Conventional or Trunked P25?
Deciding on P25 is not the end of the technology selection process: important choices need to be made. Conventional or trunked? Phase 1 or Phase 2?
Luckily, in most cases these decisions are not difficult. While you should use an experienced consultant to guide your decision, some simple rules of thumb can help you in this area.
Conventional or trunked?
First, we can dispense with the misconception that there is a large functional gap between P25 conventional and trunked systems. This is not the case. The table clearly sets out the main functional differences.
| Conventional | Trunked |
|---|---|
| Radio channels selected by the user | Radio channels assigned to the user automatically |
| Channel access instantaneous | Channel access time varies with technology and other factors (typically measured in hundreds of milliseconds) |
| No control channel needed | Control channel used in all P25 trunked applications. |
| Suitable for smaller groups of users | Better for larger (~300+) organizations |
| Switching not needed | Core switching essential for operation |
| Digital control signaling inherent | Digital control signaling inherent |
Conventional vs. trunked feature comparison
Based on this information, as long as you have sufficient channels for the number of users and the number of user groups, you will save money and effort by staying with P25 conventional architecture.
| Feature | P25 Conventional | P25 Trunked |
|---|---|---|
| IP backbone | Available | Available |
| Analog and digital operation (repeaters/subscribers) | Yes/yes | No/yes |
| Simplex/half-duplex/duplex (repeaters) | Yes/yes/yes | Half duplex/duplex |
| Access Control/subscriber registration | Yes | Yes |
| Supports analog and digital consoles | Yes | Yes |
| Dispatch console support | Analog and digital | Analog and digital |
| End-to-end encryption | Yes | Yes |
| Distributed, centralized or switched voting | Yes | Yes |
| Simulcast | Yes | Yes |
| Multisite(automatic roaming) | Yes | Yes |
| Self-calibration (simulcast) | Yes | Yes |
| Rx voting | Yes | Yes |
| Multi-site switching | Distributed/centralized | Centralized/distributed |
| Advanced remote monitoring and diagnostics | Yes | Yes |
| Analog line interface | Yes | Yes |
| MDC1200 interface support | Yes | Yes |
| Multiple linking options including RF | Yes | Yes (stricter requirements) |
| OTAR | Yes | Yes |
| Packet data support | Yes | Yes |
| Voice call types | Group, individual, announcement, broadcast, emergency | |
| Non-voice call types | All standardized P25 supplementary services – status, radio check, monitor, call alert, inhibit/uninhibit, short message | |
| Talk Group ID | Yes | Yes |
| Individual ID | Yes | Yes |
| Emergency ID | Yes | Yes |
| Emergency Alarm | Yes | Yes |
| Call addressing | Yes | Yes |
| Cancel P25 Unit Call (dispatcher interrupt) | Yes | Yes |
| Automatic working channel assignment (trunking) | No | Yes |
| Talk group scanning | Yes | Yes |
| Interfaces | ISSI, PSTN, DFS | ISSI, PSTN, CSSI |
| Late entry | Yes (limited) | Yes |
| Call queuing | No | Yes |
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