5. Summary of outcomes

1. To efficiently cater for the introduction of APCO P25 phase 1, a channelling plan with a 12.5 kHz raster is implemented in conjunction with the existing 25 kHz plan. 12.5 kHz channels will be named “TSN” for “narrow band”. (Figure 1)
2. To preserve the current block and channel assignment scheme (band plans, TS 800 MHz), digital channels are overlaid on the existing analogue channel raster. The maximum EIRP limit of the band (21.8 dBW) remains unchanged.
3. To promote RF efficiency, a digital trunked dispatch system permitted to operate in the TS-band, must have a minimum number of digital voice channels equivalent to the current minimum number of analogue voice channels. In other words, a single TETRA 25 kHz channel assignment, or three APCO P25 (phase 1) 12.5 kHz channel assignments are considered equivalent to an analogue trunked system (with three RF channel assignments).
   
   Later when it becomes available, two APCO P25 (phase 2) 12.5 kHz channel assignments will be considered as equivalent.

a.    Coverage area

The coverage area of a base station is the area of service within which the licensee has a reasonable expectation of protection from harmful interference. This is defined by a continuous contour equivalent to a signal level of -106 dBm or a theoretical coverage area with a radius of 58 km*, whichever is the smaller. See Figures 2 and 3.

Figure 2 - Without terrain limitation, a 58 km radius applies

 

Figure 3 - With terrain limitation, the smaller -106 dBm area applies

b.    Co-channel re-use distance

The re-use distance is the distance required to ensure a suitable grade of service between co-channel services. Generally, the re-use distance is constrained by topographic obstructions. See Figure 4.

In areas where the local topography may not provide sufficient levels of obstruction loss between co-channel services, the proposed service must protect existing services to a minimum C/I of 18 dB* at the edge of the existing coverage area. See Figure 5.

Co-channel, first and second adjacent channels, etc, in this document refer to the 25 kHz raster, not the 12.5 kHz sub-channels.

d.    Protected C/I

In some instances, the above guidelines may not be optimal when considering specific characteristics of the local topography, especially in large and flat terrains. In such cases, the above distances can be adapted, provided that the proposed service complies with the minimum C/I of 18 dB at the edge of the coverage area of the existing service.

Explanatory notes:

* The C/I level of 18 dB has been obtained considering dynamic conditions (fading) for analogue, APCO and TETRA systems. This figure takes into account the C/I requirements to maintain a Delivered Audio Quality (DAQ) grade of 3.4 (as specified in TSB88.1, table A-1). This value is also used in ITU-R SM.337-4 (table 1), where a calculation example is given for determining frequency and distance separation between land mobile services in the UHF band.

Detail of C/I specifications (extract from TSB88, table A-1):