Broadband Cable-Satellite Connection Key Link for Business Communications.
Much has been said about the evolution of the United States from an industrial society to an information society. Just as the number of people working in industry started to outnumber the people working in agriculture in the early 1900s, the people working in information occupations now outnumber those working in industrial occupations. We have indeed encountered "The Third Wave" explored in Alvin Toffler's book.
Information and the way it is used will be the key strategic variable in many businesses. For this to happen, effective information transfer can no longer be constrained by a communication system designed for voice transmission.
With the advent of the communications satellite, large amounts of information can be easily sent from one city to another. The satellite carriers have made a significant investment in earth stations for intercity distribution of information. The problem lies in distribution of this information to the local user. The cable that is now being laid for distribution of television can be used for a substantial part of this local distribution. The linking of satellite earth stations with cable television distribution systems offers many new opportunities as the information society develops.
A number of large businesses are essentially information-based; included are banks, insurance companies, investment companies and stock exchanges. Their business depends on gathering and assimilating large amounts of data. Office automation will allow the information to be processed and stored electronically, with only summary information being recorded on paper. Communication and transfer of this information can be accomplished by the interconnected cable and satellite systems described in this article.
Although productivity improvements have occurred in the agriculture, manufacturing and service industries, productivity improvement in the office has been slow. However, improvements are now being made to change this situation. Communicating word processors, facsimile devices, computer-to-computer links, voice messages stored in digital format, integrated voice and data PBX, and intra-facility communication networks are now available to upgrade office systems. A sophisticated business communication system allows charts, budget, last-minute schedule changes, press releases, contracts and photographs to be transmitted quickly and reliably. Many people will be able to work at home connected by cable to their office. Executives attending out-of-town meetings and salespeople on the road will be able to have immediate and accurate access to information back at the home office. In the future, a person will be able to substitute teleconferencing for some business travel. The possibilities seem unlimited.
With office automation moving ahead, satellite common carriers have recognized business communications as a viable market. These satellite carriers are shaping intercity business communications with their concept of shared earth stations. Digital satellite carriers offer business customers a capability to transmit vast amounts of data, voice, electronic mail and other business signals from the earth station up to the satellite and back down to another earth station. Cable is a logical choice of a medium to distribute this data from the earth station to the business in each city.
Satellite and cable systems offer increased communications capabilities for text, facsimile, data transmission, voice, visual aids and videoconferencing. In the past, text transmission has been handled pricipally by telex, which is slow and has a rudimentary character set. Telex is being replaced with communicating word processors that allow typewritten material to be transmitted from one machine to another at high speed. Much of the transmission and storage is accomplished electronically, thus creating tremendous communications needs. With a cable/satellite communications system, a secretary can type a letter, attach the appropriate electronic "address" and send a copy directly to another terminal at a distant facility.
Graphs, pictures and photographs do not lend themselves to character transmission and are better sent by facsimile. In order to obtain high resolution and transmit at a rate of one page per second, the bit rate needs to be of the order of 256 kb/s. This high data rate, which is available on the satellite, creates the need for a high-capacity local distribution system such as cable can provide.
The next step beyond communicating by voice and still pictures is conferencing using full-motion video. Point-to-point videoconferencing now makes economic sense. Many national sales meeting have been set up with regional salespeople coming to local auditoriums where earth stations are installed or have been temporarily set up. The salespeople view the program material on large television screens and respond to the presenter by phone.
Point-to-point teleconferencing is very costly when using full-motion video because of the large bandwidth required. Analog video requires one-quarter to one full transponder of a satellite. The use of this much capacity for a normal business meeting would be excessively expensive. hence there is a need to digitize the information and reduce the data.
NTSC color video can be digitized at the rate of about 90 Mb/s with no visible degradation. Removing redundancy allows a video signal to be sent at 20 Mb/s with insignificant loss in video quality. When the motion is limited and the camera is fixed, it is possible to reduce the bit rate to 6 Mb/s with limited loss in quality. Current digital technology has reduced the bit rate to 1.5 Mb/s while maintaining reasonable cost. As new devices for video coding are developed and as the cost of travel increases, business teleconferencing will become common-place.
Consider next data transmission. Large computers can manipulate data at rates of 1 Mb/s of faster. Efficient resource sharing, computer backup, file protection, core diagnosis and other factors make it necessary for distant computers to communicate with-each other. Transmission at Mb/s rates is required for computer communications in the future.
Since the office of the future will be integrated electronically, a number of scenarios for linking the equipment and people become evident. One scenario sees the hub of the automated office being an integrated voice and data PBX. The PBX permits users to transmit, switch and store voice and data. Another possibility has local networks connecting office machines, digital telephones and intelligent terminals or work centers. These terminals process and display data, text, pictures and graphs. Regardless of the method, there will be a need for rapid communication of information within the office and from office to office.
Satellite business carriers have made great strides in the intercity portion of satellite business communications. Carriers such as SBS, American Satellite, RCA and Western Union have provided increasingly sophisticated business communications facilities for their customers. American Satellite, through its satellite data exchange (SDX) service, has specialized in providing voice and data communications to small earth stations located on end-user's premises. American Satellite now has about 100 earth stations operation. RCA Communications is providing data, voice, facsimile, slow-scan TV and teleprinter service called "56 Plus." Western Union also offers a similar data service to its customers. Voice channels can be provided over these digital links by using phase-code modulation (PCM) or continous-variable-slope delta modulation (CVSD) encoding.
Communications of business data by satellite offers a number of advantages. The telephone system normally restricts data transmission to maximum speeds of 9.6 kb/s. However, data rates of 50 Mb/s can be transmitted by satellite.
The telephone network can be expected to produce, on the average, one error per 100,000 10sup.5 bits transmitted. Elaborate error-checking-and-correcting schemes, which reduce efficiency, have been developed to allow the use of the telephone channel. Error rates of fewer than one error per 10,000,000 10sup.7 bits are easily accomplished using satellite communications, with error rates typically lower than 10sup.-8 with simple error-correction devices.
Having achieved a long distance network, the carriers are then faced with the need for local distribution to their customers.
The options available are the telephone plant, broadband cable and microwave links. Prior to the development of pro-competitive policies by the FCC, local distribution was dominated by the local telephone companies. With the settlement of the AT&T antitrust suit and the development of alternative local distribution technologies, a new business opportunity, "telephone bypass," has emerged. This bypass industry has been dominated by: Digital Termination Services (DTS), which use private microwave; cable system; and radio common carriers, which use cellular radio. The local telcos offer data distribution primarily by twisted pair, although some progressive companies are working with fiber optics, broadband cable and cellular radio.
Independent of whether the local distributor supplier is a bypass company or the telco, broadband cable has some advantages over the other technologies for completing the satellite communications link. Like the twisted-pair telephone plant, broadband cable is a proven existing technology. However, broadband cable, like satellite, offers excellent bit-error-rate performance in addition to being very cost effective for high data rates. When compared to microwave and radio, the inherent closed system (shielded cable) nature makes broadband cable less susceptible to external problems such as line-of-sight and radio frequency interference.
Also, broadband cable systems do not require the sophisticated control schemes used in cellular radio and private microwave DTS.
Overall, broadband cable is flexible, available and cost effective as a local data distribution medium. Broadband cable meets the service need for intracity data communications for both the telco and the private network industry.
Cable television systems can play an important part in the intracity distribution of voice, data, electronic mail, teleconferencing and other business communications.
In only a few years, cable has gone from an auxilary system for delivering television to areas with poor television reception to the most versatile and economical means for mass distribution of many channels of video entertaiment. The next equally dramatic step will involve cable operators finding new customers for using the cable to distribute business communications within the city. These customers will include satellite communications carriers, large corporation, financial institutions, municipal agencies, hospitals and university complexes.
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|Author:||Beakley, G.; Best, A.|
|Date:||Mar 1, 1984|
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