CHAPTER 4 of Canadian Developments in Telecommunications: An Overview of Significant Contributions. Thomal L. McPhail and David C. Coll, Editors. ISBN 0-88953-083-1. Published by the University of Calgary, 1986
David C. Coll
There have been a number of noteworthy Canadian activities in telecommunications that are not described in detail in the following chapters. In addition to satellite communications, public digital networks, fiber optics and mobile radio, which are described, some other Canadian achievements in telecommunications will be reviewed briefly in this chapter. These include HF and meteor burst communications, signal processing, cable television, and videotex.
One of the interesting attributes of the telecommunications business in Canada, particularly those sectors of it that derive from an R & D background, is just how small a community it actually is. Much of the activity to be described in this chapter was conducted by people and institutions closely associated with those mentioned in the following chapters. Two institutions have particularly influenced the development of telecommunications in Canada. The first was the Defence Research Telecommunications Establishment (DRTE), which became the Communications Research Centre (CRC) of the Department of Communications (DOC) when the latter was formed. The second is Bell-Northern Research. These two, along with a number of others, were the "technology engines" (as D.J. Doyle, the founding president of Digital Equipment of Canada and a DRTE alumnus, would say) that drove much of the work - either directly or through people who had gained some of their training and experience in those institutions.
The upper atmospheric research program at DRTE led directly to the Canadian space program and satellite communications. It also spawned a number of other activities, among which were sounder-assisted HF communications and meteor burst communications. The Department of Communications and CRC were also the source of substantial work on wired city concepts.
In addition to the communications research taking place at CRC, DOC has been concerned with computers and privacy, the direction that the "information society" would take, and ways to assess its impact and to control and regulate its growth. The marriage of the computer and telecommunications was one of the first areas investigated by the Department of Communications (DOC) when it was established. These investigations were described in "Instant World", published in 1971. DOC was responsible for Telidon, the Canadian videotex system that led to the establishment of NAPLPS, the North American Presentation Level Syntax, and a short-lived information industry. Not long ago, DOC was responsible for a series of major experiments in Office Communication Systems. However, recently, the emphasis at DOC has shifted from the creation of communications technology to the assessment of its impact, and to the promotion of the cultural aspects of communications: the fires in one of the premier Canadian "technology engines" have been heavily banked, if not extinguished.
Canadians were very active in anti-submarine warfare during World War 11. This took the highly visible form of active convoy escort duty during the Battle of the Atlantic; it also involved the operation of very successful high frequency (HF) direction finding stations in Canada. It has been suggested that the output from these stations, though virtually unheralded, may have contributed more to the defeat of the U-boat than radar ever did. In any event, the involvement in ionospheric propagation gained during these activities was preserved and exploited through the research and development program of the Canadian Defence Research Board (DRB) at the Defence Research Telecommunications Establishment (DRTE) in Ottawa.
Long distance radio communications in the late forties and early fifties were primarily dependent on reflections from the ionosphere. In Canada, ionospheric propagation was often affected by the solar activity that also gives rise to the aurora borealis. Thus, a need for research in ionospheric physics existed, which was met at DRTE. The research resulted in improved models of the ionosphere that could be used to predict propagation conditions. It also led to the use of oblique ionospheric sounders that could rapidly measure the response of the ionosphere across the entire HF band to provide HF communications networks with timely information about the assigned channels that they should be using (Hatton, 1961; Jull, et al., 1962).
The advent of satellite communications has eclipsed the use of HF ionospheric channels for long distance communications; but HF communication systems which are fully adaptive to channel characteristics could easily be constructed with modem electronic technology.
The desire to know even more about the ionosphere was used as the raison d'etre for Canada's entry into the satellite game. As R.M. Dohoo reports in his chapter on the Canadian Satellite Communications Program, 'top-side sounding' of the ionosphere was the function of the Allouette and ISIS satellites. These first Canadian satellites carried swept-frequency HF radars that probed the ionosphere from above, contributing vast amounts of data about the ionosphere for many years. It was only after a number of scientific satellites were launched that Canada moved into the communication satellite area.
The ionized trails left by meteors as they streak through the upper atmosphere were well known to Canadian researchers because of the concern with radio wave propagation in the ionosphere at DRTE and a general interest in meteors at the National Research Council (NRC).
Research was conducted on the reflection of radio waves from meteor trails and it was found that they could support HF propagation over long distances for periods ranging from milliseconds to minutes. The reflections occur as meteors penetrate the E layer -about 100 km above the earth's surface. The rate at which useable meteor trails occur varies considerably, depending on the time of day, the season of the year and geographical location; but, by and large, enough occur to support communications with a duty ratio of about 5%.
A system, called JANET, was developed by DRTE in cooperation with Ferranti-Packard in the middle fifties (Forsythe, et al., 195 1). It used a burst-type mode of operation to transmit digital information (teletype). The receipt of a signal of sufficient strength at one site from a transmitter at another indicated the presence of a useable path. A message, stored on tape, was transmitted until the received signal strength dropped below a threshold. The transmission was continued when the next suitable meteor trail was formed.
JANET operated around 40 MHz and transmitted data at 1300 words per minute (or 1300 bits per second), using binary pulse position modulation. Although throughput was dependent on transmitted power and antenna gains, tests showed that, on the average, 60 words per minute could be maintained.
Unfortunately the major operational trials of the JANET system coincided with very severe ionospheric storms. The ionization levels were so high that the signals that were not absorbed in the D layer were reflected to the ground and the resulting backscatter interference made the transmissions useless. JANET was shelved.
Further research on propagation at higher frequencies (which is less susceptible to ionospheric effects) was carried out, and the beginnings of modern digital circuitry were applied to the problem, but JANET was never successfully marketed (Coll, 1963). It may have been ahead of its time: meteor burst communications is undergoing a revival, especially for interrogation of automatic data platforms. It will be interesting to see what happens to the new systems as the sunspot cycle develops.
The application of digital signal processing techniques in telecommunications is now taken for granted. Digital transmission is commonplace (and may, in fact, replace analog in the not too distant future) modems are realized by programming digital signal processing chips; real-time video conferencing systems employing motion-compensated image compression techniques are commercially available; speech synthesis is routine and recognition can be implemented; and so on. This revolution in signal processing and transmission was started by the advent of transistor switches in the mid-fifties, nurtured by the appearance of the mini computer in the early sixties, and reached true reality with the development of the micro-processor in the mid-seventies. The emergence of special purpose DSP chips and the super-mini, or the mainframe on a chip, in the eighties has brought digital signal processing to maturity.
There are three examples of Canadian involvement with digital signal processing that span the period in which DSP was developed. The first is the use of DSP in HF and meteor-burst communications. The second is the invention of automatic data channel equalization; and the third related to digital television.
The potential of digital signal processing, real-time computer systems and digital communications was exploited at an early stage in the design of HF and meteor-burst systems at DRTE. Coded pulse sequences with good autocorrelation properties were used to enhance the sensitivity of oblique ionospheric sounders.
Both analog and digital matched filter receivers for these sequences were constructed from logical modules and used in a series of experiments in the early sixties. Similar pulse sequences were used as synchronizing preambles in meteor-burst data packets (Coll, 1957; 1965; 1966; Coll & Storey, 1964).
In the summer of 1963, Prof. D.A. George (now the Dean of Applied Science at Simon Fraser University) made a significant theoretical contribution to communications theory in the form of specification of the optimum receiver for data signals corrupted by intersymbol interference (George, 1965). A practical version of this receiver was implemented in the following years (Coll & George, 1965) which led to a patent being issued to the Crown for the Transversal Equalizer (US patent 3, 521, 037). The experimental receiver was implemented using digital signal processing built from logic modules operating under the real-time control of a DEC PDP-5 mini-computer. Because the receiver had a computer in it, subsequent research was able to lead to a receiver that automatically adjusted itself to changing channel conditions (Coll & Storey, 1966; Coll, 1967; George, et al., 1970). Such adaptive equalizers are now routinely incorporated into all high-speed modems.
As a historical note, the PDP-5 computer referred to was among the first mini-computers purchased by the Government of Canada, and established the concept of computers being used as components within other systems. At the time it was ordered the government was very concerned about too many computers being bought. It was extremely difficult to convince the authorities that the PDP-5 was a component, and that its purchase was not a blatant duplication of existing computer power. Processing of the order for the PDP-5 through the government inter-departmental EDP computer committees took twenty-seven weeks - after the order had been approved by all responsible technical authorities. During this entire time a PDP-5 was held available by Digital for delivery on one hour's notice. One wonders if things ever change.
The growth of capability in DSP is nowhere more evident than in the leading edge research being conducted at the Bell-Northern Laboratories in Montreal. There, in cooperation with the l'Institut National de la Recherche Scientifique (INRS) -Telecommunications and McGill University, researchers under the direction of Dr. B. Prasada are developing digital techniques for the real-time compression of colour television (Netravali & Prasada, 1985; Sabri, 1984). The processing rates required tousefully compress and decompress television signals without noticeable degradation - are truly astounding, which in itself is an indication of the level to which DSP has progressed. Up to eleven different compression schemes operate in parallel with the representation created by the most efficient being selected automatically as the transmitted version. It is the degree of complexity that provides the ability of the TV codecs (coder-decoder) to adapt to varying image characteristics which represents the maturity of DSP.
The Canadian love affair with communications did not diminish with the introduction of television. Canada has very extensive cable TV installations, and has pursued the use of these broadband facilities for the delivery of all sorts of programming and non-programming services into the home (Coll & Hancock, 1985).
Canada is one of the most heavily cabled countries in the world. In 1982, 80% of Canadian households were passed by cable -television and 75% of these are subscribers. This means that in 1982 there were almost 5 million cable subscribers in Canada.
The proximity of major Canadian cities to the United States border was responsible for the development of the cable television industry in Canada (Easton, 1980). When television broadcasting was introduced in the United States, signals from Buffalo could be picked up on rabbit ears in Toronto. It was some time before Canadian TV broadcasting started, but expectations had been aroused by the Toronto experience. In fact, the reception of US TV, "just like the folks in Toronto", became one of the unwritten Canadian birthrights.
To accommodate the "right" to view American TV, cable systems were installed in many locations where there was no local television but where there was a US station far enough away that elaborate antennas were required to receive its signal. This was particularly true in the fringe reception areas in Southern Ontario and British Columbia.
In Montreal, Canadian broadcasting started before US stations within receiving distance came on the air, and it was carried along with movies on an existing cable network. The US stations, which were located in Upper New York State, could not be picked up on rabbit ears, especially in parts of the city shielded by Mount Royal. Thus, it was not long before the Canadian channels were bumped from the cable and US channels were being distributed.
This led to public and government concern about the Canadian content in broadcasting and as a result the Canadian government, in the form of the Canadian Radio-television and Telecommunications Commission (CRTC), regulates the cable industry. In particular, it determines the mix of Canadian and US channels that can be carried. Canadian stations are carried on the regular VHF channels. US channels, pay-TV and non-programming services are carried on converter channels (or impaired VHF channels).
Even with off-air programming available in much of Canada, and with direct-to-home satellite reception possible from US satellites, cable TV is a ubiquitous Canadian phenomenon. Cable TV programming is even distributed to remotely located head-ends via satellite. Cable companies are competing with VCR/videotape rental, direct-to-home satellite broadcasting, personal computer communications and other distractions with general and customized pay-TV offerings and a host of non-programming services. These latter include the common news channel and such long-promised services as home shopping.
One of the most comprehensive private, multi-functional cable installations in Canada is the OASIS system. This is a cable system installed on Parliament Hill in Ottawa to serve the members of the House of Commons. OASIS provides Members of Parliament with television programs, including those from all regions of the country, the House proceedings in both official languages, and off-air TV programs as well as whatever can be received from visible satellites.
The system also provides data networks, computer access, and voice service. It really does provide virtually every available communication modality in an integrated package. OASIS is implemented with a standard cable TV technology incorporating broadband local area networks, so that the cost is reasonable and the capacity immense.
The potential of the broadband cable television network for the delivery of communications into the home and between institutions has been well recognized in Canada. Substantial studies of the "wired city" were conducted in universities and government laboratories (Coll, et al., 1975).
Telidon, the Canadian videotex phenomenon, deserves some description. This communications program had many facets. It was involved with the definition of a language of instructions which could be used to draw pictures; it was concerned with the transmission of these drawing instructions; it was concerned with equipment on which the instructions could draw pictures; it was concerned with the creation of public data bases containing (the instructions to draw) pictures which subscribers could retrieve in response to their queries for information.
A set of Graphics Transmission Instructions (GTIs) were developed as part of a DRTE research program in multiple user access to shared computer graphics visual spaces. They were developed so that remote users of a graphics display could interact with the display by directly modifying the file that contained the image drawing commands. The modification was achieved by transmitting graphics commands in the guise of ASCII characters. Thus the capability existed at DRTE for the creation of computer graphics images from a remote location over telephone lines when the Minister of Communications at the time (Mme. Jeanne Sauve, now the Governor General of Canada) asked whether or not this was the same as the European videotex systems she had seen. She was informed that it was not, it was much better! And, in fact, it was a better picture because the display was a vector computer graphics terminals and not a block mosaic character display.
What was to become known as Telidon grew from this project in response to competition from Prestel and Antiope. The GTIs became PDIs: a set of Picture Description Instructions which, when received with the proper equipment, could create an image on a television set. These PDIs were coded as strings of standard (ASCII) teletype characters so that they could be transmitted to the Telidon terminals in the same way that text files were. As well, means were developed to transmit Telidon PDIs as data signals on the spare lines in broadcast television signals. The idea was that every TV set would become a graphics terminal for information systems. As a potential application for this new communications mode, Telidon was advertised as the coming of the information age: "two-way television", "Talk back to your TV set", and so on. The expectations were that Telidon would provide the means to access data bases: access to all the world's information in every home!
Several things went wrong on the way to the marketplace. While most of the blame for the "failure" of the Telidon project can be traced to one salient reason:the lack of a market for information, several strategical and technicals errors were committed during its development. For one thing, the introduction of Telidon coincided with the advent of the personal computer, even though it was one. Home computers could not be used as Telidon terminals, although they were widely used for access to information systems like The Source. The Telidon PDIs were not consistent with concurrent developments in the computer graphics field, even though Telidon terminals were graphics devices. Telidon is essentially a terminal character set. Originally, the Telidon data bases could not be accessed using standard data communications. Decoders were expensive, and image creation systems very expensive. High level image creation languages were not developed. The structure of the Telidon data bases was never properly determined, so that information searches were restricted to the most boring and tedious of menu searches and tree following. And so on.
Telidon was adopted by the Canadian government as a flagship hi-tech project to demonstrate Canadian competence. It was also supported as the foundation of a new industry - the information marketplace. However, it was never clear whether the DOC role was to create the technology, establish a world of information systems in which Telidon would be used, assure Telidon's future by establishing it as a world standard (a major DOC strategy that dissipated the technical efforts and drained the project of its brilliant technical leadership - the small group of original inventors were involved in all aspects: invention, design, debugging, contracting, standards, and marketing, as well as promotion and selling of the concepts), or whether market forces should rule to accept or reject the idea.
The latter happened, and the real reason was that no one would pay for information. Aside from hotel lobby travel information terminals, cable TV information channels and a few similar heavily-subsidized applications, there just wasn't the market for information in the form that Telidon could provide it. Information is all too available in Canada, for free, from other sources. Even as the technology to produce NAPLPS-compatible videotex and teletext of technically superb quality at economical prices is being developed, the last commercial broadcast Telidon venture in Ottawa, the NABU Network, closed down last month.
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