365 research outputs found
Energy-Efficient Broadcasting in All-Wireless Networks
In all-wireless networks, minimizing energy consumption is crucial as in most cases the nodes are battery-operated. We focus on the problem of power-optimal broadcast, for which it is well known that the broadcast nature of radio transmissions can be exploited to optimize energy consumption. This problem appears to be difficult to solve [30]. We provide a formal proof of NP-completeness for the general case and give an NP-completeness result for the geometric case; in the former, the network topology is represented by a generic graph with arbitrary weights, whereas in the latter a Euclidean distance is considered. For the general case, we show that it cannot be approximated better than O(log N), where N is the total number of nodes. We then describe an approximation algorithm that achieves the O(log N) approximation ratio. We also describe a new heuristic, Embedded Wireless Multicast Advantage. We show that it compares well with other proposals and we explain how it can be distribute
Networking - A Statistical Physics Perspective
Efficient networking has a substantial economic and societal impact in a
broad range of areas including transportation systems, wired and wireless
communications and a range of Internet applications. As transportation and
communication networks become increasingly more complex, the ever increasing
demand for congestion control, higher traffic capacity, quality of service,
robustness and reduced energy consumption require new tools and methods to meet
these conflicting requirements. The new methodology should serve for gaining
better understanding of the properties of networking systems at the macroscopic
level, as well as for the development of new principled optimization and
management algorithms at the microscopic level. Methods of statistical physics
seem best placed to provide new approaches as they have been developed
specifically to deal with non-linear large scale systems. This paper aims at
presenting an overview of tools and methods that have been developed within the
statistical physics community and that can be readily applied to address the
emerging problems in networking. These include diffusion processes, methods
from disordered systems and polymer physics, probabilistic inference, which
have direct relevance to network routing, file and frequency distribution, the
exploration of network structures and vulnerability, and various other
practical networking applications.Comment: (Review article) 71 pages, 14 figure
Minimum-energy broadcast in random-grid ad-hoc networks: approximation and distributed algorithms
The Min Energy broadcast problem consists in assigning transmission ranges to
the nodes of an ad-hoc network in order to guarantee a directed spanning tree
from a given source node and, at the same time, to minimize the energy
consumption (i.e. the energy cost) yielded by the range assignment. Min energy
broadcast is known to be NP-hard.
We consider random-grid networks where nodes are chosen independently at
random from the points of a square grid in the
plane. The probability of the existence of a node at a given point of the grid
does depend on that point, that is, the probability distribution can be
non-uniform.
By using information-theoretic arguments, we prove a lower bound
on the energy cost of any feasible solution for
this problem. Then, we provide an efficient solution of energy cost not larger
than .
Finally, we present a fully-distributed protocol that constructs a broadcast
range assignment of energy cost not larger than ,thus still yielding
constant approximation. The energy load is well balanced and, at the same time,
the work complexity (i.e. the energy due to all message transmissions of the
protocol) is asymptotically optimal. The completion time of the protocol is
only an factor slower than the optimum. The approximation quality
of our distributed solution is also experimentally evaluated.
All bounds hold with probability at least .Comment: 13 pages, 3 figures, 1 tabl
Minimum Energy Broadcast and Disk Cover in Grid Wireless Networks
Abstract. The Minimum Energy Broadcast problem consists in finding the minimum-energy range assignment for a given set S of n stations of an ad hoc wireless network that allows a source station to perform broadcast operations over S. We prove a nearly tight asymptotical bound on the optimal cost for the Minimum Energy Broadcast problem on square grids. We emphasize that finding tight bounds for this problem restriction is far to be easy: it involves the Gauss’s Circle problem and the Apollonian Circle Packing. We also derive near-tight bounds for the Bounded-Hop version of this problem. Our results imply that the best-known heuristic, the MST-based one, for the Minimum Energy Broadcast problem is far to achieve optimal solutions (even) on very regular, well-spread instances: its worst-case approximation ratio is about pi and it yields Ω( n) hops. As a by product, we get nearly tight bounds for the Minimum Disk Cover problem and for its restriction in which the allowed disks must have non-constant radius. Finally, we emphasize that our upper bounds are obtained via polynomial time constructions.
Contributions to Distributed Spatial Compression in Wireless Sensor Networks
Projecte final de carrera fet en col.laboració amb University of Southern CaliforniaPremi Càtedra Red.es en l’Àrea de Sistemes de la Informació al millor Projecte de Fi de Carrera d'Enginyeria de Telecomunicació. Atorgat per Càtedra Red.es. (Curs 2010-2011)This thesis presents several contributions in the field of distributed spatial compression
inWireless Sensor Networks. First, since in most of the spatial compression
schemes some nodes (raw nodes) need to broadcast their raw data to allow other
nodes (aggregating nodes) to perform compression, we design several distributed
heuristics which, via local communications, split the nodes into raw/aggregating
subsets and optimize the amount of energy consumed in the network. We also extend
previous work in the use of graph-based lifting transforms for data compression
in distributed data gathering applications, to networks with more than one sink,
and scenarios where all data has to be available at every node. Additionally, under
the scope of these contributions, we design a new energy-efficient multicast routing
algorithm, which is based on the minimum Steiner tree and exploits the broadcast
property of wireless communications. We prove via computer-based simulations
that our methods reduce the energy consumption in the network in comparison
with existing approaches.Award-winnin
Minimum-energy broadcast in all-wireless networks: NP-Completeness and distribution issues
In all-wireless networks a crucial problem is to minimize energy consumption, as in most cases the nodes are battery-operated. We focus on the problem of power-optimal broadcast, for which it is well known that the broadcast nature of the radio transmission can be exploited to optimize energy consumption. Several authors have conjectured that the problem of power-optimal broadcast is NP-complete. We provide here a formal proof, both for the general case and for the geometric one; in the former case, the network topology is represented by a generic graph with arbitrary weights, whereas in the latter a Euclidean distance is considered. We then describe a new heuristic, Embedding Wireless Multicast Advantage. We show that it compares well with other proposals and we explain how it can be distributed
- …