Transmission performance of DS-CDMA with RAKE reception adding time-window control loop (TWCL) in multipath fading environment

This paper presents laboratory test measurement results from a post-detection RAKE receiver system with a time-window control loop (TWCL) as the code synchronization scheme under a frequency-selective fading environment. RAKE combining methods, a simple integral demodulation method within a time-window and a recursive least squares (RLS) demodulation method within the time-window that uses the RLS algorithm to realize maximal ratio combining, are investigated. The result shows that the TWCL provides good acquisition and tracking performance under the fading conditions experienced with maximum Doppler frequencies from 5 to 80 Hz. It is also shown that the required E_b /N₀ when the bit-error rate must be 10^-3 under the double-spike frequency-selective Rayleigh-fading model is reduced by 10 dB compared to the non-selective Rayleigh-fading model. The difference of the path-diversity effect between the two RAKE combining methods is only 1 dB