激光通信网络通信误差的智能控制系统

在激光通信网络通信过程,由于采用大气作为数据传输的信道,而大气具有时变性,使得通信过程中存在一定的误差,而当前方法无法对通信误差进行自动控制,为了提高激光通网络的通信性能,设计了一种激光通信网络通信误差的智能控制系统。首先对当前激光通信网络通信误差的控制研究现状进行分析,找到引起误差高的原因,然后设计了激光通信网络通信误差的智能控制系统硬件和软件模块,最后对激激光通信网络通信误差的智能控制系统性能进行了测试。结果表明,本文系统大幅度降低了通信误差,提高了激光通信网络的通信精度,且相对于其它控制系统具有明显的优势。

多模态电磁涡旋波复用天线通信误差控制仿真

传统电磁涡旋波天线通信误差控制方法无法实现通信输入信息量和输出信息量的一致性,导致误差控制耗时长,且天线存在窄带宽问题。为此设计多模态电磁涡旋波复用天线通信误差控制方法。利用轨角向量技术改善频谱效率,采用L型探针贴片设计8个阵元以圆周阵列等夹角排列的复用天线,获取复用天线通信传输过程中产生的激励幅度误差、相位误差、耦合干扰、阵元安置误差,利用误差反馈控制方法控制通信中输入信息量和输出信息量的一致性,抑制通信误差扰动,实现多模态电磁涡旋波复用天线的误差控制。仿真结果表明,阵元复用天线能够有效改善天线窄带宽的问题,10bB的带宽能够覆盖的频率区间为[1.03,2.2]GHz。所提方法通信误差控制耗时约为60s,实验结果验证了所提方法在较短时间内将天线通信误差控制到最低。

多频与无线传感融合下的植保无人机通信系统研究

为进一步提高植保无人机的通信质量与整机作业效率,以多频与无线传感融合通信机理为出发点,针对其通信系统进行设计。在深入理解无人机作业特点与通信控制目标的基础上,侧重通信链路质量与数据收发成功率等关键指标,建立无人机多频无线传感通信模型,以通信系统多频与无线传感融合设计框架为依托,进行硬件选型与软件控制模块设计。多频无线传感融合通信试验表明:通信系统经合理调度及多频无线融合,通信误差率平均可保持在2.889%,整机一次作业完成时间效率提高了12.83%;作业过程各通信节点设置准确合理,整机工作效率可由传统无线式的89.90%提高到93.20%。该设计满足多频融合数据传输稳定、高效的作业要求,具有很好的参考价值。

基于延迟补偿的网联式自主驾驶车辆协同控制

针对智能交通领域多车协同驾驶中存在的通信信息乱序、丢包问题,研究网联式自主驾驶车辆协同控制技术,建立基于零阶保持(Zero Order Hold,ZOH)信息处理机制的自主驾驶车队控制模型,通过非线性系统状态估计算法进行延迟补偿,使得车队控制模型在复杂汽车行驶环境下保持有效。通过构建由多辆实车组成的网联式自主驾驶车队,在封闭道路环境下进行协同驾驶编队测试,结合网络传输及传感器数据进行模型仿真,验证了模型在实车编队环境下的稳定性、有效性和实用性。

PCCC for the performance improvement of the wireless optical communication system

In wireless optical communication, effects of scintillation make average Bit Error Rate （BER） deteriorate. To improve system performance,PCCC （Parallel Concatenated Convolutional Code） encoding scheme is employed,and upper bound on the bit error rate is given by considering the effects of scintillation,APD noise and thermal noise. Simulation results show that the POOC encoding scheme can relieve turbulenceinduced intensity fluctuations and the system performance is improved remarkably.

Performance Analysis and Parameter Optimizing Rules of LT Codes

As a new class of forward error correcting encoding algorithm,Luby Transform codes are suitable for the erasure channel environment based on the packet communication.The encoding,decoding algorithms and the implementation of LT codes are summarized in the paper.Meanwhile simulations of the ideal soliton distribution and robust soliton distribution are conducted to evaluate the performance of LT codes in terms of successful decoding probability,mean degree and decoding time over the erasure channel.The parameter optimization rules of LT codes are deeply discussed and proposed in the paper.The research results are of great practical importance for improving the real time performance in the erasure correction applications.

Novel multipath routing protocol integrated with forward error correction in MANET

In order to improve the data transmission reliability of mobile ad hoc network, a routing scheme called integrated forward error correction multipath routing protocol was proposed, which integrates the techniques of packet fragmenting and forward error correction encoding into multipath routing. The scheme works as follows: adding a certain redundancy into the original packets; fragmenting the resulting packets into exclusive blocks of the same size; encoding with the forward error correction technique, and then sending them to the destination node. When the receiving end receives a certain amount of information blocks, the original information will be recovered even with partial loss. The performance of the scheme was evaluated using OPNET modeler. The experimental results show that with the method the average transmission delay is decreased by 20% and the transmission reliability is increased by 30%.

ESSENTIAL INFORMATION AGGREGATION OF INTRA CODED VIDEO FRAME FOR WIRELESS TRANSMISSON

A novel error resilient method based on Essential Information Aggregation (EIA) technique is proposed for robust wireless transmission of intra coded video frames. This method modifies the original video stream structure so as to mitigate the effect of decoding loss of synchronization within a video frame, for which Macro Block Aligned (MBA) error detection method is accompanied to be developed. Experiments on an Additive White Gaussian Noise (AWGN) wireless simulation platform and H.263+ baseline video codec show that it can obtain better subjective and objective image quality than existing error resilience approaches.

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation(DPIM),it is difficult to analyze the error performances of Turbo coded DPIM.To solve this problem,a fixed-length digital pulse interval modulation(FDPIM) method is provided.The FDPIM modulation structure is introduced.The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM.Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel.The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM.However,FDPIM is easy to be implemented and easy to be combined.with Turbo code for soft-decision because of its fixed length.Besides,the introduction of Turbo code in this modulation can decrease the average power about 10 dBm,which means that it can improve the error performance of the system effectively.

COOPERATIVE ARQ PROTOCOL FOR CORRELATED WIRELESS CHANNELS

A novel Automatic repeat ReQuest (ARQ) protocol called cooperative ARQ is presented in this let-ter, where a relay terminal is requested to retransmit an erroneously received packet, instead of the source ter-minal. The data link layer Packet Error Rate (PER) performance of cooperative ARQ is derived in correlated wireless channel. The results show that even though the relay-destination channel is worse than the source-destination channel, the new protocol outperforms the traditional one as long as the average SNR of the relay-destination channel is better than a certain threshold. It is also demonstrated that a second order diversity gain can be achieved with the cooperative ARQ protocol.

Channel Arrangement for optical communication subsystems with 12 parallel channels

This paper devoted to report the design and the achievement of an optical communication subsystem with 12 parallel channels in one chip.The system is capable of transmitting 10 Gbps bidirectional date over hundreds of meters.It can provide error detection and correction by using 8B/10B encoding and Cyclical Redundancy Checking (CRC) encoding when only single-channel fails.The design scheme has already passed the simulation in FPGA.This technique is useful to enhance the capability and the reliability of the very short reach (VSR) transmission systems.

CLOSED-FORM ERROR RATES OF STBC SYSTEMS AND ITS PERFORMANCE ANALYSIS

The closed-form solutions for error rates of Space-Time Block Code (STBC) Multiple Phase Shift Keying (MPSK) systems are derived in this paper. With characteristic function based method and the partial integration based respectively, the exact expressions of error rates are obtained for (2,1) STBC with and without channel estimation error. Simulations show that the practical error rates accord with the theoretical ones, so closed-form error rates are accurate references for STBC performance evaluation. For the error of pilot assisted channel estimation, the performance of a (2,1) STBC system is deteriorated about 3dB.

Pairwise codeword error probability for coded atmospheric optical communication systems

To study the performance of various error-control coding schemes,exact expressions and upper bounds on the pairwise codeword error probability(PEP)for several modulation schemes(OOK,SC-BPSK,BPPM)used in atmospheric optical communication systems are derived.To simplify the computation,this research was under the assumption of weak turbulence.Moreover,by simulation of expressions,the performances of PEP in different modulation schemes are compared and the best one of them is given.

APPLICATION OF BEAM SEARCH FOR THE DECODING OF ONE CLASS OF LDPC CODES

For one class of Low-Density Parity-Check(LDPC)codes with low row weight in theirparity check matrix,a new Syndrome Decoding(SD)based on the heuristic Beam Search(BS),labeledas SD-BS,is put forward to improve the error performance.First,two observations are made andverified by simulation results.One is that in the SNR region of interest,the hard-decision on thecorrupted sequence yields only a handful of erroneous bits.The other is that the true error pattern forthe nonzero syndrome has a high probability to survive the competition in the BS,provided sufficientbeam width.Bearing these two points in mind,the decoding of LDPC codes is transformed into seekingan error pattern with the known decoding syndrome.Secondly,the effectiveness of SD-BS dependsclosely on how to evaluate the bit reliability.Enlightened by a bit-flipping definition in the existingliterature,a new metric is employed in the proposed SD-BS.The strength of SD-BS is demonstrated viaapplying it on the corrupted sequences directly and the decoding failures of the Belief Propagation(BP),respectively.

Multiple-Symbol Interleaved RS Codes and Two-Pass Decoding Algorithm

For communication systems with heavy burst noise, an optimal Forward Error Correction(FEC) scheme is expected to have a large burst error correction capability while simultaneously owning moderate random error correction capability. This letter presents a new FEC scheme based on multiple-symbol interleaved Reed-Solomon codes and an associated two-pass decoding algorithm. It is shown that the proposed multi-symbol interleaved Reed-Solomon scheme can achieve nearly twice as much as the burst error correction capability of conventional single-symbol interleaved Reed-Solomon codes with the same code length and code rate.

HIHO Decoding Algorithms of Turbo Product Codes for High Rate Optical Communications

This paper presents a new Hard-Input Hard-Output (HIHO) iterative decoding algorithm for Turbo Product Codes (TPC), and especially describes the BCH-TPC codes aiming to alleviate error propagation and lower error floor. This algorithm mainly emp hasizes a decision mechanism for bit-flips, which thoroughly evaluates four different aspects of the decoding process, properly weighs and combines their respective reliability measures, and then employs the combined measure to make a judgment with regard to whether any particular bit should be flipped or not. Simulations result in a very steep Bit Error Rate (BER) curve indicating that a high-level net coding gain can be expected with a reasonable complexity. The simplicity and effectiveness of this HIHO decoding algorithm makes it a p romising candidate for the application in future high-speed fiber optical communications.

Training sequence based channel estimation for indoor visible light communication system

Channel estimation is a key technology in indoor wireless visible light communications(VLCs).Using the training sequence(TS),this paper investigates the channel estimation in indoor wireless visible light communications.Based on the propagation and signal modulation characteristics of visible light,a link model for the indoor wireless visible light communications is established.Using the model,three channel estimation methods,i.e.,the correlation method,the least square(LS) method and the minimum mean square error(MMSE) method,are proposed.Moreover,the performances of the proposed three methods are evaluated by computer simulation.The results show that the performance of the correlation method is the worst,the LS method is suitable for higher signal to noise ratio(SNR),and the MMSE method obtains the best performance at the expense of highest complexity.

Experiment study of ATP system for free-space optical communications

To meet the requirement of high tracking angular accuracy for the acquisition, tracking, and pointing (ATP) subsystem of the free-space optical communication, and provide the basis for the further optical communication between maritime mobile platforms, the experimental system, which executing part for the fine tracking is voice coil motor with high frequency and good performance for error compensation, is established, and the whole system can be controlled by personal computer. A series of experiments has been done for the simulation target of different uniform speed, and the data of tracking error for fine tracking and coarse tracking are collected, analyzed and evaluateds separately, and the real-time optical power of communication laser is also collected. The result shows that standard deviation for ATP system tracking error increases with the increase of target speed, while the range of tracking error appears to be no order. Furthermore, communication link can be hold for a long time.

Performance analysis of relay-aided free-space optical communication system over gamma-gamma fading channels with pointing errors

The average bit error rate(ABER) performance of a decode-and-forward(DF) based relay-assisted free-space optical(FSO) communication system over gamma-gamma distribution channels considering the pointing errors is studied. With the help of Meijer's G-function, the probability density function(PDF) and cumulative distribution function(CDF) of the aggregated channel model are derived on the basis of the best path selection scheme. The analytical ABER expression is achieved and the system performance is then investigated with the influence of pointing errors, turbulence strengths and structure parameters. Monte Carlo(MC) simulation is also provided to confirm the analytical ABER expression.