Apparatus and methods for implementing a split equalizer filter for sparse channels
First Claim
1. A signal processing component for use in a mobile terminal operable in a wireless telecommunications system, the signal processing component for performing channel equalization operations, the channel equalization operations comprising:
- estimating an impulse response-delay profile of a channel using a known signal, the channel being a direct sequence spread spectrum communications channel;
determining if the impulse response-delay profile is indicative of a sparse channel;
if the channel impulse response-delay profile is indicative of a sparse channel, selecting a first channel impulse response cluster using a pre-determined selection criterion, wherein the first channel impulse response cluster is separated from other channel impulse response clusters by a delay difference indicative of the sparse nature of the channel;
aligning a first filter window with the first channel impulse response cluster;
calculating channel equalization coefficients for the first filter window; and
using the channel equalization coefficients to perform channel equalization on signals received by the mobile terminal.
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Accused Products
Abstract
The invention concerns methods and apparatus for performing channel equalization in a direct-sequence spread spectrum communications system. The methods and apparatus of the present invention are particularly applicable in situations where communication occurs over a channel experiencing multipath interference associated with paths having significantly different lengths. The impulse response-delay profile of such a channel is typically sparse, that is, dominated by a relatively few and widely spaced taps or clusters of closely spaced taps. In one aspect, equalization filter coefficients are calculated based on a channel estimate derived from a single cluster of closely-spaced channel taps collectively having the greatest percentage of energy as indicated by the impulse response-delay profile. In another aspect, equalization filter coefficients are calculated for each of two clusters of closely-spaced channel taps, where the two clusters of closely-spaced channel taps are separated by a delay spread indicative of a sparse channel. In a further aspect where channel equalization coefficients are calculated for each of two clusters of closely-spaced channel taps, the equalization coefficients are jointly optimized during the calculation process.
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Citations
25 Claims
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1. A signal processing component for use in a mobile terminal operable in a wireless telecommunications system, the signal processing component for performing channel equalization operations, the channel equalization operations comprising:
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estimating an impulse response-delay profile of a channel using a known signal, the channel being a direct sequence spread spectrum communications channel;
determining if the impulse response-delay profile is indicative of a sparse channel;
if the channel impulse response-delay profile is indicative of a sparse channel, selecting a first channel impulse response cluster using a pre-determined selection criterion, wherein the first channel impulse response cluster is separated from other channel impulse response clusters by a delay difference indicative of the sparse nature of the channel;
aligning a first filter window with the first channel impulse response cluster;
calculating channel equalization coefficients for the first filter window; and
using the channel equalization coefficients to perform channel equalization on signals received by the mobile terminal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A mobile terminal for use in a wireless communication network, the mobile terminal comprising:
a wireless section comprising a digital signal processor;
a signal processing component for performing channel equalization operations;
a wireless transceiver; and
an antenna, wherein the signal processing component performs the following channel equalization operations;
estimating an impulse response-delay profile of a channel using a known signal, the channel being a direct sequence spread spectrum communications channel;
determining if the impulse response-delay profile is indicative of a sparse channel;
if the channel impulse response-delay profile is indicative of a sparse channel, selecting at least a first channel impulse response cluster and a second channel impulse response cluster using a pre-determined selection criterion, wherein the first channel impulse response cluster and second channel impulse response clusters are separated by a delay difference indicative of the sparse nature of the channel;
aligning a first filter window with the first channel impulse response cluster and a second filter window with the second impulse response cluster;
calculating channel equalization coefficients for the first and second filter window; and
using the channel equalization coefficients calculated for the first and second filter windows to perform channel equalization on signals received by the mobile terminal. - View Dependent Claims (19, 20, 21, 22, 23)
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24. A method for use in a mobile terminal for performing channel equalization operations, the method comprising:
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estimating an impulse response-delay profile of a channel using a known signal, the channel being a direct sequence spread spectrum communications channel;
determining if the impulse response-delay profile is indicative of a sparse channel;
if the channel impulse response-delay profile is indicative of a sparse channel, selecting at least a first channel impulse response cluster and a second channel impulse response cluster using a pre-determined selection criterion, wherein the first channel impulse response cluster and second channel impulse response clusters are separated by a delay difference indicative of the sparse nature of the channel;
aligning a first filter window with the first channel impulse response cluster and a second filter window with the second impulse response cluster;
calculating channel equalization coefficients for the first and second filter window; and
using the channel equalization coefficients calculated for the first and second filter windows to perform channel equalization on signals received by the mobile terminal.
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25. A mobile terminal for use in a wireless communication network, the mobile terminal comprising:
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memory means for storing an operating program for controlling the mobile terminal, where the operating program further comprises a computer program component for controlling operation of the mobile terminal;
wireless section means comprising digital signal processing means;
signal processing component means;
wireless transceiver means and an antenna means for performing wireless communication operations;
processing means coupled to the memory means and wireless section means for executing the operating program, wherein the signal processing component performs the following channel equalization operations;
estimating an impulse response-delay profile of a channel using a known signal, the channel being a direct sequence spread spectrum communications channel;
determining if the impulse response-delay profile is indicative of a sparse channel;
if the channel impulse response-delay profile is indicative of a sparse channel, selecting at least a first channel impulse response cluster and a second channel impulse response cluster using a pre-determined selection criterion, wherein the first channel impulse response cluster and second channel impulse response clusters are separated by a delay difference indicative of the sparse nature of the channel;
aligning a first filter window with the first channel impulse response cluster and a second filter window with the second impulse response cluster;
calculating channel equalization coefficients for the first and second filter window; and
using the channel equalization coefficients calculated for the first and second filter windows to perform channel equalization on signals received by the mobile terminal.
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Specification