Page 206 - GuideFWA

These transients can occur whenever emissions start or stop e.g., at the beginning and end of
EVERY burst of timeslots. For synchronized, compatible TDMA systems, timeslot guard bands
can minimize the impact, but for any other victim technology, the impact may be more severe
than the impact predicted in the previous spreadsheet due to modulation. Proposed Solution:
Any future calculation should include some allowance for ALL regular emissions.

2.2. AENS VIEW

This issue was largely discussed within the experts group meetings, and the agreed conclusion
was to use only the emission mask due to modulation as the main interference mechanism.

The reason for that is not only the simplicity, but because it is the worst case of all the possible
interfering mechanisms:

• Spurious emissions: though isolation values that could be obtained by using the spurious
emissions specifications may be, in some cases, higher that those due to emissions due to
modulation, the spurious signals will appear at a few specific frequencies, and therefore those
problems could be solved by Dynamic Channel Selection in FWA TDD systems and by
intracell/intercell handovers in PCS systems. In addition, spurious emissions are not wide
band noise floor signals and the probability of occurrence is negligible compared to emissions
due to modulation. Moreover, it should be considered that FCC rules define for PCS a limit
for spurious emissions which is, at least, 13 dB and 17 dB higher than maximum allowed
spurious levels defined for PHS and DECT, respectively. This fact confirms that considering
spurious emissions, the results obtained by FWA TDD-PCS scenarios will be much better,
compared to PCS-PCS scenarios, than the obtained ones in [1] by using only emissions due to
modulation.

• Switching transients: In practice, transients are not very high, and they are very short. Their
average energy is extremely low and any error correction technique (as those presented in PCS
systems) are able to withstand occasional single bit errors.

• Intermodulation products: for the analysed cases, the most likely interference resulting from
unwanted intermodulation effects in victim receivers is the third order product which will
occur only in a partial spectrum of the PCS band. Since the probability of IM interference is
low, and the interference values are not so high, these problems could be also easily solved by
intracell/intercell handovers in PCS systems and by DCS mechanisms in FWA TDD systems.

As stated and agreed in report [1], section II.A.1. “Methodology”, the point of view of DECT and
PHS proponents is to use (as made in [1]) only the Emissions Due to Modulation as the main
interference mechanisms. The rests of interference mechanisms are not relevant as explained in
above.

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