A Brief History of Microwave Radio Fixed Point-to-Point (Relay) Communication Systems

This chapter presents a brief history of microwave radio fixed point-to-point communication systems. The first known message relay system was created by the Egyptian king Sesostris I about 2000 BCE. Digital transmission systems continued to advance using the basic concept developed by Polybius. In the late 1940s, all fixed point to point microwave relay systems used analog frequency modulation (FM) transmission. Frequency division multiplex (FDM) was used to aggregate the 4-kHz-wide analog telephone channels for transmission over FM radios. The new millennium shows a significant increase in adoption of Internet protocol (IP) technology for interconnecting all forms of digital transmission. The user community drop and edge connections are rapidly transitioning to IP. IP, with its evolving Quality of Service features, is the new wave of digital transmission. Fixed point to point microwave network evolution mirrors that transition.