Improved channel decoding for the CDMA forward link chip-level LMMSE receiver

This paper investigates how to improve channel decoder trellis path metric calculations when convolutional or turbo codes are combined with the chip-level linear minimum mean square error (LMMSE) code division multiple access (CDMA) mobile receiver. These metric calculations require channel state information (CSI) that consists of desired signal amplitude and interference plus noise variance. Several techniques suitable for use with the chip-level LMMSE receiver are presented for estimating CSI. Chip-level simulations are used to evaluate CDMA forward link performance when these techniques are used by the mobile. The results indicate that the channel state estimation scheme that provides the best forward link performance depends on the type of channel code and channel decoder algorithm used in the system.