Genetic optimization of 5G-NR LDPC codes for lowering the error floor of BICM systems

With the wide range of commercial uses of fifth generation (5G), new radio (NR) communication networks, the wireless transmission becomes more efficient, reliable and faster. At the same time, high-quality signal transmission for 5G networks and beyond has also encountered new opportunities and challenges. Channel coding is a key technology to ensure reliable information transmission and service quality. However, the 5G-NR LDPC coded bit-interleaved coded modulation (BICM) sometimes suffers from relatively high error floors, so it can not always guarantee the high-quality and low-delay wireless transmission. In this paper, we propose a further redesign of the 5G-NR LDPC coded BICM based on genetic algorithm (GenAlg). By adjusting the number of the non-zero elements, the corresponding positions and shifting values in base matrix, we optimize the 5G-NR LDPC codes with GenAlg according to the error performances of coded BICM schemes. Simulation results show that the optimized 5G-NR LDPC codes which still support length and rate compatible coding have lower error floors with a little performance loss int the waterfall region compared to the standard 5G-NR LDPC codes with different modulation orders.     

LDPC coded DFT/DCT-spread SC-FDMA for image communication: A compressed sensing approach

A compressed sensing (CS)-based detector is proposed for the low-density parity-check (LDPC) coded single carrier frequency division multiple access (SC-FDMA) scheme. The proposed CS-based detector can be employed at the receiver of LDPC-coded SC-FDMA systems for efficient image communications over vehicular channels. The proposed detector employs a suitable sparse recovery algorithm. We have considered both the discrete Fourier transform (DFT)-based and the discrete cosine transform (DCT)-based SC-FDMA for mitigating the channel-induced dispersion at a low peak to average power ratio (PAPR). Additionally, both the linear equalizer (LE) and the decision feedback equalizer (DFE)-based SC-FDMA have been considered for image communication. The performance of the proposed technique is investigated using a number of image quality metrics. The qualities of the received images are also compared visually. The complexity of the proposed detector and that of the benchmark detectors are quantified. Furthermore, the performance and the complexity of the proposed system using some of the sparse recovery techniques are investigated and compared. Our simulations demonstrate that LDPC coded SC-FDMA using the compressed sampling matching pursuit (CoSaMP)-based CS detector can significantly improve the performance of image communication over vehicular channels.     

采用纠缠辅助量子LDPC码和检错重传策略的 量子直传通信方案

针对现有量子信息直传协议在有噪音量子信道下传输效率低及可靠性差的问题,提出了一种有效利用纠缠资源的量子安全直传通信方案.通过收发双方共享纠缠粒子作为辅助比特,采用纠缠辅助量子低密度校验码对量子态信息进行前向纠错保护,以提高系统在噪音环境下的传输可靠性.同时采用自动请求重传策略对量子态信息进行检错编码保护,当因窃听或强噪音导致译码获得的信息不正确时,则请求发端对该组信息进行编码重传操作.文中对所选用纠缠辅助量子低密度校验码在量子退极化噪音信道下的迭代译码性能进行了仿真,最后对方案的安全性进行了分析论证.     

Improved Chernoff Bound of Gaussian Q-function with ABC algorithm and its QAM applications to DB SC and MRC systems over Beaulieu–Xie channels

In this study, we propose an improved upper bound for the Gaussian Q function by using artificial bee colony algorithm. Then, we investigate the performance of the dual-branch (DB) selection combining (SC) and maximal ratio combining (MRC) systems over the Beaulieu–Xie fading channels. The probability density functions of the instantaneous signal to noise ratio for the considered systems are obtained. Employing the proposed upper bound, we derive closed-form expressions of the error probability for the quadrature amplitude modulation (QAM) techniques such as rectangular QAM (RQAM), cross QAM (XQAM), and hexagonal QAM (HQAM). Furthermore, the asymptotic error probability expressions for the DB SC system are also obtained to simplify the analyses. The effects of some key parameters in the systems are shown in the results. Comparisons of the different modulation types and the different upper bound approaches for the Gaussian Q function are presented. Finally, it has been shown that the upper bound approximation presented in this study can be widely used for many communication applications.     

基于循环前缀相关性的水声OFDM信号调制识别方法*

本文研究水声OFDM通信信号与常见单载波水声数字通信信号(MPSK,MFSK)之间的调制识别问题。考虑到水声信道复杂传播特性对循环前缀相关性的影响,本文通过截取信号前后片段并迭代搜索双相关峰进行无需先验知识的水声OFDM通信信号特征参数提取,在此基础上设计了一种基于模糊系统的水声OFDM通信信号识别器。对不同信道条件下海上实录信号数据的识别实验结果表明了本文方法的有效性。     

IRZ-Manchester coding for downstream signal modulation in an ONU-source-free WDM-PON

Inverted return-to-zero (IRZ)-Manchester coding is proposed for optical downstream signal using amplitude shift keying (ASK) modulation in an optical network unit (ONU)-source-free wavelength-division-multiplexing passive optical network (WDM-PON), and ASK modulation is used for the optical upstream signal generation using remodulation over the optical downstream signal. With IRZ-Manchester coding, differential phase shift keying (DPSK) modulation can be overlaid on the downstream optical ASK signal for broadcasting services. Our experimental results show that the IRZ-Manchester coded optical ASK downstream signal has no modulation extinction ratio restrictions from the overlaid DPSK modulation, and that the remodulated optical upstream signal has very limited signal crosstalk from the downstream signals. In comparison with the conventional schemes using only Manchester coding or IRZ modulation, the proposed IRZ-Manchester coded modulation scheme shows better performance under different PON upstream and downstream traffic bit rate ratios.     

一种鲁棒性强的OFDM 水声通信系统*

为了在不同衰落水声信道下实现正交频分复用水声通信,该文提出了一种鲁棒性强的正交频分复用水声通信方案,方案包括编码调制、信道估计和多普勒估计等内容。为了使该系统更稳健,整个信道编码分为两个步骤。首先,循环冗余校验编码器和里德-所罗门编码器用于编码整个数据包,然后循环冗余校验编码器和Turbo 编码器用于编码每个数据帧,其中比特交织编码调制技术用来对抗信道的时变特性。为了得到水声信道估计,使用线性最小均方误差估计器来处理导频数据得到信道估计值。多普勒估计包括帧的多普勒估计和符号的多普勒估计。实验结果表明该系统在不同的衰落信道下都能实现正确的跟踪和译码,系统的鲁棒性能优越。此外,该系统算法计算简单,易于实现,具有良好的工程应用价值。     

低密度奇偶校验码在光通信中的性能

低密度奇偶校验码(LDPC)不仅有逼近香农限的良好性能, 而且译码复杂度较低, 结构灵活, 是近年信道编码领域的研究热点, 在光通信系统中有广泛的应用前景。针对非规则Tanner图上构造的低密度奇偶校验长码具有良好的性能, 以及其在光通信系统中的应用, 构造了几种LDPC码, 并采用置信传播(BP)译码, 在加性高期白噪声(AWGN)信道、二相移相键空(BPSK)调制下进行了计算机仿真。根据规则LDPC码和非规则LDPC码的误码率(BER)和FER曲线, 对规则码和非规则LDPC码在编译码方面以及性能方面作了分析和比较, 进而对构造在光通信系统中具有实用价值的LDPC码提出了看法。通过理论分析与仿真结果表明LDPC 码型具有良好的性能, 可以节省硬件开销, 比较适用于光通信系统中, 可作为超强前向纠错码型的候选码。     

Entanglement can completely defeat quantum noise

We describe two quantum channels that individually cannot send any classical information without some chance of decoding error. But together a single use of each channel can send quantum information perfectly reliably. This proves that the zero-error classical capacity exhibits superactivation, the extreme form of the superadditivity phenomenon in which entangled inputs allow communication over zero-capacity channels. But our result is stronger still, as it even allows zero-error quantum communication when the two channels are combined. Thus our result shows a new remarkable way in which entanglement across two systems can be used to resist noise, in this case perfectly. We also show a new form of superactivation by entanglement shared between sender and receiver.     

近程高速水声毫米波通信仿真与试验验证*

水声信道的严重双扩特性极大地限制了水声高速通信的稳健性。针对近程高速水声通信技术的需求,该文基于水声毫米波频段,提出了一种基于超奈奎斯特发射技术及高阶调制技术的单载波的水声毫米波通信技术。而超奈奎斯特发射技术以及高阶调制给接收机带来了极大的挑战:一是超奈奎斯特发射技术引入了严重的符号间干扰,二是高阶调制系统的符号检测对信道估计的精度要求很高。针对以上问题,该文提出了一种基于迭代信道估计技术的迭代软反馈DFE接收机技术。仿真实验表明:采用128QAM高阶调制时,在较为严重的多途衰落信道条件下,采用所提出的接收机可以在15 dB时实现无误码传输。信道水池试验证明:当通信带宽为300 kHz,通信符号率为300k符号/秒且采用64QAM调制时,在发射平台慢速运动的条件下可以实现900 kbps的净数据率,其相应的频谱利用率高达6 Bits/s/Hz。     

Cooperative diversity performance of selection relaying over correlated shadowing

The study of relaying systems has found renewed interest in the context of cooperative diversity for communication channels suffering from fading. In particular, dual-hop relaying with diversity combining of the relayed and direct path at the receiver has practical importance and can be considered as a building block for forming larger communication systems. This paper presents novel analytical expressions and numerical results on cooperative diversity performance using selection relaying over correlated lognormal channels for both SC and MRC techniques at the receiver. In addition, an exact framework for comparing the performance and efficiency of the medium access protocol and relay capabilities (TDMA/half-duplex, SDMA/full-duplex) is proposed. Finally, based on the analysis and novel mathematical expressions for the outage probability, we investigate the impact of the lognormal parameters (including correlation) on the cooperative system performance and its efficiency.     

量子Turbo乘积码

量子通信是经典通信和量子力学相结合的一门新兴交叉学科.量子纠错编码是实现量子通信的关键技术之一.构造量子纠错编码的主要方法是借鉴经典纠错编码技术,许多经典的编码技术在量子领域中都可以找到其对应的编码方法.针对经典纠错码中最好码之一的Turbo乘积码,提出一种以新构造的CSS型量子卷积码为稳定子码的量子Turbo乘积码.首先,运用群的理论及稳定子码的基本原理构造出新的CSS型量子卷积码稳定子码生成元,并描述了其编码网络.接着,利用量子置换SWAP门定义推导出量子Turbo乘积码的交织编码矩阵.最后,推导出量子Turbo乘积码的译码迹距离与经典Turbo乘积码的译码距离的对应关系,并提出量子Turbo乘积码的编译码实现方案.这种编译码方法具有高度结构化,设计思路简单,网络易于实施的特点. 关键词： CSS码 量子卷积码 量子Turbo乘积码 量子纠错编码     

Deep neural network-based detection of index modulated MIMO-OFDM

Multiple-input multiple-output orthogonal frequency division multiplexing with index modulation (MIMO-OFDM-IM) has been introduced as a new transmission method for 5G and beyond communications. On the other hand, deep neural networks (DNNs) have started to be effective in many fields, including wireless communication, due to their advantages such as low complexity, high performance, low processing times, etc. Since the optimum decoding for MIMO-OFDM-IM grows exponentially with higher modulation orders and the number of transmit and receive antennas, DNN-based decoding will be a potential choice for the next generation receiver architecture. In this work, a novel fully connected DNN based MIMO-OFDM-IM to jointly detect the transmitted symbols from each antenna is proposed and its performance is analyzed. As seen from the simulation results, the proposed DNN-based detector shows a close bit error rate performance to optimum detection with lower computational complexity.     

Multiple-symbol noncoherent learning detection of coded QAM signals in IEEE 802.15.3 Wireless Multi-media Networks

We consider the noncoherent deep learning problem for coded signal detection under the phase noncoherent channels for remote home healthcare applications with high data rate. In particular, a multiple-symbol noncoherent learning detection (MNLD) scheme based on neural networks is proposed for low-density parity-check (LDPC) coded noncoherent quadrature amplitude modulation (QAM) signals in IEEE 802.15.3 Wireless Multi-media Networks. Our derivation shows that extensive operations for the first kind zero-order modified Bessel function is unavoidable for the implementation of the optimal bit log-likelihood ratio (LLR) for decoding in traditional multiple-symbol detection (MSD) scheme. The perfect estimation of the channel state information (CSI), i.e., a priori information about the variance of the additive white Gaussian noise (AWGN), is also required for the receiver. This is clearly not computationally practical for Wireless Multi-media Networks. Consequently, we developed an improved approach based on feed-forward neural networks to accurately calculate the bit LLR. Furthermore, to decrease the generation size of training set and thus increase the training speed of the proposed neural networks, we uniformly quantize the continuous carrier phase offset (CPO), which is random and unknown, into discrete status. Our simulation results verify the learning efficiency of this simplified training-set generation configuration. The decoding convergence is successfully accelerated and much performance gain is finally achieved when compared with traditional decoding using the perfect bit LLR. This is clearly critical for high reliable transmission of home healthcare information.     

一种基于编码孔径成像原理的三维成像方法

三维成像技术因其应用广泛而备受关注。根据编码孔径成像的基本原理,提出了一种非相干可见光三维成像方法。这种两步成像方法的第一步采用空间位置编码的照相机阵列对物体拍照,在第二步中,首先将照相机阵列拍照得到的物体照片根据拍照时的位置关系合成为一幅图像,然后采用计算机程序模拟光学反投影解码方法解码再现出物体不同深度的表面分层图像。设计了初步的实验,该实验采用1部照相机依次在各编码位置对物体模型拍照,编码形式是包含9个点的无冗余阵列形式,物体模型只包含2个深度层次,布置在距离照相机阵列1.5m的地方。实验得到了信噪比较高的物体模型的分层解码图像,验证了这种三维成像方法的可行性。     

Gray-scale data pages for digital holographic data storage

The prospects for gray-scale (or multilevel) digital holographic data storage are theoretically and experimentally investigated. A simple signal-to-noise ratio (SNR) partitioning argument shows that when SNR scales as 1 over the number of holograms squared, five gray levels (log(2) 5bits/pixel) would be expected to result in a 15% capacity increase over binary data pages. However, the additional signal-dependent noise sources present in practical systems create a baseline SNR that reduces both the optimal number of gray levels and the resulting gain in capacity. To implement gray-scale recording experimentally, we adapt the predistortion technique previously developed for binary page-oriented memories [Opt. Lett. 23, 289 (1998)]. Several new block-based modulation codes for decoding gray-scale data pages are introduced. User capacity is evaluated by an experimental technique using LiNbO(3) :Fe in the 90 degrees geometry. Experimental results show that a balanced modulation code with three gray levels provides a 30% increase in capacity (as well as a 30% increase in readout rate) over local binary thresholding.     

Spectrally Efficient 3D Optical CDMA Using Coherent Spatial Phase–Time Coding/Decoding

We demonstrate a WDM compatible optical CDMA system incorporating 3D spectral phase–time encoding/decoding. We provide coding and decoding using binary [0, π] phase chips for six users at 6 Gb/s, with a single coded signal separated with an acceptable bit-error rate ≤10 ^?9. The coding and decoding method is based on 3D coding of tightly spaced phase-locked laser lines that is compatible with conventional WDM networking. In optical CDMA systems, we propose to provide encoding and decoding done by converting Hadamard codes (used for conventional CDMA system) to the phase codes. We report that duo-binary modulation format is the best with adequate bandwidth compression. We confirm that better simulation results are reached in terms of the Q factor and bit error rate.     

Power and rate control in wireless communication systems with energy harvesting and rateless codes

In this paper, for a wireless communication system with energy harvesting and rateless error correction codes, the joint optimization of transmit power, modulation scheme and code rate to maximize the long-term average achievable transmission rate under the constraint of available energy is studied. The method is given first to determine the codeword length (or code rate) for a signal-to-noise ratio (SNR) under the constraint of a pre-defined decoding error probability. Then the formula of the actual transmission rate is deduced with a specific modulation and code rate, and the optimization problem to maximize the long-term average actual transmission rate is constructed under the constraints of available harvested energy and the decoding complexity of the rateless code. Since energy harvesting and channel fading are both stochastic processes, the optimization problem is difficult to solve. By using the Lyapunov optimization framework, the original long-term optimization problem is transformed into a per time slot one. Then an efficient numerical method is proposed to obtain the solution to the problem. The proposed algorithm is verified by simulation, and the results show that the proposed algorithm can achieve a higher average actual transmission rate than the comparison algorithms aiming at optimizing the channel capacity.     

A tutorial on laser-based lighting and visible light communications:device and technology [Invited]

This tutorial focuses on devices and technologies that are part of laser-based visible light communication(VLC)systems. Laser-based VLC systems have advantages over their light-emitting-diode-based counterparts, including having high transmission speed and long transmission distance. We summarize terminologies related to laser-based solid-state lighting and VLC, and further review the advances in device design and performance.The high-speed modulation characteristics of laser diodes and superluminescent diodes and the on-chip integration of optoelectronic components in the visible color regime, such as the high-speed integrated photodetector,are introduced. The modulation technology for laser-based white light communication systems and the challenges for future development are then discussed.     

Resource block Filtered-OFDM for future spectrally agile and power efficient systems

Spectrum sharing is a common paradigm in future communication systems and a spectrally agile baseband waveform with minimal out-of-band emissions is a critical component. In this paper, we propose a new multicarrier modulation technique, called resource block Filtered-OFDM (RB-F-OFDM) and present the transceiver design. This waveform can be used over channels with non-contiguous spectrum fragments and exhibits very low adjacent channel interference, which is required for cognitive radio systems with multi channel carrier aggregation capabilities. As such, regulatory based very stringent adjacent channel leakage ratio (ACLR) and adjacent channel selectivity (ACS) requirements can be met. We show that the transceiver complexity may be reduced by utilizing an efficient polyphase implementation that is commonly used in the filter bank multicarrier (FBMC) modulation. In addition, some efficient peak-to-average power ratio (PAPR) reduction techniques can be naturally applied. The new design is backwards compatible with legacy OFDM based systems. Simulation results to evaluate the performance, including measured bit error rate (BER) in multipath channels, are provided.