Enabling linear minimum-mean square error (LMMSE)-based estimation of random time-selective channels, pilot-symbol-assisted modulation (PSAM) has well-documented merits as a fading counter-measure boosting bit-error rate performance. In this paper, we design average-rate optimal PSAM transmissions by maximizing a tight lower bound of the average channel capacity. Relying on a simple closed-form expression of this bound in terms of the LMMSE channel estimator variance, we obtain PSAM transmissions with optimal spacing of pilot symbols and optimal allocation of the transmit-power budget between pilot and information symbols. Equi-powered transmitted symbols, channels with special Doppler spectra, and analytical and simulation based comparisons of possible alternatives shed more light on information-theoretic aspects of PSAM-based transmissions.
Bibliographical noteFunding Information:
Manuscript received January 18, 2002; revised March 7, 2002; accepted March 15, 2002. The editor coordinating the review of this paper and approving it for publication is Dr. Annamalai. The work of G. B Giannakis was supported by the National Science Foundation (NSF) Wireless Initiative under Grant 9979442. This paper was presented in part at the Wireless Communications and Networking Conference (WCNC), Orlando, FL, March 2002.
- Average channel capacity of fading channels
- Linear minimum mean-square error estimation
- Pilot symbol assisted modulation
- Time-selective channels