Lately, the security in wireless network is always a really hot topic. With the popularity of wireless network in our daily life day after day, the issues of connection speed have evolved to emphasize on personal privacy and information security. Due to the complication of membership in wireless network, it is hard to identify every member. We can reference to the security mechanism in wired network, and try to modify it to fit in wireless network. Of course, the wireless devices do not have such strong processing power and resources as personal computers or servers. So when we try to modify the security mechanism in wired network, we should think about the difference between wired and wireless devices. In this paper, we use a special method to establish Ad Hoc network architecture, and SSL ( Security Sockets Layer ) security protocol. Because SSL has been widely implemented and is now the main standard for providing security e-commerce transactions over the Web. Besides, we use ECC ( Elliptic Curve Cryptosystems ) to replace traditional RSA. Though RSA is the most widely used public key cryptosystem today, the implementation of RSA requires expensive computation. Since battery/computing power and bandwidth are scarce in mobile and wireless systems, the use of a computationally intensive cryptosystem, such as RSA, is not a feasible choice in such environments. Then we can establish a security environment in Ad Hoc network. We hope we can take a excellent balance between security and processing complexity. This paper goes toward the direction, and tries to move SSL to wireless networks. We believe that it is a method to give consideration to practical utility and ideal.

Wireless ad hoc networks have been emerged to support applications, in which it is required/desired to have wireless ommunications among a variety of devices without relying on any infrastructure or central managements. In ad hoc networks, wireless devices, simply called nodes, have limited transmission range. Therefore, each node can directly communicate with only those within its transmission range and requires other nodes to act as routers in order to communicate with out-of-range estinations. One of the fundamental operations in ad hoc networks is broadcasting, where a node sends a message to all other nodes in the network. This can be achieved through flooding, in which every node transmits the first copy of the received message. However, flooding can impose a large number of redundant transmissions, which can result in significant waste of constrained resources such as bandwidth and battery power. One of the contributions of this work is to propose efficient broadcast algorithms which can significantly reduce the number of redundant transmissions. We also consider some of the security issues of ad hoc networks. In particular, we carefully analyze the effect of the wormhole attack, which is one of the most severe threats against ad hoc networks. We also propose a countermeasure, which is an improvement over the existing timing-based solutions against the wormhole attack. Finally, in the last chapter, we propose novel point compression techniques which can be used in Elliptic Curve Cryptography (ECC). ECC can provide the same level of security as other public key cryptosystems (such as RSA) with substantially smaller key sizes. Smaller keys can result in smaller system parameters, bandwidth savings, faster implementations and lower power consumption. These advantages make ECC interesting for ad hoc networks with restricted devices.

In this paper, a mobile network is combined with backbone structure to form a hierarchical ad hoc network. Usually, a mobile ad hoc network is assumed to be homogeneous such that each mobile node uses the same radio capability. However, a homogenous ad hoc network suffers from poor scalability. In this thesis we establish a physical (not logical) hierarchical network to solve this problem in which backbone nodes are employed to transmit for long distance using larger radio power at high tier and cluster structure is used to efficiently utilize resources in a wide and dynamic network. We propose a cluster head determination scheme based on the degree variations of nodes. The nodes with minimum degree variation in the neighborhood are considered more stable and will be selected as the cluster heads. The cluster heads form the backbone nodes and other nodes are the cluster members. The information of cluster members and the nodes in neighboring clusters are recorded in a table of cluster head. According to the information, we have the knowledge of whether the destination node is close to the source node and can determine how to route the transmission. Routing is divided into low tier and high tier routing to relieve the workload of backbone network. The simulation results demonstrate that the proposed hierarchical routing in two tiers (HRTT) improves some problems occurred in the flat network.

Wireless ad hoc networks have been emerged to support applications, in which it is required/desired to have wireless ommunications among a variety of devices without relying on any infrastructure or central managements. In ad hoc networks, wireless devices, simply called nodes, have limited transmission range. Therefore, each node can directly communicate with only those within its transmission range and requires other nodes to act as routers in order to communicate with out-of-range estinations. One of the fundamental operations in ad hoc networks is broadcasting, where a node sends a message to all other nodes in the network. This can be achieved through flooding, in which every node transmits the first copy of the received message. However, flooding can impose a large number of redundant transmissions, which can result in significant waste of constrained resources such as bandwidth and battery power. One of the contributions of this work is to propose efficient broadcast algorithms which can significantly reduce the number of redundant transmissions. We also consider some of the security issues of ad hoc networks. In particular, we carefully analyze the effect of the wormhole attack, which is one of the most severe threats against ad hoc networks. We also propose a countermeasure, which is an improvement over the existing timing-based solutions against the wormhole attack. Finally, in the last chapter, we propose novel point compression techniques which can be used in Elliptic Curve Cryptography (ECC). ECC can provide the same level of security as other public key cryptosystems (such as RSA) with substantially smaller key sizes. Smaller keys can result in smaller system parameters, bandwidth savings, faster implementations and lower power consumption. These advantages make ECC interesting for ad hoc networks with restricted devices.

Wireless ad hoc networks have been emerged to support applications, in which it is required/desired to have wireless ommunications among a variety of devices without relying on any infrastructure or central managements. In ad hoc networks, wireless devices, simply called nodes, have limited transmission range. Therefore, each node can directly communicate with only those within its transmission range and requires other nodes to act as routers in order to communicate with out-of-range estinations. One of the fundamental operations in ad hoc networks is broadcasting, where a node sends a message to all other nodes in the network. This can be achieved through flooding, in which every node transmits the first copy of the received message. However, flooding can impose a large number of redundant transmissions, which can result in significant waste of constrained resources such as bandwidth and battery power. One of the contributions of this work is to propose efficient broadcast algorithms which can significantly reduce the number of redundant transmissions. We also consider some of the security issues of ad hoc networks. In particular, we carefully analyze the effect of the wormhole attack, which is one of the most severe threats against ad hoc networks. We also propose a countermeasure, which is an improvement over the existing timing-based solutions against the wormhole attack. Finally, in the last chapter, we propose novel point compression techniques which can be used in Elliptic Curve Cryptography (ECC). ECC can provide the same level of security as other public key cryptosystems (such as RSA) with substantially smaller key sizes. Smaller keys can result in smaller system parameters, bandwidth savings, faster implementations and lower power consumption. These advantages make ECC interesting for ad hoc networks with restricted devices. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

published_or_final_version / abstract / Electrical and Electronic Engineering / Master / Master of Philosophy

Ad hoc networks provide a flexible, infrastructure-free means to communicate between soldiers in war zones, aid workers in disaster areas, or consumers in device-to-device (D2D) applications. Ad hoc networks, however, are stilled plagued by interference. Communication with millimeter-wave (mmWave) devices offers hope to ad hoc networks through higher bandwidth, reduced interference due to directional antennas, and a lighter interference field due to blockage. This report uses a stochastic geometry approach to characterize the one-way and two-way coverage probability of a mmWave ad hoc network with directional antennas and random blockages. The coverage probability in the presence of noise and both line-of-sight and non-line-of-sight interference is analyzed and used to derive the transmission capacity. Several reasonable simplifications are used to derive the transmission capacity. Performance of mmWave is then analyzed in terms of area spectral efficiency and rate coverage. The results show that mmWave networks support larger densities, higher area spectral efficiencies, and better rate coverage compared to microwave ad hoc networks. / text

Cognitive radio is an important technology which aims to improve the spectrum resource utilization and allows a cognitive radio transceiver to detect and sense spectrum holes without causing interference to the primary users (PUs). As a result of the development of cognitive radio technology, the concept of cognitive radio ad hoc networks (CRAHNs) has recently been proposed in the literature, which aims to apply the cognitive radio to traditional ad hoc networks. However, this new network paradigm creates more research challenges than those in classical cognitive radio networks (CRNs). These research challenges in CRAHNs are due to the variable radio environments caused by spectrum-dependent communication links, hop-by-hop transmission, and changing topology. This study will focus on important research topics in spectrum management in scalable CRAHNs driven by local control, such as spectrum sharing, allocation, and mobility. To conduct this study, a local control approach is proposed to enable system-level analysis and protocol-level design with distributed protocols for spectrum sharing. In the local control approach, we can evaluate the system dynamics caused by either protocol-specific parameters or application-specific parameters in CRAHNs, which is hard to explore using existing methods. Moreover, combining the previous evaluations and scaling law analysis based on local control concept, we can design new distributed protocols based on the features of the medium access control (MAC) layer and the physical layer. In this study, the proposed research themes and related research issues surrounding spectrum sharing are discussed. Moreover, justification of the research has been made by experimental and analytical results. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2013-02-04 14:37:45.883

Zhang Jialiang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 51-52). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation and Related Work --- p.1 / Chapter 1.2 --- Organization of the Thesis --- p.3 / Chapter Chapter 2 --- Interference Modeling for Directional Antennas --- p.5 / Chapter 2.1 --- Pair-wise Physical Link Interference Model of Generic Directional Antenna --- p.6 / Chapter 2.2 --- Potential Interference Region --- p.8 / Chapter 2.3 --- Antenna Pattern and Phased Array Antenna --- p.9 / Chapter Chapter 3 --- Null Width of Directional Antennas --- p.12 / Chapter 3.1 --- Concept of Null Width --- p.12 / Chapter 3.2 --- Effective Null Width and Interference --- p.14 / Chapter 3.2.1 --- Probability of Interference --- p.14 / Chapter 3.2.2 --- Scenario of Directional Transmission and Omni-directional Reception --- p.15 / Chapter 3.2.3 --- Scenario of Directional Transmission and Directional Reception --- p.17 / Chapter 3.3 --- Properties of General Effective Beam Width --- p.18 / Chapter 3.4 --- Numerical Scaling Law of Effective Beam Width of Some Particular Antenna Patterns --- p.23 / Chapter 3.5 --- Summary --- p.26 / Chapter Chapter 4 --- Scaling Law of Network Capacity of Wireless Random Networks with Directional Antennas --- p.27 / Chapter 4.1 --- Random Network Model and Network Capacity --- p.27 / Chapter 4.2 --- Node distribution and MAC Protocol --- p.29 / Chapter 4.3 --- Scenario of Directional Transmission and Omni-directional Reception --- p.30 / Chapter 4.3.1 --- Probability of Transmission to be Success and Per-Link (Transport) Throughput --- p.30 / Chapter 4.3.2 --- Scaling Law of Network Capacity --- p.32 / Chapter 4.3.3 --- Concluding Remark --- p.37 / Chapter 4.4 --- Scenario of Directional Transmission and Directional Reception --- p.38 / Chapter 4.4.1 --- Antenna Steering Protocol --- p.39 / Chapter 4.4.2 --- Probability of Transmission to be Success --- p.40 / Chapter 4.4.3 --- Scaling Law of Network Capacity --- p.41 / Chapter 4.4.4 --- Scaling Law of Phased Array Antennas --- p.42 / Chapter Chapter 5 --- Conclusion --- p.44 / Appendix A: Proof of equation (22) --- p.47 / Appendix B: Proof of equation (28) --- p.49 / Appendix C: Constraint on Region of Optimality for pt and r --- p.50 / References --- p.51