In the previous chapter, we introduced readers to spectral aggregation, a technique for acquiring increased spectrum for 5G services. In this chapter, readers will be introduced to spatial densification as a way of meeting the demand for capacity in a 5G network.

In order to meet these demands, the key technologies applied at the 5G physical layer are Network Densification, Heterogeneous Networks, Cloud Radio Access Network (RAN) and Coordinated Multipoint (COMP).

3.1 Network Densification

It simply involves the deployment of low power nodes (pico cells, femto cells, Distributed Antennas etc.) within localized regions of high traffic demand, as depicted in Fig. 3.1. It is anticipated that most traffic would originate from indoor areas, hotspots, public areas like stadiums, malls etc., hence it makes sense to deploy an overlay of small cells within the macro coverage area [7].

The goal is to offload some of the traffic from the base stations (macro cells) to the small cells which therefore improves the frequency reuse. This requires careful network planning to balance the load, address interference and backhaul challenges [7, 8].

Small cells require less power and cooling and can be deployed closer to the user and within existing networks; the deployment of small cells will lead to a reduction in CAPEX and OPEX incurred by operators [8].

The small cells could be deployed with self – organizing network capabilities which allows the cells to sense their environment, switch off when in idle mode (reduces energy consumption), coordinate with other base stations to deal with interference challenges within the environment [8].

3.2 Heterogeneous Network

The traffic bottle neck could vary from network to network. Therefore, offloading could occur between networks of the same air interface technologies (Macro/small cells) or between networks of different air interface technologies (LTE/Wi-Fi) or between mobile operator core network and public internet.

This combination of technological solutions involving the use of network of different technologies or network of multiple layers of different sizes is referred to as a Heterogeneous Network (HetNet), as clearly illustrated in Fig. 3.2.

A HetNet consists of multiple tiers of layers of different networks of different cell sizes and/or multiple radio access technologies [7, 12].

3.3 Cloud RAN for Backhaul

The deployment of a HetNet to increase capacity has to be complemented with a backhaul for this to translate into an enhanced user experience. The Cloud RAN has been proposed for backhaul purposes in 5G. In literal terms, it translates into Cloud Base Stations.

Cloud RAN involves relocating the signal processing from tens to hundreds of base stations to a centralized server platform (see Fig. 3.3); thus encouraging virtualization. It is especially suitable for high traffic demand areas like stadia and venues.

The Cloud RAN also reduces energy consumption by eliminating the need for air conditioning facilities at various sites. It is also able to adapt to the traffic demand within its geographic coverage daily [8, 12].

Besides Cloud RAN, Wireless backhaul can also be used within a 5G system.

3.4 Cooperative Communication

Base stations can cooperate among themselves by exchanging information. Cloud RAN is a special application of Cooperation among base stations.

Cooperation can either be Joint Processing or Coordinated Scheduling. In a Joint Processing Cooperative Communication system, the processing of information among the nodes takes place in a central processor. The nodes could be base stations, User Equipment (UEs), relays or even a hybrid [8]. For example, the base stations in Fig. 3.4 below exchange information that is processed in the central processor.

A joint processing Cooperation among base stations is called CoMP. COMP involves the dynamic cooperation and coordination between/among multiple geographically separated base stations to improve spectral efficiency, address interference and reduce energy consumption [8].

Whereas, in Coordinated Scheduling, exchange of information occurs among nodes but there is no need for a central processor [8].

3.5 Summary

In order to meet the increased demand for bandwidth/data, small cells are being densed in space and laid in various configurations within macro coverage areas. Besides, other air interface technologies are also been deployed and combined in clever ways, leading to the development of HetNet to provide the much needed capacity for 5G services. Cooperation among stations is also been developed as a way to meet the increased data demand; this is thus paving the way for virtualization at the radio interface.

Interoperability is no doubt vital to allow the various air interface technologies work seamlessly and fully cooperate among themselves, when deployed within a 5G network.

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This chapter addresses the spectrum requirements anticipated for 5G networks. Spectrum is a scarce finite resource; there is however a growing demand for spectrum due to the hungry data demand of consumers who want to be able to download videos in seconds, instantly connect with friends and families from various parts of the globe, share viral videos and favourite moments with one another, hashtag a political concern or even issues at work and finalize business deals remotely.

The success of 5G applications highlighted in the previous chapter is heavily dependent on the Governments and regulators support of a timely release of affordable spectrum. Within the Industry, there are several developments geared at providing spectrum and increasing the efficiency of the existing spectrum for 5G applications, termed spectral aggregation. This chapter therefore introduces the reader to the spectral aggregation methods developed for the 5G network.

2.1 Spectrum Re-farming

In order to make spectrum available, traditionally old bands are cleared of incumbents [8]. Spectrum Re-farming involves the re-assignment of frequencies previously assigned for older generations like 2G and 3G and subsequent use for 5G. This is particularly true in countries like the US and East Asia where there are no 2G services available anymore [9]. This is a cheaper and cost effective way of acquiring spectrum.

Furthermore, the digital switchover also contributed towards freeing up some spectrum; infact the 700MHz band was cleared of incumbents to provide some bandwidth for 5G. Besides 700MHz, some other bands will be re-farmed for 5G [10].

2.2 Spectrum Sharing

Spectrum sharing, as the name implies, involves sharing spectrum among various bands.

2.2.1 Spectrum Sharing – Unlicensed bands

Unlicensed spectrum (e.g. 2.4GHz) can support offloading from licensed bands. This is very important because 5G would involve a combination of different technologies like Long Term Evolution (LTE)/WiFi etc.

However, Quality of Service (QoS) cannot be guaranteed when using unlicensed spectrum; therefore spectrum sharing (with unlicensed bands) needs to be well planned and carefully integrated with licensed bands [8].

2.2.2 Spectrum Sharing – Under-utilized bands

Bands that are under-utilised in time or geography can also be utilised for 5G services e.g. TV white spaces in the US. This has led to specialized spectrum sharing techniques like Authorized Share Access (ASA) where the ASA spectrum holder only has access to the spectrum when it is not utilized by the incumbent [8]

Furthermore, certain Organisations like GSMA are pushing for regulators to encourage voluntary spectrum sharing agreements among operators or verticals, where possible [10].

2.3 New Spectrum from mm wave band

Traditionally, frequency bands used for cellular systems were within the sub-3GHz [8]. However, the need for an increased spectrum for 5G services means that the higher frequencies (30-300GHz), termed mm wave, are now been considered for use in 5G.

These frequencies were traditionally being used for satellites and radar applications. And these frequencies are able to provide a large amount of bandwidth. As the higher the frequency, the more data that can be transmitted. The huge bandwidth/data capability of the mm wave frequencies is of utmost importance to 5G applications.

But these frequencies have different propagation characteristics and thus present numerous challenges such as large path loss, shorter transmission range, signal blocking/absorption by objects, low transmission capability etc. [8]

In order to combat these propagation challenges, base stations can be situated closer to the users (which reduces the loss) and makes a good case for citing various small cells indoors. However, an issue that could arise with citing base stations closer to the public is that it may increase the publics’ concern and worry about the impact of electromagnetic radiation on their health.

At these higher frequencies, the antennas are small due to the small wavelength dimensions (from the name mm-wave); hence the signals propagate very short distances, which is an issue for signal reception [8]. Hence to maximize the signal reception, a large number of small antennas are combined within the transmitter and receiver to provide for spatial and multiplexing gain using a technique called Massive Multiple Input Multiple Output (MIMO).

Massive MIMO simply implies that the number of antennas is far greater than the number of data streams and requires hundreds/thousands of antennas, as shown below in Fig. 2.1 below [7].

Furthermore, adaptive beam-forming can also be used to target the radiation towards or away from the user, thereby reducing the interference, as depicted below in Fig. 2.2 below [7,8].

2.4 Dynamic Spectrum Management

Previously, spectrum assignment was static and regulators simply monitor that the spectrum assigned is being utilized for the right purpose. Research has shown this is inefficient and there are better ways to maximize the scarce spectrum resource. For example, dynamic spectrum allocation (e.g.  Nominet Dynamic Spectrum Management) allows for the allocation of spectrum in real time using a geo-location database by checking for the usage, location of user and the demand [11]. This increases the efficiency of the spectrum.

2.5 Spectrum Harmonization

From the foregoing, it is clear that 5G would rely on spectrum from the low band, mid band to the high band. For this reason, a new air interface, called 5G New Radio (NR), has been developed to support these wide range of bands, as depicted below in Fig. 2.3. The 5G NR will be discussed further in the next chapter. Fig. 2.3 shows that LTE works within the sub 6GHz whereas 5G NR would operate over a wide range of bands.

The effective use of frequencies in different bands is critical to the success of 5G services and therefore places huge emphasis on spectrum harmonization as the key to minimising cross border interference, facilitating international roaming agreements and reducing the cost of mobile devices [10].

2.6 Summary

It is clear from this chapter that the spectrum needed for 5G would be realized in different bands: Sub-1GHz for widespread coverage and Internet of Things (IoT) services, 1-6GHz for coverage and capacity and mm wave band for higher capacity; hence spectrum harmonization will vital in delivering the huge promises anticipated from 5G applications [10].

Furthermore, it has been noted that spectrum pricing in developing countries, are on average more than three times higher than in developed countries, after taken into considering the income levels within the country, in order to maximise revenues. This therefore leads to slower broadband services and worse coverage. These costs are often transferred to the consumers which therefore widens the digital gap. In order to accelerate the adoption of 5G services, regulators are advised to set affordable spectrum prices based on the market forces [10, 13].

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This chapter will introduce the reader to 5G cellular generation network, cover its widespread applications within different industries (verticals) and highlight some ethical impact of 5G and emerging technologies on society.

5G refers to the Fifth Generation Cellular Network. Every ten years, there is always a shift from previous generation onto a newer generation, as depicted in Fig. 1.1 below.

In 1991, the development of GSM made voice calls to become reliable and cheaper and encouraged the widespread adoption of SMS and MMS. 1n 2001, 3G ushered in an era of data services and allowed workers access to emails from any location and this increased work productivity. 1n 2010, 4G led to the development of mobile internet and video based applications which triggered the development of many sectors like online shopping, e-banking etc [1]. 2020 is not going to be different as it promises an era of high speed connectivity, ubiquitous coverage, massive data and low latency, all thanks to 5G.

1.1 What is 5G?

5G represents a shift from consumer technologies to industrial technologies as it promises to lead to the development of a highly automated and intelligent environment which would revolutionise many industries and every part of the society as shown above in Fig. 1.2.

It is a newer generation which presents different opportunities to different stakeholders depending on where your interests lie. To an equipment vendor like Ericsson, 5G represents a market opportunity to drum up the sales of infrastructures like small cells etc. To an academic, 5G would provide an opportunity to solve complex research problems within the Communications Industry.

To a car manufacturer, 5G simply represents the opportunity to make revenues from new offerings like connected cars. To a regulator, 5G would lead to the opportunity to make increased profits from new spectrum release and lots of debate on band issues etc. To telcos, it may represent a way to increase revenue, consider new offerings (verticals) and address the increased competition from over the top (OTTs) applications like WhatsApp etc.

For the technology media, it’s an opportunity to increase subscription audience and perhaps pitch the development and deployment of 5G as a race between countries or operators.

The International Telecommunication Union (ITU) has classified 5G in terms of three use-cases presented below:

1. Enhanced Mobile Broadband: It is simply an extension of 4G and promises a speed of 10/20Gbps for either your uplink/downlink. In literal terms, as a user, you should be able to download an HD film in seconds [7].
2. Ultra-Reliable and Low latency: Here, a stringent requirement of less than a milli-sec of delay is anticipated for applications like autonomous driving and remote surgery e.g. imagine a robot performing a surgery operation during an emergency, a delay could have damning consequence [7]
3. Machine to Machine type Communications: allow for IoT based applications, 10^6 devices per km^2 e.g. smart metering, smart city, smart agriculture etc. [7]

1.2 Applications of 5G

5G will be a major technology in growing industrial digitization applications. For example,

• Transportation System: Autonomous cars will revolutionise transportation (see Fig. 1.3 below) which would reduce commute time, allow passengers to concentrate on other tasks and reduce accident due to human error [2].
• Smart Cities: Highly Efficient Transport Systems would therefore lead to the development of smart cities where for example, connected sensors can help in determining the water level of a city and predict when and whether a city will be flooded or otherwise [3]. Connected sensors can also help direct passengers to the nearest parking spaces with available facilities [4].
• Health Care: Internet of skills alongside remote surgery can help to improve health care in developing as well as developed countries. For instance, a surgeon in remote Africa can perform complex surgical procedures through video access to the best surgeon in the world. Robots can be made to perform precise and complex surgical operations thereby reducing the death rate from human error, as depicted in Fig. 1.4 below. 5G will also aid the remote monitoring of patients who need mobility assistance or are residing far away from hospitals or clinics. Drones can also be used to deliver drugs in remote places in developing countries e.g. this is already happening in Malawi, Ghana etc. [5].

• Package Delivery: Amazon is already testing the use of drones to deliver its packages in the US, as depicted in Fig. 1.5 below. This is particularly useful in rural or remote areas, where it takes a significant amount of time for packages to arrive using the current system.

 

Figure 1.5: Drone delivering an Amazon package [24]

• Industry 4.0: The use of robots, automated machines and sensors etc. would lead to Industry 4.0 which would bring about the development of highly automated and efficient factories and industries. Machines in factories can therefore be programmed to order for maintenance support and spare parts through the use of automated sensors.
• Smart Agriculture: Food production can be increased through smart agricultural initiatives like the use of sensors to predict the right level of water and fertilizer to apply to different parts of the farm [6].

Livestock management can be enhanced through the use of connected sensors monitoring the welfare of the animals. Robots can be employed to harvest and perform farming operations. Farmers and Buyers can be connected through Artificial Intelligent System, thereby reducing food wastage. Weather conditions can also be predicted for agricultural processes using Big Data [5].

• Smart Home: Homes can be made smarter through smart energy and other smart homes applications, for example, one can programme a refrigerator to order groceries online when exhausted, see Fig. 1.6 above. Smart energy can help in reducing the energy consumption within the home.
• Future of Work: Labour force need not be restricted to a geographic location through smart educational initiatives and internet of skills.
• Fintech: Mobile money and other electronic bank transactions would make bank transactions faster which would make life easier.
• E-commerce: Consumers are able to purchase products and services from any geographic location as we are already witnessing.
• Education: Robots can serve as educational Instructors and has huge implications for developing countries where there is a shortage of such professionals [5]. 

1.3 Ethical Implication of 5G

It is very clear from the foregoing that 5G, alongside other emerging technologies, would lead to a disruption in all parts of the Society. For example, certain jobs will no longer be available as robots will replace humans. This will of course engage ethical questions like:

1. Should robots have the same rights as humans?
2. Should robots be taxed for every job they replace?
3. If robots can think and have emotions, what would then make us human?
4. How do we ensure that there are no security breaches in our digitally interconnected world?
5. How do we ensure that data theft and privacy concerns are respected in the wake of fake news, terrorism, profiling of individuals?
6. How do we protect the society from the use of autonomous weapons?
7. Will these technologies widen or reduce the existing inequalities within the world?
8. Will these technologies reduce or increase the gender bias or the digital divide within the world?

These and more questions need to be addressed so that the benefits of these technologies can be maximized whilst minimizing the risks [5].

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