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Abstract-Vehicular ad hoc networks (VANETs) are going to be an important communication infrastructure in our life. Because of high mobility and frequent link disconnection, it becomes quite challenging to establish a robust multi-hop path that helps packet delivery from the source to the destination. This paper presents a multi-hop routing protocol, called MURU, that is able to find robust paths in urban VANETs to achieve high end-to-end packet delivery ratio with low overhead. MURU tries to minimize the probability of path breakage by exploiting mobility information of each vehicle in VANETs. A new metric called expected disconnection degree (EDD) is used to select the most robust path from the source to the destination. MURU is fully distributed and does not incur much overhead, which makes MURU highly scalable for VANETs. The design is sufficiently justified through theoretical analysis and the protocol is evaluated with extensive simulations. Simulation results demonstrate that MURU significantly outperforms existing ad hoc routing protocols in terms of packet delivery ratio, packet delay and control overhead.

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Abstract-The development of efficient quality of service (QoS) routing algorithms in a high-speed network environment is a very important and at the same time very difficult task due to the need to provide divergent services with multiple QoS requirements. Recently heuristic algorithms based on Lagrange relaxation techniques have been proposed to resolve the contradiction between the time complexity and the quality of solution. In this paper, we investigate the performance of two heuristic algorithms, LR DCLC and NR DCLC, for the delay-constrained least-cost (DCLC) routing problem. Algorithm LR DCLC is based on linear relaxation, while algorithm NR DCLC, which is proposed in this paper, is based on nonlinear relaxation. A large number of simulations demonstrate that even though both algorithms have very good performance, NR DCLC can obtain much better solutions than LR DCLC by running Dijkstra's algorithm on average a few more times, especially in the case when the optimal solutions are hard to find.

Abstract-Vehicular ad hoc networks (VANETs) are going to be an important communication infrastructure in our life. Because of high mobility and frequent link disconnection, it becomes quite challenging to establish a robust multi-hop path that helps packet delivery from the source to the destination. This paper presents a multi-hop routing protocol, called MURU, that is able to find robust paths in urban VANETs to achieve high end-to-end packet delivery ratio with low overhead. MURU tries to minimize the probability of path breakage by exploiting mobility information of each vehicle in VANETs. A new metric called expected disconnection degree (EDD) is used to select the most robust path from the source to the destination. MURU is fully distributed and does not incur much overhead, which makes MURU highly scalable for VANETs. The design is sufficiently justified through theoretical analysis and the protocol is evaluated with extensive simulations. Simulation results demonstrate that MURU significantly outperforms existing ad hoc routing protocols in terms of packet delivery ratio, packet delay and control overhead.

The next-generation (4G) wireless communication systems focus on the seamless integration of various existing wireless communication networks, such as integrating the thirdgeneration (3G) cellular networks and wireless local area network (WLAN). Resource management (RM) is one of the essential techniques to improve both overall resource utilization and quality-of-service (QoS) provisioning. In this paper, we proposed a novel joint resource management scheme with QoS provisioning. A joint call admission policy is derived to support heterogeneous network architecture, service types, user mobility characteristics, and QoS levels. To relieve traffic congestion, an optimal channel searching and replacement algorithm (oCSR) and passive handoff techniques are further developed to balance total system traffic between WLAN and 3G cellular network as well as to reduce average system QoS cost, such as weighted blocking probability. Theoretical analysis and simulation results show that our scheme outperforms both traditional disjoint RM and joint RM without optimization.

Wireless local area networks ( W L A N ) are expected to be a major growth factor for communication networks in the up-coming years. They are expected to provide a transparent connection f o r mobile hosts to communicate with other mobile hosts, and wired hosts o n the wired L A N and broadband networks. Recently there have been two W L A N projects u ndergo standardization process: the I E E E 802.11 and the E T S I H I P E R L A N . Most of the existing study of the two M A C protocols focused o n simulation results, and none of t h e m has formally analyzed the hiddenterminal effect, which is both crucial and unavoidable in wireless/mobile environment. I n the first part of this paper, we formally analyze the hidden-terminal effect o n H I P E R L A N . Through mathematical analysis, we formulate network throughput under hiddenterminal influence in terms of the original (clearchannel) throughput, hidden-terminal probability, and other protocol parameters. W e show that when hidden probability is greater than zero, the achievable throughput is reduced b y more than the percentage of hidden probability. I n the second part of the paper, we evaluate and compare the two W L A N M A C protocols by simulation o n the effect of hidden terminals o n (1) network throughput, (2) real-time voice delay, and (3) number of voice and data stations supported while guaranteeing delay f o r voice. W e also evaluate how well the two M A C protocols support real-time trafic while considering the effects of frame size and other network parameters, and measure (1) the distribution of voice *and ENH-TR-95. delay and (2) number of voice and data stations supported while guaranteeing their quality of service. W e found that, comparing with IEEE 802.11, H I P E R L A N provides real-time packet voice trafic with shorter delay, and at the same time provides the non-real-time packet data with higher bandwidth.

Abstract. In this paper we have proposed a secure routing protocol based on AODV for multihop ad hoc networks. Our protocol is unique in the sense that it is capable of finding a secure end-to-end route free of any malicious entity, thus resisting an intemal attack within the network either in the form of compromised or disloyal nodes. We propose to find a secure and efficient route to a destination based on collaborative effort of all the nodes.