Locating Technologies
Wi-Fi for real-time location: how it works, range and accuracy
Wi-Fi's main appeal for indoor location is that the infrastructure is often already there. Most buildings already have Wi-Fi access points installed for network connectivity, and those access points can sometimes double as fixed reference points for a location system, without deploying dedicated hardware purely for tracking.
Key specifications
Property | Typical value |
|---|---|
Frequency | 2.4 GHz and 5 GHz ISM/UNII bands (with 6 GHz increasingly available under Wi-Fi 6E) |
Range | Roughly 30–50 m indoors per access point, though this varies with obstructions and power |
Accuracy | Typically 3–5 m using RSSI; better achievable with Fine Timing Measurement (FTM) on supported hardware |
Measurement methods | RSSI, fingerprinting, Fine Timing Measurement (FTM / IEEE 802.11mc) |
Update rate | Generally lower than dedicated RTLS technologies; often several seconds between updates |
Tag power profile | Client devices (phones, Wi-Fi tags) typically draw more power than BLE tags, giving shorter battery life |
Accuracy and range depend heavily on access point density and placement, since most deployments use existing network infrastructure rather than one purpose-built for location.
How it works
Wi-Fi location systems generally use one of two approaches. The first, and most common, uses received signal strength (RSSI): a client device, or a dedicated Wi-Fi tag, is heard by multiple access points, and the relative signal strength at each is used to estimate distance and, through trilateration, position. As described in our measurement basics guide, RSSI is an indirect measurement, influenced by walls, reflections and interference as much as by actual distance, so this method typically produces accuracy in the metre range rather than centimetre precision.
Fingerprinting is a common refinement. During a site survey, the expected RSSI pattern from surrounding access points is recorded at many known reference points across the space. A device's live signal readings are then matched against this map to estimate location, which can improve accuracy in stable environments but requires the survey to be redone if the physical layout changes significantly.
A newer approach, Fine Timing Measurement (FTM, standardised as IEEE 802.11mc), brings time-of-flight ranging to Wi-Fi, similar in principle to the ToF techniques described in our radio frequencies guide. FTM measures the round-trip time of a signal exchange between a client and an access point to calculate distance more directly than RSSI allows, though it requires FTM-capable hardware on both ends and is not yet universally supported.
Measurement methods available
- RSSI – the most widely deployed method, using signal strength from multiple access points
- Fingerprinting – matching live RSSI readings against a pre-surveyed signal map
- Fine Timing Measurement (FTM) – time-of-flight-based ranging on supported 802.11mc hardware
Advantages
- Can reuse existing Wi-Fi network infrastructure, potentially lowering deployment cost
- Client devices (smartphones, laptops) are already Wi-Fi-enabled, useful for BYOD or visitor-facing applications
- Mature, well-understood technology with broad vendor support
- Reasonable range per access point reduces the number of fixed points needed to cover a large area
Limitations
- RSSI-based accuracy is generally coarser than BLE AoA or UWB, typically several metres
- Existing access point placement is usually optimised for network coverage, not location accuracy, which can limit performance if infrastructure isn't purpose-adjusted
- FTM support is still inconsistent across client devices and access points
- Wi-Fi client radios generally consume more power than dedicated low-power tags, shortening battery life for tracked devices
Typical applications
Wi-Fi-based location is commonly used for building- or zone-level occupancy and space utilisation analysis, general indoor wayfinding for visitors using their own smartphones, and coarse asset tracking where room-level accuracy is acceptable and reusing existing infrastructure is a priority.
Frequently asked questions
Can I use my existing Wi-Fi network for RTLS? In some cases, yes, particularly for coarse, zone-level tracking. Achieving better accuracy usually requires additional access points, FTM-capable hardware, or a dedicated site survey for fingerprinting.
How accurate is Wi-Fi-based location? Typically 3–5 metres using RSSI. Fine Timing Measurement can improve on this where supported hardware is available on both the client and access point.
Does Wi-Fi location drain smartphone battery faster? Continuous or frequent Wi-Fi scanning does use more power than a low-power protocol like BLE, so applications relying on smartphones for location should account for this in their design.