16,768 research outputs found
Analysis of a Cone-Based Distributed Topology Control Algorithm for Wireless Multi-hop Networks
The topology of a wireless multi-hop network can be controlled by varying the
transmission power at each node. In this paper, we give a detailed analysis of
a cone-based distributed topology control algorithm. This algorithm, introduced
in [16], does not assume that nodes have GPS information available; rather it
depends only on directional information. Roughly speaking, the basic idea of
the algorithm is that a node transmits with the minimum power
required to ensure that in every cone of degree around
, there is some node that can reach with power . We show
that taking is a necessary and sufficient condition to
guarantee that network connectivity is preserved. More precisely, if there is a
path from to when every node communicates at maximum power, then, if
, there is still a path in the smallest symmetric graph
containing all edges such that can communicate with
using power . On the other hand, if ,
connectivity is not necessarily preserved. We also propose a set of
optimizations that further reduce power consumption and prove that they retain
network connectivity. Dynamic reconfiguration in the presence of failures and
mobility is also discussed. Simulation results are presented to demonstrate the
effectiveness of the algorithm and the optimizations.Comment: 10 page
Distributed Decision Through Self-Synchronizing Sensor Networks in the Presence of Propagation Delays and Asymmetric Channels
In this paper we propose and analyze a distributed algorithm for achieving
globally optimal decisions, either estimation or detection, through a
self-synchronization mechanism among linearly coupled integrators initialized
with local measurements. We model the interaction among the nodes as a directed
graph with weights (possibly) dependent on the radio channels and we pose
special attention to the effect of the propagation delay occurring in the
exchange of data among sensors, as a function of the network geometry. We
derive necessary and sufficient conditions for the proposed system to reach a
consensus on globally optimal decision statistics. One of the major results
proved in this work is that a consensus is reached with exponential convergence
speed for any bounded delay condition if and only if the directed graph is
quasi-strongly connected. We provide a closed form expression for the global
consensus, showing that the effect of delays is, in general, the introduction
of a bias in the final decision. Finally, we exploit our closed form expression
to devise a double-step consensus mechanism able to provide an unbiased
estimate with minimum extra complexity, without the need to know or estimate
the channel parameters.Comment: To be published on IEEE Transactions on Signal Processin
Complexity of increasing the secure connectivity in wireless ad hoc networks
We consider the problem of maximizing the secure connectivity in wireless ad hoc networks, and analyze complexity of the post-deployment key establishment process constrained by physical layer properties such as connectivity, energy consumption and interference. Two approaches, based on graph augmentation problems with nonlinear edge costs, are formulated. The first one is based on establishing a secret key using only the links that are already secured by shared keys. This problem is in NP-hard and does not accept polynomial time approximation scheme PTAS since minimum cutsets to be augmented do not admit constant costs. The second one extends the first problem by increasing the power level between a pair of nodes that has a secret key to enable them physically connect. This problem can be formulated as the optimal key establishment problem with interference constraints with bi-objectives: (i) maximizing the concurrent key establishment flow, (ii) minimizing the cost. We prove that both problems are NP-hard and MAX-SNP with a reduction to MAX3SAT problem
- …