定向自组网中基于报文多时延等级的发送端调度算法

面向接收机冲突的多址接入（ROMA）是一种高效的适用于多波束自适应阵列天线的调度协议,但它无法保证具有不同时延要求的报文传输的服务质量。针对此问题,在原始ROMA的基础上提出了一种多时延限制的调度算法（MDRS）。通过在调度接入过程中插入子时隙,比较发送端报文时延信息,调度发送节点的传输顺序,使得时延限制更严格的报文优先发送,从而提高了不同时延等级的报文的传输成功率。最后,通过仿真验证了MDRS的性能：与原始ROMA相比,所提算法在多时延限制的发送端调度中表现出了更好的吞吐量和传输成功率。     

Ad hoc网络基于信息的调度算法

针对Ad hoc网络提出一种基于信息的调度策略。分组调度时,既考虑队列中剩余信息的多少又考虑原始的信息长度。仿真结果表明,算法改进了整个系统信息端到端的时延性能,并且不影响网络的吞吐量性能,不需要额外的通信开销。     

Ad hoc网络中分组调度算法研究

本文概述了Ad hoc网络及其特点、结构等;阐述了有线网络的分组调度算法在Ad hoc网络中的局限性;重点介绍了几种现有的典型Ad doc网络的分组调度算法。     

Ad hoc网络技术讲座第1讲Ad hoc网络的体系结构和信道接入协议

本文首先介绍Ad hoc网络的概貌，然后分析Ad hoc网络的体系结构。在介绍了信道接入协议的地位和作用后，对Ad hoc网络特有的信道共享方式。隐终端和暴露终端问题进行了介绍和分析。文章把Ad hoc网络的信道接入协议划分成基于单信道、双信道和多信道三类，最后给出了Ad hoc网络信道接入协议的发展动向。     

Ad hoc网络中基于时延最小自适应流量分配算法

由于Ad hoc网络带宽有限,多径传输能提高有效带宽能力,满足有一定带宽要求的QoS服务需求。该文从理论上论证了合理分配流量实现时延最小的可行性,并提出了基于时延最小自适应流量分配算法(ATDBMD),目的是科学利用多条路径,满足QoS业务对时延的要求。仿真分析证明,ATDBMD算法能降低平均时延和时延抖动,并具有简单、快速自适应性和准确性等优点,明显优于其它算法。     

基于Ad hoc网络的退避算法研究

在移动Ad hoc网络中,无线信道由多个节点共享,合理协调多个节点访问共享信道的媒体接入控制(MAC,Medium Access Control)协议是移动Ad hoc网络的关键技术之一。退避算法在MAC协议中起着至关重要的作用。针对目前退避算法存在的问题,本文提出了一种改进算法,根据网络节点发送数据包成功与否,预测网络信道空闲或繁忙的趋势,应用趋势合理地调节退避算法中节点发送数据时退避值的大小,并通过Omnet++软件对算法进行了仿真分析对比。     

移动Ad hoc网络中的密钥管理

首先阐述了移动adhoc网络中密钥管理的重要性,接着探讨了几种密钥管理的方法,包括局部分布式认证授权中心、完全分布式认证授权中心、自发证书、安全Pebblenets、指示性标志、基于口令验证的密钥交换等,并对这些方法进行了较完整的概括总结和深入的比较分析,最后提出了一些研究移动adhoc网络中密钥管理方法所必须注意的问题。     

Ad hoc网络技术讲座第1讲 Ad hoc网络的体系结构和信道接入协议

本文首先介绍Adhoc网络的概貌,然后分析Adhoc网络的体系结构。在介绍了信道接入协议的地位和作用后,对Adhoc网络特有的信道共享方式、隐终端和暴露终端问题进行了介绍和分析。文章把Adhoc网络的信道接入协议划分成基于单信道、双信道和多信道三类,最后给出了Adhoc网络信道接入协议的发展动向。     

关于Ad hoc网络中传输能量控制的介绍

能量控制的主要目标是减少包传输的总体能量消耗,以及通过提高信道的空间复习率增加网络的吞吐量。本文首先概括各种已经提出的能量控制方法,然后讨论影响传输能量的因素,包括路由协议和媒体接入间的相互影响。最后,为解决两者间的影响提出一些建议。     

Ad hoc网络在智能家居中的应用研究

本文构建了采用脉冲超带宽无线传输技术,基于ad hoc网络架构的智能家居系统,给出了智能家居系统的体系结构与模块的组成,并且对所建立的家庭网络协议与网络管理功能进行了全面的分析与阐述.针对家庭区域网络的节点特征,设计了一种适合家庭网络的路由协议,有效地降低了网络的负载,提高了传输的效率,为智能家居的具体实现提供了一种可行的方案.     

Receiver-Oriented Multiple Access in Ad Hoc Networks with Directional Antennas

Directional antennas can adaptively select radio signals of interest in specific directions, while filtering out unwanted interference from other directions. A couple of medium access protocols based on random access schemes have been proposed for networks with directional antennas, using the omnidirectional mode for the transmission or reception of control packets in order to establish directional links. We propose a distributed receiver-oriented multiple access (ROMA) scheduling protocol, capable of utilizing multi-beam forming directional antennas in ad hoc networks. Unlike random access schemes that use on-demand handshakes or signal scanning to resolve communication targets, ROMA computes a link activation schedule in each time slot using two-hop topology information. It is shown that significant improvements on network throughput and delay can be achieved by exploiting the multi-beam forming capability of directional antennas in both transmission and reception. The performance of ROMA is studied by simulation, and compared with a well-know static scheduling scheme that is based on global topology information.     

Priority Scheduling in Wireless Ad Hoc Networks

Ad hoc networks formed without the aid of any established infrastructure are typically multi-hop networks. Location dependent contention and hidden terminal problem make priority scheduling in multi-hop networks significantly different from that in wireless LANs. Most of the prior work related to priority scheduling addresses issues in wireless LANs. In this paper, priority scheduling in multi-hop networks is discussed. We propose a scheme using two narrow-band busy tone signals to ensure medium access for high priority source stations. The simulation results demonstrate the effectiveness of the proposed scheme. Xue Yang received the B.E. degree and the M.S. degree from University of Electronic Science and Technology of China. She is currently a Ph.D. candidate at University of Illinois at Urbana-Champaign (UIUC). She is awarded Vodafone-U.S. Foundation Graduate Fellowship from 2003 to 2005. Her current research is in the areas of wireless networking and mobile computing, with the focus on medium access control, quality of service and topology control. Her research advisor is Prof. Nitin Vaidya at UIUC. For more information, please visit Nitin H. Vaidya received the PhD degree from the University of Massachusetts at Amherst. He is presently an Associate Professor of Electrical and Computer Engineering at the University of Illinois at Urbana-Champaign (UIUC). He has held visiting positions at Microsoft Research, Sun Microsystems and the Indian Institute of Technology-Bombay. His current research is in the areas of wireless networking and mobile computing. His research has been funded by various agencies, including the National Science Foundation, DARPA, BBN Technologies, Microsoft Research, and Sun Microsystems. Nitin Vaidya is a recipient of a CAREER award from the National Science Foundation. Nitin has served on the program committees of several conferences and workshops, and served as program co-chair for the 2003 ACM MobiCom. He has served as editor for several journals, and presently serves as Editor-in-Chief for IEEE Transactions on Mobile Computing, and as editor-in-chief of ACM SIGMOBILE periodical MC2R. He is a senior member of IEEE and a member of the ACM. For more information, please visit     

移动自组织网络中基于QoE的跨层多波束信道接入机制

引入数字多波束技术可以使移动自组织网络的信道容量得到有效提升,然而,时间、频率、空间、用户、功率等多维度资源域的统一调度与跨层联合优化使得信道接入机制的分析与设计变得更加复杂。为此,结合多波束的特性,将波束宽度限制、收发限制、通道限制、功率限制等多种约束条件抽象图论问题,并建立分析模型。基于分析模型,进一步提出了MB-MAC(Multi-beam Medium Access Control)信道接入机制,结合物理层的预编码技术,建立定向链路的队列模型,度量用户的满意度(Quality of Experience,QoE),设计了适用于自组织网络中多用户并发并收的信道接入机制,兼顾了网络容量和用户满意度。仿真结果表明,MB-MAC机制能在保证各个用户满意度的情况下,有效提升网络吞吐率。     

Distributed Priority Scheduling and Medium Access in Ad Hoc Networks

Providing Quality-of-Service in random access multi-hop wireless networks requires support from both medium access and packet scheduling algorithms. However, due to the distributed nature of ad hoc networks, nodes may not be able to determine the next packet that would be transmitted in a (hypothetical) centralized and ideal dynamic priority scheduler. In this paper, we develop two mechanisms for QoS communication in multi-hop wireless networks. First, we devise distributed priority scheduling, a technique that piggybacks the priority tag of a node's head-of-line packet onto handshake and data packets; e.g., RTS/DATA packets in IEEE 802.11. By monitoring transmitted packets, each node maintains a scheduling table which is used to assess the node's priority level relative to other nodes. We then incorporate this scheduling table into existing IEEE 802.11 priority backoff schemes to approximate the idealized schedule. Second, we observe that congestion, link errors, and the random nature of medium access prohibit an exact realization of the ideal schedule. Consequently, we devise a scheduling scheme termed multi-hop coordination so that downstream nodes can increase a packet's relative priority to make up for excessive delays incurred upstream. We next develop a simple analytical model to quantitatively explore these two mechanisms. In the former case, we study the impact of the probability of overhearing another packet's priority index on the scheme's ability to achieve the ideal schedule. In the latter case, we explore the role of multi-hop coordination in increasing the probability that a packet satisfies its end-to-end QoS target. Finally, we perform a set of ns-2 simulations to study the scheme's performance under more realistic conditions.     

软件定义的无人机网络架构研究综述

软件定义网络（Software Defined Network,SDN）依靠着其集中控制、可编程性和数控分离等优点,能够有效解决无人机网络（Flying Ad Hoc Network,FANET）面临的任务拓扑高度变化、网络链路连接不稳定、网络安全防护脆弱以及应用程序的异构性等问题,极大地提升FANET的灵活性和可靠性。针对SDN架构与FANET的结合问题,描述了SDN的体系架构,并以SDN控制器部署方式为关注点分类别概括了近几年软件定义无人机网络（Software-defined Flying Ad Hoc Network,SD-FANET）的研究进展,重点阐述了结合移动边缘计算（Mobile Edge Computing,MEC）的SD-FANET研究现状,最后指出了SD-FANET的应用场景和一些具体的未来研究方向。     

Energy-Efficient, Collision-Free Medium Access Control for Wireless Sensor Networks

The traffic-adaptive medium access protocol (TRAMA) is introduced for energy-efficient collision-free channel access in wireless sensor networks. TRAMA reduces energy consumption by ensuring that unicast and broadcast transmissions incur no collisions, and by allowing nodes to assume a low-power, idle state whenever they are not transmitting or receiving. TRAMA assumes that time is slotted and uses a distributed election scheme based on information about traffic at each node to determine which node can transmit at a particular time slot. Using traffic information, TRAMA avoids assigning time slots to nodes with no traffic to send, and also allows nodes to determine when they can switch off to idle mode and not listen to the channel. TRAMA is shown to be fair and correct, in that no idle node is an intended receiver and no receiver suffers collisions. An analytical model to quantify the performance of TRAMA is presented and the results are verified by simulation. The performance of TRAMA is evaluated through extensive simulations using both synthetic- as well as sensor-network scenarios. The results indicate that TRAMA outperforms contention-based protocols (CSMA, 802.11 and S-MAC) and also static scheduled-access protocols (NAMA) with significant energy savings. This work was supported in part by the NSF-NGI grant number ANI-9813724 and by the Jack Baskin Chair of Computer Engineering at UCSC. Venkatesh Rajendran received the B.E. degree in Electronics and Communication Engineering from the Anna University in 2001, and M.S. in Computer Engineering from the University of California, Santa Cruz (UCSC) in 2003. He is currently working towards his Ph.D at UCSC. He is a graduate student researcher at the Inter-networking Research Lab (INRG). His research interests are in wireless communication system design, energy-aware media access control protocols for wireless ad hoc networks, smart sensor networks, reliable multi-casting, wireless multi-carrier communications, digital signal processing, adaptive modulation, and smart antenna systems. Katia Obraczka received the B.S. and M.S. degrees in electrical and computer engineering from the Federal University of Rio de Janeiro, Brazil, and the M.S. and Ph.D. degrees in computer science from the University of Southern California (USC). She is an Assistant Professor of Computer Engineering at the University of California, Santa Cruz. Before joining UCSC, she held a research scientist position at USC's Information Sciences Institute and a research faculty appointment at USC's Computer Science Department. Her research interests include computer networks, more specifically, network protocol design and evaluation in wire-line as well as wireless (in particular, multi-hop ad hoc) networks, distributed systems, and Internet information systems. J.J. Garcia-Luna-Aceves received the M.S. and Ph.D. degrees in electrical engineering from the University of Hawaii, Honolulu, HI, in 1980 and 1983, respectively. He is the Baskin Professor of Computer Engineering at the University of California, Santa Cruz (UCSC). Dr. Garcia-Luna-Aceves directs the Computer Communication Research Group (CCRG), which is part of the Information Technologies Institute of the Baskin School of Engineering at UCSC. He has been a Visiting Professor at Sun Laboratories and a consultant on protocol design for Nokia. Prior to joining UCSC in 1993, he was a Center Director at SRI International (SRI) in Menlo Park, California. Dr. Garcia-Luna-Aceves has published a book and more than 250 refereed papers and three U.S patents, and has directed more than 18 Ph.D. theses at UCSC. He has been Program Co-Chair of ACM MobiHoc 2002 and ACM Mobicom 2000; Chair of the ACM SIG Multimedia; General Chair of ACM Multimedia '93 and ACM SIGCOMM '88; and Program Chair of IEEE MULTIMEDIA '92, ACM SIGCOMM '87, and ACM SIGCOMM '86. He has served in the IEEE Internet Technology Award Committee, the IEEE Richard W. Hamming Medal Committee, and the National Research Council Panel on Digitization and Communications Science of the Army Research Laboratory Technical Assessment Board. HE has been on the editorial boards of the IEEE/ACM Transactions on Networking, the Multimedia Systems Journal, and the Journal of High Speed Networks. He received the SRI International Exceptional-Achievement Award in 1985 and 1989, and is a senior member of the IEEE.     

A Cross-layer Approach to Channel Assignment in Wireless Ad Hoc Networks

To improve the capacity of wireless ad hoc networks by exploiting multiple available channels, we propose a distributed channel assignment protocol that is based on a cross-layer approach. By combining channel assignment with routing protocols, the proposed channel assignment protocol is shown to require fewer channels and exhibit lower communication, computation, and storage complexity than existing channel assignment schemes. A multi-channel MAC (MC-MAC) protocol that works with the proposed channel assignment protocol is also presented. We prove the correctness of the proposed channel assignment protocol. In addition, through a performance study, we show that the proposed protocol can substantially increase throughput and reduce delay in wireless ad hoc networks, compared to the IEEE 802.11 MAC protocol and an existing multi-channel scheme.

依据用户妥善安排的多址接入协议在分布式无线网络中的性能研究

本文基于有效竞争预约接入、无冲突轮询传输的思想提出了在多跳分布式无线网络中支持节点移动性和多跳网络结构的依据用户妥善安排的多址接入(UPMA)协议.该协议能够保证发送节点快速接入信道,从而大大提高信道的使用效率.用仿真方法研究了多跳分布式无线网络中采用该协议时的网络性能.结果表明,UPMA协议可以提供较高的通过量、较低的平均分组时延和较小的平均分组丢失率.