Overview of infrastructure required to provide location data

This section will discuss the infrastructure technologies that are used by vendors to deliver end-to-end RTLS solutions in healthcare and support an understanding of the technologies and which infrastructure can support which RTLS capabilities.

Location data can be accessed in a number of ways from using more pervasive radio-based networks, to placing discreet location beacons and/or readers at main points of interest. 

Wi-Fi data networks are often deployed in a pervasive manner, that is to provide as much ‘coverage’ as possible to ensure availability across large hospital sites or campuses. When designing a Wi-Fi network there is a consideration in the RF planning and design between 3 main factors, being:

Coverage

Where does this Wi-Fi network need to be available?

Capacity

What are the connectivity and throughput requirements where this Wi-Fi network is used? Note: capacity does not have to be consistent across the Wi-Fi deployment and requirements may vary across locations.

Cost 

The available budget for the network and any potential return on investment will always be a consideration.

Wi-Fi networks tend to be provided by access points populating the coverage area with either a centralised controller appliance (virtual or physical with clustering options) and/or a cloud-based management or controller solution. RTLS Wi-Fi based applications usually require an increase in density of access points over and above data coverage. This is required to support the signal strength and access point positioning requirements of location tracking via Wi-Fi.

For adequate coverage to support data and voice transmission, the minimum RSSI (received signal strength indicator) the radio signal power to a device from an access point, should be -65dBm. Ideally, Wi-Fi based RTLS should use least 3 access point positions to allow for a client to be positioned using triangulation on RSSI measurement at this signal strength.

For more on Wi-Fi coverage and target metrics see Wi-Fi metrics and measures.

The IEEE standard 802.11mc branded as Fine Time Measurement (FTM) and OpenLocate, seeks to use time metrics rather than signal strength triangulation to position a client device. Both the access points and the device will measure the time taken for data conversations between them. With accurately placed access points these time measurements can produce 1-2m accuracy. This solution requires both the Wi-Fi system and the client to support the standard for a full implementation.

Improvements to tracking accuracy are possible without client contribution by using a combination of GPS and FTM measurements between access points to accurately position them on maps. Using this approach means that access point density requirements can be reduced compared to standard Wi-Fi implementations. FTM-capable solutions can use other hybrid technologies for improved positioning accuracy.

Bluetooth is a wireless technology that is well known in the consumer and corporate spaces. Typical uses are for headsets, sound bars and in-car entertainment. It uses the 2.4GHz spectrum but is interference resistant due to use of frequency hopping. which may be beneficial in hospital environments with multiple sources of interference from medical devices and other users. (How Bluetooth Technology Uses Adaptive Frequency Hopping to Overcome Packet Interference | Bluetooth® Technology Website).

With version 5 of Bluetooth Low Energy (BLE5), the technology has a range of up to 30m. Its low energy profile is also due to the lightweight protocol (less chatty) and lends itself to lower battery power usage for devices. Most such devices should last up to 3-5 years.

Most post-2015 Wi-Fi access points from the main Wi-Fi manufacturers include inbuilt BLE radios, allowing them to operate those radios for RTLS applications. Activating those radios tends to be software controlled and can require activating a license. This means that any Wi-Fi access points that have been refreshed since 2015 should be able to support BLE capabilities alongside Wi-Fi without any need for new hardware.

Due to the shorter range and battery possibilities for Bluetooth devices the technology lends itself well to RTLS applications. Within Wi-Fi, the density of access points aids the accuracy of both asset tracking and Wayfinding applications (3 access points for triangulation). Almost all implemented Wi-Fi networks are deployed without this density in mind. To subsequently provide this density can come at large additional cost.

BLE battery powered beacons can be deployed in addition to access points to provide the density necessary for good RTLS accuracy. This generally only applies to Wayfinding or Geofencing solutions as asset tracking solutions require enabled access point or specialised BLE gateways to sense the asset tag by triangulation. 

There are new enhancements to BLE capabilities for RTLS being developed currently, that offer potential future cost and accuracy benefits. One development is the equipping of access points with many directional Bluetooth antenna radios so that location can be determined by arc direction around the access point, rather than just proximity signal power from several points. This can make a BLE implementation possible using solely standard density access point deployments, which offers  a potential cost advantage.

At the time of writing, Juniper Networks is the only manufacturer to offer this capability commercially, under the name Virtual BLE (vBLE), a new implementation of BLE, which provides beacon-like coverage directly from the access point.

Everyone is familiar with the mapping functions within mobile phones which can position the user on a live map. This is usually done by a combination of Global Positioning System (GPS) and cell tower triangulation. For external, outside of building positioning, this is ideal and the accuracy of this has improved over the years.

The technology is unlikely to be used for asset tracking because of both a lack of coverage for battery powered tags and the fact that assets tend to be located indoors. For internal positioning, the mobile maps are unable to accurately map buildings with multiple floors meaning that the use of cell tower positioning is restricted to external spaces.

The challenge for RTLS vendors is to integrate the external positioning data from 4G or 5G mobile networks with their internal solutions, using Wi-Fi or BLE. NHS organisations should look to evaluate that integration from potential vendors, particularly with regard to deployment in campus environments which include significant outdoor areas.  

Expanding on the mobile networks above, which apply to GPS capable devices such as mobile phones, increasingly GPS itself is being integrated with RTLS systems to provide greater accuracy for wayfinding and mapping. GPS radios can be included within access points allowing that access point to be positioned accurately on the Earth’s surface.

If the access point is located by this method, then devices can be placed on wayfinding maps more accurately in the real world. Without this an error is introduced where the access points are placed by 'eye' on maps during installation, which if incorrect can reduce the accuracy of location data.

GPS positioning of access points is still rather new to the industry and organisations should look to see if their vendor of choice offers support for it. GPS is important for BLE and Wi-Fi FTM that are currently used for wayfinding.

Radio Frequency Identification (RFID) is a well-established technology that does not tie into Wi-Fi solutions and is often deployed in isolation. This technology is used exclusively for asset management through tags. There are two main RFID solutions: passive and active.

Passive RFID is commonly used for such consumer systems as contactless bank cards and door security systems. For RTLS, unpowered tags, usually presented as stickers, are placed on the assets. Auditor users then use handheld recording devices to register the presence of the tag and asset. This requires manual effort to keep the presence and location information up to date and as such does not track asset location in real time.

The tags themselves have no power, so do not require batteries, and they operate by RF induction from a reader device, which is powered.  There are various RF frequencies used, including 125-134KHz, 13.56MHz & 865-960 MHz.

The passive nature of the solution in comparison with the other RTLS solutions means that this technology is not suitable for direct integration with mobile asset tracking solutions. However, passive RFID can supplement a mobile system by providing information on fixed assets whose presence needs to be manually taken stock of.

In comparison to other technologies a passive RFID solution can be implemented cheaply and without disruption to any existing Wi-Fi solution.

Representing a halfway house between passive RFID and RTLS, active RFID is generally held as a more flexible version of passive that provides the same solution. The active asset tags contain batteries and can respond to readers from a greater distance than passive tags (as the reader does not need to power the tag). This reduces the admin overhead and manual scanning required to keep the asset information up to date.

The greater range and the active nature of the tags means that active RFID can be implemented as part of a mobile asset tracking solution.  It is possible to have active RFID readers placed in fixed locations and linked to the wider IT network to supplement a Wi-Fi or BLE based RTLS solution.

The technology uses two discrete RF frequencies- 433MHz & 2.45GHz​.