Also known as: DMR Tier III, DMR Tier 3
DMR Tier III is the trunked tier of the DMR standard. It adds a control channel and trunking signalling so many talkgroups can share a pool of two-slot TDMA channels, assigned on demand.1
Overview
Where Tier II is conventional, Tier III is a full trunked-radio system. Radios register (affiliate) and request calls over the control channel, which issues channel grants pointing them to a traffic channel and slot. (Motorola’s proprietary Capacity Plus offers similar trunking outside the strict Tier III standard.)
Technical characteristics
| Property | Value |
|---|---|
| Access | Two-slot TDMA + dedicated control channel |
| Signalling | CSBK control messages |
| Channel | 12.5 kHz |
| Vocoder | AMBE+2 |
History
Tier III trunking was standardised by ETSI to give DMR a multi-site, high-capacity option competing with P25 and TETRA in the commercial market.1
Deployment
Used by larger commercial, utility, and transport operators needing trunked capacity at lower cost than TETRA or P25.
Decoding it with GopherTrunk
GopherTrunk locks the Tier III control channel, follows CSBK channel grants to the assigned channel/slot, and decodes the voice. See Status.
Sources
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Digital mobile radio — Wikipedia, for the ETSI DMR tiers, including the trunked Tier III with its control channel and CSBK signalling. ↩ ↩2