Improved Bit Error Rate Research Articles

A Two-Hop mmWave MIMO NR-Relay Nodes to Enhance the Average System Throughput and BER in Outdoor-to-Indoor Environments.

Millimeter-Wave (mmWave) bands are receiving enormous attention in 5G mobile communications, due to the capability to provide a multi-gigabit transmission rate. In this paper, a two-hop architecture for 5G communications with the capacity to support high end-to-end performance due to the use of Relay Nodes (RNs) in mmWave-bands is presented. One of the novelties of the paper is the implementation of Amplify-and-Forward (A&F) and Decode-and-Forward (D&F) RNs along with a mmWave-band transceiver chain (Tx/Rx). In addition, two approaches for channel estimation were implemented at the D&F RN for decoding the backhaul link. One of them assumes complete knowledge of the channel (PCE), and the other one performs the channel estimation through Least Square (LS) estimator. A large number of simulations, using MATLAB and Simulink software, were performed to verify the potential benefits of the proposal two-hop 5G architecture in an outdoor-to-indoor scenario. The main novelty in performing these simulations is the use of signals with 5G features, as DL-SCH transport channel coding, PDSCH generation, and SS Burst generation, which is another of the main contributions of the paper. On the other hand, mmWave transmitter and receiver chains were designed and implemented with off-the shelf components. The simulations show that the two-hop network substantially improves the Key Performance Indicators (KPIs), Bit Error Rate (BER), and Throughput, in the communications between the logical 5G Radio Node (gNodeB), and the New Radio User Equipment (NR-UE). For example, a throughput improvement of 22 Mbps is obtained when a 4 × 4 × 2 MIMO D&F with LS architecture is used versus a SISO D&F with PCE architecture for Signal-to-Noise Ratio (SNR) = 20 dB and 64-QAM signal. This improvement reaches 96 Mbps if a 256-QAM signal is considered. The improvement in BER is 11 dB and 10.5 dB, respectively, for both cases. This work also shows that the obtained results with D&F RNs are better than with A&F RNs. For example, an improvement of 17 Mbps in the use of SISO D&F with LS vs. SISO A&F, for the 64-QAM signal is obtained. Besides, this paper constitutes a first step to the implementation of a mmWave MIMO 5G cooperative network platform.

BER of Massive MIMO in time-variant channels using multiplexed, superimposed and hybrid channel estimation techniques

Massive MIMO (M-MIMO) is one of the most promising technologies towards fifth generation (5G) wireless systems. M-MIMO use a large number of antennas at the base station (BS) serving multiple user terminals (UTs). Therefore, it presents an exceptional performance in terms of the ergodic capacity and bit error rate (BER) using simpler linear detectors when time-invariant channels (TIC) and perfect channel state information (CSI) are considered. However, impairments introduced by the time-variant channel (TVC) and the imperfect channel estimation limit the M-MIMO performance. In this work, the impairments introduced by the multiplexed pilot estimation (MPE), superimposed pilot estimation (SPE), and hybrid pilot estimation (HPE), using the minimum-mean-square error (MMSE) estimator are analyzed for M-MIMO in TVCs. Furthermore, the system performance is evaluated in terms of the BER for the zero-forcing (ZF) detector. Closed-form expressions and simple lower bounds are derived. The results show that the average BER in TVCs is far from the average BER obtained for TICs. Moreover, MPE and HPE are more susceptible to the impairments of TVCs, and even increasing a considerable number of BS antennas, the BER improvement is negligible in some time-slots. Finally, the BER using SPE outperforms the other estimation techniques.

Neuro‐fuzzy and fuzzy schemes for cooperative communication in wireless sensor network: a military battlefield scenario

In the military battlefield, maintaining high survivability of energy constraint wireless sensor network (WSN) when some nodes are destroyed by the foe troops is one of the prominent issues for the researchers. This study proposes the fuzzy and neuro-fuzzy based relay selection schemes for cooperative WSN which reduce the bit error rate (BER) while improving the network lifetime. Meanwhile, the proposed model maintains the uninterrupted communication between military nodes in a warfare situation. The proposed proposed strategies are compared with the maximum residual energy-based relay selection (MRERS), minimum energy consumption-based relay selection (MECRS), and random relay selection (RRS) strategies. The performance of the proposed and existing strategies is evaluated on the basis of BER, network lifetime, number of dead nodes, and average energy of nodes in the network. The simulation results demonstrate that proposed schemes has 13.19–19.28% improvement in BER than the existing strategies. Moreover, 76.00–90.88% network lifetime improves when compared with the MECRS and RRS strategies. However, 6–7.76% is less than MRERS strategy. Furthermore, the results show that network survivability and average network energy is also better when the number of dead nodes in the network increases.

Optimal Detection Interval for Absorbing Receivers in Molecular Communication Systems With Interference

We consider a molecular communication system comprised of a transmitter, an absorbing receiver, and an interference source. Assuming amplitude modulation, we analyze the dependence of the bit error rate (BER) on the detection interval, which is the time within one transmission symbol interval during which the receiver is active to absorb and detect the number of information-carrying molecules. We then propose efficient algorithms to determine the optimal detection interval that minimizes the BER of the molecular communication system assuming no inter-symbol interference (ISI). Simulation and numerical evaluations are provided to highlight further insights into the optimal results. For example, we demonstrate that the optimal detection interval can be very small compared to the transmission symbol interval. Moreover, our numerical results show that significant BER improvements are achieved by using the optimal detection interval for systems without and with ISI.

Enhanced cognitive demodulation with artificial intelligence

The low-cost ‘THz Torch’ wireless link technology is still in its infancy. Until very recently, inherent limitations with available hardware has resulted in a modest operational figure of merit performance (Range times Bit Rate). However, a breakthrough was reported here by the authors, with the introduction of ‘Cognitive Demodulation’. This bypassed the thermal time constant constraints normally associated with both the thermal emitter and sensor; allowing step-change increases in both Range and Bit Rate with direct electronic modulation. This paper concentrates on advancements to the bit error rate (BER) performance. Here, separate techniques are introduced to the demodulation software that, when combined, result in enhanced Cognitive Demodulation. A factor of more than 100 improvement in BER was demonstrated within the laboratory and approximately a 60-fold improvement in a non-laboratory environment; both at the maximum Range and Bit Rate of 2 m and 125 bps, respectively, demonstrated recently. Moreover, demodulation speed is increased by almost a factor of 10,000; allowing for real-time demodulation while easing future computational hardware requirements. In addition to these software advancements, the paper demonstrates important improvements in hardware that has brought the technology out of the laboratory, with field trials being performed within an office corridor.

Hybrid mapped optical‐OFDM using non‐linear companding technique for indoor visible light communication application

In this study, the authors have developed an analytical model for reducing the peak-to-average-power ratio (PAPR) using non-linear companding transform (NCT) based on inverse hyperbolic sine function. As a consequence of non-linear transform, this study compensates the system bit error rate (BER) degradation with the help of an error efficient hybrid modulation. By means of an inflexion point and companding parameter, more design flexibility is achieved; as a result, a trade-off between PAPR and BER has reasonably been more precise. To the best of the authors’ awareness, no findings have yet been reported on the performance evaluation of the optical orthogonal frequency division multiplexing (OOFDM) system using a hybrid modulation technique. To find out the advantages of hybrid modulation with NCT, the authors inspect the nature of PAPR reduction, and BER improvement through numerical simulations. The numerical BER results exhibit roughly 3 dBm decay in the power efficiency of hybrid modulation with NCT over discrete Fourier transform (DFT) precoding technique. On the other hand, the NCT technique with hybrid modulation has 6 dB less PAPR than the DFT precoding technique.

A Transmit Antenna Selection based Energy-Harvesting MIMO Cooperative Communication System

This paper considers a cooperative wireless system with multiple antennas at the source. A multi-antenna relay equipped with a power splitter is introduced between the source and destination. It utilizes the energy from the received signal for amplification and transmit it to the destination. The linear precoding techniques such as zero forcing (ZF) and minimum mean square error (MMSE) are used to reduce the interference. We compare two antenna selection techniques viz. norm-based antenna selection (NBAS) and received signal-to-noise ratio (SNR) based antenna selection (RSBAS). It is analyzed that the NBAS and RSBAS antenna selection techniques offer improvement of 20% and 37% over random antenna selection technique. However, the antenna selection technique NBAS offers improvement in system bit error rate (BER) performance by 14% as compared to RSBAS at SNR value of 0 dB. We presented a scenario where the energy harvesting at relay node offers saving the battery power at the user node. Hence, the presented analysis is applicable in communication with remote sensors. This paper also analyses that the BER is improved with the reduction in the distance between source and relay for the given value of energy harvesting efficiency.

Evaluation of the Performance of a Reed Solomon Coded STBC MIMO System Concatenated with MPSK and MQAM in Different Channels

Background & Objective: Wireless technologies like Wi-Fi, WiMAX, and LTE are using Multiple Input, Multiple Output (MIMO) communications that play an important role in achieving high data rates. Bit Error Rate (BER) is one of the most important performance parameters in multipath channels for data communication. Methods: This research proposes a new method based on Reed Solomon (RS) coding to improve the efficacy of a Space-Time Block Coded (STBC) MIMO System concatenated with M-ary Phase Shift Keying (MPSK) and M-ary Quadrature Amplitude Modulation (MQAM) in reducing BER in Rayleigh, Rician and Nakagami channels. It is based on the error detection and correction properties intrinsic to RS coding processes. Binary data is coded using an RS encoder and the modulated signal STBC encoded and transmitted through Rayleigh, Rician and Nakagami channels. Signals received by two antennas are STBC decoded, demodulated, RS decoded and tested for BER. Results & Conclusion: Results show lower BER rates for RS Coded systems as compared for uncoded systems in all three channels. In addition, it was found that reduction in BER is greater for high Signal to Noise Ratio (SNR) but deteriorates for low SNR. Furthermore, this research observed that RS coding gives 63% to 98% improvement in BER in the Rayleigh as compared to Rician and Nakagami channels. This research has been able to successfully incorporate the BER reduction of STBC MIMO to further enhance the efficacy of an STBC MIMO system.

Efficient Information Transmission Using Smart OFDM for IoT Applications

Orthogonal frequency-division multiplexing (OFDM) is one of the most widely adopted modulation schemes because it offers several desirable features, such as spectral efficiency and low complexity implementation. Moreover, it is highly suitable for adaptive implementation. Nevertheless, OFDM does not have any special immunity against multipath fading as compared to single-carrier systems. Therefore, we propose in this article a new OFDM configuration, denoted as OFDM-smart (OFDM-S), where superposition modulation is used to introduce transmit diversity to reduce the bit error rate (BER) while maintaining the spectral efficiency and bit rate fixed. The proposed scheme is based on clustering specific subcarriers that can cooperate by sharing their transmission resources. The cooperation is performed such that all subcarriers transmit their data jointly using all the subcarriers within their cluster. The system performance is derived in terms of BER performance over Nakagami- $m$ frequency-selective fading channels where efficient expressions are presented in terms of a single finite integral, and closed-form expressions are derived for the asymptotic BER. The obtained analytical results corroborated by simulation show that the OFDM-S can provide substantial BER improvement over conventional OFDM, due to the transmit diversity.

Hollow top‐hat DOE shaping method applied in space uplink chaotic optical communication for BER improvement

As the traditional refractive optical telescope blocks part of the transmission beam, the transmission efficiency in space chaotic optical communication is needed to be improved. A couple of diffractive optical elements (DOEs) are introduced into the optical subsystem at transmitting terminal to avoid the obscuration through shaping transmission beam into hollow top-hat beam (HTB). The simulation results indicate that shaping transmission beam into HTB is more efficient than traditional hollow Gaussian beam in bit error rate (BER) improvement of space chaotic optical communication. The results are significant for the optimisation design of space uplink chaotic optical communication system.

Comparison of Different Precoding Techniques for Unbalanced Impairments Compensation in Short-Reach DMT Transmission Systems

Channel independent precoding technique has been widely used in optical discrete multi-tone (DMT) transmission systems to compensate unbalanced impairments induced by bandwidth limitations and imperfect frequency responses of electrical/optical devices and various interferences. However, the comparison of different precoding techniques in terms of peak-to-average power ratio (PAPR) reduction, nonlinear distortion tolerance, implementation complexity, and bit error rate (BER) improvements has not been fully studied. In this article, we comparatively investigate seven most commonly used precoding techniques, i.e., discrete Fourier transform (DFT), orthogonal circulant matrix transform (OCT), constant amplitude zero autocorrelation sequence-based matrix transform (CAZACT), Zadoff-Chu matrix transform (ZCT), discrete cosine transform (DCT), discrete Hartley transform (DHT), and Walsh-Hadamard transform (WHT), through both numerical simulations and offline experiments. Simulations show that the ZCT can achieve the best PAPR reduction, and the OCT cannot reduce the PAPR. Besides, DFT, CAZACT, ZCT, DCT, and DHT precoded DMT signals have superior error vector magnitude performance after passing through nonlinear models. And the corresponding precoded QPSK-DMT signals have better BER performance than both OCT/WHT precoded and conventional ones in the distortion-limited scenarios. However, the precoded 16/64QAM-DMT signals, excluding OCT precoded one, are more sensitive to nonlinear distortions and provide minor BER improvement or even may degrade the BER performance. Complexity analysis exhibits the WHT precoding does not require multiplications and therefore has the lowest implementation complexity. In the inter-symbol interference-limited case, OCT precoding can still achieve a good signal-to-noise ratio (SNR) balance and provide the best BER performance. A simple timing synchronization point adjustment (TSPA) method is employed to enhance SNR balance. Simulated and experimental results exhibit that similar BER performance can be achieved by using these precoding techniques together with TSPA in noise-limited scenarios. Considering the implementation complexity, WHT precoding may be a good option to compensate unbalanced impairments in the short-reach DMT transmission system.

Wireless link pairing toward secured 6G networks.

Hybrid wireless networks are foreseen to play a major role in the visioning and planning of the sixth generation (6G) network. Most of the 6G applications are human-centric, and thus high security and privacy are key features. Recently, physical layer (PHY) security has become an emerging area of research. This work introduces a novel, to the best of our knowledge, PHY security approach called wireless link pairing (WiLP). In WiLP, signals received from both air interfaces in a hybrid radio frequency and optical network are required for successful signal reconstruction and processing at the receiver. The transmitted packets based on the IEEE 802.11 standards are redesigned, and improvements in performance are validated via simulations and experimental measurements using software-defined radio platforms. The obtained results demonstrate improvements in bit-error rate (BER) and the secrecy capacity for multiple modulation and coding schemes.

Bit error probability analysis of IR-UWB ED-OOK system using cooperative dual-hop DTF strategy

The Bit Error Rate (BER) of a single user cooperative Impulse Radio (IR)-Ultrawideband (UWB) communication system employing Energy Detector (ED) receiver with On-Off Keying (OOK) in IEEE 802.15.4a UWB multipath environment is investigated in this paper. Analytical evaluation based on Energy detection principle is performed to derive approximate BER Expressions for various diversity combining cases, namely optimum combining, linear combining and selective combining using cooperative dual-hop Detect and Forward (DTF) relay protocol in presence and absence of Inter-symbol interference (ISI). Numerical results reveal that there is a significant improvement in BER, with increase in number of relay diversity paths and decrease in number of frames Nf. The accuracy and perfection in approximation used in investigation of BER is confirmed with the validation of the analytical BER expressions with that of the simulation results. The analytical and simulation results confirm that among the diversity combining schemes, the performance of optimum combining is better compared with linear combining, which in turn performs better than selective combining.

Capacity enhancement of an indoor visible light communication system using cooperative transmission

This study investigates cooperative inter-lighting interference cancellation (C-ILIC) in indoor multiple-input single-output (MISO) visible light communication (VLC) to overcome co-channel interference (CCI) and provide connectivity, even if there is link blockage. C-ILIC exhibits great improvement in the average bit error rate (BER) performance and the transmission capacity. VLC plays an important role in handling the increasing data traffic in indoor environments. When the transmitters simultaneously send unique data over the same frequency resources, and the receiver obtains the different signals, CCI occurs because the signals interfere with each other. C-ILIC employs cooperative transmission to forward a composite data, which consists of the high received power data and the low received power data, and ILIC to decode the high received power data and reduce CCI in the low received power data before decoding. Through computer simulations, the BER performance of C-ILIC overcomes the conventional ILIC in any position because the receiver power ratio always complies with the threshold. Despite the BER performance deteriorating in the presence of link blockage, the data connection is guaranteed when the obstruction is not severe. Therefore, C-ILIC can provide reliable communication and full connectivity within a room.

Channel Estimation in OFDM System using Compressive Sensing Framework: A Review

Paper addresses Channel Estimation by means of Compressive Sensing (CS). Here system under consideration is OFDM. Paper reviews the emerging techniques of pilot design and allocation schemes. With the said pilot allocation techniques performance improvement in Mean square Error (MSE) and Bit Error Rate (BER) is achieved. Spectral efficiency can be considerably improved with channel estimation exploiting compressive sensing. Prominent algorithms are designed to attain better estimation accuracy even with reduction in pilot subcarrier figure. Comparatively simple CS structures with least computation complexity also reviewed in the projected paper.

On the performance of adaptive hybrid MQAM-MPPM scheme over Nakagami and log-normal dynamic visible light communication channels.

In this paper, we introduce the idea of using adaptive hybrid modulation techniques to overcome channel fading effects on visible light communication (VLC) systems. A hybrid $ M $M-ary quadrature-amplitude modulation ($ M{\rm QAM} $MQAM) and multipulse pulse-position modulation (MPPM) technique is considered due to its ability to make gradual changes in spectral efficiency to cope with channel effects. First, the Zemax optics studio simulator is used to simulate dynamic VLC channels. The results of Zemax show that Nakagami and log-normal distributions give the best fitting for simulation results. The performance of $ M{\rm QAM} $MQAM-MPPM is analytically investigated for both Nakagami and log-normal channels, where we obtain closed-form expressions for the average bit-error rate (BER). The optimization problem of evaluating the hybrid modulation technique settings that lead to the highest spectral efficiency under a specific channel status and constraint of outage probability is formulated and solved using an exhaustive search. Our results reveal that the adaptive hybrid scheme improves system spectral efficiency compared to ordinary QAM and MPPM schemes. Our results reveal that the adaptive hybrid scheme improves system spectral efficiency compared to ordinary QAM and MPPM schemes. Specifically, at low average transmitted power, $ - 32\;{\rm dBm} $-32dBm, the adaptive hybrid scheme shows 280% improvement in spectral efficiency compared to adaptive versions of ordinary schemes. At higher power, $ - 20\;{\rm dBm} $-20dBm, 6.5% and 725% improvement are obtained compared to ordinary QAM and ordinary MPPM, respectively. Also, the adaptive hybrid scheme shows great improvement in average BER and outage probability compared to ordinary schemes. The hybrid scheme shows 28%, 34%, and 38% improvement, respectively, for $ m = 1,2,3 $m=1,2,3 for Nakagami channels at $ {\rm BER}{ = 10^{ - 3}} $BER=10-3. Also, the outage probability of hybrid schemes of $ {\rm BER}{ = 10^{ - 3}} $BER=10-3 shows 30% and 14% better performance than ordinary $ M{\rm QAM} $MQAM and MPPM schemes, respectively.

Nonlinear Channel Equalization Using Wavelet Neural Network Trained Using PSO

Wireless communication channels are increasingly being pushed into the paradigm nonlinearity and inter symbol interference (ISI) because of demand for high speed data through portable and power efficient hand held devices. ISI and nonlinearity cause severe degradation in received signal resulting in poor quality of service. In this paper, channel equalizers are designed for mitigating channel nonlinearity and ISI. We propose an improved method of training wavelet neural network-based equalizer using particle swarm optimization (PSO). Our approach consists of optimizing the translation, dilation and other weights of hidden layer to achieve improvement in bit error rate (BER) performance. Superior performance of the proposed training algorithm is established by comparing the BER with established equalization schemes in literature.

Jamming in Free Space Optical Systems: Mitigation and Performance Evaluation

In this paper, the effect of jamming in free space optical (FSO) link, is evaluated by deriving closed-form expressions of the bit error rate (BER) and outage probability (OP) for single-input single-output (SISO) and multiple-input single-output (MISO) FSO systems. The effects of partial-band jamming and broadband jamming over the error performance of the considered FSO systems are also analyzed. The jammer behaves as a random noise source, following the negative exponential distribution-due to the atmospheric turbulence. Therefore, in the presence of jammer, the error performance of FSO systems is governed by the additive negative exponential noise. It is shown by a rigorous analysis that a MISO FSO system can significantly mitigate the effect of jamming. Specifically, we consider a $2\times 1$ FSO system for analysis, and demonstrate the improvement in BER and OP performance an FSO system can gain by using an additional spatial dimension, in the presence of a random jammer. The mitigation of jamming, due to implementation of arbitrary transmit apertures, is also verified through simulation results; which lies in complete agreement with the analytical results. Also, the error performance under the jamming effect is studied numerically over the Gamma-Gamma fading channel incorporated with pointing error effect.

Optical MIMO-OFDM With Fully Generalized Index-Spatial LED Modulation

In this letter, we propose a novel, fully generalized index-spatial (FGIS) light emitting diode (LED) modulation scheme for the optical MIMO-orthogonal frequency division multiplexing (OFDM) system. The fully generalized index-spatial (FGIS) is a spectrally efficient (SE) visible light communication (VLC) modulation scheme in which the LED indices are exploited in an innovative way to address, not only the OFDM signal time/frequency domain shaping problem but also to provide an additional spatial modulation (SM) domain. Compared to recent OFDM-LED index modulation schemes, FGIS achieves higher SE with lower number of LEDs. The simulation results surpass the proposed FGIS in giving superior improvement in both bit error rate (BER) and achievable rate ( $R$ ) compared with the state-of-the-art OFDM-LED index modulation schemes.

Multiple TAS-OSTBC in MIMO with Outer BCH Concatenation under Nakagami-m Fading

Transmit Antenna Selection (TAS) technique with Orthogonal Space Time Block Code (OSTBC) addresses the problem of hardware complexity in multiple antenna systems and improves Bit Error Rate (BER) significantly by using various antenna selection algorithms. TAS technique is not able to provide the coding gain. To achieve the coding gain benefits with improvement in BER, it is necessary to concatenate TAS system with an outer code. In literature, it is observed that the concatenation of Forward Error Correction (FEC) codes and Space Time Block Code (STBC) for MIMO systems provides the high coding gain with improved BER. In this paper, a multiple TAS-OSTBC system is proposed with concatenation of channel coding techniques such as BCH and TURBO. The proposed system is concatenated with BCH as outer code in series with TURBO as inner code. This combination provides the capacity benefits of TAS-OSTBC system with improved coding gain. The channel is assumed to be faded by Nakagami- m fading. It is observed that for multiple TAS-OSTBC system this new concatenation of BCH-TURBO code gives improvement of 5 dB at 10-6 as compared to concatenation of TURBO code at m =0.5 for Nakagami- m fading parameter.