Impact of Non-Typical Antenna Configurations on Higher Order Sectored Sites in Ultra Dense Networks

Impact of Non-Typical Antenna Configurations on Higher Order Sectored Sites in Ultra Dense Networks

Muhammad Usman Sheikh (Department of Electronics and Communications Engineering, Tampere University of Technology (TUT), Tampere, Finland) and Jukka Lempiäinen (Department of Electronics and Communications Engineering, Tampere University of Technology (TUT), Tampere, Finland)
DOI: 10.4018/IJITN.2017070103
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The site densification and higher order sectorization are the two well-known possible ways of increasing the system capacity. However, to take the full advantage of these techniques they should be implemented with optimum antenna configuration. The target of this paper is to highlight the gain of using an optimized antenna configuration for 3-, and 6-sector sites in achieving a better quality (SINR) and capacity. Generally, a 3-sector site is deployed with 65° HPBW antenna; however, it was observed that for ultra-dense networks i.e. 100 m to 250 m ISD distance 3-sector site gives better result with 32° HPBW antenna. Similarly, performance of 6-sector site was found better with 16° HPBW antenna at small ISDs, whereas at large intersite distances the 32° HPBW antenna was found to be a preferred choice. It was observed that spectral efficiency of the cell degrades with site densification and higher order sectorization, but the overall capacity of a system improves due to more number of sectors and cells.
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1. Introduction

Mobile networks have evolved tremendously in the last two decades. Indicators are showing that in future the internet and mobile traffic will increase at an exponential rate, and in the coming years the number of mobile devices connected to the network will surpass the number of people on planet “Earth”. By the year 2019 there will be nearly 1.5 devices per person (Cisco White Paper, 2015). In terms of coverage and data rates the expectations from users have also gone high. Users now expect to have high data rates with continuous and homogeneous coverage. Enormous growth in smartphones’ penetration, hunger of higher per user data rates, cheap data plans etc., act as a catalyst for the multifold increase in capacity demand. To fulfill the requirement of services of such a large number of connected devices, a mobile network needs to provide a huge capacity. There are several ways by which the network capacity can be enhanced e.g. by adding more spectrum, by site densification as shown in references (Bhushan et al., 2014; Yunas, Valkama, & Niemelä, 2015; Richter & Fettweis, 2010; Hiltunen, 2011), by sector densification i.e. higher order sectorization (Sheikh & Lempiainen, 2013) (Sheikh, Ahnlund & Lempiainen, 2013), by deploying heterogeneous network i.e. mix of macro, micros, femtos and picos (Hwang, Song & Soliman, 2013) (Soh et al., 2013), by using Multiple Input Multiple Output (MIMO) antennas using spatial multiplexing (Sheikh, Jagusz, & Lempiainen, 2011), by using smart adaptive antennas, by using higher order modulation and coding scheme etc. However, this paper focuses only on site densification and higher order sectorization. In heterogeneous networks, still a macro layer is considered as a baseline layer for providing a basic coverage and capacity to the users. Therefore, in this paper a special attention is given to macro and micro sites only.

Frequency spectrum is the scarce and limited resources. Therefore, most of the time adding a spectrum is not a possible solution for the mobile operators. However, to increase the network capacity, we can reuse the allocated spectrum as frequently as possible. By increasing the site density in a certain geographical area, the intersite distance between the sites is reduced. It means that more often the same frequency resources can be reused which can result in larger system capacity. Theoretically, an increase in the capacity of a network should be directly proportional to the increase in the density of sites. However, it is reported by (Yunas et al., 2015) and (Yunas et al., 2013) that the gain of site densification starts to saturate in dense networks due to severe interference coming from the neighboring sites. In real networks, sometimes the identified site location in nominal plan is not available for acquisition or landlord does not allow placing an antenna mast there. In such situation, the higher order sectorization is a feasible solution to increase the site capacity without adding an additional site. In case of higher order sectorization the number of sectors at an existing site is increased from three to six sectors or even higher. From the OPEX and CAPEX point of view, the higher order sectorization is an attractive solution for mobile operators (Sheikh & Lempiainen, 2013) (Sheikh, Ahnlund, & Lempiainen, 2013).

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