## 5 Results and Calculation Examples  
Results of systematic hop-length calculations for short- and medium-haul digital \(\upmu\)/mmW point-to-point links are presented in this section. Solving Equation (18), the recommended maximum distances were calculated. All the links operate in ETSI-defined communication bands widely used in Europe, at frequencies of 13, 15, 18, 23, 26, 28, 32, 38, 58, and 80 GHz. Up to 38 GHz, the links in the calculations used 14 MHz channel spacing (ETSI and ITU channel raster) and 32-TCM (trellis coded modulation) for 34 Mbit/s [10; 24]. The 58 GHz links used 50 MHz channel spacing. The transmitters were set to the highest output power and the links had identical antenna size on both ends. The main parameters of the calculated links are summarized in Tables 3 and 4. In the 13-38 GHz bands, slip-mounted 60 cm- and 30 cm-diameter parabolic dishes are used (marked with \(\upomega\)). At  
Figure 13: **(a)** Ice and snow on the radome of a parabolic dish; the photo is re-printed with permission from RACOM [34]. **(b)** Extra attenuation due to a tree in the near field. **(c)** ODU installed behind a church window (polycarbonate lamels). **(d)** Metal cables inside the first Fresnel zone of the \(\upmu\)W link. 58 GHz, \(\omega\) 30 cm parabolic dishes and integrated 20 cm rectangular antennas are used (marked with \(\square\)). The integrated rectangular 58 GHz antenna is a grid composed of radiating waveguide elements. The low-profile antenna structure and its measurement are discussed in Reference [46]. The system and antenna gain values are illustrative examples. Naturally, the simulation can also run with different \(SG\) values and with asymmetric antenna configuration. The graphs in Figures 14 and 15 were drawn using the rain model according to ITU-R P.838 [38]. The shadowed regions show typical rainfall rates in Central and Eastern Europe, (H and K rain zones according to ITU-R P.837 [37]). The curves were calculated without any additional obstacle loss (Figure 13). Single-polarized links were calculated, and there was no polarization combiner loss calculated in the link budget. Antennas were directly connected to the transceivers, thus no waveguide losses were considered due to feeder lines. Vertical polarization is shown in Figures 14a and 15a. Horizontal polarization is shown in Figure 14b and in Figure 15b. As earlier discussed in Section 4, at 58 GHz frequency, the atmospheric attenuation is very high. Therefore, horizontal polarization is not recommended, and only vertical polarization is calculated [44; 45; 49]. Note that 7-15 GHz links are rarely used in a dense urban environment. For the 13-18 GHz links, the minimum recommended dish diameter is 60 cm. Several communication authorities specify very strict antenna pattern requirements for the lower frequency bands to avoid interference (e.g., minimum antenna gain, maximum sidelobe, front-to-back ratio) [50]. In practice, the 30 cm dishes are not permitted in the frequency bands below 18 GHz in some countries to achieve better frequency re-use. Therefore, the calculated 13-18 GHz links with 30 cm dishes are shown only for comparison (the upper three curves in Figure 15a,b). Finally, calculation results are shown for the E band. In the examples, the parameters of the Nokia millimeter-wave radio family are used, as given in Table 5. The \"Wavence\" radios can operate with several channel spacing options at 80 GHz: 62.5 MHz, 125 MHz, 250 MHz, 500 MHz, 750 MHz, 1 GHz, 1.25 GHz, 1.5 GHz, and 2 GHz. The 80 GHz radio uses adaptive modulation up to 256-QAM.