Simone Leggio

A Power-Aware Broadcasting Algorithm

Flooding is an expensive operation that is often required in the operation of mobile ad hoc networks (MANETs). In this paper, we present a novel algorithm to reduce the overhead imposed by flooding operations. The algorithm improves previous results by using a distributed function to elect the nodes that will provide the highest additional coverage to previous retransmissions. The algorithm does not require any signalling or impose special requirements on the participating devices

Achieving seamless mobility in IP-based radio access networks

A handover in any IP-based mobile network is a complex procedure. Typically, it takes quite a long time before the new access router gets the parameters describing the flow states associated with an incoming mobile node. It may even be that the new access router does not have enough resources to support the rerouted flows. Thus, it is crucial to select from several candidate access routers the one that best fits the mobile nodes requirements. This article describes the candidate access router discovery protocol, which can be used to select a suitable new access router. We also address the context transfer architecture that makes use of the candidate access router discovery protocol and aims to reduce the time required to recover flow descriptor parameters. Finally, we discuss how the two protocols can intemperate to achieve seamless handovers.

A framework for seamless service interworking in ad-hoc networks

Local area wireless networks are becoming commonplace in our everyday lives. It would be beneficial to establish such wireless networks in an ad-hoc manner so that they are infrastructure-free. In the current IP networks, various infrastructure elements play cordial roles, and most of the service-related Internet technologies cannot be deployed in infrastructure-free ad-hoc networks. In this paper, we develop mechanisms for seamless service interworking in ad-hoc networks: first, finding devices, people and services in an ad-hoc environment, and then establishing communications sessions between two or more parties. To guarantee interworking with current networks, we reuse as much as possible well-known client-server Internet technologies and with minimal changes modify them to be applicable in a peer-to-peer manner in ad-hoc networks. We have developed methods for service discovery, session management, and security support that can be used in infrastructure-free ad-hoc networks. We have verified the developed methods with a proof-of-concept implementation in a WLAN testbed network. We also evaluated the realized implementation, in terms of bandwidth and CPU consumption. We present the evaluation results to conclude the paper.

SIPCache: A Distributed SIP Location Service for Mobile Ad-Hoc Networks

Internet-based communication is currently in a hype. People utilize Internet services more and more to communicate with each other, e.g., via VoIP or chat. The next step would be to reutilize the same applications to achieve ubiquitous communication, anytime and anywhere, also where network support is not available, such as in ad-hoc networks. Existing Internet protocols must be modified for working in the ad-hoc server-less environment. The session initiation protocol (SIP) is a fundamental element in the Internet for establishing multimedia communication sessions. However, SIP cannot be used in ad-hoc networks, as it relies on the support of SIP servers in the network; e.g, in ad-hoc networks it is not possible to locate SIP users since the assistance of a dedicated SIP server is missing. A solution for this problem is presented in this paper which describes and evaluates a fully decentralized mechanism for locating SIP users in ad-hoc networks

An Internet SIP Gateway for Ad-hoc Networks

Various forms of ad-hoc networking are slowly emerging. However, a wider diffusion of ad-hoc networking in everyday life will only be possible if existing common applications are adapted for use in ad-hoc networks. There has been some work on adapting Internet-based applications to function in ad-hoc networks. Yet, in order to make ad-hoc networking even more useful and interesting to people, applications must also be able to connect to the Internet. Many new Internet applications are based on sessions, e.g., instant messaging, VoIP and multimedia communications. The session initiation protocol (SIP) is a popular protocol to manage sessions in IP networks, based on centralized servers, and application-level routing. However, in order to establish SIP sessions between an ad-hoc network and the Internet, some logic must be built in the ad-hoc gateway node to make messages flow correctly to and from the ad-hoc network. In this paper, we present an intelligent SIP gateway that makes it possible to route messages properly between ad-hoc networks, and the Internet, even when the ad-hoc IP addresses are not globally routable

Seamless service interworking of ad-hoc networks and the Internet

Ad-hoc network research has traditionally focused on radio-specific challenges and packet routing. In order to make ad-hoc networking feasible in practise, we also need to consider how actual Internet protocols and applications can be supported. This paper presents our work on service discovery, session management and security for ad-hoc networks. Together with our previous work, the overall design enables secure service discovery and SIP-based communication in ad-hoc networks, and, when a gateway exists, communications between nodes in the ad-hoc network and the Internet. Towards the end of the paper, we will also address practical implementation issues.