基于平均频谱效率的自适应编码调制优化设计

自适应编码调制(ACM)技术能够很好地改善无线信道的频谱利用率.文中提出了一种基于平均频谱效率的自适应调制编码系统的优化方案,运用该方案,ACM系统需要数量很少的优化编码,使吞吐量接近于AWGN信道容量.     

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。      

自适应编码调制技术在DVB-S2中的应用

阐述DVB-S2中自适应编码调制技术(Adaptive Coding Modulation,ACM)的原理,介绍DVB-S2自适应编码调制技术在IP单播中的具体应用,并分析影响ACM性能的因素.     

ACM技术在DVB-S2 IP单播系统中的应用

研究并阐述了DVB-S2系统交互式应用中IP单播采用的自适应编码调制(ACM)技术,介绍了ACM的基本原理及实现过程,给出采用ACM的IP单播系统流程.     

刍适应编码调制技术在DVB—S2中的应用

阐述DVB—S2中自适应编码调制技术（Adaptive Coding Modulation，ACM）的原理，介绍DVB—S2自适应编码调制技术在IP单播中的具体应用，并分析影响ACM性能的因素。     

卫星通信网中ACM技术研究

针对现有卫星通信网传输效率不高的问题,讨论了自适应编码调制(ACM)技术在卫星通信中的应用。提出了在点对点和TDM/TDMA(FDMA)组网方式下的编码调制的自适应调整策略和自适应调整门限值的计算方法,给出了中心站网管控制下的自适应调整流程;并通过重新设计2种应用方式下的调制信号帧结构,结合现有的突发解调技术,可以实现信号的自适应解调。     

ACM技术在卫星通信IP网互联中的应用

自适应编码调制(ACM)技术根据信噪比自适应改变编码和调制方式,可将链路余量自动转换为链路传输能力,从而提高无线信道的频谱利用率。为解决卫星通信中IP化传输对电路带宽需求增加的问题,提出了应用自适应编码调制技术进行IP网互联的方案,通过对DVB-S2_ACM与VersaFEC_ACM两种不同技术的性能比较,分析了VersaFEC_ACM技术在岸船卫星通信IP网互联中应用的可行性及工作过程。链路计算与性能比较结果表明,该技术的应用可使岸船间原有的1 024 kb/s电路带宽利用率提高95%,同时抗信道衰落的余量提高6 dB,能够提高卫星通信资源利用率和系统可用度。研究结果可为后续工程应用提供参考。     

极化码在LTE系统中的应用

为了实现极化码在LTE系统中的应用,提出了两类LTE系统中的极化码编码调制方案:联合极化编码调制(MLC-PCM)方案和比特交织极化编码调制(BIPCM)方案.其中,MLC-PCM方案凸显了通信系统中联合极化设计对系统性能提升的重要作用.此外,由于极化码的编码码长不一定为2的幂次,因此提出了一套简单易行且性能优异的极化码速率适配打孔方案,使得极化码的码长可以任意变化.最后,将极化编码调制方案与LTE系统Turbo码编码调制方案在所有MCS等级上进行了对比,仿真结果显示,在所有MCS等级上,极化编码调制方案都有明显性能增益.     

宽带卫星通信中的DVB-S2

新的数字视频卫星传播标准（DVB-S2），应用到宽带卫星通信中，将极大地提升系统容量，提供更多的宽带交互式业务。本文分析了DVB-S2中ACM（自适应编码调制）的工作机制，并指出了DVB-S2具有良好的后向兼容性。     

PolarSat公司推出新一代卫星通信网络

2月10日，加拿大PolarSat Inc．公司宣布已在VSATPlus3产品上成功实现了全网状自适应编码／调制（Mesh—ACM）技术。Mesh—ACM技术可以同时提供卫星链路高可用性和卫星带宽最佳利用。尽管自适应编码／调制（ACM）技术已在基于星状网的DVB—S2系统中得到了广泛的使用，但一直未能在复杂的网状网系统中实现。     

基于DVB_S2X标准的自适应传输控制技术

针对天地一体化信息网络中星地间高速、高效数据自适应传输需求,在宽带卫星通信 DVB_S2X 标准的基础之上,开展高效自适应传输控制技术研究,包括高精度信道估计、低延时信道状态预测与自适应编码调制选择切换策略等关键技术,满足自适应编码调制技术(ACM) 的使用要求。并完成典型模拟环境下高效自适应传输控制技术的测试验证,为后续宽带通信卫星系统、星地高速数据传输系统以及天地一体化信息网络的构建奠定技术基础。实验结果表明,该方法可以在不同信道条件下都保持最大的传输效能,大幅度提高系统的频谱效率和数据吞吐量。     

A generalized Chinese remainder theorem-based proactive multi-secret sharing scheme for global wide area network

Adaptive communication for is one of the hottest areas of research in the telecommunication systems including wireless broadcast systems. This is primarily accomplished for sake of boosting the transmission throughput with enhanced quality of service and ideal link utilization. In adaptive communication, various radio transmission parameters like modulation symbol, code-rate and power etc. are carefully chosen according to the erratic channel state information on the link. Digital video broadcast—second generation (DVB-S2) has an inbuilt support for adaptive coding and modulation (ACM). However, power adaptation is still a necessity because of power constraint in downlink where satellite has a limited power bank. Moreover, different downlinks have distinct transmit power requirements due to diverse ambient on earth receivers like rainy, foggy, stormy and with clear sky etc., hence flat transmit power distribution among all the ground receivers may not be a good idea at all. To utilize the ACM feature in DVB-S2 and to additionally adapt power, in this paper, an adaptive modulation, coding (MODCOD) and power scheme is proposed. By investigating a fuzzy system and differential evolution algorithm, to select the set of MODCODs and optimum power vector, respectively, for the next transmission interval. From the simulation results it is apparent that the proposed scheme is promising in terms of efficient link and transmit power utilization as well as quality of service compared to the schemes in the literature with flat power distribution.

     

Adaptive coding and modulation for satellite broadband networks: From theory to practice

This paper presents the detailed design and the key system performance results of a comprehensive laboratory demonstrator for a broadband Ka‐band multi‐beam satellite system exploiting the new DVB‐S2 standard with adaptive coding and modulation (ACM). This complete demonstrator allows in‐depth verification and optimization of the ACM techniques applied to large satellite broadband networks, as well as complementing and confirming the more theoretical or simulation‐based findings published so far. It is demonstrated that few ACM configurations (in terms of modulation and coding) are able to efficiently cope with a typical Ka‐band multi‐beam satellite system with negligible capacity loss. It is also demonstrated that the exploitation of ACM thresholds with hysteresis represents the most reliable way to adapt the physical layer configuration to the spatial and time variability of the channel conditions while avoiding too many physical layer configuration changes. Simple ACM adaptation techniques, readily implementable over large‐scale networks, are shown to perform very well, fulfilling the target packet‐error rate requirements even in the presence of deep fading conditions. The impact of carrier phase noise and satellite nonlinearity has also been measured. Copyright © 2009 John Wiley & Sons, Ltd.     

CSMA local radio networks with BPSK modulation in Rayleigh fading channels

Calculation of the throughput of a carrier sense multiple access (CSMA) packet radio network with capture over slow Rayleigh-fading channels is presented. The effects of capture on the throughput of the system are related to the modulation and coding technique of the transmission system, the general distribution of terminals in the area and the length of the transmitted packets. BPSK modulation and BCH coding are considered.<>     

Throughput-Optimal Multi-Mode Precoding MIMO System with Per-Substream AMC

In this paper, we study a multi-mode quantized precoding multiple-input multiple-output (MIMO) system with per-substream adaptive modulation and coding under a maximal throughput target. An analytical throughput expression is firstly presented by recurring to Gaussian mixed approximation for block error rate of Turbo codes. An optimal mode-MCS (modulation and coding scheme) selection algorithm is then developed to achieve maximal throughput performance based on throughput criterion. Further, a complexity-reducing selection algorithm with negligible performance loss is proposed by making full use of the information provided by singular value decomposition of the instantaneous channel matrix at the receiver side. Simulation results show that both selection algorithms can achieve good throughput performance in the above mentioned MIMO system.     

Adaptive Coding and Modulation for the DVB-S2 Standard Interactive Applications: Capacity Assessment and Key System Issues

Point-to-point multibeam satellite systems based on the DVB-S standard are currently designed for link closure in the worst-case propagation and location conditions. The DVB-S standard, conceived for broadcasting applications, considers a fixed coding rate and modulation format that are selected according to the assumed coverage and availability requirements. This approach implies the occurrence of high margins in the majority of the cases, when interference and propagation conditions allow for higher signal-to-noise-plus-interference ratio. The adaptive coding and modulation (ACM) introduction in the new DVB-S2 standard for the interactive service profile opens up a number of appealing opportunities for the design and development of satellite broadband networks. In this article we show how the ACM introduction in the satellite downlink enables greatly enhanced system performance but also has a profound impact on the way the system and some of the key system components are designed.     

5G通信中的极化码在高阶调制下的应用

极化码作为信道编码领域的一类新型编码方案,已经被确定为5G移动通信系统中增强移动宽带(Enhanced Mobile Broadband,eMBB)场景下控制信道的编码方案。为了提高5G通信中的频带利用率和信息传输速率,提出将极化码与高阶调制技术相结合,针对16QAM和256QAM两种调制方式,建立和仿真了基于极化码的高阶调制通信系统。在加性高斯白噪声(Additive White Gaussian Noise,AWGN)信道模型下采用逐次消除(Successive Cancellation,SC)译码算法对不同参数的极化码进行仿真比较。仿真结果表明,在现有5G标准控制信道的16QAM模型下,码长N=1024,码率R=1/3,信噪比Eb/N0=6 dB时,极化码误码率可以达到10^-5。未来极化码的应用将推广到数据信道,在256QAM调制方式下,也体现出较好的纠错性能;在16QAM调制方式下,将极化码与同等速率的LDPC码及卷积码相比较,性能增益也有良好的体现。     

LTE系统中自适应调制编码技术的研究

根据标准研究了LTE系统的自适应调制编码技术,并针对该系统提出了自适应调制编码技术的实现方案。在LTE系统环境下仿真了提出的实现方案的性能,结果表明：无论在高信噪比还是在低信噪比条件下,自适应技术均比单一的编码调制方案吞吐量有明显的提升,该自适应实现方案在保证一定的通信可靠性的前提下,能够更有效地利用频谱资源和提高系统吞吐量。