338 research outputs found
Exploiting Regional Differences: A Spatially Adaptive Random Access
In this paper, we discuss the potential for improvement of the simple random
access scheme by utilizing local information such as the received
signal-to-interference-plus-noise-ratio (SINR). We propose a spatially adaptive
random access (SARA) scheme in which the transmitters in the network utilize
different transmit probabilities depending on the local situation. In our
proposed scheme, the transmit probability is adaptively updated by the ratio of
the received SINR and the target SINR. We investigate the performance of the
spatially adaptive random access scheme. For the comparison, we derive an
optimal transmit probability of ALOHA random access scheme in which all
transmitters use the same transmit probability. We illustrate the performance
of the spatially adaptive random access scheme through simulations. We show
that the performance of the proposed scheme surpasses that of the optimal ALOHA
random access scheme and is comparable with the CSMA/CA scheme.Comment: 10 pages, 10 figure
High-SIR Transmission Capacity of Wireless Networks with General Fading and Node Distribution
In many wireless systems, interference is the main performance-limiting
factor, and is primarily dictated by the locations of concurrent transmitters.
In many earlier works, the locations of the transmitters is often modeled as a
Poisson point process for analytical tractability. While analytically
convenient, the PPP only accurately models networks whose nodes are placed
independently and use ALOHA as the channel access protocol, which preserves the
independence. Correlations between transmitter locations in non-Poisson
networks, which model intelligent access protocols, makes the outage analysis
extremely difficult. In this paper, we take an alternative approach and focus
on an asymptotic regime where the density of interferers goes to 0. We
prove for general node distributions and fading statistics that the success
probability \p \sim 1-\gamma \eta^{\kappa} for , and
provide values of and for a number of important special
cases. We show that is lower bounded by 1 and upper bounded by a value
that depends on the path loss exponent and the fading. This new analytical
framework is then used to characterize the transmission capacity of a very
general class of networks, defined as the maximum spatial density of active
links given an outage constraint.Comment: Submitted to IEEE Trans. Info Theory special issu
Interference and Throughput in Aloha-based Ad Hoc Networks with Isotropic Node Distribution
We study the interference and outage statistics in a slotted Aloha ad hoc
network, where the spatial distribution of nodes is non-stationary and
isotropic. In such a network, outage probability and local throughput depend on
both the particular location in the network and the shape of the spatial
distribution. We derive in closed-form certain distributional properties of the
interference that are important for analyzing wireless networks as a function
of the location and the spatial shape. Our results focus on path loss exponents
2 and 4, the former case not being analyzable before due to the stationarity
assumption of the spatial node distribution. We propose two metrics for
measuring local throughput in non-stationary networks and discuss how our
findings can be applied to both analysis and optimization.Comment: 5 pages, 3 figures. To appear in International Symposium on
Information Theory (ISIT) 201
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