In the performance evaluation of a protocol for an ad hoc network, the protocol should be tested under realistic conditions including, but not limited to, a sensible transmission range, limited buffer space for the storage of messages, representative data traffic models, and realistic movements of the mobile users (i.e., a mobility model). This paper is a survey of mobility models that are used in the simulations of ad hoc networks. We describe several mobility models that represent mobile nodes whose movements are independent of each other (i.e., entity mobility models) and several mobility models that represent mobile nodes whose movements are dependent on each other (i.e., group mobility models). The goal of this paper is to present a number of mobility models in order to offer researchers more informed choices when they are deciding upon a mobility model to use in their performance evaluations. Lastly, we present simulation results that illustrate the importance of choosing a mobility model in the simulation of an ad hoc network protocol. Specifically, we illustrate how the performance results of an ad hoc network protocol drastically change as a result of changing the mobility model simulated.

Network wide broadcasting in Mobile Ad Hoc Networks provides important control and route establishment functionality for a number of unicast and multicast protocols. Considering its wide use as a building block for other network layer protocols, the MANET community needs to standardize a single methodology that efficiently delivers a packet from one node to all other network nodes. Despite a considerable number of proposed broadcasting schemes, no comprehensive comparative analysis has been previously done. This paper provides such analysis by classifying existing broadcasting schemes into categories and simulating a subset of each category, thus supplying a condensed but comprehensive side by side comparison. The simulations are designed to pinpoint, in each category, specific failures to network conditions that are relevant to MANETs, e.g., bandwidth congestion and dynamic topologies. In addition, protocol extensions using adaptive responses to network conditions are proposed, implemented and analyzed for one broadcasting scheme that performs well in the comparative study.

In recent years, several position-based routing protocols have been developed for mobile ad hoc networks. Many of these protocols assume a location service is available that provides location information on the nodes in the network. In this chapter, we survey all the proposed location information services that exist in the literature to date. We classify these location information services into three categories: proactive location database systems, proactive location dissemination systems, and reactive location systems.

In recent years, many location based routing protocols have been developed for ad hoc networks. This paper presents the results of a detailed performance evaluation on two of these protocols: Location-Aided Routing (LAR) and Distance Routing Effect Algorithm for Mobility (DREAM). We compare the performance of these two protocols with the Dynamic Source Routing (DSR) protocol and a minimum standard (i.e., a protocol that floods all data packets). We used NS-2 to simulate 50 nodes moving according to the random waypoint model. Our main goal for the performance investigation was to stress the protocols evaluated with high data load during both low and high speeds. Our performance investigation produced the following conclusions. First, the added protocol complexity of DREAM does not appear to provide benefits over a flooding protocol. Second, promiscuous mode operation improves the performance of DSR significantly. Third, adding location information to DSR (i.e., similar to LAR) increases both the network load and the data packet delivery ratio; our results conclude that the increase in performance is worth the increase in cost. Lastly, our implementation of DREAM provides a simple location service that could be used with other ad hoc network routing protocols.

This article concerns a variation on multicasting, called geocasting, for an ad hoc network. The goal of a geocast routing protocol is to deliver packets to a group of nodes that are within a specified geographical area, i.e., the geocast region. This paper presents a Geocast Adaptive Mesh Environment for Routing (GAMER) which provides geocast communication in an ad hoc network. GAMER adapts to the current network environment by dynamically changing the density of the mesh. Thus, when nodes are highly mobile, a dense mesh is created; when nodes are moving slowly, a sparse mesh is created. We compare the performance of GAMER with non-adaptive mesh-based geocast routing protocols in an ns-2 simulated ad hoc network. We also compare two versions of GAMER; one version is more active than the other in adapting to the current network environment. We conclude that both versions of GAMER improve the transmission accuracy significantly, without increasing the load on the network significantly, when compared to non-adaptive mesh-based geocast routing approaches.

In order to ease the challenging task of information dissemination in a MANET, we employ a legend: a data structure that is passed around a network to share information with all the nodes. Our motivating application of the legend is sharing location information. Previous research shows that a location service using a legend performs better than other location services in the literature. To improve the legend-based location service, we evaluate three methods for the legend to traverse a network in this paper and compare their performance in simulation. We also explore several improvements to the traversal methods, and describe our way of making the legend transmission reliable.

The Grid Location Service (GLS) is a location service which provides location information for a node in a mobile ad hoc network. A mobile ad hoc network (MANET) is an autonomous system of mobile routers (and associated hosts) connected by wireless links - the union of which form an arbitrary graph. The routers are free to move randomly and organize themselves arbitrarily; thus, the network's wireless topology may change rapidly and unpredictably. GLS provides a mechanism for a node to track the location of other nodes in the network topology. When combined with geographic-based routing protocols, the authors of GLS conclude that it will perform well in a very large mobile ad hoc network. Since the results of GLS look promising, further study of GLS is warranted. Specifically, GLS needs to be compared with other location services and incorporated into a geographic-based routing protocol. In addition to providing an overview of the GLS protocol, this paper reports on our first step toward meeting these goals.

We combine location information and mobility feedback to create an innovative Mobile Ad Hoc Network (MANET) routing protocol which we demonstrate is effective over a wide range of mobility conditions typical in a MANET. We use link duration as our mobility feedback metric, and we demonstrate that mobility feedback using link duration effectively enables adaptive MANET protocols. Using our mobility feedback agent, we develop a hybrid MANET routing protocol which adapts between two MANET routing protocols in order to combine the strengths of both component protocols while avoiding their weaknesses. Our hybrid, adaptive protocol achieves data packet delivery ratios above 80% in VERY demanding network mobility conditions (i.e. link durations less than 4 seconds). In more stable networks (i.e., link durations more than 15 seconds), our protocol achieves data packet delivery ratios above 90%. While other existing MANET routing protocols can achieve similar data packet delivery ratios in more stable networks, no other existing MANET routing protocol can achieve such high performance in VERY unstable networks.

Network wide broadcasting in Mobile Ad Hoc Networks (MANETs) provides important control and route establishment functionality for a number of unicast and multicast protocols. Considering its wide use as a building block for other network layer protocols, the MANET community needs to standardize a single methodology that efficiently delivers a packet from one node to all other nodes. Despite a considerable number of proposed broadcasting schemes, no comprehensive comparative analysis has been previously done. This thesis provides a theory-based and simulation-based comparison of the different protocols. Broadcast protocols are first described and classified into four categories. A run-time analysis of algorithm complexity is performed and a theoretical model to predict the fraction of retransmitting nodes is provided for two protocols. In addition, we simulate a subset of the protocols from each category, thus supplying a condensed but comprehensive side by side comparison. The simulations are designed to pinpoint, in each category, specific failures to network conditions that are relevant to MANETs, e.g., bandwidth congestion and dynamic topologies. Protocol extensions using adaptive responses to network conditions are proposed, implemented and analyzed for one broadcasting scheme that performs well in the comparative study. Two protocols utilizing neighbor knowledge are shown to be most applicable for a wide range of network conditions. Areas of future research are defined to perfect these two protocols, with the hope that one will be chosen as a standard broadcasting scheme by the MANET community.

Previous research has illustrated that locationbased routing protocols improve the effectiveness of mobile ad hoc network (MANET) routing. The goal of a location server, which may be used in conjunction with a locationbased routing protocol, is to provide accurate location information on the mobile nodes in the network. In this paper, we implement a location server for a MANET using our Legend Exchange and Augmentation Protocol (LEAP). We use LEAP to provide a Network Environment Wireless State (NEWS) service. The goal of NEWS is to collect and distribute "news" (such as location information) on the mobile nodes. We compare our legend-based NEWS service to three other location service alternatives via extensive simulations, and illustrate that our LEAP implementation offers both higher accuracy and lower overhead.