Closed-loop transmit diversity schemes for five and six transmit antennas

• Published in: IEEE signal processing letters Vol. 12; no. 2; pp. 130 - 133
• Main Authors: Milleth, J K, Giridhar, K, Jalihal, D
• Format: Journal Article
• Language: English
• Published: 01.02.2005
• ISSN: 1070-9908
• DOI: 10.1109/LSP.2004.840927(410)12

Closed-loop, rate-one, channel orthogonalized space-time block codes (CO-STBCs) for three and four transmit antennas using a single (real) phase feedback term have been proposed . These codes achieve full diversity and result in maximum likelihood (ML) decoding with only linear processing at the receiver similar to OSTBCs. In this paper, we propose a closed-loop STBC for five and six transmit antennas with rate 3/4, where the one parameter feedback angle can be evaluated in closed form. These codes achieve full diversity and are delay optimal. Simulation results comparing the error-rate performance of the CO-STBC with open-loop OSTBC as well as some quasiorthogonal space-time block codes are also provided. While the 1- to 5-dB gain accrued by the closed-loop scheme (over the open-loop methods) is not surprising, the novel contribution of this work is in the approach taken to derive the feedback parameter as a single phase term, which is purely a function of the channel gains.