Capacity Bound of MIMO Systems with MPSK Modulation and Time-Multiplexed Pilots

Yifei ZHAO
Yunzhou LI

IEICE TRANSACTIONS on Communications   Vol.E89-B    No.9    pp.2629-2632
Publication Date: 2006/09/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e89-b.9.2629
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Wireless Communication Technologies
MIMO system,  channel capacity,  MPSK modulation,  time-multiplexed pilots,  channel estimation,  

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In this letter, we elucidate the ergodic capacity of multiple-input multiple-output (MIMO) systems with M-ary phase-shift keying (MPSK) modulation and time-multiplexed pilots in frequency-flat Rayleigh fading environment. With linear minimum mean square error (LMMSE) channel estimation, the optimal pilots design is presented. For mathematical tractability, we derive an easy-computing closed-form lower bound of the channel capacity. Based on the lower bound, the optimal power allocation between the data and pilots is also presented in closed-form, and the optimal training length is investigated by numerical optimization. It is shown that the transmit scheme with equal training and data power and optimized training length provides suboptimal performance, and the transmit scheme with optimized training length and training power is optimal. With the latter scheme, in most situations, the optimal training length equals the number of the transmit antennas and the corresponding optimal power allocation can be easily computed with the proposed formula.