Code-aided blind detection of the transmission rate for multirate direct-sequence CDMA systems

The problem of rate detection for a multirate direct sequence/code division multiple access (DS/CDMA) systems is considered in this paper. It is assumed that, in each data-frame, each user may transmit its data at one out of a set of available data-rates, depending, e.g., on the kind of data to be transmitted, on the desired quality-of-service, and on the channel state. Relying on the knowledge of the spreading codes of the user whose rate is to be detected, rate detection algorithms based on the application of the generalized likelihood ratio test are here proposed. Both the cases where either the rates of the interfering users have been already detected and are known to the receiver or these rates are not known to the receiver are separately considered. With regard to the performance assessment, the effectiveness of the proposed rate detection strategies is validated, for a single-path fading channel, through both computer simulations and, with regard to the case that the interfering users rates have already been acquired, through a Chernoff-bounding technique.