Lattice-reduction-aided receivers for MIMO-OFDM in spatial multiplexing systems

Abstract

Abstract-Orthogonal Frequency Division Multiplexing (OFDM) significantly reduces receiver complexity in wireless broadband systems and therefore has recently been proposed for use in wireless broadband multi-antenna (MIMO) systems. The performance of maximum likelihood detector in MIMO-OFDM system is optimal, however, its complexity, especially with higher order constellation is prohibitive. A number of other detectors, both linear and non-linear, may offer substantially lower complexity, however, their performance is significantly lower. This paper proposes a class of lattice-reduction-aided (LRA) receivers for MIMO-OFDM systems that can achieve near maximum likelihood detector performance with low complexity. Performance comparisons between LRA receiver and other popular receivers, including linear receivers and V-BLAST in both independent and correlated channels, are provided. It will be shown that the performance of LRA receiver is superior as compared to other sub-optimal detection methods, especially when the channel is correlated.

An Improved Low Complexity Detection Scheme in MIMO-OFDM Systems

“…Although the QRD-M detection reduces the complexity by selecting M candidates and achieves near ML detection performance, the detection complexity of this scheme is still highly increased by the number of transmit and receive antennas, constellation level [6]. Recently, the lattice-reduction-aided detection (LRD) schemes [7], [8] have been proposed to enhance the performance without the increased complexity for MIMO system. Although LRD scheme can achieve near MLD performance with low complexity, it is still unable to approach optimal performance.…”

Improved detection methods for MIMO-OFDM-CDM communication systems

“…In [3], the algorithm was further extended to a general n R × n T MIMO-OFDM system, where n R ≥ n T . In this paper, we apply the technique proposed in [3] is characterized by its columns, h i , i = 1, . .…”

“…h 1 and h 2 , is very narrow (i.e., the vectors are correlated), a small amount of noise can make a received symbol fall out of its own decision region and cause the decoder to make a wrong decision [2]. Therefore, the objective of the LRA technique [3] is to find a change of basis, F which transforms H into H such that the decision regions for a specific lattice and decoder are optimized. An algorithm to compute the change of basis F , for arbitrary numbers of transmit and receive antennas with n R ≥ n T , is given in [3].…”

“…All of these operations are performed at the receiver. Therefore, the operations at the receiver consist of two steps [3] …”

“…To summarise, the steps are as follows: First, we reduce the basis of the extended channel matrix H and calculate the change of basis, F according to the lattice reduction algorithm as detailed in [3]. Second, by using the V-BLAST cancelling and optimal ordering technique, we perform the detection in the new basis.…”