As a supplement to other books on wireless connectivity that deal with the detail of analysis and design of specific technologies.
Acknowledgments
Even when a book has a single author, a large part of the authorship goes to the colleagues, friends, and family that provided inspiration, criticism, a gentle push when things looked impossible and a reminder that Sisyphus was only a mythical creature.
I am deeply grateful to Osvaldo Simeone (King's College London) for enormous support during the preparation of this book. The credit for the idea of using cartoons should go to him. He could absolutely always find the time to read the chapters that I was asking him to check, and provide prompt and rich feedback. I have been fortunate to have him, an exemplary erudite researcher, as a collaborator over many years.
Three people stood out in encouraging me throughout the long writing of the book. Jørgen Bach Andersen (Aalborg University), Angel Lozano (Pompeu Fabra University) and Hiroyuki Yomo (Kansai University). Jørgen provided me with very valuable feedback on Chapter 10 (Space in Wireless Communications). Angel removed my doubts about the usefulness of Chapter 9 (Time and Frequency in Wireless Communications). Hiroyuki decided to use this as a textbook in the early stages, when I presented him with the book concept.
I am very thankful for the feedback I got on specific chapters. Two members of my research group provided me with feedback in the early stage of writing and removed some of the doubts I had about the style. Čedomir Stefanović (Aalborg University) read the first chapters and Nuno Pratas (now with Nokia) read Chapter 6 (A Mathematical View on a Communication Channel). Anna Scaglione (Arizona State University), Emil Björnson (Linköping University) and Elisabeth de Carvalho (Aalborg University) were very kind to read Chapter 11 (Using Two, More, or a Massive Number of Antennas) and provide me with prompt and useful feedback.
A big thank you goes to the members of my research group, who had to be patient with my rants about the book throughout all these years. After one of my lectures for the master students, Rocco Di Taranto (now with Ericsson), at that time my PhD student, asked me: “Where can I read these topics explained in a way in which you did it at the lecture?”. The book idea had been cooking in the background for some time, but this was perhaps the decisive push to write it. Marko Angjelichinoski (now with Duke University) was convinced that the style and the whole book project were very original and I needed to hurry up. I would like to thank Kasper Fløe Trillingsgaard (now with InCommodities) for many stimulating discussion on the information-theoretic aspects. Alexandru-Sabin Bana (Aalborg University) and Radoslaw Kotaba (Aalborg University) helped to prepare a course based on this book and spotted several errors and inconsistencies. While this book was in the final stages, I was teaching a course at Aalborg University and several students were kind to correct errors in the chapters: Andreas Engelsen Fink, Jonas Ingerslev Christensen, Taus Mortensen Raunholt, Jeppe Thiellesen and Simon Kallehauge.
The cartoons, the cover page, as well as the clipart used to make the figures, were made by Peter Gregson Studio from Novi Sad, Serbia. This is a team of immensely creative people, Jovan Trkulja, Velimir Andrejević and Milan Letić, whose ideas play a significant role in the final look of the book. I would also like to thank Aleksandar Sotirovski for making the first version of the cartoons for some of the chapters, but due to objective reasons could not continue. Thanks to Kashif Mahmood (Telenor) for suggesting Umer as a Pakistani name starting with “U”. I would also like to thank the team at Wiley for being patient and supportive throughout the years, but especially in the final stage: Sandra Grayson, Louis Manoharan, Adalfin Jayasingh, and Tessa Edmonds.
My biggest support through these years came from my family: my wife Iskra, my children Andrej and Erina, as well as our extended family. Family was always there to take the blame when I was performing poorly on time management and planning of the writing. In its most severe form, that blame was ending with a threat that I was going to write something similar to the dedication written by a mathematician, who dedicates his book to his wife and children “without whom this book would have been completed two years earlier”. I am obviously not doing it and, instead, I want to thank them for absolutely always being there for me. I am hoping that some of them will read the book and get to know what I am actually working with. Unfortunately, my father passed away before this book was finished. I am dedicating this book to him.
P. P.
1 An Easy Introduction to the Shared Wireless Medium
We start by describing wireless communication through an analogy with a conversation within a group of people, named Zoya, Yoshi, and Xia. We will refer to these and some other characters throughout the book; the characters will stand for wireless devices, base stations, or similar. The data that they want to communicate to each other is the content of their speech, which is part of the conversation. Regardless of the speech content, the conversation can only take place if the participants follow some conversation protocol, such that at a given time only one person speaks while the others listen. How do they agree who gets to speak and who gets to listen? One way would be, before starting the actual conversation, to have them agree upon which conversation protocol should be followed. In that case the information exchanged in that preliminary conversation cannot be regarded as useful data, but rather as metadata, also called protocol information or control information. The metadata is necessary in order to enable the conversation to take place. But then, how do they agree on the protocol for exchanging the metadata?
These questions can go on to infinity, but in a normal situation the communication protocol is agreed upon by either sticking to certain rules of politeness or following visual cues and gestures that facilitate the conversation. In other words, the metadata is exchanged by using a visual communication channel that is different from the speech communication channel. However, in a commonly encountered wireless communication system there is only one communication channel through which both the data and the metadata should be sent. This is not to say that it is not possible to have one wireless communication channel for data and a separate one for metadata; even if such separation exists, then what is the protocol for exchanging the meta-metadata that is used to agree how to send the metadata?
This gets obviously complicated, but the bottom line is that we will always hit the problem of communicating over a single shared wireless channel. Now, taking the fact that there is a single channel for communicating both the data and the metadata, the key point of the analogy with the conversation is to put Zoya, Yoshi, and Xia in a dark room, such that they have only speech as a means of communicating (we exclude tactile communication) and no visual cues can be of help. In that setting, the audio channel should be used both to coordinate the conversation and to carry the actual content of the conversation.
This is the common situation in which wireless communication systems operate and will be the subject of this chapter. Here are some examples of the questions that will be discussed. If Zoya and Yoshi want to talk to each other, how do they agree who talks first and who listens first? If both Xia and Yoshi want to talk to Zoya, how should they agree who takes a turn to speak at a given time, so that they don't all talk simultaneously? Solutions to these problems are provided by various protocols for controlling the access to the medium; hence the name MAC (medium access control) protocols, and they are of central importance in wireless communication systems.
1.1 How to Build a Simple Model for Wireless Communication
1.1.1 Which Features We Want from the Model
The main