Bluetooth for Contact Tracing Explained

In this article we will break down how SaferMe uses Bluetooth to log mobile contacts for the use of contact tracing


Bluetooth for Contact Tracing - what is required? 

The SaferMe app uses Bluetooth Low Energy (BLE) as a way of logging close proximity contact with another device.

  • Devices must have the SaferMe mobile app downloaded 
  • Devices must have Bluetooth enabled for the SaferMe mobile app
  • The member needs to be logged in to the SaferMe mobile app


Use Case Example


The Bluetooth on Device A will scan for nearby devices and when it picks up another device signal (Device B) it will log a contact on both devices.

As the member is logged in to the mobile app, their login data is associated with a unique user ID. Unique user ID's will display as the names of the members in the front end of SaferMe. 

In a similar fashion, the app is able to use device location / GPS to determine that two member's devices came into contact and log a contact occurrence this way.

However, GPS is less accurate than Bluetooth in determining the distance between member's devices. 


Bluetooth Permissions

For the app to use Bluetooth and/or GPS data to log contacts it requires permission from the devices to do so.

If these device settings are not allowed then the SaferMe app is not permitted to pull any data from the device, so it cannot successfully log contacts between devices.


How Bluetooth Functions on iOS


iOS Note: Examples below are referring to two or more mobile devices with the SaferMe mobile app downloaded, Bluetooth permissions allowed and the member is signed in. 


Bluetooth on iOS devices


On iOS mobile devices scan for other bluetooth mobile devices. The devices will log contact with each other when they connect to each other. 

Devices continue operating with intermittent scans and this enables approximate interaction length to be determined. 

When the SaferMe app is open on the device it does this continuously.  When the SaferMe app is in the background on the device, it will request the device to do it frequently (every 15 minutes).


Challenges on iOS


iOS can deprioritize mobile apps that are not being actively used or are using too much capacity on the device.

Routine use of the SaferMe mobile app can prevent iOS deprioritizing the SaferMe mobile app.

SaferMe members can regularly make reports such as a Daily Check In and can scroll through the feed to catch up on updates posted by the organization. 


Reactivate SaferMe Notification


Additionally SaferMe has configured for iOS members to receive a "reactivate app" notification every 1-2 days. This act of simply opening the app helps the operating system to re-prioritize SaferMe.

It is similar for GPS where iOS can trace device contacts intermittently with current location if available. 


How Bluetooth Functions on Android


Android Note: Examples below are referring to two or more mobile devices with the SaferMe mobile app downloaded, Bluetooth permissions allowed and the member is signed in. 


Bluetooth on Android devices

On Android the SaferMe mobile app is able to continuously to receive bluetooth signals. When it goes into "background" mode it can continue running the same as foreground mode with a foreground notification.

One thing to note about Android is that this operating system uses location services (GPS) to drive its bluetooth function. On Android the device detects another device in proximity, and "logs" that contact.

The data reflecting the occurrences of contact are sent from each device to the SaferMe server intermittently. It is encrypted in transmission and encrypted when it is stored.

The contact log data is then reflected in each person's individual contact table.  

Each member has their own individual contact log table. To read about Contact Log Tables in full visit our knowledge base article here. 


If you have any questions about Bluetooth for contact tracing contact