Application of auto-regressive spectrum estimation to joint CDMA code detection and interference cancellation

The CDMA forward link consists of multiple users´ signals transmitted synchronously by a base station. In current CDMA systems, the mobile user has knowledge only of its own spreading code; therefore, blind interference suppression (IS) algorithms are required to cancel the multiple access interference (MAI). An algorithm using auto-regressive spectrum estimation (ARSE) methods is introduced to allow the mobile to determine all of the codes that the base station is transmitting. The technique is based on computing an orthogonal code spectrum, analogous to the traditional Fourier spectrum, by correlating each code with the received signal. This technique allows a simple, single stage, joint interference cancellation (JIC) algorithm to be applied to remove the effects of the other users. It is shown that this technique can improve forward link performance by up to 2 dB over interference suppression (IS) techniques such as minimum mean square error (MMSE), with the added advantage of lower sample support requirements which allows fast computation and adaptivity to a changing environment. Application of the technique to asynchronous data is also discussed.