3,786 research outputs found
On the Delay-Throughput Tradeoff in Distributed Wireless Networks
This paper deals with the delay-throughput analysis of a single-hop wireless
network with transmitter/receiver pairs. All channels are assumed to be
block Rayleigh fading with shadowing, described by parameters
, where denotes the probability of shadowing and
represents the average cross-link gains. The analysis relies on the
distributed on-off power allocation strategy (i.e., links with a direct channel
gain above a certain threshold transmit at full power and the rest remain
silent) for the deterministic and stochastic packet arrival processes. It is
also assumed that each transmitter has a buffer size of one packet and dropping
occurs once a packet arrives in the buffer while the previous packet has not
been served. In the first part of the paper, we define a new notion of
performance in the network, called effective throughput, which captures the
effect of arrival process in the network throughput, and maximize it for
different cases of packet arrival process. It is proved that the effective
throughput of the network asymptotically scales as , with , regardless of
the packet arrival process. In the second part of the paper, we present the
delay characteristics of the underlying network in terms of the packet dropping
probability. We derive the sufficient conditions in the asymptotic case of such that the packet dropping probability tend to zero, while
achieving the maximum effective throughput of the network. Finally, we study
the trade-off between the effective throughput, delay, and packet dropping
probability of the network for different packet arrival processes.Comment: Submitted to IEEE Transactions on Information Theory (34 pages
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
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
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