Output as power.

  The tracking control unit 107 compares the power of the correlation value output from each of the despreading units 106-1 to 106-m, selects the phase with the largest correlation value power, and decodes it from a plurality of despread signals. Select the power signal and its phase.

  The phase variation storage unit 108 stores the amount of phase change between the previous decoding and the current decoding.

  The same path detection unit 109 checks the phase difference between the finger processing units 103-1 to 103-n, and detects a path having a phase difference equal to or less than a threshold value as the same path. That is, a group of paths whose phases are recognized as being in the vicinity are detected.

  The path deletion determination unit 110 checks the phase change amount in the phase variation storage unit 108 corresponding to each path of the same path detected by the same path detection unit 109 and deletes a path having a relatively large phase change amount. . Further, the despread result of the path that is not deleted, that is, the despread result of the remaining path is used as a decoding result, and data is output to a circuit (not shown) in the subsequent process such as a path synthesis unit, and the phase shift in the deleted path and tracking Information is output to the path selection unit 102.

  The operation of the path detection apparatus configured as described above will be described with reference to FIG. FIG. 2 is a diagram modeling the operation of the selected path, with the reception level on the vertical axis and the delay time (phase) on the horizontal axis.

  Assume that the reception signal shown in FIG. 2 is input to the reception antenna 101 and that the finger a and the finger b are currently selected by the path selection unit 102. In this case, the despreading unit 106 for the finger a has the timing of the tracking timing (phase) 1, finger timing (phase) a, and tracking timing (phase) 2 shown in FIG. Despreading is performed, and tracking 2 having the highest reception level is selected by tracking control section 107, and the phase of finger a is updated to the timing of tracking 2. Similarly, as shown in FIG. 2, despreading is performed on finger b at the timing of tracking timing (phase) 2 and tracking timing (phase) 3 before and after finger timing (phase) b. Is the timing of finger b, the tracking control unit 107 does not change the phase, and finger b is continuously selected. Therefore, if there is no change in the received signal now, the tracking control for checking the correlation value before and after the path phase and changing the phase to the larger correlation value is continued. As shown in the case of FIG. Are sequentially shifted to the finger b side, so that the same timing as that of the finger b is reached, and the same path detection unit 109 determines that the finger a and the finger b are the same path.

  The path deletion determination unit 110 selects a path to be deleted from the information in the phase fluctuation amount storage unit 108, and in the case of FIG. 2, deletes the finger a whose phase has fluctuated.

  According to such a path detection apparatus of the first embodiment of the present invention, by providing means for selecting a path to be deleted based on the phase change amount, any one of the paths having the same phase assigned to the plurality of fingers is deleted. In this case, since the path whose phase has changed can be deleted, it is possible to prevent the paths from being switched.

  In the above description, the path to be deleted is selected only by the phase change amount. However, the reception level after despreading of tracking 1, finger a, and tracking 2 may also be used for path deletion determination. In this case, when the propagation path is changed and the path phase to be originally set is changed, the path deletion processing can be performed in consideration of the reception state without deleting the changed path phase.

(Embodiment 2)
Next, a path detection apparatus according to Embodiment 2 of the present invention is shown in a block diagram in FIG. In FIG. 3, the same components as those shown in the first embodiment in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. Here, the description will be focused on the portion related to the second embodiment.

  As shown in FIG. 3, the path detection apparatus 200 according to the second embodiment has a delay profile generation unit 201 added in comparison with the configuration shown in FIG. 1 (first embodiment), and the path deletion determination unit 110. Are different from the path deletion determination unit 203 in reference numerals.

  In the above configuration, the delay profile generation unit 201 calculates the magnitude of the correlation value at each phase, and the path deletion determination unit 203 has an internal phase fluctuation amount storage unit 108 detected by the same path detection unit 109. The path to be deleted can be selected by comparing the amount of phase timing change due to and the magnitude of the correlation value by the corresponding delay profile generation unit 201. Specifically, the correlation value based on the delay profile of each path is stored, and when a path to be deleted in the same path range occurs, the stored correlation values are compared, and one of them is greater than a predetermined threshold value. If you leave that path. If it is below this predetermined threshold, the same operation as in the first embodiment is performed.

  As described above, according to the path detection device 200 according to the second embodiment of the present invention, by performing path deletion determination using the correlation value based on the delay profile and the phase timing change amount, the tracking operation is performed when the correlation value is large. Since it is stable, it is possible to perform path deletion processing taking into account fluctuations in the reception state.

  As described above, the path detection apparatus according to the present invention has an effect of preventing the path from being switched by providing means for selecting a path to be deleted based on the phase change amount, and has direct spreading code division multiple access (DS). This is useful as a path detection apparatus in a mobile communication system using the (CDMA) method.

1 is a block diagram of a path detection device according to Embodiment 1 of the present invention. Modeled diagram for explaining the operation of path deletion in Embodiment 1 of the present invention Block diagram of the path detection apparatus in Embodiment 2 of the present invention

Explanation of symbols

100, 200 Path detection device 101 Receiving antenna 102 Path selection unit 103 Finger processing unit 104 Despreading code generation unit 105 Delay unit 106 Despreading unit 107 Tracking control unit 108 Phase fluctuation amount storage unit 109 Same path detection unit 110, 203 Path deletion Determination unit 201 Delay profile generation unit

Claims (2)

Path selection means for selecting a plurality of paths from the received signal;
Tracking control means for finely adjusting the path phase of the selected path;
A phase variation storage means for obtaining and storing a phase change amount at the time of past decoding and at the time of this decoding;
The same path detection means for determining a path having a phase difference within a predetermined range as the same path among the selected paths;
Between the paths determined to be the same path by the same path detection means, a path deletion determination means for deleting a path having a relatively large phase change amount;
A path detection apparatus comprising: A delay profile generating means for creating a delay profile of the received signal and outputting a correlation value of the delay profile to the path deletion determining means;
The path detection apparatus according to claim 1, wherein the path deletion determination unit selects a path to be deleted according to the changed phase amount and the correlation value of the delay profile.

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