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CT-TCM的CSI自适应编码调制技术

自适应编码调制技术已成为高速无线数据通信的一项关键技术.文中介绍了自适应编码调制技术,包括它的分类及特点.介绍了CT-TCM的基本原理和优点,设计了一种基于CT-TCM码的自适应编码调制通信方案,该方案能够以较低的复杂度提高系统频谱利用率.     

基于非编码信息匹配的自适应Turbo TCM编码调制方案

本文提出了一种通过调整非编码信息量,并与信号映射相结合来改变编码、调制模式的自适应Turbo TCM编码调制方案,称之为基于非编码信息匹配的自适应Turbo TCM编码调制方案.由于将Turbo码和TCM编码调制技术相结合得到的Turbo TCM编码调制方案的带宽效率高,所以,在慢时变无线衰落信道中,自适应Turbo TCM编码调制的平均频谱效率也将很高.给出了该方案的工作原理、设计方法,并通过蒙特卡洛(Monte Carlo)仿真研究了该方案的性能.与现有编码调制方案相比,该方案具有频谱效率高、易于设计和实现的优点.     

宽带卫星通信中的ACM技术

采用自适应编码调制技术(ACM)的卫星数字视频广播新标准(DVB-S2)应用到宽带卫 星通信网中,将极大提升系统吞吐量,提供更丰富的交互式业务。从实际应用的角度,分析 了ACM的控制机制并提出其编码调制方案的简化方法。仿真结果表明,在几乎不影响系统性 能的前提下,该方案可以大幅降低ACM机制的复杂度。     

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.     

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。     

New Approach for Optimized Resources Allocation in DVB- S2 Networks

自适应编码调制技术根据信道环境自适应地调整传输参数来提高频谱效率,但是卫星网络中信道的时变特征对该技术的使用造成了一些限制.提出一种基于预测的信噪比估计算法,来应对回路延时带来的不利影响.在预测值基础上,提出一种新的编码调制方案选择算法来选择更强健的编码调制方案.最后,提出一种滑动窗口技术来应对编码调制方案的频繁转换及其引起的系统性能振荡.仿真结果表明,新方案能够使网络资源得到更有效的利用.     

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.     

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。     

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。     

Performance analysis of a rate-adaptive dual-branch switched diversity system

In this letter, a performance analysis of a dualbranch switched diversity system operating on statistically independent and identically distributed Nakagami-m flat-fading channels is presented. An adaptive coded modulation (ACM) scheme is employed to increase the spectral efficiency of the system. The ACM scheme consists of a set of multidimensional trellis codes originally designed for additive white Gaussian noise channels, where the codes are based on quadrature amplitude modulation (QAM) signal constellations of varying size. The performance is evaluated by assuming perfect channel knowledge at both transmitter and receiver and instantaneous feedback of channel state information, conveyed from the receiver to the transmitter on an error-free feedback channel. The optimal switching threshold of the switched diversity combiner, maximizing the average spectral efficiency, is identified for spatially uncorrelated antenna branches.     

Impact of channel prediction on adaptive coded modulation performance in Rayleigh fading

Adaptive coded modulation (ACM) is a promising tool for increasing the spectral efficiency of time-varying mobile channels while maintaining a predictable bit-error rate (BER). An important restriction in systems with such a transmission scheme is that the transmitter needs to have accurate channel-state information (CSI). Earlier analysis of ACM systems usually assumes that the transmitter has perfect knowledge of the channel or that the CSI is accurate but outdated. In this paper, we investigate the effects of predicting the CSI using a linear fading-envelope predictor in order to enhance the performance of an ACM system. For the case in which multidimensional trellis codes are used on Rayleigh-fading channels, we obtain approximative closed-form expressions for BER and average spectral efficiency. Numerical examples are given for the case of Jakes correlation profile and maximum a posteriori-optimal predictor coefficients.     

Turbo‐coded APSK modulations design for satellite broadband communications

This paper investigates the design of power and spectrally efficient coded modulations based on amplitude phase shift keying (APSK) modulation with application to satellite broadband communications. APSK represents an attractive modulation format for digital transmission over nonlinear satellite channels due to its power and spectral efficiency combined with its inherent robustness against nonlinear distortion. For these reasons APSK has been very recently introduced in the new standard for satellite Digital Video Broadcasting named DVB‐S2. Assuming an ideal rectangular transmission pulse, for which no nonlinear inter‐symbol interference is present and perfect pre‐compensation of the nonlinearity, we optimize the APSK constellation. In addition to the minimum distance criterion, we introduce a new optimization based on the mutual information; this new method generates an optimum constellation for each spectral efficiency. To achieve power efficiency jointly with low bit error rate (BER) floor we adopt a powerful binary serially concatenated turbo‐code coupled with optimal APSK modulations through bit‐interleaved coded modulation. We derive tight approximations on the maximum‐likelihood decoding error probability, and results are compared with computer simulations. The proposed coded modulation scheme is shown to provide a considerable performance advantage compared to current standards for satellite multimedia and broadcasting systems. Copyright © 2006 John Wiley & Sons, Ltd.     

Impact of Spatial Correlation on Adaptive Coded Modulation Performance in Rayleigh Fading

A performance analysis of an adaptive coded modulation (ACM) scheme operating on identically distributed and spatially correlated Rayleigh flat-fading channels is presented. In particular, we study a single-input multiple-output system where spatial diversity is exploited at the receiver by using a maximum ratio combining scheme. The ACM scheme consists of a set of multidimensional trellis codes originally designed for additive white Gaussian noise channels, with codes being based on quadrature amplitude modulation signal constellations of varying size. Rate adaptation is achieved by providing the transmitter with channel state information as predicted by the receiver. Approximate closed-form expressions for the average bit error rate and the average spectral efficiency are derived, and numerical examples are given for the case of Jakes correlation profile and maximum a posteriori optimal predictor coefficients     

超窄带通信调制技术研究

在分析超窄带通信中的关键技术一具有高频带利用率的双向编码调制方式:可变相移键控(VPSK),甚小频移键控(VMSK)的基础上重点讨论了1/2甚小频移键控(VMSK/2)调制方式的编解码原理,并给出了其频谱的数学表达式和计算机仿真频谱图.对VMSK/2信号的频谱利用率和误码率作出初步估计,给出了VMSK/2无线数字传输系统模型,并对近似零群时延滤波器进行了初步分析.     

宽带无线网络中的自适应编码调制技术研究

由于自适应编码调制技术在宽带无线网络中对于改善频谱利用率和增加数据速率来说是一项能力很强的技术,因此本文针对刚提出的CT-TCM技术,将其与RCPT和ARQ技术结合起来,讨论了一种新的自适应编码调制方案.并对实现该方案的一些具体细节进行了详细的阐述.     

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。