Method and decoder for despreading data signals spread using walsh sequences
OwnerReinhart Rudershauseninventor
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Abstract
According to the invention, a data stream with continuous, periodic transmitted, spread data signals of N chips each is split into two data streams of N chips each, which are shifted by N chips; for each of these data streams the correlation functions are calculated within every chip clock time and, in relation to their maxima, evaluated in order to separate user signals from extraneous signals and disturbing signals.
Claims20
A method for de-spreading a data signal (DS) that have been spread using a Walsh sequence (W(n, m)) of the chip lengths N, which are received as the first data stream in a periodic sequence, wherein the method comprises:
- splitting the first data stream into at least a second and a third non-periodic data stream, each of which comprises alternating N successive chips of the first data stream arriving with a chip cycle;
- with each chip cycle, computing a correlation of the lengths N for each chip sequence in the second and in the third data streams with stored sequences;
- determining desired signals using the second and third data streams by calculating the respective maximums of the computed correlations within 2N−1 chip cycles, and evaluating the symmetry of the calculated maximums with a threshold value;
- and
- joining the determined desired signals in an alternating manner, in each case following N chip cycles, for generating the de-spread first data stream.
A decoder for de-spreading a data signal (DS) that have been spread using a Walsh sequence (W(n, m)) of the chip lengths N, which are received as a first data stream in a periodic sequence, wherein the decoder comprises:
- means for splitting the first data stream into at least a second and a third non-periodic data stream, each of which records alternating N successive chips of the first data stream arriving with a chip cycle;
- means for computing the correlation of the lengths N for each chip sequence in the second and third data streams with stored sequences, at each chip cycle;
- means for determining desired signals using the second and third data streams by calculating the respective maximums of the computed correlations within 2N−1 chip cycles, and evaluating the symmetry of the calculated maximums with a threshold value;
- and
- means for joining the determined desired signals in an alternating manner, in each case following N chip cycles, for generating the de-spread first data stream.
Dependencies are inferred from the claim text.