IEE ELECTRONICS DIVISION: CHAIRMAN'S ADDRESS

Communications in the 21st centuryC.P. Sandbank, B.Sc, D.I.C., F.lnst.P., C.Eng., F.I.E.E.

Indexing term: Communication

Abstract: A restrained extrapolation is made on the basis of the further development of some of today'stechnology seen against a background of the finite radio spectrum and limited energy resources. Present-daycommunications have become established as a set of complementary services, radio, television, telephone,letters, newspapers, records, films etc, with separate terminal devices and each having their own distributionchannels. It is assumed that in the 21st century the techniques, such as antenna array signal processing, willlead to much more effective use of the radio spectrum and that optical fibres will provide a widebandswitched network to the local area. In these circumstances it will be economically and operationally attract-ive to integrate communications systems providing a wide variety of functions. It is postulated that most'deliveries' connected with information and entertainment will be electronic, leaving physical transportationfor essentials like food and fuel or luxuries like 'limited editions' and paintings where there is pleasure derivedfrom direct association with the originator of the art work. The question of man adapting to the machine orthe machine adapting to man is discussed. It is concluded that further developments in speech recognition aremore likely than man learning to speak or read in a binary language suitable for direct communication withcomputers. It is noted that there has been little change in the basic transducers of electronic communications(i.e. the microphone, loudspeaker, television-camera tube and cr.t. display) since their first introduction.Although electronic aural communications are close to saturating the capability of the human receptor,electronic visual communication has a long way to go before it saturates the capability of the eye-brain com-bination.

1 Trends and constraints

In trying to envisage the shape of communications at thestart of the 21st century, I am helped by the fact that somefairly well established trends in the demands for certaintypes of communication are linked to the development ofour civilisation. If one assumes that civilisation will con-tinue to develop along similar lines, then it is possible toestimate the level of these requirements by the year 2000.Although rapid advances in technology will continue toremove the obstacles between what is possible and what isdesired, the basic laws of physics provide a constraint whichprevents the picture of the future stimulated by the imagin-ation becoming too unrealistic.

Communication takes many forms but, excluding thecommunication between humans who are within earshot orstriking distance of each other, it is convenient to considerit in three major forms. First there is the recorded messagewhich is transmitted or disseminated. The most commonforms of this are, of course, the letter and the book, towhich have been added in the 20th century the gramo-phone record, cine film and magnetic tape. I shall refer tothis as 'recorded' communication. The second group, whichI shall call 'instantaneous' communication, concerns themessage received effectively at the same instant at which itis transmitted, in terms of human reaction time. This istypified by live radio and television. The third group,'interactive' communication, defines transmitted messageswhich can influence the nature of the next message received.Common examples of this are, of course, the telephone andthe remote computer-access terminal.

There are no sharp dividing lines between any of thesegroups, the telephone can be regarded as 'instantaneous'and correspondence by letter is an example of 'interactive'

Paper 8404 E, delivered before the IEE Electronics Division 10thOctober 1979Mr Sandbank is with the BBC Research Department, KingswoodWarren, Tadworth, Surrey KT20 6NP, England

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communication. However, they describe three activitieswhich are currently fairly separate in terms of the transmis-sion media and the terminal devices.

During the last 50 years, radio and television broadcast-ing has developed to the stage where it dominates domesticcommunication, and the international switched-telephonenetwork dominates business communication. During thenext 50 years, I believe that technological developmentsand environmental constraints will bring about an integra-tion of the three groups which will have a major influenceon our habits of communication.

2 Transmission methods

The traditional way of transmitting information over longdistances was by physically carrying 'recorded' messagesfrom one place to another. The 20th century has seen thedevelopment of the two other methods, cable and electro-magnetic waves. The universe may support other methodssuch as gravitational waves, but no practical ways of gener-ating or detecting these have yet been discovered. It isreasonable to predict, therefore, that we will have to livewith the three known methods for at least another 100years as the principal means of transmission.

I develop later the theme that economic constraintsstemming from the limited supply of basic raw materialswill shift the balance from physical to electronic 'deliveries'.Possession of a book would have to be on the basis of itsmerit as a collector's item because the cost of materials andtransportation would not be competitive with electronictransmission for entertainment or education.

Although such prognostications have been made for atleast 20 years while the rate at which we convert forestsinto pulp, or empty oil wells, does not seem to havedecreased, nevertheless all the economic pointers continueto support the basic premise. Thus it is important to placelong-term speculation into perspective in relation to likelydevelopments in the near future. One might otherwise takethe view that North Sea oil was not worth pursuing because

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it was a poor long-term investment! More relevant to mytheme is the case of the video disc. I believe that the sameconsiderations that I have cited above in connection withthe possession of a book will eventually apply to the videodisc. However, I also believe that this product will have asubstantial period of growth before it starts the declinewhich, in addition to material and transportation costs, will,in the 21st century, be due to increasing pressure on storagespace. Thus, however optimistic one may be about thefuture, line and radio transmission are bound to continueto grow at the expense of physically transported 'recorded'messages for both domestic and business communication.

The reasons why the shift to electronic communicationhas been slower than some people have anticipated is thatthe new technologies for radio and cable transmission areonly just becoming viable, while the rising costs of fuel andraw materials have taken longer to affect the balance thanpredicted. By the end of the century we shall see tech-niques such as array signal processing improving the effec-tive use of terrestrial and satellite radiocommunications.During the 21st century further growth in wideband com-munication will have to come from line transmission. Bythat time optical-fibre technology should be able to provideextensive wideband network coverage.

2.1 Free-space radiation

Radio waves provide the most convenient transmissionmedium because they can support high bandwidth signals,they can reach a large number of people simultaneously at alow per-capita cost, and they are the only means of 'instan-taneous' communication with mobile terminals.

One of the popular science-fiction myths, which appearsplausible because of the availability of microminiature elec-tronics, is the tiny television transmitter/receiver providingtwo-way audio and visual communication. Such a devicecontaining a microcircuit camera, a radio transmitter, areceiver, and a miniature television display is almost withinthe capability of present-day technology. Furthermore,mass-production techniques would allow such a device tobe manufactured at a price comparable with that of adomestic television receiver. Yet it is virtually certain that ifsuch a device were produced, legislation would have to banits use as an 'interactive' personal communications terminal.Its widespread use would have to be limited to the recep-tion of broadcast video transmissions because I can envisageno discoveries likely to remove one of the basic constraintsof mobile communication, namely that the total radiospectrum is limited, and there will be no more bandwidthavailable at the end of the 21st century than there is today.

Most of the available radio spectrum is already allocatedand, except in sparsely populated or developing countries,there is not much unused. In order to satisfy future increasein the demand for communication we must

(a) vastly improve the efficiency in our use of the finiteradio spectrum to a tolerable saturation level

(b) look to cable as the means of providing the growth inwideband point-point transmission that 21st-century com-munications will require.The useful spectrum for radio communication lies betweenabout 100 kHz and 20 GHz. Above 10 GHz rain attenuationlimits the useful distance over which signals can be received,and above 20 GHz there are few places on earth where therainfall is so low that radio communication would alwaysbe reliable over distances of several kilometres. Howeverthere are short-distance applications where frequencies

above 20 GHz can be used, and radio frequencies up to100GHz can be generated, modulated, and demodulated onreception. Thus, by analogy with other earth resources, onecan say that there are no longer any 'unknown regions' ofradio spectrum still to be discovered, although regions of thenear infra-red are still somewhat unexplored. The only choicewe have is to use the radio spectrum as effectively as possible,and allocate it as intelligently as we can. Fortunately thereis a fair amount which can be done in both of these areas.

Our present methods of allocating frequencies on thebasis of signals decaying along the earth's surface to a levelgiving sufficiently low cochannel interference is far fromefficient. Leaving aside h i . transmission which is the onlyterrestrial radiocommunication system capable of penetrat-ing remote hostile frontiers, l.f., m.f., and vJi.f. frequenciesare allocated on the basis of a small service area surroundedby a much larger sterilised area where signals are too weakfor satisfactory reception but too strong to allow thefrequency to be used by other transmitters. If one calcu-lates the useful service area as a percentage of the areawhich has to be left unused to keep cochannel interferenceat an acceptable level on a particular frequency and polaris-ation, then one obtains a figure which is generally less than12% for the coverage efficiency.

Up to now, the main feature of communication satelliteshas been their ability to provide a platform for antennashigh enough to avoid the line-of-sight limitations for long-distance wideband communication. However, the possibil-ity of providing a sharply defined service area may becomea more important function of satellites than providing largearea coverage. Although no special attempts have beenmade to use antenna aperture to optimise coverageefficiency, current plans for broadcast satellites give about30% coverage efficiency per channel compared with 12%for the terrestrial stations discussed above. My comparisonis of couse not strictly fair since I am comparing s.h.f. satel-lite allocations with v.h.f. terrestrial practice, but inprinciple the efficient space-division multiplex possible withsatellite-mounted antennas need not be restricted to micro-wave frequencies. Large aperture satellite antenna arraysseem a cost-effective way of solving future radio-spectrumallocation problems.

One does not need to look only to the sky for improve-ments in the use of the radio spectrum. Directional antennasare increasingly used for broadcasts at all frequencies wherethis will lead to more efficient use of the spectrum. Radi-ating cables can be used for communication with mobilereceivers confined to prescribed routes such as motorwaysand railways, or defined areas such as factory sites and ships.

An important step in the right direction is the allowancemade for directivity of receiving antennas in the planning ofu.h.f. television broadcast transmitters. This would bringthe coverage efficiency up to about 30% for receivingantennas having a discrimination of 15 dB, although inpractice this efficiency is not achieved at u.h.f. because ofthe effect of topography.

I believe the future lies in very much greater co-opera-tion between the receiver and transmitter to reduce theeffect of the unwanted signals. An example of this type ofoperation applied to the particular problem of broadcastingtraffic information is the BBC 'CARFAX' system. Here aningenious combination of voice amplitude modulation withf.m. signalling is used. The f.m. capture effect inhibitsactivation of the receiver when burst signals from anyadjacent station show that that station is about to make an

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announcement. Thus stations which are too near from apropagation standpoint but too far to broadcast informationof relevance to the motorist in the next sector are separatedon a t.d.m. basis to enable them to use the same frequency.With this approach, a single frequency could be used toprovide, if required, worldwide coverage yet providinginformation discrimination between transmitters only a fewmiles apart.

Unlike 'CARFAX', which makes few demands onadvanced technology, there are developments in thedefence field where highly sophisticated technology isleading to a quantum step in the degree of co-operationbetween receiver and transmitter. Array signal processingwhereby active antenna arrays are used in conjunction withfast online signal processing will lead to a high level ofwanted-signal acquisition in the face of multipath andjamming. It is only a matter of time before thesetechniques of beam switching and null steering can berealised in consumer products.

For broadcast application, frequency-division multiplexremains effective, but more so if it can be combined withtransmitting and receiving antennas giving a high coverageefficiency. For mobile communication, when there mightbe long periods of silence on individual subscribers'channels, dynamic frequency sharing is essential. Here againthe technology of spread-sprectrum radiocommunicationspioneered in defence applications points the way. Thereceiver searches in a fairly wide band for the signalmodulated by a digital code which is orthogonal to othercodes associated with other subscribers in the same spread-spectrum band. Thus the receiver picks its message from the'noise' represented by the other users of the band whichbecomes saturated only when the signal/noise ratio isunacceptable. Spread-spectrum transmission can lead togreater efficiency and flexibility in spectrum utilisationwith intermittent channel usage.

Even if these technologies became viable for civil appli-cations in the near future, it would probably take until the21st century before allocations could be rearranged toallow spread-spectrum communication to be widely usedoutside the defence sphere.

A defence-sponsored project with civil implicationswhose progress during the next ten years may indicate theextent to which these techniques become generally accept-able is the Navstar satellite system for position location.This uses many of the technologies such as adaptive receiv-ing antenna arrays, spread-spectrum communication, andadvanced signal processing to determine the location of thereceiver from signals received from several satellites whoseposition is precisely updated. There are two extreme waysin which this project could develop. Receivers could eitherremain the province of sophisticated and lavishly equippedusers, such as the captains of battleships and airliners, orboy scouts could be using them in place of compasses in theway that school children today use miniature computersin place of log tables. The actual status of Navstar betweenthese extremes in ten years from now will be a pointer tothe development of many important aspects of radio-communications technology in the 21st century such asdirect broadcasting from satellites, digital techniques forsignalling and modulation, and portable-receiver-equipmentpractice. One further important technological step inmicroelectronics is needed in this area. The tremendousadvance in low-cost, low-power-consumption processingpower must be extended by several orders of magnitude in

speed. Compound semiconductors such as GaAs may makethis possible.

I personally feel confident that communications will besufficiently high on the list of priorities that those transmit-ting information, e.g. the broadcasters, can assume thathighly sophisticated receiving apparatus will be in generaluse. For example, we can expect sections of roofs to con-tain steerable arrays so that most sectors are covered.Architects may bear the position of the geostationary orbitin mind when designing a house, as they now consider thesoutherly aspect. Vehicles will be designed with 'radomes'incorporated in the body structure to give all-round visi-bility for the antenna arrays used for communication andnavigational aids.

There are of course many other current developmentsthat will help to shape future radio communications. Animportant trend is the close linking, by automatic means, ofthe switched-telephone network and personal radio com-munication — to my mind the only way to provide uni-versal radio contact with individuals. This should beachieved by progressively smaller radio cells of highcoverage efficiency, each contacted through the switched-telephone network. (It represents, incidentally, one of theaspects of integrated communication which I have stressed.)The present radio-paging systems are a first step in thisdirection; the combination of high technology and moreefficient spectrum utilisation should enable these personalcommunication systems to be extended to voice contact,but not, as I mentioned earlier, to visual contact.

2.2 The wideband cable network

Our present way of life assumes that wherever we may bewithin a private or public building, we shall always bewithin convenient reach of a socket giving access to .theelectric main supply. In the 21st century, I believe a similarassumption will be valid for a socket connected to a cablegiving access to 'the wideband communications network'.For this to happen there must clearly be some furthertechnological advances, particularly in switching, butoptical fibres go a long way towards establishing the feasi-bility of a wideband subscriber network. As well as newtechnology, there would have also to be some majorchanges in our attitude towards the provision of suchservices. The concept is only viable if it is possible tointegrate the various communication services (includingfuture expansion in broadcasting beyond the capacity ofthe radio spectrum) in such a way that separate access andinterconnecting networks are not required for each service.

Communications over cables that contain glass fibres inplace of copper wires will make the- possibility of theuniversal wideband network with subscriber access apractical reality. Although the bandwidth of metalliccoaxial cables a few millimetres in diameter is sufficient fortelevision transmission over moderate distances, the distri-bution to individual subscribers by cables of this sort wouldmake unreasonable demands on duct space near telephoneexchanges. Thus, although space-division multiplex hascomfortably existed in the local area for voice telephonyusing thin copper wires, it is not practical for widebandtransmission based on metallic cables. The optical cableprovides the opportunity for wideband communication inthe local area with the same degree of space-divisionmultiplex offered by the present-day twisted-pair voice-frequency connections. Since each 'conductor' for the

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information transmitted is a glass fibre with diameter of ahuman hair and protected from damage by a thin coveringof plastic, a cable containing thousands of fibres forswitched local area distribution is entirely feasible. Further,the low-signal attenuation in such cables which has alreadybeen achieved (less than 1 dB/km) has enabled digitaltransmissions capable of handling television signals to bedemonstrated over distances greater than 50 km. Althoughthis is by no means the limit of what could be achieved byrefining essentially today's technology, the present statuswould be more than adequate for local-area wideband dis-tribution without repeaters even in remote districts.

The cost of providing a wideband optical cable servicegiving the degree of coverage obtained by present-day u.h.f.television transmissions would be very large and is unlikelyto be an economic alternative to conventional and satellitetelevision transmission for a very long time. The rate atwhich a wideband network is established will depend on thedemand for expansion in broadcast and television servicesbeyond the capacity of the allocated radio spectrum andthe extent to which two-way wideband communicationbecomes an alternative to travel in the face of rising fuelcosts.

By the 21st century there is every reason to suppose thattechnology will have developed to the stage where the costof fabricating such optical cables will be very much lessthan cables relying on raw materials such as copper andaluminium. Thus, unless a radically new transmissiontechnology emerges, the wideband integrated network willuse optical rather than metallic conductors.

Present-day telephone networks are designed such thatthe current operating the bell, activating the microphone,and energising the earpiece is conducted along the matellicwire which transmits the information. Post Telephone andTelegraph administrations have adhered strongly to thisprinciple, but it is not really compatible with the operationof an integrated wideband network, particularly sinceoptical cables would not normally carry metallic conduc-tors. Although there are advantages in having a communica-tion system which is not rendered inoperative by localelectric power failure, this safeguard will become lessrelevant by the 21st century. Continuity of power supplywill become so essential for the total operation of a build-ing, that a high integrity of service will have to be main-tained by the provision of auxiliary supplies. Emergencycommunication will be possible through the personal radiolink which would doubtless have some degree of diversityof access and, being portable, would of course be batteryoperated. The trend to use even the present limited-bandwidth telephone network for many applications besidevoice communication, such as remote computer access, orfacsimile transmission, means that a separate electricitysupply is already becoming an essential ancillary to thetelephone line. By the 21st century this trend will haveensured that the telephone connection is a means ofcommunicating information, and not the electric powerneeded to operate the terminal.

Perhaps the biggest change would come from an altera-tion in the position occupied by the PTTs in our society.The present situation, whereby PTTs provide a service withtheir own modems and terminals, and charge directly forthe service rather than for the transmission capacityprovided, will become less acceptable in the future. Even ifit were feasible for all terminals at the subscriber end tobelong to the administration and be maintained in the same

way as a telephone subset, this would also become lessacceptable in the future for reasons associated with theprivacy and independence of the individual. As the com-munication network is used increasingly as a means of con-ducting our private and public lives, more emphasis will beplaced on means of safeguarding the information and thenature of the operations at the terminals. The communica-tions administrations will therefore revert to their role of'common carrier', as in the basic postal service where thenature and content of the letter or packet is no concern ofthe postal administration.

Fortunately, in the United Kingdom, the British PostOffice is one of the more progressive among the PTTs inrecognising that digital transmission and data communica-tion are more compatible with common-carrier operations.In other countries it may take more than the 20 remainingyears of the 20th century before the PTTs would beprepared to let the subscriber connect his own modem tothe network!

I am confident that during the 21st century we shouldsee the common carriers providing a very widebandswitched communication network allowing two or moreterminals to be interconnected with each other anywhere inthe world. I am less confident about the timing. Telephoneconnections have been in existence for much longer thanradio transmissions, and yet today in the United Kingdomwe have only about 68% of households connected to low-bandwidth telephone lines, while the wideband broadcasttelevision transmissions are within the range of over 98% ofhouseholds. Further, the actual use has been estimated at95% of homes and this is probably a conservative figuresince it has been derived from the number of televisionlicences purchased. Thus it may be well into the 21stcentury before we can count on the extensive penetrationof a network suitable for video broadcasting and com-munication.

A tariff structure where the administration charges forthe connection, and not for the service, may seem topresent some insuperable problems in view of the widerange of services for which it is intended to use the com-munications media. However, a structure which couldaccommodate this situation would be to charge on the basisof time, bandwidth, distance and degree of individualswitching required. The degree of switching represents thecost of making an individual connection, thus the chargefor N subscribers accessing one terminal simultaneouslywould be MfN of the charge for an individual connectionwhere M is small compared to N. This would, for example,cover the situation where the network was being used forbroadcast reception of entertainment and electronic 'news-papers'. Some PTTs are envisaging 'package deals', in whichthe tariff covers the price of transmission and the serviceprovided. In my opinion it is fundamental to the success ofintegrated communication- that the charges for providingthe communication link be entirely separate from thecharges for the service being communicated. It should makeno difference whether the network is being used to transmitinformation to the gas company about the rate at which asubscriber is consuming fuel; to transmit a computerprogram; or to advise the library that a particular programhas been requested. In each case the PTT charge should bea function of time, bandwidth, distance and switching,calculated on the basis of the cost of providing theconnection. The capability and integrity of the communi-cations network must of course be such that it can

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handle the information dealing with the charging andaccounting for the services provided. But again the PTTshould be concerned with the data transfer operations andnot with the financial transactions.

3 The system and the individual

The picture of communications in the 21 st century which isemerging shows readily accessible communication linksbetween men or machines whether fixed or mobile. Thus,in a pessimistic mood, one might envisage spending thewhole of one's life carrying out a productive and variedexistence without moving from the room in which one wasborn, provided one had adequate terminals connected tothe communications network. More optimistically onemight look forward, for example, to working with a teamcarrying out research into the possibility of life on distantgalaxies, while one is sailing round the world on a yacht. (Ichoose sailing advisedly, since it doesn't require oil!) In thiscase, one might be in contact with a group of people in onecountry using a radiotelescope, and another group in adifferent country studying evolution. From one's yacht onewould be able to consult 'books' in libraries throughout theworld, and one would have access to powerful computers toassist in the analysis of the gathered data.

My reason for pointing out the possibility of theseextreme situations, is to stress the view that the location ofthe individual will have less and less relevance to his activityas communications improve. The resources used by man forhis business or leisure occupation, are unlikely to beassociated with his place of work or residence. We arealready finding that the concept of money being depositedphysically with a particular location of a bank is disappear-ing. The transfer of funds is becoming increasingly thetransmission over telephone lines of data in one computerto the store of another computer. The actual location ofone's assets is becoming increasingly vague. It will not bevery long before a visit to one's bank manager to find outthe state of one's fortunes will be quite meaningless sinceeven if the local branch of a bank consisted of more thanautomatic money dispensing machines, the record of one'sbank balance is likely to be kept in a central store. Thisstore could be interrogated as conveniently from one'shome as from the bank. Thus, the present practice ofidentifying an individual in relation to his location becomesan unsatisfactory means of identification.

The all-pervading computer technology is likely tostimulate the use of a binary code as a universal means ofpersonal identification. This is not to say that radicaldevelopments in analogue signal processing are ruled outforever. Indeed such developments could lead to muchmore efficient electronics but the momentum gathered bythe software 'culture' associated with binary processing willnot readily be reversed. By the 21st century, digital com-munication will probably be so extensive that a world-widebinary identification code for individuals would becomeessential. Since the switching processes will to an increasingextent be computer controlled, the personal identificationcode can be integrated into the routing instruction to thecommunications network. A train of 35 pulses wouldprovide a binary code which would have over 30 billionindividual combinations. Since this is ten times the presenttotal world population, it should be adequate for the periodunder consideration. If the world population shouldincrease beyond 30 billion, then the inadequacy of such acode would be the least of humanity's problems!

Having chosen an unambiguous code which enables theswitching and terminal equipment to identify the individual,the first problem is to solve the man/machine interfaceproblem since this type of binary representation is not partof our culture. It may be that future generations will beable to remember or recognise a binary sequence of thetype mentioned above as easily as we can now remembernames or numbers. However, assuming that our presentalphanumeric representation retains its present position as ameans of communicating intelligence, it will probably beconvenient to continue the practice of identifying indi-viduals by name. It would be quite simple to have thecommunications terminal convert the name typed on thekeyboard into the binary code in the same way thatcomputer terminals perform this function. Since the binarycode resulting from each name must be unique, parents offuture generations will find themselves in conflict betweentheir own preferences for the names of their children andthe constraints set by the availability of combinations whichhave not been allocated. Man's ability to make a virtue ofnecessity will probably solve this problem by ingeniousmeans. If not, people are likely to have two means ofidentification, one related to the code which providesunique identification by the communication system, andthe other derived from the traditional practice of naming.

Let us now consider a scenario based on the technolog-ical assumptions made so far to envisage a communicationscontact being made in the 21st century. A subscriber inEngland would like to see how her husband is getting onduring a business trip to Brazil. (I discuss in Section 5 thefurther technological steps required to make teleconferencea real alternative to travel.) The first action would be toinsert her own identification code into the system. Shemight do this by having the terminal read a card containingher personal code.

Having identified herself, and thereby taking responsi-bility for any charges incurred in the transaction she isabout to initiate, she would press a button indicating visualcontact required and insert the personal code for herhusband. She may well have a card for her husband'spersonal code or have this already preprogrammed as partof the terminal equipment in their house. Thus thesequence of instructions could in the simplest case haveconsisted of pressing only three keys to provide the com-munication system with all the information needed to makethe contact.

The first action probably taken by the system would beto contact the computer containing a record of her bankaccount to check whether she has access to funds to pay forany subsequent transaction. Normally such a check couldbe carried out in a few milliseconds, so that it would becomplete before she would have time to press the nextbutton. As soon as the system received the instructionrequiring contact with her husband as identified by hispersonal code, this request would be passed to a centralprocessor for routing instruction. The store of this machinewould contain information on the whereabouts of everyindividual and convert this into an instruction enabling theexchange to make the connection. Although there is notechnical reason why a single computer should not keep anupdated record of every single individual's movements, thisis unlikely to be the most convenient way of organising thesystem. It is much more likely that people would be'registered' with a store in the exchange associated withtheir home base, and this would be updated. Thus having

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said earlier that geographic location has less significance, itmay still be convenient to associate individuals with certaindistributed processing facilities, although not necessarily adatabase physically near their homes. It would further besensible to associate the personal code with this database.

There are many ways in which the computer's store atthe local exchange could be kept informed of the precisewhereabouts of subscribers. In fact, the difficulty in asociety envisaged with this communication system will beto avoid being instantly located. The system would havehad prior warning of an individual's intention to travel toBrazil as soon as he reserved his transportation. However, inthe unlikely event of the computers which track transportarrangements, accommodation reservations, and finances,all remaining isolated from each other and from the com-munications computers, a self-contained automatic up-dating system could be used for personal location.

I have already postulated that a small two-way voicecommunication device will in future be as essential a part ofour civilisation as the wristwatch is today. The world couldthen be divided into communication cells each a few kilo-metres in diameter (or larger in low population densityregions). The device would report in at regular intervals, sayonce an hour, to establish its association with a particularcell. If the subscriber moved to a different cell, then thenew temporary location would be established, for thatparticular individual, and a message would be sent to thecomputer at his home base updating the information fromwhich routing instructions are based. The traveller, whomight be relaxing in the swimming-pool of his hotel willhear a bleep from his device less than a second after his wifehas pressed the button launching his personal code into thesystem. For the reasons discussed earlier he will be ableto hear his wife but will not be able to see her until hewalks to his hotel room and inserts his personal codecard into the communications terminal indicating that hecan be reached at that location. From that instant his imagecould appear in England and he will be able to see his wifeon a screen in his room. The higher rate of charging for thegreater bandwidth used would of course be initiated as soonas the vision link was established.

A system operating in the way described above wouldmake quite modest demands on the technology in terms ofthe developments which I have forecast. The main problemswould be the sociological ones associated with the freedom,security, and privacy of the individual. It is much easier topredict the benefits of a new technology than its evils. Ifhuman behaviour patterns develop in a way that enhancesthe common good derived from an integrated communica-tions system, then safeguards that protect the individualfrom accidental infringement of his liberty can be fairlyreadily devised. For example, although it would only take ahigh-speed computer a few seconds to examine every singleone of the 30 billion combinations of the 35-bit personalcodes, it would take today's fastest computer billions ofyears to examine all the possible combinations of a codeconsisting of three of these in series, i.e. 105 bits long. Thus,by adding updated codes representing various degrees ofprivacy to the published basic personal code of the indi-vidual, one should be able to provide moderately restrictedaccess to information contained in the computers of thecommunication system.

If human behaviour patterns develop in a way to exploitthe weaknesses and vulnerability of the integrated com-munication system, then it is unlikely to develop along the

lines suggested. The system is vulnerable to criminalelements, and new methods of law enforcement would haveto be devised. The more extensive the communicationsystem, the more it is vulnerable to abuse by governments,as well as by criminals, and herein lies the greatest threat tothe individual. Furthermore, commercial pressures mightencourage people to restrict their own access to the net-work. Clearly, if a very large percentage of people felt itnecessary to impose the equivalent of an 'ex-directory'restriction on their personal codes, then the concept of theintegrated communication system would be eroded andeventually break down. My hope is that improved com-munication will steer man's instinct for self preservationtowards a greater sense of responsibility for the communityat large.

4 The influence of education

Having predicted fairly confidently the technological trendsduring the next 50 years, I must confess a feeling of uncer-tainty in one important area. I am not sure to what extentman will adapt his culture to suit the machine, or devisemachines to perpetuate his culture. This trend, whicheverway it goes, will have a major effect on the development ofthe communications media. Unfortunately, the lessonsdrawn from past experience are contradictory. On the onehand man has accepted as part of his basic training thedevelopment of a highly sophisticated interaction with themotor car, in which most unnatural actions are performedvirtually subconsciously. Yet in the 50 years during whichthe typewriter has been widely available, a much smallerpercentage of people have learnt to type than to drive.

It may be that the ability to drive a car is considered tobe a completely new and valuable attribute to mankind,whereas being able to type is considered to be only a minorand not very worthwhile variation of a method of. com-munication which has been in existence for hundreds ofyears. It is not clear whether it is the inertia of the educa-tion system or uncertainty about the value of learning totype that has limited its adoption. Whether it is to be dis-played as hard or soft copy, handwritten alphanumericmaterial cannot be transmitted as efficiently as keyedcommunications which can be sent directly in dense code.Even letters in typewritten form should lend themselves toelectronic transmission with a time-bandwidth productapproaching that of directly keyed messages, since patternrecognition processes can work efficiently with standardfonts. It remains to be seen whether the widespread avail-ability of electronic mail and computer-access terminals willencourage the teaching in schools of the manipulation ofalphanumeric keyboards. If not, then much more emphasismay be placed on character recognition technology so thatthe terminals can read handwritten communications orinstructions.

It is possible that education methods may concentratevery heavily on developing man/machine interaction. Withincreased leisure and improved communication, educationwill become a lifelong rather than a childhood activity.However, the teacher will to a greater extent becomeaugmented by the communication terminal used in aninteractive mode, particularly with the older pupils. Thiscould lead to the development of a completely new language,one devised to bridge the gap between the man and themachine. To illustrate the point, let us assume that all theadaptation is carried out by man rather than by the machine.

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In this case man might learn to write, type, speak, and readin binary code. Writing would present very little difficulty,since one would only have to learn to produce two easilydistinguishable marks representing the ' 1 ' and '0'. Typingwould be even less of a problem. A keyboard in which onefinger would operate the 0, and the second finger the 1,would probably be more suitable for rapid transmission ofa binary code. Speaking would be slightly more difficult,but no doubt the voice could be trained to articulate apulse train using perhaps two different notes to distinguishthe 1 from the 0. All this could be rather slow and tedious,so that if we did learn to 'speak' to computers we wouldneed to invent some short cuts which would provide abetter match between our anatomical limitations and thespeed at which data can be received.

Reading a binary code is a much more fascinatingconcept. The human capacity for pattern recognition hasbaffled scientists for many years. It should be quite possibleto devise a computer language such that the human beingcould recognise words in binary code as readily as otherforms of writing. It is very unlikely that if man did in factmake an attempt to speak the language of machines, hewould choose the simple binary code. It would probably beworth changing the architecture of the machine to bring thetwo closer together and to ease the introduction of redun-dancy and error correction.

For the small mobile terminal, the advantage of beingable to communicate in binary code is apparent. If hisdevice were the size of a wristwatch, then there wouldhardly be room for the ten-button keyboard, and a fullalphanumeric keyboard would be out of the question. Atwo-button binary-keyboard transmitter would be quitefeasible; alternatively, the articulated binary code could bereceived by the microphone.

My own belief is that the trend will go more in the direc-tion of the machine adapting to man. It is interesting tonote that even the present-day l.f., m.f. and v.h.f. radioreceiver presents the average person with sufficient difficultyin station selection that the BBC is considering the use ofdata signalling combined with the audio modulation to givethe station a 'label'. The receiver would search out the bestsignal bearing the 'label' of the station selected on the basisof an instruction which could be as simple as moving a lightpen across a bar code printed in the Radio Times. Devel-opments of the present-day speech synthesis and recogni-tion process will become so small and cheap that we may befurther discouraged from making the effort to adapt ourculture to ease the interaction with machines.

Another educational trend which conflicts with themore extensive availability of communication is the diver-gence rather than the unification of language. Even in acountry as small as the United Kingdom, there is a tendencyfor the re-establishment of regional languages. Whereas onemight have expected the availability of broadcast enter-tainment commonly available over several continents toencourage some unification of language, exactly theopposite seems to be happening. The French are refiningtheir own language and discouraging the use of inter-nationally understood phrases. Thus, at the same time thatcontinent-wide broadcasts from satellites would be availablefor entertainment and education, language problems wouldprevent these from being widely accepted. If this trendcontinues, one solution would be to provide several soundchannels in different languages to accompany the visualmaterial which would have to be multilingual in style.

Artistically this would be a poor extension to nationalprogrammes, and much worse than 'mid-Atlantic' produc-tions.

5 The communications terminal

One of the biggest differences between communications inthe 21st century and the present will be the dissociationbetween the nature of the transmission medium and theterminal. Today there is a low probability that the tele-phone wires entering a house are connected to anythingother than the conventional handset, or that the uJi.f.aerial is connected to anything other than the standardtelevision set. However, we are now seeing several examplesheralding the start of this integration. CEEFAX receivershave been demonstrated with hard-copy facility, thuscombining classical examples of instantaneous and'recorded' communication. In Viewdata, the televisionreceiver is connected to the telephone line. Subaudible datamodulation of radio broadcast transmissions is beinginvestigated by the electrical supply industry with the BBCas a means of remote switching of storage heaters etc.Direct-debit facilities are appearing at point-of-sale stationsusing magnetic data on credit cards to interrogate andinstruct the computer at the customer's bank. With theavailability of the wideband communications network, thefunction of the terminal will be to achieve the desired man-machine or machine-machine interface, rather than toterminate a particular transmission medium dedicated to aspecific communications function.

Clearly the complexity of the switching operations in anintegrated network which provides a variety of services tothe subscriber needs to be many orders greater than that oftoday. One extreme situation might be that a single verywideband line (say an optical fibre with two-way transmis-sion at two optical wavelengths) would provide all servicesto fixed locations leaving the radio spectrum free frommobile users. All signalling and information transfer wouldgo along this line connecting the subscriber to the exchangewhere the selection processes would be activated by thesignalling commands. It will be clear from Section 2 that Ido not believe that things will turn out that way. Financiallimitations as well as the sheer inertia of developments thathave to be compatible with what has gone before will resultin an evolutionary change.

I envisage that for a very long time the average subscriberwill have a number of parallel connections with the 'wide-band network' some of these derived from radio, bothterrestrial and satellite, some from lines intended to havelimited switching, some with access to the trunk network,and finally one connected to the twisted-wire pair becauseno-one will want to dismantle it! There will thus be adegree of distributed switching whereby the intelligentterminal performs the first stage of selection by searchingfor the connection appropriate to the service required.There would be a continuous grading of transmission meanswith a bias towards cable in high-population density con-urbations and a bias towards radio for remote or mobileusers. This distribution will of course change in favour ofcable during the course of the 21st century. Techniquessuch as the BBC's signalling in radio could be used by theterminal to select the appropriate radio or cable outlet.

It will already be apparent that in my view a large partof the demands of the communication network will bemade by machine-machine communication. These terminals

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will depend very much upon the nature of the machinesassociated with them such as autopilots, process-controldevices, and accounting systems. To speculate on the natureof these terminals one would have to consider future devel-opments associated with the machines themselves, and thisis outside the scope of this paper. I propose therefore toconcentrate on the domestic end of the communicationsnetwork.

My basic premise is that the communication networkwill deal with 'all deliveries' that are concerned with thetransfer of information rather than the transfer of materialgoods. Thus a fuel such as gas would be physically deliveredin the pipe, but the information on how much gas has beenconsumed over a given period would be transmitted overthe communications medium and not by a man calling toread the meter. The 'postman' would deliver a packet con-taining a piece of wedding cake from distant relative, butthe 'letter' describing the wedding and containing thephotographs would be sent to the domestic terminal overthe communications network.

The two examples chosen above represent the transferfrom manual to electronic communication which is likelyto become established first. This would be followed by thereplacement of the 'paper-boy' for the delivery of news-papers and magazines. Eventually, there are unlikely to beany technological obstacles to extending the principle tothe delivery of all the other modes of information transfer,such as, in today's terms, books, gramophone records, andcine films. The extent to which this would happen willdepend very largely on the relative cost of the raw materialswhich are used for the manufacture and transportation ofthe 'recorded' communication compared with the transmis-sion and presentation costs associated with the electronicmeans of delivery for such recorded communication, whenadded to the initial software costs.

The role of the 'broadcasters' may eventually divide intotwo streams: that of providing the instantaneous informa-tion, news, sport, 'live' outside broadcasts etc, and theprovision of 'on demand' information and entertainment.The latter mode might be regarded as a combination of thepublisher and the library functions. However, for a verylong time the cost of an individual switched connection islikely to be vastly more expensive than broadcast connec-tion, thus the subscribers may prefer the 'programmes'selected by the 'libraries'; in other words something close topresent-day broadcast services for both news and enter-tainment.

The consideration which will determine the extent towhich 'recorded' communications are delivered by thecommunications network is the value placed on the posses-sion of an 'original'. The more extensive the communica-tions system, the more remote becomes the contactbetween the communicator and the communicatee whoseconfidence in the authenticity of the original must not bedestroyed by censorship or distortion in the communica-tion system. For this to apply extensively, man will have todevise means of interacting with the system in such a waythat it is possible to transmit proof of authenticity which isas acceptable as a written signature. Such a process is verylikely to be well established by the beginning of the 21stcentury, since its development will be stimulated bybusiness-communications methods which will by then havebeen in use for a couple of decades.

With such a system, the communications industry wouldbe primarily concerned with the presentation of the infor-

mation conveyed in a volatile form for temporary localstorage. A subsidiary 'luxury' industry would be concernedwith the nature and quality of the presentation package,and its direct association with the originator. This has itstraditional parallel in, for example, the distinction betweenprints obtained directly from a wood engraving and photo-lithographic copies of these, or the deliberately limitededition of a book using high-quality materials, and the'paperback' edition. Economic considerations, the scarcityof raw materials, and the improved access to the informa-tion contained in the 'originals' will cause the divergencebetween the methods used to convey recorded communica-tions to many individuals, and the methods used to preserveinformation for posterity. Under these circumstances, thedomestic communications terminal would be required tohandle most of the 'recorded', 'instantaneous' and 'inter-active' communications. The role of the bookshop orgramophone record shop would be closer to that of ajeweller than that of a purveyor of information or enter-tainment. With the separation of the motivation for thepossession of a permanent record and of the desire forinformation, the electronic 'libraries' of the future wouldassume a more important function than our presentrepository of books.

A further development of electronic storage methodswill not only enhance the facilities offered by the com-munication terminals but will be essential for the efficientuse of bandwidth. Consider, for example, the transmissionof one static page of alphanumeric information by aconventional television system using a bandwidth of5-5 MHz. Assuming it takes 30 s to read the page, the time-bandwidth product used to transmit the message is165 MHz s. Only the first twenty-fifth of a second wasnecessary actually to transmit a picture of the page, the restwas updating a static image to give the brain time to absorbthe information. A picture store would remove the need forupdating transmission and enable the time-bandwidthproduct to be reduced by a factor of 750 to 220 kHzs. Since.the information is in alphanumeric form it can be trans-lated to a dense code such as used in CEEFAX, for examplewhich would only require 8 5 kHz s to transmit the page.

Although our usage of time-bandwidth product percapita will greatly increase in the 21st century, I cannotenvisage circumstances under which it will not be worthincreasing the efficiency of usage. It will be a function ofthe communications terminal to carry out the signalprocessing for transmission and reception which give thebest balance between bandwidth reduction and the com-promise between what is considered essential and what isconsidered redundant information.

This compromise can be illustrated by consideringthe example discussed above. The loss in introducing apicture store to display the page for 30 s was that if someimportant newsflash came 10 s after the page was firstdisplayed, the viewer could not see this for another20 s — a small price to pay for about three orders of magni-tude saving in time-bandwidth product. The further savingintroduced by the dense code may be more controversial.If the original had letters in a font which contributed to thequality of the message, it would be a loss; if it were, say,the stock-market report it would be acceptable with astandard format.

This argument can be extended almost idefinitely byassuming the use of signal processing and storage to effectbandwidth conservation at the expense of'authenticity'.If

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one is prepared to accept a loss of the 'instantaneous'nature of the message, the delay could be used to share thebandwidth not required by static imagery with those havingrapid changes. In sound, one could broadcast a dense codeused in conjunction with speech synthesisers at the receiverto articulate the news or have a MOOG operated by datatransmitted in a few milliseconds and slowly dispensed bythe local memory to give an hour's pop concert! I am ofcourse not seriously proposing a 21st century version of thepianola, but merely trying to express some views of thetype of compromise decisions technological progress maypresent.

It is in fact much more likely that the improved efficiencyderived from devices such as memory at the receiveterminals will be used to enhance the quality of presenta-tion of information. It is rather surprising that in this era ofvery rapid technological progress there has been hardly anychange in the terminal transducers at the extremities of theelectronic communication systems. The microphone andearpiece of today's telephone handset are very similar tothose used at the end of the 19th century. The television-camera tube, cathode-ray tube display and loudspeaker areessentially the same devices as used when the service startedin the 1930s.

Clearly, where the technology is adequate there is noneed for change. I feel that to a large extent this applies tosound but not to vision. A stereo or quadraphonic hi-fisound presentation is close to saturating the capabilities ofthe human aural channel. The present c.r.t.-displayed tele-vision image is a long way from saturating the visualinformation channel of the human being. This situation ishardly surprising since the serial communications methodsof electronic systems match those of the mouth and earwhich work directly with a serial transmission medium,whereas the eye works in a parallel mode. Thus, for visualcommunication, the serial electronic communicationssystem requiring the dissection and rewriting of the imagepresents a severe bottleneck as far as the eye is concerned.With the prospects of satellite broadcasting and optical-fibre cables, the neck of this bottle could be much larger,but paradoxically no display technology has so far emergedwhich could do justice to the large high-definition imageswhich could soon be transmitted. Until such displays areavailable there is probably not much incentive for departingfrom existing television transmission formats where there isstill considerable room for improvement within the presentframework.

Energy problems rather than the motivation for improvedentertainment presentation may stimulate the developmentof new display technology. The telephone, television andelectronic mail (which in the business sector is already withus), have all reduced the need to travel. However, I believethat it will need a visual communications medium thatcomes as close to saturating the capabilities of the eye, aspresent sound transmission comes to saturating the ear,before electronic communications could become a seriousalternative to meetings requiring travel.

Technologies for achieving this 'visually saturating'communications system are not yet here but they may bequite close. Initially we will doubtless stay with serial

transmission but if we make the step to modulating anddetecting coherent optical transmission, we can get manyorders closer to exploiting the 'r.f.' of 1014 Hz than cur-rently projected fibre-optic communications systems. Atthe terminal end, large matrix-addressed displays could beused, and technology could be devised for cost-effectiveproduction (although, as the last 40 years have shown, theelectron beam is hard to beat as a means of sequentiallyaddressing a large area with high resolution). Here again,coherent optics could provide a convenient way of scanninga light beam by using a phased array. Although this couldstill need matrix address, the matrix could be a small solid-state device compatible with low-cost microelectronictechnology, unless large-area active device technologybecomes viable.

Eventually we would find means of transmitting, andswitching, visual information in the parallel mode such ascan currently be done over short distances with fibrebundles. Such transmission combined with coherent opticsWould allow large'area holograms to be displayed. Thedisplay could consist of a wall having an array of bundleradiators each capable of resolving sufficiently high spatialfrequencies to give a wide angle of view. Although thebandwidth requirement would be high, it is not as enormousas it might seem. The information would control therelative phase of the 'point sources' in the bundles and the'difference' information for the other bundles whose trans-forms are all related since they project slightly differentviews of the same image. In addition there would be theusual triplication for colour using red, green and bluesources with no mutual phase relation to avoid interference.

I have not given much thought to the problem of the'camera' for such a system except to consider the fact thatmost scenes are lit by incoherent light. For teleconferencesthis problem could be readily solved by a special lightsource in the room, and the same would apply to studioproductions. An extension of this could be used for naturallylit scenes assuming the availability of sophisticated signalprocessing at the sending transducer which would of coursehave to be a fairly extensive array. Such an array couldsense luminance and chrominance based on natural lightand phase based on a special coherent source (not necessarilyvisible). Fast online signal processing would arrange theinformation for transmission in a way that the data for dis-play could be extracted on reception.

Such a system, although far beyond the bounds of thetechnology of the 20th century may be no more of a tour-de-force in the 21st century than microelectronics orsatellites were in this century. The realisation of such asystem would come as close to saturating the visual sense asI can envisage.

6 Acknowledgments

This paper is an expression of my personal views but I amgrateful to the Director of Engineering of the BBC forpermission to publish, and to my colleagues for helpfulcomments.

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