Internet Connectivity for Ad Hoc Mobile Networks

The growing deployment rate of wireless LANs indicates that wireless networking is rapidly becoming a prevalent form of communication. As users become more accustomed to the use of mobile devices, they increasingly want the additional benefit of roaming. The Mobile IP protocol has been developed as a solution for allowing users to roam outside of their home networks while still retaining network connectivity. The problem with this solution, however, is that the deployment of foreign agents is expensive because their coverage areas are limited due to fading and interference. To reduce the number of foreign agents needed while still maintaining the same coverage, ad hoc network functionality can cooperate with Mobile IP such that multihop routes between mobile nodes and foreign agents can be utilized. In this work, we present a method for enabling the cooperation of Mobile IP and the Ad hoc On-Demand Distance Vector (AODV) routing protocol, such that mobile nodes that are not within direct transmission range of a foreign agent can still obtain Internet connectivity. In addition, we describe how duplicate address detection can be used in these networks to obtain a unique co-located care-of address when a foreign agent is not available.     

An Efficient Multicast Routing Protocol in Wireless Mobile Networks

Providing multicast service to mobile hosts in wireless mobile networking environments is difficult due to frequent changes of mobile host location and group membership. If a conventional multicast routing protocol is used in wireless mobile networks, several problems may be experienced since existing multicast routing protocols assume static hosts when they construct the multicast delivery tree. To overcome the problems, several multicast routing protocols for mobile hosts have been proposed. Although the protocols solve several problems inherent in multicast routing proposals for static hosts, they still have problems such as non-optimal delivery path, datagram duplication, overheads resulting from frequent reconstruction of a multicast tree, etc. In this paper, we summarize these problems of multicast routing protocols and propose an efficient multicast routing protocol based on IEFT mobile IP in wireless mobile networks. The proposed protocol introduces a multicast agent, where a mobile host receives a tunneled multicast datagram from a multicast agent located in a network close to it or directly from the multicast router in the current network. While receiving a tunneled multicast datagram from a remote multicast agent, the local multicast agent may start multicast join process, which makes the multicast delivery route optimal. The proposed protocol reduces data delivery path length and decreases the amount of duplicate copies of multicast datagrams. We examined and compared the performance of the proposed protocol and existing protocols by simulation under various environments and we got an improved performance over the existing proposals.     

第四代移动互联网切换算法

第四代移动通信网络是一个多网集成和重叠覆盖同一个区域的综合网络.为满足用户移动过程中,不同网络之间切换的需求,从提供用户快捷的数据传输服务和提高网络资源使用效率的角度出发,提出在不同的网络之间建立一个新的数据通道,从而给出了一种新的切换算法.仿真实验表明,使用新的切换算法不仅能获得高的数据传输速度,还能有效地提高载频的使用效率.     

Urban 802.11 Community Networks for Mobile Users: Current Deployments and Prospectives

Few years ago some network operators launched a new service called Community Networks, where each subscriber shares its residential Internet connection with other subscribers of the same operator via his 802.11 access point. Due to the high access point density in urban areas, community networks have the potential to offer high data rate wireless Internet access for mobile users, going beyond the currently available hot-spots, which are typically deployed in a limited number of isolated locations (e.g., airports, cafes). Unlike cellular networks, the locations of community network access points is not centrally planned. We evaluate existing community networks using a participatory sensing application called Wi2Me. First, we analyze different metrics in order to characterize community networks. Second, we take advantage of this unique 802.11 network (in terms of density and coverage) to study how mobility can be supported by identifying drawbacks and proposing some possible solutions.     

基于移动代理WSN分布入侵检测研究

针对聚类无线传感器网络安全的问题,将移动代理技术与分布式入侵检测技术相结合,提出了一种基于移动代理的无线传感器网络分布式入侵检测方案,采用了多个代理模块进行分布式协作,运用一种基于聚类的分布式入侵检测算法,从节点上收集和处理数据,减少网络负载、促进效率平衡,能够满足WSNs的要求和限制。从而达到提高无线传感器网络的安全性、可靠性,降低入侵检测能量消耗的目的。     

使用移动Agent技术的网络管理

当今大型的通信网络往往集成了来自多家厂商的网络和通讯设备，而基于集中式方式的传统网络管理已难以满足用户的需求。移动ａｇｅｎｔ是能够自动在网络各节点间移动并代表其它实体工作的软件实体，引起了人们广泛关注。文章介绍了有关移动ａｇｅｎｔ的基本概念及其系统实现，并讨论了网络管理中移动ａｇｅｎｔ技术的几个应用实例以表明移动ａｇｅｎｔ是解决异构环境的复杂网管的有效途径。     

移动代理技术在Ad Hoc无线网络中的应用研究

Ad Hoc无线网络是一组具有路由和转发功能的移动节点组成的一个多跳的临时性自治系统,是一种无中心的无线网络。现有的主动路由协议或者按需路由协议都不能很好地满足Ad Hoc网络的需要。介绍了Ad Hoc无线移动网络和移动代理技术。在分析了现有的2种路由协议后,提出了在按需路由协议中加入移动代理技术来增强Ad Hoc无线网络的性能。在这些结果的基础上,提出了移动代理通信协议。     

An Index-Based Location Management Scheme for PCS Network

Location management provides the guarantee to deliver a call to mobile user during the mobility of user and it is a key challenge in wireless cellular networks. In this paper, we are introducing a new index-based location management scheme. It is based on indexing of location update information at the home agent of network. A tuple of index will keep track of range of location update information and corresponding thread of it, connected to stack of information table. To register a new mobile user, the mobile switching centre will generate a new identification number with the help of mobile switching centre identification number and temporary mobile subscriber identity of subscriber. If, the identification number is with in the range of index then, the Care of Address of mobile subscriber is added to information table else, the index will be reconstruct based on new range of identification number. It has been observed that in proposed technique, the call setup delay and network overheads is reduces over the limitation of minor increment of registration delay. The analytical model and numerical result represents the effectiveness of proposed scheme over the existing schemes.     

Affordable Mobile TV Services in Hybrid Cellular and DVB-H Systems

Mobile TV services are expected to become a key application in future wireless networks. The recently proposed terrestrial digital broadcast technology, DVB-H, especially designed for mobile services, is regarded as a powerful alternative to the 3G cellular networks that already offer these services out on a point-to-point basis. Unfortunately, the cost of supporting real-time streaming and full area coverage seems to be very high compared to fixed TV services. In this article we discuss hybrid IP datacast DVB-H and 3G systems as a possible solution for providing affordable network infrastructure and services. Our approach is DVB-H centric. The 3G cellular system plays the role of providing interactivity, error reporting, and repair for the DVB-H broadcast channel. To enable an easy and efficient interworking of DVB-H and 3G, we employ forward error correction at the application layer with digital fountain coding. The main way to provide lower cost services is to avoid full DVB-H area coverage from the beginning and to perform an incremental DVB-H network deployment that follows the user demand. In this direction, to hide the discontinuity in coverage from the perception of users, we propose to take advantage of the bursty character of DVB-H transmissions and the mobility of users. This is possible by sending additional parity data, either with the DVB-H or the cellular network, in the time intervals between original service bursts. We evaluate the potential DVB-H infrastructure cost savings determined by transmitting additional parity data in DVB-H when targeting vehicular users. The implications of delivering parity data through the cellular network also are discussed. The numerical investigations show a potential for significant cost savings compared with the traditional approaches     

IP Paging Service for Mobile Hosts

In wireless networks, mobile hosts must update the network with their current location in order to get packets delivered. Paging facilitates efficient power management at the mobile host by allowing the host to update the network less frequently at the cost of providing the network with only approximate location information. The network determines the exact location of a mobile host through paging before delivering packets destined to the mobile host. In this paper, we propose the concept of paging as an IP service. IP paging enables a common infrastructure and protocol to support the different wireless interfaces such as CDMA, GPRS, wireless LAN, avoiding the duplication of several application layer paging implementations and the inter-operability issues that exist today. We present the design, implementation, and detailed qualitative and quantitative evaluation, using measurements and simulation, of three IP-based paging protocols for mobile hosts.     

基于地面广播的手机电视

手机电视业务可以利用蜂窝移动网络和地面/卫星数字广播来实现,其相关技术有4种:基于移动网实现技术、基于地面数字广播网实现技术、基于卫星实现技术和基于应用层实现技术。DVB-H和T-DMB是2种典型的地面数字广播电视标准,前者是DVB组织为通过地面数字广播网络向手持终端提供多媒体业务所制订的传输标准,后者是韩国推出的基于欧洲厂商开发的尤里卡147数字音频广播(Eureka-147DAB)的地面数字多媒体广播标准。目前开展手机电视业务面临着标准、频率资源、管制和终端等方面的问题,其运营模式存在移动运营商单独运营、广电单独运营和两者合作运营模式3种。手机电视是广电和通信产业融合的重要尝试,主管部门的协调和技术标准的制订将直接影响未来三网融合的进程。     

Route Optimization Using Tree Information Option for Nested Mobile Networks

Mobile IP is the basic solution to provide host mobility, whereas network mobility refers to the concept of collective mobility of a set of nodes. In the simplest scenario, a mobile network moves as a single unit with one mobile router (MR) that connects it to the global Internet. Also, multiple mobile networks can be nested in a hierarchical form, e.g., a wireless personal area network (PAN) in a vehicular network. In a nested mobile network, multiple MRs form a tree hierarchy in which the root MR is called the top-level mobile router (TLMR). Nested mobile networks exhibit the pinball routing problem, which becomes worse in proportion to the number of nested levels in the hierarchy. To solve this problem, we propose a routing optimization scheme using a tree information option (ROTIO) that extends the NEMO basic support protocol. In the ROTIO scheme, each MR in the nested mobile network sends two binding updates (BUs): one to its home agent and the other to the TLMR. The former BU contains the TLMR's home address, while the latter contains routing information between the issuing MR and the TLMR. This alleviates the pinball routing problem significantly. Now, a packet from a correspondent node only needs to visit two transit nodes (the home agents of the MR and the TLMR), regardless of the degree of nesting. Moreover, the ROTIO scheme provides location privacy and mobility transparency. We also extend ROTIO to perform routing between two mobile network nodes inside the same nested mobile network more efficiently and to substantially reduce the disruption when a mobile network hands off.     

Optimal Distributed Location Management in Mobile Networks

An important issue in the design of future Personal Communication Services (PCS) networks is the efficient management of location information. In this paper, we consider a distributed database architecture for location management in which update and query loads of the individual databases are balanced. We obtain lower bounds to the worst-case delay in locating a mobile user, to the average delay, and to the call blocking probability. We then propose a dynamic location management algorithm that meets these lower bounds. The optimality of this algorithm with respect to these three performance measures, as well as simplicity, make it an appealing candidate for distributed location management in PCS networks.     

Wireless Internet access for mobile subscribers based on theGPRS/UMTS network

With the advent of IP technologies and the tremendous growth in data traffic, the wireless industry is evolving its core networks toward IP technology. Enabling wireless Internet access is one of the upcoming challenges for mobile radio network operators. The General Packet Radio Service is the packet-switched extension of GSM and was developed to facilitate access to IP-based services better than existing circuit-switched services provided by GSM. We illustrate how a visited mobile subscriber on a GPRS/UMTS network can access his/her home network via the gateway GPRS support node (GGSN). We also propose some implementation ideas on wireless Internet access for a remote mobile subscriber based on a GPRS/UMTS network     

Integrated Mobility Management Methods for Mobile IP and SIP in IP based Wireless Data Networks

With developments in voice over IP (VoIP), IP-based wireless data networks and their application services have received increased attention. While multimedia applications of mobile nodes are served by Session Initiation Protocol (SIP) as a signaling protocol, the mobility of mobile nodes may be supported via Mobile IP protocol. For a mobile node that uses both Mobile IP and SIP, there is a severe redundant registration overhead because the mobile node has to make location registration separately to a home agent for Mobile IP and to a home registrar for SIP, respectively. Therefore, we propose two new schemes that integrate mobility management functionality in Mobile IP and SIP. We show performance comparisons among the previous method, which makes separate registration for Mobile IP and SIP without integration, and our two integrated methods. Numerical results show that the proposed methods efficiently reduce the amount of signaling messages and delay time related to the idle handoff and the active handoff.     

Dynamic Self-Optimization of the Antenna Tilt for Best Trade-off Between Coverage and Capacity in Mobile Networks

One major factor influencing the coverage and capacity in mobile networks is related to the configuration of the antennas and especially the antenna tilt angle. By utilizing antenna tilt, signal reception within a cell can be improved and interference radiation towards other cells can be effectively reduced, which leads to a higher signal-to-interference-plus-noise ratio received by the users and increased sum data rate in the network. In this work, a method for capacity and coverage optimization using base station antenna electrical tilt in mobile networks is proposed. It has the potential to improve network performance while reducing operational costs and complexity, and to offer better quality of experience for the mobile users. Our solution is based on the application of reinforcement learning and the simulation results show that the algorithm improves significantly the overall data rate of the network, as compared to no antenna tilt optimization. The analysis in this paper focuses on the downlink of the cellular system. For the simulation experiments a multicellular and sectorized mobile network in an urban environment and randomly distributed user terminals are considered. The main contribution in this work is related to the development of a learning algorithm for automated antenna tilting.     

Verifiable Distributed Oblivious Transfer and Mobile Agent Security

The mobile agent is a fundamental building block of the mobile computing paradigm. In mobile agent security, oblivious transfer (OT) from a trusted party can be used to protect the agent’s privacy and the hosts’ privacy. In this paper, we introduce a new cryptographic primitive called Verifiable Distributed Oblivious Transfer (VDOT), which allows us to replace a single trusted party with a group of threshold trusted servers. The design of VDOT uses a novel technique called consistency verification of encrypted secret shares. VDOT protects the privacy of both the sender and the receiver against malicious attacks of the servers. We also show the design of a system to apply VDOT to protect the privacy of mobile agents. Our design partitions an agent into the general portion and the security-sensitive portion. We also implement the key components of our system. As far as we know, this is the first effort to implement a system that protects the privacy of mobile agents. Our preliminary evaluation shows that protecting mobile agents not only is possible, but also can be implemented efficiently. This work was supported in part by the DoD University Research Initiative (URI) program administered by the Office of Naval Research under grant N00014-01-1-0795. Sheng Zhong was supported by ONR grant N00014-01-1-0795 and NSF grants ANI-0207399 and CCR-TC-0208972. Yang Richard Yang was supported in part by NSF grant ANI-0207399. A preliminary version of this paper was presented at the DialM-POMC Joint Workshop on Foundations of Mobile Computing in 2003. Sheng Zhong received his Ph.D. in computer science from Yale University in the year of 2004. He holds an assistant professor position at SUNY Buffalo and is currently on leave for postdoctoral research at the Center for Discrete Mathematics and Theoretical Computer Science (DIMACS). His research interests, on the practical side, are security and incentives in data mining, databases, and wireless networks. On the theoretical side, he is interested in cryptography and game theory. Yang Richard Yang is an Assistant Professor of Computer Science at Yale University. His research interests include computer networks, mobile computing, wireless networking, sensor networks, and network security. He leads the LAboratory of Networked Systems (LANS) at Yale. His recent awards include a Schlumberger Fellowship and a CAREER Award from the National Science Foundation. He received his B.E. degree from Tsinghua University (1993), and his M.S. and Ph.D. degrees from the University of Texas at Austin (1998 and 2001).     

A Two-Tier Heterogeneous Mobile Ad Hoc Network Architecture and Its Load-Balance Routing Problem

The mobile ad hoc network (MANET) has attracted a lot of interest recently. However, most of the existing works have assumed a stand-alone MANET. In this paper, we propose a two-tier, heterogeneous MANET architecture which can support Internet access. The low tier of the network consists of a set of mobile hosts each equipped with a IEEE 802.11 wireless LAN card. In order to connect to the Internet and handle the network partitioning problem, we propose that the high tier is comprised of a subset of the mobile hosts, called gateways, which can access to cellular/infrastructure networks. The high tier is heterogeneous in the sense that the network interfaces in the gateway hosts could be IEEE 802.11 cards, PHS handsets, or GPRS handsets characterized by different bandwidths and latencies. Observing that the gateways could become the bottlenecks of the two-tier network, we propose a set of solutions, namely boundary-moving, host-partitioning, and probabilistic solutions, to solve the load-balance routing issue. Implementation issues/concerns of these schemes are discussed. Simulation results are presented to compare these load-balance routing schemes.