Optimal antenna selection and power adaptation for underlay spectrum sharing with statistical CSI

Abstract

For underlay spectrum sharing, transmit antenna selection is a low hardware complexity technique that can help the secondary system overcome the performance limitations imposed by the constraints on the interference it causes to a primary system. However, its efficacy depends on the channel state information (CSI) available to the secondary transmitter. We consider a practically appealing model in which the secondary transmitter has only statistical CSI about the channel gains from itself to the primary receiver and is subject to a general class of stochastic interference constraints. We derive an optimal and novel joint antenna selection and continuous power adaptation rule for it that minimizes the average symbol error probability (SEP) of the secondary system. We show that it has an intuitively appealing separable structure. We then analyze its average SEP. Our numerical results evaluate the impact of the interference constraint on both secondary and primary systems, and show that a judicious choice of the interference constraint and its parameters is needed as its impact on the secondary and primary systems can be very different.