This monograph reviews events, circa 1920-1960, leading to the development of spread-spectrum communication systems. The WHYN, Hush-Up, BLADES, F9C-A/Rake, CODORAC, and ARC-50 systems are featured, along with a description of the prior art in secure communications, and introductions to other early spreadspectrum communication efforts. References to the available literature from this period are included.

The Origins of Spread-Spectrum Communications

http://ieeexplore.ieee.org/iel5/35/23781/01091406.pdf

Why is the army interested in spread spectrum

This paper presents the results of a study to determine the satellite capacity enhancement obtainable by using syllabic compandors. Syllabic companding applied to the speech channels of tDDM-rm carriers can increase satellite capacity by as much as 100 percent, depending on the number of channels per carrier. Syllabic compandors presently produced by integrated circuit technology are small and inexpensive. Compandors permit a higher level of satellite circuit noise and hence an FM index (and bandwidth) which is smaller than that required for uncompanded channels. The results presented in the paper are based on compandor advantage measurements and singleand multi-channel amplitude distribution measurements for both companded and uncompanded speech signals. For data transmission, it is estimated that about 2-dB degradation may be encountered when long terrestrial access circuits are interconnected via a companded satellite circuit for international transmission. *This paper is based upon work performed at COMSAT Laboratories under the sponsorship of the International Telecommunications Satellite Organization (INTELSA r).

Enhancement of FDM-FM satellite capacity by use of compandors

GEOSYNCHRONOUS satellite systems designed specially for providing domestic communications to geographically large rural areas are currently under investigation by several countries. The paper presents some significant technical considerations for the economical provision of both telephone and television services to such areas. Satellite launch vehicles, operating radio frequency band(s), spacecraft communications implementation and earth station engineering are discussed.

R. Briskman

Papers

Domestic communications satellites: System considerations for rural areas