Andrew P. Millar

Tomlinson Harashima Precoding Design for Non-Regenerative MIMO Relay Networks

In this paper we consider the design of minimum mean square error (MMSE) transceivers for non-regenerative multiple input multiple output (MIMO) relay systems. Our design utilises Tomlinson Harashima precoding (THP) at the source along with linear processors in each stage of the network. Assuming full channel state information (CSI) is available at each node in the network the various processors are jointly optimised to minimise the system arithmetic mean square error (MSE) whilst abiding by average power constraints at both the source and relay terminals in the network. Simulations show that the proposed schemes outperform existing methods in terms of bit error ratio (BER).

Precoder Design for MIMO Relay Networks with Direct Link and Decision Feedback Equalisation

In this letter we derive the source and relay precoders for a multiple-input multiple-output (MIMO) relay system with zero-forcing (ZF) decision feedback equalisation (DFE) when a direct link exists between the source and destination. Assuming full channel state information (CSI) is available at each node in the network, the processors are optimised for a large class of objective functions subject to the ZF condition and average power constraints at both the source and relay terminals. Simulation results show that the proposed design outperforms existing techniques in terms of bit error ratio (BER).

THP Transceiver Design for MIMO Relaying with Direct Link and Partial CSI

In this letter we consider Tomlinson Harashima precoding (THP) for multiple-input multiple-output (MIMO) relay systems with a direct link between the source and destination. It is assumed that the destination can acquire full channel state information (CSI) of all channels, whereas the source and relay have full CSI of the source-relay channel but only acquire statistical knowledge of the source-destination and relay-destination channels. Simulation results demonstrate that, for high signal to noise ratio (SNR) in the relay-destination link, the performance of the proposed design approaches that of non-linear transceivers utilising full CSI.

Initial results on an MMSE precoding and equalisation approach to MIMO PLC channels

This paper addresses some initial experiments using polynomial matrix decompositions to construct MMSE precoders and equalisers for MIMO power line communications (PLC) channels. The proposed scheme is based on a Wiener formulation based on polynomial matrices, and recent results to design and implement such systems with polynomial matrix tools. Applied to the MIMO PLC channel, the strong spectral dynamics of the PLC system together with the long impulse responses contained in the MIMO system result in problems, such that diagonlisation and spectral majorisation is mostly achieved in bands of high energy, while low-energy bands can resist any diagonalisation efforts. We introduce the subband approach in order to deal with this problem. A representative example using a simulated MIMO PLC channel is presented.

Broadband SVD and non-linear precoding applied to broadband MIMO channels

We address the problem of precoding and equalisation of broadband MIMO systems. A new non-block based methods is based on a broadband singular value decomposition, which can decouple a broadband MIMO channel into independent dispersive SISO subchannels. We thereafter apply Tomlinson-Harashima precoding to mitigate the dispersiveness of these SISO subchannels. We present arguments why this is a suitable approach compared to existing methods, underlined by some simulation results.

Training-Based Channel Estimation Algorithms for Dual Hop MIMO OFDM Relay Systems

In this paper, we consider minimum-mean-square error (MMSE) training-based channel estimation for two-hop multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) relaying systems. The channel estimation process is divided into two main phases. The relay-destination channel is estimated in the first phase and can be obtained using well-known point-to-point MIMO OFDM estimation methods. In the second phase, the source-relay channel is estimated at the destination with the use of a known training sequence that is transmitted from the source and forwarded to the destination by a nonregenerative relay. To obtain an estimate of the source-relay channel, the source training sequence, relay precoder, and destination processor, require to be optimized. To solve this problem, we first derive an iterative algorithm that involves sequentially solving a number of convex optimization problems to update the source, relay, and destination design variables. Since the iterative algorithm may be too computationally expensive for practical implementation, we then derive simplified solutions that have reduced computational complexity. Simulation results demonstrate the effectiveness of the proposed algorithms.

Design of ZF and MMSE filter-banks in relay networks with average and peak power constraints

In this paper we consider the design of jointly optimal filter-banks for transmission over frequency selective MIMO relay channels. Utilising block processing we present designs that maximise signal to noise ratio under the zero forcing constraint and minimise the mean square error. Both designs targetted in this paper assume limited power resource at the relaying stage of the network and we resort to techniques from convex optimisation theory to obtain the solutions to the constrained design problems.