5,738 research outputs found
How to Couple from the Past Using a Read-Once Source of Randomness
We give a new method for generating perfectly random samples from the
stationary distribution of a Markov chain. The method is related to coupling
from the past (CFTP), but only runs the Markov chain forwards in time, and
never restarts it at previous times in the past. The method is also related to
an idea known as PASTA (Poisson arrivals see time averages) in the operations
research literature. Because the new algorithm can be run using a read-once
stream of randomness, we call it read-once CFTP. The memory and time
requirements of read-once CFTP are on par with the requirements of the usual
form of CFTP, and for a variety of applications the requirements may be
noticeably less. Some perfect sampling algorithms for point processes are based
on an extension of CFTP known as coupling into and from the past; for
completeness, we give a read-once version of coupling into and from the past,
but it remains unpractical. For these point process applications, we give an
alternative coupling method with which read-once CFTP may be efficiently used.Comment: 28 pages, 2 figure
Maximal Ratio Transmission in Wireless Poisson Networks under Spatially Correlated Fading Channels
The downlink of a wireless network where multi-antenna base stations (BSs)
communicate with single-antenna mobile stations (MSs) using maximal ratio
transmission (MRT) is considered here. The locations of BSs are modeled by a
homogeneous Poisson point process (PPP) and the channel gains between the
multiple antennas of each BS and the single antenna of each MS are modeled as
spatially arbitrarily correlated Rayleigh random variables. We first present
novel closed-form expressions for the distribution of the power of the
interference resulting from the coexistence of one intended and one unintended
MRT over the considered correlated fading channels. The derived expressions are
then used to obtain closed-form expressions for the success probability and
area spectral efficiency of the wireless communication network under
investigation. Simulation results corroborate the validity of the presented
expressions. A key result of this work is that the effect of spatial
correlation on the network throughput may be contrasting depending on the
density of BSs, the signal-to-interference-plus-noise ratio (SINR) level, and
the background noise power.Comment: 6 pages, 6 figures, IEEE GLOBECOM 201
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