Multi-Antenna Relay Nodes in OFDM Systems

Abstract

In this paper we study different ways of embedding multi-antenna relay nodes to OFDM systems. We compare the performance of half-duplex Amplify and Forward, Amplify and Forward within the Cyclic Prefix and Decode and Forward relays in combination with multi-stream MIMO communication. We show that the eigenvalue spread of the effective channel matrix is much higher for the Amplify and Forward relaying protocols compared to the Decode and Forward protocols. Thus, Decode and Forward relays offer better spatial multiplexing possibilities.In particular we test the performance of the different relaying protocols for a 4x4x4 relay network in the downlink of a metropolitan area network. We show that Amplify and Forward within the Cyclic Prefix outperforms half-duplex Amplify and Forward and Decode and Forward relaying for a SNR up to 20dB. Only at higher SNR Decode and Forward performs better due to its higher spatial multiplexing possibilities.

On the Design of Amplify-and-Forward MIMO-OFDM Relay Systems With QoS Requirements Specified as Schur-Convex Functions of the MSEs

“…The transmit and receive antennas are assumed to be adequately separated so as to make the channel realizations statistically independent in the spatial domain. Comparisons are made with SA (suboptimal approach) in which the unitary matrices S and P in (13) and (21) are set equal to the identity matrix (see [11] - [14]). Fig.…”

“…, ǫ k ] T . The above problem is formally equivalent to the one discussed in [11] meaning that the matrices U and F solving (P 2 ) have the same form of those computed in [11] and are given by (13) in the text. For notational convenience, we denote by P T (U, F) the transmit power required by the matrices (U, F) and call [E k (U, F)] n,n the corresponding MSE of the kth symbol over the nth subcarrier.…”

Robust Power Allocation for Multicarrier Amplify-and-Forward Relaying Systems

“…In case of a large number of subcarriers, some techniques, such as subcarrier grouping [15,16] and multi-antenna relays [17,18], where one relay can be designed properly to serve multiple subcarriers, can be utilized to considerably reduce the number of relays needed. The power allocation strategies are approached by maximizing the approximated channel capacity under aggregate power constraint (APC) and separate power constraint (SPC), respectively.…”