DS-CDMA Downlink Site Diversity with Frequency-Domain Equalization and Antenna Diversity Reception

Hirotaka SATO
Hiromichi TOMEBA
Kazuaki TAKEDA
Fumiyuki ADACHI

IEICE TRANSACTIONS on Communications   Vol.E90-B    No.12    pp.3591-3597
Publication Date: 2007/12/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.12.3591
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
DS-CDMA,  frequency-domain equalization,  site diversity,  link capacity,  

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The use of frequency-domain equalization based on minimum mean square error criterion (called MMSE-FDE) can significantly improve the bit error rate (BER) performance of DS-CDMA signal transmission compared to the well-known coherent rake combining. However, in a DS-CDMA cellular system, as a mobile user moves away from a base station and approaches the cell edge, the received signal power gets weaker and the interference from other cells becomes stronger, thereby degrading the transmission performance. To improve the transmission performance of a user close to the cell edge, the well-known site diversity can be used in conjunction with FDE. In this paper, we consider DS-CDMA downlink site diversity with FDE. The MMSE site diversity combining weight is theoretically derived for joint FDE and antenna diversity reception and the downlink capacity is evaluated by computer simulation. It is shown that the larger downlink capacity can be achieved with FDE than with coherent rake combining. It is also shown that the DS-CDMA downlink capacity is almost the same as MC-CDMA downlink capacity.