Differential acquisition of m-sequences using recursive soft sequential estimation

A novel sequential estimation method is proposed for the acquisition of m-sequences. This sequential estimation method exploits the principle of iterative soft-in-soft-out (SISO) decoding for enhancing the acquisition performance, and that of differential preprocessing for the sake of achieving an enhanced acquisition performance, when communicating over various communication environments. Hence, the advocated acquisition arrangement is referred to as the differential recursive soft sequential estimation (DRSSE) acquisition scheme. The DRSSE acquisition scheme exhibits a low complexity, which is similar to that of an m-sequence generator, while achieving an acquisition time that is linearly dependent on the number of stages in the m-sequence generator. A low acquisition time is achieved with the advent of the property that the proposed DRSSE scheme is capable of determining the real-time reliabilities associated with the decision concerning a set of, say, S consecutive chips. This set of consecutive chips constitutes the sufficient initial condition for enabling the local m-sequence generator to produce a synchronized local despreading m-sequence replica. Owing to these attractive characteristics, the DRSSE acquisition scheme constitutes a promising initial synchronization scheme for acquisition of long m-sequences, when communicating over various propagation environments.