tailieunhanh - Báo cáo hóa học: " Downlink Space-Frequency Preequalization Techniques for TDD MC-CDMA Mobile Radio Systems"

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: Downlink Space-Frequency Preequalization Techniques for TDD MC-CDMA Mobile Radio Systems | EURASIP Journal on Wireless Communications and Networking 2004 1 67-73 2004 Hindawi Publishing Corporation Downlink Space-Frequency Preequalization Techniques for TDD MC-CDMA Mobile Radio Systems Adao Silva Instituto de Telecomunicaẹões Universidade deAveiro Campus Universitario de Santiago 3810-193 Aveiro Portugal Email asilva@ Atilio Gameiro Instituto de Telecomunicacões Universidade deAveiro Campus Universitario de Santiago 3810-193 Aveiro Portugal Email amg@ Received 31 October 2003 Revised 16 March 2004 The paper considers downlink space-frequency preequalizations techniques for time division duplex TDD MC-CDMA. We consider the use of antenna arrays at the base station BS and analytically derive different preequalization schemes for two different receiver configurations at the mobile terminal a simple despread receiver without channel equalization and an equal-gain combiner EGC conventional receiver. We show that the space-frequency preequalization approach proposed allows to format the transmitted signals so that the multiple access interference at mobile terminals is reduced allowing to transfer the most computational complexity from mobile terminal to the BS. Simulation results are carried out to demonstrate the effectiveness of the proposed preequalization schemes. Keywords and phrases MC-CDMA preequalization antenna array TDD downlink. 1. INTRODUCTION The beyond 3G broadband component of wireless system must be able to offer bit rates of more than 2 Mbps in a vehicular environment and at least 10-20 Mbps in indoor and pedestrian environments 1 . It is consensual that MC-CDMA is one of the most promising multiple-access schemes for achieving such high data rates 2 . This scheme combines efficiently orthogonal frequency division multiplex OFDM and CDMA. Therefore MC-CDMA benefits from OFDM characteristics such as high spectral efficiency and robustness against multipath propagation while CDMA allows a flexible multiple access with good .