Hussam M. Soliman Ramadan

Design and evaluation of a fast MAC layer handoff management scheme for WiFi-based multichannel Vehicular Mesh Networks

Abstract Vehicular Mesh Networks (VMNs) are important components of the wireless metropolitan networks. Compared with traditional wireless networks, they are more efficient in terms of deployment, configuration, and maintenance. However, connecting all mesh routers through wireless connection in VMNs results in the network backbones remarkably lower bandwidth. Multichannel technology, where non-interfering channels are used to enable mesh routers to send and receive packets simultaneously, can be adopted to improve the throughput of VMNs. Due to the limited radio range of mesh routers, mobile clients have to switch among different mesh routers to maintain wireless connections. Therefore, providing smooth roaming in multichannel VMNs has become an important topic in VMN research. In this paper, a novel MAC layer handoff scheme is proposed as a means of minimizing handoff latency for WiFi-based multichannel VMNs to provide smooth communication for real-time applications. By designing a dynamic grouping algorithm for channel selection and allowing mesh routers to switch their channels for probe response messages, our scheme can shorten the waiting time for the detection of available access routers, decrease the loss ratio of data packets during the handoff, and consequently achieve smooth handoff in the MAC layer.

Design of a lightweight authentication scheme for IEEE 802.11p vehicular networks

With the growing popularity of vehicle-based mobile devices, vehicular networks are becoming an essential part of wireless heterogeneous networks. Therefore, vehicular networks have been widely studied in recent years. Because of limited transmission range of wireless antennas, mobile vehicles should also switch their access points to maintain the connections as conventional mobile nodes. Considering the inherent characteristics of vehicular networks such as dynamic topology and high speed, the question of how to implement handoff protocol under real-time scenarios is very important. IEEE 802.11p protocol is designed for vehicular networks for the long distance transmission. To reduce handoff latency for 802.11p protocol, the authentication phase is waived during the handoff. However, security is also very important for wireless communications, and authentication can forbid access from malicious nodes and prevent wireless communications from potential attacks. Thus, in this paper, a lightweight authentication scheme is introduced to balance the security requirements and the handoff performance for 802.11p vehicular networks. In our scheme, the access points are divided into different trust groups, and the authentication process is completed in a group-based method. Once a vehicle is authenticated by an access point group, during the handoff within the same group, few extra authentication operations are needed. As a result, there is no extra overhead introduced to the authentication servers. Simulation results demonstrate that our authentication scheme only introduces small handoff latency and it is ideal for vehicular networks.

Performance evaluation of an efficient fault tolerant service discovery protocol for vehicular networks

Recently, vehicular networks and inter-vehicle communication have received attention from the research community and the automotive industry. In this context, many services are deployed in vehicular networks that are beneficial to drivers and passengers. Service discovery in vehicular networks is vital to make such services useful. However, due to the lack of communication reliability in vehicular ad hoc networks, it is necessary to implement fault-tolerant techniques during the discovery of service providers in vehicular networks. Very few service discovery protocols for vehicular networks have considered fault tolerant techniques, which are very important for the efficiency of service discovery. Fault tolerant techniques improve service request satisfaction and reduce dropped connections due to faulty components between the service provider and the service requester. In this paper, we propose a fault tolerant location based service discovery protocol for vehicular networks which can work well under service provider failures, communication link failures and roadside router failures. Our protocol permits the discovery of location based services where the requester specifies the region of interest within the request. Our protocol uses an infrastructure support consisting of clusters of roadside routers formed in specific regions in the vehicular network. In addition, service discovery messages are integrated into the network layer and use channel diversity in order to improve service discovery efficiency. We describe our fault tolerant location based vehicular service discovery protocol (FTLocVSDP) and discuss its proof of correctness and performance evaluation. We prove that the success rate is improved in the roadside router failure and in the communication link failure scenarios by 50% and 30%, respectively, compared to the location based service discovery protocol for vehicular networks (LocVSDP) which does not consider fault tolerant techniques.

Measuring Communication Delay for Dynamic Balancing Strategies of Distributed Virtual Simulations

As an inherent characteristic of any distributed system, the execution and performance of distributed virtual simulations totally rely on underlay communication infrastructure and resources. The performance of such simulations is directly restricted by the communication latencies between interdependent simulation components. The high level architecture (HLA) is a framework designed with the objective of organizing these simulations through management services. However, the framework is unaware of the communication delays caused by the network distances between communicating simulation parts. These delays can result from nonplanned initial deployment or dynamic simulation changes, requiring constant load balancing. Due to the importance of balancing distributed simulations, many approaches have been designed. In order to provide a balancing system aware of the dynamic communication changes, a delay-based redistribution scheme has been designed. The scheme successfully arranges the load, but it lacks precision due to communication delay oscillations. Therefore, extensions are proposed to modify the balancing algorithm in order to avoid unnecessary, mistaken load rearrangements. In the experimental results, the delay-based scheme has been able to reduce the simulation execution time when compared with the distributed balancing scheme, and the proposed extension has been capable of increasing the precision of the balancing.

TEASE: A novel Tunnel-based sEcure Authentication SchemE to support smooth handoff in IEEE 802.11 wireless networks

With the growing popularity of WiFi-based devices, WiFi-based wireless networks have received a great deal of interest in the wireless networks community. However, due to the limited transmission range of WiFi-based networks, mobile users have to switch their associated access points constantly to maintain continuing communications during their movement. The process of switching access points is called handoff. Handoff management is a key service in mobile networks, because providing seamless roaming in wireless networks is mandatory for supporting real-time applications in a mobile environment, such as VoIP, online games, and eConference. Security is another important issue in network communications, and to prevent possible attacks, authentication is required during the handoff process to guarantee the reliability of mobile clients and access points. In this paper, we propose a novel authentication scheme to achieve a smooth handoff in WiFi-based networks, which we refer to as TEASE. A tunnel is introduced to forward data packets between the new access point and the original reliable access point. The processing of a complete secure authentication and the transmitting of data between mobile terminals and their correspondence nodes can go on simultaneously. The security of handoff is achieved without increasing overhead to authentication servers, and handoff latency can be minimized to support seamless roaming. Simulation results show that our proposed scheme reduces significantly the communication interruption time and generates low packet loss ratio, and our method is suitable to be used for secure handoff in real-time applications.

Distributed re‐arrangement scheme for balancing computational load and minimizing communication delays in HLA‐based simulations

Because of the availability of shared resources, substantial efforts have been applied to the development of large‐scale distributed simulations, and performance has become an essential aspect that can be impaired by heterogeneity and availability of resources, dynamic, unpredictable load imbalances, and communication delays. In order to manage and keep such distributed simulations consistent, the high level architecture (HLA) standard has been designed; however, it does not provide any solution that directly solves simulation performance issues. Many balancing approaches have been proposed in order to offer a suboptimal balancing solution, but they are limited to certain simulation aspects, are specific to determined applications, or are unaware of the HLA‐based simulation characteristics. In light of considering both computational and communication aspects for HLA‐based simulations, a centralized hierarchical balancing scheme was proposed. This scheme presents several drawbacks that make it susceptible to bottlenecks, overheads, global synchronization, and single point of failure. Therefore, a scheme based on a distributed algorithm to re‐arrange the computational and communication load is proposed. Experiments have been performed to evaluate the effectiveness of the distributed scheme when compared with the scheme based on a centralized redistribution algorithm. The results showed that the distributed balancing technique could provide similar performance gain or even improve it for some specific cases. Copyright