Trends in fourth generation (4G) wireless networks are clearly identified by the full-IP concept where all traffic (data, control, voice and video services, etc.) will be transported in IP packets. MObile NETwork (MONET) is a group of mobile nodes moving together as a unit. Such groups are common characteristics of the vehicular environments, for example train and buses (which are attractive because of the high concentration of passengers on these vehicles). This paper investigates an ad hoc networking for Inter-MONET communications and interworking between MONETs and the global Internet. We propose a hierarchical architecture (1) integrating Mobile IPv6 and OLSR, a routing protocol for ad hoc networks, to manage universal mobility and to avoid the nested problem (2) connecting this ad hoc network to the Internet. The heterogeneous communication is established with the help of specific access routers, which serve as gateways. We describe the network scenario, its basic protocol architecture and we discuss the different practical approaches for routing. We validate our proposed architecture by analyses and simulations.

SUMMARYThis paper presents the time-based bandwidth reservation (TBR) algorithm, suitable for handoff management in cellular systems. TBR is based on real-time measurements of mobile stations (position, velocity and acceleration). The scheme consists in sending reservation requests to the neighboring cells based on an extrapolation of the user's motion. The originality of our approach lies in dynamically adjusting the amount of time for which bandwidth has to be allocated and reserved in a cell. In addition, we propose an optimal channel requests arrangement (CRA) algorithm in order to improve the performance of TBR in terms of resource utilization. Finally, we propose VTBR, an adapted and extended version of TBR for better support of vehicular network specifi cities where service degradation or forced call termination may occur owing to frequent handoffs. Detailed simulation results for TBR and VTBR schemes and a comparison with the guard channel scheme are presented. The results show that TBR and VTBR can effi ciently improve the fl ow dropping probability.

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