Evaluation of Optimum Adaptive Antenna Array Beam Forming Configuration Considering Diversity Effect in W-CDMA Forward Link

Satoru FUKUMOTO  Taisuke IHARA  Mamoru SAWAHASHI  Iwao SASASE  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E85-A   No.7   pp.1594-1603
Publication Date: 2002/07/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Multi-dimensional Mobile Information Networks)
Category: 
Keyword: 
W-CDMA,  adaptive antenna array beam forming,  transmit diversity,  fast transmission power control,  mobile radio,  

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Summary: 
This paper investigates the optimum adaptive antenna array beam forming (AAA-BF) configuration considering the diversity effect provided by transmit diversity (TD) in a multipath fading channel in the W-CDMA forward link. Computer simulation results show that the required transmit signal energy per bit-to-background noise power spectrum density ratio (Eb/N0) at the average block error rate (BLER) of 10-2 using AAA-BF coupled with TD is decreased by approximately 1.0 dB compared to that of AAA-BF assuming the identical number of total antennas when the capacity, i.e., the number of simultaneously accommodated users with the transmission power proportional to the symbol rate, normalized by processing gain, Pg, is below approximately 20%. However, we find that in an interference-limited channel, when the capacity normalized by Pg is above approximately 30%, AAA-BF employing all antennas accommodates a larger capacity compared to AAA-BF coupled with TD because of a sufficient interference suppression effect due to a much narrower beam width despite the absence of the antenna diversity effect. This paper also elucidates in a multi-cell model that AAA-BF employing all antennas can accommodate approximately 1.5 times more users with the average BLER of 10-2 and with the outage probability of 5%, compared to the case with AAA-BF coupled with TD, when the total number of antennas is 8.