可信网络连接安全协议与访问控制体系设计

针对现阶段可信网络在连接与控制方面存在问题,分析现有可信网络实体功能、结构层次和接口协议,提出包含完整度量收集器在内的全新可信网络连接体系架构,重新设计以EAP-TNC数据包为核心的安全网络协议及访问控制体系。通过设置网络带宽、终端状态和可信等级等多项指标,对体系访问控制和连接性能进行实验测试。结论表明,可信网络连接安全协议和访问控制体系可使终端以安全可控的方式访问网络,具备良好的安全性和可用性。     

自适应p-持续CSMA/CD介质访问控制策略

针对IEEE802．3局域网介质随机访问协议l-持续CSMA／CD，在同一个冲突域内，它的性能在重荷载下有明显缺陷的问题，本文分析了p-持续CSMA／CD协议，提出了一种新的关于概率p的自适应算法。该算法基于对网络流量的分析，在OSI物理层通过信道信息量的在线实时检测，根据反馈控制的原理，在数据链路层动态地调整控制输入参数p，从而控制站点发送分组数据帧的行为，使信道处于最佳的传输状态，提高信道的效率。     

基于HFC-CATV网的媒体访问控制协议

通过引入“组群 (cluster)”的概念 ,提出一种适用于HFC CATV网络的媒体访问控制 (MAC)协议的新结构模型 ,并分析该协议的工作原理和实现机制。     

优先级与自适应PRMA协议的性能研究

本文对未来的第三代微蜂窝移动无线通信系统的多址访问协议进行了研究。研究了ＰＲＭＡ系统中同时存在高、低优先级话音终端的Ｐｐｒｍａ协议的性能。提出了话音终端具有自适应重发许可概率的Ａｐｒｍａ协议。利用系统仿真技术对协议的性能进行了估计。     

水声通信网络介质访问控制协议的设计与仿真

采用OPNET平台对水声通信网络节点模型与介质访问控制协议进行了设计与实现,并重点研究建立了基于忙时间改进网络分配向量帧冲突处理机制的水声通信网络协议——UMACAW。同时建立并测试了包含1个主节点与4个传感器节点的水声通信网络。仿真结果表明,MAC层采用UMACAW协议能更好地克服冲突,减少节点间端对端传输延时,从而获得更高水声通信网络的吞吐量。     

基于节点剩余能量及流量自适应的混合MAC协议

基于节点剩余能量和网络流量变化,文中提出了RA-ZMAC协议,在Z-MAC协议中加入了能量控制和流量自适应机制.当网络流量低时,时隙的一部分时间中节点将进入睡眠状态以节省能耗,随着流量增大,睡眠时间减少.当网络流量继续增大,节点工作到TDMA方式,实现了基于竞争到基于调度的信道接入的平滑转换.RA-ZMAC协议根据节点剩余能量和流量情况改变竞争窗口和退避时间,当节点流量大时增大竞争窗口;节点剩余能量越多,退避时间越短.     

基于流量总时延最小的并行LSP自适应流量分配

MPLS的引入使IP网络的流量工程成为可能.如何平衡两个标记交换路由器的多条并行显式标记交换路径上的网络流量,从而达到避免拥塞和优化网络性能的目的,是流量工程研究的一个重要课题.本文指出流量总时延最小是最有价值和最实用的流量工程优化目标,通过分析平均分组时延和网络负载的约束关系,证明了优化解的存在,解出了其数学结果,提出了一种自适应流量分配新方法,理论分析和仿真结果都表明该方法具有简单、快速、收敛性强等优点.     

波分复用访问控制（WDMA）协议

近年来波分复用访问控制（ＷＤＭＡ）协议的研究十分活跃，本文综述了这一领域的最新成果。新协议注意高速网络环境的特点，尽量减少节点处理量，降低光器件的要求，解决潜在的控制通道处理瓶颈等。其中不少协议成本低、结构简单、通道利用率高且时延小，为ＷＤＭＡ的实用化奠定了良好的基础     

无线传感器网络S-MAC协议研究

传感器节点能量受限,节能是传感器网络中媒体访问控制（MAC）协议设计的首要问题。采用周期性睡眠机制、自适应侦听机制、串音避免机制和消息传递机制可使得传感器媒体访问控制（S-MAC）协议在网络能耗和时延方面得到改进。对S-MAC协议的改进主要有两种方式：动态调整、区别控制包与数据包的发送条件进行发送。对无线传感器网络,要想设计出一种满足各方面要求的MAC协议是不现实的,可针对不同应用的要求,灵活采用不同的方式,设计出相应的协议。     

无线Mesh网络速率自适应算法研究

自适应速率选择是影响无线Mesh网性能的关键问题。提出了一种基于动态解调门限的速率自适应选择算法,该算法通过统计传输速率进行速率选择,能够针对不同信道环境对每种调制速率所需最小信噪比门限进行自动调整。同时,采用跨层设计思想,采用路由协议广播报文作为MESH设备间传输信噪比信息的载体,从而能够根据信噪比和传输成功率信息得到信道环境下的最佳发送速率。实际测试结果表明,所提算法能够在较短时间内选择出最佳速率,而且具有较低的抖动和稳定的吞吐量。     

Efficient medium access protocol for Internet of things applications

The recent progresses made in microelectronics and sensor networks led to the emergence of a new family of networks called Internet of things (IoT). Several factors may degrade seriously IoT applications performance and prevent the connected objects to accomplish out their services. One factor is the inability of medium access control (MAC) protocol, namely, DCF 802.11 function, to distinguish between different sources of frame losses. To address this problem, we propose in this article an improvement called MAC protocol with distinction between data losses (MAC‐DL), which consists mainly to consider the different sources of frame losses in the functioning of the backoff algorithm. After the evaluation of MAC‐DL performance, the results showed a better performance compared with MAC protocol with the original DCF 802.11 function and to 2 other protocols proposed in the literature. Our solution improved significantly the quality of service and the energy efficient for typical IoT scenarios.     

Enhanced binary exponential backoff algorithm for fair channel access in the ieee 802.11 medium access control protocol

The medium access control protocol determines system throughput in wireless mobile ad hoc networks following the ieee 802.11 standard. Under this standard, asynchronous data transmissions have a defined distributed coordination function that allows stations to contend for channel usage in a distributed manner via the carrier sensing multiple access with collision avoidance protocol. In distributed coordination function, a slotted binary exponential backoff (BEB) algorithm resolves collisions of packets transmitted simultaneously by different stations. The BEB algorithm prevents packet collisions during simultaneous access by randomizing moments at stations attempting to access the wireless channels. However, this randomization does not eliminate packet collisions entirely, leading to reduced system throughput and increased packet delay and drop. In addition, the BEB algorithm results in unfair channel access among stations. In this paper, we propose an enhanced binary exponential backoff algorithm to improve channel access fairness by adjusting the manner of increasing or decreasing the contention window based on the number of the successfully sent frames. We propose several configurations and use the NS2 simulator to analyze network performance. The enhanced binary exponential backoff algorithm improves channel access fairness, significantly increases network throughput capacity, and reduces packet delay and drop. Copyright © 2013 John Wiley & Sons, Ltd.     

Hopping control channel MAC protocol for opportunistic spectrum access networks

Opportunistic spectrum access （OSA） is considered as a promising approach to mitigate spectrum scarcity by allowing unlicensed users to exploit spectrum opportunities in licensed frequency bands. Derived from the existing channel-hopping multiple access （CHMA） protocol,we introduce a hopping control channel medium access control （MAC） protocol in the context of OSA networks. In our proposed protocol,all nodes in the network follow a common channel-hopping sequence; every frequency channel can be used as control channel and data channel. Considering primary users＇ occupancy of the channel,we use a primary user （PU） detection model to calculate the channel availability for unlicensed users＇ access. Then,a discrete Markov chain analytical model is applied to describe the channel states and deduce the system throughput. Through simulation,we present numerical results to demonstrate the throughput performance of our protocol and thus validate our work.     

根据用户数目妥善安排传输的多址接入协议

提出了一种新型的多址接入协议根据用户数目妥善安排传输的多址接入协议,它用轮询的方式妥善安排用户的分组传输,并以独特的帧结构和高效的接入竞争算法保证节点能快速地接入信道。对UPMA协议的仿真结果表明它比CSMA/CA协议具有更优越的性能。     

An adaptive reservation scheme for VBR voice traffic in wireless ATM networks

A reservation scheme, named dynamic hybrid partitioning, is proposed for the Medium Access Control (MAC) protocol of wireless ATM (WATM) networks operating in Time Division Duplex (TDD) mode. The goal is to improve the performance of the real-time Variable Bit Rate (VBR) voice traffic in networks with mixed voice/data traffic. In most proposed MAC protocols for WATM networks, the reservation phase treats all traffic equally, whether delay-sensitive or not. Hence, delay-sensitive VBR traffic sources have to compete for reservation each time they wake up from idle mode. This causes large and variable channel access delays, and increases the delay and delay variation (jitter) experienced by ATM cells of VBR traffic. In the proposed scheme, the reservation phase of the MAC protocol is dynamically divided into a contention-free partition for delay-sensitive idle VBR traffic, and a contention partition for other traffic. Adaptive algorithms dynamically adjust the partition sizes to minimize the channel bandwidth overhead. Simulation results show that the delay performance of delay-sensitive VBR traffic is improved while minimizing the overhead.     

Mobility-aware timeout medium access control protocol for wireless sensor networks

Wireless sensor networks (WSNs), has been under development for a while by the academia and industry. Due to limited computational power, a typical sensor node may experience operational challenges. Moreover, mobility has become an important feature since emergency and healthcare related applications are evolving in WSNs. Consideration of mobile nodes in WSNs introduce new challenges for the designers. In this paper, an enhanced version of T-MAC protocol (a well-known medium access control protocol in WSNs) known as MT-MAC is proposed. Using the capturing fluctuation in RSSI and LQI values of the received SYNC packets, MT-MAC solves high packet drop ratio in T-MAC. By detecting the mobility, a mobile node softly handover to a new virtual cluster without losing connection with other nodes. The performance of the proposed solution is then compared with T-MAC, S-MAC as well as other well-known mobility-aware MAC (MS-MAC) protocol. The simulation results show that the proposed protocol significantly increases the throughput and packet delivery ratio of T-MAC in exchange for a small increase in power consumption. Compared to MS-MAC protocol, the proposed approach can reduce power consumption by 20–65%, and achieve slightly higher packet delivery ratio.     

UPnP设备权限控制及安全协议的研究与设计

UPnP协议已经越来越多的应用到局域网络以及家庭智能网络中,但是由UPnP带来的安全问题也越来越受到重视,并且相关的解决方案很少。本文在介绍UPnP组成及工作流程的同时,也对UPnP容易引起的安全问题进行分析,进而作者提供了一种由安全控制台来对设备进行权限控制、设备和控制点之间进行加密传输的安全协议。此安全协议能够有效保护数据完整性、保护信息的不可抵赖、防止重发攻击等。     

APON接人系统的一个介质访问控制协议

作为共享介质的接入网络,APON需要介质访问控制协议用于协调各终端对介质的存取.本文提出了一个符合ITU-T建议的MAC协议,采用了时延分优先级,对高优先级的实时业务按照的均匀间隔的原则分配带宽,低优先级业务的带宽按次序循环分配.上行帧长度根据处于连接的用户数动态变化,各终端的带宽申请时隙由系统动态分配.最后给出了由该协议确定的网络性能的计算机仿真结果.     

An asynchronous low‐power medium access control protocol for wireless sensor networks

Duty cycling is a fundamental approach used in contention‐based medium access control (MAC) protocols for wireless sensor networks (WSNs) to reduce power consumption in sensor nodes. Existing duty cycle‐based MAC protocols use either scheduling or low‐power listening (LPL) to reduce unnecessary energy lost caused by idle listening and overhearing. This paper presents a new asynchronous duty‐cycled MAC protocol for WSN. It introduces a novel dual preamble sampling (DPS) approach to efficiently coordinate channel access among nodes. DPS combines LPL with a short‐strobed preamble approach to significantly reduce the idle‐listening issue in existing asynchronous protocols. We provide detailed analysis of the energy consumption by using well‐known energy models and compare our work with B‐MAC and X‐MAC, two most popular asynchronous duty cycle‐based MAC protocols for WSNs. We also present experimental results based on NS‐2 simulations. We show that depending on the traffic load and preamble length, the proposed MAC protocol improves energy consumption significantly without degrading network performances in terms of delivery ratio and latency. For example, for a traffic rate of 0.1 packets/s and a preamble length of 0.1 s, the average improvement in energy consumption is about 154%. Copyright © 2011 John Wiley & Sons, Ltd.     

Standardization of a multi-configuration medium access protocol for broadband ISDN

This paper examines the current work within various standards bodies to define a multi-configuration medium access control (MAC) protocol for operation between broadband ISDN terminals. To begin, the configurations in which the MAC protocol is expected to operate are introduced. The relation between the MAC protocol and the broadband ISDN resource allocation schemes is then discussed. Several MAC protocol proposals currently being discussed in various standards bodies, each with unique assumptions regarding resource allocation in broadband ISDN, are then described and compared. Finally, areas for future work on this topic are identified.