Blind maximum-likelihood detection for decode-and-forward randomized distributed OSTBC

This paper considers the randomized distributed orthogonal space-time block coding (DOSTBC) system proposed by Sirkeci-Mergen and Scaglione, and considers a situation where some of the cooperative relays can disconnect from the network during the data frame transmission. Such an event translates into abrupt changes of the virtual channel matrix at the receiver; and a coherent detector, which assumes that the virtual channel matrix is perfectly known and static, can be severely degraded in performance. We propose a blind maximum-likelihood (ML) detector and a non-intersecting subspace (NIS) code scheme for the randomized DOSTBC system. With a mild assumption on the transmission protocol, we show that the proposed blind ML detector is robust against the unexpected relay disconnection problem. Moreover, we show that the randomized NIS code scheme can achieve the maximum transmit diversity with the blind ML receiver. Some simulation results are presented to demonstrate the efficacy of the proposed method.

1. INTRODUCTION

Distributed space-time coding schemes have been proposed recently for relay-assisted networks [1]–[3] in order to obtain capacity and diversity gains as in non-distributed multiple-input multiple-output (MIMO) systems. Among the existing schemes, the randomized distributed orthogonal space-time coding (DOSTBC) scheme proposed by Sirkeci-Mergen and Scaglione [3] has been shown to be effective in achieving the maximum transmit diversity with coherent maximum-likelihood (ML) reception without requiring extra control information overhead for a centralized code allocation procedure.