This paper studies the V-BLAST detection in a general multiuser space-time wireless system, in which each user's data stream is either (orthogonal) space-time block coded (OSTBC) for transmit diversity or spatially multiplexed (SM) for high spectral efficiency. The motivation behind this work is that each user adopting a signaling scheme better matched to his own channel condition proves to improve the individual link performance but the resultant co-channel interference mitigation problem is scarcely addressed thus far. By exploiting the algebraic structure of orthogonal code, it is shown that the V-BLAST detector in the considered dual-signaling environment allows for an attractive group-wise implementation: at each iteration a group of symbols, transmitted either from an OSTBC station or from an antenna of an SM terminal, are jointly detected. The group detection property, resulting uniquely from the use of orthogonal codes, potentially improves the dual-mode signal separation efficiency, especially when the OSTBC terminals are dense in the cell. The imbedded structure of the channel matrix is also exploited for deriving a computationally efficient detector implementation. Flop count evaluations and numerical examples are used for illustrating the performance of the proposed V-BLAST based solution.Index Terms-Multiuser detection, spatial multiplexing, spacetime block codes, vertical Bell Labs layered space-time (V-BLAST), multiple-input multiple-output (MIMO).
Abstract-This paper investigates multiuser orthogonal spacetime block coded signal detection within the ordered successive interference cancellation (OSIC) framework. Both the zeroforcing and minimum-mean-square-error ordering criteria are considered. When each user terminal is equipped with no more than four transmit antennas, it is shown that orthogonal transmit redundancy leads to an appealing signal ordering property: in each processing layer the transmitted symbols of an arbitrary user are associated with an identical ordering metric. This guarantees the feasibility of (user based) group-wise symbol recovery through the OSIC mechanism. Analytic bit-error-rate performance is given. Computer simulations and flop count evaluations are also provided for comparing the OSIC based solution with existing multiuser detection schemes reported for the considered system. Index Terms-Multiuser detection, ordered successive interference cancellation (OSIC), array processing, space-time block codes.
In this paper, a simplified maximum likelihood (ML) detector is proposed for multi-input multi-output (MIMO) systems over the Rayleigh flat-fading channels. The main idea of the proposed method is to pre-construct a reduced-size searching set for the optimal ML detection to reduce its computational load without significant performance loss. This can be done by a two-stage searching algorithm combined with the ordered successive interference cancellation scheme. Computer simulations show that with an adequate size of searching set, the proposed simplified ML detection can outperform the conventional MIMO detectors and achieve the same performance as that of the optimal ML detection.Keywords Multi-input multi-output (MIMO) · Maximum likelihood (ML) detection · Reduced-size searching set · Ordered successive interference cancellation (OSIC)
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