Patent ID: 6359925
Filing Date: 2002-03-19
Classification: H04L

Abstract:
An improvement to a spread-spectrum receiver at a base station in a direct-sequence code-division-multiple-access (DS-CDMA) system, having a plurality of spread-spectrum signals modulating differentially-encoded symbols, with each spread-spectrum signal in the plurality of spread-spectrum signals having a chip-sequence signal lasting a symbol time TS, and with each chip-sequence signal different from other chip-sequence signals used by other spread-spectrum signals in the plurality of spread-spectrum signals, with the spread-spectrum receiver including a matched filter having an impulse response matched to a desired chip-sequence signal in the plurality of chip-sequence signals, for detecting a desired spread-spectrum signal in the plurality of spread-spectrum signals arriving at the spread-spectrum receiver, the improvement comprising:a symbol sampler, coupled to said matched filter, for sampling at a plurality of symbol times nTS, where n is an index to each symbol time, a plurality of symbol samples; a relative-signal-level decoder, coupled to said symbol sampler, for relative-signal-level decoding the plurality of symbol samples, thereby generating a plurality of decoded-symbol samples; a noise sampler, coupled to said matched filter, for sampling at any of before, after, or a combination of before and after each decoded-symbol sample, at a plurality of chip times kTC, where k is an index of each chip time Tc, but not at the plurality of symbol times nTS, a plurality of noise samples; an estimator, coupled to said noise sampler, for processing the plurality of noise samples to generate a noise estimate; an erasure detector, coupled to said estimator and to said symbol sampler, for detecting from a particular symbol sample corresponding in time to the particular decoded-symbol sample and the noise estimate, an erasure condition, thereby generating an erasure signal; and an erasure decoder, having an erasure input coupled to said erasure detector and a data input coupled to said relative-signal-level decoder, responsive to the erasure signal, for erasure decoding the data input.