The uses of radio spectrum

Introduction

The use of radio spectrum is at the heart of almost all aspects of daily personal, business and government activities. Life without the services reliant upon spectrum would be unthinkable – either no or very limited TV, radio, Internet, air travel, mobile phones, and much, much more. In this section, we provide an overview of the key uses of radio spectrum, their current allocations, and their likely future needs. As an illustration, Figure 1-1 shows the key uses of the spectrum in the UK and their current split of allocations across broad frequency bands.

In interpreting the figure (and recalling that it refers only to the UK) it is, first, worth noting that the usage of all frequency bands will add to greater than 100%. This is because much of the band is shared, and in the chart, if two applications both shared, say, 10% of the band, both would be considered to be using this 10% since it is typically very hard to divide up shared utilization. On this basis, some uses appear overstated: for example, program making and special equipment (PMSE), which is broadly the use of wireless microphones and cameras, appears to have more access to spectrum below 1 GHz than mobile telecommunications, but all the PMSE allocation is shared with broadcasting and PMSE needs to work around broadcasting, giving it little “real” allocation in practice.

In the figure the use is split into four different frequency bands. The advantages and disadvantages of different frequencies are discussed in more detail in the next chapter. Suffice it to say here that the bands below 6 GHz are considered much more valuable than those above and that the band below 1 GHz is especially useful where long-range propagation is required. We now turn to each of the sectors to provide a brief overview.

The public sector

The public sector encompasses all governmental (local, regional, and national) use, which is very varied.

This book consists of four parts:

The first is a primer, designed to ensure that all readers have sufficient knowledge to tackle the material in the rest of the book. It covers spectrum management fundamentals, technical issues, and basic economics.

The second covers conventional economic methods of spectrum management, such as auctions, trading, and pricing, which have been evolving for a decade or more.

The third looks at spectrum management approaches which we believe will become more prominent in future, including shared and dynamic spectrum access and new ways of licensing based on interference caused.

The fourth looks at some case studies and issues. It uses the UHF TV band to illustrate a number of principles from earlier chapters, considers approaches that might be adopted in the public sector in international spectrum management, and examines the role of spectrum in the wider economy. Finally, it contains our projection of trends and the key agenda which we think needs to be tackled.

The challenge for the regulator remains the same as always – to maximize the value of the use of radio spectrum through ensuring that the highest-value users have access to the spectrum and that the interference between them remains controlled to an optimal level. However, the solution to this challenge is constantly changing as usage patterns change and new tools to manage users develop, often based on changing technology. In this final chapter we look at the key trends relating to spectrum usage and suggest where we think spectrum management will evolve in the coming decades.

Trends

Trends in usage

There are hundreds of different uses of the radio spectrum and trends and changes in many of these. However, where the users require relatively small amounts of spectrum, or spectrum for which there is little competition (e.g. satellite use of frequencies above 20 GHz) then these have limited impact on spectrum management approaches. Here we discuss what we believe are some of the most important trends relating to those uses that generate the highest economic value (broadly cellular and broadcasting), those that compete for the most congested spectrum and those where innovation might be most likely to occur. The trends are not presented in any particular order.

Trend 1: growing importance of unlicensed spectrum We are using Wi-Fi and Bluetooth ever more. Home Wi-Fi networks now routinely have tens of devices connected to them whereas a decade ago they might have had one or two. Monitoring devices are slowly appearing around the home, such as Wi-Fi-connected security devices, and many more are being shown at trade shows. Other systems, such as the home energy system, may make use of a separate network within the home to connect gas and electricity meters, in-home displays, and eventually smart appliances. Out of the home we are increasingly looking to log onto Wi-Fi hotspots wherever we find ourselves. Bluetooth accessories are proliferating, with many health- and fitness-oriented devices being developed for wearing and devices like Google Glass being tested. As this usage grows so will the possibilities of interference, while at the same time our tolerance for not being connected will fall. The use of 5 GHz spectrum will offer some relief but regulators may need to become more inclined towards making bands unlicensed than they are at present.

Introduction

In most countries a great deal of spectrum – roughly half – is used within the public sector. This applies both to all bands taken together and to the highest-value spectrum in the 300 MHz to 3 GHz range. The uses include applications for aviation and maritime transport, communications, radar, and science. Most of the spectrum use is defense-related.

The pattern of use across countries is not very sensitive to geographical location and income per head, so a similar division can be expected everywhere. It is also common for defense-related spectrum to account for more than half of public-sector spectrum use. Figure 12-1 shows the breakdown between commercial and public use of spectrum in a typical European country.

Historically, defense and, to a lesser extent, other public-sector uses of spectrum had priority over civilian uses. Often public-sector users were not subject to license requirements or to license fees in the same way as commercial users. In periods of spectrum plenty (i.e. before the recent growth of spectrum demand for communications services), the public sector was normally given generous assignments.

In the UK a study monitoring spectrum use found low levels of use of some public spectrum, including in the 1.0–1.8 GHz range, as contrasted with high levels of use in mobile bands – for example 900, 1800, 2300 MHz.

This says nothing about the value of such use. However, the observation both of low usage levels and of the lack of incentive for efficient use of public-sector spectrum which is described below does at least raise questions for further investigation.

This chapter draws heavily upon the broader analysis we have undertaken in previous chapters, notably of spectrum scarcity and its consequences (Chapter 3), of spectrum pricing and valuation (Chapter 7), and of spectrum sharing (Chapter 8). First we discuss how special attributes of the public sector affect spectrum use and spectrum management. Then we review a set of possible means to improve efficiency of spectrum use there.

The issues at stake

Territorial wars are seldom waged over infertile land, unless it has military or symbolic significance. The same is true of spectrum. Given the technologies available today, the most fertile spectrum lies below 3 GHz, and the very best of it is found in or just above the UHF TV band, which falls between 400 and 800 MHz.

This spectrum is particularly well suited both to terrestrial broadcasting and to mobile communications as a result of its propagation characteristics. At these frequencies radio signals travel many tens of kilometers, but equally receivers do not require antennas that are larger than handheld devices. In the case of broadcasting this allows most of a country to be served from a relatively small number of high-tower sites (e.g. around 100 for the entire UK). In the case of mobile communications the extended range is valuable both for covering rural areas and for achieving better in-building penetration than could be achieved at other frequencies.

In both cases, there are other options that can be used to enable service delivery. Broadcasting can be delivered using other spectrum bands or alternatively via non-spectrum inputs such as fibre-optic cables. TV distribution via satellite broadcasting uses spectrum in the 12 GHz range and this is much less valuable than the UHF band. Coaxial and fibre cables can be used to distribute TV content, which is increasingly the case in dense urban settings.

With regard to mobile communications there are many higher bands available – notably at 1,800 MHz, 2.1 GHz, 2.6 GHz and others. Voice and data services are also available for fixed and nomadic consumption by wireline technologies, combined with Wi-Fi final drop. But auction data show that the higher frequencies are much less valuable (see Chapter 5). Telecommunications regulators continue to regard (perhaps with decreasing conviction) fixed and mobile voice and data services as falling in different economic markets, because they are seen by users as being insufficiently substitutable for one to impose a constraint on the other.

Introduction

The most fundamental reason for managing radio spectrum is to avoid interference between users, or at least to ensure interference is manageable and optimizes the capacity of the radio spectrum. This chapter provides the background material necessary to understand how interference occurs and the mechanisms to mitigate its effects. This is fundamental to the understanding of the spectrum management discussions throughout the rest of this book.

The chapter broadly describes the characteristics of a radio signal, how it travels from a transmitter to a receiver, the ways that interference can occur in the receiver, and how these can be avoided using technology.

Transmitting a radio signal

Defining a radio signal

A radio signal is the emission of an electromagnetic wave from an antenna. Electromagnetic waves cover a broad range of frequencies, from radio waves up through visible light and beyond into X-rays. Radio waves are generally considered to be those where the frequencies range from around 10 kHz up to 300 GHz. They are formed when an electrical signal passes into any conductor that has the ability to radiate signals. Antennas are designed for this purpose, but cabling can be an unwanted radiator if not properly shielded, and even semiconductor chips tend to radiate unwanted signals.

Components of a signal: power, bandwidth, and mask

At its simplest a radio signal has three key components – power, bandwidth and frequency. The power is the amount of energy radiated from the antenna, typically measured in watts. The bandwidth is the width of the different frequency components of the signal, measured in hertz, and the center frequency is the frequency of the transmitter when not transmitting any information (said to be unmodulated), also measured in hertz. For example, a GSM handset might transmit 1 W of power at a center frequency of 900 MHz with a bandwidth of 200 kHz.

As might be expected, there are some subtleties in each of these parameters. The antenna used by a device can radiate energy equally in all directions (an “omnidirectional antenna”) or it can focus energy in one particular direction (a “directional antenna”). The former is like a light bulb in a room, the latter like a torch. The effect of a directional antenna is to increase the energy received in the direction of the beam and decrease it elsewhere.