36,400 research outputs found
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
A New Cell Association Scheme In Heterogeneous Networks
Cell association scheme determines which base station (BS) and mobile user
(MU) should be associated with and also plays a significant role in determining
the average data rate a MU can achieve in heterogeneous networks. However, the
explosion of digital devices and the scarcity of spectra collectively force us
to carefully re-design cell association scheme which was kind of taken for
granted before. To address this, we develop a new cell association scheme in
heterogeneous networks based on joint consideration of the
signal-to-interference-plus-noise ratio (SINR) which a MU experiences and the
traffic load of candidate BSs1. MUs and BSs in each tier are modeled as several
independent Poisson point processes (PPPs) and all channels experience
independently and identically distributed ( i.i.d.) Rayleigh fading. Data rate
ratio and traffic load ratio distributions are derived to obtain the tier
association probability and the average ergodic MU data rate. Through numerical
results, We find that our proposed cell association scheme outperforms cell
range expansion (CRE) association scheme. Moreover, results indicate that
allocating small sized and high-density BSs will improve spectral efficiency if
using our proposed cell association scheme in heterogeneous networks.Comment: Accepted by IEEE ICC 2015 - Next Generation Networking Symposiu
Modeling Heterogeneous Network Interference Using Poisson Point Processes
Cellular systems are becoming more heterogeneous with the introduction of low
power nodes including femtocells, relays, and distributed antennas.
Unfortunately, the resulting interference environment is also becoming more
complicated, making evaluation of different communication strategies
challenging in both analysis and simulation. Leveraging recent applications of
stochastic geometry to analyze cellular systems, this paper proposes to analyze
downlink performance in a fixed-size cell, which is inscribed within a weighted
Voronoi cell in a Poisson field of interferers. A nearest out-of-cell
interferer, out-of-cell interferers outside a guard region, and cross-tier
interference are included in the interference calculations. Bounding the
interference power as a function of distance from the cell center, the total
interference is characterized through its Laplace transform. An equivalent
marked process is proposed for the out-of-cell interference under additional
assumptions. To facilitate simplified calculations, the interference
distribution is approximated using the Gamma distribution with second order
moment matching. The Gamma approximation simplifies calculation of the success
probability and average rate, incorporates small-scale and large-scale fading,
and works with co-tier and cross-tier interference. Simulations show that the
proposed model provides a flexible way to characterize outage probability and
rate as a function of the distance to the cell edge.Comment: Submitted to the IEEE Transactions on Signal Processing, July 2012,
Revised December 201
Joint Resource Partitioning and Offloading in Heterogeneous Cellular Networks
In heterogeneous cellular networks (HCNs), it is desirable to offload mobile
users to small cells, which are typically significantly less congested than the
macrocells. To achieve sufficient load balancing, the offloaded users often
have much lower SINR than they would on the macrocell. This SINR degradation
can be partially alleviated through interference avoidance, for example time or
frequency resource partitioning, whereby the macrocell turns off in some
fraction of such resources. Naturally, the optimal offloading strategy is
tightly coupled with resource partitioning; the optimal amount of which in turn
depends on how many users have been offloaded. In this paper, we propose a
general and tractable framework for modeling and analyzing joint resource
partitioning and offloading in a two-tier cellular network. With it, we are
able to derive the downlink rate distribution over the entire network, and an
optimal strategy for joint resource partitioning and offloading. We show that
load balancing, by itself, is insufficient, and resource partitioning is
required in conjunction with offloading to improve the rate of cell edge users
in co-channel heterogeneous networks
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