Matra Nortel Communications

Matra Communication

Fabrice Belveze

Philippe Mege

Florence Madeleine Chancel

Xavier Lasne

Albert Roseiro

A transmitter outputs a radio signal formed from a first baseband signal incorporating a synchronization signal. The recipient obtains a second baseband signal from the received radio signal, detects the synchronization signal in a portion of the second baseband signal in order to compute synchronization parameters and/or parameters for estimating a radio transmission channel, and uses the computed parameters to demodulate another portion of the second baseband signal and extract the transmitted information from it. The synchronization signal contains a synchronization pattern selected by the transmitter on the basis of signalling information to be supplied to the second station. The receiver searches several patterns in the second baseband signal in order to obtain the signalling information depending on the detected pattern.

Signalling method in a radio communication system, and transmitters, receivers and repeaters for implementing the method

The detection of symbols of a sequence on the basis of an observation signal is performed in accordance with a soft output Viterbi algorithm using a trellis. In order to assign a likelihood to a discrete estimation of a symbol, the difference between the metrics of the optimal path determined in accordance with the Viterbi algorithm and the metrics of a competitor path, which is optimal among all the paths leading to a different decision for the symbol in question is calculated, the metrics being considered on the whole length of the trellis.

Method for detecting a discrete symbol sequence from an observation signal, and viterbi processor implementing such method

A receiving device performs N separate demodulations (N.gtoreq.2) each supplying respective estimates of successive binary symbols resulting from differential coding of a sequence of bits sent by a transmitting device, the differential coding being of the form a.sub.k c.sub.k .sym.a.sub.f(k) where a.sub.k and c.sub.k designate the binary symbol at position k and the bit at position k, f(k) designates an integer equal to k-1 at most and .sym. designates the exclusive-OR operation. Each estimate of a binary symbol at position k is a real number s.sub.k.sup.(i) (1=i=N) the sign of which represents the most probable value of the symbol and the modulus of which measures the likelihood of the most probable value. The value of a bit at position k of the sequence is estimated on the basis of the number: ##EQU1##

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Maurepas, France

Fabrice Belveze