OVERVIEW

Many developments in the communications field have contributed to the recent growth of digital microwave system applications. Some of the most important of these developments are an ever-increasing rate of growth in the amount of telephone traffic that can economically be handled entirely by digital methods; demands for new services such as facsimile, digitized television and high-speed data; demonstrated high radio-frequency (RF) spectrum efficiency for mixtures of data; digitized voice traffic; and the opening up of frequency bands above 10 GHz, which are more viable for digital than for analog transmission methods.

During the late 1970 s the countries most active in the application of digital line-of-sight microwave systems (digital radio systems) were the United States, Canada, Japan, the United Kingdom, Italy, France, and Norway. Of these, Japan is probably the world leader in operating high-capacity digital radio systems. For example, by 1977 one Japanese manufacturer had over 1500 such transmit/receive terminals installed for operation [1.9]. In Europe, Italy probably leads in the field of digital radio by having over five hundred 13 GHz digital transmit/receive terminals in operation. Canada is committed to an 8 GHz all-digital high-capacity system, of about 6000 km in length, that will stretch from the Atlantic to the Pacific coasts. Initially, the major application in the United States has been to interconnect pulse code modulation (PCM) transmission links between switching centers. The Federal Communications Commission (FCC) in the United States has issued well-defined rules for digital microwave systems. These rules, summarized...