多元速率兼容LDPC码的自适应编码调制系统研究

本文设计了一种基于有限域GF(q)上的多元速率兼容LDPC (RC-LDPC) 码结合高阶调制的自适应编码调制(Adaptive Coded Modulation, ACM) 系统。并提出了多元RC-LDPC码在独立和相关衰落信道下的增量冗余型自适应编码调制方案。本方案中多元LDPC码码率从1/3到5/6灵活变化,以较低的系统复杂度,有效提高了系统的频带利用率。仿真结果表明:随着系统吞吐率提高,多元ACM系统相对于二元ACM系统具有越来越明显的编码增益,最高可达约9 dB。      

基于链路自适应的遥感数据传输技术研究

为提升遥感卫星数据传输的效率,针对传统遥感卫星数据传输中固定速率存在链路资源未充分利用的问题,研究基于链路自适应的遥感卫星数据传输技术,提升链路资源利用率。仿真计算结果表明,在星上发射功率和传输带宽不变的情况下,与传统方式相比,遥感卫星过境期间的数据传输量提高了2.62倍。     

TCM数据传输系统的自适应均衡

介绍两种要吧有效地用于财制（ＴＣＭ）数据传自应均衡技术，即交织判决反馈均衡（ＩＤＦＥ）和降态序列估值（ＲＳＳＥ）。最后对它们的性能进行了评价。     

基于LDPC码的SW速率自适应对称编码方法

为达到SW速率界限上的任何一点,关注分布式信源编码的设计.首先对伴随式编码进行了介绍,然后提出了一种实际解决方法:基于LDPC的伴随式打孔的编码方法实现编码的速率自适应.实验表明,此方法具有很好的编码性能且更接近SW码率界限.     

高码速率遥感卫星LDPC译码模块设计

随着遥感技术的飞速发展,遥感数据的传输速率和编码性能要求越来越高。在高码速率、复杂编码的条件下,设计符合国际空间数据系统咨询委员会(CCSDS)标准的高码速率解调器成为解决遥感卫星数据解调的关键。在软件无线电平台的解调器结构下,分析低密度奇偶校验码(LDPC)译码特点,完成译码模块结构、解调速率、存储规则的设计。设计结果满足高码速率遥感卫星解调器要求,提高了数据的下传效率和空间资源的利用效率。     

基于无率纠错码和高阶QAM调制的收端速率自适应方案

现有的自适应解调方案中调制阶数最高仅限于16,且方案分析和设计中没有考虑信道编码的译码环节.本文研究适用于高阶QAM的自适应解调算法,并结合无率纠错码提出一种收端速率自适应方案.接收端有多种解调模式,每种解调模式删除一个符号中不同数量的、似然比绝对值最低的几个比特,以提高解调比特的可靠度和平均互信息.从互信息分析的角度,得到在满足要求的译码误码性能时,译码所需要的码字长度的理论结果,进一步给出在译码复杂度约束条件下解调模式的选择方案.以256-QAM调制星座和Raptor码为例对方案进行了仿真,验证了理论分析的正确性和方案的有效性.     

卫星信道自适应传输技术研究

卫星通信由于信道条件开放,会受到各种大气因素的影响,为了提高数据传输的速率和可靠性,并在有限的频带资源下提供更高的频谱效率,自适应传输技术已逐步成为卫星通信领域的研究热点之一。文章首先介绍了卫星通信基本原理;然后深入研究了自适应编码调制技术的原理和关键技术。研究结果表明,相对于传统传输系统,基于自适应技术的传输系统在误比特率和数据吞吐量性能上有明显的改进。     

一种基于LDPC码的SW速率自适应对称编码方法

为达到SW速率界限上的任何一点,本文关注于分布式信源编码的设计。首先对伴随式编码进行了介绍,然后提出了一种的实际解决方法：基于LDPC的伴随式打孔的编码方法实现编码的速率自适应。实验表明,此方法具有很好的编码性能且更接近SW码率界限。     

无速率编码及其应用综述

纠错编码技术通过引入冗余增加可靠性,是现代通信的关键技术之一。无速率编码是一类新兴纠错编码,其速率可以根据信道状态自适应改变,编译码算法较为简单,且性能优异,可以适用于不同的应用场景,因此受到了国内外学者和工业界的关注。介绍了4种经典或新兴的无速率编码方案,包括卢比变换(Luby Transform,LT)码、Raptor码、在线喷泉码(OFC)和BATS(Batched Sparse)码。介绍无速率编码的基本原理,通过其发展过程比较不同无速率编码的特点。阐述了这些无速率编码的编译码方法,并简要介绍其最新的研究进展。最后,介绍无速率编码在广播通信及不等差保护、无线传感器网络、车联网、存储以及分布式计算等新老场景中的应用。无速率编码是一种复杂度低、灵活度高的编码,随着新型无速率编码的发展,在未来的分布式系统等场景中将会有更广泛的应用。     

基于Turbo乘积码的自适应编码调制技术研究

随着高速无线数据通信的发展,自适应调制技术逐渐成为业界研究的热点之一。研究了MQAM自适应调制技术,分析了自适应调整区间的划分方案,设计了基于Turbo乘积码的自适应编码调制方法,提高了系统的频谱利用率。     

一种遥感卫星高码速VCM数传信道的均衡技术

在基于第二代数字卫星视频广播协议（DVB-S2）标准的遥感卫星可变编码调制（VCM）高码速数传信道中,宽带信号的大失真、大频偏和低信噪比会导致解调器载波环路不锁定。传统的DVB-S2解调器并不能解决这个问题。在载波环路前增加一个均衡器补偿失真,可以让载波环路稳定锁定。为了克服载波环路前信号的频偏和相偏对均衡器的影响,提出了一种均衡技术,利用起始序列（SOF）和导频的先验信息进行双重自相关变换,设计了一种新的误差函数和迭代过程。仿真结果表明,该均衡技术可在该应用条件下支持解调稳定工作。     

多跳分集系统中一种新的基于无比率编码的跨层方案

研究了多跳分集系统中由于链路的不可靠传输直接应用实用网络编码存在差错的扩散和传播问题.提出了一种新的基于无比率编码的跨层方案,该方案利用无比率编码的纠错能力及实用网络编码码字随机特性,控制了输入链路的差错扩散和传播.结果表明,在满足每条链路误包率一定的情况下,该方案获得了较好的差错性能.进一步分析了为了使每条链路达到给定的误包率,无比率编码在不同信噪比下的冗余.     

基于云计算的多源遥感数据服务系统研究

在分析了遥感影像数据及数据使用现状的基础上,综合考虑了云计算技术在遥感应用领域使用的必要性和可行性,设计了基于云计算的多源遥感数据服务系统。阐述了基于云计算的多源遥感数据服务系统体系结构及关键业务流程,包括遥感数据云存储、遥感数据云处理、遥感数据应用服务及遥感业务注册组装等。最后,通过原型系统的实现验证了系统设计既能保护原始数据的安全,又能降低数据使用的成本,同时还能够提高数据的共享率和用户使用率。     

端元匹配的遥感影像地物自适应光谱表征

光谱信息是遥感识别地物的依据,而目前已发展的典型地类的光谱指数模型有限,波谱库中的标准地物类型及其普适性也是有限的.鉴于此,提出一种端元匹配的地物自适应光谱表征方法,通过选取贴合影像本身的端元,并综合光谱角和距离度量对影像和端元光谱进行综合匹配.通过ETM+(Enhanced Thematic Mapper)影像上对植被、水体与美国地质调查局(United States Geological Survey,USGS)波谱库及归一化植被/水体指数的对比实验,及阴影、裸地等的验证实验,证实了该方法的有效性和普适性.     

Adaptive code symbol assignment in a rateless coded multichannel cognitive radio network

Because of its robustness to packet loss and adaptivity to channel conditions, rateless codes have been used in cognitive radio networks to improve the secondary system performance. In this paper, we investigate an adaptive code symbol assignment scheme for the secondary user (SU) in a multichannel cognitive radio network based on rateless coding. In particular, the SU transmitter first encodes its information data through rateless coding and then assigns the unceasingly generated code symbols adaptively to each available channel obtained by spectrum sensing. Thanks to the forward incremental redundancy provided by rateless codes, it is unnecessary for the SU receiver to request the retransmission of lost symbols and the code symbols collected from any channel at any time contribute to the final data recovery. With an alternating channel occupancy model of the primary user (PU), we conduct a weight enumerator analysis to derive the optimal number of code symbols to be assigned to each available channel, thus to maximize the system throughput while protecting PU from interference. Both theoretical analysis and numerical results demonstrate the good performance of our proposed scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

A novel rateless codes design scheme based on two‐stage encoding and forward equal probability

This paper proposes an ideal rateless codes model to comprehensively describe rateless codes and extends the definition of systematic linear block code to generalized systematic code. Under the proposed model, average delay, maximum disorder, and uniformity recovery entropy are introduced as performance indices to design efficient rateless codes. A novel coding scheme based on two‐stage encoding and forward equal probability is proposed to optimize the proposed indices. In the first stage, the first k symbols are encoded, aiming to improve the performance of order recovery, uniformity recovery, and transmission efficiency as much as possible. In the second stage, the remaining infinite symbols are encoded, where the symbols with high degree are used to compensate the symbols loss in the first stage. Simulation results show that the proposed scheme can achieve generalized systematic rateless codes with high probability and also has less average delay and maximum disorder, better capacity achievability, and uniformity recovery performance than Luby trasform (LT) codes and rateless coded symbol sorting algorithm. Besides, the proposed scheme has the aforementioned advantages compared with expending window fountain codes except for uniformity recovery and maximum disorder performance when the erasure rate is higher than about 0.25. Copyright © 2013 John Wiley & Sons, Ltd.     

大批量数据远程传输的一种实现方法及其应用

提出了一种数据库系统的大批量远程数据传输方法,通过对数据进行打包、压缩及传输过程的优化处理,来实现远程大批量数据的高效传输,并应用到某医疗保险中心的数据远程传输系统中,取得了较好的传输效果。     

Optimization and realization of SWIPT relay channel transmission rate based on rateless code

The optimization of the transmission rate and implementation of the simultaneous wireless information and power transfer in a relay system were studied.In a three-node two-hop system,the decode-and-forward protocol was employed by the relay node.One transmission period was divided into two phases.The first phase was the simultaneous transmission of the information and energy from the source to the relay.The received signal at the relay node was split to two parts.One part was used for information decoding,and the other was converted into energy for information forwarding in the second phase.In the second phase,the information was forwarded according to the decode-and-forward protocol by the relay.The power splitting factor was optimized to minimize the total time of the two hops for the transmission of a certain amount of information when the durations of the two hops were unequal.Furthermore,Raptor codes were combined with different modulation modes to realize different transmission rates on the two hops for the efficient utilization of the different channel capacities in the two hops.The selection mechanism of the codeword length of Raptor codes and modulation mode was given.The simulation proves that the two hops with unequal durations can achieve a higher throughput,and the capacity of the relay channel can be efficiently used by employing Raptor codes,and an efficient and reliable transmission is realized.     

频率复用高码速率遥感卫星数据接收系统设计

针对双圆极化频率复用、高码速数据接收等关键技术,分析了影响系统交叉极化鉴别率、高码速数据接收链路误码性能的主要环节,提出了天馈、高码速数据接收链路的体系结构和设计方案.据此设计并建成的频率复用高码速率遥感卫星数据接收系统已成功接收了国内首颗双圆极化频率复用遥感卫星(“资源三号”卫星,数据速率450 Mbit/s×2)的...     

Research on application of variable coding modulation system based on Digital Video Broadcasting ‐ Satellite ‐ 2nd Generation in data transmission of near‐earth remote sensing satellite

In order to make full use of the link resources for data transmission from near‐earth remote sensing satellites, variable coding modulation (VCM) system is used to fully utilize the system link margin to improve the satellite data transmission performance. By analyzing the dynamic link under the VCM data transmission system, the contribution of the VCM system to the satellite data link optimization is studied from the perspective of engineering application, which can provide reference for the data link design of remote sensing satellites. Applying the flow design, for the currently adopted transmission system of X band, compared with traditional constant coding modulation (CCM) system, the average link performance of VCM system can be increased by 42.1% in single‐station transmission mode and 53.3% in dual‐station relay mode through the exampled analysis.