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4.2 Recommendation 2
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- 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).
The majority of reviewers agree with this recommendation. In regard to this recommendation, one reviewer indicated that trunked systems usually employ one channel for control, affecting spectrum efficiency. In this regard, it suggested considering the implications of the advent of APCO phase 2 channel sizes.
Currently, APCO systems allow either 25 kHz or 12.5 kHz configurations. In order to ensure the orderly and efficient allocation of 12.5 kHz APCO channels, an overlayed12.5 kHz raster has been identified as appropriate. Future APCO phase 2 platforms may involve TDMA (12.5 kHz channels) or FDMA (6.25 kHz) techniques to allow an increased number of voice channels. However, these techniques are still under development and standards are not available. The Ministry will review the impact of such developments once standards have been finalised.
