Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2007-09-27 21:48:20.594 / Wireless networks are less reliable than wired networks because channels are “exposed” to the surrounding environment that is susceptible to interference and noise. To minimize losses of data due to collisions, wireless networks need a mechanism to regulate the access on the transmission medium. Medium Access Control (MAC) protocols control access to the shared communication medium so that it can be used efficiently. In this thesis, we first describe the collision-controlled Dual Prohibition Multiple Access (DPMA) protocol [45]. The main mechanisms implemented in DPMA, such as binary dual prohibition, power control, interference control, and support for differentiated services (DiffServ), are presented in detail. We conducted a thorough simulation study on DPMA protocol from several aspects. First, we conduct simulations to observe the effects of binary competition number (BCN), unit slot length and safe margin on the performance of DPMA. Secondly, the DiffServ capability of DPMA is demonstrated through simulation results. Finally, we compare the DPMA protocol with the CSMA/CA protocol and find that DPMA with optimal configuration has better performance than CSMA/CA under both low and high network density. / Master

Localization and coverage are two important and closely related problems in wireless ad hoc networks. Localization aims to determine the physical locations of devices in a network, while coverage determines if a region of interest is sufficiently monitored by devices. Localization systems require a high degree of coverage for correct functioning, while coverage schemes typically require accurate location information. This thesis investigates the relationship between localization and coverage such that new schemes can be devised which integrate approaches found in each of these well studied problems. This work begins with a thorough review of the current literature on the subjects of localization and coverage. The localization scheduling problem is then introduced with the goal to allow as many devices as possible to enter deep sleep states to conserve energy and reduce message overhead, while maintaining sufficient network coverage for high localization accuracy. Initially this sufficient coverage level for localization is simply a minimum connectivity condition. An analytical method is then proposed to estimate the amount of localization error within a certain probability based on the theoretical lower bounds of location estimation. Error estimates can then be integrated into location dependent schemes to improve on their robustness to localization error. Location error estimation is then used by an improved scheduling scheme to determine the minimum number of reference devices required for accurate localization. Finally, an optimal coverage preserving sleep scheduling scheme is proposed which is robust to localization error, a condition which is ignored by most existing solutions. Simulation results show that with localization scheduling network lifetimes can be increased by several times and message overhead is reduced while maintaining negligible differences in localization error. Furthermore, results show that the proposed coverage preserving sleep scheduling scheme results in fewer active devices and coverage holes under the presence of localization error.

Localization and coverage are two important and closely related problems in wireless ad hoc networks. Localization aims to determine the physical locations of devices in a network, while coverage determines if a region of interest is sufficiently monitored by devices. Localization systems require a high degree of coverage for correct functioning, while coverage schemes typically require accurate location information. This thesis investigates the relationship between localization and coverage such that new schemes can be devised which integrate approaches found in each of these well studied problems. This work begins with a thorough review of the current literature on the subjects of localization and coverage. The localization scheduling problem is then introduced with the goal to allow as many devices as possible to enter deep sleep states to conserve energy and reduce message overhead, while maintaining sufficient network coverage for high localization accuracy. Initially this sufficient coverage level for localization is simply a minimum connectivity condition. An analytical method is then proposed to estimate the amount of localization error within a certain probability based on the theoretical lower bounds of location estimation. Error estimates can then be integrated into location dependent schemes to improve on their robustness to localization error. Location error estimation is then used by an improved scheduling scheme to determine the minimum number of reference devices required for accurate localization. Finally, an optimal coverage preserving sleep scheduling scheme is proposed which is robust to localization error, a condition which is ignored by most existing solutions. Simulation results show that with localization scheduling network lifetimes can be increased by several times and message overhead is reduced while maintaining negligible differences in localization error. Furthermore, results show that the proposed coverage preserving sleep scheduling scheme results in fewer active devices and coverage holes under the presence of localization error.

Localization and coverage are two important and closely related problems in wireless ad hoc networks. Localization aims to determine the physical locations of devices in a network, while coverage determines if a region of interest is sufficiently monitored by devices. Localization systems require a high degree of coverage for correct functioning, while coverage schemes typically require accurate location information. This thesis investigates the relationship between localization and coverage such that new schemes can be devised which integrate approaches found in each of these well studied problems. This work begins with a thorough review of the current literature on the subjects of localization and coverage. The localization scheduling problem is then introduced with the goal to allow as many devices as possible to enter deep sleep states to conserve energy and reduce message overhead, while maintaining sufficient network coverage for high localization accuracy. Initially this sufficient coverage level for localization is simply a minimum connectivity condition. An analytical method is then proposed to estimate the amount of localization error within a certain probability based on the theoretical lower bounds of location estimation. Error estimates can then be integrated into location dependent schemes to improve on their robustness to localization error. Location error estimation is then used by an improved scheduling scheme to determine the minimum number of reference devices required for accurate localization. Finally, an optimal coverage preserving sleep scheduling scheme is proposed which is robust to localization error, a condition which is ignored by most existing solutions. Simulation results show that with localization scheduling network lifetimes can be increased by several times and message overhead is reduced while maintaining negligible differences in localization error. Furthermore, results show that the proposed coverage preserving sleep scheduling scheme results in fewer active devices and coverage holes under the presence of localization error.

Localization and coverage are two important and closely related problems in wireless ad hoc networks. Localization aims to determine the physical locations of devices in a network, while coverage determines if a region of interest is sufficiently monitored by devices. Localization systems require a high degree of coverage for correct functioning, while coverage schemes typically require accurate location information. This thesis investigates the relationship between localization and coverage such that new schemes can be devised which integrate approaches found in each of these well studied problems. This work begins with a thorough review of the current literature on the subjects of localization and coverage. The localization scheduling problem is then introduced with the goal to allow as many devices as possible to enter deep sleep states to conserve energy and reduce message overhead, while maintaining sufficient network coverage for high localization accuracy. Initially this sufficient coverage level for localization is simply a minimum connectivity condition. An analytical method is then proposed to estimate the amount of localization error within a certain probability based on the theoretical lower bounds of location estimation. Error estimates can then be integrated into location dependent schemes to improve on their robustness to localization error. Location error estimation is then used by an improved scheduling scheme to determine the minimum number of reference devices required for accurate localization. Finally, an optimal coverage preserving sleep scheduling scheme is proposed which is robust to localization error, a condition which is ignored by most existing solutions. Simulation results show that with localization scheduling network lifetimes can be increased by several times and message overhead is reduced while maintaining negligible differences in localization error. Furthermore, results show that the proposed coverage preserving sleep scheduling scheme results in fewer active devices and coverage holes under the presence of localization error.

No description available.

Ad hoc networks are becoming an interesting research area, as they inher-ently support unique network applications for the wireless communications in a rug-ged environment, which requires rapid deployment and is difficult to be provided by an infrastructure network. Many issues need to be addressed for the ad hoc networks. In this dissertation, we propose an efficient distributed coordination function, a dynamic rate adaptation and fragmentation scheme, and a simultaneous frame transmission scheme on the media access control protocol to enhance the power conservation of mobile hosts and to im-prove the network throughput of an ad hoc network. Extensive simulations are studied to evaluate the improvement of the proposed schemes. The results of the simulations exhibit significant improvement to the stan-dard access control protocol. Not only the improvement of the throughput of the ad hoc networks, but also the conservation of the battery power of the mobile hosts were achieved with our schemes.

Wireless networks are less reliable than wired networks because channels are “exposed” to the surrounding environment that is susceptible to interference and noise. To minimize losses of data due to collisions, wireless networks need a mechanism to regulate the access on the transmission medium. Medium Access Control (MAC) protocols control access to the shared communication medium so that it can be used efficiently. In this thesis, we first describe the collision-controlled Dual Prohibition Multiple Access (DPMA) protocol [45]. The main mechanisms implemented in DPMA, such as binary dual prohibition, power control, interference control, and support for differentiated services (DiffServ), are presented in detail. We conducted a thorough simulation study on DPMA protocol from several aspects. First, we conduct simulations to observe the effects of binary competition number (BCN), unit slot length and safe margin on the performance of DPMA. Secondly, the DiffServ capability of DPMA is demonstrated through simulation results. Finally, we compare the DPMA protocol with the CSMA/CA protocol and find that DPMA with optimal configuration has better performance than CSMA/CA under both low and high network density. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2007-09-28 16:25:02.515

Wireless mobile internet market is still an unprecedented, uncaptured territory for cellular service providers. The shortage and high cost of downlink data bandwidth in a cellular network has remained a huge factor for the slow growth of data services in mobile devices. Although there has been a significant evolution in telephony infrastructures in form of 3G and 4G systems, the potential of high speed ad hoc network for sharing cellular spectrum have not been realized to its full potential. Like (e.g. Verizon) users can share voice minutes with friends, there is a potential for sharing the unutilized cellular bandwidth among friends to increase net data speed. In a scenario like a football stadium where people visit in groups, although a lone phone cannot stream a high quality replay video, unused cellular bandwidth of proximate friend’s devices can automatically be used in real time to view the replays. An available secondary ad hoc network such as Wi-Fi or Bluetooth in phone can be used for sharing this cellular bandwidth. Thus, we propose BuddyShare, a novel social-based automatic bandwidth sharing overlay platform on short range ad hoc devices to increase net data speed. The motivation stems from the fact that the location of mobile users tends to be clustered to form “people hotspots” such as conferences, stadiums, stations, buses and trains. For example, in a scenario like a football stadium where people visit in groups, although a lone phone cannot stream a high quality replay video, unused cellular bandwidth of proximate friends’ devices can automatically be used in real time to view the replays. Our work creates an overlay on horizontal ad hoc network to enable users to form a group among socially trusted members who can collaboratively share their data connections. Social trust is automatically derived from social relationships obtained by mining mobile-phone behavior pattern. This work aims to improve the overall utilization of the data connection, and increase the data rate of individual users without compromising their privacy and unauthenticated usage. The user privacy is preserved by using the bandwidth resources of only socially trusted member of the user, which also guarantees against unauthenticated exploitation of expensive bandwidth. Our proposed work promises to deliver win-win situation to users, content providers and service providers. The advantages of users are: 1) Increased data rate for the same cost.2) Secure and trusted overlay based communication for sharing resources. The advantages for the service providers are manifold: 1) Customer increase: More customers will avail the data plan due to social influence. 2) Customer retention: [18] Customers part of the social-cum-adhoc network are least likely to leave the network.3) Group subscription: Service provider can get bulk subscriptions as collaborative groups increase data rate. In this work, we address some key technical issues of developing a socially aware overlay collaborating medium. Some of the addressed functionalities associated with the overlay formations are group discovery, creation, management and actual data distribution. This proposal also accounts the computation of social trustworthiness by using standard social networking analytics. We also account the several key technical challenges associated with management of overlay on mobile nodes and trust computation using abstract social network. In order to verify the usefulness of BuddyShare, we collected realistic datasets from various sources (questionnaires, mobile device logs, social networking portal) and conducted analyses and simulations on it. The analyses concluded that sample users from the dataset shared sufficient social trustworthiness. The real events from the datasets were captured in the simulations. These simulations showed that, by using Bluetooth as a horizontal ad hoc medium, an user can scale his data speed three times on average for sufficient duration per day. This thesis achieves the following objectives: 1) It presents a comprehensive design for an overlaid social based internet sharing platform called BuddyShare. 2) It presents a social analysis to validate the concept of social trust among users. 3) It delivers a flexible simulation platform to realistically simulate mobile phones with dual interfaces. 4) It presents the results of simulations of real events captured from the device logs of sample users. These results conclude the usefulness of BuddyShare work.

Recent accomplishments in link-level and radio technologies have significantly improved the performance of wireless links. Wireless mobile ad hoc networks, however, typically only take limited advantage of these enhancements. In this research, the medium access control protocol and ad hoc routing protocol are extended to take advantage of radios offering multi-user interference cancellation and direct-sequence spread-spectrum functionality, by encouraging multiple simultaneous connections and adaptively changing communication parameters on a per-packet basis. Through its environment characterization techniques, the adaptive direct sequence spread spectrum MAC protocol for non-broadcast multiple access networks (ADIM-NB) improves several aspects of the wireless mobile ad hoc network performance, including throughput, delay, stability, and power consumption, through its use of spread-spectrum multiple access and four different adaptive algorithms. The four adaptive algorithms change processing gain, forward error correction coding rate, transmit power, and number of simultaneous connections. In addition, the ad hoc routing protocol is extended with the clustering algorithm for mobile ad hoc network (CAMEN). With ADIM-NB in mind, CAMEN discourages the use of broadcast messages, supplements ADIM-NB's functionality at the network level, and improves the network scalability by aggregating nodes into clusters. Both protocols are intended to lead to more powerful and flexible communication capabilities for wireless nodes. Simulation models have been developed and simulated to verify the performance improvements of both protocols at the network-level as well as provide a means to perform trade-off analysis. Results indicate that the network capacity is increased between 50% in a moderately loaded network to 100% in a heavily loaded network over a non-adaptive MAC protocol. The delay also improve significantly in most scenarios of interest. / Ph. D.