DS-CDMA SIR estimation with bias removal [cellular system applications]

In direct-sequence code-division multiple-access (DS-CDMA) systems, signal quality estimation is an important receiver function used for power control and rate adaptation. Signal quality is usually measured in terms of a signal-to-interference ratio (SIR). Typically, a short term signal power estimate and a long term interference power estimate are used. As a result, estimation error is mostly due to the short term signal power estimate. In this paper, we consider both subtractive and multiplicative forms of bias removal for SIR estimation, and show that multiplicative bias removal provides lower root-mean-square (rms) error. These bias removal forms are developed for a traditional SIR estimation approach that has been extended to account for interference correlation across Rake fingers due to receive filtering or dispersion. The extension provides an SIR estimation approach suitable for use in conjunction with generalized Rake reception, which also accounts for interference correlation.