Bit Error Rate Performance Of System Research Articles

Impact of phase noise on single-tap equalization for fast–OFDM signals under generic linear fading channels

In this correspondence, we present the performance evaluation of a low-complexity fast – orthogonal–frequency–division–multiplexing (F–OFDM) scheme, in the presence of phase-noise (PHN), working under the generic linear fading channels (like two-wave-with-diffuse-power (TWDP) multipath fading and modal dispersion in multi-mode-fiber optic channel). Here, a single-tap zero-forcing (ZF) equalizer is utilized to compensate the channel-impulse-response (CIR) without sacrificing data-rate, in which the discrete-cosine-transform (DCT) operation is replaced by the discrete-Fourier-transform (DFT) operation at the receiver. The phase noise variations are modelled by utilizing the random–walk paradigm, in which PHN is dependent on the model parameters/statistics. Therefore, main focus is on the impact of PHN on the performance of single-tap ZF equalization for F–OFDM signals. Simulation results are presented to illustrate efficiency and efficacy of underlying F–OFDM system, while working under TWDP, Rician and Rayleigh multipath fading linear channels. It can be inferred from results that the PHN severely affects/deteriorates the performance of F–OFDM based communication systems in terms of high bit-error-rate (BER), when the PHN variations are large. Moreover, the TWDP fading model is found to be quite appropriate for analyzing/investigating the BER performance of communication systems using the binary-shift-keying modulation technique.

SSD‐enhanced uncoded space‐time labeling diversity

SummarySpace‐time labeling diversity (STLD) has been shown to be an efficient technique for improving the bit error rate (BER) performance of an uncoded space‐time coded modulation system. In this paper, signal space diversity (SSD) is incorporated into the uncoded STLD system to further enhance the system BER performance. A tight closed‐form union bound on the BER of the proposed system is derived and is used to optimize the rotation angle of the SSD scheme. Simulation results are used to confirm the theoretical bound derived for the system. The results also show performance gains of approximately 2.0 dB at a BER of 10−6 and 1.6 dB at a BER 10−4 from incorporating SSD into the uncoded STLD system using 16QAM and 64QAM, respectively. Furthermore, a low complexity detection scheme based on orthogonal projection is formulated for the proposed scheme and, in comparison with the optimal maximum‐likelihood detector, is shown to result in a 56% and 95% reduction in computation complexity for the 16QAM and 64QAM versions of the proposed system, respectively.

A closed-form expression for performance optimization of subcarrier intensity QAM signals-based relay-added FSO systems with APD

This study characterizes the overall bit-error-rate (BER) performance optimization of avalanche photodiode (APD) receiver-based amplify-and-forward (AF) relay-added free-space optical (FSO) communication system. The system of interest uses subcarrier intensity quadrature amplitude modulation (QAM) signals and subjects to scintillation due to optical turbulence. A weak atmospheric turbulence (clear-air condition) scenario is considered, for which the received signal intensity fluctuation can be modeled as a log-normal random process. A closed-form expression of the overall BER is derived by taking into account the impact of atmospheric loss, turbulence strength, thermal-noise and shot-noise limited conditions. It can be inferred from the numerical results that using AF relay nodes can extend the transmission distance and minimize BER performance of FSO system significantly compared with the direct transmission. Moreover, the selection of APD’s gain values is indispensable to minimize the system’s BER performance. Hence, the designed system could achieve the minimal BER by selecting an optimal APD gain value appropriately. In addition, the optimal gain values of APD significantly depend on various conditions, such as noise temperature, link distance, and the number of relay nodes.

Receiver design combining iteration detection and ICI compensation for SEFDM

With the rapid development of wireless communication, the spectrum resource becomes rare, and research on utilization of limited spectrum resource becomes more popular, especially in fifth generation (5G) mobile communication system. Some efficient frequency division multiplexing systems, such as spectrally efficient frequency division multiplexing (SEFDM) system, can improve spectrum utilization by further compression of the distance between subcarriers with respect to orthogonal frequency division multiplexing (OFDM) carrier structure. This idea of further compressing bands will efficiently solve the problem of scarce spectrum resource in future. However, this kind of systems exist strong self-caused inter-carrier interference (ICI) due to non-orthogonal subcarriers employment, which poses a great challenge to the design of receiver. In this paper, a receiver designed with iterative ICI compensation (IIC) for SEFDM is proposed, which has excellent bit error rate (BER) performance and low complexity. Simulation results show that the BER performance of system under iterative ICI compensation receiver is almost same as traditional combining iterative detection and fixed sphere detection (ID-FSD) scheme with large bandwidth compression factor (BCF). But the complexity of the proposed method is lower than that of ID-FSD.

Polar coded space–time block coded spatial modulation based on Plotkin's construction for coded cooperative networks

A Plotkin-based polar coded space–time spatial modulation scheme is proposed and its bit error rate (BER) performance over quasi-static Rayleigh fading channel is evaluated. The exacerbated complexity in receiver design is ameliorated by employing a low complexity soft demapper for their proposed Plotkin-based polar coded scheme. As there is a natural split present in the design of the considered Plotkin's construction, therefore the authors effectively extended their proposed scheme to coded-cooperative scenarios. In any coded-cooperative communication, the relay node always plays a pivotal role in determining the BER performance of communication system. Therefore, a rational selection criterion for selecting the information bits at the relay node is presented. The authors have also devised nested polar coded-cooperative space–time spatial modulation (NPCCST-SM) scheme as a useful benchmark. Monte-Carlo simulated results revealed that their proposed coded-cooperative scheme has triumphed conventional NPCCST-SM scheme by a gain of 0.6–0.8 dB under identical conditions. Moreover, the proposed cooperative scheme outperforms its corresponding non-cooperative counterpart scheme by a gain of 1–1.2 dB under identical conditions.

BER Performance of PDM 4-QAM Optical Transmission System Considering the Effects of PMD and GVD Using Exact Probability Density Function

A noble theoretical approach is presented to evaluate the bit error rate (BER) performance of an optical polarization division multiplexed (PDM) 4-multilevel quadrature amplitude modulation (4-QAM) transmission system under the combined influence of polarization mode dispersion (PMD) and group velocity dispersion (GVD) in a single mode fiber (SMF). The analysis is carried out considering a coherent homodyne receiver. The exact probability density function (pdf) fluctuation due to PMD and GVD is evaluated from its moments using a Monte-Carlo simulation technique. Average BER is evaluated by averaging the conditional BER over the pdf of the random phase fluctuation. BER performance results are evaluated for different system parameters. It is found that PDM 4-QAM coherent homodyne system doubles the data rate but suffers more power penalty than the 4-QAM system. Results show that for a BER of 10^-9 at DGD of 0.5T and GVD value of 1700 ps/nm the PDM 4-QAM system needs 2.21 dB more power than 4-QAM systems giving the leverage of doubling the data rate.

Iterative Clipping Noise Elimination of Clipped and Filtered SCMA-OFDM System

Similar to conventional orthogonal frequency division multiplexing (OFDM) signal, the signals of sparse code multiple access combine with orthogonal frequency division multiplexing (SCMA-OFDM) existing the problem that its peak-to-average power ratio (PAPR) is unbearable high. In this paper, the clipping method is adopted to reduce the PAPR of the SCMA-OFDM signal. However, the clipping process brings extra noise to the SCMA-OFDM signal while the clipping noise is not taken into account in the message passing algorithm (MPA), which makes the MPA detection inaccurate and leads to a phenomenon that the decoding performance declines sharply with the increasing of ${{\text {E}}_{\text {b}}}{{/}}{{\text {N}}_{{0}}}$ . Moreover, due to the distortion of SCMA-OFDM signals caused by clipping process, the system bit error rate (BER) performance degrades obviously. To tackle the issues above, we analyze the random characteristics of the clipping noise for the MPA detection scheme. Then, an iterative clipping noise elimination scheme is proposed to restore the BER performance of clipped SCMA-OFDM system. Simulation results show that our method can remove the phenomenon that the BER performance declines sharply at the high ${{\text {E}}_{\text {b}}}{{/}}{{\text {N}}_{{0}}}$ region and the proposed iterative clipping noise elimination scheme restores the BER performance significantly.

User-relay Assignment based Antenna Selection Scheme in Multi-user Multi-relay AF Cooperative Communication Network

In this paper, the user-relay assignment based antenna selection scheme for multi-user cooperative network is proposed to improve the transmission bit rate and system performance. The low complexity suboptimal user-relay assignment algorithm is first proposed to simultaneously improve both the system performance and individual user’ performance in the multi-user amplify-and-forward (AF) cooperative user-relay network, where each user can fairly select its best relay according to the instantaneous channel state information (CSI). Based on the user-relay assignment scheme and space shift keying (SSK), we further present the antenna selection scheme to further enhance the system performance for the multi-user AF cooperative user-relay network. In order to minimize the system bit error rate (BER), three antenna selection criteria based on the maximum likelihood (ML) detection have been proposed. Numerical results and theoretical analysis show that the proposed schemes can effectively improve the average system sum rate, the outage probability of the worst user, and the system BER performance, compared with the other schemes.

A Novel Fractional Fourier Transform-Based ASK-OFDM System for Underwater Acoustic Communications

A key research area in wireless transmission is underwater communications. It has a vital role in applications such as underwater sensor networks (UWSNs) and disaster detection. The underwater channel is very unique as compared to other alternatives of transmission channels. It is characterized by path loss, multipath fading, Doppler spread and ambient noise. Thus, the bit error rate (BER) is increased to a large extent when compared to its counterpart of cellular communications. Acoustic signals are the current best solution for underwater communications. The use of electromagnetic or optical waves obviously entails a much higher data rate. However, they suffer from high attenuation, absorption or scattering. This paper proposes a novel fractional fast Fourier transform (FrFT)—orthogonal frequency division multiplexing (FrFT-OFDM) system for underwater acoustic (UWA) communication—which employs the amplitude shift keying (ASK) modulation technique (FrFT-ASK-OFDM). Specifically, ASK achieves a better bandwidth efficiency as compared to other commonly used modulation techniques, such as quadrature amplitude modulation (QAM) and phase shift keying (PSK). In particular, the system proposed in this article can achieve a very promising BER performance, and can reach higher data rates when compared to other systems proposed in the literature. The BER performance of the proposed system is evaluated numerically, and is compared to the corresponding M-ary QAM system in the UWA channel for the same channel conditions. Moreover, the performance of the proposed system is compared to the conventional fast Fourier transform (FFT)-OFDM (FFT-OFDM) system in the absence and presence of the effect of carrier frequency offset (CFO). Numerical results show that the proposed system outperforms the conventional FFT-based systems for UWA channels, even in channels dominated by CFO. Moreover, the spectral efficiency and data rate of the proposed system are approximately double the values of the corresponding conventional OFDM systems for the same parameters.

Performance Analysis of OFDM System Using Pilots, Coding Bounds and MAP Decoder for Next Generation Applications

In this paper, an integrated Orthogonal Frequency Division Multiplexing (OFDM) system is developed to improve Bit Error Rate (BER) performance of communication systems in order to meet the requirements of advanced communication systems like long term evaluation advanced (LTE –A). The proposed OFDM system consists of channel estimation using comb type pilot arrangement and convolution encoder with the best known Coding Bounds and Maximum A Posteriori (MAP) decoder. Using pilot symbols, the channel quality is estimated. The BER performance of OFDM system is improved using pilot carriers, channel estimation schemes and MAP decoder at the best known coding bounds. The system performance is analyzed with recursive systematic and non-systematic convolution codes, ML and MAP decoders. From the results, it is evident that the proposed OFDM system with channel estimation and MAP decoder at the best known coding bounds improves the system performance significantly.

Effect of Correlation on BER Performance of the FSO-MISO System With Repetition Coding Over Gamma–Gamma Turbulence

In free space optical (FSO) communication systems, atmospheric turbulence is the major cause of bit error rate (BER) performance degradation. The error performance of the system can be significantly improved with the help of spatial diversity by employing multiple transmit or receive apertures. However, correlation of channels under turbulence in the case of small separation between transmit apertures can substantially reduce the benefits of spatial diversity. Still, a thorough analysis of the system performance in terms of diversity order and coding gain for the FSO multiple-input single-output (MISO) system under turbulence influenced correlated channels has not been studied when the repetition coding is used to achieve improved BER performance. In this paper, we provide unique results of the BER performance analysis of the considered correlated FSO-MISO system over Gamma–Gamma distributed turbulence channel. Using the joint moment generating function of received signal-to-noise ratio (SNR), a novel generalized approximate BER expression is derived, followed by convergence test of the power series based BER expression using the Cauchy's ratio test. Then, an asymptotic analysis at high SNR is performed to obtain a novel closed-form expression for BER of FSO-MISO system. We also derive expressions for coding gain, diversity gain, and coding gain loss due to correlation in channels. Although the effect of correlation in channels on the BER performance of the system is analyzed under different scenarios, while it is observed that it does not affect the diversity order; it significantly degrades the coding gain of the considered system.

Effect of Pointing Error on BER Performance of a Multi-wavelength OCDMA FSO System with SIK Dual Detector Receiver

Abstract A novel analytical approach is presented to evaluate the bit error rate (BER) performance of a multi-wavelength optical code division multiple access (MW-OCDMA) free space optical (FSO) system using optical domain encoder and sequence inverse keying (SIK) balanced photodetector direct detection receiver taking the effect of pointing errors into considerations. The analysis is carried out to find the expression for the signal, multi-access interference (MAI) and crosstalk at the output of the SIK receiver in presence of pointing error. The BER performance results are evaluated for different values of standard deviation of pointing error, code length, number of simultaneous user and other system parameters. It is found that, MW-OCDMA system offers improved BER performance over single wavelength OCDMA FSO system. However, the performance of an MW-OCDMA system is degraded due to the effect of pointing error between the laser transmitter and optical receiver and the system suffers significant power penalty at a given BER of 10−9. The penalty is found to be 11.0 dB, 24.0 dB and 30 dB for jitter standard deviation of 1.3, 1.8 and 2.5 respectively when code length is 512 and number of user is 8 for number of wavelength 8. Further, the penalty can be greatly reduced by increasing the code length for a given number of user and number of wavelength.

Research on the system performance evaluation of minimum-shift keying in uplink ground-to-satellite with gamma–gamma distribution

Minimum-shift keying (MSK) has the advantages of constant envelope, continuous phase, and high spectral efficiency, and it is applied in radio communication and optical fiber communication. MSK modulation of coherent detection is proposed in the ground-to-satellite laser communication system; in addition, considering the inherent noise of uplink, such as intensity scintillation and beam wander, the communication performance of the MSK modulation system with coherent detection is studied in the uplink ground-to-satellite laser. Based on the gamma–gamma channel model, the closed form of bit error rate (BER) of MSK modulation with coherent detection is derived. In weak, medium, and strong turbulence, the BER performance of the MSK modulation system is simulated and analyzed. To meet the requirements of the ground-to-satellite coherent MSK system to optimize the parameters and configuration of the transmitter and receiver, the influence of the beam divergence angle, the zenith angle, the transmitter beam radius, and the receiver diameter are studied.

Experimental investigation of optimum beam size for FSO uplink

In this paper, the effect of transmitter beam size on the performance of free space optical (FSO) communication has been determined experimentally. Irradiance profile for varying turbulence strength is obtained using optical turbulence generating (OTG) chamber inside laboratory environment. Based on the results, an optimum beam size is investigated using the semi-analytical method. Moreover, the combined effects of atmospheric scintillation and beam wander induced pointing errors are considered in order to determine the optimum beam size that minimizes the bit error rate (BER) of the system for a fixed transmitter power and link length. The results show that the optimum beam size for FSO uplink depends upon Fried parameter and outer scale of the turbulence. Further, it is observed that the optimum beam size increases with the increase in zenith angle but has negligible effect with the increase in fade threshold level at low turbulence levels and has a marginal effect at high turbulence levels. Finally, the obtained outcome is useful for FSO system design and BER performance analysis.

Multi-Relay Communications in the Presence of Phase Noise and Carrier Frequency Offsets

Impairments such as time varying phase noise (PHN) and carrier frequency offset (CFO) result in loss of synchronization and poor performance of multi-relay communication systems. Joint estimation of these impairments is necessary in order to correctly decode the received signal at the destination. In this paper, we address spectrally efficient multi-relay transmission scenarios where all the relays simultaneously communicate with the destination. We propose an iterative pilot-aided algorithm based on the expectation conditional maximization for joint estimation of multipath channels, Wiener PHNs, and CFOs in decode-and-forward-based multi-relay orthogonal frequency division multiplexing systems. Next, a new expression of the hybrid Cramer–Rao lower bound (HCRB) for the multi-parameter estimation problem is derived. Finally, an iterative receiver based on an extended Kalman filter for joint data detection and PHN tracking is employed. Numerical results show that the proposed estimator outperforms existing algorithms and its mean square error performance is close to the derived HCRB at different signal-to-noise ratios for different PHN variances. In addition, the combined estimation algorithm and the iterative receiver can significantly improve average bit-error rate (BER) performance compared with existing algorithms. In addition, the BER performance of the proposed system is close to the ideal case of perfect channel impulse responses, PHNs, and CFOs estimation.

Bit error rate analysis of the scheduled TAS with MRC for CR-MIMO systems

In this paper, we investigate the bit error rate (BER) analysis of the scheduled transmit antenna selection (TAS) with maximal ratio combining (MRC) for the cognitive radio multiple-input multiple-output (CR-MIMO) systems. As a first step, this paper derives approximate probability density functions (PDFs) of the effective signal to noise ratio (SNR) of the proposed scheduled TAS with MRC in CR-MIMO systems. Next, the tight closed-form expressions of the BER for the M-ary QAM and M-ary PSK modulations are presented, respectively. Using asymptotic analysis, we approximate the BER for the scheduled system, and quantify the diversity order and SNR gain, respectively. Analytical results show that the diversity order of the scheduled system is the product of spatial diversity (SD) and multiuser diversity (MUD). Thus, BER performance of the proposed system is improved as the number of users increases by MUD regardless of modulation types. Also, the SNR gain is getting worse as the number of received antennas at the primary system increases regardless of modulation types.

Performance Investigation of Spatial Modulation Systems Under Non-Stationary Wideband High-Speed Train Channel Models

In this paper, the bit error rate (BER) performance of a new multiple-input-multiple-output technique, named spatial modulation (SM), is studied under a novel non-stationary wideband high-speed train (HST) channel model in different scenarios. Time-varying parameters obtained from measurement results are used to configure the channel model to make all results more realistic. A novel statistic property called the stationary interval in terms of the space-time correlation function is proposed to describe the channel model’s time-varying behavior. The accurate theoretical BER expression of SM systems is derived under the time-varying wideband HST channel model with the non-ideal channel estimation assumption. The simulation results demonstrate that the BER performance of SM systems shows a time-varying behavior due to the non-stationary property of the employed HST channel model. The system performance can maintain a relative stationary status within the specified stationary interval. It can also be observed that the BER performance of SM systems under the HST channel model is mainly affected by the correlation between sub-channels, inter-symbol-interference, Doppler shift, and channel estimation errors.

Combined peak-to-average power ratio reduction and physical layer security enhancement in optical orthogonal frequency division multiplexing visible-light communication systems

A physical encryption scheme for discrete Hartley transform (DHT) precoded orthogonal frequency division multiplexing (OFDM) visible-light communication (VLC) systems using frequency domain chaos scrambling is proposed. In the scheme, the chaos scrambling, which is generated by a modified logistic mapping, is utilized to enhance the physical layer of security, and the DHT precoding is employed to reduce of OFDM signal for OFDM-based VLC. The influence of chaos scrambling on peak-to-average power ratio (PAPR) and bit error rate (BER) of systems is studied. The experimental simulation results prove the efficiency of the proposed encryption method for DHT-precoded, OFDM-based VLC systems. Furthermore, the influence of the proposed encryption to the PAPR and BER of systems is evaluated. The experimental results show that the proposed security scheme can protect the DHT-precoded, OFDM-based VLC from eavesdroppers, while keeping the good BER performance of DHT-precoded systems. The BER performance of the encrypted and DHT-precoded system is almost the same as that of the conventional DHT-precoded system without encryption.

Analytical Evaluation of the Effect of Cross-Polarization-induced Crosstalk on the BER Performance of a PDM-QPSK Coherent Homodyne Optical Transmission System

Abstract An analytical approach is developed to find the effect of cross-polarization (XPol)-induced crosstalk on the bit error rate (BER) performance of a polarization division multiplex (PDM) quadrature phase shift keying (QPSK) optical transmission system with polarization diversity receiver. Analytical expression for the XPol-induced crosstalk and signal to crosstalk plus noise ratio (SCNR) are developed at the output of polarization diversity PDM-QPSK coherent optical homodyne receiver conditioned on a given value of mean misalignment angle. Considering Maxwellian distribution for the pdf of the misalignment angle, the average SCNR and average BER are derived. Results show that there is significant deterioration in the BER performance and power penalty due to XPol-induced crosstalk. Penalties in signal power are found to be 8.85 dB, 11.28 dB and 12.59 dB correspondingly for LO laser power of −10 dBm, −5 dBm and 0 dBm at a data rate of 100 Gbps, mean misalignment angle of 7.5 degree and BER of 10−9 compared to the signal power without crosstalk.

BER Performance of Spatial Modulation Systems Under 3-D V2V MIMO Channel Models

In this paper, the bit error rate (BER) performance of spatial modulation (SM) systems under a novel 3-D vehicle-to-vehicle (V2V) multiple-input multiple-output (MIMO) channel model is investigated both theoretically and by simulations. The impact of vehicle traffic density, Doppler effect, and 3-D and 2-D V2V MIMO channel models on the BER performance are thoroughly investigated. Simulation results show that the performance of SM is mainly affected by the spatial correlation of the underlying channel model. Compared with other MIMO technologies, the SM system can offer a better tradeoff between spectral efficiency and system complexity.