Fast Multi-Satellite ML Acquisition for A-GPS

Successful position fix in harsh environments such as indoors and dense urban canyons is a strongly required capability for an assisted global positioning system (A-GPS) receiver. In recently developed cellular networks, receiving fine time assistance and maintaining high-frequency accuracy using downlink measurements are not possible for A-GPS receivers, since node-Bs are asynchronous and are not equipped with a source for precise time and frequency. In this paper, we propose a correlator-based fast multi-satellite maximum likelihood (MSML) algorithm, for A-GPS receivers in asynchronous networks, that achieves fast acquisition utilizing fast computation techniques. From numerous Monte Carlo simulations, it is demonstrated that the proposed fast MSML algorithm, when compared with conventional correlator-based acquisition techniques used in standalone GPS and A-GPS receivers, provides higher detection sensitivity for weak signals in the presence of other strong signals by removing strong inter-satellite interference (ISI).