Radio Resource Management For Wireless Networks

by Jens Zander, Seong-Lyun Kim

Overview

Providing a unified approach to radio resource management, this work offers a comprehensive understanding of the interrelationship between important RRM factors such as power control, channel allocation and link performance to aid in the design of more efficient wireless systems.

Product Details

ISBN-13:	9781580531467
Publisher:	Artech House, Incorporated
Publication date:	03/31/2001
Series:	Mobile Communications Series
Edition description:	BK&CD-ROM
Pages:	396
Product dimensions:	6.00(w) x 9.00(h) x 1.00(d)

About the Author

Magnus Almgren is a Senior Specialist in Radio Resource Allocation at Ericsson. He holds several patents and has published several papers in the field. The field of work has been in both GSM, TDMA as in 3G. He holds an M S degree in Electrical Engineering.

Olav Queseth is currently pursuing a Ph.D. degree at the Royal Institute of Technology in Stockholm. Previously he worked as a system engineer designing systems for operation and maintenance of telecommunication equipment. He received his M.S. in computer engineering from Chalmers University, Gothenburg, Sweden in 1994.

Jens Zander is a professor and head of the Radio Communication Systems Laboratory at the Royal Institute of Technology (KTH) in Stockholm, Sweden. Dr. Zander has published numerous papers on the resource management aspects of personal communication systems. He holds a M.S. and Ph.D. in electrical engineering from Linköping University, Linköping, Sweden.

Seong-Lyun Kim is an assistant professor at the Royal Institute of Technology (KTH) in Stockholm, Sweden. Dr. Kim's main research field includes power control, rate control/scheduling, and economic models for wireless infrastructure. He holds a B.S. degree in economics from Seoul National University, and M.S. and Ph.D. degrees in operations research from Korea Advanced Institute of Science and Technology (KAIST).

Read an Excerpt

1: Introduction

1.1 Historical Perspective on Radio Resource Management

The insight that energy could be transported without wires dates back to the late 19th century. As J. C. Maxwell predicted in the 1850s, Heinrich Hertz managed in 1888 to demonstrate that his 600 MHz transmitter was capable of producing a spark in his simple receiver a few meters away in his laboratory. It was, however, the Italian engineer Guillermo Marconi who first was able to make practical and commercial use of the "Hertzian wave" phenomenon in the field of communication. After the first experiments on his father's estate in 1895, his wireless devices became a commercial success, eventually making Marconi the first (but not last!) millionaire in the wireless business. From bridging a few hundred meters in his first stumbling tries, he managed to communicate across the Atlantic Ocean between Cornwall and Cape Cod, Massachusetts in 1901. In the decades to follow, wireless communications became an essential technology onboard ships. The early 1920s saw the advent of radio broadcasting, bringing wireless receivers into every home. What happened later is all well known to most of us who have seen wireless mass market successes such as TV-broadcasting, world-wide short-wave communication, satellite communications, and now in the recent decades, mobile telephony.

From an engineering perspective, the developers of wireless systems have, over time, been struggling with different fundamental design bottlenecks, or key problems, each typical to their respective phase of development. The removal of one bottleneck pushed development a quantum leap forward, just to face another bottleneck. In the following we will briefly review these key problems.

Key Problem I: Path Loss-The Early Days

Wireless telegraphy became widespread in the early years of the 20th century. Receivers in those days were passive devices, mainly consisting of a simple tuned circuit (i.e., a bandpass filter tuned to the dominant frequency of the transmissions). The consequence of this design was that all the energy at the receiver output (to create a sound in an earphone or to energize and electro-magnet to pull a pen onto a strip of paper) had to be generated at the transmitter. The loss of energy over a wireless connection, the path loss, is very large, in particular over large distances. The consequence was that large and bulky transmitters, capable of radiating an enormous amount of power were dominating the scene in the early years. Needless to say, this fact severely limited the use of mobile wireless communication, except on larger ships. The advent of the electron tube amplifier (de Forest, 1915) solved this problem. Now, receivers could be equipped with amplifiers with, in principle, any amount of amplification, which could completely compensate for the path loss. This took radio into the era of radio broadcasting which spread rapidly in the 1920s. The word "radio" became synonymous with radio broadcasting to the man on the street. Within a few decades there was a radio receiver in virtually every household in the Western World. Following the early successes, sound broadcasting was followed by TV broadcasting. In the United States this occurred in the 1930s, but elsewhere, commercial success of TV had to wait for the 1950s. Wireless communication played an important role in World War II and immediately after the war, two crucial inventions revolutionized our view on wireless communication. The first was the invention of the transistor. Intended as a tube-replacement to create lightweight, low-power, and portable radios, the transistor became synonymous with the small pocket broadcast receiver in the 1950s and 1960s. In the meantime, communication engineers became increasingly aware of the next bottleneck, thermal noise.

Key Problem ll: Thermal Noise

The unavoidable thermal noise, caused by the "Brownian dance" of electrons in all materials and electronic components, provided a new challenge of a different nature. No matter how much the received signals are amplified, the noise will also be amplified with them. The second key invention in the late 1940s, was the recognition of the fact that there were fundamental limits to the amount of information and the quality of reception imposed by this noise.

The trend-setting work of Claude E. Shannon, as manifested in his "A mathematical theory on communication," published in 1949, foreboded the advent of digital communications. Although not very practical at the time, the advent of the Large Scale Integrated (LSI) circuits and Digital Signal Processing (DSP) devices in the 1970s and 1980s have made it possible to push the performance of today's wireless communication systems very close to Shannon's limits. The most remarkable achievements made possible by this new way of thinking are probably the communication with satellites and deep space probes, as well as digital mobile telephones. The latter manage to maintain acceptable voice quality in the most adverse environments, such as in moving cars or even indoors.

With these new techniques, engineers have been quite successful in pushing the performance close to the constraints manifested in the laws of physics and the thermal noise. In the 1930s another fundamental problem became evident, the limited radio spectrum.

Key Problem III: The Limited Spectrum

Although this is touched upon by Shannon (bandlimited channels), it is clear that this is not entirely a technical problem. Since there is only one "ether," it is obvious that extensive and concurrent use of the same natural resource will inevitably lead to conflicts, in this case (unwanted) interference between different users. This is clear to anyone who has tried to receive a radio program on the medium wave (AM) band in the night. Hundreds of radio stations compete for the attention of the listener and in most cases the mutual interference is devastating. Since it would be possible to properly receive most of these stations if they were "alone," we see that the problem is something outside the "struggle" against nature discussed above. Rather, this problem, as with all resource sharing problems, has a social dimension. This was recognized already in the early years of radio, when the sharing of the frequency spectrum was given an administrative solution.

The International Telecommunication Union (ITU) was formed just after World War II, mainly to deal with these problems. A concept that has been in use for spectrum resource sharing since the advent of radio communication has been frequency multiplexing. The available spectrum is split into frequency bands and since early modulation schemes produced narrow-band signals, this was an excellent way to separate different users of the spectrum and to avoid unintended interference. Within the framework of the ITU, the countries of the world have taken it on to closely regulate the use of the frequency spectrum...

Table of Contents

	Preface	xi
1	Introduction	1
1.1	Historical Perspective on Radio Resource Management	1
1.2	Fundamental Problems in Wireless Networks	6
	References	10
2	Link Performance in Interference Channels	11
2.1	A Review of Multi-User Access in Mobile Communication Systems	11
2.1.1	Introduction and Problem Formulation	11
2.1.2	Signal Design in Multi-User Systems	14
2.1.3	Basic Orthogonal Multiplex Schemes	24
2.1.4	Spread-Spectrum and Nonorthogonal Multiplexing	30
2.2	Link Performance Models	43
	Problems	48
	References	50
3	Wireless Network Models	53
3.1	The Resource Management Problem	53
3.2	Quality-of-Service Models and User Behavior	61
	Problems	66
	References	67
4	Principles of Cellular Systems	69
4.1	Frequency Reuse	69
4.2	Static Channel Allocation and Simple Capacity Analysis	74
4.3	Traffic-Based Capacity Analysis	80
4.4	Outage-Based Capacity Analysis	86
4.4.1	Interference Outage	86
4.4.2	Analytical Approach	88
4.4.3	Simulation Approach	96
4.5	Directional Antennas and Sectorization	107
	Problems	115
	References	120
5	Handover and Mobility	121
5.1	Mobility Management Fundamentals	121
5.2	Handover Decision Algorithms	124
5.3	Handover Resource Management	138
	Problems	146
	References	148
6	Transmitter Power Control	151
6.1	Introduction	151
6.2	SIR Balancing	155
6.3	Distributed Power Control	163
6.3.1	Iterative Method	163
6.3.2	Convergence of the Iterative Method	166
6.3.3	Convergence Speed of the Iterative Method	166
6.3.4	Standard Interference Function	170
6.3.5	Constrained Power Control	171
6.3.6	Distributed SIR Balancing	172
6.4	Transmitter Removal	173
6.5	Dynamic Behavior of Power Control	174
6.6	Multirate Power Control	175
	Problems	182
	References	184
7	Dynamic Channel Allocation	187
7.1	Introduction	187
7.2	Traffic Adaptive Channel Allocation	192
7.3	Reuse Partitioning	196
7.4	Interference-Based DCA Schemes	202
	Problems	205
	References	208
8	Orthogonal Frequency Hopping	211
8.1	Random Channel Allocation	211
8.2	Slow Frequency Hopping System Design	221
	Problems	224
	References	228
9	DS-CDMA in Wireless Networks	229
9.1	DS-CDMA Random Resource Allocation	229
9.2	Simple Capacity Estimation of DS-CDMA Systems	231
9.3	Refined Capacity Estimation of DS-CDMA Systems	234
9.4	Erlang Capacity of DS-CDMA Systems	235
9.5	Capacity of Multi-Service DS-CDMA Systems	238
9.6	Power Control in DS-CDMA Systems	243
9.7	Soft Handoff in DS-CDMA Systems	248
9.8	Dynamic Cell Management in DS-CDMA Systems	252
	Problems	255
	References	258
10	Resource Management in Packet Access Systems	259
10.1	Data Traffic and Performance Models	259
10.2	Packet Multiple Access	263
10.3	Some Packet Access Applications	288
10.3.1	WCDMA--Packet Access	288
10.3.2	IEEE 802.11 Wireless Local Area Network (WLAN) Access	290
	Problems	291
	References	294
11	Cell-Planning	297
11.1	The Cellular Concept	297
11.2	Cell-Planning Based on Regular Hexagon Geometry	298
11.3	Hierarchical Cell Structure	301
11.3.1	Channel Separation in HCS	302
11.3.2	Velocity-Based (Interlayer) Handoff	304
11.4	Automatic Cell-Planning	304
	References	305
12	Some Fundamentals of Wireless Infrastructure Economics	307
12.1	Telecommunication Infrastructures	307
12.2	Wireless Access Systems	311
12.3	Cost Models for Wideband Wireless Infrastructures	315
	Problems	325
	References	325
Appendix A	Propagation Models for Wireless Networks	327
	References	333
Appendix B	Simulation Models	335
Appendix C	RUNE Tutorial	347
	About the Author	363
	Index	365

Preface

The development in the field of wireless communications has been nothing short of astonishing in the past decades. We now are witnessing the transition between the mobile telephone era and the era of wireless computing. With the breakthrough advances of digital signal processing high data rate, many of the technical problems associated with the adverse and changing propagation conditions in mobile radio communication have been solved. Multimegabit data rates to portable mobile terminals are no longer science fiction, but reality. As the engineer seems to have the upper hand in this struggle against nature, very much of the development efforts are concentrated on the social struggle for scarce resources, such as the frequency spectrum and terminal battery power. The question is not only if we, as engineers, can provide wideband wireless communication everywhere, but rather, if we can afford it. These issues, the Radio Resource Management (RRM) problem are addressed in this book.

Chapter 1 provides a brief introduction to the problems in resource management and an historical outlook over the field and its relations to adjacent disciplines. In Chapter 2, a refresher of multi-user communication theory is given. Readers with a solid background in this area may omit the first section of this chapter. The last section of Chapter 2 introduces the analysis model used throughout the book. In Chapter 3, the radio resource management problem is defined in a more stringent way. Chapter 4 is probably the core chapter of the book where static resource management and cellular system design is introduced and the RUNE tool is put to work for the first time. In Chapters 5-7, various elements of resource management, such as handoffs, dynamic channel allocation, and transmitter power control are treated. Whereas the treatment in Chapters 1-7 mainly has been focused on F/TDMA type (orthogonal) waveforms, Chapters 8 and 9 deal with spread spectrum waveforms and the special problems in RRM for these systems. In particular Chapter 9, where resource management issues in CDMA systems are dealt with, is an important chapter in the book. Chapter 10 brings the focus on to RRM for data communication systems and the special characteristics and problems related to management of packet traffic. In Chapter 11, various aspects of system planning are investigated, in particular so-called "hierarchical cell structures" (HCS). The last chapter, Chapter 12, widens the scope of RRM to consider resources other than the frequency spectrum. Here also other resources are taken into account, mainly the infrastructure of fixed networks and wireless access ports. Throughout the book, examples from the application of RRM techniques, current 2G systems, as well as future 3G systems are provided.

The book is intended as a textbook for a second graduate course in wireless networks. The student and reader should be familiar with the fundamentals of radio communications, communication theory, and some queuing theory basics. Wireless networks are complicated systems, which makes the design and performance analysis inherently difficult. Several approaches are taken in the book. Classical analysis involves highly simplified models but renders easily tractable results. Slightly more elaborate models are analyzed by means of numerical analysis. The most interesting results, however, are those derived from the more realistic models for propagation and traffic conditions. Here, stochastic simulation has been the tool of choice in the field. For this purpose, RUNE, a MATLAB™-based software tool for performance analysis in wireless networks, has been included in the book. This tool was originally developed at Ericsson, but has been developed by the software authors for pedagogical use. Most of the examples in the book that require simulations have been solved using this tool. The software solutions for these examples have been provided on the CD, enabling the reader to repeat and modify the experiments in the book. In addition, a number of problems are provided for each chapter. Some of the problems are marked with an asterisk and require simulation solutions with the RUNE tools. Most of the material has been used in courses given by the authors at the Royal Institute of Technology (KTH) in Stockholm, Sweden, and in various in-house courses at Ericsson.

The authors would like to thank the software authors, Magnus Almgren at Ericsson, who is the original architect of RUNE, and Olav Queseth at KTH, who made RUNE "student friendly," for their valuable contributions and discussions around the simulation examples in the book. We would also like to acknowledge the help received in the development of the course material and early versions of the manuscript. In particular we are grateful for the contributions of Magnus Frodigh, Hakan Olofsson, Anders Furuskar, and Sverker Magnusson at Ericsson Radio Systems. Thanks to all graduate students at the Radio Communication Systems laboratory at KTH that have been instrumental in solving and designing many of the problems. Last but not least, we would like to extend our gratitude to the anonymous reviewer whose valuable comments have helped us to clarify some of the more intricate concepts in the book.

Jens Zander
Seong-Lyun Kim

Editorial Reviews

Engineers at the Royal Institute of Technology in Stockholm offer their colleagues designing radio communications systems a new, unified approach to managing scarce radio resources such as frequency spectrum and terminal battery power. They explore the interrelationships between such factors as power control, channel allocations, and link performance. They also pass on some fundamentals of wireless infrastructure economics. The disk contains the Rudimentary Network Emulator software, which simplifies creating network simulations, is implemented in a MATLAB environment, and illustrates examples presented in the text. Annotation c. Book News, Inc., Portland, OR (booknews.com)

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