tailieunhanh - Báo cáo hóa học: " Adaptive Space-Time-Spreading-Assisted Wideband CDMA Systems Communicating over Dispersive "

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Adaptive Space-Time-Spreading-Assisted Wideband CDMA Systems Communicating over Dispersive | EURASIP Journal on Wireless Communications and Networking 2005 2 216-230 2005 Hindawi Publishing Corporation Adaptive Space-Time-Spreading-Assisted Wideband CDMA Systems Communicating over Dispersive Nakagami-m Fading Channels Lie-Liang Yang School of Electronics and Computer Science University of Southampton Southampton SO171BJ UK Email lly@ Lajos Hanzo School of Electronics and Computer Science University of Southampton Southampton SO171BJ UK Email lh@ Received 23 May 2004 Revised 18 December 2004 In this contribution the performance of wideband code-division multiple-access W-CDMA systems using space-timespreading- STS- based transmit diversity is investigated when frequency-selective Nakagami-m fading channels multiuser interference and background noise are considered. The analysis and numerical results suggest that the achievable diversity order is the product of the frequency-selective diversity order and the transmit diversity order. Furthermore both the transmit diversity and the frequency-selective diversity have the same order of importance. Since W-CDMA signals are subjected to frequency-selective fading the number of resolvable paths at the receiver may vary over a wide range depending on the transmission environment encountered. It can be shown that for wireless channels where the frequency selectivity is sufficiently high transmit diversity may be not necessitated. Under this case multiple transmission antennas can be leveraged into an increased bitrate. Therefore an adaptive STS-based transmission scheme is then proposed for improving the throughput of W-CDMA systems. Our numerical results demonstrate that this adaptive STS-based transmission scheme is capable of significantly improving the effective throughput of W-CDMA systems. Specifically the studied W-CDMA system s bitrate can be increased by a factor of three at the modest cost of requiring an extra dB or dB transmitted power in the context of the .