No description available.

No description available.

Ensuring trustworthiness through mobile nodes is a serious issue. Indeed, securing the routing protocols in Mobile Ad Hoc Network (MANET) is of paramount importance. A key exchange cryptography technique is one such protocol. Trust relationship between mobile nodes is essential. Without it, security will be further threatened. The absence of infrastructure and a dynamic topology changing reduce the performance of security and trust in mobile networks. Current proposed security solutions cannot cope with eavesdroppers and misbehaving mobile nodes. Practically, designing a key exchange cryptography system is very challenging. Some key exchanges have been proposed which cause decrease in power, memory and bandwidth and increase in computational processing for each mobile node in the network consequently leading to a high overhead. Some of the trust models have been investigated to calculate the level of trust based on recommendations or reputations. These might be the cause of internal malicious attacks. Our contribution is to provide trustworthy communications among the mobile nodes in the network in order to discourage untrustworthy mobile nodes from participating in the network to gain services. As a result, we have presented an Elliptic Curve Diffie-Hellman key exchange and trust framework mechanism for securing the communication between mobile nodes. Since our proposed model uses a small key and less calculation, it leads to a reduction in memory and bandwidth without compromising on security level. Another advantage of the trust framework model is to detect and eliminate any kind of distrust route that contain any malicious node or suspects its behavior.

Mesh network is gaining importance as the next generation network for many high speed applications such as multimedia streaming. This is because it is easy and inexpensive to setup mesh networks with mobile and PDA devices and can be used as a private network. Hence research is active in the field of routing protocols and routing metrics to improve the mesh network performance. Though most of the protocols are evaluated based on simulation, we implemented protocols based on a few metrics like Expected Transmission Count (ETX) Per-hop Packet Pair Delay (Pkt Pair) and WCETT (Weighted Cumulative Expected Transmitted Time) to investigate the performance of the network through experiments. An advanced version of DSR protocol called LQSR (Link Quality Source Routing) protocol of Microsoft Research along with MCL (Mesh Connectivity Layer) allows multiple heterogeneous adapters to be used in mesh network. Since wireless adapters of 802.11a standard offer 12 non-interfering channels and 802.11b/g standard offer 3 non-interfering channels, using multiple adapters of different bands operating on non-interfering channels to improve capacity and robustness of mesh networks was also investigated. In this thesis we explore the possibility of increasing the coverage area of Wireless Mesh Networks (WMN) to enhance the capacity of WMN and minimize the problems due to interference. Theoretical achievable capacity to every node in a random static wireless ad-hoc network with ideal routing is known to be where n is the total number of nodes in the network. Therefore, with increasing number of nodes in a network, throughput drops significantly. Our measurements show that throughput in a single WMN for different path length is closer to the throughput with nodes across two WMNs of the same path length. We propose to interconnect the networks by using multiple wireless adapters in a gateway node configured with the SSID of the networks in operation. We exploit the DSR protocol feature of assigning locally unique interface indices to its adapters. Performance of a network depends heavily on the metrics used for routing packets. Different metrics were studied in the thesis by setting up a 10-node testbed with a combination of nodes with single and two radios. Testbed was partitioned into two networks with two gateway nodes. Performance of multi-radio performance with the above metrics was compared with baseline single radio nodes in the network with the same metric. It is found that multi-radio nodes out-perform single radio nodes in the multi-hop scenario. Also, operating multi-mesh networks using multiple interfaces configured to those networks in a gateway node increases the coverage area and robustness without loss of performance.

Ensuring trustworthiness through mobile nodes is a serious issue. Indeed, securing the routing protocols in Mobile Ad Hoc Network (MANET) is of paramount importance. A key exchange cryptography technique is one such protocol. Trust relationship between mobile nodes is essential. Without it, security will be further threatened. The absence of infrastructure and a dynamic topology changing reduce the performance of security and trust in mobile networks. Current proposed security solutions cannot cope with eavesdroppers and misbehaving mobile nodes. Practically, designing a key exchange cryptography system is very challenging. Some key exchanges have been proposed which cause decrease in power, memory and bandwidth and increase in computational processing for each mobile node in the network consequently leading to a high overhead. Some of the trust models have been investigated to calculate the level of trust based on recommendations or reputations. These might be the cause of internal malicious attacks. Our contribution is to provide trustworthy communications among the mobile nodes in the network in order to discourage untrustworthy mobile nodes from participating in the network to gain services. As a result, we have presented an Elliptic Curve Diffie-Hellman key exchange and trust framework mechanism for securing the communication between mobile nodes. Since our proposed model uses a small key and less calculation, it leads to a reduction in memory and bandwidth without compromising on security level. Another advantage of the trust framework model is to detect and eliminate any kind of distrust route that contain any malicious node or suspects its behavior.

Popularity of mobile devices along with the presence of ad hoc networks requiring no infrastructure has contributed to recent advances in the field of mobile computing in ad hoc networks. Mobile ad hoc networks have been mostly utilized in military environments. The recent advances in ad hoc network technology now introduce a new class of applications. In this thesis, we design, implement and analyze a multi-hop ad hoc messenger application using Pocket PCs and Microsoft .Net Compact Framework. Pocket PCs communicate wirelessly with each other using the IEEE 802.11b technology without the use of an infrastructure. The main protocol implemented in this application is based on Dynamic Source Routing (DSR), which consists of two important mechanisms, Route Discovery and Route Maintenance. We adopt DSR since DSR operates solely based on source routing and "on-demand" process, so each packet does not have to transmit any periodic advertisement packets or routing information. These characteristics are desirable for the ad hoc messenger application for which a conversation is source-initiated on-demand. To test our application easily, we have developed a testing strategy by which a mobility configuration file is pre-generated describing the mobility pattern of each node generated based on the random waypoint mobility model. A mobility configuration file thus defines topology changes at runtime and is used by all nodes to know whether they can communicate with others in a single-hop or multi-hops during an experimental run. We use five standard metrics to test the performance of the wireless ad hoc messenger application implemented based on DSR, namely, (1) average latency to find a new route, (2) average latency to deliver a data packet, (3) delivery ratio of data packets, (4) normalized control overhead, and (5) throughput. These metrics test the correctness and efficiency of the wireless ad hoc messenger application using the DSR protocol in an 802.11 ad hoc network that imposes limitations on bandwidth and resources of each mobile device. We test the effectiveness of certain design alternatives for implementing the ad hoc messenger application with these five metrics under various topology change conditions by manipulating the speed and pause-time parameters in the random waypoint model. The design alternatives evaluated include (1) Sliding Window Size (SWS) for end-to-end reliable communication control; (2) the use of per-hop acknowledgement packets (called receipt packets) deigned for rapid detection of route errors by intermediate nodes; and (3) the use of cache for path look-up during route discovery and maintenance. Our analysis results indicate that as the node speed increases, the system performance deteriorates because a higher node speed causes the network topology to change more frequently under the random waypoint mobility model, causing routes to be broken. On the other hand, as the pause time increases, the system performance improves due to a more stable network topology. For the design alternatives evaluated in our wireless ad hoc messenger, we discover that as SWS increases, the system performance also increases until it reaches an optimal SWS value that maximizes the performance due to a balance of a higher level of data parallelism introduced and a higher level of medium contention in 802.11 because of more packets being transmitted simultaneously as SWS increases. Beyond the optimal SWS, the system performance deteriorates as SWS increases because the heavy medium contention effect outweighs the benefit due to data parallelism. We also discover that the use of receipt packets is helpful in a rapidly changing network but is not beneficial in a stable network. There is a break-even point in the frequency of topology changes beyond which the use of receipt packets helps quickly detect route errors in a dynamic network and would improve the system performance. Lastly, the use of cache is rather harmful in a frequently changing network because stale information stored in the cache of a source node may adversely cause more route errors and generate a higher delay for the route discovery process. There exists a break-even point beyond which the use of cache is not beneficial. Our wireless ad hoc messenger application can be used in a real chatting setting allowing Pocket PC users to chat instantly in 802.11 environments. The design and development of the dynamic topology simulation tool to model movements of nodes and the automatic testing and data collection tool to facilitate input data selection and output data analysis using XML are also a major contribution. The experimental results obtained indicate that there exists an optimal operational setting in the use of SWS, receipt packets and cache, suggesting that the wireless ad hoc messenger should be implemented in an adaptive manner to fine-tune these design parameters based on the current network condition and performance data monitored to maximize the system performance. / Master of Science