Patent ID: 6714583
Filing Date: 2004-03-30
Classification: H04B,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 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 despreading means 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 noise sampler, coupled to said matched filter, for sampling a plurality of noise samples at any of before, after, and a combination of before and after each symbol sample; a low-pass filter, coupled to said noise sampler, for filtering the plurality of noise samples, to generate a noise estimate corresponding to a particular symbol sample in the plurality of symbol samples; a combiner circuit, coupled to said low-pass filter and to said symbol sampler, for subtracting the noise estimate from the particular symbol sample, thereby generating a comparison signal; a magnitude device, coupled to said combiner circuit, for determining a magnitude of the comparison signal; and a comparator, coupled to said magnitude device and having a threshold voltage applied to a threshold input, for comparing the magnitude of the comparison signal to the threshold voltage, thereby generating the erasure signal; and an erasure decoder, having an erasure input coupled to said comparator and a data input coupled to said symbol sampler, responsive to the erasure signal for erasure decoding the symbol sample.