Overview of GPS reporting methods supported in MOTOTRBO systems. Includes Regular GPS, Enhanced GPS, Enhanced GPS with CSBK, PTT triggered GPS, and Swift GPS reporting logic. Describes cadence limits, licensing requirements, throughput capabilities, and operational constraints.
GPS Data Format
• EPSG:900913 Mercator coordinates.
• RSSI is measured by repeater RX path.
• Radio sends GPS to the application through a Repeater. The repeater evaluates received signal quality.
Regular GPS
• Cadence options: 7.5, 15, 30, 60, 120 seconds.
• Revert channel is required to avoid collisions.
• Regular GPS uses a 1 second transmission.
Enhanced GPS
• Collisions are eliminated because subscribers transmit only in reserved windows.
• The repeater creates an eight minute superframe containing sixteen 30 second frames.
• Each frame contains windows. A window has an announcement slot and GPS bursts.
• Subscribers request a window. The repeater confirms reservation. Radios revert to the EGPS Revert Channel and transmit within their window.
Enhanced GPS Superframe Structure
+------------------ Enhanced GPS Superframe Structure -------------------+
| |
| Superframe = 8 minutes (480 seconds) |
| ├── Frame 1 (30 sec) |
| │ ├── Window 1 |
| │ │ ├── Announcement slot |
| │ │ └── GPS data bursts |
| │ ├── Window 2 |
| │ │ ├── Announcement slot |
| │ │ └── GPS data bursts |
| │ └── ... |
| ├── Frame 2 (30 sec) |
| ├── ... |
| └── Frame 16 (30 sec) |
| |
| Superframe repeats continuously |
| Each window size determines capacity and cadence |
+------------------------------------------------------------------------+
Enhanced GPS Capacity
| Configuration | Capacity at 90 percent load with 60 second cadence (both slots) |
|---|---|
| Standard Windows | Up to 360 location responses per minute |
| Window Size 1 | Up to 1808 responses per minute |
| Window Size 2 | Up to 896 responses per minute |
For fleets above 2200 radios with 2-minute cadence, distribute load across two scheduled repeaters.
Enhanced GPS with CSBK
When CSBK GPS is enabled the system supports twice the number of radios at a similar delivery success rate. Revert channel is required.
Requirements
• license in TRBOnet.
• Window size 1 requires .
• Window size 2 requires or . Control Radio does not work for CSBK in or .
Limitations
• No Basic Privacy or Enhanced Privacy.
• No confirmed data delivery.
• Indoor location is not supported.
• MOTOTRBO Link does not support CSBK.
• Allowed cadences are 7.5, 15, 30, 60, 120 seconds. Other values cause LRRP error .
PTT Triggered GPS
• Operates using CSBK commands.
• Requires subscriber firmware or higher.
• Requires enabling CSBK data in the subscriber codeplug and Repeater GPS coordinates in MNIS.
• Motorola states that inband location is sent in the first 2 to 3 bursts.
• Real world observation: PTT must be held for about 5 seconds to activate the GPS transmission.
• Recent subscriber firmware sends GPS data only through MNIS and NAI Voice and Data.
Mixed Window Operation
• Each slot of a Data Repeater can be configured with a different window size.
• A radio with a smaller window size fits into a larger reserved window size.
• Regular GPS is compatible with EGPS Data Repeaters but sends outside the reserved windows.
Swift GPS Reporting
• Swift report supports transmission of 40 to 50 coordinates per report.
• Maximum packet size is 400 bytes which holds about 60 coordinates without extra parameters.
• Typical packet size is 100 to 150 bytes.
• A large report is formed only with rare trigger conditions or during server requests for stored data.
Swift GPS Timing
• Swift request: about 1 second.
• Swift response: about 2 seconds plus preamble.
• Downloading 300 coordinates requires about 1 minute on a free channel.
• Revert Channel is required.