 cell pattern (three sectors, each of a hexagonal shape). In this GPRS example, the difference in coverage of the four coding schemes can clearly be seen, with the covered area decreasing progressively from CS-1 to CS-4. Figure 2.19 assumes the use of frequency hopping. Figure 2.20 illustrates the equivalent coverage areas for the nonhopping case. With the exception of CS-4, all coverage areas are reduced compared to the hopping case. The difference with CS-4 is the absence of error protection SO this coding scheme has increased vulnerability to fading (and hence increased block errors) when hopping. EGPRS and GPRS share the same concepts for relative coverage areas where EGPRS varies over the full range of modulation coding schemes 1 to 9. These results refer to a convenient cell size of 4000 m. Continuing with the GPRS example, coding scheme CS-1 does not quite cover the whole cell at this distance (with frequency hopping), and hence the overall coverage for CS-1 is a little less that 100 %. This fact explains the values presented in the next figure. Figure 2.21 illustrates the perceived cell radius of the different coding schemes, as a percentage of the 4000 m cell radius, both with and without frequency hopping. Coverage Planning Coverage areas of different GPRS coding schemes (sfg) 11000 10000 10000 11000 Figure 2.19 Coverage with frequency hopping Coverage areas of different GPRS coding schemes (sfg) 11000 10000 10000 Figure 2.20 Coverage without frequency hopping Radio Network Planning and Optimisation Figure 2.21 Perceived cell radius Figure 2.22 shows the relative coverage areas (within a cell) of the four schemes (relative to CS-1) in the two hopping scenarios. Both figures are based on simulations employing the path loss model used in UMTS 30.03 v3.2.0. Assuming 900 MHz with a base station antenna height of 15m above average rooftop level, the path L is given by the following formula: L = 120.9 + 37.6 log 10(R) dB (2.47) It has been shown that the service area for CS-1 and CS-2 will typically cover the