Understanding the RF path - CommScope

[Pages:224]Understanding the RF path

TABLE OF CONTENTS

Chapter 1 Introduction: Welcome to RF communications 3 Chapter 2 The solutions, practices and trends: Cell site development 8 Chapter 3 Getting the signal across: Base station antennas 19 Chapter 4 Working within the limits: Co-siting solutions 44 Chapter 5 Talking and listening at the same time: Transmission and receiving isolation systems 59 Chapter 6 Getting from the air to the network: Cables and connectivity 76 Chapter 7 Clearing the connections: Overcoming passive intermodulation (PIM) 97 Chapter 8 Getting the most from every cycle: Spectrum management 105 Chapter 9 The infrastructure behind the call: Backhaul 115 Chapter 10 The next RF architecture evolution: C-RAN 137 Chapter 11 The energy of communications: Powering wireless networks 147 Chapter 12 Successfully planning against failure: Reliability in wireless systems 172 Chapter 13 Extending the network indoors: DAS, C-RAN antenna systems, and small cell solutions 187 Chapter 14 Finding safer ground: Lightning protection 196 Biographies 210 | Appendix A 214 | Glossary 219

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Introduction:

Welcome to RF communications Chapter 1

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Introduction:

Welcome to RF communications

For decades, CommScope has grown up alongside the science of communication with practical solutions. We have been dedicated to helping the world achieve more powerful, efficient and innovative ways to network information and people. We have partnered with leading networks all over the world to help them maximize opportunities and unlock hidden potential, because we believe in the power of innovative networks and those who build them.

To us, true partnership also includes sharing what we've learned along the way. The result is this book, which presents the fundamentals of radio frequency (RF) communications in a comprehensive, yet approachable, way.

Many different kinds of communication rely wholly or in part on RF technologies. The field is not limited to long-established applications like broadcast radio, shortwave and so forth--it also includes modern cellular communications such as 4G/LTE and emerging 5G

networks. It encompasses indoor wireless solutions that allow a mobile user to find a clear connection from anywhere in a vast building complex, aboard an aloft airliner or from a bullet train zipping through a tunnel under miles of granite. It even includes transmissions in the microwave bands, which, as you will learn, are an effective way to move vast amounts of data miles across a network without cable.

Indeed, as established a science as RF is, there remains incredible potential for new and innovative solutions that expand its reach and usefulness across every aspect of modern life. CommScope is dedicated to unlocking this potential.

The goal of this book is to explore the many dimensions of RF communications--past, present and future. It will also examine the technologies, solutions and practices that power the ongoing evolution of RF's role in the world, including many innovative technologies and practices that CommScope has brought to the industry. Some of this material is theoretical and technical, but every effort has been made to keep it as approachable as possible. Consider this RF Fundamentals 101.

Chapter 1

Microwave backhaul The use of microwave communications to aggregate and transmit cellular voice and data to and from the main network.

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1 | Introduction: Welcome to RF communications

RF systems, then and now

Wireless communication is a mature science. RF systems have been in commercial use since the 1940s, with the earliest examples including community repeaters, paging systems, point-to-point links and specialized mobile radio (trunked) systems.

More recent innovations and uses of the RF spectrum include the cellular radio networks we are all now familiar with. These applications originated in the 1980s and have evolved into a diverse and dynamic ecosystem of technologies, standards and architectures. Alongside these applications, other wireless technologies have become mainstream, even common features of everyday life--Wi-Fi, for example.

show how they interweave to create the fabric of modern communications. These systems include such components as:

Antennas, which are the structures where radio signals enter and exit the air

Coaxial copper cable, which features an inner and outer conductive layer for signals to travel

Fiber-optic cable, which uses pulses of light to transmit information efficiently

Filters, which prevent the intrusion of interfering signals from entering the RF path

The shared link These diverse applications all share one important characteristic: they all utilize a limited range of radio frequencies to move information between radio base locations and remote users.

The chain of components required to make this movement of information possible is complex and diverse. CommScope's wide range of solutions allows us to present a fairly comprehensive view of these systems, explain how they function and

Amplifiers, which increase signal transmission power to extend distance or improve signal quality

Enclosures, located at the base of a cell site, connected to remote radios and antennas at the top

Power backups, which ensure uninterrupted wireless service in the event of grid power failure

This is only a partial list, but this book will explore these and other components in the chapters ahead.

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1 | Introduction: Welcome to RF communications

RF communications: The early years

While the full story of RF communications continues to be written by a dynamic, growing industry, the current capabilities of modern RF technologies would almost certainly exceed the wildest dreams of the field's earliest pioneers. We take our connected world for granted, but the earliest commercial uses were not nearly so ubiquitous.

frequencies within its coverage area. Voice and data calls could be seamlessly "handed off" to neighboring cells as the user moved from one coverage area--or cell--to the next. The close-proximity reuse of radio channels is the fundamental concept of cellular telephones, and even today, it remains the reason why wireless networks can move vast amounts of traffic within a comparatively narrow band of RF spectrum.

The first RF systems featured a base radio using an omnidirectional antenna to communicate with one or more mobile users. Then, as now, the effective coverage radius of that base radio was limited by factors including RF power, antenna height, and the sensitivity of mobile receivers that were vulnerable to thermal noise and other interference sources. These systems were also limited by the fact that certain frequencies could only be used once in a particular geographical area. Once a mobile user left that area, no communication was possible.

The engineers of AT&T Bell Laboratories envisioned a future that would require much higher RF capacities to service thousands or millions of users at once. To deliver this future, they developed the cellular concept: a wireless network that uses lower antenna heights and transmission power levels to create limitedradius coverage areas that used and reused the same

The business case for technical expertise

Wireless service providers monitor key performance indicators within their territories to identify coverage problems and assure customer satisfaction. These indicators include quality of service (QoS), dropped calls, failed access attempts, and other criteria. Their engineers are on the front lines of this battle for quality and constantly optimizing network performance as traffic grows at an incredible rate.

Of the many ways an RF engineer can optimize a network, the first and most essential is to ensure a solid physical foundation of interoperating components across the RF path (Figure 1.1).

42% DATA TRAFFIC GROWTH

Data Tra c

2016 2017 2018 2019 2020 2021

42% data tra c CAGR growth each year through 2021, worldwide

SOURCE: Ericsson Mobility Report, June 2017

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1 | Introduction: Welcome to RF communications

Not only does this foundation provide the best scenario for efficient operation, it also helps minimize the likelihood of downtime, which is a disruptive and expensive proposition for the wireless service operator. For these reasons, it's vital for the RF engineer to understand the latest standards and specifications, and to choose components that meet or exceed those standards and specifications. It is an unfortunate fact in the wireless industry that not all solutions are built to meet the latest requirements--it is incumbent on the provider and the engineer to ensure compliant components are used in the RF path.

Understanding the RF path and the parts that make it operate efficiently is the journey this book will follow. CommScope is glad to have you join us for the trip. Let's visit the first stop along the way in the next chapter, where we will examine the makeup of a modern cell site.

Selfoptimizing networks Advanced fine

tuning

Hando parameters

Have a quality life experience while on the network

Stay on the network

Access parameters Physical layer -- RF path

Get on the network

Coverage design

1.1: The interconnection of technology, design and optimization

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The solutions, practices and trends:

Cell site development Chapter 2

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