Tse and Viswanath:Fundamentals of Wireless Communication 10 of each chapter provide pointers to literature that is very closely related to the material discussed in the book;we do not aim to exhaust the immense research literature related to the material covered here
Tse and Viswanath: Fundamentals of Wireless Communication 10 of each chapter provide pointers to literature that is very closely related to the material discussed in the book; we do not aim to exhaust the immense research literature related to the material covered here
Tse and Viswanath:Fundamentals of Wireless Communication Acknowledgements We would like to first thank the students in our research groups for the selfless d.In particular,many thanks to:Sanket Dusad.Rad op who bet en them painstakingly produced most of the figures in the andar drew quitea fe figures and proofread som chapters Ada Poon whose research shaped significantly the material in Chapter 7 and who drew several figures in that chapter as well as in Chapter 2;Saurabha Tavildar and Lizhong Zheng whose research led to Chapter 9:Tie Liu and Vinod Prabhakaran for their help in clarifying and improving the presentation of Costa precoding in Chapter 10. Several researchers read drafts of the book carefully and provided us with very of the book. k D ap ·Atilla e ilmaz,Irem Koprul ana Porrat and Pascal Vonte obel.This book ha also benefite immensely from critical comments from students who have taken our wireless commu- nications courses at Berkeley and Urbana-Champaign.In particular,sincere thanks to Amir Salman Avestimehr,Alex Dimakis,Krishnan Eswaran,Jana van Greunen. Nils Hoven,Shridhar Mubaraq Mishra,Jonathan Tsao,Aaron Wagner,Hua Wang. Xinzhou Wu and Xue Yang Earlier of this ok hav e been used in teaching course at several univ sities: Il,ETHZ,MIT,Northwestern and Universit of Colorado at Boulde We would like to thank the instructors for their feedback:Helmut Bolcskei, Anna Scaglione,Mahesh Varanasi,Gregory Wornell and Lizhong Zheng.We would like to thank Ateet Kapur,Christian Peel and Ulrich Schuster from Helmut's group for their very useful feedback.Thanks are also due to Mitchell Trott for explaining to us how the arr system work This book ntains the re y researchers,but it owe s an intellectual debt to two individuals in particular.Bob Gallager's research and teaching style have greatly inspired our writing of this book.He has taught us that good theory,by providing a unified and conceptually simple understanding of a morass of results,should shrink rather than grow the knowledge tree.This book is an attempt to implement this dictum.Our many discussions with Rajiv Laroia have significantly influenced our view of the system aspects of ications.Seve ral of his ideas have found their way into the" em view discussions in the book Finally we would like to thank the National Science Foundation,whose continued support of our research led to this book
Tse and Viswanath: Fundamentals of Wireless Communication 11 Acknowledgements We would like to first thank the students in our research groups for the selfless help they provided. In particular, many thanks to: Sanket Dusad, Ra´ul Etkin and Lenny Grokop who between them painstakingly produced most of the figures in the book; Aleksandar Joviˇci´c who drew quite a few figures and proofread some chapters; Ada Poon whose research shaped significantly the material in Chapter 7 and who drew several figures in that chapter as well as in Chapter 2; Saurabha Tavildar and Lizhong Zheng whose research led to Chapter 9; Tie Liu and Vinod Prabhakaran for their help in clarifying and improving the presentation of Costa precoding in Chapter 10. Several researchers read drafts of the book carefully and provided us with very useful comments on various chapters of the book: thanks to Stark Draper, Atilla Eryilmaz, Irem Koprulu, Dana Porrat and Pascal Vontobel. This book has also benefited immensely from critical comments from students who have taken our wireless communications courses at Berkeley and Urbana-Champaign. In particular, sincere thanks to Amir Salman Avestimehr, Alex Dimakis, Krishnan Eswaran, Jana van Greunen, Nils Hoven, Shridhar Mubaraq Mishra, Jonathan Tsao, Aaron Wagner, Hua Wang, Xinzhou Wu and Xue Yang. Earlier drafts of this book have been used in teaching courses at several universities: Cornell, ETHZ, MIT, Northwestern and University of Colorado at Boulder. We would like to thank the instructors for their feedback: Helmut B¨olcskei, Anna Scaglione, Mahesh Varanasi, Gregory Wornell and Lizhong Zheng. We would like to thank Ateet Kapur, Christian Peel and Ulrich Schuster from Helmut’s group for their very useful feedback. Thanks are also due to Mitchell Trott for explaining to us how the Arraycomm systems work. This book contains the results of many researchers, but it owes an intellectual debt to two individuals in particular. Bob Gallager’s research and teaching style have greatly inspired our writing of this book. He has taught us that good theory, by providing a unified and conceptually simple understanding of a morass of results, should shrink rather than grow the knowledge tree. This book is an attempt to implement this dictum. Our many discussions with Rajiv Laroia have significantly influenced our view of the system aspects of wireless communications. Several of his ideas have found their way into the “system view” discussions in the book. Finally we would like to thank the National Science Foundation, whose continued support of our research led to this book
Chapter 1 Introduction 1.1 Book Objective Wireless ommunication is one of the most vibrant areas in the communication field today.While it has been a topic of study since the 1960's,the past decade has seen a surge of research activities in the area.This is due to a confluence of several factors First is the explosive increase in demand for tetherless connectivity,driven so far mainly by cellular telephony but is expected to be soon eclipsed by wireless data applications.Second,the dramatic progress in VLSI technology has enabled small-area and low-power implementation of sop histicated signal processing algorithms and coding Third the 0n(2G digita wire s standard in particular,the IS-95 Code Division Multiple Access(CDMA)standard,provides a concrete demonstration that good ideas from communication theory can have a significant impact in practice.The research thrust in the past decade has led to a much richer set of perspectives and tools on how to communicate over wireless channels,and the picture is still very much evolving There are two fun ts of wireless communication that make the lem challenging and ting. These aspects are and large not as significant wireline communication.First is the phenomenon of fading:the time-variation of the channel strengths due to the small-scale effect of multipath fading,as well as larger scale effects such as path loss via distance attenuation and shadowing by obstacles Second,unlike in the wired world where each transmitter-receiver pair can often be thought of as an isolated point-to-point link,wireless users communicate over the air and there is sig ant interferen communica tion The interference can be between transmitters communicating with a common receiver e.8 uplink of a cellular system),between signals from a single transmitter to multiple re ceivers (e.g.downlink of a cellular system),or between different transmitter-receiver pairs (e.g.interference between users in different cells).How to deal with fading and with interference is central to the design of wireless communication systems,and will
Chapter 1 Introduction 1.1 Book Objective Wireless communication is one of the most vibrant areas in the communication field today. While it has been a topic of study since the 1960’s, the past decade has seen a surge of research activities in the area. This is due to a confluence of several factors. First is the explosive increase in demand for tetherless connectivity, driven so far mainly by cellular telephony but is expected to be soon eclipsed by wireless data applications. Second, the dramatic progress in VLSI technology has enabled small-area and low-power implementation of sophisticated signal processing algorithms and coding techniques. Third, the success of second-generation (2G) digital wireless standards, in particular, the IS-95 Code Division Multiple Access (CDMA) standard, provides a concrete demonstration that good ideas from communication theory can have a significant impact in practice. The research thrust in the past decade has led to a much richer set of perspectives and tools on how to communicate over wireless channels, and the picture is still very much evolving. There are two fundamental aspects of wireless communication that make the problem challenging and interesting. These aspects are by and large not as significant in wireline communication. First is the phenomenon of fading: the time-variation of the channel strengths due to the small-scale effect of multipath fading, as well as larger scale effects such as path loss via distance attenuation and shadowing by obstacles. Second, unlike in the wired world where each transmitter-receiver pair can often be thought of as an isolated point-to-point link, wireless users communicate over the air and there is significant interference between them in wireless communication. The interference can be between transmitters communicating with a common receiver (e.g. uplink of a cellular system), between signals from a single transmitter to multiple receivers (e.g. downlink of a cellular system), or between different transmitter-receiver pairs (e.g. interference between users in different cells). How to deal with fading and with interference is central to the design of wireless communication systems, and will 12
Tse and Viswanath:Fundamentals of Wireless Communication 13 be the central themes of this book.Although this book takes a physical-layer per- spective,it will be seen that in fact the management of fading and interference has ramifications across multiple lavers. Traditionally the design of wireless systems has been focused on increasing the reliability of the air interface in this nd interference are nuisances tha e viewed a are to be countered crea the spectmal efficiency;associated with this shift is a new point of view that fading can be viewed as an opportunity to be exploited.The main objective of the book is to provide a unified treatment of wireless communication from both these points of view.In addition to traditional topics such as diversity and interference averaging a substantial portion of the book will be devoted to more modern topics suc opportunistic and multi-input multi An important component of this book is the system view emphasis:the successful implementation of a theoretical concept or a technique requires an understanding of how it interacts with the wireless system as a whole.Unlike the derivation of a concept or a technique,this system view is less malleable to mathematical formulations and is primarily acquired through experience with designing actual wireless systems.we try to help the reader develop s ome of this intuition by giving numero examples of how the concepts are applied in actual wireless systems.Five of wireles systems are used. The next section gives some sense of the scope of the wireless systems considered in this book. 1.2 Wireless Systems Wireless communication,despite the hype of the popular press,is a field that has been around for over a hundred years,starting around 1897 with Marconi's successful demonstrations of wireless telegraphy.By 1901,radio reception across the Atlantic Ocean had been established;thus rapid progress in technology has also been around for quite a while In the intervening hundred years,many types of wireless systems flourished,and often late ed.Fo levision in its earlyda s,was broadcast by wireles adi ters, being replaced by cable transmissi n.Similarly,the point to point m crowave circuit that formed the backbone of the telephone network are being replaced by optical fiber In the first example,wireless technology became outdated when a wired distribution network was installed:in the second.a new wired technology (optical fiber)replaced the older technology The site type of o in tele where 411 is par t of th wired telephor network(particularly in parts of the world where the wired network is not we ll devel oped).The point of these examples is that there are many situations in which there is a choice between wireless and wire technologies.and the choice often changes when
Tse and Viswanath: Fundamentals of Wireless Communication 13 be the central themes of this book. Although this book takes a physical-layer perspective, it will be seen that in fact the management of fading and interference has ramifications across multiple layers. Traditionally the design of wireless systems has been focused on increasing the reliability of the air interface; in this context, fading and interference are viewed as nuisances that are to be countered. Recent focus has shifted more towards increasing the spectral efficiency; associated with this shift is a new point of view that fading can be viewed as an opportunity to be exploited. The main objective of the book is to provide a unified treatment of wireless communication from both these points of view. In addition to traditional topics such as diversity and interference averaging, a substantial portion of the book will be devoted to more modern topics such as opportunistic and multi-input multi-output (MIMO) communication. An important component of this book is the system view emphasis: the successful implementation of a theoretical concept or a technique requires an understanding of how it interacts with the wireless system as a whole. Unlike the derivation of a concept or a technique, this system view is less malleable to mathematical formulations and is primarily acquired through experience with designing actual wireless systems. We try to help the reader develop some of this intuition by giving numerous examples of how the concepts are applied in actual wireless systems. Five examples of wireless systems are used. The next section gives some sense of the scope of the wireless systems considered in this book. 1.2 Wireless Systems Wireless communication, despite the hype of the popular press, is a field that has been around for over a hundred years, starting around 1897 with Marconi’s successful demonstrations of wireless telegraphy. By 1901, radio reception across the Atlantic Ocean had been established; thus rapid progress in technology has also been around for quite a while. In the intervening hundred years, many types of wireless systems have flourished, and often later disappeared. For example, television transmission, in its early days, was broadcast by wireless radio transmitters, which is increasingly being replaced by cable transmission. Similarly, the point to point microwave circuits that formed the backbone of the telephone network are being replaced by optical fiber. In the first example, wireless technology became outdated when a wired distribution network was installed; in the second, a new wired technology (optical fiber) replaced the older technology. The opposite type of example is occurring today in telephony, where wireless (cellular) technology is partially replacing the use of the wired telephone network (particularly in parts of the world where the wired network is not well developed). The point of these examples is that there are many situations in which there is a choice between wireless and wire technologies, and the choice often changes when
Tse and Viswanath:Fundamentals of Wireless Communication 14 new technologies become available. In this book,we will concentrate on cellular networks,both because they are of t current cellular networks.A cellular network consists of a large number of wireless subscribers who have cellular telephones (users).that can be used in cars.in buildings.on the street,or almost anywhere.There are also a number of fixed base stations,arranged to provide coverage of the subscribers. The area covered by a base station.ie..the area from which incoming calls reach that base station,is called a cell.One often pictures a cell as a hexagonal region with the base station in the middle. One then pictures a city or region as being broker up into a hexagonal lattice of cells (see Figure 1.2a).In reality,the base stations are placed somewhat irregularly,depending on the location of places such as building tops or hill tops that have good communication coverage and that can be leased or bought (see Figure 1.2b).Similarly,mobile users connected to a base station are chosen by good communication paths rather than geographic distance. a b hie eac cell ibeaonal Part (b):a more ealistic Figure 1.1:Cells and Base stations for a cellular network When a user makes a call,it is connected to the base station to which it appears to have the best path (often but not always the closest base station).The base stations in a given area are then connected to a mobile telephone switching office(MTSO,also )by high speed vire connection 0 links.Th MTSO is connected to the public wired telephone network microwa Thus an in coming call from a mobile user is first connected to a base station and from there to the MTSO and then to the wired network.From there the call goes to its destination, which might be an ordinary wire line telephone,or might be another mobile subscriber Thus,we see that a cellular network is not an independent network,but rather an ap- pendage to the wired network.The MTSO also plays a major role in coordinating
Tse and Viswanath: Fundamentals of Wireless Communication 14 new technologies become available. In this book, we will concentrate on cellular networks, both because they are of great current interest and also because the features of many other wireless systems can be easily understood as special cases or simple generalizations of the features of cellular networks. A cellular network consists of a large number of wireless subscribers who have cellular telephones (users), that can be used in cars, in buildings, on the street, or almost anywhere. There are also a number of fixed base stations, arranged to provide coverage of the subscribers. The area covered by a base station, i.e., the area from which incoming calls reach that base station, is called a cell. One often pictures a cell as a hexagonal region with the base station in the middle. One then pictures a city or region as being broken up into a hexagonal lattice of cells (see Figure 1.2a). In reality, the base stations are placed somewhat irregularly, depending on the location of places such as building tops or hill tops that have good communication coverage and that can be leased or bought (see Figure 1.2b). Similarly, mobile users connected to a base station are chosen by good communication paths rather than geographic distance. ✔ ✔ ❚ ❚ ❚ ❚ ✔ ✔ ❚ ❚ ✔ ✔ ✔ ✔ ❚ ❚ ✔ ✔ ❚ ❚ ❚ ❚ ✔ ✔ t t t t t t t t ✥✥✥✥ ❵❵ ✓ ✓ ✓ r r r r✏✏ r ✘✘✘✘r PPPr ❍❍ r ✘✘✘r ✘r ✘✘✁ ✁ r ✄ ✄ ✄ ✄r (a) (b) Part (a): an oversimplified view in which each cell is hexagonal. Part (b): a more realistic case where base stations are irregularly placed and cell phones choose the best base station Figure 1.1: Cells and Base stations for a cellular network When a user makes a call, it is connected to the base station to which it appears to have the best path (often but not always the closest base station). The base stations in a given area are then connected to a mobile telephone switching office (MTSO, also called a mobile switching center MSC) by high speed wire connections or microwave links. The MTSO is connected to the public wired telephone network. Thus an incoming call from a mobile user is first connected to a base station and from there to the MTSO and then to the wired network. From there the call goes to its destination, which might be an ordinary wire line telephone, or might be another mobile subscriber. Thus, we see that a cellular network is not an independent network, but rather an appendage to the wired network. The MTSO also plays a major role in coordinating