Estimated Outage in Long-Haul Radio Relay Systems with Protection Switching

In order to achieve the high reliability demanded for long-haul TD and TH microwave radio relay systems, frequency diversity by automatic channel switching is used as an effective means to protect services against outages due to propagation, equipment failure, and maintenance activity. In this arrangement, each radio relay route is divided into a number of switching sections. One or two of the total number of radio channels in a given band are designated as protection channels. The automatic protection switching system uses protection channels to replace failed or otherwise unavailable regular channels by operating either IF or baseband switches at the transmitting and receiving ends of the switching section. The first protection switching system developed for use with the long-haul TD-2 system (TDAS) is capable of protecting up to five regular working channels with one protection channel ( 1 x 5 switching). 1 It was first placed in service in 1953, and it accounts for about 45 percent of the long-haul radio switching systems now in the field. Another frequency diversity switching system was developed for application to the 6-GHz TH-1 system which was overbuilt on TD-2 1455