Receiver Architectures for MIMO-OFDM Based on a Combined VMP-SP Algorithm

Iterative information processing, either based on heuristics or analytical frameworks, has been shown to be a very powerful tool for the design of efficient, yet feasible, wireless receiver architectures. Within this context, algorithms performing message-passing on a probabilistic graph, such as the sum-product (SP) and variational message passing (VMP) algorithms, have become increasingly popular. In this contribution, we apply a combined VMP-SP message-passing technique to the design of receivers for MIMO-ODFM systems. The message-passing equations of the combined scheme can be obtained from the equations of the stationary points of a constrained region-based free energy approximation. When applied to a MIMO-OFDM probabilistic model, we obtain a generic receiver architecture performing iterative channel weight and noise precision estimation, equalization and data decoding. We show that this generic scheme can be particularized to a variety of different receiver structures, ranging from high-performance iterative structures to low complexity receivers. This allows for a flexible design of the signal processing specially tailored for the requirements of each specific application. The numerical assessment of our solutions, based on Monte Carlo simulations, corroborates the high performance of the proposed algorithms and their superiority to heuristic approaches

A two-step multiuser detection scheme for space-time coded MIMO OFDM systems

In this paper, we investigate transceiver design for a wideband multiuser-multiple-input, multiple-output (MIMO) communication system, where the co-channel users are equipped with multiple transmit and multiple receive antennas. In particular, we develop a two-step hard-decision interference cancellation receiver for a multiuser-MIMO uplink system which employs orthogonal frequency division multiplexing (OFDM) modulation and space-time block codes (STBC). The STBC has been implemented either over adjacent tones or adjacent OFDM symbols and the performances of both implementations have been tested under slowly time-varying channels. The two-step receiver structure has been implemented using a combined interference suppression scheme based on minimum mean-squared error (MMSE) and symbol-wise likelihood detectors, which is then followed by an interference cancellation step. The receiver can suppress and cancel the interference from the co-channel users effectively without increasing the complexity significantly. The paper also includes computer experiments that are intended to improve the understanding of specific issues involved in the design of multiuser STBC-OFDM systems

Space time transceiver design over multipath fading channels

Imperial Users onl