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Detection and delay estimation of a new user entering in a CDMA system

CDMA is a promising technique for future mobile satellite communications. In this paper the problem of detecting the presence of a new user at the base station is considered and a detector is proposed to detect that a new user has started transmitting and to make the estimation of its parameters. The detector determines the difference between the received signal and the expected signal, considering that previous users' sequences and delays are known. This difference is used to provide the delay of the new user, with respect to the same arbitrary reference which the other users have, using an structure based on the performance of the correlation. Furthermore this detector is optimised with respect to that structure, using a de-noising technique, in the wavelet transform domain. This paper also presents a new way of de-noising the difference between the received signal and the expected signal, based on the wavelet transform of a PN-sequence.