An ad-hoc network is the cooperative engagement of a collection of mobile nodes without the required intervention of any centralized access point or existing infrastructure. In this paper we present Ad-hoc On Demand Distance Vector Routing (AODV), a novel algorithm for the operation of such ad-hoc networks. Each Mobile Host operates as a specialized router, and routes are obtained as needed (i.e., on-demand) with little or no reliance on periodic advertisements. Our new routing algorithm is quite suitable for a dynamic selfstarting network, as required by users wishing to utilize ad-hoc networks. AODV provides loop-free routes even while repairing broken links. Because the protocol does not require global periodic routing advertisements, the demand on the overall bandwidth available to the mobile nodes is substantially less than in those protocols that do necessitate such advertisements. Nevertheless we can still maintain most of the advantages of basic distance-vector routing mechanisms. We show that our algorithm scales to large populations of mobile nodes wishing to form ad-hoc networks. We also include an evaluation methodology and simulation results to verify the operation of our algorithm.

Abstract — IP-based solutions to accommodate mobile hosts within existing internetworks do not address the distinctive features of wireless mobile computing. IP-based transport protocols thus suffer from poor performance when a mobile host communicates with a host on the fixed network. This is caused by frequent disruptions in network layer connectivity due to — i) mobility and ii) unreliable nature of the wireless link. We describe the design and implementation of I-TCP, which is an indirect transport layer protocol for mobile hosts. I-TCP utilizes the resources of Mobility Support Routers (MSRs) to provide transport layer communication between mobile hosts and hosts on the fixed network. With I-TCP, the problems related to mobility and the unreliability of wireless link are handled entirely within the wireless link; the TCP/IP software on the fixed hosts is not modified. Using I-TCP on our testbed, the throughput between a fixed host and a mobile host improved substantially in comparison to regular TCP. 1

We present extensions to a traditional cellular [Ses95] handoff system to handle the simultaneous operation of multiple wireless network interfaces. This new system allows mobile users to roam in a "Wireless Overlay Network" structure consisting of room-size, building-size, and wide-area data networks. In this structure, the user can connect to the wired network through multiple wireless subnets, and offers the best possible connectivity given the user's geographic location and local wireless connectivity. We present the basic handoff system and show that the handoff latency is bounded by the amount of time that the mobile host takes to discover that it has moved in or out of a new wireless overlay. To efficiently support applications that can not tolerate these disruptions, we present optimizations to this basic scheme that assume no knowledge about specific channel characteristics. For handoffs between room-size and building-size overlays, these optimizations lead to a handoff latenc...

Mobile computing is a new emerging computing paradigm posing many challenging data management problems. We identify these new challenges and investigate their technical significance. New research problems include management of location dependent data, information services to mobile users, frequent disconnections, wireless data broadcasting, and energy efficient data access. 1 Introduction The rapidly expanding technology of cellular communications, wireless LAN, and satellite services will make it possible for mobile users to access information anywhere and at anytime. In the near future, tens of millions of users will be carrying a portable computer, often called a personal digital assistant or a personal communicator. Smaller units will run on AA batteries and may be diskless; larger units will run on Ni-Cd packs. These larger units will be powerful laptop computers with large memories and powerful processors. Regardless of size, all mobile computers will be equipped with a wireless...

Over the past few years, Transmission Control Protocol (TCP) has become the most widely used transport layer protocol on the Internet. TCP performs poorly however, if one of the communicating hosts is a mobile wireless computer [6]. One way to address this performance problem is to modify TCP to make it aware of host mobility. Such an approach

Networking protocols are being modified to handle mobility of hosts. This paper argues that there is a need to make mobility explicit at every level of the OSI model --- even above the network level through user or application level. Further, it is proposed that the mobile host and the first hop (wireless link) of communication be handled differently than the rest of the network. Hence, in networks with mobile hosts, we propose a radical approach of indirect interaction between clients and servers. 1 Introduction The client-server paradigm has served well for structuring applications in distributed systems. The paradigm is implicitly based on two assumptions: 1) the end points of the communication link are fixed and 2) the underlying network infrastructure is to a large extent homogeneous (high bandwidth, reliable, and low latency). However, mobile hosts have different characteristics from fixed hosts. Mobility implies that hosts will connect from different access points and ma...

This article summarizes the results of the BARWAN project, which focused on enabling truly useful mobile networking across an extremely wide variety of real-world networks and mobile devices. We present the overall architecture, summarize key results, and discuss four broad lessons learned along the way. The architecture enables seamless roaming in a single logical overlay network composed of many heterogeneous (mostly wireless) physical networks, and provides significantly better TCP performance for these networks. It also provides complex scalable and highly available services to enable powerful capabilities across a very wide range of mobile devices, and mechanisms for automated discovery and configuration of localized services. Four broad themes arose from the project: 1) the power of dynamic adaptation as a generic solution to heterogeneity, 2) the importance of cross-layer information, such as the exploitation of TCP semantics in the link layer, 3) the use of agents in the infrastructure to enable new abilities and to hide new problems from legacy servers and protocol stacks, and 4) the importance of soft state for such agents for simplicity, ease of fault recovery, and scalability.

and have found that it is complete and satisfactory in all respects, and that any and all revisions required by the final examining committee have been made.

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Mobile Computing is a new emerging computing paradigm of the future. Data Management in this paradigm poses many challenging problems to the database community. In this paper we identify these new challenges and plan to investigate their technical significance. New research problems include management of location dependent data, wireless data broadcasting, disconnection management and energy efficient data access. 1 Introduction The rapidly expanding technology of cellular communications, wireless LAN, wireless data networks, and satellite services will give mobile users capability of accessing information anywhere and anytime. In the near future, tens of millions of users will carry a portable (palmtop, laptop) computer (often called personal digital assistant (PDA) or personal communicator) with wireless connection to a worldwide information network. Coming years will most likely be the decade of mobile or nomadic computing. This vision poses new challenging problems to the databas...