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Hardware & Implementation IPS

Indoor Positioning System

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A system using BLE beacons, AoA/AoD direction finding, or Channel Sounding for indoor location tracking.

다른 명칭: IPS RTLS

Indoor Positioning System (IPS)

An Indoor Positioning System (IPS) uses BLE technology to determine the location of people or assets within buildings where GPS signals are unavailable. BLE-based IPS is deployed in warehouses, hospitals, airports, retail stores, and smart factories for asset tracking, wayfinding, and occupancy analytics.

BLE Positioning Technologies

BLE offers three positioning approaches with increasing accuracy:

1. RSSI-Based Positioning (1-5 meter accuracy)

The simplest approach measures Received Signal Strength from multiple BLE beacons and uses trilateration or fingerprinting to estimate position. RSSI is noisy (multipath, body absorption, antenna orientation), so accuracy is limited. However, it works with any BLE hardware and requires no special SoC features.

2. Direction Finding -- AoA/AoD (0.5-1 meter accuracy)

Bluetooth 5.1 introduced Angle of Arrival (AoA) and Angle of Departure (AoD) using antenna arrays. AoA locators contain multi-element antenna arrays that measure the phase difference of incoming signals to compute the angle from which a beacon signal arrives. Combining angles from multiple locators yields sub-meter positioning. AoD shifts the antenna array to the beacon, allowing the receiving device to compute its own position.

3. Channel Sounding (10-50 cm accuracy)

Bluetooth 6.0 Channel Sounding uses phase-based ranging and round-trip time measurements for centimeter-level distance estimation. Unlike RSSI or AoA, Channel Sounding measures actual distance rather than signal characteristics, providing the highest accuracy and robustness against multipath.

System Architecture

A BLE IPS typically consists of:

Beacons/Tags: Battery-powered BLE Peripherals carried by people or attached to assets, advertising at regular intervals
Locators/Anchors: Fixed BLE Central receivers (or AoA antenna arrays) installed at known positions throughout the facility
Location Engine: Server-side software that collects RSSI/angle/distance data from locators and computes position estimates using algorithms (trilateration, particle filters, Kalman filters)
Application layer: Maps, dashboards, geofencing rules, and analytics

Hardware Considerations

For RSSI-based systems, any BLE chip works. For Advertising">Direction Finding, chips must support CTE (Constant Tone Extension) -- the nRF52833 and nRF5340 support AoA/AoD. For Channel Sounding, Bluetooth 6.0 silicon is required (e.g., nRF54H20).

The antenna array for AoA locators typically uses 4x4 or larger patch arrays with lambda/2 spacing (about 62 mm at 2.4 GHz). These arrays are commercially available from companies like Quuppa, u-blox, and Nordic's reference design.

Related Terms

RSSI Channel Sounding Direction Finding

BLE Beacons Explained: iBeacon, Eddystone, and AltBeacon

Protocols & Profiles

BLE Direction Finding: AoA and AoD for Indoor Positioning