Subspace-based SIR estimation for CDMA cellular systems

The signal-to-interference ratio (SIR) has been highlighted in the literatu re to be an efficient criterion for several radio resource management algor ithms such as power control and handoff, In this paper we address the probl em on how to obtain fast and accurate measurements of this quantity in a pr actical contest. We develop a general SIR estimation technique for code div ision multiple access (CDMA) cellular systems, that is based on a signal su bspace approach using the sample covariance matrix of the received signal. Analysis and simulation results for an IS-95 like system show that the SIR can be estimated to within 80% of the actual SIR after less than seven fram es, or within 90% of the actual SIR after less than 15 frames, We also stud y a computationally less expensive SIR tracking algorithm based on updating the signal subspace, We show that the algorithm works well in the context of a rapidly time varying channel.