ADSL, VDSL, and Multicarrier Modulation

John A. C. Bingham, Wiley Series in Telecommunications and Signal Processing, John Wiley & Sons, Inc. 2000, ISBN: 0-47 1-29099-8, hardcover, 314 pages

Reviewer: Chaohuang (Steve) Zeng

      Digital subscriber line (DSL) technology uses existing twisted-pair copper wires in the telephone cables to provide high-speed data communication between the central office and the customer premises. There are several million DSL subscribers worldwide, and the number is increasing rapidly. Compared to the traditional voiceband modem, DSL technology uses much wider bandwidth. The signal, however, attenuates severely in the higher frequencies. Therefore, advanced communication techniques, such as multicarrier modulation, are used to restore the original transmitted signal.
      This book is an outstanding source on the principle of multicarrier modulation, the design practice of DSL using multicarrier modulation, and the open issues in asynchronous DSL (ADSL) and very-high-rate DSL (VDSL) systems. John A. C. Bingham is a world-renowned expert in the areas of multicarrier modulation and DSL modem design. This book distills his design experience and is a very valuable handbook for the modem designer and programmer. Many techniques described in the book can be extended beyond DSL systems to other systems, such as wireless local area networks (WLANs, IEEE 802.11a). Although it is not as rigorous as many academic textbooks, this book is well suited to graduate students and researchers who are interested in high-speed transmission techniques.
      Chapter 1 introduces basic facts on the DSL family: ISDN, T1, E1, HDSL, ADSL, VDSL, HDSL2, and SDSL. Then it describes the history of multicarrier modulation and its major applications. The references in this chapter provide interested readers comprehensive pointers to literature on this subject. Chapter 2 describes ADSL network architecture, protocols, and equipment. This chapter analyzes ADSL deployment from the perspective of network architecture. A. J. Weissberger is the author of this chapter.
      Chapter 3 first describes the makeup of the digital subscriber line. It then provides the mathematical model for the unshielded twisted pair of copper wires. Finally, the author spends most of the chapter describing the principles, scenarios, and models of crosstalk among the twisted pairs, since crosstalk among wire lines is the major impairment in current DSL systems. Based on the models of the twisted pair and crosstalk, Chapter 4 analyzes the capacity of DSL systems and determines the trade-off among different duplexing methods, such as TDD, FDD, or echo cancellation FDD. Since many different DSL systems (HDSL, SDSL, ADSL, etc.) exist in the same telephone cable, it is mandatory to ensure that these systems are compatible with each other. Chapter 4 describes in detail the impact of this important issue on system management.
      The author then shifts the topic from ADSL systems to multicarrier modulation. Chapter 5 describes the fundamental principle of multicarrier modulation and several important practical issues. These problems include the channel measurement, bit loading in different subcarriers, and peak-to-average ratio. Chapter 6 deals with two of the most popular techniques based on multicarrier modulation, discrete multitone (DMT) in DSL systems, and orthogonal frequency division multiplexing (OFDM) in wireless systems. Unfortunately, the side lobes in both systems fall off slowly because of the rectangular window in the time domain. This chapter describes several methods, such as shaped cyclic prefix, to reduce the side lobe effect. Chapter 7 continues to discuss other types of multicarrier modulation. One such system is discrete wavelet multitone (DWMT), which reduces the side lobe problem.
      Chapter 8 describes the implementation aspects of ADSL systems, which use DMT transmission. This chapter is an excellent source for an ADSL modem design engineer to understand and look up all the important components of the transmitter and receiver. The author himself has extensive experience in designing ADSL modems; the materials covered here are most relevant to practical implementations. Chapter 9 discusses how to ensure that ADSL systems coexist with legacy services, such as voiceband services and ISDN.
      VDSL uses much wider bandwidth than ADSL to offer up to 26 Mb/s symmetric and/or asymmetric data rate. Chapter 10 describes the requirements and implementation of VDSL systems. The author compares various techniques and standard contributions proposed during the evolution of the VDSL standard, and expresses some interesting views on the VDSL standardization process.
      The last chapter describes many open issues and further improvements in DSL systems. This chapter is useful for modem designers to improve system performance. Some of the open issues are excellent topics for Ph.D. theses. In fact, part of my own thesis is inspired by this book! The appendices of this book provide valuable software programs for DSL system analysis, a description of standard organizations, and recommendations for many different DSL systems.
      Overall, this book is very well written and easy to read. It describes the principles and practical issues of multicarrier modulation, and contains invaluable resources for DSL modem implementations.

UMTS Networks: Architecture, Mobility, and Services

Heikki Kaaranen, Ari Ahtiainen, Lauri Laitinen, Siamak Naghian, and Valtteri Niemi, John Wiley & Sons, Ltd., 2001, ISBN 0471 48654 X, hardcover, 302 pages

Reviewer: Andrzej Jajszczyk

      Five authors from Finland, including four from Nokia, wrote an excellent book on third-generation (3G) mobile networks. Universal Mobile Telecommunications System (UMTS) -- a 3G platform for mobility and services -- is expected to replace in the future the very successful GSM. UMTS designers have inherited the best experiences from European GSM and its packet-oriented extensions as well as, concerning the radio interface, from the North American CDMA-based IS-95 system. The newest releases of UMTS also try to use IP networking as much as possible. The resulting solution is a masterpiece of engineering of considerable complexity. To describe it clearly in one volume was a real challenge. But the authors were successful. The book well combines details needed for system designers with a broad view required by a wide range of readers.
      The first two chapters give a general overview of the UMTS system as specified within the 3G Partnership Project (3GPP). Evolution to UMTS from analog 1G mobile networks, through digital 2G, is also briefly presented. Chapter 2 concentrates on the GSM system and its data-oriented extensions such as High Speed Circuit Switched Data (HSCSD), General Packet Radio Service (GPRS), and Enhanced Data for Global Evolution (EDGE). Several 3G implementation scenarios are also described.
      Chapter 3 covers basic information on radio communications within UMTS. It gives a tutorial overview of multipath propagation, fading, and radio resources. Cellular radio communication principles, multiple access techniques, and regulatory issues are also presented. The main attention, however, in this chapter is given to the 3G radio path description. Chapter 4 is devoted to the UMTS radio access network (UTRAN). It presents the UTRAN architecture as well as the base station and the radio network controller. A rough method to estimate WCDMA transceiver capacity might be useful to many readers. Other issues covered in this chapter include modulation methods, receiver techniques, radio resource management, and UTRAN control functions.
      The UMTS core network is described in Chapter 5. Such a network is a basic platform for all communication services including switching of circuit-switched calls and routing of packet data. Three releases (R99, R4, R5) of the core network are presented. These releases differ mainly in the depth of IP penetration. The authors discuss such topics as core network architecture, mobility management, and communication management. The relatively short Chapter 6 describes issues related to the UMTS terminal. The brevity of the description probably reflects the fact that at the time the book was written, 3G terminals were hardly available. The authors concentrate on terminal architecture and capabilities as well as the user interface.
      The success or failure of UMTS will mainly depend on availability and quality of the offered services. A wide range of issues related to the UMTS services is presented in Chapter 7. The authors present the relation between services and the commercial model. Describing the quality of service (QoS) architecture, they discuss the interrelation between delay and required network and queuing resources. The following service capabilities are overviewed: Wireless Application Protocol, location communication services, mobile application execution environment, UMTS Subscriber Identity Module (SIM) application toolkit, and CAMEL service creation environment. CAMEL is a concept of adding mobility on top of an intelligent network (IN). The chapter concludes with issues related to end-to-end services in UMTS. Services belonging to several QoS classes are described. Chapter 8 covers various security aspects of UMTS on both the system and network levels, including security in 3G, access security, protection of applications and services, along with methods for lawful interception.
      The last two chapters present the protocol architecture of UMTS. In Chapter 9 the protocol reference and interworking architectures are described. The authors also present protocols related to transport, radio, and system networks. The protocol architecture is excellently illustrated by procedure examples contained in Chapter 10. The examples include such elementary procedures as paging, radio resource control, connection setup, transaction reasoning, authentication and security, transaction setup, transaction clearing, and radio resource connection release. The other sets of examples cover radio resource and mobility management. A packet data example concludes the chapter.
      The bibliography contains URLs to 3GPP, IETF, and WAP Forum specifications as well other literature, almost exclusively books.
      UMTS Networks: Architecture, Mobility and Services is a very valuable source of information on 3G mobile communications for both specialists and newcomers. Although it does not contain problems to solve, it can also be used as a good textbook or supplementary reading for students.

Design of Optical WDM Networks: LAN, MAN and WAN Architectures

Byrav Ramamurthy, Kluwer Academic Publishers, 2001, ISBN 0-7923-7281-6, hardcover, 166 pages

Reviewer: Andrzej Szymanski

      The book Design of Optical WDM Networks: LAN, MAN and WAN Architectures by Byrav Ramamurthy contains a sampling of problems and proposed solutions associated with design of WDM optical networks. It is targeted at researchers and practitioners in the field of optical networks and WDM, and will also be of interest to students of networking and telecommunications.
      The book investigates the impact of physical-layer issues on the design of wavelength-division-multiplexing-based optical networks. Chapters 1 and 2 serve as an introduction to the field of optical communications. Chapter 1 provides some background on optical communications. Two types of WDM networks are introduced and dealt with: broadcast-and-select networks and wavelength-routed networks. Furthermore, the main design issues and optimization problems connected with the presented network types are identified and explained in general terms.
      Chapter 2 presents different types of equipment used in optical networks. The description is very brief, providing only general information as a background for the remainder of the book. No advanced mathematics is used; however, a great number of references allow the reader to search for more detailed descriptions of particular topics. First, optical fiber and its major features are described. Second, passive optical devices -- splitters, combiners and passive-star couplers -- are discussed. The next part deals with optical amplifiers and signal regeneration. Two main categories of optical amplifiers are introduced, namely semiconductor-laser amplifiers and doped-fiber amplifiers. Then the switching elements are presented: simple crossconnect elements, nonreconfigurable wavelength routers, and reconfigurable wavelength routers. In addition, the idea of an optical packet switch is introduced. Finally, the author identifies physical layer limitations that affect the network design process: signal power, signal-to-noise ratio, crosstalk, and dispersion.
      Chapters 3 and 4 focus on planning of LAN and MAN broadcast-and-select optical networks. Chapter 3 deals with the amplifier placement problem, assuming equally powered wavelengths. The solution approach minimizes the number of amplifiers in the network using mixed-integer linear programming. The author provides both a clear explanation of the problem in mathematical terms and the solution algorithm. The simple optical amplifier model needed for the algorithm is presented here; the more sophisticated one is included in appendices. Finally, sample results achieved using the presented algorithm are discussed and compared to other approaches. The author shows that his approach has the potential to save a significant number of amplifiers compared to other algorithms.
      In Chapter 4 a similar problem, without assuming power equality between wavelengths, is dealt with. The author defines the problem, a mixed-integer nonlinear one, and a suggested solution, having as an objective function the number of amplifiers used. The numerical results included at the end of the chapter show that in certain networks it is possible to gain additional benefits using this method by requiring fewer amplifiers.
      The remaining chapters are focused on WAN optical network design problems. Wavelength conversion is the main theme of Chapter 5. The author presents the concept, purpose, and different methods of wavelength conversion. Then the design issues are presented, followed by a discussion and analysis of performance benefits due to wavelength conversion. Four analytical models, developed in literature, allowing such analysis are presented; the reader is also referred to other sources of information in that field.
      Chapter 6 discusses the impact of the optical signal degradation on transmission quality and how this should be included in the network design process. The author presents the network simulation model, which includes the mathematical model for bit error ratio as a function of crosstalk and amplifier spontaneous emission. The simple model of an optical switch is also presented here. A more detailed switch model is discussed in Appendix A. At the end of the chapter the numerical results are presented and discussed.
      Chapter 7 summarizes the work and presents possible future research directions.
      Both beginners and the more advanced will find this book very interesting. For the former, it is an excellent introduction to optical networking, since it contains general ideas and concepts connected with optical technology presented in clear form and illustrated with many figures and examples. The presented problems and suggested solutions are introduced in two steps: first, the main ideas are presented using descriptive language; then the strict mathematical formulation follows. Advanced readers will find the book remarkable not only because of the presented problems and solutions, but also because of the large number of references to other publications, both those analyzing the given approach in more detail and those describing other contrasting approaches.