Title :
Performance analysis of closed-loop transmit diversity in the presence of feedback delay
Author :
Onggosanusi, Eko N. ; Gatherer, Alan ; Dabak, Anand G. ; Hosur, Srinath
Author_Institution :
DSPS R&D Center, Texas Instrum. Inc., Dallas, TX, USA
fDate :
9/1/2001 12:00:00 AM
Abstract :
In this paper, a bit-error-rate (BER) analysis for closed-loop transmit diversity in a time-selective Rayleigh fading channel containing feedback delay is presented. In the absence of feedback delay, closed-loop transmit diversity always outperforms open-loop transmit for a given transmitted signal energy. This is no longer true in the presence of feedback delay. We derive closed-form expressions of the average BER for this case assuming QPSK and BPSK signaling. The results of the analysis are instrumental for comparing closed-loop with open-loop schemes under given operating conditions. In particular, we demonstrate that, for a given transmitted energy and number of transmit antennas, open-loop outperforms closed-loop at sufficiently fast channel fading. We also show that, for a given transmitted signal energy and fading rate, closed-loop outperforms open-loop for sufficiently large numbers of transmit antennas while the total average transmitted signal energy is kept constant. For some special cases, closed-form expressions for the fading rate at which the performance of open-loop is equal to closed-loop are obtained
Keywords :
Rayleigh channels; antenna arrays; code division multiple access; delays; error statistics; feedback; land mobile radio; quadrature phase shift keying; radio receivers; spread spectrum communication; transmitting antennas; BER; BPSK signaling; QPSK; bit-error-rate; channel fading; closed-loop transmit diversity; feedback delay; open-loop schemes; performance analysis; time-selective Rayleigh fading channel; transmit antennas; transmitted signal energy; Binary phase shift keying; Bit error rate; Closed-form solution; Delay; Fading; Feedback; Instruments; Performance analysis; Quadrature phase shift keying; Transmitting antennas;
Journal_Title :
Communications, IEEE Transactions on