Consistence between the block-error and the bit-error based residual performance of practical SDH microwave-links with extremely long hops

The error performance of a non-standard extremely long (143 km) operational SDH microwave radio-relay link has been extensively measured throughout 30 days of the usually worst period of the year, in order to investigate the consistence of practically achieved residual error performance with the migration of its defining parameter from the residual-bit-error-ratio (RBER) to the background-block-error-ratio (BBER), as coming out of the evolution of the relevant ITU-T performance standard from the bit-error-rate based to the more stringent block-error-rate based one, where, in turn, the latter practically does also include into the performance evaluation periods of deep fading. The close matching between the actual BBER-based RBER estimation and the native RBER objective found even on such a long hop, most likely is to be attributed to the space diversity, as the ultimate and most worthy protection measure in this case.