Title of Invention | MULTI-PATH SEARCHING |
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Abstract | A method of multi-path searching in a cellular network in which a multi-path searcher is provided which carries out a correlation process over a predetermined integration period in relation to a first pilot signal received in connection with a first cell of the cellular network to identify the position of multi-paths in the signal and the multi-path searcher for multi-path searching in a cellular network by carrying out a correlation process over a predetermined integration period in relation to a first pilot signal received in connection with a first cell of the cellular network to identify the position of multi-paths in the signal. |
Full Text | This invention relates to method of multi-path searching in cellular network and multi-path searcher for the same. A mobile handset has to be designed to accommodate multi-path signals that may be present in the received signal, and for this purpose it incorporates a multi-path searcher which identifies the strongest of the multi-path signals to use. In a Wide band Code Division Multiple Access system, the Common Pilot Channel (CPICH) contains a predetermined sequence of pilot bits spread with known channelisation codes and scrambled with mown scrambling codes, and the multi-path searcher makes measurements on the CPICH signal by correlating this against the known CPICH scrambled chip sequence to identify the path positions and select a sub-set to use for decoding. The multi-path searcher consists of multiple correlators which each process the same scrambling sequence and channelisation code to carry out a correlation measurement on the received signal after it has been delayed by a different time delay at the input of each correlator, the multiple correlation measurements so generated being analysed in relation to the time delays to identify the multi-path positions. In order to improve the accuracy and reliability in detecting path positions, the correlation process is extended over an integration time sufficient to identify the path positions above the noise floor of the signal. However, an increase in integration time results in an increase in processor/ASIC size and power consumption, which in turn leads to an increase in the manufacturing cost of the handset. In addition, there is a requirement in the W-CDIvl AA standard that a handset should be able to handle multi-path signals, as described above, in connection with multi-path CPICH signals corresponding to different cells of the cellular network, and that multi-path measurements should be made in relation to a predetermined number of cells should within a predetermined time, each cell being identified by its own scrambling code and channelisation code. Thus, if a multi-path searcher is used to make successive multi-path measurements in relation to multiple cells, the integration time for each is limited. Alternatively, if multiple multi-path searchers are provided to handle the multiple cells in parallel, then the manufacturing cost and power consumption is increased. An object of the invention is to provide multi-path searching in such a manner as to mitigate the above problems. According to the invention, a multi-path searcher is provided which carries out a correlation process over a predetermined integration period in relation to a first pilot signal received in connection with the first cell of a cellular network to identify the position of multi-paths in the signal, characterised in that information of said multi-path positions over a first predetermined integration period is stored as first candidate multi-path positions and compared with second candidate multi-path positions derived from multiple correlation measurements made subsequently by the multi-path searcher over a second predetermined integration period in relation to the first pilot signal, so as to confirm or reject candidate multi-path positions and define modified candidate multi-path positions. Any uncertainty in candidate multi-path positions as measured in the first predetermined integration period is resolved by the candidate multi-path positions as measured in the second and subsequent predetermined integration periods, thus shorter integration periods can be used to reduce hardware size and cost, while an insufficiently low level of uncertainty in the measurement of candidate multi-path positions can still be accomodated. By spacing said successive predetermined integration periods apart, multiple sets of integration periods can be interleaved and the same multi-path searcher can be used to determine the multi-path positions in relation to the pilot signal received in connection with each of different cells. Thus, the multi-path searcher carries out a first correlation process in relation to the pilot signal of each of different cells in succession to determine first candidate multi-paths for each, and then carries out a second correlation process in relation to each of the pilot signals again to determine second candidate multi-paths for each to confirm or reject the respective first candidate multi-paths and define modified candidate multi-path positions. Thus the multi-path searcher is able to meet the standard required in measuring the multi-path positions of a predetermined number of cells within a limited time whilst still controlling the size of the hardware used. The invention will now be described by way of example with reference to the accompanying drawings:- Figure1 is a schematic drawing of a multi-path searcher as used according to the invention; Figure 2 is a schematic drawing showing the time delayed outputs of multiple correlators in Figure 1; Figure 3 is a plot of the outputs of the correlators of Figure 1 in response to a typical CPICH signal, showing candidate multi-paths; and Figure 4 is a diagram showing the timing of successive candidate multi-path measurements for different cells. The multi-path searcher in Figure 1 comprises multiple correlators Co, C1, C2, C3.......CN which are all fed the same input signal generated by a cellular receiver RX. The input signal is fed to the correlators via a chain of delay elements D Which each introduce a delay A so that the input signal is delayed to each of successive correlators Co, C1, C2, C3.......CN by a progressively increasing interval ?, 2?, 3?.........N? as shown in Figure 2. In the first of multiple integration periods Tp1, each of the correlators processes the input signal using a scrambling sequence for the common pilot channel CPICH of a first cell CELL 1 so as to make multiple correlation measurements Mo, M1, M2, M3........Mn, which are analysed in a processor A as a time plot, shown in Figure 3, to determine multi-path positions in accordance with a reference L. These multi-path positions are stored in a corresponding first store P1. It will be appreciated that the correlation process in each correlator involves a de-scrambling, de-spreading and accumulation, of the bit streams representing the input signal to produce one of the probability measurements Mo, M1, M2, M3........Mn- The reference level L is set at a predetermined level corresponding to the expected threshold for the existence of a multi-path. As shown in the example of Figure 3, two significant peaks are detected, L1 above the level L and L2 just below the level L. Data of both of these peaks L1 and L2 are stored in the store P1 as candidate multi-path positions. As the correlation process continues, the correlators Co, C1, C2, C3........CN next make multiple correlation measurements over a second integration period TP2 in relation to the CPICH channel of a second cell CELL 2 to determine corresponding candidate multi-path positions which are stored in the store P2. The same correlation process then runs for each of successive integration periods TP3, TP4.........TPs in relation to the CPICH channel of 3rd, 4th.......Sth cells CELL 3, CELL 4........CELL S to determine corresponding candidate multi-path positions and to store these in respective stores P3, P4.............Ps. At this point, the multi-path detector has analysed the candidate multi-paths in S cells over a time period STP, assuming that the integration periods TP1, Tp2, Tp3, TP4...........Tps are all equal to TP. It will be appreciated that TP = Tint- + N?, where Tint is the period over which each correlator operates to generate a correlation measurement. Therefore, the period Tint, delay A and number of correlators N are all selected in relation to the number of cells S to ensure that the multi-paths are determined for the required number of cells S in a predetermined time STp. Having measured candidate multi-paths for each of the cells S in a first measurement cycle Tl, as shown in Figure 4, the correlators Co, C1, C2, C3........Cn then repeat the whole process in a second measurement cycle T2 to determine a second set of candidate multi-path positions for each cell which are also stored in the respective stores P1 to Ps holding the first candidate multi-path positions. The first and second set of candidate multi-path positions stored in each store P1 to Ps are compared with one another by the processor A to produce a modified set of candidate multi-path positions, some candidate positions being confirmed and others being rejected. This process of modification of candidate multi-path positions to produce a modified set of multi-path positions with a higher probability of correctness, continues in successive measurement cycles. In this way, any lower level of probability accepted for determining individual candidate multi-path positions, perhaps because of a shorter than optimum period Tint, is compensated for by subsequent repeat measurements. WE CLAIM:- 1. A method of multi-path searching in a cellular network in which a multi-path searcher is provided which carries out a correlation process over a predetermined integration period in relation to a first pilot signal received in connection with a first cell of the cellular network to identify the position of multi-paths in the signal, the multiple correlation measurements so generated being analysed in relation to the time delays to identify the multi-path positions, characterised in that information of said multi-path positions over a first predetermined integration period is stored as first candidate multi-path positions and compared with second candidate multi-path positions derived from multiple correlation measurements made subsequently by the multi-path searcher over a second predetermined integration period in relation to the first pilot signal, so as to confirm or reject candidate multi-path positions and define modified candidate multi-path positions and wherein the multi-path searcher carries out a correlation process in each of successive integration periods over a first cycle of integration periods and identifies first candidate multi-path positions during each integration period in relation to the pilot signal of a respective different cell, and in which the multi-path searcher repeats said correlation process in each of successive integration periods over a second cycle of integration periods to identify second candidate multi path positions during each in relation to the pilot signal of the same set of cells as during the first cycle of integration periods, corresponding first and second candidate multi-path positions relating to the same cell being compared to determine modified candidate multi-path positions for the training signal of each cell. 2. A multi-path searcher for multi-path searching in a cellular network by carrying out a correlation process over a predetermined integration period in relation to a first pilot signal received in connection with a first cell of the cellular network to identify the position of multi-paths in the signal, characterised in that storage means is provided to store information of said multi-path positions over a first predetermined integration period as first candidate multi-path positions and to store second candidate multi-path positions derived from multiple correlation measurements made subsequently by the multi-path searcher over a second predetermined integration period in relation to the first pilot signal, and comparison means to compare said first and second candidate multi-path positions so as to confirm or reject candidate multi-path positions and define modified candidate multi-path positions. 3 A mobile handset incorporating a multi-path searcher as claimed in claim 2 A method of multi-path searching in a cellular network in which a multi-path searcher is provided which carries out a correlation process over a predetermined integration period in relation to a first pilot signal received in connection with a first cell of the cellular network to identify the position of multi-paths in the signal and the multi-path searcher for multi-path searching in a cellular network by carrying out a correlation process over a predetermined integration period in relation to a first pilot signal received in connection with a first cell of the cellular network to identify the position of multi-paths in the signal. |
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01787-kolnp-2005-description complete.pdf
01787-kolnp-2005-international publication.pdf
1787-KOLNP-2005-(09-02-2012)-CORRESPONDENCE.pdf
1787-KOLNP-2005-ASSIGNMENT-1.1.pdf
1787-kolnp-2005-assignment.pdf
1787-KOLNP-2005-CORRESPONDENCE 1.1.pdf
1787-KOLNP-2005-CORRESPONDENCE-1.1.pdf
1787-KOLNP-2005-CORRESPONDENCE-1.2.pdf
1787-kolnp-2005-correspondence.pdf
1787-kolnp-2005-description (complete).pdf
1787-KOLNP-2005-EXAMINATION REPORT-1.1.pdf
1787-kolnp-2005-examination report.pdf
1787-KOLNP-2005-EXAMINATION REPORT1.1.pdf
1787-KOLNP-2005-FORM 18-1.2.pdf
1787-KOLNP-2005-FORM 26-1.2.pdf
1787-KOLNP-2005-FORM 3-1.2.pdf
1787-KOLNP-2005-FORM 5-1.2.pdf
1787-KOLNP-2005-FORM 6-1.2.pdf
1787-KOLNP-2005-GRANTED-ABSTRACT-1.1.pdf
1787-KOLNP-2005-GRANTED-CLAIMS-1.1.pdf
1787-KOLNP-2005-GRANTED-DESCRIPTION (COMPLETE)-1.1.pdf
1787-KOLNP-2005-GRANTED-DRAWINGS-1.1.pdf
1787-KOLNP-2005-GRANTED-FORM 1-1.2.pdf
1787-KOLNP-2005-GRANTED-FORM 2-1.1.pdf
1787-KOLNP-2005-GRANTED-LETTER PATENT-1.1.pdf
1787-KOLNP-2005-GRANTED-SPECIFICATION-1.1.pdf
1787-kolnp-2005-granted-translated copy of priority document.pdf
1787-KOLNP-2005-OTHERS-1.1.pdf
1787-KOLNP-2005-REPLY TO EXAMINATION REPORT-1.1.pdf
1787-KOLNP-2005-REPLY TO EXAMINATION REPORT.pdf
1787-kolnp-2005-specification.pdf
1787-kolnp-2005-translated copy of priority document.pdf
1787-KOLNP-2006-FORM 6-1.1.pdf
Patent Number | 235880 | |||||||||
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Indian Patent Application Number | 1787/KOLNP/2005 | |||||||||
PG Journal Number | 36/2009 | |||||||||
Publication Date | 04-Sep-2009 | |||||||||
Grant Date | 02-Sep-2009 | |||||||||
Date of Filing | 08-Sep-2005 | |||||||||
Name of Patentee | TTPCOM LIMITED | |||||||||
Applicant Address | MELBOURN SCIENCE PARK, CAMBRIDGE ROAD, MELBOURN, ROYSTON, HERTFORDSHIRE, SG8 6HQ | |||||||||
Inventors:
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PCT International Classification Number | H04B 1/707 | |||||||||
PCT International Application Number | PCT/GB2004/000995 | |||||||||
PCT International Filing date | 2004-03-08 | |||||||||
PCT Conventions:
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