Using Bluetooth Beacons to Measure Gait Speed

There’s recent research into using Bluetooth beacons to measure human gait speed. The ability to walk can be used as a core indicator of health in aging and disease. For example, it can enable early detection of cognitive diseases such as dementia or Alzheimer’s disease.

Researchers at Universitat Jaume I and University of Extremadura, Spain, have created a new dataset. In their paper BLE-GSpeed: A New BLE-Based Dataset to Estimate User Gait Speed (pdf) they describe how they collected the data.

The database is freely available and includes:

  • mac: The MAC address of the detected beacon.
  • rssi: The RSSI value obtained for the beacon.
  • device: A four-character descriptor for the smartwatch that performed the scan.
  • timestamp: The time stamp at which the scan was received.
  • user: The id of the user that was performing the experiment.
  • direction: A number (0 or 1) indicating the direction of the walk.
  • walk_id: A number that identifies each walk.
  • speed: The actual speed of the user, in $m/s$.

It database contains RSSI measurements from different wearable devices and different BLE beacons, corresponding to 382 walks performed by 13 actors. The open source code used is available on GitHub.

Combining Wake Up Radio (WUR) and Bluetooth LE

There’s interesting new research from University of Oulu, Finland, on Wake-up radio enabled BLE wearables: empirical and analytical evaluation of energy efficiency.

Wake Up Radio (WUR) uses a very low power device that senses a radio signal to switch other devices, in this case a Bluetooth LE transmitter. A AS3930 WUR senses a signal in the range 110-150 kHz and switches a Texas Instruments Bluetooth CC2640R2 LaunchPad board.

The idea is that usually Bluetooth LE advertises every say 100ms to 1000ms and this is wasteful on battery power if the advertising is only needed for short periods of time. The paper assesses the feasibility of using WUR to turn advertising on and off to save battery power. While this is in in the context of wearables, the authors don’t mention much more regarding what might switch the beacons to advertise, other than:

The transmitter of this wake-up signal, which is usually a less restricted device, might be integrated with the communication infrastructure or deployed as an independent system element

The authors later mention healthcare so perhaps wearable beacons might only transmit when needed in particular areas.

It’s also mentioned that WUR can mitigate against the problem of interference when many Bluetooth devices advertise at the same time. This problem is rare and requires a very large number of devices. The authors later mention healthcare but this is unlikely to be a problem. A warehouse with thousands of assets might be a more realistic scenario. In this case, you could envisage wanting a Bluetooth beacon only transmitting when invited to do so.

The paper has some useful charts showing usual Bluetooth power use over time (without WUR):

You can see the periodic advertising which isn’t regular due to the 10ms long pseudo-random delay between advertisements. This is the part of the Bluetooth standard that helps ensure two device that collide usually don’t do so the next time they advertise. In between advertising, the power use a very low 0.3 µW.

The paper shows that energy consumption of the system as a function of the number of wake-ups in a period of time and the maximum application-level latency:

The paper concludes that the WUR approach can be more energy efficient when the desired latency for data delivery is below 2.11s. Even though the consumption of the WUR is low, it unfortunately exceeds the level of a BLE only system sleep mode by almost two orders of magnitude.

In our opinion the researchers are trying to improve on something that is already very low power. In between advertising, power use is extremely low. A CR2477 battery in a Bluetooth wearable can advertise periodically for up to 3 years. Also, for the wearable scenario, it’s more normal to use a low power accelerometer to only have the wearable transmit when moving. This way the battery lasts an extremely long time that’s limited more by the physical lifetime of the battery (5 to 10 years) rather than battery consumption.

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Dementia Anti-Wandering Using Beacons

The Hong Kong Multimedia Technology Research Center (MTREC) has an interesting project that implements a dementia anti-wandering system using iBeacons.

A paper (pdf) explains how it uses a novel multi-hop system to track targets using mobile sensors. The multi-hop approach extends the sensing area and reduces the deployment cost.

iBeacon Cooperative Tracking

The system uses a particle filter which analyses the temporal and spatial information of the targets to achieve 4.37m and 9.46m tracking error in a campus and a shopping mall respectively.

Read about Beacons in Life Sciences

Bluetooth in Healthcare

The Bluetooth blog has a recent post on 4 Reasons to Use Bluetooth in Your Healthcare Facility. It explains some advantages of Bluetooth and mentions some uses within healthcare.

Bluetooth can be used as a way of connecting wearables and equipment to other devices. When equipment and people are Bluetooth-enabled, asset tracking and wayfinding become possible. Staff can quickly locate valuable hospital assets and patients in need for urgent care.

Another reason for using Bluetooth is reliability. The article mentions Bluetooth’s adaptive frequency hopping (AFH) that makes communication more reliable in noisy wireless environments. You can read more about the technical aspects in our post on Bluetooth LE on the Factory Floor.

A further reason for using Bluetooth, particularly Bluetooth LE, is low power. Stand-alone devices can work on coin-cell batteries for many years.

The final reason given for using Bluetooth is the ability to create larger site-wide networks using Bluetooth mesh. Mesh can be used for control, monitoring and automation systems without the need for WiFi that can be unreliable and congested in hospitals.

For a further look at usecases, see the post on RTLS in Healthcare.

RTLS in Healthcare

There’s a new Mr Beacon video interview with HT Snowday, VP of Innovation and Technology Development at Midmark RTLS. Midmark and HT are formerly of Versus Technology who were acquired by Midmark in Aug 2018.

Midmark RTLS uses a combination of infra-red, 433Mhhz RF, WiFi and Bluetooth to provide tracking of healthcare assets, care givers and patients. It allows medical equipment to be located quickly, key things such as IV pumps to be effectively distributed (par levelling) and the location of care staff and patients to be controlled and monitored. The Bluetooth part of Midmark RTLS is used more for wayfinding using powered, static beacons to mark locations. Systems also allow for health workflow processes including self-rooming to reduce waiting and queuing for care.

Healthcare is increasingly being provided at outpatient rather than inpatient treatment. This is leading to more clinics and treatments centres and the need for technical sophistication to efficiently process patients.

No mention was given to other crucial healthcare usecases we have come across at BeaconZone such as tracking (and temperature) of valuable medicines, tracking porters, wheelchairs and wayfinding from the hospital limits to reception areas.

Read about Beacons For Life Sciences

Using Beacons in Healthcare

Russ Sharer, Vice-President of Global Marketing for Fulham, a manufacturer of energy-efficient lighting sub-systems has written an article in Health Estate Journal (pdf) on the use of iBeacons in healthcare.

Russ says it’s often difficult to find life saving equipment in hospitals and many organisations have to compensate by purchasing more equipment than they need. However, in use, equipment still gets misplaced, usually just at the critical time it is needed. He explains how the use of Bluetooth beacons and mesh can solve this problem. The article provides a great introduction to iBeacons and some issues such as the affect of frequency of transmission on battery life.

While the article mentions Bluetooth Mesh and iBeacons, these specific technologies don’t always have to be used. Gateways can be used instead of mesh to allow greater throughput of data. Also, any beacons, not just iBeacons, can be used as it’s usually the MAC address of the beacon that’s used for identification purposes. Using sensor beacons allows further scenarios, for example, monitoring the temperature of expensive medicines.

There are also many more scenarios for the use of beacons in healthcare than are mentioned in the article. Our beacons are being using to track hundreds of dementia patients. We have also been involved in a project to use beacons for navigation in large hospitals. Once there’s a network of beacons in a hospital, it’s possible to add lots of widely varying solutions.

Read About Beacons in Life Sciences