Title of Invention  MULTIPATH SEARCHING 

Abstract  A method of multipath searching in a cellular network in which a multipath 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 multipaths in the signal and the multipath searcher for multipath 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 multipaths in the signal. 
Full Text  This invention relates to method of multipath searching in cellular network and multipath searcher for the same. A mobile handset has to be designed to accommodate multipath signals that may be present in the received signal, and for this purpose it incorporates a multipath searcher which identifies the strongest of the multipath 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 multipath 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 subset to use for decoding. The multipath 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 multipath 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 WCDIvl AA standard that a handset should be able to handle multipath signals, as described above, in connection with multipath CPICH signals corresponding to different cells of the cellular network, and that multipath 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 multipath searcher is used to make successive multipath measurements in relation to multiple cells, the integration time for each is limited. Alternatively, if multiple multipath 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 multipath searching in such a manner as to mitigate the above problems. According to the invention, a multipath 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 multipaths in the signal, characterised in that information of said multipath positions over a first predetermined integration period is stored as first candidate multipath positions and compared with second candidate multipath positions derived from multiple correlation measurements made subsequently by the multipath searcher over a second predetermined integration period in relation to the first pilot signal, so as to confirm or reject candidate multipath positions and define modified candidate multipath positions. Any uncertainty in candidate multipath positions as measured in the first predetermined integration period is resolved by the candidate multipath 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 multipath positions can still be accomodated. By spacing said successive predetermined integration periods apart, multiple sets of integration periods can be interleaved and the same multipath searcher can be used to determine the multipath positions in relation to the pilot signal received in connection with each of different cells. Thus, the multipath searcher carries out a first correlation process in relation to the pilot signal of each of different cells in succession to determine first candidate multipaths for each, and then carries out a second correlation process in relation to each of the pilot signals again to determine second candidate multipaths for each to confirm or reject the respective first candidate multipaths and define modified candidate multipath positions. Thus the multipath searcher is able to meet the standard required in measuring the multipath 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 multipath 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 multipaths; and Figure 4 is a diagram showing the timing of successive candidate multipath measurements for different cells. The multipath 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 multipath positions in accordance with a reference L. These multipath positions are stored in a corresponding first store P1. It will be appreciated that the correlation process in each correlator involves a descrambling, despreading 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 multipath. 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 multipath 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 multipath 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 multipath positions and to store these in respective stores P3, P4.............Ps. At this point, the multipath detector has analysed the candidate multipaths 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 multipaths are determined for the required number of cells S in a predetermined time STp. Having measured candidate multipaths 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 multipath positions for each cell which are also stored in the respective stores P1 to Ps holding the first candidate multipath positions. The first and second set of candidate multipath positions stored in each store P1 to Ps are compared with one another by the processor A to produce a modified set of candidate multipath positions, some candidate positions being confirmed and others being rejected. This process of modification of candidate multipath positions to produce a modified set of multipath 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 multipath positions, perhaps because of a shorter than optimum period Tint, is compensated for by subsequent repeat measurements. WE CLAIM: 1. A method of multipath searching in a cellular network in which a multipath 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 multipaths in the signal, the multiple correlation measurements so generated being analysed in relation to the time delays to identify the multipath positions, characterised in that information of said multipath positions over a first predetermined integration period is stored as first candidate multipath positions and compared with second candidate multipath positions derived from multiple correlation measurements made subsequently by the multipath searcher over a second predetermined integration period in relation to the first pilot signal, so as to confirm or reject candidate multipath positions and define modified candidate multipath positions and wherein the multipath searcher carries out a correlation process in each of successive integration periods over a first cycle of integration periods and identifies first candidate multipath positions during each integration period in relation to the pilot signal of a respective different cell, and in which the multipath 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 multipath positions relating to the same cell being compared to determine modified candidate multipath positions for the training signal of each cell. 2. A multipath searcher for multipath 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 multipaths in the signal, characterised in that storage means is provided to store information of said multipath positions over a first predetermined integration period as first candidate multipath positions and to store second candidate multipath positions derived from multiple correlation measurements made subsequently by the multipath searcher over a second predetermined integration period in relation to the first pilot signal, and comparison means to compare said first and second candidate multipath positions so as to confirm or reject candidate multipath positions and define modified candidate multipath positions. 3 A mobile handset incorporating a multipath searcher as claimed in claim 2 A method of multipath searching in a cellular network in which a multipath 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 multipaths in the signal and the multipath searcher for multipath 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 multipaths in the signal. 

01787kolnp2005description complete.pdf
01787kolnp2005international publication.pdf
1787KOLNP2005(09022012)CORRESPONDENCE.pdf
1787KOLNP2005ASSIGNMENT1.1.pdf
1787kolnp2005assignment.pdf
1787KOLNP2005CORRESPONDENCE 1.1.pdf
1787KOLNP2005CORRESPONDENCE1.1.pdf
1787KOLNP2005CORRESPONDENCE1.2.pdf
1787kolnp2005correspondence.pdf
1787kolnp2005description (complete).pdf
1787KOLNP2005EXAMINATION REPORT1.1.pdf
1787kolnp2005examination report.pdf
1787KOLNP2005EXAMINATION REPORT1.1.pdf
1787KOLNP2005FORM 181.2.pdf
1787KOLNP2005FORM 261.2.pdf
1787KOLNP2005FORM 31.2.pdf
1787KOLNP2005FORM 51.2.pdf
1787KOLNP2005FORM 61.2.pdf
1787KOLNP2005GRANTEDABSTRACT1.1.pdf
1787KOLNP2005GRANTEDCLAIMS1.1.pdf
1787KOLNP2005GRANTEDDESCRIPTION (COMPLETE)1.1.pdf
1787KOLNP2005GRANTEDDRAWINGS1.1.pdf
1787KOLNP2005GRANTEDFORM 11.2.pdf
1787KOLNP2005GRANTEDFORM 21.1.pdf
1787KOLNP2005GRANTEDLETTER PATENT1.1.pdf
1787KOLNP2005GRANTEDSPECIFICATION1.1.pdf
1787kolnp2005grantedtranslated copy of priority document.pdf
1787KOLNP2005OTHERS1.1.pdf
1787KOLNP2005REPLY TO EXAMINATION REPORT1.1.pdf
1787KOLNP2005REPLY TO EXAMINATION REPORT.pdf
1787kolnp2005specification.pdf
1787kolnp2005translated copy of priority document.pdf
1787KOLNP2006FORM 61.1.pdf
Patent Number  235880  

Indian Patent Application Number  1787/KOLNP/2005  
PG Journal Number  36/2009  
Publication Date  04Sep2009  
Grant Date  02Sep2009  
Date of Filing  08Sep2005  
Name of Patentee  TTPCOM LIMITED  
Applicant Address  MELBOURN SCIENCE PARK, CAMBRIDGE ROAD, MELBOURN, ROYSTON, HERTFORDSHIRE, SG8 6HQ  
Inventors:


PCT International Classification Number  H04B 1/707  
PCT International Application Number  PCT/GB2004/000995  
PCT International Filing date  20040308  
PCT Conventions:
