Traffic channel amplitude estimation with rate determination for the IS-95 downlink

In this paper, we describe amplitude estimation algorithms for the Walsh traffic channels in the downlink of Interim Standard 95 (IS-95). The parameter estimate is designed to improve the performance of a successive interference canceller (SIC) by providing greater reconstruction accuracy. A feature of the IS-95 downlink that makes amplitude estimation difficult is that during lowered voice activity levels, bit repetition occurs with a corresponding drop in the symbol energy for a frame of data. As a result, the amplitude level cannot be assumed to remain constant and should be taken into account during signal reconstruction in the SIC. We explore various algorithms for estimating the nominal Walsh traffic channel amplitude level. The distinguishing characteristic of the different techniques is the type of a priori knowledge employed in the estimation. For example, one parameter that may need to be estimated is the bit repetition multiple using a rate determination algorithm.