An Improved Multistage Parallel Interference Cancellation for CDMA in Multipath Fading Channels

• Main Authors: Chih-Hung Lin, 林志鴻
• Other Authors: Bor-Sen Chen
• Format: Others
• Language: en_US
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/97561785394511709756

碩士 === 國立清華大學 === 電機工程學系 === 88 === This study introduces an improved multistage parallel interference cancellation (PIC) technique for binary phase shift keying (BPSK) modulated direct sequence code-division multiple access (DS/CDMA) systems over multipath fading channels. We study the improvement technique for multistage interference cancellation receivers, with a full or only a fractional cancellation of the estimated multiple access interference (MAI) and intersymbol interference (ISI) caused by multipaths at each receiver stage. Because the statistics of MAI and ISI are unavailable in multipath fading channels, the estimations of the MAI and ISI, especially in the earlier stages, contain significant errors. A poor estimation of MAI and ISI due to the relatively high decision bit error rate (BER) may lead to a poor cancellation or even a higher BER at the following decision stages. In this study, the H-infinity filtering is employed to estimate MAI and ISI at the initial stage, and then it can improve the system performance by effective cancellation of MAI and ISI. The H-infinity filtering approach is a robust optimization from the minimax point of view, and it tends to be more effective even in the case that the co-channel interference statistics are less valid. It minimizes the effect of the worst disturbance (including co-channel interference and additive noise). Computer simulation demonstrates that a better transmission performance can be achieved by using the H-infinity filtering algorithm at the initial stage of PIC.