Subspace based estimation of the signal to interference ratio for CDMA cellular systems

The signal to interference ratio (SIR) has been highlighted in the literature to be an efficient criterion for several radio resource management algorithms such as power control and handoff. We address the problem on how to obtain fast and accurate measurements of this quantity in a practical context. We develop a general SIR estimation technique for CDMA cellular systems, that is based on a signal subspace 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 percent of the actual SIR after only 20 ms, or within 90 percent of the actual SIR after only 40 ms.