7,378 research outputs found
A Tractable Approach to Coverage and Rate in Cellular Networks
Cellular networks are usually modeled by placing the base stations on a grid,
with mobile users either randomly scattered or placed deterministically. These
models have been used extensively but suffer from being both highly idealized
and not very tractable, so complex system-level simulations are used to
evaluate coverage/outage probability and rate. More tractable models have long
been desirable. We develop new general models for the multi-cell
signal-to-interference-plus-noise ratio (SINR) using stochastic geometry. Under
very general assumptions, the resulting expressions for the downlink SINR CCDF
(equivalent to the coverage probability) involve quickly computable integrals,
and in some practical special cases can be simplified to common integrals
(e.g., the Q-function) or even to simple closed-form expressions. We also
derive the mean rate, and then the coverage gain (and mean rate loss) from
static frequency reuse. We compare our coverage predictions to the grid model
and an actual base station deployment, and observe that the proposed model is
pessimistic (a lower bound on coverage) whereas the grid model is optimistic,
and that both are about equally accurate. In addition to being more tractable,
the proposed model may better capture the increasingly opportunistic and dense
placement of base stations in future networks.Comment: Submitted to IEEE Transactions on Communication
Stochastic Geometry Modeling of Cellular Networks: Analysis, Simulation and Experimental Validation
Due to the increasing heterogeneity and deployment density of emerging
cellular networks, new flexible and scalable approaches for their modeling,
simulation, analysis and optimization are needed. Recently, a new approach has
been proposed: it is based on the theory of point processes and it leverages
tools from stochastic geometry for tractable system-level modeling, performance
evaluation and optimization. In this paper, we investigate the accuracy of this
emerging abstraction for modeling cellular networks, by explicitly taking
realistic base station locations, building footprints, spatial blockages and
antenna radiation patterns into account. More specifically, the base station
locations and the building footprints are taken from two publicly available
databases from the United Kingdom. Our study confirms that the abstraction
model based on stochastic geometry is capable of accurately modeling the
communication performance of cellular networks in dense urban environments.Comment: submitted for publicatio
Coverage Analysis for Millimeter Wave Cellular Networks with Beam Alignment Errors
Millimeter wave (mmWave) communication is a promising approach to satisfy the demanding high data rate requirement of next generation mobile communications. This paper studies the downlink coverage performance of mmWave cellular networks with beam alignment errors. An enhanced antenna model is adopted to model the directional antenna beamforming pattern, in which the mainlobe beamwidth and directivity gains can be expressed as functions of the number of elements in the antenna array. After deriving the probability density function (PDF) of distance between mobile station (MS) and its serving base station (BS), the directivity gain with beam alignment errors is obtained as a discrete random variable. Then, a computationally tractable expression is derived for the coverage probability of mmWave cellular networks. Numerical results indicate that small beam alignment errors will not deteriorate the coverage probability significantly. Moreover, when the beam alignment error is small enough, the coverage performance can be improved by increasing the number of elements in the antenna array
Average Rate of Downlink Heterogeneous Cellular Networks over Generalized Fading Channels - A Stochastic Geometry Approach
In this paper, we introduce an analytical framework to compute the average
rate of downlink heterogeneous cellular networks. The framework leverages
recent application of stochastic geometry to other-cell interference modeling
and analysis. The heterogeneous cellular network is modeled as the
superposition of many tiers of Base Stations (BSs) having different transmit
power, density, path-loss exponent, fading parameters and distribution, and
unequal biasing for flexible tier association. A long-term averaged maximum
biased-received-power tier association is considered. The positions of the BSs
in each tier are modeled as points of an independent Poisson Point Process
(PPP). Under these assumptions, we introduce a new analytical methodology to
evaluate the average rate, which avoids the computation of the Coverage
Probability (Pcov) and needs only the Moment Generating Function (MGF) of the
aggregate interference at the probe mobile terminal. The distinguishable
characteristic of our analytical methodology consists in providing a tractable
and numerically efficient framework that is applicable to general fading
distributions, including composite fading channels with small- and mid-scale
fluctuations. In addition, our method can efficiently handle correlated
Log-Normal shadowing with little increase of the computational complexity. The
proposed MGF-based approach needs the computation of either a single or a
two-fold numerical integral, thus reducing the complexity of Pcov-based
frameworks, which require, for general fading distributions, the computation of
a four-fold integral.Comment: Accepted for publication in IEEE Transactions on Communications, to
appea
Modeling and Analysis of K-Tier Downlink Heterogeneous Cellular Networks
Cellular networks are in a major transition from a carefully planned set of
large tower-mounted base-stations (BSs) to an irregular deployment of
heterogeneous infrastructure elements that often additionally includes micro,
pico, and femtocells, as well as distributed antennas. In this paper, we
develop a tractable, flexible, and accurate model for a downlink heterogeneous
cellular network (HCN) consisting of K tiers of randomly located BSs, where
each tier may differ in terms of average transmit power, supported data rate
and BS density. Assuming a mobile user connects to the strongest candidate BS,
the resulting Signal-to-Interference-plus-Noise-Ratio (SINR) is greater than 1
when in coverage, Rayleigh fading, we derive an expression for the probability
of coverage (equivalently outage) over the entire network under both open and
closed access, which assumes a strikingly simple closed-form in the high SINR
regime and is accurate down to -4 dB even under weaker assumptions. For
external validation, we compare against an actual LTE network (for tier 1) with
the other K-1 tiers being modeled as independent Poisson Point Processes. In
this case as well, our model is accurate to within 1-2 dB. We also derive the
average rate achieved by a randomly located mobile and the average load on each
tier of BSs. One interesting observation for interference-limited open access
networks is that at a given SINR, adding more tiers and/or BSs neither
increases nor decreases the probability of coverage or outage when all the
tiers have the same target-SINR.Comment: IEEE Journal on Selected Areas in Communications, vol. 30, no. 3, pp.
550 - 560, Apr. 201
The Intensity Matching Approach: A Tractable Stochastic Geometry Approximation to System-Level Analysis of Cellular Networks
The intensity matching approach for tractable performance evaluation and
optimization of cellular networks is introduced. It assumes that the base
stations are modeled as points of a Poisson point process and leverages
stochastic geometry for system-level analysis. Its rationale relies on
observing that system-level performance is determined by the intensity measure
of transformations of the underlaying spatial Poisson point process. By
approximating the original system model with a simplified one, whose
performance is determined by a mathematically convenient intensity measure,
tractable yet accurate integral expressions for computing area spectral
efficiency and potential throughput are provided. The considered system model
accounts for many practical aspects that, for tractability, are typically
neglected, e.g., line-of-sight and non-line-of-sight propagation, antenna
radiation patterns, traffic load, practical cell associations, general fading
channels. The proposed approach, more importantly, is conveniently formulated
for unveiling the impact of several system parameters, e.g., the density of
base stations and blockages. The effectiveness of this novel and general
methodology is validated with the aid of empirical data for the locations of
base stations and for the footprints of buildings in dense urban environments.Comment: Submitted for Journal Publicatio
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