BER Reduction Research Articles

Self-measurement and calibration of amplitude-frequency response for coherent optical transmitters with limited DAC resolution

Precise measurement and calibration of the amplitude-frequency response (AFR) of coherent optical transmitters (Tx) are paramount for generating high-quality signals, especially when the transmitter has insufficient bandwidth. The previously proposed self-measurement and calibration (SMC) method based on multi-tone signals (MTS) is cost-effective, fast, and convenient. However, this method exhibits a compromised AFR measurement precision in high-frequency regions, especially when the digital-to-analog converters (DAC) of the Tx have a limited resolution. To solve this problem, we optimize the amplitudes and phases of the MTS by pre-emphasis and the sequential quadratic programming (SQP) algorithm to improve the accuracy in the high-frequency region. Numerical simulations show a notable reduction in AFR measurement error, from about 4 dB to 0.8 dB, when employing a DAC with a four-bit resolution. Additionally, experiments utilizing a 22 GHz 3-dB bandwidth transmitter to generate 61 GBaud dual-polarization 16QAM signals demonstrate a 60% BER reduction. The proposed SMC method is attractive for high-baud rate systems employing Tx with limited bandwidth and DAC resolution.

Improving FSO Link Performance using PolSK Modulation

Free Space Optical (FSO) communication systems are based on the use of infrared light to transmit information at high speed through the atmospheric channel. Their performance is therefore affected by the characteristics of the atmospheric channel. One of the most widely used methods of compensating for the effects of atmospheric factors is modulation.The main aim of this research is to demonstrate the improvement in FSO link performance using PolSK modulation in a subtropical environment such as Cˆote d’Ivoire. The performance indicators considered are bit error rate, channel capacity, outage probability and energy efficiency. The mathematical expression of the evolution of each of these indicators as a function of the atmospheric parameters of our environment was determined using the gamma-gamma model. A numerical evaluation of the results obtained was carried out using Matlab software. The results show that PolSK modulation offers the best results in terms of BER reduction, with a BER of the order of 10-11 for an SNR of 50dB, compared with BERs of 10-4 and 10-2 for BPSK and OOK modulations respectively. We obtain a probability of interruption of the order of 10-3 for PolSK modulation compared with 10-2 for BPSK modulation and 10-1 for OOK modulation. As for the channel capacity, we obtain the same value (4:1458bit/s) for PolSK and BPSK modulation compared with 3:8181bit/s for OOK modulation. BPSK modulation, on the other hand, stands out for its excellent energy efficiency.

Modified Kramers-Kronig receiver based on memory polynomial compensation for photonics-assisted millimeter-wave communications.

Photonics-assisted millimeter-wave (MMW) wireless communications are advancing rapidly driven by the escalating congestion in the lower-band spectrum and the growing demand for higher data rates. Concurrently, Kramers-Kronig (KK) receivers provide an economical solution ideally suited for cost-sensitive deployment and application. However, the conventional KK receiver is subject to performance degradation due to the nonlinearity and memory effects introduced by practical electronic devices. In this work, the performance degradation of the conventional KK receiver is investigated and quantitatively simulated, showing that the KK receiver exhibits greater sensitivity to nonlinearity and memory effects compared to the conventional coherent receiver. To enhance the performance of KK receivers deployed in MMW communication systems, we propose a modified KK receiver employing memory polynomial compensation, namely MP-KK receiver, capable of effectively compensating memory effects whilst simultaneously addressing nonlinearity. Crucially, the memory polynomial model is employed prior to the KK algorithm to prevent further signal degradation caused by the nonlinear operator in the KK algorithm in the scenario of photonics-assisted MMW wireless communication based on the KK receiver. For verification, we present a 95 GHz W-band MMW wireless transmission demonstration with 20 Gb/s QPSK and 40 Gb/s 16-QAM signals. The experimental results indicate that the MP-KK receiver can achieve more than 3.5 dB improvement in EVM and 71.25% reduction in BER compared to the conventional approaches.

Design and Performance Analysis of the Dynamic Reduction of Intrinsic Interference Suppression and BER using QAM-based FBMC for MU-MIMO Communications

The present research work is focused on the study of co-channel interface with its minimization techniques without influencing its performance, in turn, which is desired to achieve the minimized complexity of Quadrature Amplitude Modulation (QAM)-based Filter Bank Multi-Carrier (FBMC) to minimize the interference and increase the spectral features with consideration of intrinsic features extractions for the ML (Maximum Likelihood) synthesis systems. The valid measures are given various concerns under consideration, to start with the consideration of the evaluation of the Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFD performance metrics along with the FBMC/QAM in signal transmission in a dedicated fading channel for the evaluation of the modulation order and BER as a required trade-off for quality assessments. From the results, it can be noted that the proposed FBMC QAM has performed better when compared with conventional FBMC systems. The present research also includes considering and calculating the efficiency of nonlinear channels with the Multi-User Multiple Input Multiple Output (MU-MIMO) and FBMC/QAM techniques. In continuation, the obtained results are dominating significantly to access the possible solution to meet the efficiency of the proposed system. In the next part of the research, it is considered with implementation of the sub-detector during the downlink of the system with the technique of threshold-driven strategy for better accuracy and minimization of the complexity in terms of ML detection in terms of order of its modulation. The calculations of the proposed technique with better BER are done on the recent MATLAB platform with its simulation demonstration for its detailed observation.

Approximate BER Performance of LoRa Modulation With Heavy Multipath Interference

This letter proposes a method to approximate LoRa performance over heavy multipath channels. Firstly, the multipath time delay and LoRa signal duration are combined to analyze the path overlapping interference quantitatively. Then simple BER approximations in coherent and non-coherent detections are derived with Gaussian Q-function and algebraic formulas. With the heavy multipath channel model in 3GPP to mimic the realistic indoor industrial scenarios, the approximate expressions are verified by Monte Carlo simulations. Moreover, performance comparison results show that a high spreading factor leads to severe multipath overlap and may result in BER reduction.

Joint Spatio-Temporal Precoding for Practical Non-Stationary Wireless Channels

The high mobility, density and multi-path evident in modern wireless systems makes the channel highly non-stationary. This causes temporal variation in the channel distribution that leads to the existence of time-varying joint interference across multiple degrees of freedom (DoF, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e.g</i> ., users, antennas, frequency and symbols), which renders conventional precoding sub-optimal in practice. In this work, we derive a High-Order Generalization of Mercer’s Theorem (HOGMT), which decomposes the multi-user non-stationary channel into two (dual) sets of jointly orthogonal subchannels (eigenfunctions), that result in the other set when one set is transmitted through the channel. This duality and joint orthogonality of eigenfuntions ensure transmission over independently flat-fading subchannels. Consequently, transmitting these eigenfunctions with optimally derived coefficients eventually mitigates any interference across its degrees of freedoms and forms the foundation of the proposed joint spatio-temporal precoding. The transferred dual eigenfuntions and coefficients directly reconstruct the data symbols at the receiver upon demodulation, thereby significantly reducing its computational burden, by alleviating the need for any complementary post-coding. Additionally, the eigenfunctions decomposed from the time-frequency delay-Doppler channel kernel are paramount to extracting the second-order channel statistics, and therefore completely characterize the underlying channel. We evaluate this using a realistic non-stationary channel framework built in Matlab and show that our precoding achieves ⩾4 orders of reduction in BER at SNR⩾15dB in OFDM systems for higher-order modulations and less complexity compared to the state-of-the-art precoding.

Error Correction Using Hybrid Coding Algorithm for BER Reduction in MIMO-OFDM

Error Correction Using Hybrid Coding Algorithm for BER Reduction in MIMO-OFDM

Genetic Algorithm Based BER Aware Channel Selection Using Break Point Technique For Next Generation Milli-Meter (mm) Wave Communication Systems

Due to exponential increase in communication speed when shifting from 4th Generation 4G to 5G networks, there is a requirement to redesign equipment to support spectrum ranges from 450 MHz to 52.6 GHz, which makes them operate at very high speeds. In order to maintain good communication performance while operating at this bandwidth, millimeter waves (mmWaves) are used. As communication radius increases, the BER also increases linearly, which limits range of these equipment’s, thereby incurring higher deployment costs. In order to reduce these costs, and design mmWave communication components to work for larger areas, this text proposes a Genetic optimization architecture that uses intelligent channel modelling and selection. The architecture is designed in order to reduce BER during communication when threshold breakpoint occurs, thereby improving communication speed, and overall throughput. It exploits long-ranged loopback communications in order to automatically tune internal transmission parameters for supporting larger areas with minimum packet loss. The underlying model is tested on various channel types, different network scenarios, and under different noise conditions. It is observed that the proposed model outperforms original mmWave communication models in terms of BER reduction by 8% and in terms of communication coverage by 6%, thereby making it applicable for wider geographical areas. This results in reduced deployment costs, and better communication quality of service (QoS), thereby assisting in better network design.

Analysis of PAPR and BER Reduction in MIMO-OFDM using Hybrid Moth Flame-Improved Firefly Algorithm

Analysis of PAPR and BER Reduction in MIMO-OFDM using Hybrid Moth Flame-Improved Firefly Algorithm

2D Constellation Distortion for Subduing Equalization Noise in Bandwidth- Limited IMDD Systems

Bandwidth-limited IMDD systems suffer from the noise boosted by the strong equalization at the receiver. This letter proposes a multiplication-free approach that reduces the impacts of the equalizer-enhanced colored noise through time-interleaving the received symbols and distorting the two-dimensional (2D) constellation such that the noise correlation is subdued. The 2D distortion map is predefined and retrieved from a look-up table. The proposed 2D constellation distortion is evaluated after the linear feed-forward equalizer and Volterra nonlinear equalizer. Experimental results show a BER reduction of 40% when the 2D constellation distortion is employed after the equalizer for the 135 Gbaud PAM4 and 110 Gbaud PAM6 signals. Owing to the proposed approach, we transmit a net data rate of 250 Gbps/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> PAM4 and PAM6 in the O-band over 2 km of SSMF at a BER of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.8\times 10^{-3}$ </tex-math></inline-formula> below the 6.7% overhead HD-FEC using a 47 GHz SiP modulator, linear equalization, and the proposed 2D distortion.

A Performance Analysis of Wavelet based LTE-OFDM with Multi-equalizers

A rapid change in usage of mobile data and mobile based applications such as online gaming, mobile TV etc. motivates the mobile wireless communication system to work on new emerging trends Long Term Evolution (LTE). LTE-4G architecture provides an optimized packet based radio access technology. The basic signal format of LTE is Orthogonal Frequency Division Multiplexing (OFDM) Modulation. This modulation scheme satisfies the spectrum flexibility requirement in LTE. LTE-MIMO-OFDM with IFFT and FFT transform introduced to provide the cost-effective solution for very wide carriers with high PAPR. Inter-symbol Interference (ISI) and inter carrier interference (ICI) are predominant factors which exist in the wireless communication channel. Existing methods of ISI and ICI reduction to improve signal quality have been achieved using conventional OFDM techniques. However, a better modulation scheme is required to achieve high data rate, low latency and flexible bandwidth deployment. This paper has proposed a Wavelet based LTE-MIMO-OFDM modulation scheme with multi equalizer that improves the performance of system by reducing PAPR and BER in MCM. Experimental results show the performance of this scheme and the results is compared with existing MMSE and Multi equalizer MMSE and achieves a flexible spectral efficiency with reduction of PAPR and BER.

5G Massive Multiple Input and Multiple Output System with Maximum Spectral Performance

Massive MIMO is the presently maximum compelling sub-6 GHz physical-layer era for destiny wireless access. Excellent spectral overall performance finished through manner of spatial multiplexing of many terminals inside the equal time-frequency resource. The 5G structures are characterized through excessive transmission records prices, 1Gbps and above, so large bandwidth transmission is expected. The most vital objectives within the 5G wireless systems design is to deal with the excessive inter photograph interference (ISI) as a consequence of the high statistics fees, and using the accessible spectral bandwidth in resourceful way.MC-CDMA is categorized in to two methods that is ODFM and CDMA. Efficient useful resource allocation is the principle trouble within the development of fourth generation cellular communication systems. For utilizing the internet and multimedia a maximum data fee is preferred, so in this paper the general performance of MC-CDMA systems the usage of Sylow theorem for grouping this is executed that's a spectrum allocation technique is presented. This paper particularly analyzes the presence of Additive white Gaussian Noise (AWGN) in MC-CDMA utilizing QPSK for special variety of subcarrier, exclusive wide sort of customers with the help of MATLAB tool. This paper shows the reduction in BER and power allocation among the MC-CDMA and massive-MIMO.

BER Evaluation in LTE SC-FDMA under Multipath Channels

Channel equalization is very essential step in Single Carrier Frequency Division Multiple Access (SC-FDMA) transmission for overcoming the inter-symbol interference (ISI). Also, to evaluate the data-link and network scheduling of LTE technique, a particular channel modelling is crucial. Due to the techniques’ complexity and requirement of high bandwidth for data transmission in literature, we motivated to perform a comparative analysis for BER reduction in SCFDMA scheme with and without equalizer. Therefor, in order to enhance efficiency of performance and functionality of network application, due to huge demand for lower delay, latency and higher speed by the modern users, BER reduction is a significant factor for enhancing signal quality. The substantial focus of this research is to improve the uplink signal of LTE technology by using two type of linear equalization methods such as zero forcing (ZF) and minimum mean square error (MMSE) at receiver part. Moreover, analysis of BER and SNR for SC-FDMA systems are obtained under several channel models and two different sub-mapping. This evaluation is performed for SC-FDMA in uplink by aid of adaptive modulation techniques like QPSK. Finally, for evaluating the channel equalization efficiency with SC-FDMA and for investigating the response of an uplink transmitter, MATLAB framework, is applied in this study. The results reveal that PAPR reduction does not have significant impact on BER performance.

Nonlinear Tomlinson-Harashima precoding for direct-detected double sideband PAM-4 transmission without dispersion compensation.

In this paper, we propose a nonlinear Tomlinson-Harashima pre-coding (THP) scheme for nonlinear distortion suppression in direct-detected double sideband (DSB) PAM-4 transmission systems. Based on the traditional THP, the feedback term is modified by introducing nonlinear components. In this way, more accurate feedback can be obtained to mitigate the signal distortions, especially the nonlinear distortions including the signal-to-signal beating interference and nonlinear power series caused by chromatic dispersion and square-law detection. Meanwhile, we also propose to only reserve the nonlinear kernels with adjacent tap products in nonlinear THP, for the purpose of computation complexity reduction. To verify the effectiveness, transmissions of double sideband (DSB) PAM-4 signal in 1550nm window are experimentally demonstrated. Volterra FFE is adopted on the receiver side to suppress linear and nonlinear pre-cursors. We optimize various parameters of hardware and apply appropriate simplification to the nonlinear THP kernels. The results indicate that, the proposed nonlinear THP can lead to up to three folds BER reduction, compared to the conventional linear THP. Finally, with the combination of proposed nonlinear THP and conventional Volterra FFE, we successfully transmit 84-Gbps PAM-4 and 107-Gbps PAM-4 respectively over 80 km and 40 km under the hard decision forward error correction (HD-FEC) threshold of 3.8 × 10-3.

Performance of Kramers–Kronig Receivers in the Presence of Local Oscillator Relative Intensity Noise

There is increasing interest in low-complexity coherent optical transceivers for the use in short-reach fiber links. Amongst the simplest configurations is the heterodyne coherent receiver, using a 3-dB coupler to combine the signal with the local oscillator (LO) laser output, and a single photodiode for detection of each polarization. In this paper, through numerical simulations, we investigate the impact of signal–signal beating interference (SSBI) and LO relative intensity noise (RIN) on the performance of such coherent transceivers. We assess the performance of two methods to mitigate the SSBI: first, the use of high LO laser power, and second, the application of digital signal processing-based receiver linearization, specifically, the Kramers–Kronig (KK) scheme. The results indicate that, in the case of a RIN-free LO laser, a strong LO is effective in mitigating SSBI and achieves a similar performance to that of the KK algorithm. However, the required increase in LO-to-signal power ratio (LOSPR) is significant. For example, a 20 dB higher optimum LOSPR was observed in the 28 Gbaud dual polarization 16 QAM system at an optical signal-to-noise power ratio of 22 dB. The drawback of using such a high LOSPR is the increased penalty due to RIN-LO beating terms, which we next investigated. The lower optimum LOSPR and, consequently, the lower impact of LO RIN on the performance of the KK receiver lead to a reduction in the pre-FEC BER by over an order of magnitude for LO RIN levels above −140 dBc/Hz.

Mitigating the interferences and intruders in cognitive radio networks using an authentication protocol over Reed-Solomon codes

Cognitive radio networks have emerged as a promising solution for spectrum scarcity problem. Secondary users (unlicensed users) accessing cognitive radio network suffer from continuous unintentional interference from primary users (licensed users). Also, the adversary present in the channel tries to thwart the secondary users' communication. To address these two problems, an inherent authentication protocol is defined over Reed-Solomon codes. Reed-Solomon codes with authentication protocol are used with M-ary frequency shift keying modulation technique, for transmissions over cognitive radio network. Similarly, the received message is demodulated and decoded to get the original information bits at the receiver. The performance of the proposed scheme is given in terms of bit error rate. The experimental results show that the proposed system performs better in terms of BER reduction. Also, it is shown that the proposed scheme is resistant to replay attack, man-in-the-middle and impersonation kind of attacks.

Orthogonally Precoded Massive MIMO for High Mobility Scenarios

Massive multiple-input multiple-output (MIMO) systems are of high interest for ultra-reliable low-latency communication (URLLC) links. They provide channel hardening, i.e. reduced channel variations, due to the large number of transmit antennas which exploit spatial diversity by beam-forming. Massive MIMO requires channel state information (CSI) on the base station side. For time-varying vehicular communication channels the CSI acquired during the uplink phase will be outdated for the following downlink phase, leading to reduced spatial channel hardening. We investigate a combination of massive MIMO with general orthogonal precoding (OP) to compensate this effect. OP uses two-dimensional precoding sequences in the time-frequency domain and provides channel hardening by exploiting time- and frequency diversity. We show that the combination of massive MIMO and OP is beneficial for time-varying communication channels. While the spatial channel hardening of massive MIMO decreases, the time-frequency channel hardening of OP increases with larger time-variance of the communication channel. An iterative receiver algorithm for massive MIMO with OP as well as a detailed analysis of the channel hardening effect is presented. We demonstrate a BER reduction by more than one order of magnitude for a velocity of 50 km/h = 16.6 m/s using the orthogonal frequency division multiplexing (OFDM) based 5G new radio (NR) physical layer.

Lower Order Modulation Aided BER Reduction in OFDM With Index Modulation

Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is a multi-carrier transmission scheme in which a set of sub-carriers is chosen and modulated according to the incoming bit-stream. It is already established that for the same average bits per channel use, OFDM-IM can provide a better error rate performance when compared to conventional OFDM. In this letter, we propose a novel method to further improve the error rate performance of OFDM-IM with the aid of lower order signal constellations, by using fewer bits for symbol selection and using the remaining bits to select the index combinations. As the increased number of indexing bits demand more index combinations for mapping them, certain index combinations are reused, with the reuse made unambiguous by rotating lower order constellation. This approach provides significant signal-to-noise ratio gains without compromising spectral efficiency when compared to existing OFDM-IM schemes.

Bit error rate reduction of optical communication by means of Tip/Tilt correction

Abstract One of the parameters for evaluating the free space optical link is BER. The atmospheric turbulence increases BER of telecommunication link. One of the BER reduction methods is the use of correction of dynamic aberrations caused by atmospheric turbulence. In this paper first, by using phase plates, atmospheric turbulence has been simulated. In order to determine the refractive index structure parameter, fluctuation of angle of arrival and fitting curve into probability density function of scintillation beam have been applied. The obtained value of C n 2 , from two methods is of order of 10−14 m − 2 ∕ 3 , which are in good agreement with each other. In the following, BER of free space telecommunication link before and after correction has been measured using the correction of tip and tilt low order aberration in the presence of simulated turbulence at laboratory. In this paper, by indirect method, BER was measured by probability density function of fluctuation beam. Before correction, the value of BER was 3 . 302 × 1 0 − 4 that which reduced to 4 . 276 × 1 0 − 7 after the correction.

Novel designs for digital gates based on single electron devices to overcome the traditional limitation on speed and bit error rate

Single electron devices, SEDs, are distinguished among all new nano-scale electronic devices due to their very small size, ultra-low power consumption, and consistent technology. This paper is dedicated to digital application of single electron devices. The paper introduces a method for the speed enhancement and bit error rate reduction based on a new parallelism concept of tunneling paths and reduction of tunneling wait time. Using this method, one can go beyond the theoretical limitation of these devices in any specified technology which comes from quantum uncertainty principle. Correctness of this method is shown by analytical approaches and numerical method i.e. ensemble Monte-Carlo simulation, EMC. In this way, by proposing new designs and removal of maximum speed limitation in addition to BER reduction, this paper improves the seat of SEDs among other competing nano-scale devices.