Chunxiao Chigan

A Game Theoretic DSA-Driven MAC Framework for Cognitive Radio Networks

The game theoretic dynamic spectrum allocation (DSA) technique is an efficient approach to coordinate the cognitive radios to share the spectrum. However, existing game based DSA algorithms lack a platform to support the game process. On the other hand, existing medium access control (MAC) protocols for cognitive radio (CR) networks do not fully utilize the adaptability and intelligence of the cognitive radio (CR) to achieve efficient spectrum utilization, let alone fairness and QoS support. Therefore it is necessary to develop a DSA-driven MAC protocol with the game theoretic DSA embedded into the MAC layer. In this paper, based on the analysis of challenges for the game theoretic DSA in realistic applications, we conclude that a unified game theoretic DSA-driven MAC framework should constitute of four integral components: 1)DSA algorithm, which derives the steady strategy of each radio to guide the channel access for data communication; 2) negotiation mechanism, which coordinates game players to exchange game information and update their strategies in the right game timing; 3) clustering algorithm, which limits the negotiation of game players in one cluster to solve the scalability issue; 4) cluster based collision avoidance mechanism, which is to avoid collisions among negotiations in different clusters. Subsequently, we design each component to construct an effective DSA-driven MAC framework with low cost. Our proposed game theoretic DSA- driven MAC framework can fulfill the merits of game theoretic DSA algorithms including high spectrum utilization, collision- free channel access for data communication, QoS and fairness support. Through simulations, the merits of the DSA-driven MAC framework are demonstrated.

RPB-MD: Providing robust message dissemination for vehicular ad hoc networks

To improve traffic safety and efficiency, it is vital to reliably send traffic-related messages to vehicles in the targeted region in vehicular ad hoc networks (VANETs). In this paper, we propose a novel scheme, relative position based message dissemination (RPB-MD), to reliably and efficiently disseminate messages to the vehicles in the zone-of-relevance. Firstly, the relative position based (RPB) addressing model is proposed to effectively define the intended receivers in the zone-of-relevance. To ensure high message delivery ratio and low delivery delay, directional greedy broadcast routing (DGBR) is introduced to make a group of candidate nodes hold the message for high reliability. Moreover, to guarantee efficiency, the protocol time parameters are designed adaptively according to the message attributes and local vehicular traffic density. The protocol feasibility is analyzed to illustrate the robustness and reliability of RPB-MD. Simulation results show that RPB-MD, compared with representative existing schemes, achieves high delivery ratio, limited overhead, reasonable delay and high network reachability under different vehicular traffic density and data sending rate.

Countermeasure Uncooperative Behaviors with Dynamic Trust-Token in VANETs

As one special case of the mobile ad hoc networks (MANETs), vehicular ad hoc network (VANET) is featured for its extremely high mobility and constantly changing topology. As a fully distributed network, VANET can work properly only if all the participating vehicles cooperate well during communications. However, lacking centralized coordinators, individual vehicle might be uncooperative for its own benefits. To promote node cooperation and to protect VANET packets during propagation, this paper proposes a dynamic trust-token (DTT) based cooperation enhancement mechanism. DTT utilizes both symmetric and asymmetric cryptography mechanisms to protect packet integrity, and applies neighborhood WatchDog to generate trust token based on instant performance to verify packet correctness. As a result, cooperation among VANET nodes during packet disseminations could be achieved and packet delivery could be well-protected. Performance analysis shows that the latency degradation of the proposed DTT mechanism is negligible.

A Delay-Bounded Dynamic Interactive Power Control Algorithm for VANETs

To enable real-time and robust message delivery, the highly mobile vehicular ad hoc networks (VANETs) call for comprehensive investigation on the dynamic power control effects on the real-time and robust communications. Ideally, by adjusting transmission power adaptively, VANET nodes may agilely cope with the segmentation problem at light vehicular traffic and with the limited system capacity problem at high traffic load. In this paper, we propose a delay-bounded dynamic interactive power control (DB-DIPC) module which is a fully distributed and proactive approach, wherein neighboring nodes periodically and interactively reach each other via power adjustment to maintain run-time connectivity. DB-DIPC algorithm is distributed, asynchronous, fast converging, and capable of interactive learning and calibrating over multiple iterations. With DB-DIPC, the transmission powers of VANET nodes are verified iteratively and interactively by the neighbor vehicles at run-time, which consequently ensures that the prompt 1-op neighbor connectivity to adapt the high VANET dynamics. Our analytical and simulation studies confirm these salient features of the proposed DB-DIPC mechanism.

Cooperation Enhancement for Message Transmission in VANETs

As one special case of the Mobile Ad Hoc Networks (MANET), vehicular ad-hoc networking (VANET) is featured by its high mobility and constantly changing topology. In VANET, nodes can work properly only if the participating vehicles cooperate with each other during communications. However, as a distributed network, individual vehicles might be non-cooperative for their own benefits. In order to prevent non-cooperative vehicles from tampering packet relaying in the network, we propose a cooperation enhancement mechanism using “Neighborhood WatchDog” to generate “Trust Token” based on the first-hand observation. Therefore, trust relationships and packet-acceptance decisions of the receiving nodes are based on the instant observation and the token-proved relaying behavior of the benign neighboring vehicles. With the inherit mapping between the Electronic ID of one vehicle and its public key, keys can be distributed on-the-fly. As a network layer solution, the cooperation enhancement mechanism proposed in this paper is built on the top of our previous proposed Media Access Control (MAC) protocol: Relative Position Based-MAC (RPB-MAC).

Delay-Aware Transmission Range Control for VANETs

End-to-end delay is critical for the real-time safety message delivery in Vehicular Ad Hoc Networks (VANETs). In this paper, we present an analytical model to evaluate the impact of transmission range on the end-to-end delay in 802.11p-based VANETs. Compared with the previous works, our model derives a concise expression of the transmission delay in saturated networks, and obtains the service rate of non-saturated networks with novel methodology. To the best of our knowledge, it is the first complete analytical model that reveals the significant end-to-end delay difference between saturation and non-saturation cases.

Resource-aware self-adaptive security provisioning in mobile ad hoc networks

Providing satisfactory security services in mobile ad hoc networks (MANET) is indispensable for mission critical applications; however, often a highly secure mechanism inevitably consumes a rather large amount of system resources, which in turn may unintentionally cause a security provisioning denial of service (SPDoS) attack. The scheme proposed in this paper sets out a framework to solve this problem by designing a resource-aware self-adaptive network security provisioning scheme. With the support of the offline optimal secure protocol selection module and the online self-adaptive security control module, the framework is capable of deploying different combinations of secure protocols to satisfy different security needs in different conditions for different applications. Consequently, the proposed self-adaptive security provisioning achieves the maximum overall network security services and network performance services, without causing an SPDoS attack. Moreover, it provides additional security capability via security service hopping.

Providing QoS in ubiquitous telemedicine networks

Wireless LANs will play a critical role in providing anywhere and anytime connectivity for ubiquitous telemedicine applications. This paper focuses on how to provide QoS over the wireless channel between the body sensor network (BSN) gateway and the wireless access points (e.g., wireless hotspots in various locations). In the telemedicine application, it usually requires the periodic data and the data related to the occurrence of emergencies to be reported to the remote health care in a timely manner. Unlike the traditional QoS techniques which support voice and data applications, the sporadic nature of the emergency data in telemedicine systems makes it nontrivial to provide sufficient QoS support. In this paper, we first investigated several alternative schemes for emergency QoS support in the telemedicine systems. An express dual channel (EDC) based QoS provisioning mechanism is then proposed. Not only is the proposed mechanism simple and resource efficient, but also it provides the minimum delay for the unpredictable emergency data transmission. Simulation results show the proposed EDC based solution provides satisfactory QoS for ubiquitous telemedicine applications

WSN07-3: RPB-MACn: A Relative Position Based Collision-free MAC Nucleus for Vehicular Ad Hoc Networks

Vehicular ad hoc networks (VANETs) will play a vital role in reducing the number of road accidents and fatalities as well as vehicular traffic optimization. Though an instance of mobile ad hoc networks (MANETs), the highly mobile and dynamic environment of VANET introduces new research challenges. To quickly adapt to the highly mobile and constantly changing topology and still meet the desired application requirements, it is vital for the VANET media access control (MAC) protocol guarantees wireless channel access with minimal delay and minimal exchange of control messages. This paper proposes an innovative relative-position-based MAC Nucleus (RPB- MACn). By combining the dedicated communication channel pair and the dedicated directional antenna associated to the relative position of vehicles, a conceptually contention-free RPB-MACn mechanism for VANET is realized (when coupling with dynamic power control mechanism). Consequently, RPB-MACn can meet all the key requirements of the MAC protocol in a VANET system.

On Joint Privacy and Reputation Assurance for Vehicular Ad Hoc Networks

In vehicular ad hoc networks (VANETs), privacy protection makes it challenging to maintain a long-term reputation of any node, while reputation management requires reputation manifestation at risk of easier vehicle tracking. Here, JPRA is proposed to reconcile these challenging conflicts and support the synergistic coexistence of both indispensible schemes in VANETs. JPRA adopts a localized reputation management model where the behavior evaluation, reputation aggregation, and reputation manifestation of each node are collectively performed by itself and its neighbors. In this model, novel algorithms are designed to support secure and efficient reputation management in face of node mobility and privacy protection. Furthermore, a conditional reputation discretization algorithm ensures privacy-preserving reputation manifestation for the honest nodes. Theoretical analysis and simulations show that JPRA can efficiently and synergistically support both schemes in VANETs.