Mobile Ad hoc Networks: Modelling, Simulation and Broadcast Based Applications

Luc Hogie

Projet Mascotte


Over the last few years, personal communication devices have invaded most developed countries and today, the majority of the population owns a mobile phone and most of them use personal digital assistants, mobile computers, etc. This tendency is reinforced and occurs at the same time with a new trend: most of these devices get equipped with one or several wireless networking interfaces. Practically, Wi-Fi or/ and Bluetooth-enabled devices become of frequent use. More than allowing the connection to some access point (as they can be found in airport, train stations, city-centers, restaurants, etc), these interfaces permit also to interconnect directly with one another in a decentralized way and to hence self-organize into ad hoc networks. A mobile ad hoc network (MANET) is a set of mobile nodes able to communicate with other nodes in their surroundings. These wireless communications happen in a peer-topeer manner, without relying on any predefined infrastructure. Today, MANETs are mainly used for sensing, gaming and military purposes. But the steadily wider adoption of wireless technologies in daily life let one foresee the next generation of MANETs applications: environmental and medical monitoring, groupware, customer-to-customer applications, risk management, entertainment, advertising, etc. In order to enable the development and spreading of these applications, a number of issues have to be solved. First, in such network, end-to-end connectivity cannot be guaranteed. Indeed MANETs may be partitioned and nodes may be sporadically present in the network. As such, MANETs can be considered as Delay Tolerant Networks (DTN). Second, the topology of the network changes over time because of the mobility of the stations. Then, the way the communication primitives were implemented in the context of wired networks is no longer applicable. It is hence necessary to propose new algorithms to enable those primitives, like broadcasting that serves as a basic pattern for the design of many MANETs applications. The design and implementation of such communication schemes, and more generally of MANETs application, can be achieved using two different ways: either by building a real network, or by resorting to modelling and simulation. In the context of this work, where city-scale environment were considered, simulation was hence unavoidable. The development of such a simulator took place at the crossroad of some projects in relation to complex system modelling, optimization and middleware design for MANETs, and conducted in several European countries. This diversity led to the design of a custom simulator called Madhoc. Madhoc captures the major characteristics of DTNs, by providing an extendable set of mobility models as well as a framework for the de_nition of new applications. Madhoc was primarily used for the investigation of the broadcasting issue. In this specific context, networks composed of thousands devices using a variety of wireless technologies were considered. These networks are partitioned and exhibit heterogeneous densities. This led to the design of a bandwidth-efficient broadcasting protocol called DFCN.<

Luc Hogie
[Projet Mascotte]