We present an overview of ad-hoc routing protocols that make forwarding decisions based on the geographical position of a packet's destination. Other than the destination 's position, each node needs to know only its own position and the position of its one-hop neighbors in order to forward packets. Since it is not necessary to maintain explicit routes, position-based routing does scale well even if the network is highly dynamic. This is a major advantage in a mobile ad-hoc network where the topology may change frequently. The main prerequisite for position-based routing is that a sender can obtain the current position of the destination. Therefore, recently proposed location services are discussed in addition to position-based packet forwarding strategies. We provide a qualitative comparison of the approaches in both areas and investigate opportunities for future research.

This paper outlines our experience with the implementation and deployment of two MANET routing protocols on a five node, four hop, network. The work was prompted by the lack of published results concerning the issues associated with the implementation of MANET routing protocols on actual wireless networks, as opposed to results of simulation experiments. We examined implementations of two distance vector MANET routing protocols and found a number of problems with both protocols during the course of our experiments. The most significant was that neither protocol could provide a stable route over any multi-hop network connection. The route discovery process of both protocols is fooled by the transient availability of network links to nodes that were more than one hop away. Packets transmitted over a fading channel cause the routing protocol to conclude incorrectly that there is a new one hop neighbor that could provide a lower metric (hop count) route to even more distant nodes. This can occur even when nodes are stationary, mobility resulted in even less route stability. We implemented a simple signal strength based neighbor selection procedure to test our assertion that fading channels and unreliable network links were the cause of the failure of the routing protocols. The result was that neighbor discovery and the filtering for neighbors with which nodes could communicate reliably enables the creation of reliable multihop routes. Based on our experiences, we outline several recommendations for future work in MANET research. 1.

In this paper we investigate the use of ad-hoc routing algorithms for the exchange of data between vehicles. There are two main aspects that are of interest in this context: the specific characteristics of ad-hoc networks formed by vehicles and the applicability of existing ad-hoc routing schemes to networks that display these characteristics. In order to address both aspects we generate realistic vehicular movement patterns of highway traffic scenarios using a well validated traffic simulation tool. Based on these patterns we show that the characteristics of vehicular ad-hoc networks are quite different from the frequently used random waypoint model. We then proceed to evaluate the performance of a reactive ad-hoc routing protocol (DSR) and of a position-based approach (greedy forwarding as done in GPSR) in combination with a simple reactive location service. Our analysis suggests that for vehicular networks where communication spans more than 2 or 3 hops position-based ad-hoc routing has significant advantages over reactive non-position-based approaches both in the number of successfully delivered packets and in routing overhead.

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Abstract. This paper proposes a novel communication pattern for mobile multihop ad-hoc networks which is based on a marketplace metaphor. In order to substantially increase the probability that negotiating peers sucessfully reach an agreement, communication is focused on a static geographic area, called the marketplace. Users are not constrained to be at the marketplace physically, but are allowed to utilize other ones mobile devices located at the marketplace to let a software agent or a service installed on each device negotiate with others on their behalf. The forwarding and negotiation protocols needed to implement the marketplace solution are described in this work. Additionally, a prototypical implementation of the protocols is evaluated in a simulation environment. Since simulation results strongly depend on the mobility model, three realistic models based on an extension of the random waypoint model are used. Their movement patterns are resulting from persons on a music festival, a university campus, and an exhibition. 1

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We extensively analyze the short (and long) term fairness performance of wireless ad hoc networks. The primary goal of our study was to investigate how multi-hop routing in an ad hoc network would affect the fairness of the MAC layer. Recently the fairness of the MAC layer of such systems has been studied. We demonstrate that higher-level protocols must also be considered when studying fairness. We analyze the behavior of a network using DSR and DSDV as an ad hoc routing protocol. The MAC layer used was IEEE 802.11. The study is carried out for a wide range of independent parameters. These include: (i) network topology, (ii) the number of connections and their spatial location and (iii) the injection rate and burstiness of individual connections.

Routing protocols in ad hoc networks can be generally categorized as proactive and reactive. Previous studies [1] have shown that on-demand (reactive) routing protocols perform a lot better in terms of high throughput and low overhead especially with node mobility. On-demand protocols (e.g.DSR, AODV) employ efficient route caching mechanisms to avoid unnecessary route discovery floods and robust route maintenance mechanisms to deal with frequent route breaks. Most performance studies of ad hoc routing use long-lived randomly assigned connections that usually last throughout the simulation duration. These connections emulate file transfer (ftp) or user-specific constant bit rate (CBR) applications. Such simulations mainly capture route maintenance/repair phase in addition to the initial route discovery/setup phase of the routing protocols. However, for short-lived small transfers routing protocols may exhibit significantly different behavior. Small transfers may include resource discovery...

The advancement in information technology and the need for large-scale communication infrastructures has triggered the era of Wireless Sensor Networks (WSNs). Mobile ad-hoc network (MANET) is a network of wireless mobile nodes which communicate with each other without any centralized control or established infrastructure. Routing is the process of selecting paths in a network along which data is to be sent. Routing is a critical task in MANET where the nodes are mobile. Dynamic and reliable routing protocols are required in the ad-hoc wireless networks, as they have no infrastructure (base station) and their network topology changes. There are various protocols for handling the routing problem in the ad-hoc wireless network environment. In this paper focus is given on studying the performance evaluation of various routing protocols using Qualnet simulator 5.0.2. The performance of the proactive, reactive and hybrid protocols are analyzed with different node densities for mobile and stationary nodes. The metrics used for the performance evaluation include average jitter, throughput, packet delivery ratio and average end to end delay.

Ad hoc networking allows hosts to communicate without the benefit of fixed infrastructure.