Power allocation for cooperative systems with training-aided channel estimation

Cooperative communication techniques promise the advantages of multi-input multi-output (MIMO) communications for wireless scenarios with single-antenna terminals. A main assumption in majority of the research work on cooperative communications is the availability of channel state information at the receiver. In practice, knowledge of the channel is obtained by sending known training (pilot) symbols to the receiver. In this paper, we study the effect of training on the performance of an amplify-and-forward cooperative relaying system with pilot-assisted channel estimator over quasi-static Rayleigh fading channels. We consider average received signal-to-noise ratio at the destination node as the objective function and formulate optimization problems for a single-relay scenario under total network power (TNP) and individual node power (INP) constraints. We aim to answer the following fundamental questions: Q1) How should overall transmit power be shared between training and data transmission periods?; Q2) How should training power be allocated to broadcasting and relaying phases?; Q3) How should data power be allocated to broadcasting and relaying phases? Our simulation results demonstrate that optimized schemes significantly outperform the original schemes with equal power allocation. Depending on the relay location, performance gains up to 5.5 dB and 2.8 dB are observed, respectively, under TNP and INP constraints.