Optimal Bit Error Rate Performance Research Articles

BER performance of unmanned aerial vehicle assisted spatial modulation system in Rician channels

Unmanned aerial vehicle (UAV) is an emerging technology with high mobility and flexible reconfiguration. In this paper, an UAV-assisted spatial modulation (SM) system with amplify-and-forward (AF) protocol is presented, and the corresponding bit error rate (BER) performance is investigated over Rician fading channels, where the UAV is employed as a half-duplex relay and remains stationary over a given area, and the path loss exponent and Rician factor depend on the position of the UAV. Based on the imperfect channel state information (CSI), the effective signal-to-noise ratio (SNR) of the system is firstly derived. Then, with this result, we analyze the BER performance of the system, and deduce an upper bound of average BER for evaluation. On these bases, the asymptotic performance under large SNR is analyzed, and asymptotic expression of BER bound is derived to attain the diversity gain which is zero for imperfect CSI and one for perfect CSI. Simulation results demonstrate the effectiveness of the presented performance analysis, and reveal that the degradation arisen from estimation error and multiple antennas at the transmitter in BER performance is serious while the improvement brought by spatial diversity at the receiver is relatively modest. Specifically, the increase of 0.04 in estimation error variance results in the diminution of 12.5dB in performance gain, and the use of eight transmit antennas is 8dB worse than two transmit antennas. At the receiver, the increase in performance gain offered by going from ND=1 to ND=6 is about 4dB. Furthermore, according to the simulation, the optimal BER performance can be reached by adjusting the UAV position and power allocation factor. At last, the open issues and challenges focusing on both the deployment and architecture of this system are highlighted.

Adaptive Pilot Pattern for Massive MIMO Systems

This work proposes a new adaptive pilot pattern used for pilot arrangement at the mobile station and a new channel estimation at the base station. It addresses the bit error rate (BER) performance optimization of wireless channel estimation in massive multiple-input multiple-output systems. First, we propose a new adaptive pilot pattern (APP) that offers a lower BER than the conventional pilot patterns. Then, we suggest a new channel estimation algorithm based on the APP. It is called the shifted APP-channel estimation (SACE). As a result, APP guarantees an optimal BER performance for the different system configurations, channel models, and carrier frequencies. It offers better BER performance than conventional pilot patterns, such as the long-term evolution (LTE) pilot pattern. Moreover, the shifted APP-based channel estimation algorithm solves the error floor caused by the usage of multiple subcarriers. It also offers a signal-to-noise ratio (SNR) improvement that reaches 17 dB at BER $= 10^{-2}$ compared to the conventional minimum mean square error (MMSE) channel estimation.

BER Performance of Uplink NOMA With Joint Maximum-Likelihood Detector

We mathematically derive an upper bound of bit-error rate (BER) of uplink non-orthogonal multiple access (NOMA) systems with quadrature phase shift keying (QPSK) modulation in fading channels. In particular, we exploit the joint maximum-likelihood (ML) detector at a base station (BS) with multiple antennas since it results in the optimal BER performance of a super-imposed QPSK modulated symbols from multiple users. In particular, we obtain a closed-form integral of Q-function with Erlang distributed random variable to derive the BER. We also obtain diversity order of the uplink NOMA systems. Through extensive computer simulations, we validate that our analytical results match well with the simulation results especially in high signal-to-noise ratio (SNR) regime.

A novel quadrilateral companding transform for PAPR reduction in OFDM systems

One of the major limitations of Orthogonal Frequency Division Multiplexing (OFDM) signal is high Peak-to-Average-Power-Ratio (PAPR). Non-linear companding transforms that expand small signals and compress the peak signals reduce the PAPR significantly. The proposed companding scheme transforms the Rayleigh distributed probability distribution function (PDF) of original OFDM signal magnitude into quadrilateral shape PDF; hence the name “Quadrilateral Companding Transform (QCT)”. The proposed method provides better design flexibility to achieve an effective trade-off between PAPR reduction capability and bit-error rate (BER) performance. Theoretical performance of the proposed scheme is characterized by means of transformation gain, complementary cumulative distribution function (CCDF) of PAPR and companding attenuation distortion. The parameters of the proposed companding function are also calculated for optimal BER and PAPR performance. Simulation results confirm that the proposed scheme achieves better BER performance as compared to exponential companding transform, trapezoidal companding scheme and trapezium distribution based companding methods, while achieving almost same PAPR reduction capability. It is also shown that the proposed scheme is a generalized companding scheme and exponential companding transform, trapezoidal companding scheme and trapezium distribution based companding methods are the special cases of our proposed quadrilateral companding transform. BER performance of the proposed QCT is also analyzed over fading channel with and without including the effect of power amplifier.

Improvement of bit error rate performance of MC-CDMA system by using adaptive digital modulation schemes

In Wireless Communication, the transmission channel suffers due to multipath propagation and channel dispersion due to Inter Symbol Interference (ISI), thereby degrades the system performance greatly. Future communication requires high data rate and effective utilization of bandwidth. Hence, there is a need to improve the Bit Error Rate (BER). The proposed work is Adaptive Modulation (AM), combined with Multi Carrier Code Division Multiple Access (MC-CDMA) based transmission system. It is a promising way to increase the data rate and it uses bandwidth in a efficient manner. The Adaptive Modulation based MC-CDMA systems applied to a wide-area environment, can achieve high data rate up to 100Mbps. In this paper M-ary PSK, M-ary QAM and M-ary CPM modulation techniques are used. The Adap-tive modulation based MC-CDMA systems perform well for around 10 number of users. As a whole, the adaptive MC-CDMA system is found to give the optimum BER performance of given digital modulation schemes for fourth generation environment.

Investigation of the phase fluctuation effect on the BER performance of DPSK space downlink optical communication system on fluctuation channel

Phase fluctuation effect is an important phenomenon on bit error rate (BER) performance on fluctuation channel in space downlink optical communication system. During research process, both intensity scintillation and phase fluctuation caused by atmospheric turbulence have been considered on fluctuation channel. Through the analysis of simulation results, the influence of phase fluctuation is not sensitive for wavelength and APD gain factor at high data rate. Besides, receiving diameter and divergence angle can be adjusted properly in order to obtain optimal BER performance. This work is helpful to the research of phase fluctuation and the design of practical system.

Joint Sparse Graph-Detector Design for Downlink MIMO-SCMA Systems

The application of multiple-input multiple-output (MIMO) technique to sparse code multiple access (SCMA) systems is important to enhance the system performance of future fifth generation wireless networks. However, one of the challenges in design of downlink MIMO-SCMA systems is developing near-optimum bit error rate (BER) performance detectors with affordable computational costs. To achieve this goal, we construct a joint sparse graph combining the single graph of MIMO channels and SCMA codewords, and then design the corresponding virtual SCMA codebooks for the detector. To utilize them, a novel joint processing approach based on message passing algorithm is proposed. Furthermore, two strategies for message update on the joint sparse graph, i.e., parallel and serial schedules, are, respectively, presented. Simulations show that, the proposed detector can achieve the optimal BER performance with significantly reduced complexity, compared to the maximum likelihood detector.

M-Algorithm-Based Optimal Detectors for Spatial Modulation

A novel M-algorithm-based detector, namely M- algorithm to maximum-likelihood (M-ML), for spatial modulation (SM) receiver is proposed recently, however, due to the miscalculation of metrics, bit-error-rate (BER) performance of M-ML is far away from optimal actually. In this paper, a modified M-ML detector, which calculates accumulated metrics of each layer and can achieve optimal BER performance, is proposed; Furthermore, an M-algorithm-based constellation- reduction (MCR) method specially for SM in high correlated environment is proposed, MCR is capable of combining with maximum-likelihood (ML) and M-ML to further reduce complexity. The BER performance of M-ML and MCR is simulated, simulation results show that the proposed detectors can achieve almost the same BER performance to ML detector while reducing the computational complexity significantly. Index Terms—Spatial modulation, M-algorithm, correlated channel, maximum-likelihood

Comparative Study of Simplified MAP Algorithms and an Implementation of Non-Parallel-Radix-2 Turbo Decoder

This paper presents hardware and bit-error-rate (BER) performance analysis of simplified maximum-a-posteriori (MAP) algorithms based on piece-wise-linear-approximations and Maclaurin-series-expansion for the turbo codes. From this comparative study, a simplified MAP algorithm with optimal BER performance is selected and an architecture suitable for high speed application is suggested for the design of soft-input-soft-output (SISO) unit. Subsequently, a quantitative model is proposed for estimating the amount of memory required by SISO unit in terms of sliding window size, data width of internal metrics and total number of systematic and parity bits. Thereafter, a non-parallel-radix-2 architecture of turbo decoder which incorporates SISO unit and quadratic-permutation-polynomial interleaver is presented. Application-specific-integrated-circuit (ASIC) implementation of this turbo decoder is carried out in 130 nm complementary-metal-oxide-semiconductor (CMOS) technology node and its power consumption, design area and operating clock frequency are reported. Finally, a comparison with similar contributions in the literature has shown that the implemented turbo decoder achieves energy efficiency of 0.28 nJ/b/iteraions. Similarly, it has achieved a highest throughput of 28 Mbps among radix-2 and radix-4 non-parallel turbo decoders.

Performance Simulation of an EM-Based Iterative Receiver for Underwater Acoustic OFDM System

In this paper, an expectation maximization (EM) algorithm based iterative receiver is utilized in the underwater acoustic OFDM system to improve the spectrum efficiency. A relatively smaller number of pilots are used to determine the initial value for the EM-based channel estimation process. The intermediate estimates of the channel state information generated by the EM algorithm are fed forward to the BCJR decoding unit to achieve the a posterior probability of the transmitted bit sequence. The a posterior probability is then fed back to the EM algorithm to estimate channel state information. The iterative receive process is expected to realize a better channel estimate and bit error rate (BER) performance. Simulation results demonstrate that the EM-based iterative underwater acoustic OFDM system has a fast convergence property, and can achieve a low mean square error (MSE) for the channel estimation and a near optimal BER performance.

Adaptive Maximum Likelihood Sequence Detection for QPSK Coherent Optical Communication System

A novel Viterbi-type adaptive maximum likelihood sequence detection algorithm is developed and investigated in coherent optical communication systems in the presence of both laser phase noise and nonlinear phase noise. Compared with the nonadaptive version, it can self-adjust the effective memory length of the phase estimator and automatically deliver the optimum bit-error rate performance without requiring any prior statistical knowledge of the optical channel. The phase error variance of the estimator is also analytically investigated.

Simple low-complexity detection schemes for M-ary quadrature amplitude modulation spatial modulation

In this study, the authors propose a simple low-complexity detection scheme for Nt×NrM-ary quadrature amplitude modulation spatial modulation that exhibits a much lower computational complexity compared to the conventional maximum-likelihood (ML) detection scheme. The proposed simple low-complexity detection scheme firstly detects the transmitted symbol for each transmit antenna based on modified suboptimal detection, and secondly chooses N (N≤Nt) pairs of the most probable transmit antenna index and transmitted symbol subset, which the transmitted signal most probably belongs to, and finally searches the pair of transmit antenna index and transmitted symbol among these pairs. To further reduce detection complexity of the proposed simple detection scheme the authors also propose an adaptive detection scheme. Simulation results validate that the average bit-error-rate (BER) performance of the proposed simple detection scheme is almost the same as that of the conventional ML optimal detection with significant complexity reduction. Simulation results also show that the adaptive detection scheme can achieve optimal detection BER performance with further complexity reduction compared to the proposed simple low-complexity detection scheme.

The Impact of Nonlinear HPA on the Determination of the Impulse Sample Power in IP-OFDM Systems

The recently introduced impulse postfix OFDM (IP-OFDM) system, which performs channel estimation in time-domain by exploiting the IP instead of pilot tones, can achieve the enhanced bit error rate (BER) performance compared to that of conventional OFDM systems. Since there is a peak-to-average power ratio (PAPR) issue of using the IP, however, the decision criteria for determining the power boosting factor (PBF) of IP were proposed to resolve the PAPR issue while achieving the optimum BER performance in the IP-OFDM system with an ideal high power amplifier (HPA). In this paper, a practical IP-OFDM system with a nonlinear HPA is considered and the impact of nonlinear HPA on the determination of the PBF of IP as well as the BER performance are analyzed. The BER lower bound is also derived in the case of QPSK and 16QAM. It is shown that the approximated lower bound approaches to the simulation results as the PBF is increased. According to the analytical results, due to the nonlinearity of the HPA, 1---3dB increased PBF than the ideal PBF is required to achieve the optimum BER performance, which is even deteriorated compared to that of IP-OFDM with an ideal soft envelope limiter.

Statistical-mechanics approach to wide-band digital communication

The emerging popular scheme of fourth generation wireless communication, orthogonal frequency-division multiplexing, is mapped onto a variant of a random field Ising Hamiltonian and results in an efficient physical intercarrier interference (ICI) cancellation decoding scheme. This scheme is based on Monte Carlo (MC) dynamics at zero temperature as well as at the Nishimori temperature and demonstrates improved bit error rate (BER) and robust convergence time compared to the state of the art ICI cancellation decoding scheme. An optimal BER performance is achieved with MC dynamics at the Nishimori temperature but with a substantial computational cost overhead. The suggested ICI cancellation scheme also supports the transmission of biased signals.

Performance Evaluation of OFDM Amplify-and-Forward Relay System with Subcarrier Permutation

We perform error probability analysis of the uncoded OFDM fixed gain Amplify-and-Forward (AF) relaying system with subcarrier permutation (SCP). Two SCP schemes, named: the best-to-best SCP (BTB SCP) and the best-to-worst SCP (BTW SCP) are considered. Closed-form expressions for the bit error rate (BER) of the above SCP methods are derived. Numerical results manifest that these SCP schemes may outperform one another, depending on the average channel conditions of the links involved. That is, BTB SCP is better at low signal-to-noise ratio (SNR) values, while BTW SCP prevails in the medium and high SNR regime. Thus, it could be concluded that OFDM AF relaying systems may switch from the BTB SCP to BTW SCP in order to achieve optimum BER performance. Moreover, using the derived end-to-end SNR probability density functions (PDF), tight upper bounds for the ergodic capacities of both SCP schemes are obtained.

An application of univariate marginal distribution algorithm in MIMO communication systems

AbstractThe paper discusses a sequence detector based on univariate marginal distribution algorithm (UMDA) that jointly estimates the symbols transmitted in a multiple input multiple output (MIMO) communication system. While an optimal maximum likelihood detection using an exhaustive search method is prohibitively complex, it has been shown that sphere decoder (SD) achieves the optimal bit error rate (BER) performance with polynomial time complexity for smaller array sizes. However, the worst‐case complexity of SD is exponential in the problem dimensions, this brings in question its practical implementation for larger number of spatial layers and for higher‐order signal constellation. The proposed detector shows promising results for this overly difficult and complicated operating environment, confirmed through simulation results. A performance comparison of the UMDA detector with SD is presented for higher‐order complex MIMO architectures with limited average transmit power. The proposed detector achieves substantial performance gain for higher‐order systems attaining a near optimal BER performance with reduced computational complexity as compared with SD. Copyright © 2009 John Wiley & Sons, Ltd.

Experimental investigations on BER degradations due to analogue channel filtering in zero-IF receivers for FDD WCDMA

An experimental relationship between the bit error rate (BER) of a release ‘99 wideband code division multiple access (WCDMA) baseband modem and the error vector magnitude (EVM) due to analogue amplitude/group delay distortions in zero-IF channel filters is presented. The reported data eases system design in choosing the best trade-off between adjacent channel power rejection and optimum BER performance in designing channel filters in Zero-IF receivers for WCDMA.

Virtual MIMO-based cross-layer design for wireless sensor networks

In this paper, a novel multihop virtual multiple-input-multiple-output (MIMO) communication protocol is proposed by the cross-layer design to jointly improve the energy efficiency, reliability, and end-to-end (ETE) QoS provisioning in wireless sensor network (WSN). In the protocol, the traditional low-energy adaptive clustering hierarchy protocol is extended by incorporating the cooperative MIMO communication, multihop routing, and hop-by-hop recovery schemes. Based on the protocol, the overall energy consumption per packet transmission is modeled and the optimal set of transmission parameters is found. Then, the issues of ETE QoS provisioning of the protocol are considered. The ETE latency and throughput of the protocol are modeled in terms of the bit-error-rate (BER) performance of each link. Then, a nonlinear constrained programming model is developed to find the optimal BER performance of each link to meet the ETE QoS requirements with a minimum energy consumption. The particle swarm optimization (PSO) algorithm is employed to solve the problem. Simulation results show the effectiveness of the proposed protocol in energy saving and QoS provisioning

Performance Analysis Based on Channel Matrix Eigenvalue for MIMO Systems in LOS Environments

This paper makes an examination of BER (bit error rate) performance in 2 × 2 MIMO (Multi-Input Multi-Output) systems using spatial multiplexing in a LOS (line-of-sight) environment by analysis using the eigenvalue and eigenvector of the channel matrix and simulation. It is shown that BER performance in a LOS environment is dependent on the phase relation of direct paths and the minimum squared absolute value of the eigenvalue, which are determined by the propagated distance. A technique for improving BER performance in a LOS environment is then considered based on these findings. A receive antenna selection (RAS) technique is presented which uses the minimum squared absolute value of the channel matrix eigenvalue. Proof is then given that BER performance is improved using this RAS technique, thus making clear the validity of this approach for obtaining optimum BER performance in a LOS environment.