Suboptimal Search Algorithm in Conjunction With Polynomial-Expanded Linear Multiuser Detector for FDD WCDMA Mobile Uplink

A suboptimum search algorithm that considers the users´ power profile in conjunction with a primary stage of polynomial-expanded (PE) linear multiuser detector for mobile uplink is proposed to suppress interference level. The initial stage is improved by mathematical analysis using two new ideas based on the Rayleigh-Ritz and Gershgorin theorems for both synchronous and asynchronous users. The performance of the PE structure is further enhanced by a new suboptimum search algorithm as the second stage. The structure of the search algorithm is based on starting from a point close to the optimum search and performing sequential steps to modify it. The proposed structures of the PE method and the suboptimum search algorithm are well suited together and make them collaboratively work without encountering a high level of complexity, since they use similar information as the correlation matrix. The power profile of the users is also considered in the suboptimum search algorithm, which led to more than a 50% reduction of the complexity, while keeping the performance almost the same. The performance of the final structure is carried out by means of computer simulations, and it has been compared to a partial parallel interference cancellation method with optimized partial coefficients. One of the main features of the structure proposed in this paper is that it performs its operations on the canonical formulation of the system, which makes it highly suitable for a broad range of systems such as multicarrier code division multiple access and multiinput multioutput.