In ad hoc network, one needs other nodes to relay data packets. But resources in each node are limited. Therefore, these nodes may not relay other¡¦s data packet without getting any benefit. In this paper, a routing path selecting algorithm based on price mechanism is proposed. It helps nodes to get some benefits by relaying others¡¦ data packets. Moreover, the algorithm we proposed selects a routing path with less payment and more resources. Simulation results show that the drop rate, block rate and the cost of routing paths are reduced compared to the competing algorithms.

With rapidly development of wireless network technology in the past few years, hand-held devices can connect to Internet everywhere conveniently by equipped with wireless card. IEEE 802.11 defined two types of wireless networks: infrastructure networks and ad hoc networks. Since ad hoc networks are a kind of networks without access points, efficient routing is an important issue for these networks. A more efficient routing approach involves dividing the network into several clusters by using a clustering algorithm. The purpose of this paper is to investigate a hybrid cluster routing algorithm in mobile ad hoc networks. This investigation proposed a double-manager K-hop clustering algorithm based on the link evaluation. This algorithm not only can elect a more suitable node as the cluster head but also can reduce the overhead of the managers. Furthermore, this study devised maintenance and backup mechanisms to stabilize network performance in the face of network topology changes. The simulation results demonstrate that our proposed algorithm outperforms other clustering algorithm in terms of number of clusters, routing overhead of managers and cluster stability.

Since gateways are usually used to integrate the Internet and MANET (Mobile Ad Hoc Network), the gateway discovery approaches is important for mobile nodes in MANET to obtain the route to gateways. The hybrid gateway discovery approach can be configured through adjustment of the single parameter, the TTL (Time-to-live) of the advertisement. This thesis aims to develop an adaptive gateway discovery algorithm to adjust the TTL of advertisement by estimating the control overhead and then effectively adjusts the generation of control overhead in the integrated network. Through the simulation, we demonstrate that this adaptive gateway discovery algorithm can adjust the appropriate TTL of advertisement in different number of mobile nodes which desire to access Internet.

Effective routing is critical in mobile ad hoc networks (MANETs). In recent years, many hierarchical routing protocols have been proposed to build a backbone structure for supporting MANET routing, especially for large scalability. The clustering approach is seen as the first step in providing a flat network with a hierarchical architecture. The clusterheads become the backbone nodes (BNs), which use greater power to transmit packets, forming the backbone network. Backbone network routing can reduce the number of data-packet forwarding hops throughout the entire network. However, previous protocols have focused on clustering schemes. Fault tolerance in a backbone structure has not been considered. In this paper, we propose a backup routing scheme that can repair broken links locally without activating a route re-discovery procedure. The backup route is piggybacked in the data packet header to achieve the most durable route. The proposed method can improve the packet delivery ratio and reduce control overhead, compared to general hierarchical routing protocols.

Multi-channel MAC protocol is that schedules frames to be exchanged on different channels. To analyze the performance of multi-channel MAC protocol, an analytical model is proposed to compute the network throughput. Simulation results show that the proposed model is able to model the behaviors of multi-channel MAC protocol accurately. Furthermore, based on the analysis model, in this thesis we also proposes an adaptive contention window scheme to enhance the network throughput by tuning the initial contention window size. Results indicate that the proposed scheme can reduce the cost of collisions and increase the network throughput.

In an ad hoc networks, it is an important problem about how to increase the bandwidth utilization and guarantee Quality-of-Service. In order to increase the bandwidth utilization under the situation of limited bandwidth, we want to achieve the target by using the bitty residual bandwidth in the ad hoc networks. Hence we integrate several single paths into a multi-path that satisfies QoS requirement. In this paper, we present a policy to look up, maintain, and reroute the virtual circuit in the ad hoc networks. From the result of simulation, we obtain that our proposal indeed can increase the bandwidth utilization of ad hoc networks. But the condition of splitting also increases the overhead of connection, and affects the forced terminated ratio and packets lost ratio under mobility.

Ad hoc wireless networks are quite convenient local area networks. Because ad hoc wireless networks have a property what its topology is changed as hosts move. In order to efficiently and quickly broadcasting data, it is very important to have efficacious protocols in MAC (Medium Access Control) layer. In this paper, we propose a new broadcast protocol, Contention-based Broadcast Protocol (CBP). CBP is a TDMA-based protocol. There are three characteristics which make CBP an efficient protocol. They are (1) CBP utilize a backoff algorithm and some mini slot in contention request phase to avoid collisions. Most protocols do not implement a backoff algorithm. (2) A host only reserves a data slot each time instead of many slots in most TDMA-based protocol. It has the advantage of reducing the influence of host mobility because the time between a data slot is reserved and the time the data slot is utilized has greatly decreased, and (3) CBP differentiates unicast data and broadcast data and allows a host to reuse by channel for a unicast if it is impossible for a broadcast.

In this paper we propose a distributed algorithm to construct a scatternet for multi-hop ad hoc networks of Bluetooth devices. This algorithm is fully distributed and does not require the nodes in the networks being in-range(i.e., each pair of nodes in the network may be unable to communicate with each other directly). The role-selection process in existing scatternet formation mostly uses the strategy of message exchange and comparing their weights like IDs or power strength. This results in a large amount of control messages to be sent and a longer scatternet formation time. In our algorithm, the role selection procedure is simple. Nodes can decide their role by a randomly generated counter rather than their ¡¥weights¡¦. According to the proposed approach, nodes can determine their role of either a master or a slave of the piconet without recognizing its neighbors¡¦ ¡¥weight¡¦. The algorithm performs better time and reduces the number of control messages remarkably during the role-selection process. In this paper, we also define the gateways of 2-hops and 3-hops for evaluating the distance between two piconets.

Most existent protocols, applications and services for Mobile Ad Hoc NET-works (MANETs) assume a cooperative and friendly network environment and do not accommodate security. Therefore, Intrusion Detection Systems (IDSs), serving as the second line of defense for information systems, are indispensable for MANETs with high security requirements. Central to the research described in this dissertation is the proposed two-level nonoverlapping Zone-Based Intrusion Detection System (ZBIDS) which fit the unique requirement of MANETs. First, in the low-level of ZBIDS, I propose an intrusion detection agent model and present a Markov Chain based anomaly detection algorithm. Local and trusted communication activities such as routing table related features are periodically selected and formatted with minimum errors from raw data. A Markov Chain based normal profile is then constructed to capture the temporal dependency among network activities and accommodate the dynamic nature of raw data. A local detection model aggregating abnormal behaviors is constructed to reflect recent subject activities in order to achieve low false positive ratio and high detection ratio. A set of criteria to tune parameters is developed and the performance trade-off is discussed. Second, I present a nonoverlapping Zone-based framework to manage locally generated alerts from a wider area. An alert data model conformed to the Intrusion Detection Message Exchange Format (IDMEF) is presented to suit the needs of MANETs. Furthermore, an aggregation algorithm utilizing attribute similarity from alert messages is proposed to integrate security related information from a wider area. In this way, the gateway nodes of ZBIDS can reduce false positive ratio, improve detection ratio, and present more diagnostic information about the attack. Third, MANET IDSs need to consider mobility impact and adjust their behavior dynamically. I first demonstrate that nodes?? moving speed, a commonly used parameter in tuning IDS performance, is not an effective metric for the performance measurement of MANET IDSs. A new feature -link change rate -is then proposed as a unified metric for local MANET IDSs to adaptively select normal profiles . Different mobility models are utilized to evaluate the performance of the adaptive mechanisms.

This dissertation focuses on the design and analysis of distributed primitives for mobile ad hoc networks, in which mobile hosts are free to move arbitrarily. Arbitrary mobility adds unpredictability to the topology changes experienced by the network, which poses a serious challenge for the design and analysis of reliable protocols. In this work, three different approaches are used to handle mobility. The first part of the dissertation employs the simple technique of ignoring the mobility and showing a lower bound for the static case, which also holds in the mobile case. In particular, a lower bound on the worstcase running time of a previously known token circulation algorithm is proved. In the second part of the dissertation, a self-stabilizing mutual exclusion algorithm is proposed for mobile ad hoc networks, which is based on dynamic virtual rings formed by circulating tokens. The difficulties resulting from mobility are dealt with in the analysis by showing which properties hold for several kinds of mobile behavior; in particular, it is shown that mutual exclusion always holds and different levels of progress hold depending on how the mobility affects the token circulation. The third part of the dissertation presents two broadcasting protocols which propagate a message from a source node to all of the nodes in the network. Instead of relying on the frequently changing topology, the protocols depend on a less frequently changing and more stable characteristic — the distribution of mobile hosts. Constraints on distribution and mobility of mobile nodes are given which guarantee that all the nodes receive the broadcast data.