US 5,659,573 A · Method and apparatus for coherent reception in a spread-spectrum receiver

Abstract

A method and apparatus is provided for facilitating coherent communication reception. A received reference symbol coded spread spectrum communication signal is despread with a spreading code to derive a stream of reference samples and a stream of data samples. The channel response is estimated by utilizing the stream of reference samples. An offset frequency detector determines an offset to be applied to the received signal via a frequency locked loop, while a timing control compensates for slow timing drift and fast fading based on power estimates derived from the stream of reference samples and/or the stream of data samples. A slot detector controls gates which optimize the timing control and frequency offset detector outputs from the various timing branches. Thus an improved detection of estimated data symbols from the stream of received data samples is provided.

Claims16

Dependent claims

A coherent spread spectrum receiver, including a sampler for digitizing a received spread spectrum signal and a despreader following the sampler for despreading the received digitized spread spectrum signal into a data signal, comprising:

(a) extracting means coupled to the despreader for extracting reference sample information from the data signal;
(b) timing control means coupled to the extracting means for adjusting the timing of the received spread spectrum signal based on at least one of the data signal and the reference sample information;
and
(c) frequency offset means coupled to the extracting means for adjusting one of the group consisting of the phase and frequency of the received spread spectrum signal.

1 more element

A synchronization device for use in a coherent direct sequence spread-spectrum receiver, comprising an extractor operable for extracting timing information from a received reference symbol coded spread-spectrum signal, wherein the extractor comprises:

(a) a first despreading means for despreading an advanced replica of the received reference symbol coded spread-spectrum signal with a despreading signal to form an early despread signal;
(b) a second despreading means for despreading a retarded replica of the received reference symbol coded spread-spectrum signal with a despreading signal to form a late despread signal;
(c) reference sample extracting means for extracting reference samples from the early and the late despread signal;
(d) correlating means for correlating the reference samples from the early despread signal with a known reference sequence to generate an unbiased early power estimate and for correlating the reference samples from the late despread signal with the known reference sequence to generate an unbiased late power estimate;
(e) difference means for calculating the power difference between the unbiased early power estimate and the unbiased late power estimate;
and
(f) delay lock loop means for adjusting sampling time of a demodulator based upon the calculated power difference.

4 more elements

A method for coherent reception of spread spectrum communications in a receiver, comprising the steps of:

(a) digitizing a received spread spectrum signal in a sampler and despreading the received spread spectrum signal in a despreader coupled to the sampler into a data signal;
(b) extracting reference sample information from the data signal in an extractor;
(c) adjusting the timing of the received spread spectrum signal based on at least one of the data signal and the reference sample information;
and
(d) adjusting one of the group consisting of the phase and frequency of the received spread spectrum signal based on at least one of the data signal and the reference sample information.

2 more elements

Dependencies are inferred from the claim text.

Method and apparatus for coherent reception in a spread-spectrum receiver

Life of this patent

Method and apparatus for coherent reception in a spread-spectrum receiver

Life of this patent

Abstract

Claims16