Abstract—In this paper, we develop the optimal transmit beamforming vector and the relay amplifying factors for a multipleinput multiple-output (MIMO) relay communication system with distributed relay nodes. Using the optimal beamforming vector, an iterative joint source and relay beamforming

Cooperative diversity is a transmission technique where multiple terminals pool their resources to form a virtual antenna array that realizes spatial diversity gain in a distributed fashion. In this paper, we examine the basic building block of cooperative diversity systems, a simple fading relay

on the cutset bound at high signal-to-noise ratios (SNRs). Furthermore, Grassmannian signalling at the source achieves this bound within an SNR-independent gap. For moderate-to-high SNRs, a Grassmannian decode-and-forward (DF) relaying scheme is devised, and the optimal signalling dimensionality that minimizes

and the power allocation at the source and relay is performed under an instantaneous sumpower constraint. In particular, it is assumed that the total power used by all the active nodes during each time slot is fixed. d

Abstract—In this paper, we design the source precoding matrices and the relay amplifying matrix of an amplify-and-forward multiuser multiple-input multiple-output (MIMO) re-lay communication system. The minimum mean-squared error (MSE) is taken as the design criterion. We propose an alternating

. The optimal source and relay matrices jointly diagonalize the MIMO relay system into a set of parallel scalar channels. In this paper, we show that this diagonalization is also optimal for a multi-hop MIMO relay system with any number of hops, which is a further generalization of several previously

decoding for nested lattices and applications to

Abstract—In this paper, we study the optimal structure of the source precoding matrix and the relay amplifying matrices for multiple-input multiple-output (MIMO) relay communication systems with parallel relay nodes. We show that both the optimal source precoding matrix and the optimal relay

Abstract—In this letter, we investigate the optimal structure of the source precoding matrix and the relay amplifying matrix for non-regenerative multiple-input multiple-output (MIMO) relay communication systems with the direct source-destination link. We show that both the optimal source precoding

/reception duplexing at the relay node and on the synchronization between the source node and the relay node. We also explore power allocation. Compared to the direct transmission and traditional multihop protocols, our results reveal that optimum relay channel signaling can significantly outperform multihop protocols