Title of Invention

MULTI-PATH SEARCHING

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.

Documents:

01787-kolnp-2005-claims.pdf

01787-kolnp-2005-description complete.pdf

01787-kolnp-2005-drawings.pdf

01787-kolnp-2005-form 1.pdf

01787-kolnp-2005-form 2.pdf

01787-kolnp-2005-form 3.pdf

01787-kolnp-2005-form 5.pdf

01787-kolnp-2005-international publication.pdf

1787-KOLNP-2005-(09-02-2012)-CORRESPONDENCE.pdf

1787-kolnp-2005-abstract.pdf

1787-KOLNP-2005-ASSIGNMENT-1.1.pdf

1787-kolnp-2005-assignment.pdf

1787-kolnp-2005-claims.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-drawings.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 1.pdf

1787-KOLNP-2005-FORM 18-1.2.pdf

1787-kolnp-2005-form 18.pdf

1787-kolnp-2005-form 2.pdf

1787-KOLNP-2005-FORM 26-1.2.pdf

1787-KOLNP-2005-FORM 26.pdf

1787-KOLNP-2005-FORM 27.pdf

1787-KOLNP-2005-FORM 3-1.2.pdf

1787-KOLNP-2005-FORM 3.1.pdf

1787-kolnp-2005-form 3.pdf

1787-KOLNP-2005-FORM 5-1.2.pdf

1787-KOLNP-2005-FORM 5.pdf

1787-KOLNP-2005-FORM 6-1.2.pdf

1787-KOLNP-2005-FORM 6.pdf

1787-KOLNP-2005-GPA.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-OTHERS.pdf

1787-KOLNP-2005-PA.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

abstract-01787-kolnp-2005.jpg


Patent Number 235880
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:
# Inventor's Name Inventor's Address
1 FRANCESC BOIXADERA ESPAX 61 COLLEGE FIELDS, WOODHEAD DRIVE, CAMBRIDGE
2 FRANCESC BOIXADERA ESPAX 61 COLLEGE FIELDS, WOODHEAD DRIVE, CAMBRIDGE
PCT International Classification Number H04B 1/707
PCT International Application Number PCT/GB2004/000995
PCT International Filing date 2004-03-08
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 GB 0305561.3 2003-03-11 U.K.