Multihop data delivery through vehicular ad hoc networks is complicated by the fact that vehicular networks are highly mobile and frequently disconnected. To address this issue, we adopt the idea of carry and forward, where a moving vehicle carries a packet until a new vehicle moves into its vicinity and forwards the packet. Being different from existing carry and forward solutions, we make use of predictable vehicle mobility, which is limited by traffic pattern and road layout. Based on the existing traffic pattern, a vehicle can find the next road to forward the packet to reduce the delay. We propose several vehicle-assisted data delivery (VADD) protocols to forward the packet to the best road with the lowest data-delivery delay. Experimental results show that the proposed VADD protocols outperform existing solutions in terms of packet-delivery ratio, data packet delay, and protocol overhead. Among the proposed VADD protocols, the Hybrid Probe (H-VADD) protocol has a much better performance.

In many applications, wireless ad-hoc networks are formed by devices belonging to independent users. Therefore, a challenging problem is how to provide incentives to stimulate cooperation. In this paper, we study ad-hoc games—the routing and packet forwarding games in wireless ad-hoc networks. Unlike previous work which focuses either on routing or on forwarding, this paper investigates both routing and forwarding. We first uncover an impossibility result—there does not exist a protocol such that following the protocol to always forward others’ traffic is a dominant action. Then we define a novel solution concept called cooperation-optimal protocols. We present Corsac, a cooperation-optimal protocol consisting of a routing protocol and a forwarding protocol. The routing protocol of Corsac integrates VCG with a novel cryptographic technique to address the challenge in wireless ad-hoc networks

Protecting the network layer from malicious attacks is an important yet challenging security issue in mobile ad hoc networks. In this paper we describe SCAN, a unified networklayer security solution for such networks that protects both routing and data forwarding operations through the same reactive approach. SCAN does not apply any cryptographic primitives on the routing messages. Instead, it protects the network by detecting and reacting to the malicious nodes. In SCAN, local neighboring nodes collaboratively monitor each other and sustain each other, while no single node is superior to the others. SCAN also adopts a novel credit strategy to decrease its overhead as time evolves. In essence, SCAN exploits localized collaboration and information cross-validation to protect the network in a self-organized manner. Through both analysis and simulation results we demonstrate the effectiveness of SCAN even in a highly mobile and hostile environment.

The advance in wireless technologies makes now viable to start to develop ad hoc networks. However, without a mechanism that prevents misbehaviors, these networks could result easily unreliable. We develop a model, based on game theory, capable of formally explaining characteristics of ad hoc networks (as the nodes' selfishness or the network mobility). It also allows to formally study and analyze strategies for cooperation. As example, we describe a simple strategy that enforces packet forwarding among nodes.

Ad hoc networks rely on the cooperation of the nodes participating in the network to forward packets for each other. A node may decide not to cooperate to save its resources while still using the network to relay its tra#c. If too many nodes exhibit this behavior, network performance degrades and cooperating nodes may find themselves unfairly loaded. Most previous e#orts to counter this behavior ([4],[5],[6],[21]) have relied on further cooperation between nodes to exchange reputation information about other nodes. If a node observes another node not participating correctly, it reports this observation to other nodes who then take action to avoid being a#ected and potentially punish the bad node by refusing to forward its tra#c. Unfortunately, such second-hand reputation information is subject to false accusations and requires maintaining trust relationships with other nodes. The objective of OCEAN is to avoid this trust-management machinery and see how far we can get simply by using direct first-hand observations of other nodes' behavior. We find that, in many scenarios, OCEAN can do as well as, or even better than, schemes requiring second-hand reputation exchanges. This encouraging result could possibly help obviate solutions requiring trust-management for some contexts.

Abstract- Multi-hop wireless networks are vul-nerable to free-riders because they require nodes to forward packets for each other. Deployed routing protocolsignore this issue while proposed solutions incorporate complicated mechanisms with the intent of making free-riding impossible. We present Catch, a protocol that falls between these extremes. It achieves nearly the low mech-anism requirements of the former while imposing nearly as effective barriers to free-riding as the latter. Catch ismade possible by novel techniques based on anonymous messages. These techniques enable cooperative nodesto detect nearby free-riders and disconnect them from the rest of the network. Catch has low overhead andis broadly applicable across routing protocols and traffic workloads. We evaluate it on an 802.11 wireless testbedas well as through simulation.

Restricting network access of routing and packet forwarding to well-behaving nodes, and denying access from misbehaving nodes are critical for the proper functioning of a mobile ad-hoc network where cooperation among all networking nodes is usually assumed. However, the lack of a network infrastructure, the dynamics of the network topology and node membership, and the potential attacks from inside the network by malicious and/or non-cooperative selfish nodes make the conventional network access control mechanisms not applicable. We present URSA, a ubiquitous and robust access control solution for mobile ad-hoc networks. URSA implements ticket certification services through multiple-node consensus and fully localized instantiation, and uses tickets to identify and grant network access to well-behaving nodes. In URSA, no single node monopolizes the access decision or is completely trusted, and multiple nodes jointly monitor a local node and certify/revoke its ticket. Furthermore, URSA ticket certification services are fully localized into each node's neighborhood to ensure service ubiquity and resilience. Through analysis, simulations and experiments, we show that our design effectively enforces access control in the highly dynamic, mobile ad-hoc network.

Most proposed routing protocols for mobile ad hoc networks are vulnerable to modification, impersonation and fabrication attacks. The proposed secure rout8 Mobile Computing and Communications Review, Volume 6, Number 4 ing protocol, Authenticated Routing for Ad Hoc Networks, prevents such attacks through message authentication, integrity and non-repudiation. Simulation results show that ARAN maintains good network performance while offering significant security advantages over existing routing protocols.

In self-organizing ad hoc networks, all the networking functions rely on the contribution of the participants. As a basic example, nodes have to forward packets for each other in order to enable multihop communication. In recent years, incentive mechanisms have been proposed to give nodes incentive to cooperate, especially in packet forwarding. However, the need for these mechanisms was not formally justified. In this paper, we address the problem of whether cooperation can exist without incentive mechanisms. We propose a model based on game theory and graph theory to investigate equilibrium conditions of packet forwarding strategies. We prove theorems about the equilibrium conditions for both cooperative and noncooperative strategies. We perform simulations to estimate the probability that the conditions for a cooperative equilibrium hold in randomly generated network scenarios. As the problem is involved, we deliberately restrict ourselves to a static configuration. We conclude that in static ad hoc networks— where the relationships between the nodes are likely to be stable—cooperation needs to be encouraged.

Abstract not found