Subscriber location in CDMA Wireless networks

Location estimation in Wireless networks has become an important feature for improvement in public safety service. Its potential applications include location sensitive billing, asset tracking, fraud protection, mobile yellow pages, fleet management, etc. Several location techniques using terrestrial wireless network elements and radio signals have been proposed over the years, but multipath propagation, multiple access interference (MAI), and non-line-of-sight propagation have impeded the accuracy in mobile station (MS) positioning. Traditional location algorithms have derived location estimates assuming single user environment. However this assumption is not correct as measurement bias is introduced due to MAI. An interference cancellation based delay locked loop (DLL) for MS delay estimation is proposed in this paper, which is subsequently used for radio location. A system model is presented and simulations are carried out that show that proposed method provides MS position location quite accurately even in the presence of MAI.