Conference Paper

A Study on Hierarchical Cellular Structures with Inter-Layer Reuse in an Enhanced GSM Radio Network

Tech. Univ. Dresden
DOI: 10.1109/MOMUC.1999.819497 Conference: Mobile Multimedia Communications, 1999. (MoMuC '99) 1999 IEEE International Workshop on
Source: IEEE Xplore


In today's cellular networks it becomes harder to provide the
resources for the increasing and fluctuating traffic demand exactly in
the place and at the time where and when they are needed. Moreover,
frequency planning for a hierarchical cellular network, especially to
cover indoor areas and hot-spots is a complicated and expensive task.
Therefore, we study the ability of hierarchical cellular structures with
inter-layer reuse to increase the capacity of a GSM (Global System for
Mobile Communications) radio network by applying total frequency hopping
(T-FH) and adaptive frequency allocation (AFA) as a strategy to reuse
the macro- and microcell resources without frequency planning in indoor
picocells. The presented interference analysis indicates a considerable
interference reduction gain by T-FH in conjunction with AFA, which can
be used for carrying an additional indoor traffic of more than 300
Erlang/km2, i.e. increasing the spectral efficiency by over
50%, namely 33 Erlang/km2/MHz. From these results we draw a
number of general conclusions for the design of hierarchical cellular
structures in future mobile radio networks. For example, we may conclude
that they require reuse strategies that not only adapt to the current
local interference situation, but additionally distribute the remaining
interference to as many resources as possible. For a hierarchical GSM
network this requirement is fulfilled by the T-FH/AFA technique very

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    • "Hot spots are uniformly distributed, and the minimum distance between two hotspot centres is 40 m. Note that 300 active UEs per square km is the density usually considered in dense urban scenarios, such as Manhattan [61]. "
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    ABSTRACT: Todays heterogeneous networks comprised of mostly macrocells and indoor small cells will not be able to meet the upcoming traffic demands. Indeed, it is forecasted that at least a 100x network capacity increase will be required to meet the traffic demands in 2020. As a result, vendors and operators are now looking at using every tool at hand to improve network capacity. In this epic campaign, three paradigms are noteworthy, i.e., network densification, the use of higher frequency bands and spectral efficiency enhancement techniques. This paper aims at bringing further common understanding and analysing the potential gains and limitations of these three paradigms, together with the impact of idle mode capabilities at the small cells as well as the user equipment density and distribution in outdoor scenarios. Special attention is paid to network densification and its implications when transitioning to ultra-dense small cell deployments. Simulation results show that network densification with an average inter site distance of 35 m can increase the cell- edge UE throughput by up to 48x, while the use of the 10GHz band with a 500MHz bandwidth can increase the network capacity up to 5x. The use of beamforming with up to 4 antennas per small cell base station lacks behind with cell-edge throughput gains of up to 1.49x. Our study also shows how network densifications reduces multi-user diversity, and thus proportional fair alike schedulers start losing their advantages with respect to round robin ones. The energy efficiency of these ultra-dense small cell deployments is also analysed, indicating the need for energy harvesting approaches to make these deployments energy- efficient. Finally, the top ten challenges to be addressed to bring ultra-dense small cell deployments to reality are also discussed.
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    • "different classes of users (usually classified by speed) are initially assigned to the proper types of cells (that in proper tier). We call this kind of cellular network a hierarchical cellular network [10]. Macro cells are used for high speed users, micro cells for low speed users (pedestrians) and pico cells for in-building use or stationary users. "
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    ABSTRACT: With the exponentially increasing demand for wireless communications the capacity of current cellular systems will soon become incapable of handling the growing traffic. Since radio frequencies are diminishing natural resources, there seems to be a fundamental barrier to further capacity increase. The solution can be found by using smart antenna systems. Smart or adaptive antenna arrays consist of an array of antenna elements with signal processing capability that optimizes the radiation and reception of a desired signal, dynamically. Smart antenna can place nulls in the direction of interferers via adapting adaptive updating of weights linked to each antenna element. They thus cancel out most of the cochannel interference resulting in better quality of reception and lower dropped calls. Smart antenna can also track the user within a cell via direction of arrival algorithms. This paper focuses on about the smart antenna in hierarchical cell clustering (overlay-underlay) with demand based frequency allocation techniques in cellular mobile radio networks in INDIA.
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    • "This work utilizes a multiplicity of techniques, with an innovation in the frequency-hopping domain [1]. This paper presents the results of analytical and simulation studies of the combined effects of frequency-hopping and a special form of dynamic channel allocation (DCA) manifested by frequency-hop pattern adaptation [2]–[6]. Frequency hopping (FH) can introduce frequency diversity and interference diversity. "
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    ABSTRACT: We examine techniques for increasing spectral efficiency of cellular systems by using slow frequency hopping (FH) with dynamic frequency-hop (DFH) pattern adaptation. We first present analytical results illustrating the improvements in frequency outage probabilities obtained by DFH in comparison with random frequency hopping (RFH). Next, we show simulation results comparing the performance of various DFH and RFH techniques. System performance is expressed by cumulative distribution functions of codeword error rates. Systems that we study incorporate channel coding, interleaving, antenna diversity, and power control. Analysis and simulations consider the effects of path loss, shadowing, Rayleigh fading, cochannel interference, coherence bandwidth, voice activity, and occupancy. The results indicate that systems using DFH can support substantially more users than systems using RFH
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