radio relay lines
Design procedures of severely errored second ratio and unavailability ratio for radio relay routes was investigated.
There are some methods for quality and availability calculation. Designers know well the International Telecommunication Union method. Some national calculation methods summarized in a unit method developed with participation of the author are available.
The aim is to define the prediction accuracy of these methods. To this effect the calculation results were compared with the experimental data for 21 hops operating in the frequency ranges of 18 and 23 GHz. Area of measurements covered St.-Petersburg and Leningrad region. The experiment was carried out within two time periods: from 28 October 2007 to 26 November 2007 and from 8 May 2008 to 30 September 2008. The last measurement period covers the summer season that in the region is considered the worth one from the viewpoint of propagation environment effect.
The number of severely errored second and unavailability seconds was registered every day at each hop (in two directions: and ) during the whole measurement period. That finally allowedus to define necessary ratios.
The measurements fulfilled have shown that the worth year period for radio relay routes operation in St.- Petersburg and Leningrad region is from the end of June to the beginning of September. At that it is clear that propagation environment contribution to the considered ratios values is negligible from October to May.
The national calculation method in comparison with ITU method provides more reliable prediction for quality and availability parameters for radio relay routes of 18 GHz and 23 GHz located on the territory of the region considered. But this conclusion should not be applied to other territories without preliminary experimental tests.
The measurements have shown that approximately at a half of hops the worth parameters correspond to direction and at another half the direction was the worth. Thus, at calculations it is possible to use values of the central frequency of a range and antenna gains corresponding to it.