Logarithmic Codecs for Adaptive Beamforming in WCDMA Downlink Channels

This paper presents a comparison of two logarithmic codecs for low-medium resolution (6-12 bit) adaptive beamforming in WCDMA terminals. The two different logarithmic coding techniques are based on the utilization of a look up table (LUT), where one method employs a direct LUT conversion, and the other uses linear interpolation requiring a multiplier and a comparatively small LUT. The two logarithmic converters are analyzed with Matlab simulation, where the address precision is varied to generate observations on the adaptive filter misadjustment and its effect on the probability of error. The results indicate that both algorithms cause relatively small mean square error for address precision above 9 bits for the direct LUT conversion and 5 bits for the interpolative conversion. Both techniques render low cost alternatives to a fixed-point implementation while yielding an improved probability of error metric.