Here’s a brief summary of each chapter.
Chapter 1: The Birth of an Industry
This chapter chronicles the early years of the electric telegraph. It starts with the chaotic scenes in the US congress when – after many setbacks – Samuel Morse was finally granted the funding he needed to construct an experimental telegraph link from Washington to Baltimore. This link turned out to be much more challenging to build than Morse had anticipated, and the project came close to failure. However, on 24th May 1844 he finally succeeded in transmitting the biblical phrase “What God hath wrought !”. The chapter explains the basic principles of the Morse telegraph, and introduces the Morse Code (which remained in use for many years after the telegraph had disappeared into history).
Samuel Morse came to inventing after an early career as a portrait painter. Despite popular belief, he was not the first person to build a working telegraph – in the UK, William Fothergill Cooke and Charles Wheatstone had done this several years earlier, and the system had demonstrated its capabilities in dramatic fashion when it was used to catch a murderer. There had, in fact, been some even earlier attempts to construct a telegraph, and the chapter introduces such characters as Charles Morrison and Francis Ronalds. It concludes with a brief description of the dramatic impact that the telegraph had on 19th century life.
Chapter 2: The Telegraph Goes Global
Chapter 2 considers how the Morse telegraph evolved from an experimental link between Baltimore and Washington – a distance of approximately forty miles – to an international network that spanned the globe. It starts with the development of international undersea cables, and the heroic attempts to lay a trans-Atlantic cable. It then discusses various inventions that enabled a cable carry more traffic. It also considers ways in which the telegraph was developed to avoid the need for a trained operator; these systems include Bain’s chemical telegraph, the stock ticker and the teletype.
Many people believe that the fax machine was a 20th century invention, but 19th century pioneers such as Bain, Bakewell and Caselli were able to transmit facsimile images over the telegraph network. Early fax machines were amazing pieces of engineering. A pendulum was used at the transmitter to scan the image, with a second pendulum at the receiver to re-create the image. Electromagnets were used to keep the two pendulums synchronised.
Chapter 3: A Gatecrasher Spoils the Party
This chapter describes the events that led to the invention of the telephone, and the subsequent disputes that broke out over who had really invented it. In common with most historical accounts, this chapter focuses primarily on the work of Alexander Graham Bell, but it does give full credit to other significant contributors such as Elisha Gray, Thomas Edison and Philip Reis. It also acknowledges the vote by the US Congress in 2001 that declared Antonio Meucci to be the true inventor of the telephone.
The chapter begins by describing the scene at the Centennial Exhibition in Philadelphia in 1876. An unknown inventor called Alexander Graham Bell was exhibiting his newly-invented telephone, but it was not until he managed to attract the attention of the Emperor of Brazil that anybody took much notice. Bell’s grandfather, father and uncle had all had a professional interest in the science of speech, and the young Bell had constructed a “speaking machine” using a set of bellows and the larynx from a dissected sheep. Bell started his professional career working with deaf children, but his inventive mind soon turned to the “harmonic telegraph” – a system for squeezing more messages down a single telegraph line by using matched pairs of tuning forks operating at different frequencies. As a result of a fortunate accident in the laboratory, Bell stumbled upon a way of transmitting speech electrically using “undulatory currents”, and from there it was a fairly short step to those famous but rather uninspiring first words “Mr Watson. Come here. I want to see you.”
Chapter 4: Early Telephone Networks
The earliest telephone installations were simply point-to-point connections between two houses, but experience with the telegraph had shown how these simple connections could be built into much more complex networks. Switchboards were initially manual, and calls could only be established by talking to an operator. The first automatic telephone exchange was invented by a Kansas City undertaker called Almon B. Strowger. The original design required callers to tap out the required number on three separate keys, but these keys were soon replaced by rotary dials. Rotary dials remained the standard method of dialling a telephone number until the arrival of the push button telephone.
The chapter includes a simple explanation of how an electro-mechanical telephone exchange works. It then considers how telephone exchanges talk to each other (signalling), and illustrates some of the principles involved by discussing the strange phenomenon of “phone phreaking”. It also reviews some problems encountered on the telephone network that had not previously been encountered on the telegraph (for example, signal attenuation on long distance lines was a major problem before the invention of electronic amplifiers, and telephone calls over trans-Atlantic cables did not become possible until 1956).
Chapter 5: Going Digital
This chapter considers the changes to the telephone network that were brought about by the introduction of digital technology. It starts with a simple explanation of the differences between analogue and digital, and the advantages that digital can bring. It then explains how analogue waveforms (such as speech) can be carried in the form of ones and zeros over a digital network. The chapter is not afraid to address some slightly challenging issues, but the treatment is always aimed at non-technical readers. For example, the important concept of aliasing is introduced as the reason why wagon wheels sometimes appear to turn backwards in western movies.
The chapter then turns to the history of digital technology, and introduces some significant (and delightfully eccentric) characters such as Alec Reeves and Claude Shannon.
With the liberalisation that occurred in the telecoms market in the 1990’s, new network operators could build all-digital networks, while the more established players had to continue operating their “legacy” analogue networks. The process of converting a large analogue network to digital is discussed. Despite considerable progress in the core of the network, most residential telephone lines are still analogue.
Chapter 6: A Bit of Wet String
Transmission systems provide the links between telephone exchanges. In the early days of the telephone network, transmission links were based on uninsulated lengths of wire suspended from telegraph poles. However, this arrangement was far from perfect, and the development of coaxial cable in 1929 was a significant step forward. Radio also had an important role to play, and the chapter chronicles the development of radio from the inspired predictions of James Clerk Maxwell (experimentally confirmed by Heinrich Hertz) to Marconi’s famous demonstrations that radio range was not necessarily restricted by the curvature of the earth. Marconi’s original claim to have transmitted a message across the Atlantic may now be open to doubt, but there is no doubt that he was very effective in developing the commercial applications of radio – particularly for maritime applications. The chapter describes the role that radio played in the capture of the murderer Dr Crippen, and in reducing the loss of life after the sinking of the Titanic. Before leaving the subject of radio, the history of satellite communications is briefly discussed.
In most modern networks, the transmission links are based almost entirely on fibre optics. The development of fibre optic technology is charted from a 19th century curiosity to the all-optical networks that are likely to appear in the 21st century. Leading edge optical technologies are briefly explained, but many of these technologies are based on much older ideas – solitons, for example, were discovered in 1834 on a Scottish canal, but their significance was not recognised for many years.
Chapter 7: The Last Mile
An access network provides the “last mile” connection to customers’ homes and offices. In well-established networks, the access network often contains large numbers of copper-based telephone lines. Although copper cables cannot compete with optical fibre in terms of bandwidth, broadband technologies have enabled standard telephone lines to carry reasonably fast digital services. Copper cable is cheap and easy to work with and – thanks to many decades of investment –is already installed in vast quantities.
The only significant competition in the access network comes from the cable TV networks, but radio-based access technologies have the potential to change this. Public WiFi services are becoming common, although the spectacular failure of Ionica some years ago – and the more recent concerns about WiMAX – demonstrate that radio is by no means a one-way bet. The European Union’s futuristic ideas for providing radio-based broadband services from “High Altitude Platforms” in the sky are briefly discussed.
The access network of the future will be required to deliver a wide range of services including broadcast television, video on demand, telephony, high speed Internet access, networked gaming, telecare, telemedicine, security and building management. We should therefore expect to see optical fibre playing an increasingly important role in the access network, and “Fibre To The Home” networks are already starting to appear.
Chapter 8: Computers Get Chatty
Most large public networks were originally designed to carry telephone calls. However, the inexorable growth in computer networking has resulted in data traffic now exceeding voice traffic on most public networks. Unfortunately, data traffic has significantly different characteristics from voice, and it requires a different type of network to carry it efficiently. The implications of this change are explored at the start of this chapter.
The development of Local Area Networks (LANs) from shared media networks based upon coaxial cable to switched networks based upon twisted pair cable is described by tracing the evolution of the Ethernet standard from Bob Metcalfe’s early experiments in the 1970’s through to the present day. Other significant LAN technologies, such as Wireless LANs and Token Ring, are also briefly discussed.
The second half of this chapter provides a short introduction to network protocols. This may not seem like a terribly sexy subject, but a basic understanding of protocols is needed to appreciate how the Internet works. In particular, the widely-used ISO 7-layer model is used to explain the different roles played by routers and switches in very large data networks.
Chapter 9: The Birth of the Internet
This chapter describes how an experimental network funded by the US Department of Defense evolved into a global network of networks called the Internet. The early research took place in the early 1960’s, with significant contributions from Paul Baran at RAND Corporation in California and Donald Davies at NPL in London. Despite popular mythology, the ARPANET network was not developed to provide a resilient communications network that would survive a nuclear attack – its original justification was to enable very large (and expensive) mainframe computers to be shared by researchers in different parts of the USA. This chapter chronicles the early years of the ARPANET, including BBN’s development of Interface Message Processors (the forerunners of Internet routers), and Cerf & Kahn’s development of the TCP/IP protocol (which enabled disparate networks to be linked together).
As networking developed, the ARPANET became just one of a number of interconnected networks using the TCP/IP protocol. When the ARPANET was finally shut down, the network of networks lived on. Commercial arrangements were put in place to replace the military funding, and the Internet was born.
Chapter 10: Life in Cyberspace
Traffic measurements on the early Arpanet showed that actual network traffic was not conforming to predictions. This turned out to be because an email application had been developed that Arpanet users took to with extraordinary enthusiasm. Email was the first of many Internet applications that enjoyed totally unexpected success.
This chapter introduces some of the most important applications to have appeared on the Internet. These include email, the World Wide Web, the Domain Name System, search engines, bulletin boards, Usenet newsgroups, Internet forums, discussion groups, blogs, wikis, instant messaging, chat rooms, podcasting, peer-to-peer networks, Internet voice and video services (Skype, YouTube), social networking sites (Facebook, MySpace) and virtual worlds (SecondLife). This is a long chapter, but it illustrates the extraordinary diversity of new applications that can be built upon a “dumb” network such as the Internet. This separation between the network infrastructure and the applications that it supports has become a guiding principle for modern network architectures.
Chapter 11: The Mobile Revolution
Mobile networks have been one of the great success stories of recent times. This chapter traces the beginnings of mobile telephony back to nineteenth century experiments by David Hughes and Alexander Graham Bell, and the central antenna systems that appeared in the USA in the 1920’s. Modern cellular network concepts were being discussed as early as the late 1940’s, but the first practical implementation of these concepts was the payphone service that appeared in 1969 on Metroliner trains running between New York and Washington. Analogue cellular networks started to appear in the late 1970’s, and the technology grew rapidly in the 1980’s. However, the lack of a common cellular standard prevented roaming between networks, and reduced economies of scale. This prompted the development of a European second generation (2G) mobile standard that eventually became GSM.
Subsequent enhancements (such as GPRS and EDGE) gave GSM a low speed data capability, prompting some to categorise this as a “2.5G” technology. However, the bandwidths available were not sufficient for more demanding applications, and this led to the development of 3rd Generation mobile network technology. 3G offered a marriage between two highly successful technologies – mobile networks and the Internet. It was seen by investors as a dream come true, and prices for 3G operating licences reached stratospheric heights during the Internet boom. However, the fortunes of 3G were seriously dented by the subsequent market crash, and by the lack of any “killer applications” for the new technology. Despite these setbacks, work is proceeding to define a 4th generation mobile network standard. The chapter concludes with a brief discussion of satellite telephones.
Chapter 12: When Failure is Not an Option …
Network faults are a fact of life. However, customers have little patience with a network where services are regularly disrupted, so there is strong competitive pressure to improve service quality. This, in turn, is linked to higher costs, so each network operator has to find the optimum balance for their business.
This chapter discusses some common types of network fault (including hardware failures, cable cuts, software failures, operator errors and sabotage) and considers ways in which network reliability can be enhanced. If network reliability is not sufficient to meet the needs of the customer, then resilience techniques can be used to prevent network faults from disrupting services. The chapter is punctuated with examples of high profile network failures that illustrate what can happen when things go badly wrong. The chapter concludes with some thoughts on disaster recovery.
Chapter 13: What Comes Next ?
The final chapter discusses some key developments in telecommunications that can be expected during the next few years. It starts by considering the transition that is already underway to “Next Generation” networks, and then turns to developments in the mobile field where we can expect to see a fourth generation of mobile technology offering much higher speeds and a plethora of new services. The mobile phone will become a remote control for almost every aspect of our lives, with new capabilities such as mobile television receiver, wallet, ID card and set of keys being added to existing capabilities such as camera, mp3 player and navigation device. New service providers will emerge offering sophisticated services and highly innovative payment schemes. Some of these services will be completely free to the user.
The impact of developments in telecoms will continue to be felt in other industries. Television broadcasting will face major challenges from network-based services as viewers finally break free from the constraints of conventional television scheduling, and professional program makers find themselves having to compete with user-generated content. Personal computers will become much simpler and cheaper as ubiquitous Internet access means that software and storage can migrate into the core of the network.
Finally, some areas of concern are addressed. These include computer malware (viruses, worms etc), spam email and potential health problems caused by mobile phone usage. These are serious challenges, but the future of the telecommunications industry remains bright. The biggest machine in the world will keep on getting bigger!
To ensure that this book is easy to read, technical details and non-essential background information have been confined to footnotes and appendices. There are eighteen appendices (yes, I know it’s a lot, but they’re all short):
- Appendix A: Duplex Telegraph
- Appendix B: Baudot Code
- Appendix C: Microphone Wars
- Appendix D: Digital Signal Processing
- Appendix E: DSL Technologies
- Appendix F: Levelling-Up the Playing Field
- Appendix G: Fixed Wireless Access Networks
- Appendix H: Internet Service Provider Networks
- Appendix I: The Internet Address Shortage
- Appendix J: Virtual Private Networks
- Appendix K: Internet Voice Services
- Appendix L: IP Television
- Appendix M: GSM Networks
- Appendix N: Wideband CDMA
- Appendix O: Network Reliability
- Appendix P: Availability
- Appendix Q: Error Detection and Correction