A new iterative detection algorithm for layered space-time receiver in frequency selective fading MIMO channels

The vertical Bell labs layered space-time (V-BLAST) system is a multi-input multioutput (MIMO) system designed to achieve good multiplexing gain. In recent literature, a precoder, which exploits channel information, has been added in the V-BLAST transmitter. This precoder forces each symbol stream to have an identical mean square error (MSE). It can be viewed as an alternative to the bit-loading method. In this paper, this precoded V-BLAST system is extended to the case of frequency-selective MIMO channels. Both the FIR and redundant types of transceivers, which use cyclic-prefixing and zero-padding, are considered. A fast algorithm for computing a cyclic-prefixing-based precoded V-BLAST transceiver is developed. Experiments show that the proposed methods with redundancy have better performance than the SVD-based system with optimal powerloading and bit loading for frequency-selective MIMO channels. The gain comes from the fact that the MSE-equalizing precoder has better bit-error rate performance than the optimal bitloading method.

We propose a novel concatenated coding scheme combined Low Density Parity Check(LDPC) code and vertical Bell Labs layered space-time (VBLAST) code to improve the bit error rate (BER) performance for Free-space optical (FSO) communication links with On Off Keying(OOK) modulation. In the scheme, π-rotation encoding and belief-propagation (BP) decoding algorithm are employed in LDPC code, and minimum mean-square error (MMSE) soft-decision decoding algorithm is used for VBLAST code. Moreover, a joint iterative detection and decoding algorithm of VBLAST code and LDPC code is used to improve the overall link performance. At last, the BER of the proposed scheme over lognormal atmospheric turbulent fading channels is analyzed by using Monte Carlo method. The result shows that the BER of the proposed concatenated coding scheme is much improved than that only use VBLAST code scheme.

In this paper, in order to reduce the computational complexity of the detector of vertical Bell Laboratories layered space-time (V-BLAST) system over time-varying channels, an adaptive detection scheme is proposed based on parallel interference cancellation (PIC). The presented scheme has three units, which are primary adaptive detector, detection ordering determiner, and adaptive PIC detector. The proposed scheme can employ many of known adaptive algorithms for detection of V-BLAST system. In this paper, we present computational complexity of the proposed scheme using LMS, RLS, APA and AMSER adaptive algorithms and evaluate its performance with numerical simulations.

In this paper, an efficient algorithm of finding an antenna switching function is proposed for an antenna-switching scheme in vertical Bell Labs layered space-time (V-BLAST) with hybrid automatic repeat request (H-ARQ). The transmit antenna is switched for each retransmission, where the switching pattern is obtained by the criterion of maximizing the channel capacity. The size of search space in the algorithm is not dependent on the maximum number of transmission but only on the number of transmit antennas. From simulation results, the obtained antenna switching function is dependent on channel correlation characteristics. In addition, the SNR values give little impact on the antenna switching function. Simulation results demonstrate that the average throughput can be further improved by the antenna switching function in a correlated fading channel, without adding much complexity to the process.

In this paper, we propose a new V-BLAST (Vertical Bell Laboratories Layered Space Time) detection algorithm which considers the channel estimation error. Assuming that orthogonal training sequences are used for the channel estimation, we estimate the noise variance and the channel error variance, and use them to form the new nulling vector of V-BLAST detection algorithm. In high SNR (signal-to-noise ratio), the new nulling vector minimizes the power of unexpected terms generated by channel errors. With simulations, we test the performance of the proposed algorithm.

A performance comparison between convolutional coded vertical Bell-lab layered space time (V-BLAST) and groupwise space time trellis coded (GSTTC) multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems is presented in this paper. Both systems have the same data rate and employ receivers with comparable complexity, which are zero-forcing, minimum mean square error (MMSE) and list sphere decoder (LSD) based turbo receivers. Simulation results show that V-BLAST significantly outperform the GSTTC systems when MMSE or LSD based turbo receiver is applied, while GSTTC perform similarly to or better than the V-BLAST systems when zero-forcing detection algorithm is applied.

This paper presents linear and nonlinear precoding design for error-rate improvement in orthogonal space-time block-coded (OSTBC) multiple-input-multiple-output (MIMO) orthogonal frequency-division-multiplexed (OFDM) downlink, where both the conditional mean of the channel gain matrix and the channel gain covariance matrix may be available at the transmitter. The conditional means of the channel matrix are derived for a general transmit-antenna-correlated frequency-selective fading MIMO channel with estimation errors and feedback delay. Mean-feedback linear precoding and nonlinear Tomlinson-Harashima precoding (THP) are developed to maximize the signal-to-noise power ratio (SNR). The intuition that when the mean feedback becomes accurate the mean-feedback precoding outperforms covariance precoding is confirmed. Dual-mode precoding is also proposed, in which the novel mean-feedback precoding or covariance precoding is adaptively chosen at the receiver. The precoding-mode switching metric is the maximized SNR, which is an indicator of the error rate. The receiver calculates its metric, selects the mode that achieves a higher SNR, and decides whether mean feedback is necessary. Our proposed precoders (both mean feedback and adaptive) significantly reduce the system error rate. Nonlinear precoding is shown to outperform linear precoding. Adaptive precoding outperforms both mean-feedback precoding and covariance precoding if individually applied in OSTBC OFDM.

We propose an improved Vertical-Bell Labs layered space-time (V-BLAST) architecture by introducing space-time trellis codes (STTC) into each layer of the V-BLAST system. Multiple transmit antennas are used in each layer of this system and STTC is employed to introduce temporal and spatial correlation into signals transmitted. At the receiver, we use group interference suppression to reduce decoding complexity dramatically. This system performs much better than traditional V-BLAST system and meanwhile has comparatively low decoding complexity.

In the conventional Vertical Bell Laboratory Layered Space-Time (V-BLAST) receiver with successive interference cancellation (SIC) decoding, the diversity order for the first detected symbol is the lowest, hence its error probability dominates the overall average error probability. In this thesis, a new SIC scheme was presented, called iterative post SIC (IP-SIC) that can increase the diversity order to a fixed desired value for all symbols, thereby significantly reduce the overall average error probability. The key to the technique is that after the interference from all substreams is subtracted from the received vector (the resulting vector will be referred to as the modified received vector), the detected symbol times its channel vector is added to the modified received vector one at a time and the symbol is detected again. Important features of the proposed approach are the increase in diversity order for those symbols detected earlier and the flexibility of balancing the increase in diversity order and the suppression of remaining interference. The latter feature can be used to further reduce the average error probability. The proposed technique is applied to the V-BLAST and space-time block coded V-BLAST system and its performance and computational complexity are analyzed.

Previous studies unveiled that huge channel capacity can be achieved by employing multi-element antenna arrays at both transmitter and receiver. Foschini et.al. proposed a vertical Bell Laboratories layered space-time (V-BLAST) system with a detection algorithm based on decision feedback. This system is computationally efficient and yet supporting a high data rate. However, the detection algorithm shows unsatisfactory performance when an equal number of antennas are employed at both ends. In this paper, a parallel detection algorithm is proposed to improve the performance in such scenarios. The detector consists of many low complexity sub-detectors, all of them operating in parallel on a sub-channel matrix. By selecting the submatrix appropriately the overall performance can be improved substantially.

In the conventional zero-forcing ordered successive interference cancellation (ZF-OSIC) or minimum mean square error ordered successive interference cancellation (MMSE-OSIC) detection algorithm of vertical Bell-Labs layered space-time (V-BLAST) architecture, there exists an undesirable processing delay due to the calculation of the matrix pseudo-inverse and power reordering in detecting the symbol in each layer. The parallel interference cancellation (PIC) algorithm has a lower processing delay but poorer performance. Based on the features of SIC and PIC algorithms, an integrated PIC and OSIC detection (IPOD) algorithm is proposed which can lower the complexity as well as the processing delay of the whole algorithm with little performance loss. Moreover, there is an alterable parameter in IPOD algorithm which can be changed to obtain different trade off between complexity and performance. Thus, the proposed algorithm is more feasible for practical applications.

In this paper, we propose and analyze an Adaptive Modulation System with optimal Turbo Coded V-BLAST (Vertical-Bell-lab Layered Space-Time) technique that adopts the extrinsic information from MAP (Maximum A Posteriori) Decoder with Iterative Decoding as a priori probability in two decoding procedure of V-BLAST scheme; the ordering and the slicing. Also, comparing with the Adaptive Modulation System using conventional Turbo Coded V-BLAST technique that is simply combined V-BLAST scheme with Turbo Coding scheme, we observe how much throughput performance can be improved. In addition, we apply a STD (Selection Transmit Diversity) scheme to the systems for more performance improvement. The results show that the proposed system applying a STD scheme gains about 1.77 Mbps at 11 dB SNR (Signal to Noise Ratio) compared to the conventional system using 2 transmit and 2 receive antennas.

Vertical Bell labs layered space-time (V-BLAST) is designed to exploit the capacity advantage of multiple antenna system in rich-scattering environments. In this paper, we propose a low complexity detection algorithm with respect to the maximum-likelihood (ML) criterion. This algorithm deploys sorted QR decomposition to construct a ML trellis. A Viterbi-like algorithm is used to find a near optimal solution in the trellis. The complexity of this algorithm is lower than that of full ML. When small size constellation is used, the proposed algorithm is less complex than MMSE-OSIC. The performance of the proposed algorithm is close to that of full ML.

The transmission scheme of multilayered space-time trellis codes (ML-STTC) achieves tradeoff between diversity gain and multiplexing gain by combining space-time trellis code (STTC) and layered space-time (LST) structure in multiple-input and multiple-output (MIMO) systems. In this paper, iterative minimum mean square error (MMSE) group detection and iterative MMSE interference cancellation (IC) group detection schemes are proposed to improve the performance of ML-STTC. Moreover, the iteration can reduce the influence of the detection order on performance, and compensate for the performance loss of the firstly detected layer instead of power allocation in the iterative MMSE IC group detection scheme.

This paper presents a novel iterative detection and channel estimation scheme that combines the effort of superimposed training (ST) and pilot-aided training (PAT) for multiple-input multiple-output (MIMO) flat fading channels. The proposed method, hereafter known as joint mean removal ST and PAT (MRST-PAT), implements an iterative detection and channel estimation that achieves the performance of data-dependent ST (DDST) algorithm, with the difference that the data arithmetic cyclic mean is estimated and removed from data at the receiver’s end. It is demonstrated that this iterative and cooperative detection and channel estimator algorithm surpasses the effects of data detection identifiability condition that DDST has shown when higher orders of modulation are used. Theoretical performance of the MRST-PAT scheme is provided and corroborated by numerical simulations. In addition, the performance comparison between the proposed method and different MIMO channel estimation techniques is analyzed. The joint effort between ST and PAT shows that MRST-PAT is a solid candidate in communications systems for multiamplitude constellations in Rayleigh fading channels, while achieving high-throughput data rates with manageable complexity and bit-error rate (BER) as a figure of merit.