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.

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Hospital Asset Tracking

There’s a new article on MyLondon on How this Putney hospital is using smart technology to track down life-saving equipment. It explains how Putney hospital is using sensors to track equipment, such as ECG machines, to make them easier to find. They are also monitoring the temperatures of fridges and the occupancy of rooms.

Hospital Asset Tracking Using Bluetooth

The time saving is incredible… there are thousands of more things the hospital would want to track in the future

Toby Roberts, Putney Hospital Associate Director of Information

At BeaconZone we have customers using beacons to track wheelchairs, porters carrying medicines and the location of vulnerable Alzheimer’s patients.

We have found the main problem with introducing new technology into hospitals is lack of funding. Anything outside purchasing for the frontline is de-prioritised. Health providers tend to have have blinkered priorities that work against efficiency and cost savings.

If you think about having three key nurses and a couple of health care assistants running around the hospital for half an hour to find a piece of equipment, even if you just add up their hourly rate, let alone the increase in service quality, it’s really quite an easy equation to justify

Toby Roberts, Putney Hospital Associate Director of Information

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Fitness Band with Heart Rate and Body Temperature

We have a new beacon, the 1810G in stock that monitors both heart rate and body temperature.

Heart Rate and Temperature

This fitness band can provide real time steps, heart rate or temperature. It also stores the historical data. Data is obtained by connecting programmatically to the device, via Bluetooth GATT, from Android, iOS or other Bluetooth LE device.

Can be set up to provide for social distancing reminders, tested every minute, when two bands of this type come close together (2m).

Being programmable it allows for new usecases such as monitoring groups of people. This might be used, for example, to identify those with an elevated body temperature.

There’s also an iOS and Android app for normal consumer use.

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Using iBeacon to Assess Elderly Frailty

There’s a research paper by Thomas Tegou, Ilias Kalamaras, Markos Tsipouras, Nikolaos Giannakeas, Kostantinos Votis and Dimitrios Tzovaras of Information Technologies Institute, Greece on A Low-Cost Indoor Activity Monitoring System for Detecting Frailty in Older Adults.

The paper describes a room-level accuracy indoor localization system, based on Bluetooth RSSI, to assess the frailty in older people.

The implementation used smartphones as detectors:

The researchers identified features to classify degrees of movement between rooms:

The system was able to determine rooms to an accuracy above 93%. The results showed subjects with frailty had distinctive movement patterns that could be identified with high accuracy of 98%.

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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