762 research outputs found
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
Uplink capacity of a variable density cellular system with multicell processing
In this work we investigate the information theoretic capacity of the uplink of a cellular system. Assuming centralised processing for all base stations, we consider a power-law path loss model along with variable cell size (variable density of Base Stations) and we formulate an average path-loss approximation. Considering a realistic Rician flat fading environment, the analytical result for the per-cell capacity is derived for a large number of users distributed over each cell. We extend this general approach to model the uplink of sectorized cellular system. To this end, we assume that the user terminals are served by perfectly directional receiver antennas, dividing the cell coverage area into perfectly non-interfering sectors. We show how the capacity is increased (due to degrees of freedom gain) in comparison to the single receiving antenna system and we investigate the asymptotic behaviour when the number of sectors grows large. We further extend the analysis to find the capacity when the multiple antennas used for each Base Station are omnidirectional and uncorrelated (power gain on top of degrees of freedom gain). We validate the numerical solutions with Monte Carlo simulations for random fading realizations and we interpret the results for the real-world systems
Distributed antenna systems aspects and deployment
A lot of schemes are proposed to exploit the transmit diversity. Distributed antenna systems (DAS) constitute one of the most attractive schemes to efficiently achieve the stringent quality of service demands of next generation wireless networks.
In this paper, we investigated MISO assisted different transmission techniques used in DAS and the performance of downlink multi-cell DAS in terms of capacity improvement using
SINR for different transmission scheme. A system level simulation tool is used to analyze the performance
Quantifying Potential Energy Efficiency Gain in Green Cellular Wireless Networks
Conventional cellular wireless networks were designed with the purpose of
providing high throughput for the user and high capacity for the service
provider, without any provisions of energy efficiency. As a result, these
networks have an enormous Carbon footprint. In this paper, we describe the
sources of the inefficiencies in such networks. First we present results of the
studies on how much Carbon footprint such networks generate. We also discuss
how much more mobile traffic is expected to increase so that this Carbon
footprint will even increase tremendously more. We then discuss specific
sources of inefficiency and potential sources of improvement at the physical
layer as well as at higher layers of the communication protocol hierarchy. In
particular, considering that most of the energy inefficiency in cellular
wireless networks is at the base stations, we discuss multi-tier networks and
point to the potential of exploiting mobility patterns in order to use base
station energy judiciously. We then investigate potential methods to reduce
this inefficiency and quantify their individual contributions. By a
consideration of the combination of all potential gains, we conclude that an
improvement in energy consumption in cellular wireless networks by two orders
of magnitude, or even more, is possible.Comment: arXiv admin note: text overlap with arXiv:1210.843
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