Page 258 - GuideFWA

It is obvious that Monte Carlo simulation technique is one the possibilities to analyse the
interference between two systems, however, depending on how to implement it, it could be more
or less efficient and accurate than any other. In our opinion, the “worst case analysis” which is
included in report [1] is more accurate than the proposed one in [20], specially if taken into
account the considerably number of errors contained in [20]. The accuracy of [1] is much higher
because it allows a coherent comparative analysis that can not be done by the data contained in
[20]. It should be note that in both methodologies ([1] and [20]) the absolute values of the
interference levels are approximations to the reality, thus the accuracy can appear only if a
comparative analysis between different scenarios (some of then well-known and experienced, i.e.
PCS-to-PCD interference) can be carried out.

From this point of view, it is not necessary to implement a new methodology as proposed in [20],
and no further work by the Experts Group is needed.

Errors in report PCC.III/964/98 [20]

NOTE: It is not intention of the DECT/PHS proponents that the description of the following
errors serve to validate the methodology described in [20] by correcting them. Even when
following errors were corrected, in our opinion the use of this methodology is not required. The
following errors list tries only to show what different results can be obtained applying the same
(or similar) methodology to a different set of assumptions, and to demonstrate that only a
comparative analysis can provide a reliable conclusion.

The following errors and incorrect assumptions have been found in [20]:

• The analysis tries to quantify the interference from DECT FWA system towards PCS base
stations, and to do that, it assumes that PCS system is located in A-band. This is an great
error, since the PCS base stations in A-band does not suffer any interference from any TDD
system located in 1910-1930 MHz band. THE RECEPTION BAND FOR A PCS BASE
STATION ALLOCATED IN THE A-BAND IS 1850-1865 MHz WHICH IS FARTHER
ENOUGH TO AVOID INTERFERENCE FROM 1910-1930 MHz. (In document it is said
the PCS RX band is 1930-1945 MHz, which is only valid for PCS terminals allocated in A-
band). It could be a simple typographic mistake, but in that case:
1. If the intention is to analyse the interference on the PCS mobiles, instead of on the PCS
base stations, then the value of the RX antenna gain for PCS can not be 15 dB as stated in
document but 0 dB, and the RX antenna height can not be 25 m, as stated in document
but 1.5m, which reduces drastically the Fresnel breakpoint (from about 6300m. down to
380m), and it means that propagation losses will be much higher since the “slope” with
factor 4 in the propagation model is achieve much before.
2. If the intention is to analyse the interference on the PCS base station, but in C-band,
instead of in A-band, that is, in the PCS RX band 1985-1910 MHz, then the adjacent
DECT channel should be 1912.896 MHz, instead of 1928.488. It means a frequency
separation which is 1.384 MHz larger than the considered in [20], and it could provide
around 15 dB additional attenuation for interfering signal due to the DECT mask, than the
used in calculations in [20].

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