Blind detection of multirate asynchronous CDMA signals in multipath channels

Blind detection of a desired user's signal in a multirate direct sequence code division multiple access (DS-CDMA) system (using either variable sequence length (VSL) or multicode (MC) access) is considered. In multirate CDMA systems, a high-rate user signal may be treated as the superposition of several virtual basic-rate signals. A code-constrained inverse filter criterion (IFC)-based (also CMA-based) blind detector for equal-rate CDMA signals to detect a desired user's signal was recently presented by Tugnait and Li. In this paper novel approaches combining the code-constrained IFC and a penalty function are developed to simultaneously extract all virtual users associated with a given high-rate user in VSL and MC multirate access methods. Global minima of the proposed cost functions are analyzed. An illustrative simulation example is provided.