Page 276 - GuideFWA

Part 3.

COEXISTENCE BETWEEN FWA AND ISOCHRONOUS UPCS EQUIPMENT
ON THE BAND 1910-1930 MHZ

1. INTERFERENCE ANALYSIS BETWEEN UPCS AND FWA

1.1. THE FCC UPCS ETIQUETTE RULES CONSIST OF TWO INCOMPATIBLE SETS OF RULES

The FCC UPCS Etiquette contains two etiquette rules, one for asynchronous devices (1910 - 1920 MHz)
and one for isochronous devices (1920 - 1930 MHz). These rules are so incompatible that if for instance
an asynchronous (data) device and an isochronous device (speech) are used on the same desk in an office,
the speech service will be severely interfered all the time. This is a fact widely recognised, and is further
amplified by the unfortunate (isochronous) packing rules. EIA/TIA 41.6 is studying this matter, to see
which improvements to propose.

Besides, the Asynchronous rules are really not needed to support data, since modern standards do not
need separate rules to support both speech and data. DECT and PWT support both speech and packet data
up to 552 kbps. Furthermore, there seems to be no asynchronous devices developed for the 1910 - 1920
MHz band. Instead asynchronous devices have been developed for the 2.4 and 5 GHz bands where more
free bandwidth is available. Therefore, we do not foresee Asynchronous devices in the 1910 - 1930 MHz
to occur in Latin America, nor legally or illegally.

1.2. COEXISTENCE BETWEEN FWA AND UPCS ISOCHRONOUS DEVICES

Analysing the interference between FWA with Dynamic Channel Selection , DCS; and isochronous
UPCS is much simpler than between FWA and PCS or PCS and PCS.

The reasons are

a) that both FWA with DCS and the isochroconous UPCS systems are designed to provide reliable
services in an environment with several systems charring the same spectrum, and
b) that DECT, PHS(traffic channels) and isochronous UPCS Etiquette devices use the same basic channel
access mechanisms. These channel access mechanisms are designed to permit sharing of spectrum in a
frequency and time domain.
• listen for 10 ms before talking
• frame duration is a sub-multiple of 10 ms
• access channels are defined as a frequency & time slot combination
Therefore DECT, PHS(traffic channels) and isochronous UPCS Etiquette approved devices can coexist
on the band 1920-1930 MHz. The figure below illustrates this.

This means that Private Cordless equipment meeting the FCC Part 15 Isochronous rules, the DECT
standard or the PHS standard can coexist (except for the PHS control channel) in the band 1920 - 1939
MHz, and they can also coexist with FWA systems, if the FWA systems comply to the DECT, PWT(E) or
PHS standards (except for the PHS control channel). A frequency hopping FWA system (as the Multigain

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