US 8,787,427 B2 · Chip-level processing for joint demodulation in CDMA receivers

Abstract

A CDMA multi-code joint demodulation solution in which impairment suppression and channel matching operations are performed prior to despreading. Embodiments include a linear front end that performs chip-level suppression of signal components that are not included in a subsequent joint demodulation process. The pre-processing stage also carries out metric preparation and provides a vector decision statistic that is processed by a joint demodulation stage to extract per-code soft values for the symbols of interest in the received signal. Both code-specific and code-averaged versions of the linear processing are disclosed, as are several front-end configurations with equivalent performance, but different complexity trade-offs. These new approaches use a block formulation, requiring a set of input chip samples as an input, and perform all operations as matrix-vector multiplications, which is an approach amenable to efficient DSP or hardware implementation.

Claims20

Dependent claims

A method for processing a received spread spectrum signal containing two or more simultaneously transmitted symbols of interest with known spreading codes and one or more interfering signals with known spreading codes, wherein the known spreading codes for the simultaneously transmitted symbols of interest differ from one another and from the known spreading code or codes for the interfering signals, said method comprising:

for a given despread symbol interval, forming a sample vector from samples of the received spread spectrum signal, wherein said samples span the despread symbol interval;
using one or more matrix multiplication operations, performing a linear transformation of the sample vector to an interference-reduced decision statistic vector for the given despread symbol interval, based on covariance statistics for the received signal, wherein said linear transformation depends on the known spreading codes and wherein the interference-reduced decision statistic vector comprises a single complex value for at least each of the symbols of interest;
and
estimating a symbol value for at least one of the symbols of interest from the interference-reduced decision statistic vector, for the given despread symbol interval, using a non-linear detection process that accounts for code-specific leakage between the known spreading codes for the symbols of interest.

1 more element

A receiver circuit adapted to process a received spread spectrum signal containing two or more simultaneously transmitted symbols of interest with known spreading codes and one or more interfering signals with known spreading codes, wherein the known spreading codes for the simultaneously transmitted symbols of interest differ from one another and from the known spreading code or codes for the interfering signals, the receiver circuit comprising:

a front-end radio frequency circuit configured to mix the received spread spectrum signal to baseband and to digitize the received spread spectrum signal;
and
a receiver processing circuit configured to:
form a sample vector for a given despread symbol interval, from samples of the received spread spectrum signal, wherein said samples span the despread symbol interval;
perform a linear transformation of the sample vector to an interference-reduced decision statistic vector for the given despread symbol interval, using one or more matrix multiplication operations, based on covariance statistics for the received signal, wherein said linear transformation depends on the known spreading codes and wherein the interference-reduced decision statistic vector comprises a single complex value for at least each of the symbols of interest;
and
estimate a symbol value for at least one of the symbols of interest from the interference-reduced decision statistic vector, for the given despread symbol interval, using a non-linear detection process that accounts for code-specific leakage between the known spreading codes for the symbols of interest.

4 more elements

Dependencies are inferred from the claim text.

Chip-level processing for joint demodulation in CDMA receivers

Life of this patent

Chip-level processing for joint demodulation in CDMA receivers

Life of this patent

Abstract

Claims20