Multidestination Protocols for Satellite Broadcast Channels

Two retransmission procedures, the go-back-N(GBN) scheme and the selective repeat (SR) scheme, have been analyzed for data transfer from one transmitter to many receivers. We consider transfer of error-controlled bulk data over a satellite broadcast channel. Two retransmission strategies, the dynamic retransmission group reduction (DRGR) technique and the fixed retransmission group (FRG) technique, are proposed. We study the GBN and SR schemes for both strategies. Analytic expressions are derived for the throughput performance of the GBN scheme and of the SR scheme with infinite resources, while discrete event simulation is used to estimate the throughput of the selective repeat scheme with finite resources. Only the SR scheme using the DRGR technique provides acceptable performance for high-speed bulk data transfer. For the DRGR technique, the throughput falls logarithmically with an increase in the number of receivers. In contrast, the throughput for the FRG technique falls exponentially with an increase in the number of receivers.     

Connection Management Protocols for Dynamic Lightpath Provisioning in Future WDM Networks

This paper investigates and compares the performance of two GMPLS-based distributed control and management protocols for dynamic lightpath provisioning in future IP networks. The first protocol is a global information-based link state approach that consists of both an integrated RWA algorithm and a signaling algorithm. Two triggering mechanisms for the LSAs update procedures are considered; one is periodic-based and the other is threshold-based. The second protocol is a local-information based fixed alternate link routing approach where the signaling protocol is closely integrated with the RWA protocols.     

MICRON—A Framework for Connection Establishment in Optical Networks

Traffic grooming in optical networks has gained significance due to the prevailing sub-wavelength requirement of end users. Optical networks get upgraded to the latest technology slowly with time with only a subset of nodes being upgraded to the latest technology. The networks are thus comprised of nodes employing heterogeneous switching architectures. In this paper, we develop a framework called Methodology for Information Collection and Routing in Optical Networks (MICRON) for connection establishment in optical grooming networks with heterogeneous switching architectures. We illustrate with examples the information that may be collected from the links, and operators that may be used to obtain information along a path. The information can be used to select a path dynamically depending on the network status. We complete the MICRON framework by providing a generic channel assignment procedure that could be employed to implement different channel assignment schemes. Various routing and channel assignment algorithms can be developed from the proposed framework. The framework may be easily implemented with simple traffic engineering extensions to the already existing routing protocols in the wide-area networks.     

无线传感器网络密钥建立协议的能耗分析

从密钥存储量负载、通信负载和节点能耗等方面,对三个具有代表性的密钥建立协议SPINS、Random Key Scheme和PeerSiz进行了能耗测试和分析,结果表明:尽管基于对称密码体制的密钥建立协议的能耗远小于基于公钥体制的协议,但是如果选择部署了合适的密码算法,如ECC-160,基于公钥体制的密钥建立协议也能够较好地适应无线传感器网络环境。     

一种认证协议防御拒绝服务攻击的设计方法

拒绝服务(DoS)攻击是一种阻碍授权用户正常获得服务的主动攻击,大量认证协议和密钥建立协议存在着不同程度的DoS隐患.本文提出一种新的解决方法,用于无可信第三方认证协议和密钥建立协议防御DoS攻击,该方法可动态调整DoS防御的强度,并可减少并行会话攻击,增强协议的安全性.     

TD-SCDMA系统终端RRC连接建立过程研究

第一部分介绍了TD-SCDMA系统终端RRC子层的功能模型及RRC的主要功能。第二部分描述了RRC子层的状态，各状态下的任务以及状态间的转换。最后详细描述了TD-SCDMA系统终端RRC连接建立的过程，包括建立过程的消息流图及子过程。     

基于LTE系统的终端RRC连接建立过程研究

文章首先介绍了LTE(Long Term Evolution)系统,然后描述了终端RRC(Radio Resource Control,无线资源控制)层的协议框架及主要服务功能,最后详细地说明终端RRC初始连接建立过程,包括RRC连接建立的消息流程图,MAC(Medium Access Control,媒介接入控制)层基于竞争解决的随机接入等过程.     

Min-SINR-Maximizing Wireless-Powered AF Relay for Multisource and Multidestination Networks

Wireless Personal Communications - This study considers a wireless-powered relay assisting multisource multidestination (MSMD) communication networks. Specifically, a beamforming and...     

提高LTE网络RRC连接建立成功率方法研究

LTE网络较2G、3G网络最大的优势在于为用户提供更高速率。然而无线小区资源是一个共享资源,在同一个小区里,因某些突发因素,当用户数逐渐增多时,每个用户获得的速率将逐渐下降。当用户超过系统容量时,可能导致部分用户无法接入,大量用户同时接入网络将可能出现RRC连接建立失败次数增多,导致RRC连接建立成功率降低、用户感知差。本文通过研究异频负载均衡、接入限制控制和大容量保障相关参数,总结出应对大量用户聚集场景,避免RRC连接建立失败的方法。     

A New Translation Procedure for the C-60M System

This paper proposes a new translation procedure which is based on a jumbogroup constitution for simultaneous multiplex transmission of telephone and videophone signals over a coaxial 60-MHz system and describes transmission characteristics of the C-60M system using the translation procedure. The translation procedure reduces group-delay distortion harmful to video transmission without changing telephone transmission capacity or without degrading telephone transmission characteristics. It is also capable of transmitting either 36 videophone signals with 1 MHz bandwidth or nine videophone signals with 4.3 MHz bandwidth.     

一种认证协议的检测模型

在分布式系统中,客户向对方证实自己的身份以及建立会话密钥已是非常重要,密码协议的实施就是达到这种目的的有效方法。但密码协议的设计容易出错。本文给出了一种密码协议分析和检测模型,该模型对密码协议的描述简单而且直观。在此模型中,协议被描述成状态变换系统,通过对系统状态的检测,能够发现协议中存在的泄漏。最后,给出了如何将改进的TMN协议模型化,并找出了一种新的攻击,同时,给出了TMN协议的进一步改进。     

LTE系统无线资源控制连接重建过程研究与设计

介绍了LTE系统及其接入网E-UTRAN网络分层结构,分析了LTE协议栈及其功能,重点研究了RRC连接重新建立过程、设计RRC的状态和此通信过程的消息序列图,最后对研究课题进行了总结分析和展望。研究表明,更好地完善RRC连接重建过程的处理方法对于LTE系统通信有着极其重要的作用,这也是LTE通信系统中需要研究的方向之一。     

Per-Antenna Power Constrained Transceiver Design for MIMO Multisource and Multidestination Amplify-and-Forward Relay Systems

Wireless Personal Communications - This study addresses the transceiver design method for multiple-input multiple-output multisource multidestination amplify-and-forward relay systems. The source,...     

A New Connection Admission Control for Spotbeam Handover in LEO Satellite Networks

Frequent spotbeam handovers in low earth orbit (LEO) satellite networks require a technique to decrease the handover blocking probabilities. A large variety of schemes have been proposed to achieve this goal in terrestrial mobile cellular networks. Most of them focus on the notion of prioritized channel allocation algorithms. However, these schemes cannot provide the connection-level quality of service (QoS) guarantees. Due to the scarcity of resources in LEO satellite networks, a connection admission control (CAC) technique becomes important to achieve this connection-level QoS for the spotbeam handovers. In this paper, a geographical connection admission control (GCAC) algorithm is introduced, which estimates the future handover blocking performance of a new call attempt based on the user location database, in order to decrease the handover blocking. Also, for its channel allocation scheme, an adaptive dynamic channel allocation (ADCA) scheme is introduced. By simulation, it is shown that the proposed GCAC with ADCA scheme guarantees the handover blocking probability to a predefined target level of QoS. Since GCAC algorithm utilizes the user location information, performance evaluation indicates that the quality of service (QoS) is also guaranteed in the non-uniform traffic pattern.     

A New Procedure for Calculating Varactor Q from Impedance Versus Bias Measurements

The reasons for preferring the impedance versus bias method of measuring varactor Q at high frequencies are pointed out. To circumvent the circuit loss problem, a rigorous procedure has been developed, based on the Weissfloch equivalent circuit of a lossy two-port network, for extracting the varactor junction Q. Parallel circuit loss is automatically corrected for, but correction for series loss requires substitution of a dummy shorted varactor. The procedure is described along with an actual example of its use at 64 GHz. Simulated examples are also worked out to illustrate the effect of the initial reactance in series with the varactor junction, and to demonstrate the numerical correctness of the procedure.     

基于四阶累量的MUSIC算法对阵元误差的稳健性分析

本文分析了基于四阶累量的ＭＵＳＩＣ算法（记作ＦＯＣ－ＭＵＳＩＣ），在实际阵元存在幅相误差时，对波达方向（ＤＯＡ）的估计性能，给出了大样本情况下的估计方差公式，并与基于协方差矩阵的标准ＭＵＳＩＣ算法作了比较。计算机仿真结果表明，本文给出的方差公式与实验仿真结果十分接近。文中还给出了利用高阶累量的方法可获得阵列有效孔径扩展的新解释。     

游戏式路由算法教学初探

＂计算机网络＂课程含有抽象性较强的路由协议的内容,本文精心构思、设计和实现路由游戏,将原理融入到游戏的各个环节,使学生在参与的过程中,主动探索和思考蕴含在协议背后的设计思想,从而达到知其所以然的目的。我们的教学实践表明,该方法简单易行,效果明显,能够方便的推广到工程类专业的网络类课程的教学实践中。     

全差分运放中共模反馈电路的一种新接法

提出一种新的连接方法,利用一个简单的差分对,通过与差分信号共用信号通路,实现共模反馈电路,比传统方法节省了晶体管.并给出使用了这个共模反馈电路的一个高速、高增益、二级全差分运算放大器的设计实例.给出了理论分析和HSPICE的模拟结果.其共模回路的开环增益72dB,单位增益带宽34MHz,相位裕度是70°,增益裕度12dB.