Wi-Fi based positioning systems are commonly used to overcome inadequacies of GPS indoors. They have the advantage of also providing a value add service (internet access) and, therefore, are a pre-existing infrastructure in many establishments. Many companies, like Cisco and IBM, have developed systems that allow for some navigation and indoor location analytics using WiFi.
WiFi hot-spots are effectively 'fixed' anchor points providing a static known position. A device detects a WiFi access point and, once multiple points are detected, can determine its position. WiFi implementations require access points, a data service that computes location (and keeps track of all the locations at any given point), and a location specific context (a blueprint overlay of the building).
On the positives, the WiFi 'receiver' infrastructure is relatively ubiquitous as it works well with mobile devices and doesn't require you to sign into the WiFi network or 'opt-in' to location services to work for tracking purposes. However, while tracking location may not require an app, like other systems, moving beyond tracking to communicate does require a communication interface and opt-in, like an app. (-1)
Additionally, the requirement of internet access, power points and software to identify the various WiFi networks makes the infrastructure, relatively speaking, difficult to set-up. While this may be feasible at major shopping malls and department stores, it may be cost prohibitive to extend to other venues. (-1)
Existing WiFi access points may be unreliable, inconvenient and poorly placed for the situation at hand. The fixed nature of WiFi access points and relatively high cost of installing them means there is limited flexibility in altering the network and it is difficult to achieve the level of precision afforded by beacons or RFID. (-1)
Additionally, WiFi systems' ability to identify individuals to allow for navigation and analytics is limited, particularly by Apple devices. In order for your phone to detect a WiFi network, it sends out a string of data that is unique to your phone. Retailers use WiFi 'sniffers' to listen for your phones unique signature and, thus can tell you're in the vicinity. Previously, these signatures were static and so WiFi could identify unique users. However, with the introduction of iOS 8, Apple began randomizing the MAC address (device ID). Now, businesses may be able to detect a device but they cannot necessarily tell if the device is unique. (-1)
It is worth noting that because Android allows for ranging for both WiFi and Bluetooth, and does not randomize the MAC address, it is much easier to achieve an equal experience.
Unlike GPS or BLE, data is actually being transferred over a WiFi network, meaning that hacking into the network poses more of a risk than its counterparts. Wi-Fi has adopted various encryption technologies to secure the network and the technology has come a long way over the years. Security is going to depend on the encryption techniques used and there are a lot of companies out there that specialize in providing secure wireless connections and data exchange. (-2)
We've already discussed cost relative to the number of WiFi access points and level of precision required. The fact is, if there is an existing WiFi network in place and location details are only needed at the room or zone level, WiFi can be a great, low cost solution. However, if location information is needed at a high-level of accuracy or movement needs to be recorded, the number of access points and data service required becomes more complex and thus more expensive. (-2)
Other costs associated with WiFi location systems include internet charges, maintenance and an app for users to download so that the positioning has the correct context and protocols.
The verdict for Wifi depends on the level of precision and existing infrastructure. WiFi has a much higher bandwidth so when internet access and data transfer is required, it is a critical solution component. However, for accurate indoor location analytics, user positioning or tracking, beacons and RFID are both better solutions.