Higher order sectorization and the site densification are the two renowned solutions for the cellular system capacity crunch. However, in order to take adequate benefits of these techniques they should be implemented with optimal antenna configuration. This chapter highlights the gain of using an optimized antenna configuration for three- and six-sector sites in achieving a better network coverage and network quality (i.e., capacity). Unlike traditional wide 65° HPBW antenna, this chapter also focuses on the use of other narrow HPBW antennas for three- and six-sector sites. This chapter provides detailed analysis of network performance from coverage, capacity, spectral-efficiency, power-efficiency, and cost-efficiency point of view. It also provides a fair comparison between the network rollout with traditional three-sector sites and higher order six-sector sites. Similarly, the impact of site densification along with sector densification is also studied in this chapter.
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Mobile networks have evolved tremendously in the last two decades. Indicators are showing that in future the internet and the 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 Chapter, 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 chapter 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 chapter a special attention is given to macro and micro sites only.
Frequency spectrum is the scarce and limited resource. 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). In a network with macro site deployment, it is challenging to avoid interference from the neighboring sites. Signal propagation can be restricted by lowering the antenna height, and also by tilting the antenna in the downward direction. In case of micro sites, generally the antennas are placed on the building walls and below the average rooftops which helps in minimizing the interference in system (Lempiainen & Manninen, 2001). Antenna downtilting can be achieved either by mechanically tilting the antenna in downward direction, or by electrically changing the phase of the antenna elements (Athley et al., 2010). With the help of Remote Electrical Tilt (RET), an antenna can be electrically down tilted without physically visiting the site, which can save a handsome amount of operational cost (OPEX) for the mobile operators. Antenna down tilting can provide a certain level of inter-cell interference reduction and beamforming gain (Athley et al., 2010). Similarly, adopting an antenna with narrow beamwidth can also help in interference reduction.