This paper describes two techniques that improve throughput in an ad hoc network in the presence of nodes that agree to forward packets but fail to do so. To mitigate this problem, we propose categorizing nodes based upon their dynamically measured behavior. We use a watchdog that identies misbehaving nodes and a pathrater that helps routing protocols avoid these nodes. Through simulation we evaluate watchdog and pathrater using packet throughput, percentage of overhead (routing) transmissions, and the accuracy of misbehaving node detection. When used together in a network with moderate mobility, the two techniques increase throughput by 17% in the presence of 40% misbehaving nodes, while increasing the percentage of overhead transmissions from the standard routing protocol's 9% to 17%. During extreme mobility, watchdog and pathrater can increase network throughput by 27%, while increasing the overhead transmissions from the standard routing protocol's 12% to 24%.

In this paper we consider a large population of mobile stations which are interconnected by a multihop wireless net. The applications of this wireless infrastructure range from ad hoc networking (e.g., collaborative, distributed computing) to disaster recovery (e.g., fire, flood, earthquake), law enforcement (e.g., crowd control), search-and-rescue and battlefield. Key characteristics of this system are the large number of users, their mobility and the need to operate without the support of a fixed (wired or wireless) infrastructure. The last feature sets this system apart from existing cellular systems and in fact makes its design much more challenging. In this environment, we investigate routing strategies which scale well to large populations and can handle mobility. In addition, we address the need to support multimedia communications, with low latency requirements for interactive traffic and Quality of Service (QoS) support for real time streams (voice/video). In the wireless rout...

Most ad hoc mobile devices today operate on batteries. Hence, power consumption becomes an important issue. To maximize the lifetime of ad hoc mobile networks, the power consumption rate of each node must be evenly distributed, and the overall transmission power for each connection request must be minimized. These two objectives cannot be satisfied simultaneously by employing routing algorithms proposed in previous work. In this article we present a new power-aware routing protocol to satisfy these two constraints simultaneously; we also compare the performance of different types of power-related routing algorithms via simulation. Simulation results confirm the need to strike a balance in attaining service availability performance of the whole network vs. the lifetime of ad hoc mobile devices.

In this paper we address the problem of routing in a large wireless, mobile network such as found in the automated battle field or in extensive disaster recovery operations. Conventional routing does not scale well to network size. Likewise, conventional hierarchical routing cannot handle mobility efficiently. In this paper, we propose a novel soft state Wireless HIerarchical Routing protocoL (WHIRL). We distinguish between the "physical" routing hierarchy (dictated by geographical relationships between nodes) and "logical" hierarchy of subnets in which the members move as a group (e.g., company, brigade, battalion in the battlefield). WHIRL keeps track of logical subnet movements using Home Agent concepts akin to Mobile IP. A group mobility model is introduced and the performance of the WHIRL is evaluated through a detailed wireless simulation model.

In this paper, we propose some improvements to the flooding protocols that aim to efficiently broadcast a given information through the whole ad-hoc network. These improvements are based on probabilistic approach and decrease the number of emitted packets and hence, the medium occupation. Indeed, it is more interesting to privilege the retransmission by nodes that are located at the radio border of the sender. We observe that the distance between two nodes with full duplex communication can be approximated by comparing their neighbor lists. This leads to broadcasting schemes that do not require position or signal strength information of nodes. Moreover, proposed broadcast protocols require only knowledge of one hop neighborhood and thus need only short hello message. Such protocols are more able to support high mobility networks than protocols that need knowledge of two or more hops neighborhood and then need longer hello messages. We compare our new schemes with variable density and experiments show that the probabilistic approach is efficient.

In an ad hoc wireless network, mobile hosts are acting as routers and the network topology is constantly changing due to node mobility. The disruptions can cause serious degradation for real-time session. This paper describes a new protocol, the Flow Oriented Routing Protocol (FORP), for routing real-time IPv6 flows (e.g., voice and data) in highly mobile ad hoc wireless networks. A new concept called "multi-hop handoff" is introduced to anticipate topological changes and perform rerouting, thus limiting the disruption of a flow due to the changing topology. The performance of the proposed scheme is compared to other routing approaches. 1 Introduction An ad hoc wireless network differs from a conventional cellular wireless network in that it does not have a fixed infrastructure. An ad hoc network is used in situations such as emergency disaster relief, law enforcement, or fast deployment of military units in unpopulated areas. Since real-time applications like voice and video are imp...

A Mobile Ad hoc NETwork (manet) is a mobile, multi-hop wireless network which is capable of autonomous operation. It is characterized by energy-constrained nodes, bandwidth-constrained, variable-capacity wireless links and dynamic topology, leading to frequent and unpredictable connectivity changes. In the absence of a fixed infrastructure, manet nodes cooperate to provide routing services, relying on each other to forward packets to their destination. Routing protocols designed for the fixed network are not effective in the dynamic and resource-constrained manet environment; many alternative routing protocols have been suggested. This report provides an overview of a number of manet routing protocols. More importantly, it defines a taxonomy that is suitable for examining a wide variety of protocols in a structured way and exploring tradeoffs associated with various design choices. The emphasis is on practical design and implementation issues rather than complexity analysis.

Whereas routing protocols for mobile wireless ad hoc networks are well advanced, the support of Quality-ofService in such networks has only recently emerged as a major research topic. Several proposals combine routing concepts with mechanisms for QoS support, at the same time making assumptions as have been made for the QoS support in wired networks. This paper examines the practical applicability of approaches to QoS with respect to the differences between wired and wireless ad hoc networks. Furthermore, a novel approach for service differentiation in wireless networks is proposed and early simulation results on the performance are presented.

A classical problem caused by nodes movement in an ad hoc network is partitioning. Predicting those partitions could be a very useful feature that can be provided to applications in a mobile ad-hoc network environment. Indeed, being aware of a future disconnection in the network can help to ensure a better quality of service by adapting the application behavior. Algorithms already exists to do this but they need position information to be provided by a positioning system. This paper propose an original link robustness evaluation method based on the notion of disjoint paths which allow efficient partition detection without using any kind of positioning system. 1

In wireless communication environment, the information broadcast based on the flooding protocol leads to an overload of network bandwidth (each mobile node has to send the broadcasted message). So, each node has to obtain medium access and transmit its data. However, in dense network (e.g. more than 15 nodes per communication space) the collision probability (in MAC layer) is very high and the number of lost packets is then important. In this paper, we propose some improvements of the flooding protocols that aim to efficiently broadcast a given information through the whole network. These variants are based on stochastic approach and decrease the number of emitted packets and hence, the medium occupation.