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White Alice System--Design and Performance

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3 Author(s)
Durkee, A.L. ; Bell Telephone Labs., Murray Hill, N.J. ; Metcalfe, D. ; Tidd, W.H.

White Alice is an extensive communications network covering the entire state of Alaska. It provides essential defense communications as well as service for other government agencies and civilian commercial service. Both telephone and telegraph channels are provided with capacity for future growth. The Western Electric Company, as prime contractor for the USAF AMC, undertook the engineering, procurement, and installation of the electronic equipment as well as construction of some of the sites. The Bell Telephone Laboratories participated in the basic systems engineering and furnished consulting assistance in new scientific areas. New designs were made or supervised by the Laboratories. The White Alice system plan is based on the study by the Bell System of the communications needs of the area. Radio transmission was chosen for the majority of the routes. Wire and cable were considered either unreliable or impractical in the Alaskan terrain and climate. Where several hundred voice channels were required, microwave line-of-sight radio was used. For the majority of the links, tropospheric beyond-horizon transmission was used because of the economy and simplification of maintenance and logistic problems. The transmission objectives for the entire system were a median noise in the worst month of 38 dba and a maximum of 1 per cent outage in the worst month. These objectives were for 4000-mile circuits and were prorated to each link. The microwave portions of the system were engineered in the same way that has been used previously. Tropospheric beyondhorizon was a relatively new mode of radio transmission and the engineering procedures were less well defined. Propagation experience from a year-long test in Newfoundland, in addition to research by other groups, were used as the basis for the system engineering. These data include variation of signal strength from day to day and seasonally, the effective gain of the large antennas employed, the characteristics of the rapid fa- ding typical of tropospheric propagation, and the effects of geographical profile and separation of the stations. Towards the completion of the project, comprehensive transmission tests were made of many of the links of the system to determine that the design objectives had been met. In particular, a 2400-mile circuit traversing much of the system was tested. The transmission stability and noise performance over a 30-day period was well within the limits set in the objectives. Teletype and voice performance were eminently satisfactory. White Alice has been operating continuously since it was turned over to the Air Force in March, 1958. Its reliability has been gratifying to the military and other agencies using it. It is certain to be a significant factor in the development of this last frontier.

Published in:

Communications Systems, IRE Transactions on  (Volume:7 ,  Issue: 4 )