47 research outputs found
Throughput Scaling Laws for Wireless Networks with Fading Channels
A network of n communication links, operating over a shared wireless channel,
is considered. Fading is assumed to be the dominant factor affecting the
strength of the channels between transmitter and receiver terminals. It is
assumed that each link can be active and transmit with a constant power P or
remain silent. The objective is to maximize the throughput over the selection
of active links. By deriving an upper bound and a lower bound, it is shown that
in the case of Rayleigh fading (i) the maximum throughput scales like
(ii) the maximum throughput is achievable in a distributed fashion. The upper
bound is obtained using probabilistic methods, where the key point is to upper
bound the throughput of any random set of active links by a chi-squared random
variable. To obtain the lower bound, a decentralized link activation strategy
is proposed and analyzed.Comment: Submitted to IEEE Transactions on Information Theory (Revised
E2XLRADR (Energy Efficient Cross Layer Routing Algorithm with Dynamic Retransmission for Wireless Sensor Networks)
The main focus of this article is to achieve prolonged network lifetime with
overall energy efficiency in wireless sensor networks through controlled
utilization of limited energy. Major percentage of energy in wireless sensor
network is consumed during routing from source to destination, retransmission
of data on packet loss. For improvement, cross layered algorithm is proposed
for routing and retransmission scheme. Simulation and results shows that this
approach can save the overall energy consumptio
Research on Wireless Multi-hop Networks: Current State and Challenges
Wireless multi-hop networks, in various forms and under various names, are
being increasingly used in military and civilian applications. Studying
connectivity and capacity of these networks is an important problem. The
scaling behavior of connectivity and capacity when the network becomes
sufficiently large is of particular interest. In this position paper, we
briefly overview recent development and discuss research challenges and
opportunities in the area, with a focus on the network connectivity.Comment: invited position paper to International Conference on Computing,
Networking and Communications, Hawaii, USA, 201
Impact of Correlated Mobility on Delay-Throughput Performance in Mobile Ad-Hoc Networks
AbstractâWe extend the analysis of the scaling laws of wireless ad hoc networks to the case of correlated nodes movements, which are commonly found in real mobility processes. We consider a simple version of the Reference Point Group Mobility model, in which nodes belonging to the same group are constrained to lie in a disc area, whose center moves uniformly across the network according to the i.i.d. model. We assume fast mobility conditions, and take as primary goal the maximization of pernode throughput. We discover that correlated node movements have huge impact on asymptotic throughput and delay, and can sometimes lead to better performance than the one achievable under independent nodes movements. I. INTRODUCTION AND RELATED WORK In the last few years the store-carry-forward communication paradigm, which allows nodes to physically carry buffered dat
Random Access Transport Capacity
We develop a new metric for quantifying end-to-end throughput in multihop
wireless networks, which we term random access transport capacity, since the
interference model presumes uncoordinated transmissions. The metric quantifies
the average maximum rate of successful end-to-end transmissions, multiplied by
the communication distance, and normalized by the network area. We show that a
simple upper bound on this quantity is computable in closed-form in terms of
key network parameters when the number of retransmissions is not restricted and
the hops are assumed to be equally spaced on a line between the source and
destination. We also derive the optimum number of hops and optimal per hop
success probability and show that our result follows the well-known square root
scaling law while providing exact expressions for the preconstants as well.
Numerical results demonstrate that the upper bound is accurate for the purpose
of determining the optimal hop count and success (or outage) probability.Comment: Submitted to IEEE Trans. on Wireless Communications, Sept. 200
Rate-Constrained Wireless Networks with Fading Channels: Interference-Limited and Noise-Limited Regimes
A network of wireless communication links is considered in a Rayleigh
fading environment. It is assumed that each link can be active and transmit
with a constant power or remain silent. The objective is to maximize the
number of active links such that each active link can transmit with a constant
rate . An upper bound is derived that shows the number of active links
scales at most like . To obtain a lower bound, a
decentralized link activation strategy is described and analyzed. It is shown
that for small values of , the number of supported links by this
strategy meets the upper bound; however, as grows, this number
becomes far below the upper bound. To shrink the gap between the upper bound
and the achievability result, a modified link activation strategy is proposed
and analyzed based on some results from random graph theory. It is shown that
this modified strategy performs very close to the optimum. Specifically, this
strategy is \emph{asymptotically almost surely} optimum when
approaches or 0. It turns out the optimality results are obtained in
an interference-limited regime. It is demonstrated that, by proper selection of
the algorithm parameters, the proposed scheme also allows the network to
operate in a noise-limited regime in which the transmission rates can be
adjusted by the transmission powers. The price for this flexibility is a
decrease in the throughput scaling law by a multiplicative factor of .Comment: Submitted to IEEE Trans. Information Theor
On Space-Time Capacity Limits in Mobile and Delay Tolerant Networks
We investigate the fundamental capacity limits of space-time journeys of
information in mobile and Delay Tolerant Networks (DTNs), where information is
either transmitted or carried by mobile nodes, using store-carry-forward
routing. We define the capacity of a journey (i.e., a path in space and time,
from a source to a destination) as the maximum amount of data that can be
transferred from the source to the destination in the given journey. Combining
a stochastic model (conveying all possible journeys) and an analysis of the
durations of the nodes' encounters, we study the properties of journeys that
maximize the space-time information propagation capacity, in bit-meters per
second. More specifically, we provide theoretical lower and upper bounds on the
information propagation speed, as a function of the journey capacity. In the
particular case of random way-point-like models (i.e., when nodes move for a
distance of the order of the network domain size before changing direction), we
show that, for relatively large journey capacities, the information propagation
speed is of the same order as the mobile node speed. This implies that,
surprisingly, in sparse but large-scale mobile DTNs, the space-time information
propagation capacity in bit-meters per second remains proportional to the
mobile node speed and to the size of the transported data bundles, when the
bundles are relatively large. We also verify that all our analytical bounds are
accurate in several simulation scenarios.Comment: Part of this work will be presented in "On Space-Time Capacity Limits
in Mobile and Delay Tolerant Networks", P. Jacquet, B. Mans and G. Rodolakis,
IEEE Infocom, 201
Parallel Opportunistic Routing in Wireless Networks
We study benefits of opportunistic routing in a large wireless ad hoc network
by examining how the power, delay, and total throughput scale as the number of
source- destination pairs increases up to the operating maximum. Our
opportunistic routing is novel in a sense that it is massively parallel, i.e.,
it is performed by many nodes simultaneously to maximize the opportunistic gain
while controlling the inter-user interference. The scaling behavior of
conventional multi-hop transmission that does not employ opportunistic routing
is also examined for comparison. Our results indicate that our opportunistic
routing can exhibit a net improvement in overall power--delay trade-off over
the conventional routing by providing up to a logarithmic boost in the scaling
law. Such a gain is possible since the receivers can tolerate more interference
due to the increased received signal power provided by the multi-user diversity
gain, which means that having more simultaneous transmissions is possible.Comment: 18 pages, 7 figures, Under Review for Possible Publication in IEEE
Transactions on Information Theor