Bluetooth Covid Management Strategies

Bluetooth SIG has a new article on How Bluetooth Technology Is Helping Us Reopen Safely in a COVID-19 World. It describes strategies that use Bluetooth to manage the pandemic including hygiene management, occupancy management, safe treatment solutions, safe facility management, remote patient care and exposure notification systems.

The Bluetooth SIG also has a new draft standard for exposure notification that can be used to allow wearables to participate in exposure notification systems such that provided by Apple and Google. The idea is that not everyone has a ENS capable smartphone and extension to wearables provides a more complete system.

Read about Beacons for Workplace Social Distancing and Contact Tracing

Bluetooth App Insights from VMWare Pivotal Labs

VMware Pivotal Labs recently released Herald open source contact tracing for iOS and Android. Pivotal Labs was previously awarded three contracts worth £4.8m to develop a contact tracing app for the United Kingdom only for it to be abandoned for a new app based on the Google/Apple contact tracing mechanism.

Herald can’t be used for contact tracing unless you are a government agency because 3rd parties can’t publish such apps on the Apple app store. However, Pivotal Lab’s deep work in this area provides many insights into the use of Bluetooth on smartphones. The library itself also has other uses other than contact tracing:

  • Communication apps
  • File sharing between Android and iOS devices, reliably
  • Local ‘same location’ peer to peer applications, such as instant messaging or gaming apps
  • Safety apps
  • Using beacons in high-risk areas, an employee exposure app could accurate record exact exposure to hazardous environments
  • Also using beacons, know where to deep clean if an employee does fall ill at your large campus
  • Check in app – Walk around and be let in to secure areas automatically
  • Rescue app – e.g. for skiing/snowboarding avalanche rescue – find the hidden/non visible person. Could be fire in a large building, or rescue on a tube train

The documentation provides some useful information on technology approaches and OS specific issues.

Some insights:

  • Using scanning for 1-3 seconds with a gap of a few seconds between scanning uses 6-11% battery over 8 hours
  • Android phones’ speed when reading characteristics is significantly slower than write and acknowledge. Using write instead of read reduces the mean window times from above 8 seconds (minutes for some phones) to 0.5 – 4 seconds, depending on the handset. Use write characteristics wherever possible, and cache data to remove any redundant reads.
  • Apple iOS has a bug with background Bluetooth advertising where applications on two backgrounded iOS devices are not notified about each other. Two backgrounded iPhones cannot detect one other.
  • The background timer on Android sometimes gets stuck and might not wake for many minutes.
  • The way smartphones interpret Bluetooth signals to determine RSSI varies across Bluetooth chipsets. Some such as the iPhone 7 use a log approach while others use an inverse distance-squared scale. This affects accuracy if you subsequently use a common formula to derive distance from RSSI.

Read about Beacons for Workplace Social Distancing and Contact Tracing

Social Distancing Bluetooth RSSI Calibration

We previously described how social distance beacons differ from ordinary beacons. Devices advertise AND scan rather than just advertise OR scan. The principle is the same with with smartphones using the Apple/Google Exposure Notification API.

The problem with smartphones is that their transmit and receive capabilities vary widely. The received signal strength (RSSI) is inconsistent across types of smartphone and you can’t determine distance reliably. Apple and Google have mitigated this problem by attempting to create a database of calibration values (csv).

The calibration data is useful for Bluetooth developers creating solutions across devices. However, it’s of no use for 3rd party contact tracing as only Government agencies can use the Exposure Notification API and Apple is banning Covid related apps.

Read about Beacons for Workplace Social Distancing and Contact Tracing.

Social Distancing Technologies Take the Fast Track Through the Hype Cycle

Gartner has a recent update to their research of hype cycles that takes into account disruption caused by the Covid pandemic.

Social Distancing Technology Hype Cycle

Five emerging trends have been identified:

  • Social Distancing Technologies
  • Composable Enterprise
  • AI-Assisted Design
  • Differential Privacy
  • Biodegradable Sensors

Social distancing technologies, related to the COVID-19 pandemic, are taking the fast track through the Hype Cycle and have high impact. Technologies rarely enter the Hype Cycle at the point where social distancing technologies has entered it

Social Distancing Tech

Wearable devices provide more reliable performance than smartphone apps because smartphones’ transmit and receive capabilities vary considerably across types of device. Using defined, known wristbands or lanyard devices eliminate the variances.

Read about Beacons for Workplace Social Distancing and Contact Tracing

England’s Contact Tracing App Now Trying the Apple/Google API

After wasting a lot of money and more importantly time, England has abandoned using the public mobile OS Bluetooth APIs and is now using Apple/Google’s new contact tracing APIs. However, all has not been wasted because the home grown solution included advanced processing of Bluetooth RSSI values that provided for more precise measuring of close contacts.

The problem now is that the Google/Apple solution doesn’t provide access to RSSI and instead makes its own determination of close contact. Developers are forced down the path of a closed solution that can’t be improved upon. The new app is worse at determining distance than the original NHS Covid-19 app:

Engineers are still trying to reduce how often the Bluetooth-based tech wrongly flags people as being within 2m (6.6ft) of each other

RSSI is very noisy due to radio multi-path distortion, reflection, shadowing and fading. It also varies due to differences across devices in transmit and receive capabilities.

Variation of RSSI in devices and due to the environment

We have previously mentioned the use of Kalman filtering to improve the processing of RSSI. A newer research paper by The Alan Turing Institute of University of Oxford Inferring proximity from Bluetooth Low Energy RSSI with Unscented Kalman Smoothers describes the processing of RSSI to infer close contacts. The BBC believes this is what was used in the older NHS app.

The paper shows show how good prediction of proximity and risk can be obtained by using RSSI sequences rather than applying thresholds to single values. This correlates with our findings in that our Bluetooth contact tracing solution uses sequences rather than value thresholds. The paper also mentions that the duration of the risk also makes some close contacts more important to classify correctly. Again, we concur in that our solution has the ability to contact trace based on contact duration.

England’s contact tracing is now heading in a better direction and in the direction we previously advocated. They now need to persuade Apple and Google to improve their solution.

Effects of Obstructions on the Accuracy of Bluetooth Contact Tracing

David Labrique1, an independent researcher, has a new paper on the Effects of Obstructions on the Accuracy of Bluetooth Contact Tracing.

Bluetooth Contact Tracing

He looks into the variation of Bluetooth received signal strength (RSSI) due to different types of obstruction such as walls and the human body. He explains how RSSI is being used in contact tracing apps and asks whether it’s possible to have false positives when there’s wall between smartphones or false negatives when people are close together but blocked by their bodies.

David used a Raspberry Pi as a Bluetooth emitter and a smartphone as a receiver, situated 1 metre apart and placed various obstacles between them. He found that drywall and stud walls were ineffective at reducing Bluetooth signal strength. Conversely, human bodies drastically reduce Bluetooth signals.

He concludes:

Smart watches might be possible candidates for more accurate contact tracing as they are less obstructed by the body when worn on the wrist

It’s well known that human bodies block Bluetooth. We have an article that explains how this phenomenon can even be used to infer direction.

What David didn’t do was test at different levels of power output. We assume he just used full power which will go through walls. Solutions such as our CATT use lower power predominantly to save battery life but also because there’s no need to transmit further. There’s are also factors at play in a smartphone app such as the variance of signal power across transmitting smartphone, the variance in the ability of different smartphones to receive the signal and the ability (or not) of smartphones to be able to transmit and receive in background when the app isn’t showing/running. These factors make app based contact tracing even more unreliable. Stand alone devices, such as smart watches mentioned by David, work better.

Social Distancing Beacons

Social Distance Wristbands Help Keep Sites Operating

As offices and sites re-open and people go back to work, it’s necessary to introduce social distancing measures in the workplace. We are hearing of factories being shut down after site-specific infection. Poor social distancing measures ultimately jeopardises the continuity of work in your organisation.

No matter what measures you put in place there will be some workers who flout the guidelines and others who are so engrossed in work that they forget about social distancing.

Social distance wristbands and lanyard wearable devices remind workers to maintain social distancing. Complete solutions allow close contact events to be taken off the distance wristband each day to audit compliance and if necessary, perform contact tracing.

Read about Social Distance Wristbands for Workplace Social Distancing and Contact Tracing

Restaurant of the Future

With restaurants and pubs here in the UK scrambling to reopen this weekend, they need to find ways to provide self-service and minimise contact with staff. It’s interesting to see what was considered a ‘future restaurant’ in 2014 makes much more sense today:

The concept restaurant at Eggcellent in Tokyo used iBeacons for the location aspects together with smartglasses, augmented reality and gesture interfaces. An Engadget article covered the restaurant in more detail.

Read about Using Beacons in Hospitality

UK NHS Covid-19 Contact Tracking Source Code Available

The UK NHS has just released the Android and iOS source code for the UK NHS Covid-19 contact tracking app. This is the code used before the recent switch to the Google/Apple mechanism.

The iOS readme explains how it works:

Our unique identifier is also known as our service characteristic. In the Bluetooth spec, devices can broadcast the availability of services. Each service can have multiple characteristics. We use a characteristic to uniquely identify our service and distinguish from all other sorts of Bluetooth devices. For every device we find with a matching characteristic, we record an identifier for the device we saw, the timestamp, and the RSSI of the Bluetooth signal, which will allow a team later on to determine who was in close proximity to individuals infected with the novel coronavirus

UK Moves to Google-Apple Social Distancing API

Just under a month ago we wrote about Bluetooth RSSI, Social Distancing and Contact Tracing and how the UK Government was going their own way:

Google and Apple have implemented a new API to allow contact tracing apps to work well on iOS and Android. Some Governments, such as ours in the UK, have currently gone their own way with apps that use existing APIs. Such aforementioned restrictions stop smartphones seeing each other thus severely reducing their effectiveness. The apps won’t work properly and will provide very limited benefit.

We are not surprised that Sky News is reporting that there has now been a U-turn.

To all governments trying to use the standard iOS and Android APIs to measure social distancing and perform contact tracing: You are wasting important time.

Read about Beacons for Workplace Social Distancing and Contact Tracing