A method of synchronising a communication signal entering into a receiver. Each frame of the signal includes a learning symbol formed of N repetitions of a learning sequence. The method includes the determination of a total correlation signal by correlating the input signal with a correlation symbol formed of N repetitions of a correlation sequence corresponding to all or part of the learning sequence and duration t.sub.sc, and the determination of a partial correlation signal by correlating the input signal with the correlation sequence. A peak of the total correlation signal is identified at an instant t.sub.pct. At least one threshold is defined from the power of the peak of the total correlation signal, and the power of the partial correlation signal is compared here to the instants t.sub.pctk*t.sub.sc, with k a whole number between 0 and N1.

A method between a geolocation receiver and an identified transmitting satellite, the receiver being able to receive a composite radio signal including a plurality of navigation signals each transmitted by a transmitting satellite that is part of a satellite constellation, a method for validating the synchronization between a geolocation receiver and a transmitting satellite during a phase for acquiring an augmentation signal including geolocation correction and integrity data; the methods include, for each identified transmitting satellite, extracting received ephemeris words or received words of any type of the received signal associated with the identified satellite as it is received, and comparing at least one received word with at least one word of the same rank or stored for the identified satellite and/or for at least one other satellite; the validation or non-validation of the synchronization with the identified transmitting satellite depends on a predetermined false alarm probability and/or non-detection probability.

Time-offset, time-overlapping signals are received. The signals each include a pilot code, and at least some of the signals each include a user code occupying a time slot time-synchronized to a respective pilot code. Time-offset cross-correlation peaks for respective ones of the pilot codes are generated, each cross-correlation peak indicating a respective one of the time slots. For each time slot a respective projection vector including user code projections each indicative of whether a respective user code of known user codes is present in the time slot is generated. Particular ones of the projection vectors are selectively combined into an aggregate projection vector of aggregate user code projections, such that the aggregate projection vector has a signal-to-noise ratio (SNR) greater than the projection vectors individually. The user code is selected from among the known user codes based on the aggregate user code projections of the aggregate projection vector.

A method of synchronising a communication signal entering into a receiver. Each frame of the signal includes a learning symbol formed of N repetitions of a learning sequence. The method includes the determination of a total correlation signal by correlating the input signal with a correlation symbol formed of N repetitions of a correlation sequence corresponding to all or part of the learning sequence and duration t.sub.sc, and the determination of a partial correlation signal by correlating the input signal with the correlation sequence. A peak of the total correlation signal is identified at an instant t.sub.pct. At least one threshold is defined from the power of the peak of the total correlation signal, and the power of the partial correlation signal is compared here to the instants t.sub.pctk*t.sub.sc, with k a whole number between 0 and N1.

Embodiments provide a receiver having a receiving unit and a synchronization unit. The receiving unit is configured to receive a data packet having a pilot sequence. The synchronization unit is configured to separately correlate the pilot sequence with at least two partial reference sequences corresponding to a reference sequence for the pilot sequence of the data packet, in order to obtain a partial correlation result for each of the at least two partial reference sequences, wherein the synchronization unit is configured to non-coherently add the partial correlation results in order to obtain a coarse correlation result for the data packet.

Systems and methods for improving correlation. In at least one system and method, a signal is received and divided into a plurality of slices. Each of the slices is divided into a plurality of sub-slices. A plurality of chips of a PN code are generated, and sub-slice correlation results are generated in parallel. Summation of the sub-slice correlation results generates a slice correlation results, and the accumulated slice correlation results provide a correlation result.

A digital radio receiver (7) is arranged to receive and process data frames, each data frame comprising (i) a plurality of identical synchronization sequences; (ii) identification data different from the synchronization sequences; and (iii) convolution-encoded message data. An initial-synchronization section of the receiver (7) uses the plurality of synchronization sequences in a received data frame to perform a frequency-synchronization or symbol-timing-synchronization operation. A frame-synchronization section determines frame-synchronization information by correlating at least a part of the received identification data against reference identification data stored in a memory. A convolution-decoding section uses the frame-synchronization information to decode the message data.

Circuits and methods concerning signal detection are disclosed. In some example embodiments, an apparatus is configured to detect presence of a spreading sequence in a sample data sequence. Phase differences between samples in a sample sequence are determined. Presence of a spreading sequence in the sample sequence is detected by evaluating correlation of reference sub-sequences, of a reference spreading sequence, to the phase differences between samples in a sample sequence. Each of the reference sub-sequences includes fewer chips than the spreading sequence to be detected.

Combinations of correlation results are used to achieve detection of multiple coded signals at a receiver in a wireless communications system. The code applied to signals includes a lower rate code and a higher rate code. The lower rate code is a nested or tiered code such that it comprises at least two code sequences of the higher rate code. The received coded signal is correlated with the higher rate code using a single higher rate correlator to provide a higher rate code correlation result. The higher rate code correlation results are fed to two or more lower rate code correlators that combine multiple higher rate code-correlation results, each using a different lower rate code, to provide corresponding lower rate code correlation results. The presence of at least one coded signal or mutually exclusive coded signals can be determined from the lower rate code correlation results.

Correlation circuitry includes selection circuitry for selecting a sequence of symbol subsets comprising proper subsets of a candidate sequence of symbols and corresponding proper subsets of a target sequence of symbols. Correlation value determining circuitry determines partial correlation values for these proper subsets which are then combined by correlation value combining circuitry to generate a current combined correlation value. Early termination circuitry compares the current combined correlation value with an early termination condition represented by a threshold value to determine whether or not early termination of the correlation determination may be performed. Early termination may be performed when the combined correlation value indicates a sufficient degree of confidence in the partial result determined such that continuing with determination of the full correlation is not justified.