Multiuser Multi-Hop AF MIMO Relay System Design Based on MMSE-DFE Receiver

To achieve a better long source-destination distance communication in uplink multiaccess scenarios, we propose a multiuser multi-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay technique with nonlinear minimal mean-squared error (MMSE)-decision feedback equalization (DFE) receiver. Under transmission power constraints, this paper focuses on the improvement of reliability, meanwhile, which doesn't lose the effectiveness or require higher complexity. We demonstrate that the optimal structures of relay amplifying matrices lead to a cascading construction for the mean-squared error (MSE) matrices of respective signal waveform estimations at the destination and each relay node. Hence, in (moderately) high signal-to-noise ratio (SNR) environment, the intractable nonconvex optimization problem can be decomposed into easier subproblems for separate optimizations of source precoding and relay amplifying matrices. The source precoding matrix, along with the decision feedback matrix, is obtained by an iterative process, which can converge to a Nash point within the reasonable time. As for the relay amplifying matrices, closed-form water-filling solutions are derived. The simulation and analysis results show that compared to other existing algorithms, which also utilize decomposition methods to simplify operations, the proposed algorithms have better MSE and bit-error-rate (BER) performance without increasing the computing time or signaling overhead, thus providing a new step forward in MIMO relay system design.