Jeng Farn Lee

TEAM: Trust-Extended Authentication Mechanism for Vehicular Ad Hoc Networks

The security of vehicular ad hoc networks (VANETs) has been receiving a significant amount of attention in the field of wireless mobile networking because VANETs are vulnerable to malicious attacks. A number of secure authentication schemes based on asymmetric cryptography have been proposed to prevent such attacks. However, these schemes are not suitable for highly dynamic environments such as VANETs, because they cannot efficiently cope with the authentication procedure. Hence, this still calls for an efficient authentication scheme for VANETs. In this paper, we propose a decentralized lightweight authentication scheme called trust-extended authentication mechanism (TEAM) for vehicle-to-vehicle communication networks. TEAM adopts the concept of transitive trust relationships to improve the performance of the authentication procedure and only needs a few storage spaces. Moreover, TEAM satisfies the following security requirements: anonymity, location privacy, mutual authentication, forgery attack resistance, modification attack resistance, replay attack resistance, no clock synchronization problem, no verification table, fast error detection, perfect forward secrecy, man-in-the-middle attack resistance, and session key agreement.

An incentive-based fairness mechanism for multi-hop wireless backhaul networks with selfish nodes

In this paper, we study the fairness problem in multi-hop wireless backhaul networks in the presence of selfish transit access points (TAPs). We design an incentive-based mechanism which encourages TAPs to forward data for other TAPs, and thus eliminates the location-dependent unfairness problem in the backhaul network. We prove the correctness and truthfulness of the proposed mechanism, and evaluate its performance via ns-2 simulations. The results show that the proposed mechanism achieves fairness even when there are idle TAPs in the network.

A practical QoS solution to voice over IP in IEEE 802.11 WLANs

In this article we study the behavior of voice over IP traffic in IEEE 802.11 wireless networks. Specifically, we design a QoS provisioning mechanism for VoIP traffic, and propose a practical solution of configuring the 802.11e enhanced distributed control access parameter sets for different types of traffic. We show that media access control layer only methods may be insufficient, but the demonstrated cross-layer (layers 2, 3, and 4) method works simply and efficiently. We find that the EDCA parameter sets of the access point are not always necessarily set more aggressively than those of wireless stations even though the traffic load of AP is much heavier than the stations. With our mechanism, the EDCA parameter sets can be easily configured via software interface for off-theshelf WiFi phone products, and there is no need to modify the operations of APs or 802.11 MAC layer protocols. The performance of our mechanism is evaluated via ns-2 simulations and via laboratory experiments over Quantas O2 dual mode handsets. The results show our mechanism can provide effective and efficient QoS provisioning for VoIP traffic in IEEE 802.11 WLANs. Since the configuration may be readily configured in the field and the performance is robust across a wide range of environments, we believe that organizations deploying and operating WiFi networks for VoIP may benefit from our work and reduce or eliminate post-deployment tuning and debugging.

SPAM: A Secure Password Authentication Mechanism for Seamless Handover in Proxy Mobile IPv6 Networks

The Internet Engineering Task Force NETLMM Working Group recently proposed a network-based localized mobility management protocol called Proxy Mobile IPv6 (PMIPv6) to support mobility management without the participation of mobile nodes in any mobility-related signaling. Although PMIPv6 reduces the signaling overhead and the handover latency, it still suffers from packet loss problem and long authentication latency during handoff. In addition, there are many security threats to PMIPv6. In this paper, we perform a bicasting scheme for avoiding the packet loss problem, use the piggyback technique to reduce the signaling overhead, and provide a secure password authentication mechanism (SPAM) for protecting a valid user from attacks in PMIPv6 networks. SPAM provides high security properties, including anonymity, stolen-verified attack resistance, location privacy, mutual authentication, forgery attack resistance, no clock synchronization problem, modification attack resistance, replay attack resistance, fast error detection, choose and change password free, and session key agreement. Moreover, SPAM is an efficient authentication scheme that performs the authentication procedure locally and has low computational cost. From the analysis, we demonstrate that our scheme can resist various attacks and provides better performance than existing schemes.

WF2Q-M: Worst-case fair weighted fair queueing with maximum rate control

While existing weighted fair scheduling schemes guarantee minimum bandwidths/resources for the classes/processes of a shared channel, the maximum rate control, which is critical to service providers, carriers, and network managers for resource management and business strategies in many applications, is generally enforced by employing traffic policing mechanisms. These approaches use either a concatenation of the rate controller and scheduler, or a policer in front of the scheduler. The concatenation method uses two sets of queues and a management apparatus that incurs overhead. The latter method may allow bursty traffic to pass through the controller, which violates the maximum rate constraint, or results in packet loss. In this paper, we present a new weighted fair scheduling scheme, WF^2Q-M, which can simultaneously support maximum rate control and minimum service rate guarantees. WF^2Q-M uses the virtual clock adjustment method to enforce maximum rate control and distribute the excess bandwidths of saturated sessions to other sessions without recalculating the virtual starting and finishing times of sessions. In terms of performance, we prove that WF^2Q-M is theoretically bounded by a corresponding fluid reference model. A procedural scheduling implementation of WF^2Q-M is proposed, and a proof of correctness is given. Finally, we present the results of extensive experiments to show that the performance of WF^2Q-M is just as claimed.

A differentiated service model for enhanced distributed channel access (EDCA) of IEEE 802.11e WLANs

In this paper, we propose a new differentiated service model, referred to as Differentiated Service-EDCA (DS-EDCA), for the Enhanced Distributed Channel Access (EDCA) of IEEE 802.11e wireless local area networks (WLANs). With DS-EDCA, both strict priority and weighted fair service can be provided. The strict priority service is provided for high priority traffic through carefully setting the EDCA parameter sets of lower priority traffic; the proportional fairness service is enabled by determining the backoff intervals according to the distributed scheduling discipline (DFS). We also propose a hierarchical link sharing model for IEEE 802.11e WLANs, in which AP and mobile stations are allocated different amounts of link resource. The performance of DS-EDCA and EDCA is compared via ns-2 simulations. The results show that DS-EDCA outperforms the original EDCA in terms of its support for both strict priority and weighted fair service. More importantly, DS-EDCA can be easily implemented, and is compatible to the IEEE 802.11 Standard.

A per-class QoS service model in IEEE 802.11e WLANs

In this paper, we study the provision of per-class QoS for IEEE 802.11e enhanced distributed channel access (EDCA) WLANs. We propose two mechanisms, called BIWF-SP and IDFQ-SP, based on backoff interval (BI) and inter-frame space (IFS), respectively. In our mechanisms, both strict priority and proportional fair service are supported. We describe the operations of the proposed mechanisms in details, and compare their performance with the original EDCA mechanism via simulations. The results show that both BIWF-SP and IDFQ-SP outperform the original EDCA in terms of the support for both strict priority and weighted fair service. Compared to IDFQ-SP, BIWF-SP is easier to be implemented in real systems; compared to BIWF-SP, IDFQ-SP has better aggregate throughput and is more stable. More importantly, both mechanisms conform to the IEEE 802.11e EDCA standard, rendering both good candidates to provide per-class QoS service for IEEE 802.11 WLANs

Proportional fairness for QoS enhancement in IEEE 802.11e WLANs

In this paper, we study the proportional fairness problem in IEEE 802.11e wireless local area networks (WLANs). With 802.11e EDCA, only priority-based service is supported. Such priority-based service, while allowing differentiated service for flows of different priorities, cannot ensure service amount in proportion to their demands. This calls for weighted fair service to be supported by EDCA. In this paper, we propose a mechanism called weighted fair-EDCA (WF-EDCA) to provide proportional fairness for IEEE 802.11 WLANs. With WF-EDCA, weighted fair service among different access categories (ACs) is provided, and strict priority service can also be implemented. We then conduct simulations based on ns-2 to compare the performance of WF-EDCA and EDCA. The results show that WF-EDCA outperforms EDCA in terms of providing proportional fairness and strict priority service for IEEE 802.11 WLANs while retaining comparable total throughput

Interframe-Space (IFS)-Based Distributed Fair Queuing for Proportional Fairness in IEEE 802.11 WLANs

In this paper, we propose an interframe-space (IFS)-based distributed-fair-queuing (IDFQ) mechanism to provide proportional fairness service for IEEE 802.11 wireless local-area networks (WLANs). IDFQ is designed to emulate self-clocked fair queuing in a distributed manner. It eliminates the backoff process as implemented in existing work and introduces a new mechanism to assign the IFS value to each station. IDFQ is immune from the implementation problem suffered by existing IFS-based mechanisms and is adaptive to the collision state in the system. Moreover, it can be used to eliminate the performance-anomaly problem of 802.11 medium-access control. The performance of IDFQ is validated by ns-2 simulations. The simulation results show that IDFQ supports fairness service for flows in proportion to their weights and outperforms existing mechanisms in terms of fairness and stability, rendering IDFQ an excellent candidate to provide weighted fairness in IEEE 802.11 WLANs

WF/sup 2/Q-M : a worst-case fair weighted fair queueing with maximum rate control

Maximum rate control in a shared channel is important to service providers and carriers for various reasons. Previous approaches either use a concatenation of regulator and scheduler, which employs two set of queues and two management systems, or a policer in front of scheduler. The former requires extra management overhead and inaccuracy, and the latter causes bursty traffic as well as inaccuracy. In this paper, we propose a new scheduling algorithm, called WF/sup 2/Q-M (worst-case fair weighted fair queueing with maximum rate control), to simultaneously support maximum rate control and provide minimum service rate guarantee. WF/sup 2/Q-M has similar worst case time complexity with WF/sup 2/Q designed to provide accurate scheduling. WF/sup 2/Q-M employs virtual clock adjustment to distribute the excess bandwidth of saturated sessions to other sessions without recalculating their virtual starting and finishing times. WF/sup 2/Q-M performance is theoretically bounded by a fluid reference mode, and simulations show WF/sup 2/Q-M performs just as claimed.