Closed-Loop Mode Phase Controlled Transmit Diversity for OFDM Using Difference Information of Phase Component among Adjacent Subcarriers

Shigenori UCHIDA  Takeo FUJII  Masao NAKAGAWA  

IEICE TRANSACTIONS on Communications   Vol.E85-B   No.3   pp.573-581
Publication Date: 2002/03/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Fundamental Theories
closed loop mode transmit diversity,  OFDM,  broadband wireless channel,  

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The Orthogonal Frequency Division Multiplexing (OFDM) system is one of several suitable candidates for use in broadband wireless communications. However, due to multipath propagation, the received signal suffers from frequency-selective fading which causes significant degradation of system performance. Antenna diversity reception is widely used to solve this problem. However, this approach is not suitable for the downlink, because it increases the complexity and power consumption of the mobile station (receiver). In this paper, we consider closed-loop mode transmit diversity for OFDM, instead of diversity reception, to improve the performance in the downlink. The base station (transmitter) has several transmit antennas and each antenna is weighted by a weighting factor calculated based on feedback information (FBI). This system is a closed loop, since the FBI is fed back from the receiver. We propose a new weight generation scheme by making use of the correlation between adjacent OFDM subcarriers. The performance is evaluated under a broadband wireless channel model by computer simulation. The results show that the proposed weight generation scheme exhibits better performance than the conventional weight generation scheme without increasing the number of the FBI bits in the uplink.