Joint optimization of source and relay precoding for AF MIMO relay systems

Abstract

In this paper, we investigate a joint source and relay precoding design scheme for an amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay system with absence of the direct link. The joint optimization problem, which is to minimize an objective function based on the mean square error (MSE), is formulated as a nonconvex optimization problem in the AF MIMO relay system. Instead of the conventional iterative method, we use an inequality to derive a lower bound of the MSE under the power constraint for obtaining a suboptimal solution of the objective function, which makes the optimization problem convex and also approaches the existing upper bound of the MSE, especially at the high signal-to-noise ratio (SNR). Numerical results show that this scheme outperforms the previous schemes in terms of either MSE or bit error rate (BER).

Structured optimal transmission control in network-coded two-way relay channels

“…Note, the aforementioned power-delay tradeoff formed by (5) and (6) just poses the problem of whether or not to transmit if an instantaneous packet inflow is not able to form an XORing pair. However, if the scheduler considers downlink transmission error rate in addition, a policy that always broadcasts XORed packets whenever there is a coding opportunity without considering downlink channel states is penalized by (7).…”

“…This method, compared to the conventional store-and-forward transmission, reduces the total number of transmissions from 4 to 3 so that the transmission power is saved by 25 %. Since then, numerous optimization problems have been studied in NC-TWRC, e.g., the precoding scheme design *Correspondence: ni.ding@anu.edu.au Research School of Engineering, College of Engineering and Computer Science, Australian National University (ANU), 2601 Canberra, Australia proposed in [5], the optimal achievable sum-rate problem studied in [6] and the optimal beamforming method proposed in [7].…”