urns. There is much more fading advantage achieved from p = 1.0 to p = 0.7 than from p = 0.7 to p = 0.1. Based on p = 0.7 and n = 11, from Figure 18.6 we can calculate antenna separation values (for 850-MHz operation). For example, if h = 50 ft (16 m), we can calculate d using formula (18.4): = 50/11 = 4.5 ft (1.36 m). Recvr Recvr Combiner Output Figure 18.5 The space diversity concept. 18.4 IMPAIRMENTS: FADING IN THE MOBILE ENVIRONMENT Data below these lines with high probability h: Antenna height in wavelength a = 90° d: Antenna spacing in wavelength (Broadside) Empirical curves (At 850 Mhz) Base-station antennas Figure 18.6 Correlation coefficient P versus the parameter n for two receive antennas in different orientations. (From Ref. 7, Figure 6.4, reprinted with permission.) For an antenna 120-ft (36.9-m) high, we find that d = 120/11 = 10.9 ft (or 3.35 m) (from Ref. 7). 18.4.2.2.1 Space Diversity on a Mobile Platform. Lee (Ref. 7) discusses both ver- tically separated and horizontally separated antennas on a mobile unit. For the vertical case, 1.52 is recommended for the vertical separation case and 0.52 for the horizontal separation case. 4 At 850 MHz, 2 = 35.29 cm. Then 1.52 = 1.36 ft or 52.9 cm. For 0.51, the value is 0.45 ft or 17.64 cm. 18.4.3 Cellular Radio Path Calculations Consider the path from the fixed cell site to the mobile platform. There are several mobile receiver parameters that must be considered. The first to be derived are signal quality minima from EIA/TIA IS-19B (Ref. 8). The minimum SINAD (signal + interference + noise and distortion to interference + noise + distortion ratio) is 12 dB. This SINAD equates to a threshold of -116 dBm or 7 uV/m. This assumes a cellular transceiver with an antenna with a net gain of 1 dBd (dB over a dipole). The gross antenna gain is 2.5 dBd with a 1.5-dB transmission line loss. A 1-dBd gain is equivalent to a 3.16-dBi gain (i.e., 0 dBd = 2.15 dBi). Furthermore, this value equates to an isotropic receive level of -119.16 dBm (Ref. 8). One design goal for a