200 research outputs found
Coverage and Connectivity in Three-Dimensional Networks
Most wireless terrestrial networks are designed based on the assumption that
the nodes are deployed on a two-dimensional (2D) plane. However, this 2D
assumption is not valid in underwater, atmospheric, or space communications. In
fact, recent interest in underwater acoustic ad hoc and sensor networks hints
at the need to understand how to design networks in 3D. Unfortunately, the
design of 3D networks is surprisingly more difficult than the design of 2D
networks. For example, proofs of Kelvin's conjecture and Kepler's conjecture
required centuries of research to achieve breakthroughs, whereas their 2D
counterparts are trivial to solve. In this paper, we consider the coverage and
connectivity issues of 3D networks, where the goal is to find a node placement
strategy with 100% sensing coverage of a 3D space, while minimizing the number
of nodes required for surveillance. Our results indicate that the use of the
Voronoi tessellation of 3D space to create truncated octahedral cells results
in the best strategy. In this truncated octahedron placement strategy, the
transmission range must be at least 1.7889 times the sensing range in order to
maintain connectivity among nodes. If the transmission range is between 1.4142
and 1.7889 times the sensing range, then a hexagonal prism placement strategy
or a rhombic dodecahedron placement strategy should be used. Although the
required number of nodes in the hexagonal prism and the rhombic dodecahedron
placement strategies is the same, this number is 43.25% higher than the number
of nodes required by the truncated octahedron placement strategy. We verify by
simulation that our placement strategies indeed guarantee ubiquitous coverage.
We believe that our approach and our results presented in this paper could be
used for extending the processes of 2D network design to 3D networks.Comment: To appear in ACM Mobicom 200
Secure Data Transmission in Mobile Ad Hoc Networks
The vision of nomadic computing with its ubiquitous access has stimulated much interest in the Mobile Ad Hoc Networking (MANET) technology. However, its proliferation strongly depends on the availability of security provisions, among other factors. In the open, collaborative MANET environment practically any node can maliciously or selfishly disrupt and deny communication of other nodes. In this paper, we present and evaluate the Secure Message Transmission (SMT) protocol, which safeguards the data transmission against arbitrary malicious behavior of other nodes. SMT is a lightweight, yet very effective, protocol that can operate solely in an end-to-end manner. It exploits the redundancy of multipath routing and adapts its operation to remain efficient and effective even in highly adverse environments. SMT is capable of delivering up to 250% more data messages than a protocol that does not secure the data transmission. Moreover, SMT outperforms an alternative single-path protocol, a secure data forwarding protocol we term Secure Single Path (SSP) protocol. SMT imposes up to 68% less routing overhead than SSP, delivers up to 22% more data packets and achieves end-to-end delays that are up to 94% lower than those of SSP. Thus, SMT is better suited to support QoS for real-time communications in the ad hoc networking environment. The security of data transmission is achieved without restrictive assumptions on the network nodes' trust and network membership, without the use of intrusion detection schemes, and at the expense of moderate multi-path transmission overhead only
A Decision-Theoretic Approach to Resource Allocation in Wireless Multimedia Networks
The allocation of scarce spectral resources to support as many user
applications as possible while maintaining reasonable quality of service is a
fundamental problem in wireless communication. We argue that the problem is
best formulated in terms of decision theory. We propose a scheme that takes
decision-theoretic concerns (like preferences) into account and discuss the
difficulties and subtleties involved in applying standard techniques from the
theory of Markov Decision Processes (MDPs) in constructing an algorithm that is
decision-theoretically optimal. As an example of the proposed framework, we
construct such an algorithm under some simplifying assumptions. Additionally,
we present analysis and simulation results that show that our algorithm meets
its design goals. Finally, we investigate how far from optimal one well-known
heuristic is. The main contribution of our results is in providing insight and
guidance for the design of near-optimal admission-control policies.Comment: To appear, Dial M for Mobility, 200
A Practical, Secure, and Verifiable Cloud Computing for Mobile Systems
Cloud computing systems, in which clients rent and share computing resources
of third party platforms, have gained widespread use in recent years.
Furthermore, cloud computing for mobile systems (i.e., systems in which the
clients are mobile devices) have too been receiving considerable attention in
technical literature. We propose a new method of delegating computations of
resource-constrained mobile clients, in which multiple servers interact to
construct an encrypted program known as garbled circuit. Next, using garbled
inputs from a mobile client, another server executes this garbled circuit and
returns the resulting garbled outputs. Our system assures privacy of the mobile
client's data, even if the executing server chooses to collude with all but one
of the other servers. We adapt the garbled circuit design of Beaver et al. and
the secure multiparty computation protocol of Goldreich et al. for the purpose
of building a secure cloud computing for mobile systems. Our method
incorporates the novel use of the cryptographically secure pseudo random number
generator of Blum et al. that enables the mobile client to efficiently retrieve
the result of the computation, as well as to verify that the evaluator actually
performed the computation. We analyze the server-side and client-side
complexity of our system. Using real-world data, we evaluate our system for a
privacy preserving search application that locates the nearest bank/ATM from
the mobile client. We also measure the time taken to construct and evaluate the
garbled circuit for varying number of servers, demonstrating the feasibility of
our secure and verifiable cloud computing for mobile systems
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