Page 229 - GuideFWA

“In developing countries may be up to 30% of the metropolitan traffic (mainly
speech) will need to be served by RLL. This corresponds to 300 E/km2.”
For rural areas, the report projects FWA traffic densities of 0.35-3.5 E/km2.

Fig. 5.8 shows the median interference (as an increase in the noise floor) on the least-interfered
channel vs. FWA traffic load. The FWA sites were assumed to be “macrobases” as discussed
above, with an elevation of 40 meters. The UPCS victim receiver was assumed to be elevated 10
meters, and the attenuation through the building exterior was assumed to be 15 dB. The
propagation model adopted by the PCC.III Interference Experts Group was used.

50

45

Increase in noise floor 40
on least-interfered 35
channel (dB)

30

25

20 10 20 30 50 100 200 300
5

FWA traffic (Erlangs/km2)

Figure 5.8: FWA-to-UPCS interference (vs. FWA traffic density).

5.1.2.3.5 Effect of the Interference on UPCS

In light of the 1-dB noise floor increase criterion adopted by the Experts Group to calculate
separation distances between FWA and Licensed PCS, the increases shown in Fig. 5.8 are
enormous for FWA traffic densities expected in urban areas. However, one participant in the
Experts Group noted that UPCS systems could withstand such interference levels by simply
making the cells sufficiently small.

To test this claim, the effect of FWA interference on a Personal Wireless Telecommunications
(PWT) system was investigated. For indoor propagation between the PWT base and handset, the
“Ericsson” indoor propagation model was used (see ETR 310 [23], p. 43). The results are shown
in Fig. 5.9; calculation details are in the Annex.

As can be seen, the impact on PWT cell coverage area for FWA traffic densities of 10 E/km2 is
significant, and for more than 20 E/km2 the reduction in cell coverage is quite severe. Clearly, it
seems impractical to operate a UPCS system in the presence of interference from FWA systems
carrying the load levels expected in urban areas.

However, in rural areas, there would be little or no effect on the UPCS cell coverage area (with
no interference the coverage area is roughly 24,000 square feet). This suggests that one

Inter-American Telecommunication Commission 215