Method for blind estimation of a scrambling code for a CDMA 2000 uplink

摘要

A method for estimating a scrambling code used on the uplink of a CDMA 2000 system. The received signal is firstly sampled at twice the chip frequency of the spreading code, and then filtered with a filter adapted to the spreading code and to pulse shaping. Differential processing of the successive samples is applied on the signal thus filtered and the differential values thus obtained are decoded using iterative belief propagation decoding. The decoded values are then used to determine the content of the shift register of the scrambling code generator at a given instant.

主权项

1. A method of estimating a scrambling code used on an uplink of a CDMA 2000 system, a signal emitted by a terminal on said uplink being scrambled using the scrambling code, and then spectrally spread using a spreading code and shaped with a shaping filter, said scrambling code being generated by a generator comprising a shift register looped back on itself, said method comprising:
sampling the signal received by a receiver at twice a chip frequency of the spreading code; filtering the signal thus sampled with a filter matched to the spreading code and to the shaping filter to obtain a series of samples at said chip frequency; applying differential processing on the samples at an output of the matched filter, said differential processing supplying differential values obtained as Hermitian product of samples from said series; decoding iteratively said differential values to obtain a content of values stored in the shift register of the generator of a first maximum length sequence (M-sequence) representing a sum of two offset versions of the scrambling code; and determining, using the content of values stored in the shift register of the generator of said first M-sequence, a content (a0s) of the shift register of the scrambling code generator at a given instant.