SYNCHRONISATION CODEWORD FOR INTERFERENCE REDUCTION IN A CDMA SYSTEM

摘要

The CDMA communication system according to the invention comprises at least one primary station (2) and a plurality of secondary stations (4). The primary station (2) and the secondary stations (4) can exchange CDMA signals (18) via a communication medium (6). The secondary stations (4) each comprise a modulator (10) for modulating data signals (16) with code words (14) in order to obtain the CDMA signals (18). A modulator (10) of a secondary station (4) initially modulates its data signal (16) with an initial code word until that secondary station (4) is synchronised with the primary station (2). From that moment on the data signal (16) is modulated with a final code word. Ideally, an initial code word is used which is, for every possible time shift of that code, substantially orthogonal to all the final code words in use by the already synchronised secondary stations (4). Such an initial code word does not interfere with the CDMA signals (18) received and transmitted by the already synchronised secondary stations (4) and is therefore very well suited for the purpose of synchronising a secondary station (4) with the primary station (2). If Walsh-Hadamard codes are used as code words the code word corresponding to the first row of the Walsh-Hadamard matrix is an example of such an ideal initial code word.