Power Allocation in Two-Hop Amplify-and-Forward MIMO Relay Systems With QoS Requirements

Abstract

The problem of minimizing the total power consumption while satisfying\ndifferent quality-of-service (QoS) requirements in a two-hop multiple-input\nmultiple-output network with a single non-regenerative relay is considered. As\nshown by Y. Rong in [1], the optimal processing matrices for both linear and\nnon-linear transceiver architectures lead to the diagonalization of the\nsource-relay-destination channel so that the power minimization problem reduces\nto properly allocating the available power over the established links.\nUnfortunately, finding the solution of this problem is numerically difficult as\nit is not in a convex form. To overcome this difficulty, existing solutions\nrely on the computation of upper- and lower-bounds that are hard to obtain or\nrequire the relaxation of the QoS constraints. In this work, a novel approach\nis devised for both linear and non-linear transceiver architectures, which\nallows to closely approximate the solutions of the non-convex power allocation\nproblems with those of convex ones easy to compute in closed-form by means of\nmulti-step procedures of reduced complexity. Computer simulations are used to\nassess the performance of the proposed approach and to make comparisons with\nalternatives.\n