Vertical Bell Laboratories Layered Space-time System Research Articles

BLAST PERFORMANCE IN MIMO WIRELESS COMMUNICATION SYSTEMS

Recently, a new detection algorithm for the Vertical Bell Laboratories Layered Space Time (V-BLAST) system, which we call Enhanced-V-BLAST, or simply E-V-BLAST, was proposed. V-BLAST has demonstrated very high spectral efficiency, there is a wide gap between the original V-BLAST algorithm and the Maximum Likelihood (ML) algorithm. Recently, some algorithms have been presented to make narrower this gap. In a new detection algorithm (Enhanced (E) V BLAST) for V-BLAST system was presented which showed significantly better performance and flexibility than the original V-BLAST detection. The E-V-BLAST algorithm gets closer to the optimum detection Maximum Likelihood (ML) algorithm by making decisions based on multiple symbols. The Enhanced (E)-V-BLAST has two parameters which can be adjusted to achieve a desired performance and complexity trade-off. In the present paper, we analyze the performance of EV-BLAST as a function of the two inherent adjustable parameters of E-V-BLAST. On the basis of this analysis, we obtain some useful characteristics of the E-V-BLAST algorithm which allow one to achieve the desired performance and complexity trade-off.

A novel signal detection algorithm of multiple-input multiple-output Vertical-Bell Laboratories Layered Space-Time for underwater acoustic networks based on the improved minimum mean square error

Multiple-input multiple-output is a commonly used technology supporting for high-rate transmission over frequency-selective fading channels with multiple antennas. Vertical-Bell Laboratories Layered Space-Time is a detection method of a multiple-input multiple-output system, which establishes a direct correspondence between antennas and layers. Studies demonstrate that multiple-input multiple-output Vertical-Bell Laboratories Layered Space-Time is a meaningful way for underwater acoustic networks of high performance. However, considering the hardware constraints and energy consumption, achieving a trade-off between the bit error ratio and complexity is a crucial issue for underwater acoustic networks of multiple-input multiple-output Vertical-Bell Laboratories Layered Space-Time systems. This article proposes a novel signal detection algorithm of multiple-input multiple-output Vertical-Bell Laboratories Layered Space-Time. First, we address the unitary matrix of the underwater acoustic channel by LDLHdecomposition. Second, we order the detection sequence based on the permutation matrix. Third, we detail the implementation of interference cancelation and slice processing. Finally, we perform experiments for comparing the bit error ratio, energy consumption, processing delay, and complexity of the proposed algorithm with zero-forcing Vertical-Bell Laboratories Layered Space-Time, minimum mean square error Vertical-Bell Laboratories Layered Space-Time, and maximum likelihood Vertical-Bell Laboratories Layered Space-Time. Results indicate that our algorithm maintains bit error ratio and the processing delay to that of maximum likelihood Vertical-Bell Laboratories Layered Space-Time algorithm. However, it reduces the energy consumption, which achieves a good trade-off between performance and complexity. This work supports on constructing underwater acoustic networks of multiple-input multiple-output Vertical-Bell Laboratories Layered Space-Time system.

BER Performance of Spatial Modulation Systems Under a Non-Stationary Massive MIMO Channel Model

In this paper, the bit error rate (BER) performance of spatial modulation (SM) systems is investigated both theoretically and by simulation in a non-stationary Kronecker-based massive multiple-input-multiple-output (MIMO) channel model in multi-user (MU) scenarios. Massive MIMO SM systems are considered in this paper using both a time-division multiple access (TDMA) scheme and a block diagonalization (BD) based precoding scheme, for different system settings. Their performance is compared with a vertical Bell labs layered space-time (V-BLAST) architecture based system and a conventional channel inversion system. It is observed that a higher cluster evolution factor can result in better BER performance of SM systems due to the low correlation among sub-channels. Compared with the BD-SM system, the SM system using the TDMA scheme obtains a better BER performance but with a much lower total system data rate. The BD-MU-SM system achieves the best trade-off between the data rate and the BER performance among all of the systems considered. When compared with the V-BLAST system and the channel inversion system, SM approaches offer advantages in performance for MU massive MIMO systems.

Investigation of error performance in network coded MIMO-VBLAST wireless communication systems

Abstract Paper aims to enhance the performance of bit error rate (BER) in wireless communication based on the multiple-input multiple-output (MIMO) system of vertical Bell laboratories layered space-time (VBLAST) algorithm. The VBLAST algorithm uses zero-forcing (ZF) and the minimum mean square error (MMSE) to evaluate the BER of wireless communication. MIMO VBLAST techniques function as an adaptive filter and can minimize the interference and multipath fading in the received signal of the channel. Physical layer network coding (PNC) is a new technique used to exploit the spatial diversity of the MIMO VBLAST system to improve the throughput and performance of wireless communication. The bit-error-rate (BER) of proposed VBLAST MIMO with PNC with binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK) modulation over the additive white Gaussian noise and Rayleigh fading channel are analyzed. The performance of both BPSK and QPSK modulation in two and four antennas are compared. From the simulation results, it was found that the proposed scheme MIMO VBLAST PNC has a 45.2 % higher BER performance compared to the traditional MIMO scheme with an increase in the BER using MMSE and ZF respectively in both two and four antennas.

Joint spatial multiplexing and transmit diversity in MIMO ad hoc networks

This paper investigates the performance of MIMO ad hoc networks that employ transmit diversity, as delivered by the Alamouti scheme, and/or spatial multiplexing, according to the Vertical Bell Labs Layered Space-Time system (V-BLAST). Both techniques are implemented in the ns-3 network simulator by focusing on their overall effect on the resulting signal-to-interference-plus-noise ratio (SINR) at the intended receiver. Unlike previous works that have studied fully-connected scenarios or have assumed simple abstractions to represent MIMO behavior, this paper evaluates MIMO ad hoc networks that are not fully connected by taking into account the impact of multiple antennas on the carrier sense activity in CSMA-like medium access control (MAC) protocols. In addition to presenting a performance evaluation of ad hoc networks operating according to each individual MIMO scheme, this paper proposes simple modifications to the IEEE 802.11 DCF MAC to allow the joint operation of both MIMO techniques. Hence, each pair of nodes is allowed to select the best MIMO configuration for the impending data transfer. The joint operation is based on three operation modes that are selected based on the estimated SINR at the intended receiver and its comparison with a set of threshold values. The performance of ad hoc networks operating with the joint MIMO scheme is compared with the performance when using each individual MIMO scheme and the standard single-input single output (SISO) IEEE 802.11. Performance results are presented based on MAC-level throughput per node, delay, and throughput fairness under saturated traffic conditions.

Joint Virtual MIMO and Network Coding Scheme with Superposition ARQ in Relay System

A new two-way transmission protocol termed VMNC-SARQ (Virtual MIMO Network Coding with Superposition ARQ) was proposed in this paper, which could improve throughput efficiency of DF (Decode-and Forward) relay network signally. In first step, two single-antenna nodes send messages to the double-antenna relay station simultaneously by using a method similar to 2×2 VBLAST (Vertical Bell Laboratories Layered Space Time) system. In step two, relay station processes the decoded signals received from two source nodes through Network Coding, and then broadcasts the combined messages with Alamouti Coding. A novel retransmission strategy will be implemented when demodulation and decoding failure presents. In order to reduce retransmission overhead, we attach the retransmitted packet to the latter normal packet by using higher modulation, and exploit the confidence value of previously error packet to help to recover both packets. Theoretical analysis and simulation results show that the proposed scheme could greatly improve end-to-end throughput efficiency for two-way relaying systems DOI : http://dx.doi.org/10.11591/telkomnika.v12i2.3444

New Trellis Code Design for Spatial Modulation

Spatial modulation (SM), in which multiple antennas are used to convey information besides the conventional M-ary signal constellations, is a new multiple-input multiple-output (MIMO) transmission technique, which has recently been proposed as an alternative to V-BLAST (vertical Bell Labs layered space-time). In this paper, a novel MIMO transmission scheme, called spatial modulation with trellis coding (SM-TC), is proposed. Similar to the conventional trellis coded modulation (TCM), in this scheme, a trellis encoder and an SM mapper are jointly designed to take advantage of the benefits of both. A soft decision Viterbi decoder, which is fed with the soft information supplied by the optimal SM decoder, is used at the receiver. A pairwise error probability (PEP) upper bound is derived for the SM-TC scheme in uncorrelated quasi-static Rayleigh fading channels. From the PEP upper bound, code design criteria are given and then used to obtain new 4-, 8- and 16-state SM-TC schemes using quadrature phase-shift keying (QPSK) and 8-ary phase-shift keying (8-PSK) modulations for 2,3 and 4 bits/s/Hz spectral efficiencies. It is shown via computer simulations and also supported by a theoretical error performance analysis that the proposed SM-TC schemes achieve significantly better error performance than the classical space-time trellis codes and coded V-BLAST systems at the same spectral efficiency, yet with reduced decoding complexity.

Low complexity antenna selection for V-BLAST systems with OSIC detection

Multiple-input multiple-output (MIMO) systems have an advantage of spectral efficiency compared to single-input single-output systems, which means that the MIMO systems have significantly higher data throughput. The V-BLAST (Vertical Bell Laboratories Layered Space Time) scheme is a popular transceiver structure which has relatively good performance. In the V-BLAST scheme, ordered successive interference cancellation (OSIC) technique was proposed as a possible efficient detection method in terms of performance and complexity. However, MIMO systems suffer from high complexity and implementation cost. As a practical solution, a technique called antenna selection has been introduced. Since the existing literature considered only the capacity-based selection, we develop an optimal selection method for V-BLAST scheme using OSIC detection with respect to error rate performance in this article. Its complexity is shown to be proportional to the fourth power of the number of transmit antennas. To reduce the complexity without significant performance degradation compared to the optimal selection method, a near-optimal selection method is also proposed. Simulation results show that the proposed selection method is very close to the performance of optimal selection.

Optimal power allocation and power control for VBLAST systems with M-ary modulations

In this study, the authors propose the optimal power allocation scheme that minimises the symbol error probability (SER) of vertical Bell Laboratories layered space-time (VBLAST) systems using M-ary modulations. The essence of the power allocation is to intentionally cause different received power from each layer at the receiver. By judiciously allocating the transmitting power to the layers, the performance of the successive interference cancelation at the receiver can be significantly improved. The exact SER of the VBLAST systems with non-uniform power allocation is analysed for the Rayleigh fading case. The SER is minimised to determine the optimal power allocation pattern for the VBLAST systems with M-ary modulations. Simulations show that our SER analysis is accurate and the proposed power allocation scheme significantly improves the performance of the VBLAST systems in fast fading environments by 3.5-4 dB. The work is applied to the power control of VBLAST systems in slow fading environments. Significant SNR gains of 8.5-10 dB are observed in the numerical experiments. It is also observed that the proposed optimal power allocation scheme can effectively reduce the SER variation among the layers.

Transmit correlation effect on SIC-ZF receiver for V-BLAST system

It has been shown that transmit correlation causes a signal-to-noise ratio (SNR) loss in the zero forcing (ZF) receiver for V-BLAST (Vertical Bell LAbs LAyered Space-Time) system. In this paper, we investigate the transmit correlation effect on the ZF receiver with successive interference cancellation (SIC). We show that such an unfavorable condition leads to twofold effects on the performance degradation. In addition to the immediate SNR loss, the transmit correlation can increase the propagation factor to spread decision error significantly. These two effects are evaluated analytically. We derive the probability density function (pdf) of the effective SNR at each decoded stream, and hence accurately quantify the SNR loss. We also calculate the decision error propagation factor in terms of its second moment. In particular, we show that transmit correlation can cause a stable component of error propagation which does not decline during the SIC procedure. Finally, we conduct the simulation to verify the analytical results.

A simplified fixed-complexity sphere decoder for V-BLAST systems

A simplified fixed-complexity sphere decoder (SFSD) with much lower computational cost than that of the original fixed-complexity sphere decoder (FSD) has been developed for signal detection in Vertical Bell Laboratories layered space-time (V-BLAST) systems. Simulation results on a 16-QAM system with 8 transmit and 8 receive antennas show that the SFSD can attain the near-optimal performance with a cost that is about 37% of the counterpart of the original FSD.

Integrated MAP detection for V-BLAST systems without channel estimation

Generally, channel estimation is indispensable for signal detection in vertical Bell Laboratories layered space-time (V-BLAST) systems. However, channel estimation always cannot perfectly obtain the channel state information (CSI), and the inaccurate CSI may result in large performance degradation. In this paper, we propose a novel soft V-BLAST detector, called integrated maximum a posteriori (IMAP) detector. Unlike conventional detectors, the IMAP detector can avoid estimating the CSI and directly generate a posteriori probability of data symbols by efficient iterative computations. Moreover, we design a list-based fast searching algorithm to further reduce the complexity of the proposed detector in the cases of large numbers of transmit antennas or high order modulations. Computer simulation shows that the IMAP detector can approximately achieve the performance of the optimal detector using the perfect CSI.

Reduced complexity detection technique for layered space time block coded multiple-input multiple-output orthogonal frequency division multiplexing

The combination of vertical Bell Labs layered space time (V-BLAST) and space time block coding (STBC), known as a Layered STBC (LSTBC) system, offers high spectral efficiency with a higher order of diversity. The system structure, computational complexity and error performance of the V-BLAST and LSTBC multiple-input multiple-output orthogonal frequency division multiplexing systems are analysed and compared. It is shown that, compared with V-BLAST, the overall diversity order of LSTBC increases two fold. This diversity gain is achieved at the expense of a four–fold increase in the computational complexity of the QR decomposition (QRD) algorithm, required at the receiver of both LSTBC and V-BLAST. The authors propose a modified QRD algorithm which reduces this four-fold complexity to two fold.

Euclidean Geometry LDPC-VBLAST System Design and Performance Evaluation

Among popular multi-transmit and multi-receive antennas techniques, the VBLAST (Vertical Bell Laboratories Layered Space-Time) architecture has been shown to be a good solution for wireless communications applications that require the transmission of data at high rates. Recently, the application of efficient error correction coding schemes such as low density parity-check (LDPC) codes to systems with multi-transmit and multi-receive antennas has shown to significantly improve bit error rate performance. Although irregular LDPC codes with non-structure are quite popular due to the ease of constructing the parity check matrices and their very good error rate performance, the complexity of the encoder is high. Simple implementation of both encoder and decoder can be an asset in wireless communications applications. In this paper, we study the application of Euclidean geometry LDPC codes to the VBLAST system. We assess system performance using different code parameters and different numbers of antennas via Monte-Carlo simulation and show that the combination of Euclidean geometry LDPC codes and VBLAST can significantly improve bit error rate performance. We also show that interleaving data is necessary to improve performance of LDPC codes when a higher number of antennas is, used in order to mitigate the effect of error propagation. The simplicity of the implementation of both encoder and decoder makes Euclidean geometry LDPC codes with VBLAST system attractive and suitable for practical applications.

A low complexity branch-and-bound-based decoder for V-BLAST systems with PSK signals

In this paper, a fast sphere decoder is proposed for the joint detection of phase-shift keying (PSK) signals in uncoded Vertical Bell Laboratories Layered Space Time (V-BLAST) systems. The proposed decoder consists of preprocessing stage and search stage. The preprocessing stage is based on the enhancement of the ordering mean square error decision feedback equalizer (MMSE-DFE). Its role is to generate a tree structure suitable for the search stage. The search stage relies on the depth-first brand-and-bound (BB) algorithm with “best-first” orders stored in lookup tables. Simulation results show that the proposed decoder is able to provide the system with the maximum likelihood (ML) performance at low complexity.

Group transmit antenna selection based on GIS technology for V-BLAST system

The conventional transmit antenna selection for Vertical Bell Laboratories Layered Space Time (V-BLAST) system is very complex because it needs to compute the inverse of channel matrices time after time. In this paper, a new group transmit antenna selection scheme for V-BLAST system is proposed. The 1st group transmit antennas are decided according to a certain selection criterion among the available antennas. Then, with Group Interference Suppression (GIS) technology, the interferences of the transmit symbols from the selected antennas can be suppressed. Finally, the 2nd group transmit antennas are decided among the residual available antennas. Simulations show that its performance is lower than that of the conventional selection scheme. However, the new selection scheme has lower complexity than the conventional one.

Adaptive Modulation and Coding Scheme with Independent MCS Level Selection in MIMO Systems

In this paper, we propose a system that adopts the independent MCS (modulation and coding scheme) level for each layer in the AMC (adaptive modulation and coding) scheme combined with the V-BLAST (vertical Bell lab layered space time) system. From the simulation results, we observe that since the independent MCS level case adapts modulation and coding rate for maximum throughput to each channel condition in separate layers, the combined AMC-V-BLAST system with the independent MCS level selection results in improved throughput compared to the combined AMC-V-BLAST system with the common MCS level selection and the conventional AMC system based on the 1x EV-DO standard. Especially, the combined AMC-V-BLAST system with the independent MCS level achieves a gain of 700 kbps in 7–9 dB SNR (signal-to-noise ratio) range.

A V-BLAST System Using Modulation Set Selection for Reduced-Complexity Tree Searching in the QRD-M Algorithm

This letter presents a new vertical Bell Labs layered space-time (V-BLAST) transmission scheme for developing low-complexity tree searching in the QRD-M algorithm. In the new V-BLAST system, we assign modulation scheme in ascending order from top to bottom tree branches. The modulation set to be assigned is decided by two criteria: minimum performance loss and maximum complexity reduction. We also propose an open-loop power allocation algorithm to surmount the performance loss. Numerical results show that the proposed V-BLAST transmission approach can significantly reduce the computational loads of the QRD-M algorithm with a slight performance degradation.

A Novel Adaptive Detection Scheme based on Parallel Interference Cancellation for V-BLAST System

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.

Performance Analysis of a Modified V-BLAST System With Delay Offsets Using Zero-Forcing Detection

This paper focuses on a modified Vertical-Bell Labs layered space-time (V-BLAST) system, where different delay offsets are intentionally applied to the spatially multiplexed data streams. The proposed system can use only one receive antenna to recover the transmitted information by zero forcing (ZF) detection, whereas the conventional synchronous V-BLAST system requires that M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ges M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> (where M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> and M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> are the number of transmit and receive antennas, respectively). The exact closed-form expression of bit error rates (BERs) is derived for an M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> times M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> modified system with ZF strategy. Compared with the conventional synchronous V-BLAST system, the modified system can achieve M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> -th-order diversity using ZF detection; however, the increase in the diversity order comes at the cost of the multiplexing gain. Although delay offsets in the system introduce an attenuation factor that decreases the instantaneous signal-to-noise ratio, the BER performance of the modified system with proper system parameters demonstrates a performance improvement over the conventional synchronous V-BLAST system.