28 research outputs found
On Capacity Scaling in Arbitrary Wireless Networks
In recent work, Ozgur, Leveque, and Tse (2007) obtained a complete scaling
characterization of throughput scaling for random extended wireless networks
(i.e., nodes are placed uniformly at random in a square region of area
). They showed that for small path-loss exponents
cooperative communication is order optimal, and for large path-loss exponents
multi-hop communication is order optimal. However, their results
(both the communication scheme and the proof technique) are strongly dependent
on the regularity induced with high probability by the random node placement.
In this paper, we consider the problem of characterizing the throughput
scaling in extended wireless networks with arbitrary node placement. As a main
result, we propose a more general novel cooperative communication scheme that
works for arbitrarily placed nodes. For small path-loss exponents , we show that our scheme is order optimal for all node placements, and
achieves exactly the same throughput scaling as in Ozgur et al. This shows that
the regularity of the node placement does not affect the scaling of the
achievable rates for . The situation is, however, markedly
different for large path-loss exponents . We show that in this
regime the scaling of the achievable per-node rates depends crucially on the
regularity of the node placement. We then present a family of schemes that
smoothly "interpolate" between multi-hop and cooperative communication,
depending upon the level of regularity in the node placement. We establish
order optimality of these schemes under adversarial node placement for .Comment: 38 pages, 6 figures, to appear in IEEE Transactions on Information
Theor
Information-theoretic Capacity of Clustered Random Networks
We analyze the capacity scaling laws of clustered ad hoc networks in which
nodes are distributed according to a doubly stochastic shot-noise Cox process.
We identify five different operational regimes, and for each regime we devise a
communication strategy that allows to achieve a throughput to within a
poly-logarithmic factor (in the number of nodes) of the maximum theoretical
capacity.Comment: 6 pages, in Proceedings of ISIT 201
Information Theoretic Operating Regimes of Large Wireless Networks
In analyzing the point-to-point wireless channel, insights about two
qualitatively different operating regimes--bandwidth- and power-limited--have
proven indispensable in the design of good communication schemes. In this
paper, we propose a new scaling law formulation for wireless networks that
allows us to develop a theory that is analogous to the point-to-point case. We
identify fundamental operating regimes of wireless networks and derive
architectural guidelines for the design of optimal schemes.
Our analysis shows that in a given wireless network with arbitrary size,
area, power, bandwidth, etc., there are three parameters of importance: the
short-distance SNR, the long-distance SNR, and the power path loss exponent of
the environment. Depending on these parameters we identify four qualitatively
different regimes. One of these regimes is especially interesting since it is
fundamentally a consequence of the heterogeneous nature of links in a network
and does not occur in the point-to-point case; the network capacity is {\em
both} power and bandwidth limited. This regime has thus far remained hidden due
to the limitations of the existing formulation. Existing schemes, either
multihop transmission or hierarchical cooperation, fail to achieve capacity in
this regime; we propose a new hybrid scheme that achieves capacity.Comment: 12 pages, 5 figures, to appear in IEEE Transactions on Information
Theor
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