Practical residual error rate of extremely long microwave links

The residual error performance of a nonstandard, extremely long (143 km) operational microwave radio-relay link (SDH STM-1) has been measured throughout 60 days of the usually worst period of the year (summertime), in order to find out how practically achieved values compare to the predictions calculated according to 1TU-R recommendations that have been proposed for much shorter links but only supposed to be valid for the longer ones as well. The error floor has been considered as block-error-rate, with the reference to the evolution of standards from the bit-error-rate based (G.821) to the block-error-rate based ones (G.826). The results of the extensive measurements campaign encourage the conclusion that, for the well designed radio-relay system, it is realistic to expect the error floor to be well within the predicted limits even for extremely long hops.