Threshold Degradation of Digital Receivers due to Interference in Fixed Wireless Access Networks

The legacy very long microwave backbone links have been recently systematically replaced by fiber-optical connections where terrain conditions and the built environment made it possible. Thanks to the high capacity optical access points, the majority of fixed radio hops became shorter. In cities the microwave and millimeter-wave $(\mu/\mathrm{mm}\mathrm{W})$ links are very short (typically $5\mathrm{~km}$ or even shorter). The density of the Fixed Wireless Access (FWA) networks is increasing. Actual 4G and 5G mobile systems and future 6G mandate strict bit rate and latency requirements. New millimeter-wave bands $(V,E,W$ and $D)$ offer wide radio bandwidths, thus higher and higher carrier frequencies are used. Excellent fade margins are possible with reasonable dish sizes, however the new $\mu/\mathrm{mm}$ links are rather interference than noise limited. For proper network design, a good understanding of radio interference is required. This paper shows the basic interference scenarios, the calculation and the effect of interference, the measurements and the finally the relevant planning recommendations are discussed.