Minimum Symbol Error Rate Research Articles

Stepped θ ‐QAM for high‐order modulation

M-ary stepped θ-QAM (θ-QAM) for M = 22l, l ≥ 3 based on square QAM is proposed. The signal constellation of stepped θ-QAM and the coordinates of the symbols generalised for modulation order M are presented. Then analyse the symbol error rate (SER) performance, and the optimum value of θ in terms of minimum SER for stepped θ-QAM in additive white Gaussian noise and fading channels. Through computer simulations, the theoretical results are validated and show that stepped θ-QAM offers better error performance than θ-QAM.

Low Complexity Post-Distorter for Visible Light Communications

In this letter, a visible light communication (VLC) link affected by the light emitting diode (LED) nonlinearity and dispersion due to the IEEE 802.15 PAN channel impulse response is considered. To mitigate severe intersymbol interference and LED nonlinearity, computationally complex classical post-distortion techniques fall short in terms of applicability to massively connected 5G deployments (as in a VLC attocell) due to increased demand on resources and intractability of implementation. To address these issues, this letter proposes a low-complexity reproducing kernel Hilbert space-based post-distorter using a better sparsification technique equipped with an adaptive kernel width optimized by a minimum symbol error rate (MSER) criterion. Use of the proposed MSER metric for kernel width optimization reduces the computational complexity at the receiver, without compromising on the bit error rate. An upper bound on step-size to guarantee convergence of the proposed post-distorter is analytically derived, and the steady-state mean square error is also analyzed theoretically and validated by simulations. Furthermore, analytical upper bounds for bit error rate and steady-state dictionary size are also derived.

Performance Analysis of a Multi-layered SVD Based STBC System

Multiple-Input Multiple-Output transmission systems using orthogonal frequency-division multiplexing is a key solution in wireless communications. The performance of MIMO-OFDM systems can be improved using coding schemes such as Space–Time Block Coding (STBC), Singular Value Decomposition (SVD) and Vertical Bell Labs Layered Space–Time Architecture (VBLAST). In this paper we present a (4 × 4) cascaded STBC–SVD multi-layered encoder structured in a VBLAST architecture. The STBC output streams are SVD encoded to improve symbol error rate (SER) performance. The introduced system achieves both spatial multiplexing and diversity gains simultaneously and maintains reliable SER performance. We study the effect of ordering the output streams of the STBC before applying the SVD encoding. We show that there is an optimum ordering that guarantees a minimum overall SER. MATLAB® simulations show that the proposed system performs better over other conventional VBLAST systems. Moreover, we show that better performance is not associated with an increase in the computational complexity.

Minimum Symbol-Error Rate Based Adaptive Decision Feedback Equalizer in Underwater Acoustic Channels

Adaptive linear equalizer, whose coefficients are designed to be adjustable to the channel impulse response, has emerged as a simple and efficient technique to adaptively compensate for the channel fading. However, conventional adaptive linear equalizers suffer from performance degradation and slow convergence in the underwater acoustic channel with large delay spread. To solve this problem, in this paper, we propose a novel adaptive decision-feedback equalizer (DFE) based on the minimum symbol-error rate (MSER) criterion. Specifically, by taking the sample-by-sample adaptation into account, the problem is first formulated as minimizing the norm between two consecutive adaptations under the constraint that the latest adaptation will provide correct detection for both the current and past symbols. Then we solve the optimization problem by using the Lagrange multiplier method to obtain the adaptive DFE that minimizes the sequential symbol detection error with a fast convergence rate. Simulation results show that the proposed MSER-based adaptive DFE significantly outperforms the existing equalizers in terms of convergence speed and steady-state performance for underwater acoustic channels.

Finite dictionary techniques for MSER equalization in RKHS

Adaptive channel equalization is a signal processing technique to mitigate inter-symbol interference in a time dispersive channel. For adaptive equalization, minimum mean square error (MMSE) criterion-based reproducing kernel Hilbert spaces (RKHS) approaches such as the kernel least mean squares (KLMS) algorithm and its variants have been suggested in the literature for nonlinear channels. Another optimality criterion, based on minimum bit/symbol error rate (MBER/MSER), is a better choice for adapting an equalizer as compared to MMSE criterion. A kernel-based minimum symbol error rate (KMSER) equalization algorithm combines minimum symbol error rate (MSER)-based approaches with RKHS techniques. However, most algorithms in RKHS such as KMSER/KLMS require infinite storage requirement and hence cannot be practically implemented. To curtail the infinite memory requirement, and make adaptive algorithm suitable for implementation with finite memory and processing power, we propose quantized KMSER (QKMSER) and fixed-budget quantized KMSER (FBQKMSER)-based equalizers in this paper. In this paper, we derive the dynamical equation for MSE evolution of the QKMSER and FBQKMSER and find their performance to be asymptotically close to the MSE behavior of the KMSER. Also, it is found via simulations that the tracking performance of FBQKMSER is better than all the compared algorithms in this paper which is particularly useful for non-stationary channels.

Adaptive Sparse Dictionary Based Kernel Minimum Symbol Error Rate Post-Distortion for Nonlinear LEDs in Visible Light Communications

Visible light communications (VLC) has emerged as one of the prominent technologies to cater to the ever-increasing high-speed-data demand for proposed fifth-generation (5G) systems. However, two main issues affect the performance of VLC in an indoor environment: a) nonlinearity of light-emitting diode, which renders the overall system nonlinear; and b) intersymbol interference due to the propagation channel, which closes the eye diagram of the transmit constellation and, hence, causes it to be unsuitable for detection. To counter these artifacts, complex post-distortion receivers such as the Volterra-decision feedback equalizer (DFE) have been proposed to recover the transmit symbols. In this paper, the use of a reproducing kernel Hilbert space-based minimum symbol error rate equalizer is proposed that provides performance comparable to a long Volterra-DFE, with much less computational cost. Simulations have been carried over IEEE 802.15 personal area network (PAN) channels, which suggest that the proposed approach gives equivalent performance in an indoor VLC channel, as compared with Volterra-DFE with far fewer computations. An analytical expression for mean square error dynamics over these channels is also derived, and it is observed that the theoretically derived expression matches the simulation results for the considered IEEE 802.15 PAN indoor VLC channels.

Generalized Unequal Error Protection Rateless Codes for Distributed Wireless Relay Networks

A generalization of unequal error protection (UEP) rateless codes and distributed rateless codes for distributed relay networks is proposed. We consider a two-hop relaying network where a single source transmits UEP rateless coded data to a destination via multiple relays. At the relays, the UEP rateless coded symbols are re-encoded by distributed rateless codes (DRC) to minimize the redundancy at the second hop. Previously introduced UEP rateless codes (URC) have supported a limited number of importance classes, mostly two classes, and targeted importance levels suited to a specific application. In this paper, however, we formulate an optimization problem to provide optimal URC in terms of the symbol error rate (SER) given any specific number and strengths of importance levels. Next, another optimization is proposed to obtain DRC with the minimum SER at a given overhead, which utilizes information of common symbols among the relays. The optimization methods are based on the AND-OR tree analysis and sequential quadratic programming. In addition, we evaluate the minimum achievable end-to-end symbol error rates over the wireless relay networks.

Alamouti-coded decode-and-forward protocol with optimum relay selection and power allocation for cooperative communications

Abstract In this paper, an Alamouti-coded decode-and-forward protocol with optimum relay selection for three-user one destination cooperative communications is investigated. Particularly, we design the new protocol that allows the source node retransmitting the signal to the destination node at the same time as the relay node forwarding the received signal to the destination node with an Alamouti coding scheme. We exploit the cooperative maximum ratio combining technique (C-MRC) at the destination for combining a multiple copy of received signals. Therefore, the proposed scheme achieves the maximum diversity gain and lower probability of error in comparison with the existing decode and forward protocol. We also analyze a symbol error rate (SER) upper bound of the single relay system, and exploit a result of this analysis to select the optimum relay in a multiple-relay cooperation scheme based on the minimum SER selection strategy. Moreover, the optimum power allocation for the proposed protocol is derived, and it is able to provide the optimum transmission power strategy to the source and the relay nodes in order to achieve the minimum probability of error. In the performance analysis, the theoretical error probability is studied and compared with the simulation results. Simulation results indicate that the proposed protocol significantly outperforms the existing protocols, and the theoretical error probability curve is relatively close to the simulated SER curve.

Transmit-Receive Antenna Pair Selection in Full Duplex Systems

In this letter, a novel transmit-receive antenna pair selection (TRAPS) scheme is proposed for bidirectional full-duplex (FD) communications between two nodes, where each node is equipped with two antennas, used for either transmission or reception. Specifically, one transmit and receive antenna combination is selected based on two system performance criteria: 1) maximum sum-rate (Max-SR), and 2) minimum symbol-error-rate (Min-SER). For the Max-SR approach, we obtain a sum-rate upper bound. And for the Min-SER, a SER lower bound is derived, by introducing a simple near-optimal Min-Max criterion. Finally, we compare the proposed TRAPS approaches with the traditional FD communication system in terms of average sum-rate and SER, respectively. Simulation results verify our analysis, and show a significant performance improvement.

Relay Selection in Two-Way Cooperative Systems

In this paper, we present a design of two-way communication system with relay selection in two-way cooperative system over cascaded Nakagami- $$m$$ m fading channels. In the proposed scheme, in which all terminals are in motion as mobiles or vehicles, two users first broadcast their information to relays. Then, a single relay with a minimum sum symbol error rate (SER) will be selected to broadcast the received signals back to the sources. In other words, in the selection process, we investigate a simple suboptimal min-max criterion for relay selection, where a single relay that minimizes the maximum SER of two source nodes will be selected. Specifically, we have derived expressions of cumulative distribution function and moment generating function of end-to-end signal-to-noise ratio. By using these expressions, we have analyzed the performance of considered system in terms of outage probability and SER expression. Numerical and simulation results show the validity of the proposed mathematical analysis and point out the confirmation of the analytical results.

Geographic Cooperative Routing for Minimum Symbol Error Rate in Wireless Multihop Networks

Geographic Cooperative Routing for Minimum Symbol Error Rate in Wireless Multihop Networks

Multiuser Detection in SDMA–OFDM Wireless Communication System Using Complex Multilayer Perceptron Neural Network

The space division multiple access–orthogonal frequency division multiplexing (SDMA–OFDM) wireless system has become very popular owing high spectral efficiency and high load capability. The optimal maximum likelihood multiuser detection (MUD) technique suffers from high computational complexity. On the other hand the linear minimum mean square error (MMSE) MUD techniques yields poor performance and also fails to detect users in overload scenario, where the number of users are more than that of number of receiving antennas. By contrast, the differential evolution algorithm (DEA) aided minimum symbol error rate (MSER) MUD can sustain in overload scenario as it can directly minimizes probability of error rather than mean square error. However, all these classical techniques are still complex as these do channel estimation and multiuser detection sequentially. In this paper, complex multi layer perceptron (CMLP) neural network model is suggested for MUD in SDMA–OFDM system as it do both channel approximation and MUD simultaneously. Simulation results prove that the CMLP aided MUD performs better than the MMSE and MSER techniques in terms of enhanced bit error rate performance with low computational complexity.

Efficient complex radial basis function model for multiuser detection in a space division multiple access/multiple‐input multiple‐output–orthogonal frequency division multiplexing system

An adaptive multiuser detection (MUD) technique using the complex radial basis function (CRBF) network is proposed for space division multiple access–orthogonal frequency division multiplexing (SDMA–OFDM) system. Among various MUDs, the linear minimum mean-square error (MMSE) MUD suffers from poor performance and the maximum likelihood (ML) detector is restricted by high computational complexity. Hence, the cost function minimisation-based detector like minimum symbol error rate (MSER) is preferred because of significant performance gain over MMSE MUD and complexity gain over ML detector. Moreover, the MSER detector also has a potential of surviving in overload scenario, where the number of users are more than that of the number of receiving antennas. However, in all these techniques, the requirement of channel estimation adds an extra complexity whereas, the proposed CRBF detector approximates the channel parameters in training phase and detects signals in testing phase. It also has low complexity, better performance compared with MSER MUD and also supports overload scenario. Each neuron in the proposed CRBF network is assembled with ‘sech’ activation function, as this function can do better complex non-linear mapping than Gaussian activation. The simulation study and performance evaluation of CRBF MUD is investigated, considering both data and image transmission.

Minimum symbol error rate multiuser detection using an effective invasive weed optimization for MIMO/SDMA–OFDM system

SUMMARYSpace division multiple access–orthogonal frequency division multiplexing system has become a potential wireless communication system by offering high spectral efficiency, performance and capacity. This article deals with minimum symbol error rate (MSER)‐based multiuser detection (MUD) technique for the space division multiple access–orthogonal frequency division multiplexing system using an efficient invasive weed optimization (IWO) algorithm. The IWO algorithm is used for finding optimal weights such that the probability of error is directly minimized rather than minimizing the mean square error. Because of this, the MSER MUD is able to detect users even in overload scenario, where the number of users is more than the number of receiving antennas, unlike several classical detection techniques. The IWO is inspired from the nature of invasive colonization of weeds and relatively simple compared with other optimization techniques. The bit error rate performance of the proposed IWO‐aided MSER MUD is found to be better than minimum means square error and differential evolution algorithm‐aided MSER MUDs. Simulation results show that the proposed IWO MSER achieves faster convergence and lower complexity compared with the differential evolution MSER MUD. Copyright © 2013 John Wiley & Sons, Ltd.

Performance of Adaptive Modulation Scheme for Adaptive Minimum Symbol Error Rate Beamforming Receiver

This paper considers adaptive beamforming receiver that support multiple users, each having one transmit antenna. In certain circumstances, symbol error rate (SER) performance of the beamforming receiver degrades severely. In order to minimize the SER, minimum symbol error rate (MSER) beamforming receiver is utilized. Then, we propose an adaptive modulation scheme for the receiver to maintain the average SER below the target SER while maximizing the average throughput. The scheme uses the information on the direction of arrival and the average signal-to-noise ratio to decide the appropriate modulation mode. For comparison, the proposed scheme is also applied to minimum mean square error (MMSE) beamforming receiver system. Simulations were carried out in the presence of single and two interferers. Simulation results show that the performance of the proposed algorithm employing MSER beamforming is superior to its MMSE counterpart, with the largest advantage of 0.21 in the outage probability.

Precoder Design in the Presence of Spatial Correlation for Macrocell Environments

A precoder scheme based on the geometrical propagation model for macrocell environments is proposed. Employing the geometry information, spatial correlation matrices of both link ends are derived in closed-form. With the spatial correlation feedback, a computationally efficient solution is obtained to minimize the Chernoff bound on pairwise error probability (PEP). Simulation results show that the proposed scheme can converge to the solution fast, and the symbol error rate (SER) performance is close to that of the minimum SER upper-bound scheme with lower complexity. For both the cases of two transmit antennas and constant transmit-side correlation, it becomes an optimal precoder of minimizing SER upper-bound.

COMPARATIVE ANALYSIS OF MODULATION SCHEMES USING ADAPTIVE EQUALIZATION AS FADING MITIGATION TECHNIQUE

Inter-symbol interference (ISI) due to multipath fading is a vital problem in high-speed wireless communication which restricts communication quality and capacity. Therefore, in addition to choosing a fading mitigation technique, it is also important to strategically select a modulation scheme for effective data transmission. Recent literature review on wireless standards, such as 3G and 4G indicates that QAM and QPSK are suitable choices for data transmission. In this paper, a comparative analysis on selected modulation schemes is performed in a fading environment. The mitigation of fading is done using adaptive equalization technique. Also, we show that the signal to noise ratio (SNR) is an important parameter to choose. It is observed that, even when an adaptive equalizer is used at the receiver, a very low SNR gives very high symbol error rate (SER). We derive some important conclusions from our simulation result: QPSK shows minimum SER, whereas 256-PSK and 256-PAM perform worse. Given its spectral efficiency and a low SER, the best choice is 256- QAM.

Turbo Multi-User Detection for OFDM/SDMA Systems Relying on Differential Evolution Aided Iterative Channel Estimation

A differential evolution (DE) algorithm aided iterative channel estimation and turbo multi-user detection (MUD) scheme is proposed for multi-user multi-input multiple-output aided orthogonal frequency-division multiplexing / space-division multiple-access (OFDM/SDMA) systems. The proposed scheme iteratively exchanges the estimated channel information and the detected data between the channel estimator and MUD employing a turbo technique, which gradually improves the accuracy of the channel estimation and the MUD, especially for the first iteration. Quadrature amplitude modulation (QAM) is employed in most wireless standards by virtue of providing a high throughput. However, the optimal maximum likelihood (ML)-MUD becomes extremely complex for employment in QAM-aided multi-user systems. Hence, two different DE aided MUD schemes, the DE aided minimum symbol error rate (MSER)-MUD as well as the discrete DE aided ML-MUD, were developed, and their achievable performance versus complexity was characterized. The simulation results demonstrate that the proposed DE aided channel estimator is capable of approaching the Cramer-Rao lower bound with just two or three iterations. The ultimate bit error rate lower-bound of the single-user additive white Gaussian noise scenario has been approached in the range of E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> / N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ≥ 10 dB and E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> / N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ≥ 6 dB for the DE aided MSER-MUD and the discrete DE aided ML-MUD, respectively.

Relay Selection For Multiple Access Relay Channel With Decode-forward And Analog Network Coding

This paper presents a relay selection for decode-and-forward based on network coding (DF-NC) and analog-NC protocols in general scheme of cellular network system. In the propose scheme the two source node simultaneously transmit their own information to all the relays as well as the destination node, and then, a single relay i.e. best with a minimum symbol error rate (SER) will be selected to forward the new version of the received signal. Simulation results show that, the DF-NC scheme with considerable performance has exactness over analog-NC scheme. To improve the system performance, optimal power allocation between the two sources and the best relay is determined based on the asymptotic SER. By increasing the number of relays node, the optimum power allocation achieve better performance than asymptotic SER.

θ-QAM: A parametric quadrature amplitude modulation family and its performance in AWGN and fading channels

We study a parametric quadrature amplitude modulation (QAM) family, called θ-QAM, which includes other known constellations, such as square QAM (SQAM) and triangular QAM (TQAM), as special cases. The versatile structure of the θ-QAM signal constellation, which occurs from the varying angle between the signal points, results in achieving the minimum symbol error rate (SER) or bit error rate (BER), under an average power constraint. The theoretical study aims at providing insight into the trade-off between error performance and complexity of this parametric modulation scheme. Exact analytical expressions are obtained for the SER in additive white Gaussian Noise (AWGN) and Nakagami-m fading channels, while highly accurate BER approximations are presented. Finally, we find the optimum angles, in a minimal SER or BER sense, for a specific signal-to-noise ratio (SNR) and modulation order, M. This serves as an indicator for the appropriate constellation with respect to channel conditions and SER or BER requirements. The presented theoretical analysis is validated via extensive computer simulations.