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BIBEBUVAMaster of Science in EngineeringSeamless Gateway-Handover in Ad Hoc NetworksMobile Information and Communication TechnologyThesis advisor: Prof. Dr. Ulrich FiedlerExpert: Prof. Dr. Torsten Braun, University of BernIn disaster recovery and public safety, wireless ad hoc networks are a promising approach for mobile broadbandcommunication. Big challenges in such multi-hop wireless networks include seamless connectivityand seamless handover for broadband real-time traffic like video transmissions among different gatewaysto a fixed network. In this thesis we have designed and implemented a demonstrator to show that seamlessgateway-handover for real-time videoconferencing traffic is feasible when employing off-the-shelf low-costequipment. In- and outdoor tests look promising.Christoph GussetFigure 1: a) Cell handover from doted to dashed wireless link in single-hopcellular wireless networks such as GSM, UMTS and LTE. b) Gateway handoverfrom doted to dashed wireless path in a multi-hop wireless ad hoc network.Mobile publicaly available communicationservices are based on cellularwireless single-hop networkarchitectures (GSM, UMTS,LTE), where only the last hop ispremised on a wireless medium asshown in figure 1a).In rescue operations, disaster recoveryand other crisis managementscenarios up to military operations,the use of publiclyavailable networks is either notpossible or not appropriate. Autonomouscommunication systemsare utilised – but these today’s mobileradio networks support onlynarrow bandwidth.In future, upcoming wireless networkconcepts can provisionbroadband connectivity in crisismanagement scenarios – even forreal-time traffic like video transmissions.A not damaged fix installed telecommunicationinfrastructure canbe expanded by rescue forcesfrom outside into a disaster areawith a wireless ad hoc network:transportable and mobile wirelessnodes have to be placed for networkcoverage extension and buildupautomatically a multi-hopwireless ad hoc network, interconnectedto a fix installed corenetwork by multiple gateways.When a mobile terminal with its mobilewireless node is movingaround, the network has to choosedynamically the optimal path betweenthe communication partners.Therefore, two types of handovercan occur: a handover inside thewireless ad hoc network (intra-domain)and a gateway-handover(inter-domain) between the mobilenode and the communication partnerin the core network. The secondcase is similar to a cell handoverin cellular networks, but morecomplex due to the multi-hop networkcharacteristic.For real-time traffic, every handovermust happen in a seamless waywithout any interruption of runningtransmissions.A seamless gateway-handover protocolfor real-time traffic was designedand a demonstrator wasimplemented.The demonstrator consists of acore network and a multi-channelmulti-radio wireless ad hoc networkwith three gateways, two fixed wirelessnodes and one mobile wirelessnode as shown in figure 1b).This demonstrator was evaluated ina realistic setting towards its abilityto guarantee seamless connectivityfor real-time traffic like IP live videostreaming and IP videoconferencing.From our tests in-house and outdoorwe conclude that seamlessgateway-handover for broadbandreal-time traffic is feasible.26 ti.bfh.ch