Showing papers by "Xiaoyan Hong published in 2009"

Multiple Radio Channel Assignement Utilizing Partially Overlapped Channels

Abstract: Existing channel assignment algorithms designed for multi-radio multi-channel wireless mesh networks (MRMC-WMN) mainly deal with orthogonal or nonoverlapped channels. But in reality, the limited availability of orthogonal channel is a major issue where the network is very dense in terms of inter-nodal distances. On the other hand, partially overlapped channels (POC) are currently considered as a great potential for increasing the number of simultaneous transmissions and eventually upgrading the network capacity; especially in case of MRMC-WMN. In this paper, we address the limited orthogonal channel problem by exploring the usable POCs. The key technique lies in the fact that the interference between adjacent channels has to be considered intelligently in order to increase the overall capacity. Our contributions include a new interference model I-Matrix that helps selecting channels with less interference and a POC-based channel assignment algorithm. We evaluate the performance of our POC based algorithm in terms of capacity by comparing with the one using only orthogonal channels. Our results show capacity improvement as the increased link assignments at an average of more than 15 percent.

A survey of anonymity in wireless communication systems

Abstract: Anonymity is an important security aspect of wireless communications and has continuously attracted significant attention. Implementing anonymity of mobile users not only protects their privacy but also reduces the chances of attacks based on impersonation; therefore security can be improved. Untraceability is a related issue to anonymity. If a user is traceable, its hidden identity can be revealed through profiling the activities associated to a user. In this paper, we conduct a survey on anonymity issues of wireless communication systems. We first discuss general issues of anonymity in wireless communication systems. Then we survey some protocols in the literature, which are designed for wireless mobile systems as well as wireless ad hoc networks. Copyright © 2008 John Wiley & Sons, Ltd.

Articulation Node Based Routing in delay tolerant networks

Abstract: Routing in delay tolerant networks (DTNs) is a challenging problem in networking research. Existing DTN routing solutions have used many approaches to increase the success rate of message delivery, such as meeting probabilities between nodes, packet replication and flooding. One important feature of these protocols is using local connection information to find the “best” path with high likelihood to deliver a packet. In this paper, we propose a new routing protocol called ANBR (Articulation Node Based Routing). From a global view, a general disconnected network can have many small instantaneously clustered mobile nodes. Mobility allows nodes carrying messages to deliver them to other clusters. Selecting appropriate nodes to carry and deliver messages becomes important in order to reduce message delay and overhead. The proposed ANBR tackles this issue by utilizing articulation nodes among a local sub-graph formed by including all neighbors of two “meeting” nodes. Articulation nodes are the articulation points or cut vertices of this local sub-graph, and by definition are the nodes, whose removal will disconnect the graph. Thus, these articulation nodes are more likely to be able to deliver messages outside the local cluster. Packets will be buffered in these nodes and forwarded to other articulation nodes when they meet. The process repeats until messages reach their destinations. We evaluate our algorithm by using real world data from the MIT reality mining project. The simulation results show that ANBR algorithm performs better than related protocols in terms of delivery rate and efficiency.

An online energy-efficient routing protocol with traffic load prospects in wireless sensor networks

Abstract: In wireless sensor networks, many routing algorithms are designed to implement energy-efficient mechanisms. Among those, some focus on maximising an important performance index called network lifetime, which is the number of messages successfully delivered in the network before a failure. In this paper, we propose a new online algorithm taking the goal of prolonging network lifetime. When making routing decisions, our algorithm, named Traffic-Aware Energy Efficient (TAEE) routing protocol, utilises prospective traffic load information for further load balance, in addition to power-related metrics used in an enhanced cost function in calculating least cost paths. An algorithm for automatic parameter adaption is also described. To better accommodate to large-scale sensor networks, we further introduce a random grouping scheme which enables hierarchical TAEE routing to run within and cross the dynamically formed groups to reduce computation and routing overhead, while maintaining global energy efficiency. Our simulation shows that compared with the leading power-aware Max-min Zp MIN protocol, the TAEE protocol generates better performance in terms of network lifetime without jeopardising network capacity.

Selective Message Forwarding in Delay Tolerant Networks

Abstract: It is challenging to deliver messages in a network where no instant end-to-end path exists, so called delay-tolerant network (DTN). Node encounters are used for message forwarding. In this paper, we propose a DTN routing protocol SMART. SMART utilizes the travel companions of the destinations (i.e. nodes that frequently meet the destination) to increase the delivery opportunities while limiting message overhead to a bounded number. Our approach differs from related work in that it does not propagate node encounter history nor the delivery probabilities derived from the encounter history. In SMART, a message source injects a fixed number of message copies into the network to forward the message to a companion of the destination, which only forwards the message to a fixed number of the destination's companions. Our analysis and simulation results show that SMART has a higher delivery ratio and a smaller delivery latency than the schemes that only use controlled opportunistically-forwarding mechanism and has a significantly smaller routing overhead than a pure flooding scheme.

Time-Based Confidentiality Enhancement Scheme for Mobile Wireless Networks

Abstract: A multi-hop wireless network with highly dynamic members and mobility is vulnerable to many attacks. To address this problem, we propose a novel time-based approach that exploits mobility. In our scheme, the source sends shares at different times. Due to node mobility, these shares will be routed through different intermediate nodes. It is highly unlikely that a particular intermediate node is able to be on many of these routes and to collect enough shares to reconstruct the original message. The scheme is particularly suitable for applications that can tolerate long message delays, as studied in Delay Tolerant Networks. The article focuses on analyzing the feasibility of this scheme. We describe a general approach to calculate the probability of intercepting enough shares by arbitrary nodes, together with simulations. The results show that the probability is small. The scheme provides a valuable alternative for delay tolerant applications to enhance message confidentiality.

Mobility identification and clustering in sparse mobile networks

Abstract: Non-uniform distributions of mobile nodes are the norm for a mobile network. Often, there can be concentration areas or grouping of nodes. Early work has explored these features to help message disseminations. However, a mobile network application can generate complex mixing mobility patterns that render these work less effective and efficient. In addition, many applications run with in a sparse mode, namely, the network may not be connected all the time. In this paper, we propose two entropy based metrics to identify the nodes with different mobility patterns and further use the metrics to accomplish clustering. Aiming at low-end devices which have no inputs of velocity and location, we employ neighbor information through hello messages and draw speed implication through neighbor change rates. The entropy based metrics are used in a clustering algorithm to find stable nodes as cluster heads. According to the the simulation results, two metrics, namely, speed entropy and relation entropy can be applied to distinguish active nodes from stable nodes in different group mixing configurations. The simulations also show that our new metric-based clustering algorithm generates more stable clusters.

Modeling Worm Propagation through Hidden Wireless Connections

Abstract: The security issue regarding to worm propagation that exploits geographic proximity of wireless enabled devices has raised attentions in recent years. Early work has modeled worm propagation through directly infecting neighboring nodes, e.g., wireless routers and Bluetooth networks. However, there remains new potential wireless connection topology that can assist the spread of worm in a covert way and threat the cyberspace. In this paper, we study a potential worm epidemic pathway that lies in the densely overlapped wireless metropolitan networks and covers large geographic areas. Specifically, the overlapped footprints of neighboring access points can create hidden connections for worms to propagate across the entire wireless network. We present a novel analytical model to analyze the spread speed of this type of worm. The constraints of the nodes within the overlapped footprints, the boundaries set aside by the access point associations, network topology, and density of both access points and users are considered in the model. We also present methods to obtain estimations about propagation delays in an access point coverage and to generate numerical results based on the model. In evaluation, real maps of access points are used to simulate worm propagation and validate the model. The results call for research on detection and defense solutions against worm propagation in wireless networks.

Protection Against Mobile Tracing Through Motion-MIX for Mobile Wireless Nodes

Abstract: Mobile wireless networks, such as mobile ad hoc networks (MANETs), are vulnerable to passive attacks that threaten the privacy of communications. Moreover, threats can now be launched from mobile platforms and with new techniques for eavesdropping, locating, and fingerprinting wireless transmissions. Recently, many wireless anonymous schemes have been studied, and mobility often plays an important role with regard to the effectiveness of wireless anonymity. In this paper, we focus on the impact of node motion behaviors. We first illustrate the emerging anonymity threat of venue privacy attacks (VPAs) to trace mobile wireless nodes. We then propose ldquomotion-MIXrdquo as the countermeasure to defend against the threat. Motion-MIX calls for protection at all the layers of the protocol stack. We further use a new asymptotic security model to verify motion-MIX's effectiveness against VPAs. In a scalable ad hoc network, we prove that the probability of security breach is negligible with respect to the number of network nodes.

Interference minimizing channel assignment using partially overlapped channels in multi-radio multi-channel wireless mesh networks (non-refereed)

Abstract: Channel assignment algorithms revealed so far in the literature for multi-radio multi-channel wireless mesh networks (MRMC-WMN) mainly deals with orthogonal channels (non-overlapped channels). But considering the total number of available orthogonal channels in the case of IEEE 802.11b, which is limited to only 3 channels. Therefore, this lack of availability of assignable channels causes inefficient use of spectrum resources. It is very difficult to design a feasible channel assignment algorithm using only orthogonal channels that is interference-aware and throughput maximizing, whereas it also minimizes switching delay and at the same time makes the best utilization of spectrum resources. We had taken the novel approach of satisfying the above goals through the smartly utilization of partially overlapped channels (POC). We also introduce the notion of a 3D Node-Radio-Channel (NRC) graph model for characterizing the topological structure along with interfaces associated with different channels at each node.

A mobility camouflaging evaluation tool

Abstract: This paper describes an innovative Mobility Camouflaging Evaluation Tool (MCET) for mobile users traveling on a predefined geo-spatial graph. MCET is a customizable platform for evaluating the effectiveness of Mobility Camouflaging Algorithms (MCAs) and Adversary Observation Algorithms (AOAs). AOAs use observations of mobile user wireless transmissions to trace their movements. MCAs are designed to reduce the ability of AOAs to construct accurate traces. Specifically, MCAs camouflage the mobile user's movements by routing them "together" yet attempting to minimize the overhead of additional travel. The AOSs and MCAs that are developed by users and plugged into MCET produce tabular results for evaluation of mobile user movement logs that are also rendered in Google Earth.

Using camouflaging mobility to protect privacy in mobile ad hoc networks

Abstract: Summary The open nature of wireless medium has left wireless communications vulnerable to various privacy attacks. Much research work has been proposed to protect the identity anonymity of communicating parties, the anonymity of network routes and the location privacy of the message source and destination. However, with the advent of new radio identification and localization techniques, more advanced privacy attacks are possible. We describe a new privacy attack in which the adversary tries to infer the itineraries of the nodes in the network. To protect itinerary privacy, we design an algorithm, called � -camouflaging mobility algorithm, which changes the original motion segments of a node into � -shaped camouflaging paths. Itinerary privacy, correspondent privacy, and route privacy are closely related so we propose a comprehensive anonymous routing scheme, called MARS, to protect these privacy goals. MARS exploits camouflaging mobility to protect itinerary privacy and uses motion pseudonyms generated from the camouflaging mobility to protect correspondent privacy and route privacy without using cryptography. Our analysis results show that � -camouflaging mobility algorithm is cost-effective, which can significantly reduce the itinerary exposure probability at a small cost of extra travel distance. Moreover, our network simulation results illustrated that MARS anonymous routing scheme and � -camouflaging mobility algorithm did not reduce network layer performance. Copyright © 2009 John Wiley & Sons, Ltd.

Effects of multiple collaborated data streams in wireless sensor networks

Abstract: Wireless sensor networks, in our paper, MICAz radio boards with sensors attached to them. Allow us to collect many information around us. When multiple collaborated input streams present, understanding the data with correct data fusion algorithms is important. In this paper, we will present the influences of the thresholds on data from wireless sensors. The hardware used in our project is the Berkeley mote MPR2400 and the MTS310 sensor board. The MIB600 is used as the Ethernet gateway interface for the motes. The MTS310 sensor is used successfully in the project to collect data from passing vehicles. The main topic of this project was to implement a form of machine learning by having the back end computer predict with high confidence that there is a vehicle present. The program MoteView is very efficient in configuring and surveying the motes in real time. This paper is an attempt to demonstrate the abilities of the current wireless sensor network technology.

Articulation Node Based Routing in Delay Tolerant Networks.

Abstract: Routing in delay tolerant networks (DTNs) is a challenging problem in networking research. Existing DTN routing solutions have used many approaches to increase the success rate of message delivery, such as meeting probabilities between nodes, packet replication and flooding. One important feature of these protocols is using local connection information to find the “best” path with high likelihood to deliver a packet. In this paper, we propose a new routing protocol called ANBR (Articulation Node Based Routing). From a global view, a general disconnected network can have many small instantaneously clustered mobile nodes. Mobility allows nodes carrying messages to deliver them to other clusters. Selecting appropriate nodes to carry and deliver messages becomes important in order to reduce message delay and overhead. The proposed ANBR tackles this issue by utilizing articulation nodes among a local sub-graph formed by including all neighbors of two “meeting” nodes. Articulation nodes are the articulation points or cut vertices of this local sub-graph, and by definition are the nodes, whose removal will disconnect the graph. Thus, these articulation nodes are more likely to be able to deliver messages outside the local cluster. Packets will be buffered in these nodes and forwarded to other articulation nodes when they meet. The process repeats until messages reach their destinations. We evaluate our algorithm by using real world data from the MIT reality mining project. The simulation results show that ANBR algorithm performs better than related protocols in terms of delivery rate and efficiency.