Optimal linear-quadratic statistical processing for interference cancellation in CDMA systems

In this paper the application of a linear-quadratic processor is proposed for detection of each user´s signal in a direct sequence code division multiple access system. In this method, some statistical knowledge of interfering transmitters´ signals is used to detect the desired user´s signal without needing exact “a priori” knowledge of the interfering signal parameters such as spreading sequences and signal powers. Parameters of the proposed processor can be obtained by solving a system of linear equations for which many effective techniques exist. A model for this detection procedure is developed and it is shown that a good compromise between complexity and quality of performance can be achieved. Finally, the problem of interference cancellation is also treated from an estimation point-of-view in which a different linear-quadratic processor is used to estimate the interference for further cancellation. Estimated error and probability of error are derived as measures of estimation performance