Beacon Payloads

This reference describes the BLE advertising payload formats supported by the NISC Muster Tracking system.

Supported Formats

iBeacon

Apple's proximity beacon standard. The advertising payload contains:

Field	Size	Description
UUID	16 bytes	Proximity UUID identifying the beacon group
Major	2 bytes	Major group identifier
Minor	2 bytes	Individual beacon identifier
TX Power	1 byte	Calibrated transmit power at 1 meter

Eddystone-UID

Google's open beacon format:

Field	Size	Description
Namespace	10 bytes	Organization identifier
Instance	6 bytes	Individual beacon identifier
TX Power	1 byte	Calibrated transmit power

Eddystone-TLM

Telemetry frame broadcast alongside UID frames:

Field	Description
Battery voltage	Millivolts
Temperature	Degrees Celsius
Advertising PDU count	Total packets sent
Uptime	Seconds since power-on

RSSI and Distance Estimation

The system uses Received Signal Strength Indicator (RSSI) values from gateways to estimate distance:

• RSSI is measured in dBm (negative values; closer to 0 = stronger signal)
• Path loss model converts RSSI to approximate distance using the beacon's TX Power calibration
• Trilateration combines distances from multiple gateways to estimate position

TIP

RSSI is affected by obstacles, reflections, and interference. Positioning accuracy improves with more gateways and clear line-of-sight.

Identity Resolution

The ingestion pipeline resolves beacon identity through several methods:

1. MAC address — Direct lookup against registered beacons
2. iBeacon UUID/Major/Minor — Matched to registered beacon profiles
3. IRK resolution — For beacons using BLE privacy (randomized MAC addresses), the system resolves identity using Identity Resolving Keys

Battery Reporting

Not all beacons report battery level. When available:

• Eddystone-TLM frames include battery voltage
• Some iBeacon firmware includes battery in manufacturer-specific data
• The system displays battery percentage in the Admin Beacons view where supported