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Disclaimer:
This book focuses on open standards for the wireless Internet of Things. This book only discusses Bluetooth, ZigBee, Thread, Z-Wave, and Wi-Fi in a nominative sense as they relate to those open standards. Neither this book nor the author is affiliated with any IoT industry groups.
Zigbee^® is a registered trademark of the Zigbee Alliance.
Bluetooth^® is a registered trademark of Bluetooth SIG, Inc.
Wi-Fi^® is a registered trademark of the Wi-Fi Alliance.
Thread^® is a registered trademark of the Thread Group, Inc.
Z-Wave^® is a registered trademark of Sigma Designs.

Library of Congress Cataloging-in-Publication Data:

ISBN: 9781119260578

Cover Design: Wiley
Cover Image: iStock.com/monsitj

CONTENTS

Preface

Acknowledgments

About the Author

1 Introduction

1.1 What is the Internet of Things?
1.2 What is the Wireless Internet of Things?
1.3 Wireless Networks
1.4 What is the Role of Wireless Standards in the Internet of Things?
1.5 Protocol Stacks
1.6 Introduction to the Protocols for the Wireless Internet of Things
1.7 The Approach of this Book
References

2 Protocols of the Wireless Internet of Things

2.1 Bluetooth
2.2 ITU G.9959
2.3 Z-Wave
2.4 IEEE 802.15.4
2.5 The ZigBee Specification
2.6 Thread
2.7 Wi-Fi
References

3 Radio Layer

3.1 The Wireless System
3.2 Basic Transceiver Model
3.3 The Basics of Channels
3.4 Bit and Symbol Error Rate
3.5 Complex Channels
References

4 Modem Layer

4.1 The Signal Model
4.2 Pulse Shaping
4.3 Modulation Techniques
4.4 Synchronization
4.5 Spread Spectrum
References

5 MAC Layer

5.1 Bands and Spectrum Planning
5.2 Spectrum Access for the Wireless IoT
5.3 Multiple Access Techniques
5.4 Spread Spectrum as Multiple Access
5.5 Error Detection and Correction
5.6 Energy Efficiency
References

6 Conclusion

6.1 Selecting the Right Standard
6.2 Higher Layer Standardization and the Future of IoT

Index

End User License Agreement

List of Illustrations

Chapter 1

Figure 1.1 The IoT Across Vertical and Horizontal Markets [5]
Figure 1.2 The IoT Application Areas and Wireless Connectivity [8]
Figure 1.3 Star Topology
Figure 1.4 Mesh Topology
Figure 1.5 WLAN and Gateway to WAN
Figure 1.6 Wireless PAN
Figure 1.7 Star Device Network
Figure 1.8 Mesh Device Network
Figure 1.9 Mesh Topology of a Device Network in eAgriculture [12]
Figure 1.10 Example Protocol Stack
Figure 1.11 Seven-Layer OSI Reference Model
Figure 1.12 TCP/IP with Routers
Figure 1.13 Mapping TCP/IP to OSI
Figure 1.14 The IEEE 802 Reference Model
Figure 1.15 The Relationship Between IEEE 802 Standards
Figure 1.16 Three-Layer Model for Wireless Sensor Networks
Figure 1.17 Simplified Protocol Stack

Chapter 2

Figure 2.1 Bluetooth v1.0 Protocol Stack [2]
Figure 2.2 Bluetooth v1.0 Lower Layers [2]
Figure 2.3 Bluetooth Device Architecture
Figure 2.4 Bluetooth LE Lower Layers
Figure 2.5 Bluetooth Topology [3]
Figure 2.6 Bluetooth Low Energy Mesh Topology [8]
Figure 2.7 Z-Wave Protocol Stack
Figure 2.8 Z-Wave Packet Layers [16]
Figure 2.9 IEEE 802.15.4 Protocol Stack [17]
Figure 2.10 802.15.4 Channel Plan [17]
Figure 2.11 IEEE 802.15.4 Packet Structure [17]
Figure 2.12 IEEE 802.15.4 Star and Peer-to-Peer Topologies [21]
Figure 2.13 IEEE 802.15.4 Cluster Tree Topology [21]
Figure 2.14 ZigBee Specification Protocol Stack [12]
Figure 2.15 Simplified ZigBee Specification Protocol Stack
Figure 2.16 Thread Protocol Stack Compared to TCP/IP Stack
Figure 2.17 IEEE 802.11 WLAN Stack
Figure 2.18 Overlapping Wi-Fi Channels [33]
Figure 2.19 Non-Overlapping Wi-Fi Channels [33]

Chapter 3

Figure 3.1 Traversing the Stack: The Radio Layer
Figure 3.2 Communication System Diagram
Figure 3.3 Transceiver Functional Block Diagram
Figure 3.4 Superheterodyne Receiver
Figure 3.5 Real-Mixing Images Frequencies
Figure 3.6 Image Frequency Example
Figure 3.7 Real-Valued ADC Bandwidth
Figure 3.8 Perfect Real-Valued Down-Conversion
Figure 3.9 Overlapping Bandwidths by Real-Valued Down-Conversion
Figure 3.10 Sampling at IF
Figure 3.11 Direct-Conversion Receiver
Figure 3.12 Complex-Valued Mixing
Figure 3.13 Complex-Valued ADC Bandwidth
Figure 3.14 IQ Imbalance Curves
Figure 3.15 Simplified Direct-Conversion Spectrum
Figure 3.16 Null at Center of OFDM Symbol
Figure 3.17 RF-Sampling Receiver
Figure 3.18 Digital Down-Converter Structure
Figure 3.19 DDC Operation
Figure 3.20 Digital Complex-Valued Mixing
Figure 3.21 Digital Up-Converter Structure
Figure 3.22 DUC Operation
Figure 3.23 Narrowband System
Figure 3.24 Bit Error Rate Curve for CPFSK h = 0.315
Figure 3.25 Link Budget Considerations for a Fading Channel [14]
Figure 3.26 Three-Ray Multipath Example
Figure 3.27 Three-Ray Multipath Example: Power Delay Profile
Figure 3.28 Combined Channel Model

Chapter 4

Figure 4.1 Traversing the Stack: The MODEM Layer
Figure 4.2 Spectrums of Real-Valued and Complex-Valued Signals
Figure 4.3 Distribution of Complex-Valued Noise Magnitude and Phase
Figure 4.4 Complex-Valued Noise Moving with Increasing CNR
Figure 4.5 Rician Distributed Signal
Figure 4.6 QPSK as a Rician Distributed Signal
Figure 4.7 The Combined Signal Model
Figure 4.8 Pulse Shaping: Square Bits
Figure 4.9 Nyquist ISI Criterion
Figure 4.10 Comparison of Roll Off Factors
Figure 4.11 Spectrum of Pulse-Shaped Bits
Figure 4.12 Gaussian Pulse-Shaping Filter
Figure 4.13 Symbol Mapping
Figure 4.14 Quadrature Modulator
Figure 4.15 BPSK Constellation
Figure 4.16 Phase Inversion of the Carrier using BPSK
Figure 4.17 Flowgraph for Differential Encoding and Decoding
Figure 4.18 QPSK Constellation
Figure 4.19 Conjugate Ambiguity
Figure 4.20 Matching DUCs and DDCs
Figure 4.21 π/4-QPSK
Figure 4.22 Block Diagram for the OQPSK Modulator
Figure 4.23 OQPSK Constellation
Figure 4.24 8PSK and 8DPSK Constellation
Figure 4.25 Frequency Modulation
Figure 4.26 Continuous Phase FSK
Figure 4.27 Inner and Outer Frequency Deviation
Figure 4.28 GFSK Modulation
Figure 4.29 Differential MSK by CPFSK
Figure 4.30 CPFSK MSK Modulator Output
Figure 4.31 802.15.4 OQPSK
Figure 4.32 IEEE 802.15.4 OQPSK Output
Figure 4.33 Correlation Demodulator
Figure 4.34 Arctan Demodulator
Figure 4.35 Arctan and Correlator Receiver BER Performance vs. Carrier Offset [10]
Figure 4.36 Cross-Differentiate-Multiplier FSK Demodulator
Figure 4.37 Sync Word in Data Packet
Figure 4.38 Seven-Bit Barker Code Autocorrelation
Figure 4.39 Recovering the Channel Impulse Response through Frame Synchronization
Figure 4.40 IEEE 802.15.4 Sync Word Autocorrelation
Figure 4.41 BPSK with Carrier and Symbol Timing Offset
Figure 4.42 BPSK with Symbol Timing Offset, Carrier Corrected
Figure 4.43 BPSK with Carrier Offset, Symbol Timing Corrected
Figure 4.44 BPSK Carrier and Symbol Timing Corrected
Figure 4.45 Projection onto Real-Axis due to Phase Offset
Figure 4.46 BPSK with Carrier Phase Offset
Figure 4.47 Basic PLL Structure
Figure 4.48 Sampling in Different Symbol Shapes
Figure 4.49 Optimal and Suboptimal Sampling Points
Figure 4.50 BPSK with Symbol Timing Offset
Figure 4.51 Basic Symbol Recovery Loop Structure
Figure 4.52 Symbol Recovery Loop from [16]
Figure 4.53 Interference within the Bandwidth of Interest
Figure 4.54 Frequency Hopping Around Interference
Figure 4.55 Frequency-Hopping Modulator
Figure 4.56 Example Frequency-Hopping Sequence
Figure 4.57 Spreading by Direct Sequence
Figure 4.58 DSSS Modulator
Figure 4.59 DSSS Signal with Interferer
Figure 4.60 32-Ary Example

Chapter 5

Figure 5.1 Traversing the Stack: The MAC Layer
Figure 5.2 2.4 GHz ISM Band Channel Mapping
Figure 5.3 Frequency Division Multiple Access
Figure 5.4 Time Division Multiple Access
Figure 5.5 Frequency Division Duplexing
Figure 5.6 Time Division Duplexing
Figure 5.7 Bluetooth Time Division Duplexing [7]
Figure 5.8 Contention Mitigation through CSMA
Figure 5.9 Collisions in CSMA System
Figure 5.10 Hidden and Exposed Node
Figure 5.11 CSMA/CA Message Diagram
Figure 5.12 IEEE 802.15.4 Beacon-Enabled MAC [9]
Figure 5.13 Multiple Access through Frequency Hopping
Figure 5.14 Matrix of 8-bit Words in Binary
Figure 5.15 Even Longitudinal Checksum
Figure 5.16 Odd Longitudinal Checksum
Figure 5.17 Detecting Bit Errors in Odd Longitudinal Checksum
Figure 5.18 (3,1) Repetition Code Distance
Figure 5.19 States of the Received Coded Bits
Figure 5.20 (3,1) Repetition Code, Implemented Sequentially
Figure 5.21 Generic Transceiver Sleep Mode Duty Cycle
Figure 5.22 Generic Transceiver Duty Cycle, Nodes Out Of Sync
Figure 5.23 Inactive Periods in Beacon-Enabled IEEE 802.15.4 Frame [9]
Figure 5.24 ITU G.9959 Beam and Wakeup Intervals

Chapter 6

Figure 6.1 Unified Protocol Stack, Lower Layers
Figure 6.2 Unified Protocol Stack, Lower Layers

Preface

While the current state of the IoT market is fragmented across manufacturers and product lines, the future of IoT lies in interoperability. This interoperability will be enabled and communicated through easy access to technology standards developed by the IEEE and others.

This book provides an overview of several wireless standards for connectivity in the Internet of Things (IoT) and then addresses relevant wireless communications theory to help elucidate those standards. The book details the lower layers of a protocol stack in describing the wireless IoT from the bottom-up. In doing so, the book decomposes the issues to be addressed into smaller subsets.

Chapter 1 introduces the concept of the wireless internet of things, detailing background information and giving a few examples of applications. Those applications drive the requirements for the wireless links that enable the wireless IoT. The book then introduces the concept of protocol stacks, such that the wireless links can be decomposed into layers with specific responsibilities. The book gives several examples of protocol stacks and the slight differences in functional decomposition across layers. The fact that the lower layers, physical and media access, are generally covered by independent standards bodies is addressed. This book then sets its scope on those lower layers used for link establishment, channel access, error detection, and modulation. This is done by following a unified lower layer model with three layers, radio, Modem, and Media Access Control.

Chapter 2 outlines physical and media access layers for several popular open wireless standards used by IoT applications. This book focuses on open standards defined by independent standards bodies. Several popular wireless IoT protocols are referenced in a nominative sense in order to link the open standards to applications with which the reader may be more familiar. Those popular protocols are Bluetooth (formerly IEEE 802.15.1), IEEE 802.15.4, and ITU G.9959. This book focuses on low-power wireless links for the IoT; however, this chapter also briefly discusses Wi-Fi as Wi-Fi is important to many IoT applications. Wi-Fi appears again in later chapters as Wi-Fi interacts with the standards identified. This chapter can be used as a quick reference guide for the various protocols. This chapter also introduces concepts that will be explored in the later chapters, and informs the reader as to where in the book more information on that topic can be found.

Chapter 3 is dedicated to the aforementioned Radio layer. Radio front-ends are explored in this chapter. There is a slant toward software-defined radio implementations of IoT protocols, but multiple radio hardware topologies are explored. This chapter reviews the concept of link budgets and goes through examples. This chapter also addresses complex channel models employing both large and small-scale fading.

Chapter 4 focuses on the MODEM. This chapter covers the concepts of the complex-envelope signal model, modulation, demodulation, synchronization, and spread spectrum. Linear and angular modulation schemes as used in the identified open standards are explored, both in terms of background theory and also as to why a particular standard would choose a particular modulation scheme. Synchronization techniques for carrier and symbol recovery are discussed. The chapter ends with a discussion on the various spread spectrum techniques employed in the physical layers of the wireless IoT.

Chapter 5 describes the Media Access Control layer. Channel access schemes commonly employed by the wireless IoT standards, such as CSMA, are detailed. The chapter describes the different bands used by the wireless IoT standards. In particular, the 2.4 GHz Industrial, Scientific, and Medical band, and the congestion therein, is detailed. The chapter describes various interference and interference mitigation techniques employed in wireless IoT standards. The chapter concludes with a discussion on error correction and detection.

A recurring theme in this book has been that no one book can cover all of wireless system design. There are many books relevant to this course of study, on topics ranging from antenna design to symbol synchronization. This book provides background material in relevant theory, analysis of design choices, and numerous citations to aid the reader interested in learning more on a given subject. Each of the chapters in this book provides a list of references such that the interested reader can research the topic in more detail than can be covered in this limited scope.

It is the hope of the author that this book is useful to a variety of readers. Developers of platforms and applications of IoT will benefit from this book that provides a practical survey of standards relevant to the lightweight and low-cost needs of IoT platforms. This book will be useful for a variety of engineers involved in Digital Signal Processing (DSP), network implementation, and wireless communication, but could also be useful to the entrepreneur or hobbyist looking to understand the technology and develop the next big Thing.

Daniel Chew

Giancarlo Fortino	Andreas Molisch	Linda Shafer
David Alan Grier	Saeid Nahavandi	Mohammad Shahidehpour
Donald Heirman	Ray Perez	Sarah Spurgeon
Xiaoou Li	Jeffrey Reed	Ahmet Murat Tekalp

TheWireless Internet of Things

A Guide to the Lower Layers

Preface

Acknowledgments

About the Author