Multiple traffic type CDMA systems using an improved adaptive LMMSE receiver

This paper examines the capacity of a CDMA system which supports multiple data rates and traffic types. The system uses a version of the slotted ALOHA protocol. An adaptive linear, minimum mean-square error (LMMSE) receiver implemented by a modified least-mean squares (LMS) algorithm is used in the system. The modifications to the adaptive LMMSE receiver overcome the well-known limitations of slow convergence and allow it to operate efficiently over fast fading channels. The modifications to the basic LMS algorithm are outlined and the performance of a system with multiple traffic types is investigated. Traffic types are distinguished by data rates and bit error-rate requirements. The performance of a single cell system with various number of users of each traffic type is investigated. The performance of the total system is calculated from the maximum number of users of each traffic type which the system can support and the total system throughput. The effect of limited power control of the user's signals is also investigated.