Hang Shen

An Adaptive Opportunistic Network Coding Mechanism in Wireless Multimedia Sensor Networks

The network coding technique is promising for improving the performance of video communication in wireless multimedia sensor networks. However, some special characteristics of existing wireless network coding mechanisms degrade the performance of video data delivery. This work begins with a thorough investigation and understanding of the performance limitations of existing wireless network coding mechanisms. On this basis, we propose an Adaptive Opportunistic Network Coding mechanism (AONC) to improve the transmission quality of video stream in wireless multimedia sensor networks. First, we propose a novel asymmetric coding method to process the video data of different lengths. The aim is to improve data exchange gain. Second, we design an opportunistic forwarding strategy based on dynamic priority to ensure that packets have a better chance to be coded and transmitted, thus achieving much higher throughput. Finally, we present a traffic-aware data scheduling algorithm, working together with the above network coding mechanism, to reduce the loss of potential coding opportunities. Our simulation results demonstrate that, compared with the existing typical network coding mechanisms, AONC can greatly enhance video transmission quality and efficiently utilize bandwidth and energy resources.

Performance Evaluation of a Hybrid FEC/ARQ for Wireless Media Streaming

This paper proposes a link-level hybrid FEC/ARQ based on an adaptive forward error correction (adaptive FEC) algorithm for wireless media streaming, in the hope that the media could be played on receivers with high quality. This model, which uses adaptive forward error correction mechanism at the application layer to adjust to the current network condition, can maximize the performance of wireless multimedia communication. Our simulation results and mathematical analysis show that the hybrid FEC/ARQ achieves better quality of media streaming comparing with FEC alone and ARQ alone, in terms of playable frame rate, reliability and real-time performance on the receiving side.

Optimal Deployment and Scheduling with Directional Sensors for Energy-Efficient Barrier Coverage

In recent years, barrier coverage problem in directional sensor networks has been an interesting research issue. Most of the existing solutions to this problem aim to find as many barrier sets as possible to enhance coverage for the target area, which did not consider the power conservation. In this paper, we address the efficient sensor deployment (ESD) problem and energy-efficient barrier coverage (EEBC) problem for directional sensor networks. First, we describe a deployment model for the distribution of sensor locations to analyze whether a target area can be barrier covered. By this model, we examine the relationship between the probability of barrier coverage and network deployment parameters. Moreover, we model the EEBC as an optimization problem. An efficient scheduling algorithm is proposed to prolong the network lifetime when the target area is barrier covered. Simulation results are presented to demonstrate the performance of this algorithm.

ECBRP: An Efficient Cluster-Based Routing Protocol for Real-Time Multimedia Streaming in MANETs

The dynamic characteristics of wireless networks and stringent QoS requirements of multimedia applications identify significant challenges for providing QoS guarantees for real-time multimedia streaming in such wireless environment. QoS routing protocols can decisively contribute to the QoS provision of network systems. This paper proposes an efficient cluster-based routing protocol (ECBRP) for real-time multimedia streaming in mobile ad hoc networks. First, to improve the stability of clusterheads, we introduce a new algorithm of cluster formation, in consideration of the node mobility and connectivity. Second, a link-broken detection mechanism is designed, which is able to distinguish whether packet loss is due to mobility or congestion, and to make proper reaction. This mechanism contributes to reduce route overhead, and to increase the decodable ratio of video frame at the application layer as well. Third, the routing protocol is enhanced via an adaptive packet salvage strategy, in order to alleviate the congestion in consideration of the characteristics of multimedia traffic. Our simulation experiment results demonstrate that the ECBRP leads to more stable cluster formation than the CBRP, and 80% decreases in the frequency of clusterhead changes against CBRP. As a result, the quality of real-time multimedia streaming is improved significantly, in terms of decodable frame ratio, delay and delay jitter, etc.

An Adaptive Queue Management Mechanism for Video Streaming over Mobile Ad Hoc Networks

This paper proposes an Adaptive Queue Management mechanism (AQM) based on bandwidth estimation for real-time multimedia streaming over mobile ad hoc networks. The purpose is to provide the soft QoS guarantee. At first, we use GM (1, 1) model to predict network bandwidth. On this basis, a mathematical model is proposed to determine a reasonable queue length, thus adjusting the queue length dynamically. To evaluate the AQM performance, we generate a set of video streams using NS2 simulation for typical network scenarios. Our statistical and mathematical analyses demonstrate that the AQM improves the performance of multimedia streaming significantly, in terms of packet loss rate and mean end-to-end delay.

Performance Study of a Cross-Layer Based Multipath Routing Protocol for IEEE 802.11e Mobile Ad Hoc Networks

Communication over wireless links identifies significant challenges for routing protocols operating. This paper proposes a Cross-layer design based Multipath Routing Protocol (CMRP) for mobile ad hoc networks, by means of the node energy signal from the physical layer. The purpose is to optimize routing decision and path quality. The nodes’ mobility behavior is predicted using a notion of “Signal Fading Degree, SFD”. Especially, in combination of the IEEE 802.11e standard at the MAC layer, we determine that the IEEE 802.11e makes a significant contribution to performance improvement of CMRP. Performance evaluation of AODV in legacy 802.11 and CMRP in IEEE 802.11e shows that, as a function of speed of node mobility, a tremendous reduction achieved, in metrics such as the average end-to-end delay, route overhead, route discovery frequency, normalized routing load - almost more than 80%, 40%, 40%, and 40%. In the case of varying number of sessions, the reduction for route discovery frequency and normalized routing load are up to 70% and 80%.

Priority-based IEEE 802.15.4 CSMA/CA mechanism for WSNs

The IEEE 802.15.4 standard is widely used in wireless sensor networks (WSNs). In this paper, we propose a priority-based IEEE 802.15.4 carrier sense multiple access with collision avoidance (CSMA/CA) mechanism for WSNs. Considering traffic load and traffic type of sensor nodes, we classify sensor nodes into three types. In our mechanism, different contention parameters are set for nodes with different priority levels, in order that nodes with high priority achieve high probability to access the channel. By modeling the proposed mechanism using a Markov chain, we analyze and compute the successful transmission probability, throughput and energy consumption for nodes with different priority levels. Finally, our numerical results demonstrate that our mechanism performs well for WSNs.

Protecting trajectory privacy: A user-centric analysis

Abstract The existing evaluation methods for location privacy protection mechanism (LPPM) focus mainly on location privacy at the time of issuing a location-based query, and rarely consider trajectory privacy from where multiple successive queries are issued. This paper provides a user-centric analysis of trajectory privacy protection against tracking attacks in presence of quality-loss and energy constraints, focusing on impact of user query behavior within a certain period of time. We consider an attacker with adversarial knowledge on users’ activity and mobility profiles to run tracking attacks, against which users employ LPPMs that incorporate location semantic diversity to maximize trajectory privacy. The attack and defense problems are formalized as a Bayesian Stackelberg game for quantitative analysis. Real location traces are used to assess the LPPMs’ effectiveness, and to find optimal query strategy. The results confirm that query behavior has a significant impact on improving trajectory privacy. Despite increased number of queries to improve trajectory privacy, the effectiveness may be decreased with a longer observation time. At the same query rate, prolonging observation time is beneficial for privacy improvement. We also find that dummy-based LPPM often provides better protection with a stringent energy constraint, while precision-based LPPM performs better under a stringent quality-loss constraint or under a loose energy constraint. At optimal trajectory privacy, quality-loss of precision-based LPPM is lower than that of dummy-based LPPM, but there is an opposite result in terms of energy cost.

L2OR: Low-Cost Low-Complexity Opportunistic Routing for Wireless Sensor Networks

Opportunistic routing can greatly improve energy efficiency in wireless sensor networks (WSNs). An important challenge is the design of a coordination protocol to implement an effective relay selection and prioritization scheme to minimize expected cost. Many existing opportunistic routing protocols often assumed an ideal link-layer, and thus the computed forwarder list may be suboptimal. Worth noting that, the computation complexity of optimal result grows rapidly with size of candidate set when the nonideal link-layer conditions are taken into account. It is, however, not feasible for energy and processing capability constrained WSNs. To address this problem, we propose a low-cost low-complexity opportunistic routing (L2OR) protocol to achieve an energy-efficient data delivery over WSNs. Our research work begins with a thorough investigation and understanding of properties of forwarder list under nonideal link-layer conditions. On this basis, a low-complexity heuristic algorithm is designed to efficiently find a reasonable choice of forwarder list, with an objective of reducing the search space to the size of candidate set. We conduct theoretical analysis and a set of simulation experiments to evaluate the performance of our L2OR. It is shown that, when comparing to typical energy-aware opportunistic protocol, the L2OR can achieve performance improvement in terms of data transmission efficiency as well as energy consumption.

A LINK-LIFETIME BASED DYNAMIC SOURCE ROUTING PROTOCOL (LTDSR) FOR MULTIMEDIA OVER MANETS

Abstract This paper proposes a link‐lifetime based dynamic source routing protocol (LTDSR) to support Soft QoS for multimedia over MANETs, with a series of improved routing mechanisms. First, our research has shown that some routes held in the route cache may become invalid as time passes, due to node mobility. In this work, we introduce a path lifetime based route selection strategy by establishing link lifetimes for routes, so that no node may select already broken routes. A route discovery will be initiated before all the routes in the cache are broken. Second, considering that the routing protocol reacts mistakenly to the transmission failures due to congestion, a cross‐layer design framework is explored to establish a shared link‐state table with nodes’ coordinate and velocity vector; on this basis, the link‐state detection mechanism can identify the cause properly when packet loss occurs, and then coordinate with the routing protocol to avoid unnecessary route updating. Our simulation results demonstrate that the LTDSR improves the quality of multimedia playing significantly, in terms of decodable frame ratio, end‐to‐end frame delay and delay jitter. In addition, the route overhead is greatly reduced.