Abstract
This paper investigates the effects of channel estimation error at the receiver on the achievable rate of distributed space-time block coded transmission. We consider that multiple transmitters cooperate to send the signal to the receiver and derive lower and upper bounds on the mutual information of distributed space-time block codes (D-STBCs) when the channel gains and channel estimation error variances pertaining to different transmitter-receiver links are unequal. Then, assessing the gap between these two bounds, we provide a limiting value that upper bounds the latter at any input transmit powers, and also show that the gap is minimum if the receiver can estimate the channels of different transmitters with the same accuracy. We further investigate positioning the receiving node such that the mutual information bounds of D-STBCs and their robustness to the variations of the subchannel gains are maximum, as long as the summation of these gains is constant. Furthermore, we derive the optimum power transmission strategy to achieve the outage capacity lower bound of D-STBCs under arbitrary numbers of transmit and receive antennas, and provide closed-form expressions for this capacity metric. Numerical simulations are conducted to corroborate our analysis and quantify the effects of imperfect channel estimation.
Highlights
An effective way of approaching the promised capacity of multiple-input multiple-output (MIMO) systems is proved to be through space-time coding, which is a powerful technique for achieving both diversity and coding gains over MIMO fading channels [1]
We start by comparing the mutual information bounds, Clower and Cupper, of distributed STBCs (D-STBCs) with the same subchannel estimation error variances, σ12 = σ22 = σe2, and with a single receive antenna for different values of σe2
We have addressed the effect of channel knowledge uncertainty at the receiver on the mutual information of distributed space-time block coded transmission in Rayleigh fading channels
Summary
An effective way of approaching the promised capacity of multiple-input multiple-output (MIMO) systems is proved to be through space-time coding, which is a powerful technique for achieving both diversity and coding gains over MIMO fading channels [1]. We address the effects of channel estimation error at the receiver on the performance of D-STBCs. In particular, we derive lower and upper bounds on the mutual information for Gaussian input signals, and present a limiting value that upper bounds the gap between these bounds at any input transmit powers. Assuming that the summation of the subchannel gains remains constant, we provide the information for positioning the receiving node so as to maximize the mutual information bounds of D-STBCs. we provide the power allocation scheme that achieves the outage capacity lower bound of D-STBCs, and derive closed-form expressions for this capacity metric and its associated power allocation.
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