无线 IP网络的移动

IP技术和无线通信技术的结合，是将来无线网络的趋势。探讨了无线IP网络的移动解决方案，分析和比较了移动IP、蜂窝IP和SIP等移动切换技术，并提出了一种综合的解决方案。     

基于无线链路的数据包丢失问题研究

本文首先分析了无线链路上数据包丢失的具体原因，探讨了无线网络环境下的各种传输控制机制．并指出它们的优势与不足最后提出了进一步的工作方向。     

Exploit Network Coding Over GF(2 q ) for Multi-user Cooperative Wireless Networks

In this paper, we present a decode-and-forward network coded (DFNC) scheme over GF(2 ^q ) for the multi-user cooperative communication systems. In particular, we consider a cooperative network with m users transmitting independent packets to the same destination. These users form a cooperation set to help each other by using linear network coding. We propose a coding coefficients construction method which can efficiently reduce the transmission overhead from m(q + log₂ m) to m bits compared with conventional random network coding. Furthermore, we propose a novel decoding algorithm—credit-based updating algorithm in order to improve the solvability of decoding set of equations at the destination. The proposed decoding algorithm is combined with channel decoding and is applied on symbol-level. It can fully make use of the error recovery property of network coding while conventional decoding algorithms (e.g., Gaussian elimination) overlook it. We theoretically analyze the diversity performance in terms of information outage probability, and the results show that diversity order of m + 1 can be achieved for a m-user cooperation system. Moreover, we conduct extensive simulations to show that DFNC outperforms other transmission schemes in terms of symbol error rate and achieves higher diversity order. We also demonstrate that the proposed decoding algorithm provides significant performance gain over conventional decoding algorithm.     

基于IP无线网络中的移动性

基于IP的无线网络将成为下一代移动网络的核心。在全IP无线网络中。移动性对于多媒体应用起着十分重要的作用。探讨了基于IP的无线网络中的一些重要问题,包括移动IP、移动IPv6和其它相关的一些技术。同时还讨论了WLAN、WWAN、2G以及3G蜂窝网和下一代混合移动网络中关于移动性支持等问题。     

无线网络中的移动模型

移动ad hoc网络(MANET)是指不依赖于固定设备,而由一组无线节点通过自组织而形成的网络.移动性是MANET最主要的特性之一,对网络的性能产生极大的影响.该文主要介绍了MANET中常见的移动模型,并简要分析了他们的主要特点和适用环境.     

基于MPLS无线接入网中的快速切换

为了减少时延,克服协议的局限性,提出了一基于MPLS的无线接入微移动方案,对传统的微移动方案进行了延伸,采用在标记交换路由器上引入中间标记信息库（I-LIB）采达到减少时延,提高服务质量的目的。     

Random Mobility and Heterogeneity-Aware Hybrid Synchronization for Wireless Sensor Network

Random mobility of a node in wireless sensor networks (WSNs) causes the frequent changes in the network dynamics with increased cost in terms of energy and bandwidth. During data collections and transmission, they need the additional efforts to synchronize and schedule the activities of nodes. A key challenge is to maintain the global clock scale for synchronization of nodes at different levels to minimize the energy consumption and clock skew. It is also difficult to schedule the activities for effective utilization of slots allocated for aggregated data transmission. The paper proposes the Random Mobility and Heterogeneity-aware Hybrid Synchronization Algorithm (MHS) for WSN. The proposed algorithm uses the cluster-tree for efficient synchronization of CH and nodes in the cluster and network, level-by-level. The network consists of three nodes with random mobility and are heterogeneous regarding energy with static sink. All the nodes and CH are synchronized with the notion of the global timescale provided by the sink as a root node. With the random mobility of the node, the network structure frequently changes causing an increase in energy consumption. To mitigate this problem, MHS aggregate data with the notion of a global timescale throughout the network. Also, the hierarchical structure along with pair-wise synchronization reduces the clock skews hence energy consumption. In the second phase of MHS, the aggregated data packets are passed through the scheduled and synchronized slots using TDMA as basic MAC layer protocol to reduce the collision of packets. The results are extended by using the hybrid approach of scheduling and synchronization algorithm on the base protocol. The comparative results show that MHS is energy and bandwidth efficient, with increased throughput and reduced delay as compared with state-of-the-art solutions.     

无线传感器网络MAC协议移动性支持问题的研究

在以往的无线传感器网络研究过程中,研究者通常假设网络中节点的位置不发生变化,忽略了移动性对网络的影响.近期研究表明,支持无线传感器节点移动性,研究移动无线传感器网络MAC协议是十分必要的.本文在研究移动性对MAC协议设计所带来的挑战基础上,分析和总结了移动性对现有MAC协议的影响,以及当前在支持节点移动性方而所作的工作.最后,文章重点探讨了未来移动传感器网络MAC协议研究过程中值得深入研究的内容.     

Hop-by-Hop Congestion Control Over a Wireless Multi-Hop Network

This paper focuses on congestion control over multi-hop, wireless networks. In a wireless network, an important constraint that arises is that due to the MAC (Media Access Control) layer. Many wireless MACs use a time-division strategy for channel access, where, at any point in space, the physical channel can be accessed by a single user at each instant of time. In this paper, we develop a fair hop-by-hop congestion control algorithm with the MAC constraint being imposed in the form of a channel access time constraint, using an optimization-based framework. In the absence of delay, we show that this algorithm are globally stable using a Lyapunov-function-based approach. Next, in the presence of delay, we show that the hop-by-hop control algorithm has the property of spatial spreading. In other words, focused loads at a particular spatial location in the network get "smoothed" over space. We derive bounds on the "peak load" at a node, both with hop-by-hop control, as well as with end-to-end control, show that significant gains are to be had with the hop-by-hop scheme, and validate the analytical results with simulation     

Light-Weight AAA Infrastructure for Mobility Support Across Heterogeneous Networks

Security and privacy architecture for various access networks have often been considered on the upper service layers in the form of application and transport security and from lower layers in the form of security over wireless networks. Today there is no trust relationship between the stakeholders of different access network types for e.g. wireless mesh network, wireless PAN, wireless LAN, cellular network, satellite etc. and each have their own security mechanism. What is common for these access networks is the networking layer which is IP based. In order to provide seamless service across these heterogeneous access networks there must be a trust relationship among the stakeholders for authentication, authorization, accounting and billing of end user. However, what is still missing is a general solution which is both adaptable to the network types and conditions and also takes into account end system capabilities as well as enabling inter-domain AAA negotiation. This paper proposes a light-weight AAA infrastructure providing continuous, on-demand, end-to-end security in heterogeneous networks.     

无线通信网络的移动性管理

未来无线通信网络的两个最重要的研究问题就是宽带和无缝漫游，而移动性管理是实现网络间无缝漫游的关键难题之一。本对移动性管理涉及的各个方面进行了简要的概述，首先介绍了移动性管理的分类和它对协议层次的影响，接着介绍了移动性管理的一般性框架和主要的协议特点，最后介绍了一些关键的研究问题和研究热点。     

A Parallel Architecture for Network Control and Mobility Tracking in Wireless Systems

In a wireless system the network logically rearranges itself rapidly whenever terminals move from cell to cell. This ability to adapt itself to changing locations of its terminals adds a new layer of complexity to wireless control software. With ever increasing demand for more capacity and the addition of new service features, many limitations and bottlenecks in the underlying network infrastructure are uncovered. While distributed architectures provide a method for increasing processing capacity, they also introduce concerns regarding reliability, communication latency and cost. In this paper we have attempted to combine the significant characteristics of both fixed and distributed architectures in a single system. Specifically, we present the design of a wireless hub processor, based on a communications oriented active memory technology, and illustrate how the procedures for mobility management, resource management and call processing map on to such a parallel architecture. A key attribute of the architecture is that it scales in processing capacity and size, while maintaining a common locus of control for administration, maintenance and reliability. Finally, we present an example of a navigation application to validate the architecture. This example shows how a roving computer or PDA connected to a global positioning system and having a wireless communication link can deal with a low bandwidth link to a server. The server provides user-tailored map data. An active memory architecture not only provides the server with a scalable architecture but also aids the client.     

基于在线评估的无线Mesh网流媒体缓存

针对无线Mesh网的特点,本文研究了媒体片段副本密度的理想最佳分布与流媒体片段流行度空间分布、节点能力以及节点稳定性之间的关系,提出了基于副本稳定性补偿的缓存优化算法.相应的,为了及时准确地了解各个地点的节点行为特性,本文提出了基于年龄分布分析的可靠性评估算法.进而本文提出了一种轻量级的全分布式的流媒体缓存策略实施方案...     

无线网络环境下命名数据网络移动性解决方案

通过数据消费者驱动的命名数据网络(NDN)可以实现数据的高效可靠传递,然而NDN中兴趣包的广播机制使得其不适用于带宽受限的无线网络环境;此外,针对数据提供者发生移动所带来的问题,NDN也没有很好的解决方案。通过分析无线网络环境下NDN通信流程中存在的问题,提出了一种无线网络分层隔离方案,通过给内容分配路由标识,实现了数据提供者移动时兴趣包的正确路由,避免了兴趣包广播及重传对无线网络带宽资源的浪费。     

Delay Performance of Two-Hop Buffer-Aided Relay Network with Wireless Assisted Links

Wireless Personal Communications - In this paper, we consider two-hop buffer-aided relay network (TBRN) with half-duplex (HD) decode-and-forward (DF) and fading block channel where source transmits...     

一种对3G网络无线链路上ROHC的改进方法

介绍了ROHC这种目前公认应用于无线链路上较为理想的头部压缩方式。通过对其模式转换的分析，发现了其中鲁棒性与压缩效率未能兼顾的缺点，从而讨论了一种新的模式转换的改进方法，进一步提高了ROHC的鲁棒性与压缩效率的平衡性。最后，用仿真实验验证了改进方法的有效性。     

无线体域网(3)

无线体域网是个人健康信息采集与传输的重要技术手段之一,具有重要现实意义和产业化前景,受到工业界、学术界和标准化组织的广泛关注。另外,IEEE 802.15.6协议标准是目前国际上公认的一款适用于健康信息采集的未来超短距无线体域网协议标准。讲座将分3期对该技术进行介绍:第1期讲述无线体域网的背景、研究动态和技术特征;第2期对无线体域网的频段选取、信道建模、MAC层协议、通信技术和数据处理技术特征进行介绍;第3期介绍无线体域网的节点设计、数据采集和应用场景问题。     

Link Layer Adaptation for Shared Wireless Links

While traditional link layer protocols assume that they fully control the underlying link, in contemporary wireless networks the link may be dynamically shared by sessions belonging to different users and/or applications. To assess the impact of link sharing, we measure the File Transfer and Web Browsing throughput achieved over a Selective Repeat (SR) protocol, with or without contention from Media Distribution. Our results indicate that the optimal protocol settings strongly depend on the level of contention for the link. We therefore present two link layer protocols that adapt to the available bandwidth, our Adaptive Selective Repeat (ASR) protocol which dynamically modifies its retransmission timeouts, and the Radio Link Control (RLC) protocol specified for use by Universal Mobile Telecommunications System networks which does not employ retransmission timers. We first repeat our performance measurements to determine the optimal settings for each protocol, and then compare the fine tuned versions of all protocols with respect to their File Transfer and Web Browsing throughput, as well as to the delay induced to the contending Media Distribution packets. Our results indicate that while both RLC and ASR are more stable than SR, the complex RLC does not match the performance of our simpler ASR.     

Mobility Management for Hierarchical Wireless Networks

In this paper, we consider the mobility management in large, hierarchically organized multihop wireless networks. The examples of such networks range from battlefield networks, emergency disaster relief and law enforcement etc. We present a novel network addressing architecture to accommodate mobility using a Home Agent concept akin to mobile IP. We distinguish between the physical routing hierarchy (dictated by geographical relationships between nodes) and logical hierarchy of subnets in which the members move as a group (e.g., company, brigade, battalion in the battlefield). The performance of the mobility management scheme is investigated through simulation.     

Simultaneous Dual Band Transmission Over Multimode Fiber-Fed Indoor Wireless Network

Performance measurements of different combinations of digital enhanced cordless telecommunications packet radio service, global system for mobile communications, universal mobile telecommunication service, and 802.11g (54 Mbps) signals in a dual band configuration transmitted over an indoor wireless network fed by a low-cost 850-nm vertical-cavity surface-emitting laser (VCSEL)-300m multimode fiber link are presented. The feasibility of such a system is demonstrated with error vector magnitude measurements which are within the required specifications