SPREAD-SPECTRUM, RELATIVE-SIGNAL-LEVEL DATA DETECTION USING MATCHED-FILTER OBTAINED SIDE INFORMATION

• US 20030161388A1
• Filed: 01/07/2003
• Published: 08/28/2003
• Est. Priority Date: 03/09/1999
• Status: Abandoned Application

• Current Assignee: Linex Technologies, Inc.
• Original Assignee: Linex Technologies, Inc.
• Inventors: Schilling, Donald L.
• Application Number:
  US10/337,962
• Publication Number:
  US 20030161388A1
• Time in Patent Office: Days
• US Class Current: 375/147
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/0047 Decoding adapted to other signal detection operation in conjunction with sequence estimation or equalization H04L25/03286

Abstract

An improvement to a spread-spectrum base station receiver having a matched filter. A symbol sampler samples at the symbol time T_S, a plurality of symbol samples from the matched filter. A relative-signal-level decoder decodes the plurality of received-symbol samples, thereby generating a plurality of decoded-symbol samples. A noise sampler samples at a plurality of chip times kT_C, but not at the symbol time T_S, a plurality of noise samples from the matched filter, before, after, or a combination of before and after, a symbol sample. An estimator processes the plurality of noise samples. The erasure detector detects for each decoded-symbol sample from the plurality of decoded-symbol samples and from the plurality of noise samples, an erasure condition for the corresponding decoded-symbol sample, and thereby generates an erasure signal. An erasure decoder erasure decodes the input data using the erasure signals from the erasure detector.

Claims

1. 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 T_S, 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 nT_S, 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 kT_C, but not at the plurality of symbol times nT_S, 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.

2. An improvement to a spread-spectrum receiver in a direct-sequence code-division-multiple-access (DS-CDMA) system having a plurality of spread-spectrum signals modulating differentially-encoded data, with each spread-spectrum signal in the plurality of spread-spectrum signals having a chip-sequence signal lasting a symbol time T_S, 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:

sampler means, coupled to said matched filter, for sampling at a plurality of symbol times nT_S, a plurality of symbol samples;

relative-signal-level means, coupled to said sampler means, for relative-signal-level decoding the plurality of symbol samples, thereby generating a plurality of decoded-symbol samples;

said sampler means for sampling at any of before, after, or a combination of before and after each symbol sample corresponding to the particular decoded-symbol sample from a plurality of decoded-symbol samples, at a plurality of chip times kT_C, but not at the plurality of symbol times nT_S, a plurality of noise samples;

estimate means, coupled to said sampler means, for processing the plurality of noise samples to generate a corresponding noise estimate for each decoded-symbol sample;

erasure-detection means, coupled to said estimate means, for detecting from the corresponding noise estimate and a symbol sample corresponding to each decoded-symbol sample from the plurality of decoded-symbol samples, an erasure condition, thereby generating a corresponding erasure signal; and

an erasure decoder, having an erasure input coupled to said erasure-detection means and a data input coupled to said relative-signal-level means, responsive to the erasure signal, for erasure decoding the plurality of decoded-symbol samples.

3. The improvement as set forth in claim 2 with said sampler means including:

a noise sampler, coupled to said matched filter, for sampling at the plurality of chip times kT_C, but not at the plurality of symbol times nT_C, the plurality of noise samples; and

a symbol sampler, coupled to said matched filter, for sampling at the plurality of symbol times nT_S, the plurality of symbol sample.

4. The improvement as set forth in claim 2, with said estimate means including:

a delay device, coupled to said sampler means, for delaying a symbol sample one symbol time T_S, thereby generating a delayed-symbol sample;

a combiner, coupled to said delay device and to said symbol sampler, for subtracting the delayed-symbol sample from the symbol sample, thereby generating a relative-signal-level sample; and

a comparator, coupled to said combiner and having a threshold input with a threshold, for comparing the relative-signal-level sample to the threshold, thereby generating a decoded-symbol sample of the plurality of decoded-symbol samples.

5. The improvement as set forth in claim 3, with said estimate means including:

a delay device, coupled to said symbol sampler, for delaying a symbol sample one symbol time T_S, thereby generating a delayed-symbol sample;

a combiner, coupled to said delay device and to said symbol sampler, for subtracting the delayed-symbol sample from the symbol sample, thereby generating a relative-signal-level sample; and

a comparator, coupled to said combiner and having a threshold input with a threshold, for comparing the relative-signal-level sample to the threshold, thereby generating a decoded-symbol sample of the plurality of decoded-symbol samples.

6. The improvement as set forth in claim 2, 3 or 4, with said estimate means including a register for storing the plurality of noise samples.

7. A method for improving a spread-spectrum receiver in a direct-sequence code-division-multiple-access (DS-CDMA) system having a plurality of spread-spectrum signals modulating differentially-encoded data, with each spread-spectrum signal in the plurality of spread-spectrum signals having relative-signal-level encoded symbol samples and a chip-sequence signal lasting a symbol time T_S, 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 the steps of:

sampling, at a plurality of symbol times nT_S, where n is an index to each symbol time, a plurality of symbol samples;

relative-signal-level decoding the plurality of symbol samples, thereby generating a plurality of decoded-symbol samples;

sampling at any of before, after, or a combination of before and after each symbol sample, at a plurality of chip times kT_C, but not at the plurality of symbol times nT_S, a plurality of noise samples;

processing the plurality of noise samples to generate a corresponding noise estimate for each decoded-symbol sample;

detecting from the corresponding noise estimate and symbol sample corresponding to each decoded-symbol sample from the plurality of decoded-symbol samples, an erasure condition, thereby generating a corresponding erasure signal; and

erasure decoding, in response to the erasure signals, the input-data symbols.