Wi-Fi Indoor Positioning Systems: Vorteile, Herausforderungen, Alternativen

Wi-Fi Remains Go-to Technology Für Real-time Location Systems (RTLS) Due To Ubiquity Und Low Upfront Cost. However, Achieving Precision Required In Mission-critical Environments – Hospitals, Warehouses, Manufacturing Plants – Can Be Difficult. Below We Compare Main Wi-Fi Positioning Methods, Discuss Strengths And Limitations, Highlight Viable Alternatives.

See Our Whitepaper For Deeper Dive Into Indoor Positioning Options.

Wi-Fi Fingerprinting

Fingerprinting Builds Reference Map Of Wi-Fi Access Points (APs) And Their Signal Strengths (RSSI) Throughout Building. Asset Tag Scans Environment, Sends List Of Detected APs And RSSI Values Back To Server, System Interpolates Tag's Position Using Pre-recorded Map.

Pros:
• Uses Existing Wi-Fi Infrastructure, So No Extra Hardware Needed For Tags.
• Easy To Deploy Initially With One-time Survey.

Cons:
• Accuracy Drops To 4–10 m Unless Dense AP Deployment And Meticulous Survey Performed.
• Survey Becomes Invalid When APs Moved, Added, Removed – Requiring Continuous Maintenance.

Large Public Wi-Fi Databases – Like wigle.net – Can Accelerate Survey Creation, But Often Lack Precision Needed For RTLS.

RSSI-basierte Multilateration

This Technique Enhances Fingerprinting By Incorporating Raw Signal Strength From All Visible APs And Their Known Coordinates To Compute Tag's Location Via Multilateration.

Typical Accuracy: ~4 m Under Optimal Conditions With Sufficient APs. In Corridors Or Areas With Sparse Coverage, Method Can Produce Floor-level Errors.

Time-of-Flight (ToF) Triangulation

ToF Requires APs That Can Timestamp Packets With Sub-microsecond Precision. By Measuring Round-trip Time Between APs And Tag, System Triangulates Position.

Pros:
• Offers Best Accuracy Among Wi-Fi Methods – Often 0,5–1,5 m In Well-designed Deployments.

Cons:
• Needs Specialized, Tightly-synchronized APs, Significantly Increasing Infrastructure Cost.
• Multipath Reflections From Walls – Especially In Large Hospitals – Can Still Degrade Accuracy.

Angle-of-Arrival (AoA) & Hybrid Approaches

AoA Leverages Multiple-input Multiple-output (MIMO) Antenna Array To Determine Angle From Which Signal Arrives. Combined With ToF, AoA Can Further Refine Position Estimates.

Key Considerations:
• Requires Precise AP Orientation And High-quality Antenna Arrays.
• Less Dependent On Clock Sync Than Pure ToF, But Still Vulnerable To Multipath Noise.

Tag Hardware Und Cost

Because Wi-Fi Tags Must Embed Wi-Fi Transceiver, They Tend To Be Bulkier And More Expensive Than Bluetooth, Infrared, Or Ultrasound Tags. In Contrast, Our AirFinder RTLS Solution Uses Hybrid Bluetooth-Ultrasound Approach, Eliminating Need For Wi-Fi Chip While Delivering Comparable Accuracy At Lower Cost.

When Wi-Fi May Not Be Best Choice

Customers – Especially In Healthcare, Aviation, High-precision Logistics – Often Find Wi-Fi Insufficient For Their Strict Accuracy Requirements. Alternatives To Consider Include:

• Ultra-Wideband (UWB) – Sub-meter Accuracy, Low Latency, Robust To Multipath.
• Bluetooth Low Energy (BLE) – Cost-effective, Widespread Adoption, Moderate Accuracy.
• Ultrasound – High Accuracy Indoors, But Limited Range.
• Infrared (IR) – Line-of-sight Only, Best For Controlled Environments.

We're Ready To Help You Choose Right RTLS Technology For Your Environment.

Learn More About Wi-Fi And Other Indoor Asset Location Technologies In This Whitepaper