Linear timing acquisition scheme in DS-CDMA communication system

Timing estimation has been shown an important issue in multiuser communication (Buehrer et al. 1996). Chang and Chen (1997) proposed the optimum timing estimation and confirmed the need of two-stage timing recovery policy: acquisition and tracking. While the complexity of the tracking scheme applying the gradient search algorithm increases linearly to the number of users, the timing acquisition still has non-polynomial (NP) complexity. Timing acquisition with linear complexity, as an M-ary hypothesis testing problem, is therefore needed in practical multiuser communications. This paper not only points out the difference between the design of a linear timing acquisition scheme and the linear detector, but also proposes a novel, simple, and effective criterion for linear timing acquisition design. With a discrete timing assumption, we prove that the estimation error of the linear timing acquisition scheme based on this new criterion converges to zero in L² as the SNR increases to infinity for an arbitrary number of users. In the general case of continuous timing, explanations and simulation results are provided to demonstrate the effectiveness of the linear acquisition scheme by the new criterion. We demonstrate such a linear scheme existing in interference limited operation for an arbitrary number of users