Efficient modulation techniques for satellite telemetry—receiver design and performance evaluation

In this paper we address the design of the data demodulator for high-efficiency satellite communications suited for telemetry applications. We choose Gaussian minimum shift keying as the modulation format and analyse its relative merits with respect to the more traditional filtered offset quadrature phase-shift keying scheme, when applied to medium-to-high data rate telemetry. Our study encompasses both geostationary orbits and the more challenging low earth orbit scenarios, and investigates the acquisition and tracking performance of the receiver with the aid of computer simulations. In particular, we present design criteria leading to the development of efficient, low-complexity schemes for symbol timing and carrier phase/frequency recovery and we analyse the impact of these synchronization algorithms on the system performance. Next, we discuss the demodulator performance degradation when the transmitted signal is passed through on-board solid-state or travelling-wave-tube power amplifiers. The paper is concluded by a comparative analysis of the above modulation schemes, with special emphasis on their power and spectral efficiency.     

基于ATM的CSCW组通信的体系结构

高性能的ＣＳＣＷ应用是各类ＣＳＣＷ应用中最复杂的一类。它不仅要求多点之间多媒体信息的实时传输,还要求的控制及管理功能。本文给出一种新的基本ＡＴＭ匠高性能ＣＳＣＷ多媒体通信的体系结构。     

多媒体通信综述

本文在简述了语音、数据及视频等信息处理技术和传输、组网等网络技术的基础上,着重介绍了多媒体通信业务的应用,主要包括;视频电子信箱,远程医疗诊断、计算机辅助设计,数字网络图书馆,多媒体会议系统,高清晰度图像系统和视频点播等。文章最后还简单介绍了国内外多媒体通信业务发展的情况。     

今天的网络孕育太比特的未来

太比特网络时代已为期不远,电信运营商的网络设施准备总超前于需求,他们已开始考虑当前网络建设和演进如何向未来太比特网络的平滑过渡。中国电信、Ｑｕｅｓｔ、Ｌｅｕｅｌ３Ｃｏｍｍｕｎｉｃａｔｉｏｎｓ等公司利用北电网络的方案和产品建设和优化了自己的网络。而光网络产品功能的不断演进和技术的突破正在为向未来端到端全光网演进清除障碍。     

Multiple Relay Selection Based on Game Theory in Cooperative Cognitive Radio Networks

Due to the inefficiency of traditional fixed spectrum allocation policies, the paradox of apparent spec-trum scarcity occurs while most of the bands are under-utilized. This has prompted proposals for Dynamic spec-trum sharing (DSS), which explains why Cognitive radio network (CRN) has been widely accepted as a promising approach to settle inefficient usage of scarce available radio spectrum. As a subset of DSS, Dynamic spectrum leasing (DSL) strategy has been proposed based on game idea, where Primary user (PU) has an incentive to allow Cog-nitive users (CUs) to access its licensed spectrum for a fraction of time in exchange for revenue. This paper pro-poses an approach, named multiple relay selection based on Game theory (GTMRS), to optimize the utilities of PU and CUs as a whole, where a pricing-based spectrum leas-ing mechanism is applied. While the parameter price c is jointly determined by PU and CUs, all selected cognitive user's optimal cooperative powers can be satisfied through a non-cooperative game among themselves. Numerical re-sults show that more CUs are involved in the cooperation and both utilities of PU and CUs as a whole are improved, which means the whole system throughput is increased.     

基于矩生成函数的协同中继传输误符号率性能分析

多中继协同分集技术在慢衰落无线环境下可以提供巨大的性能增益。该文从接收端平均误符号率的角度,分析了独立的瑞利衰落信道下,采用放大转发的多中继协同最大比合并检测方案和多节点侦听,单中继转发的机会中继方案的性能;并基于矩生成函数推导出两种方案下M-PSK和M-QAM调制信号平均误符号率的闭合表达式。经蒙特卡罗仿真验证,该表达式在中高信噪比下与仿真的实际结果非常吻合。同时也可以看出机会中继的分集增益与协同侦听的节点数成正比,误符号率性能优于使用最大比合并检测的多中继协同方案。     

一维无线传感器网络分簇通信方案能量效率研究

为了提高无线传感器网络的能量有效性,该文在分析基于分簇的传统方案和协作分集数据传输方案的能量效率基础上,提出了一维传感器网络分簇多用户分集数据传送方案(CMDDTS)。理论分析表明能量开销依赖于数据融合比、簇内通信的发送功率、簇间通信的接收功率以及电路消耗的功率和簇内传感器的数目,仿真结果验证了所提方案的能量效率优于传统方案和协作分集数据传送方案。     

随机射线的概率分布及其应用

在使用随机射线方法建模无线传播信道时,需要求解以反射次数为指标的无线电波经过若干次反射以后达到特定位置的概率分布。该文使用信息论中的最大熵原理,首先计算在Manhattan距离度量下二维和三维空间连续情形和离散情形下随机射线的概率密度函数。然后计算在Euclid距离度量下二维和三维空间连续情形下随机射线的概率密度函数,以及作随机游动的随机射线在二维空间的概率密度函数。使用城市密集传播地区的测量数据验证随机射线理论模型结果的可靠性。所得结果对于无线随机传播信道建模具有理论指导意义。     

基于网络编码的协作HARQ协议

该文基于网络编码技术提出了一种新的协作HARQ协议。在中继节点的协助下两个用户与基站进行通信。中继节点响应基站的重传请求,对两用户的增加冗余帧采用物理层网络编码即信号重叠调制技术进行处理,然后发送至基站。基站对接收信号采用多用户联合检测以及联合软判决译码。在平坦瑞利衰落信道下,该网络编码协作HARQ协议较传统的非协作HARQ协议可获得较大的性能改善,其性能接近没有采用网络编码的协作HARQ协议,且需要较少的硬件和带宽资源。     

异构无线通信系统的融合机制和协同功率分配算法研究

该文提出了一种基于协同通信和无线中继技术的融合机制,以实现异构无线接入网的互联互通和融合。为了最大化所提异构协同网络方案的协同容量,从理论上给出了协同功率分配优化理论模型,并介绍了一种不同于传统注水理论的基于效用函数的协同功率分配算法,该算法在合理设置发射功率保证第1跳和第2跳链路的传输速率匹配的前提下能够优化系统性能。仿真结果表明所提协同功率分配算法有显著的性能增益。