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Space-time trellis codes (STTCs) combine channel coding and multiple-input multiple-output (MIMO) techniques to provide coding and diversity gains for wireless communication systems. The decoding complexity is extremely high because of the high density of branch metric calculations. Thus, this study presents a state-purging mechanism based on the T-algorithm to reduce the computational complexity...
The list demapper has been widely employed for coded multiple-input multiple-output (coded-MIMO) receivers, where only a list of signal vectors is examined in the calculation of likelihood ratio. In the literature, the search of list is operated in the symbol level in accordance with a search metric defined as a function of signal (symbol) vector. Since a signal vector is mapped from a group of (coded)...
Recently, communication systems with multiple transmission and reception antennas (MIMO) have been introduced and proven to be suitable for achieving a high spectral efficiency. Assuming full channel knowledge at the receiver, so-called sphere detectors have been shown to solve the maximum likelihood detection problem at acceptable complexity. In the context of coded transmission, however, the detector...
This paper deals with MIMO detection for rank 4 3GPP Long-Term-Evolution (LTE) systems. The paper revolves around a previously known detector [1], which we shall refer to as RCSMLD (Reduced-Constellation-Size-Maximum-Likelihood-Detector). However, a direct application of the scheme in [1] to LTE/LTE-A rank 4 test cases results in unsatisfactory performance. The first contribution of the paper is to...
In this paper, we complement the open literature by presenting a comparative performance evaluation between conventional and modified Viterbi metrics for soft-decision decoding of binary convolutional codes in the framework of IEEE 802.11n systems with transmit beamforming, space division multiplexing and spatial spreading transceiver architectures. Simulation results show that the inclusion of channel...
The fixed-complexity sphere decoder (FSD) has been proposed to attain the near-optimal performance achieving the same diversity order as the maximum-likelihood decoder (MLD) recently. However, it suffers great redundant computations resulting in high power consumption. In this paper, we conduct an improved algorithm for the original FSD by using early termination (ET). This algorithm (abbreviated...
Soft-In Soft-Out (SISO) MIMO detection algorithms providing soft information to subsequent channel decoder are computationally high complex. Realizations based on depth-first search e.g. the Tuple Search (TS) algorithm enables near full MaxLogAPP optimal detection at much reduced but still high complexity. This paper presents a novel method for the complexity reduction of SISO MIMO detection algorithms...
A modified sphere decoding (SD) scheme is proposed for multiple-input multiple-output (MIMO) communication systems in this paper. The conventional SD goes from the lower dimension to the higher dimension to examine whether a lattice point lies inside the sphere of some radius, which remains fixed for all dimensions. Since the sphere radius directly affects the search range and thus the complexity,...
In this paper we consider the design of multi-stream demodulators for multiple-input multiple-output (MIMO) systems. Our proposed MIMO demodulator is based on the stack tree-search strategy and provides soft-outputs in the form of exact max-log log-likelihood ratios (max-log LLRs). We prove that our proposed demodulator is optimally efficient in that it visits the least number of nodes among all optimal...
The fixed-complexity sphere decoder (FSD) has been proposed to attain the near-optimal performance achieving the same diversity order as the maximum-likelihood decoder (MLD). However, it suffers great redundant computations resulting in very high power consumption. In this paper, we combine the probabilistic tree pruning (PTP) method proposed recently by Shim and Kang with the original FSD. This algorithm...
Air bandwidth is a precious resource for wireless communication. Multiple-antenna (MIMO) systems enable an increase in channel capacity without increasing the air bandwidth. An iterative demapping and decoding at the receiver improves the communications performance remarkably. However, MIMO demapping and channel decoding have a high computational complexity. Energy consumption, latency and throughput...
In MIMO communication systems maximum-likelihood (ML) decoding can be formulated as a tree-searching problem. This paper presents a tree-searching approach that combines the features of classical depth-first and breadth-first approaches to achieve close to ML performance while minimizing the number of visited nodes. A detailed outline of the algorithm is given, including the required storage. The...
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