Bit Error Probability Research Articles

NODR: An NOMA-Based Retransmission Scheme for URLLC in Industrial Wireless Networks

The emergence of new applications (e.g., mobile robots, smart logistics, virtual reality, and augmented reality) in the factory automation scenario has made industrial wireless networks (IWNs) a trend to replace traditional wired networks. One of the urgent challenges is to achieve ultra-reliable and low-latency communications in IWNs. In this article, to cope with massive periodic traffic and lost packets due to volatile channel conditions in IWNs, we, for the first time, combine non-orthogonal multiple access (NOMA) with the automatic on-demand retransmission scheme. To be specific, we formulate an optimization problem to maximize transmission reliability, subject to the constraints of transmit powers and the scheduling policy, and give a detailed analysis of the optimal solution to the formulated problem. To achieve the optimum, we propose an NOMA-based on-demand retransmission (NODR) scheme and derive a closed-form expression for transmission reliability in the case when all the packets experience the same packet error rate. Simulation results demonstrate the effectiveness and efficiency of the NODR scheme over other schemes under different channel conditions.

HARPAGON: An Energy Management Framework for Attacks in IoT Networks

The Internet of Things (IoT) represents an eclectic paradigm that is still growing in popularity. However, security aspects are a major concern for IoT devices due to their applications and the amount of sensitive data they provide. Simultaneously, the energy constraint in IoT networks remains a significant issue due to their limited resources. To reduce their energy consumption, several IoT protocols have integrated the energy-saving mode which offers four operating modes. On the basis of these four states, we derive an analysis framework, named HARPAGON, allowing an attacker to maximize his attack efficiency and minimize his impact in terms of energy consumption. Indeed, the effectiveness of many attacks depends principally on the state of the attacker and the victim at the same time. HARPAGON with the help of Markov chain theory allows modeling the interaction between the attacker and its victims. In this article, we demonstrate the effectiveness of the framework coupled with a jamming attack by comparing it to other types of jamming attacks. Experimental results reveal HARPAGON combined with a jamming attack drastically reduces the performance of the network, with an impact on the packet error rate (PER), which is around 13% higher than the reactive attack and with a reduced energy budget in respect of the other two well-known “green” jamming attacks.

Optical Polarization Division Multiplexing Transmission System Based on Simplified Twin-SSB Modulation.

Optical twin-single sideband (Twin-SSB) modulation, due to the left sideband (LSB) and right sideband (RSB) signal carrying individual data, has become an attractive technique in fiber transmission because it satisfies the demand of the explosive increase in data traffic. This paper focuses on reducing the complexity of Twin-SSB system and further enhancing the spectral efficiency by proposing a polarization division multiplexing (PDM) Twin-SSB modulation scheme. LSB and RSB signals are extracted using de-mapping algorithm instead of optical bandpass filters (OBPFs) to reduce system complexity. To further improve spectral efficiency, PDM is employed to meet the polarization multiplexing transmission and achieve a higher transmission capacity. Based on the PDM Twin-SSB system, the LSB is 3-arr phase-shift-keying (3PSK) modulated, while RSB is quadrature phase-shift keying (QPSK) modulated. We simulated that the bit error ratio (BER) performance of LSB and RSB of X-polarization (X-Pol) and Y-polarization (Y-Pol) at 8-Gbaud, 10-Gbaud, 12-Gbaud, 14-Gbaud, and 16-Gbaud in the case of back-to-back (BTB) and 2 km standard single-mode fiber (SSMF) transmission. The simulation results verify the effectiveness and practical feasibility of the proposed PDM Twin-SSB scheme for future short-distance transmission owing to low cost, simplified structure, low algorithm complexity, and high data transmission capacity.

Signal recovery in optical wireless communication using photonic convolutional processor.

Deep neural networks (DNNs) have been applied to recover signals in optical communication systems and have shown competence of mitigating linear and nonlinear distortions. However, as the data throughput increases, the heavy computational cost of DNNs impedes them from rapid and power-efficient processing. In this paper, we propose an optical communication signal recovery technology based on a photonic convolutional processor, which is realized by dispersion delay unit and wavelength division multiplexing. Based on the photonic convolutional processor, we implement an optoelectronic convolutional neural network (OECNN) for signal post-equalization and experimentally demonstrate on 16QAM and 32QAM of an optical wireless communication system. With system parameters optimization, we verify that the OECNN can achieve accurate signal recovery where the bit error ratio (BER) is below the 7% forward error correction threshold of 3.8×10-3 at 2Gbps. With adding the OECNN-based nonlinear compensation, compared with only linear compensation, we improve the quality (Q) factor by 3.35 dB at 16QAM and 3.30 dB at 32QAM, which is comparable to that of an electronic neural network. This work proves that the photonic implementation of DNN is promising to provide a fast and power-efficient solution for optical communication signal processing.

Mobile jammer enabled secure UAV communication with short packet transmission

This paper studies a mobile jammer enabled secure unmanned aerial vehicle (UAV) communication network in the finite packet length scenario, where the external friendly jammer UAV will transmit jamming signal to deteriorate the quality of eavesdropping channel, and help to improve the secure communication performance of the source UAV. Specifically, an average effective secrecy rate (AESR) maximization problem is formulated by jointly designing the trajectories and transmit power of the source/jammer UAV subject to the UAVs’ mobility constraints and power constraints. It is also verified that there exists a unique optimal packet error rate to maximize the AESR. The formulated problem is mathematically intractable, as it is nonconvex and involves coupled optimization variables. Therefore, we first decompose the trajectories and power optimization problem into four non-convex subproblems, and then transform them into standard convex problems by applying first-order Taylor expansion. Then, an efficient alternating optimization algorithm for AESR problem based on Bisection method and successive convex approximation (SCA) technology is presented by addressing the five subproblems iteratively. Simulation results are provided to verify that our proposed scheme can obtain considerable better AESR gain compared to other four benchmark schemes.

Use of Chaotic Oscillations for Precoding and Synchronization in OFDM

This paper proposes a novel linear precoding method for Orthogonal Frequency Division Multiplexing (OFDM) based on the employment of the chaotic waveforms generated by the fourth-order chaotic oscillator and orthonormalized by the Gram-Schmidt process. The proposed linear precoding method is aimed to increase resilience to the multipath propagation issues and reduce the Peak-to-Average Power Ratio (PAPR) of the transmitted signal. Moreover, the chaotic waveform enables novel timing synchronization methods to be implemented in the receiver. The modelling of baseband Linear Precoded OFDM (LP-OFDM) data transmission system with Rayleigh channel has been performed in Simulink environment to validate the proposed method and to compare the performance to the classic precoding methods, such as Walsh-Hadamard Transform (WHT). Experiments have shown that in a high Signal-to-Noise Ratio (SNR) scenario, the employment of the novel precoding scheme allows reducing Bit Error Ratio (BER) by several dB compared to non-precoded OFDM. The proposed precoding method leads to the reduction of PAPR; however, it is not as efficient as classical precoding schemes, such as WHT. Experimental evidence of synchronization of the chaotic oscillators within 50 samples long time interval is presented.

Joint Design of Channel Training and Data Transmission for MISO-URLLC Systems

For the ultra-reliable low-latency communication (URLLC), the existing joint design algorithms of channel training and data transmission are not applicable due to the stringent reliability requirement and limited blocklength. To address this issue, we develop a low-complexity joint design framework for MISO communication based on the finite blocklength code (FBC). Specifically, an approximate bound of the packet error probability (PEP) is first derived and validated by practical modulation and coding schemes. It reveals the inherent tension between reliability, latency, and information bit number. Then, we formulate the joint design into a nonconvex optimization problem with the objective to maximize the information bit number. By exploiting the monotonicity of the PEP approximate bound, we provide closed-form solutions of power and blocklength allocation. Thereby, we develop a low-complexity algorithm to support the URLLC services aiming at the information bit number maximization. Furthermore, we investigate the joint designs to optimize the reliability, latency, and total energy, respectively, to fully meet the diverse demands of URLLC services. Finally, numerical results are provided to validate the proposed joint designs. The results show the outage capacity-based design severely underestimates the required wireless resources.

Optical Generation and Transmission of mmWave Signals in 5G ERA: Experimental Evaluation Paradigm

We demonstrate the generation, of a mmWave signal via the injection of an optical frequency comb (OFC) into an integrated tunable dual distributed Bragg reflector (DBR) laser as well as the fiber transmission and the processing of this signal by an optical beamforming network (OBFN). The dual DBR laser is based on a hybrid indium phosphide (InP) – polymer photonic integrated circuit (PIC). Two different cases have been examined in which the microwave signal is centered around 39 GHz and 60 GHz respectively, carrying quadrature amplitude modulation (QAM) formats at 0.5 Gbaud. In this proof-of-concept scenario, the OBFN consists of two optical paths, where the relative true time delay is induced by an optical delay line (ODL). Extensive comparison between the back-to-back (B2B) case and scenarios with transmission over 25 km of standard single-mode fiber (SSMF) has been made using the error-vector magnitude (EVM) and the bit-error ratio (BER) as evaluation criteria. In all cases, error-free transmission was suggested for all QPSK signals, whereas a worst-case EVM of 11.8% was observed for 16-QAM transmission, successfully showcasing the concept’s potential. The generated microwave signal’s frequency can be set arbitrarily high, provided that high-speed photodetection equipment is available for the detection and down-conversion of the signal. Extension to higher antenna elements (AEs) numbers is straight-forward, relying only on the number of available photodetectors.

Mitigating Crosstalk of Vortex Beam Within an OAM-Mode Group Over an OAM Fiber by Reversing Transmission Matrix

For enhancing channel capacity and spectrum efficiency, vortex beam carrying orbital angular momentum (OAM) has been ardently investigated in optical communication. However, the crosstalk among OAM modes induced by mode coupling has seriously hindered the development of vortex beam communication (OBC). A novel concept of mitigating crosstalk within an OAM-mode group for a short-haul optical fiber communication (OFC) is proposed by reversing the transmission matrix. To support more OAM modes propagation, a step-index OAM fiber with ring-shaped profile is also designed and fabricated, which can support 6 vector/OAM modes propagation. A proof-of-concept experiment is performed for verifying the feasibility of the proposed concept, where a quadrature-phase-shift-keying (QPSK) signal is utilized as an excitation signal. Bit-error-ratio (BER) and constellation diagram (CD) are employed to evaluate the performance of the proposed system. The captured intensity profiles and interference diagrams demonstrate that the propagated four OAM beams within the 2rd OAM-mode group are successfully received. The measured BER and CD illustrate that the crosstalk within the mode group can be significantly mitigated. Further, although the data speed or fiber length is increased, the system performance using the proposed concept is still superior to the case without increasing fiber length or data speed when the proposed concept is missed. Therefore, the proposed concept is effective for mitigating the crosstalk and can be then used for a short-haul OAM-based OFC.

Information Freshness and Energy Harvesting Tradeoff in Network-Coded Broadcasting

This letter investigates both information freshness and energy harvesting (EH) in downlink information update systems. Information freshness is characterized by age of information (AoI). We consider a scenario in which a large update message is packetized into <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> small packets and encoded by random linear network coding (RLNC). A base station continuously broadcasts the RLNC-encoded packets to multiple users until all the users have received the message. When a user successfully receives the update message while at least one other user has not received it yet, the user harvests energy from the received signals. A key challenge is to decide the value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> in the message packetization in order to achieve low AoI and high EH simultaneously. To this end, we conduct a theoretical analysis of the tradeoff between the AoI and EH performance under different values of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> . In particular, the packet error rates of short packets in the message packetization are estimated by the short packet theory, and the closed-form AoI and EH formulas are derived. Our numerical results reveal that there exists a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> (neither too small nor too large) that can achieve both low AoI and high EH.

Scheduling Out-of-Coverage Vehicular Communications Using Reinforcement Learning

Performance of vehicle-to-vehicle (V2V) communications depends highly on the employed scheduling approach. While centralized network schedulers offer high V2V communication reliability, their operation is conventionally restricted to areas with full cellular network coverage. In contrast, in out-of-cellular-coverage areas, comparatively inefficient distributed radio resource management is used. To exploit the benefits of the centralized approach for enhancing the reliability of V2V communications on roads lacking cellular coverage, we propose VRLS (Vehicular Reinforcement Learning Scheduler), a centralized scheduler that proactively assigns resources for out-of-coverage V2V communications \textit{before} vehicles leave the cellular network coverage. By training in simulated vehicular environments, VRLS can learn a scheduling policy that is robust and adaptable to environmental changes, thus eliminating the need for targeted (re-)training in complex real-life environments. We evaluate the performance of VRLS under varying mobility, network load, wireless channel, and resource configurations. VRLS outperforms the state-of-the-art distributed scheduling algorithm in zones without cellular network coverage by reducing the packet error rate by half in highly loaded conditions and achieving near-maximum reliability in low-load scenarios.

Novel Algorithm for Nonlinear Distortion Reduction Based on Clipping and Compressive Sensing in OFDM/OQAM System

Orthogonal Frequency Division Multiplexing with Offset Quadrature Amplitude Modulation (OFDM/OQAM) signal has high peak-to-average power ratio (PAPR) problem. It not only affects the distortion in High Power Amplifier (HPA) but also results in bit error ratio (BER) degradation. In this paper an improved algorithm based on Clipping and Compressed Sensing (CS) is proposed. The transmitter uses clipping to reduce the PAPR and, the receiver uses an improved inverse model, to reduce the nonlinear distortion introduced by HPA and CS cancels the signal distortion introduced by clipping. Simulation results show that the proposed method not only significantly reduces the PAPR of OFDM/OQAM signals, but also effectively improves the BER performance of the system.

Client-server system for monitoring the quality of TV broadcasting in Russia

The strategy for the development of television and radio broadcasting in the Russian Federation until 2025 specifically states the need to ensure the reliability of uninterrupted television and radio broadcasting. The quality of DVB-T2 broadcasting is estimated by the data transmission rate and the bit error rate BER (Bit Error Ratio) stability margin «at the last mile» in the retransmitters’ broadcast zones. The distributed client-server system of broadcast quality monitoring in RF, proposed in the article, uses the necessary equipment, including BER sensors based on programmable receivers combined with single-board microcomputers implemented on SoC processors. Collection and processing of data in broadcasting areas with the help of the proposed monitoring system will allow specialists engaged in practical network development to make an objective conclusion about the necessity and ways of SFN network reconstruction to provide uninterrupted TV and radio broadcasting in RF. Modernization and technical re-equipment of SFN networks will provide a solution to the problems related to certification of satellite earth stations and transmitters of SFN networks, provision of various services and broadcasting services of DVB-T2 standard to the population with high quality.

C-band 120-Gb/s PAM-4 transmissions over a 100-km dispersion-uncompensated SSMF using joint combined pulse shaping and low-complexity nonlinear equalization.

In C-band intensity modulation and direct detection (IM/DD) systems, the frequency-dependent power fading induced by chromatic dispersion (CD) and square-law detection limits the transmission capacity and distance, especially for beyond 100-Gb/s transmissions over a 100-km dispersion-uncompensated link. To reach this goal, we propose a scheme of nonlinear pre-distortion, novel, to the best of our knowledge, combined pulse shaping, and post nonlinear equalization for four-level pulse amplitude modulation (PAM-4)-based IM/DD systems. At the transmitter, the nonlinear pre-distortion is used to generate unequally spaced PAM-4 symbols for pre-compensating the nonlinearities. While the novel pulse shaping, simply shaped by the linear combination of two inter-symbol interference (ISI)-free pulses, alters the frequency-domain power distribution of the PAM-4 signal and results in performance improvement. At the receiver, low-complexity post nonlinear equalization using an absolute-term based nonlinear equalizer with weight sharing (AT-NLE-WS) is performed to eliminate CD-induced power fading and residual nonlinear impairments. With the cooperation of these techniques, record 120-Gb/s PAM-4 signals are successfully transmitted over a 100-km standard single-mode fiber (SSMF) with the measured bit error ratio (BER) below 3.8 × 10-3, achieving >9% improvement of system capacity in comparison with the conventional pulse shaping schemes.

Comparison of low-complexity sparse and weight-sharing nonlinear equalizers for C-band 100-Gbit/s DSB PAM-4 transmission over 60-km SSMF.

To cope with the nonlinear distortions and the chromatic dispersion (CD) induced power fading in double-side band (DSB) intensity modulation and direct detection (IM/DD) transmission systems, high-performance Volterra nonlinear equalizers (VNLEs) including Volterra feed-forward equalizer (VFFE) and Volterra decision-feedback equalizer (VDFE) are widely applied. However, the conventional VNLEs have high computational complexity, especially for longer memory lengths. In this paper, based on sparse and weight-sharing strategies for significant kernel reduction, we propose four low-complexity NLEs including a sparse diagonally pruned VDFE (S-DP-VDFE), a sparse diagonally pruned absolute-term DFE (S-DP-ATDFE), a weight-sharing DP-VDFE (WS-DP-VDFE), and a weight-sharing DP-ATDFE (WS-DP-ATDFE), and present a comprehensive comparison among them in terms of computational complexity and bit error ratio (BER) performance in a C-band 100-Gbit/s PAM-4 transmission system over 60-km standard single-mode fiber (SSMF). The experimental results show that the proposed S-DP-VDFE and WS-DP-VDFE not only exhibit comparable performance with the conventional DP-VDFE but also reduce the complexity by 54.5% and 45.9%, respectively. While the proposed S-DP-ATDFE and WS-DP-ATDFE yield lower complexity at the expense of a slight performance degradation. Compared with the proposed S-DP-VDFE, S-DP-ATDFE, and WS-DP-VDFE, the proposed WS-DP-ATDFE with the lowest number of real-valued multiplications of 45 achieves up to 90.9%, 81.6%, and 95.8% complexity reduction, respectively, at the 7% hard-decision forward error correction (HD-FEC) BER limit of 3.8 × 10-3. The proposed low-complexity WS-DP-ATDFE shows great potential in low-cost and high-performance IM/DD optical transmission systems.

Optimal quantised bits for estimation over a capacity and power limited, lossy channel

This letter considers the problem of estimating the state of a scalar dynamical system over a wireless channel that is lossy, capacity, and power limited. The limited power assumption, which is valid for most real problems, links the number of quantisation bits and packet error rate. As the number of quantisation bits increases, the quantisation noise decreases but the packet loss rate increases. It is shown that the estimation error variance (EEV) is minimised for a range of quantisation bits. Further, it is shown that operating beyond the optimal range sharply increases the EEV. Simulation results corroborating the analytical results are also presented.

Unequally spaced PAM-4 signaling enabled sensitivity enhancement of a simplified coherent receiver applied in a UDWDM-PON.

We experimentally demonstrate a 4 × 10 Gb/s cost-effective coherent ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON) by the use of unequally-spaced 4-level pulse-amplitude modulation (UES-PAM-4) signaling. Because of the advantages of simple architecture and low cost, the simplified coherent receiver (SCR) based on the transmitted signal diversity (TS-D) has been reported, but its receiver sensitivity is constrained by the severe noise arising in the higher level of conventional PAM-4 signals. Here, we first experimentally demonstrate the UES-PAM-4 signaling for the SCR based on the TS-D, by altering the PAM-4 level spacing and the decision threshold through the gradient descent algorithm (GDA). Consequently, we can experimentally achieve -30.1 dBm RS for single wavelength at the bit-error ratio (BER) of 3.8 × 10-3. Compared with the conventional equally-spaced PAM-4 (ES-PAM-4) signaling, 1.3 dB RS enhancement can be secured after the 20-km standard single-mode fiber (SSMF) transmission. Meanwhile, the UES-PAM-4 signaling is experimentally verified for 4 × 10 Gb/s UDWDM-PON. An average RS of -29.6 dBm and 32.6 dB power budget are obtained after the 20-km SSMF transmission. The proposed UES-PAM-4 signaling with the RS enhancement is a promising candidate for the UDWDM-PON by utilizing the existing optical distribution network (ODN).

Beaconless angle-of-arrival tracking with improved receiver sensitivity and tracking precision for free-space optical communications

One of the technically challenging issues of free-space optical communication systems is the mitigation of angle-of-arrival (AoA) fluctuations, mainly arising from the vibration of receiving end and atmospheric turbulence. A common approach is to employ an AoA tracking system at the receiver. Beacon-based AoA tracking requires the beacon light, thus the system could be complicated and bulky when implemented. Beaconless AoA tracking could help to minimize the optical components required. This tracking typically requires an optical beam splitter to direct the received optical signal both to the beam position sensor and data photo-detector (PD). However, the presence of beam splitter results in optical power loss and tracking imprecision. In this paper, we propose a design of AoA tracking system based on an integrated beam positioning sensor and data PD to obviate the need for beacon light and beam splitter. We carry out a proof-of-concept experimental demonstration of AoA tracking systems for a 10-Gb/s free-space optical link over 104 m, comparing its performance with that of the conventional system. The demonstration shows a loss reduction of >2.9 dB by using the proposed design. It also shows that the proposed design improves the tolerance to AoA fluctuation by more than a factor of 2 at a target bit-error ratio of 10−3. The tracking time is measured to be 171 ms at an AoA fluctuation of 250 μrad. We show that the loop controller and fast steering mirror bandwidths are the main factors limiting the tracking time.

Reducing cyclic prefix overhead based on symbol repetition in NB-IoT-based maritime communication

With the increasing maritime activities, a great demand of wide-area maritime digital data services is needed. Therefore, Narrowband Internet of Things (NB-IoT) that can provide wide coverage has been expected as an application for maritime communication networks (MCNS). In this paper, we aim to enhance the spectral efficiency in NB-IoT by reducing the cyclic prefix (CP) overhead in random access signal without causing interference. The key point of the proposed scheme is the symbols transmitted for multiple times repeatedly in NB-IoT. Specifically, all CP are removed and multi-path fading effect is eliminated by using a repeated symbol to cover the disturbed symbol to construct a circular convolution structure of the channel with the same effect as adding CP. In addition, a single-tap equalization is still appropriate. To validate the effectiveness of the proposed scheme, simulation results are carried out with respect to the bit error ratio (BER).

A Novel Frequency Double Vector Millimeter Wave Signal Generation Scheme Based on a Single Polarization Modulator With Precoding

In the work, we employed a single polarization modulator to achieve double frequency vector millimeter wave (mm-wave) signal generation scheme with optical carrier suppression (OCS), which just depend on a polarization modulator and two linear polarizers, and electronic circuits is needless to control the drift of modulator bias points and no optical filters is needed to filter out undesirable harmonics. In this scheme, we set up a simulation platform to generate 40 GHz QPSK modulated vector millimeter-wave signals and analyzed the performance. The results showed when the input power for the generated 10-Gbit/s vector millimeter-wave into PD is not less than −23 dBm, the bit-error ratio could be below 3.8×10−3, which demonstrated that the generated vector millimeter-wave signal enabled by our proposed scheme could work well.