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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

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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.

Though an increasing number of wireless hotspots and mesh networks are being deployed, the problem of location privacy has been ignored. When a user’s location privacy is compromised, an attacker can determine where the user is, and use this information, for example, to stalk or blackmail the user. In existing systems, a user’s location can be easily inferred from the signal strengths of packets transmitted from her fixed address. Even if an attacker cannot decode packet contents and addresses, he can correlate different transmissions using a model of the user’s movement. In this paper, we argue that location privacy must be a first-class citizen in the design of a wireless communications system. We build a transaction-based wireless communication system in which transactions (a single request-response exchange between two nodes) are unlinkable; that is, they cannot be correlated. We find that it is even possible to support real-time session-based services such as Voice-over-IP on top of transaction primitives, though with weaker privacy properties. We also identify a number of challenges in providing location privacy in the areas of routing, incentives for multi-hop forwarding, and user- and application-driven tuning of the privacy-performance tradeoff.

Skyline queries are well suited when retrieving data according to multiple criteria. While most previous work has assumed a centralized setting this paper considers skyline querying in a mobile and distributed setting, where each mobile device is capable of holding only a portion of the whole dataset; where devices communicate through mobile ad hoc networks; and where a query issued by a mobile user is interested only in the user’s local area, although a query generally involves data stored on many mobile devices due to the storage limitations. We present techniques that aim to reduce the costs of communication among mobile devices and reduce the execution time on each single mobile device. For the former, skyline query requests are forwarded among mobile devices in a deliberate way, such that the amount of data to be transferred is reduced. For the latter, specific optimization measures are proposed for resource-constrained mobile devices. We conduct extensive experiments to show that our proposal performs efficiently in real mobile devices and simulated wireless ad hoc networks. 1.

In recent years, wireless Internet service providers (WISPs) have established Wi-Fi hotspots in increasing numbers at public venues, providing local coverage to traveling users and empowering them with the ability to access email, Web, and other Internet applications on the move. In this paper, we observe that while the mobile computing landscape has changed both in terms of number and type of hotspot venues, there are several technological and deployment challenges remaining before hotspots can become an ubiquitous infrastructure. These challenges include authentication, security, coverage, management, location services, billing, and interoperability. We discuss existing research, the work of standards bodies, and the experience of commercial hotspot providers in these areas, and then describe compelling open research questions that remain.

We study the capacity of a wireless ad hoc network with infrastructure, where well-connected base stations are placed in an ad hoc network to relay data traffic for wireless nodes. This network architecture presents a tradeoff between a cellular network and an ad hoc network in that data may be forwarded in a multi-hop fashion or through the infrastructure. It has been shown that the capacity of ad hoc network does not scale well with the number of nodes in the system [1]. In this work, we investigate the potential benefit of infrastructure network to improve ad hoc network capacity. Analytical expressions are obtained for the capacity of an ad hoc networks with infrastructure. For an ad hoc network of £ nodes with ¤ base stations, the results show that, if ¤ grows asymptotically slower than ¥ £ , the benefit of infrastructure network is insignificant. However, if ¤ grows faster than ¥ £ , the capacity increases linearly with the number of base stations, providing an effective improvement over ad hoc networks. Therefore, in order to achieve non-negligible capacity gain, the investment in the wired infrastructure should be sufficiently high.

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