TABLE 5 The effective height of the road, hs (heavy traffic) Frequency (GHz) h1 (m) hs (m) h2 = 2.7 h2 = 1.6 3.35 4 1.3 (2) 8 1.6 (2) 8.45 4 1.6 (2) 8 1.6 (2) 15.75 4 1.4 (2) 8 (1) (2) (1) The breakpoint is beyond 1 km. (2) No breakpoint exists. TABLE 6 The effective height of the road, hs (light traffic) Frequency (GHz) h1 (m) hs (m) h2 = 2.7 h2 = 1.6 3.35 4 0.59 0.23 8 (1) (1) 8.45 4 (2) 0.43 8 (2) (1) 15.75 4 (2) 0.74 8 (2) (1) (1) No measurements taken. (2) The breakpoint is beyond 1 km. When h1, h2 > hs, the approximate values of the and lower bounds of basic transmission loss for the SHF frequency band can be calculated using equations (2) and (4), with Lbp given by: (8) On the other hand, when h1 hs or h2 hs no breakpoint exists. When two terminals are close (d < Rs), the basic propagation loss is similar to that of the UHF range. When two terminals are far, the propagation characteristic is such that the attenuation coefficient is cubed. Therefore, the approximate lower bound for d Rs is given by: (9) The approximate upper bound for d Rs is given by:
(10) The basic propagation loss Ls is defined as: (11) Rs in equations (9) to (11) has been experimentally determined to be 20 m. on measurements, a median value is given by: (12) Millimetre-wave propagation At frequencies above about 10 GHz, the breakpoint distance Rbp in equation (3) is far beyond the expected maximum cell radius (500 m). This means that no fourth-power law is expected in this frequency band. Hence the power distance decayrate will nearly follow the free-space law with a path-loss exponent of about 1.9-2.2. With directional antennas, the path loss when the boresights of the antennas are aligned is by dB (13) where n is the path loss exponent, d is the distance between Station 1 and Station 2 and L0 is the path loss at the reference distance d0. For a reference distance d0 at 1 m, and assuming free-space propagation L0=20 log10 f −28 where f is in MHz. Lgas and Lrain, are attenuation by atmospheric gases and by rain which can be calculated from Recommendation ITU-R P.676 and Recommendation ITUR P.530, respectively. Values of path loss exponent n are listed in Table 7. 7 Directional path loss coefficients for millimetre-wave propagation Frequency (GHz) Type of environment Half power beam width (degree) Path loss exponent Tx Ant Rx Ant n 28 very high-rise 30 10 2.21 Urban low-rise 30 10 2.06 60 Urban low 15.4 15.4 1.9 4.1.3 Site-specific for NLoS situations This situation is depicted as the paths between D and E in Fig. 1. 4.1.3.1 Frequency range from 800 to 2 000 MHz For NLoS2 situations where both antennas are below roof-top level, diffracted and reflected waves at the corners of the street crossings have to be considered (see Fig. 3). dB (14) where:
TABLE 21 Differential time delay window for the strongest four components with respect to the first arriving component and their relative amplitude Type of environment Time delay resolution Frequency (GHz) Antenna height (m) (m) Excess time delay (s) h1 h2 1st 2nd 3rd 4th 80% 95% 80% 95% 80% 95% 80% 95% Urban 200 ns 1.9-2.1 46 1.7 100-1 600 0.5 1.43 1.1 1.98 1.74 2.93 2.35 3.26 Relative power with respect to strongest component (dB) 0 0 −7.3 −9 −8.5 −9.6 −9.1 −9.8
5.4.2 Below-rooftops propagation environments 22 shows the results of the number of signal components for below-rooftops environments from measurements in different scenarios such as type of environments, frequency bands and antenna heights. TABLE 22 Maximum number of signal components for below-rooftops environments Type of environment Time resolution Frequency (GHz) Antenna height (m) Range (m) Maximum number of components h1 h2 3 dB 5 dB 10 dB Urban 20 ns 3.35 4 1.6 0-200 0-1 000 2 2 3 3 2 2 4 4 5 5 6 9 20 ns 8.45 4 1.6 0-200 0-1 000 1 1 3 2 2 2 3 4 4 4 6 8 20 ns 15.75 4 1.6 0-200 0-1 000 1 2 3 3 2 2 3 4 4 6 5 10 Residential 20 ns 3.35 4 2.7 0-480 2 2 2 2 2 3 5.5 Fading characteristics The fading depth, which is defined as the difference between the 50% value and the 1% value in the cumulative probability of received signal levels, is expressed as a function of the product (2fLmax MHz·m) of the received bandwidth 2f MHz and the maximum difference in propagation path lengths Lmax m as shown in Fig. 13. Lmax is the maximum difference in propagation path lengths between components whose level is larger than the threshold, which is 20 dB lower than the highest level of the indirect waves as shown in Fig. 14. In this Figure, a in decibels is the power ratio of the direct to the sum of indirect waves, and a = − dB represents a NLoS situation. When 2fLmax is less than 10 MHz·m, the received signal levels in LoS and NLoS situations follow Rayleigh and Nakagami-Rice distributions, corresponding to a narrow-band fading region. When it is larger than 10 MHz·m, it corresponds to a wideband fading region, where the fading depth becomes smaller and the received signal levels follow neither Rayleigh nor Nakagami-Rice distributions. FIGURE 13 Relationship between fading and 2fLmax FIGURE 14 Model for calculating Lmax