LMMSE channel estimation for wireless energy harvesting AF relaying

Wireless energy harvesting can be adopted in relaying systems to solve the energy issue at the relay node. Channel estimation is an important aspect of its system design. Thus, in this paper, we study channel estimation for wireless energy harvesting relaying. In the study, we use the linear minimum mean squared error (LMMSE) estimators to estimate the source-to-relay link and the relay-to-destination link separately in an amplify-and-forward relaying system. Time-varying Rayleigh fading channels using the Jakes model are considered. Both time-switching (TS) and power-splitting (PS) energy harvesting strategies are examined. Fixed-gain relaying is compared with variable-gain relaying. The signal-to-noise ratios and the bit error rates are calculated. Numerical results are used to show that the system suffers from an error floor due to the use of LMMSE estimators and that its performance depends on several important system parameters. In particular, it is found that PS outperforms TS, variable-gain relaying is better than fixed-gain relaying, and a stationary relay can lead to better performance than a mobile relay. For PS, the choice of the PS factor is important. On the other hand, the symbol position has little effect on the BER.