Multi-hub environment with mobile sensors

sev

I am aiming to use MetaSensors attached to mobile subjects in a building so am looking at deploying gateways / hubs throughout the building (they are used for other purposes anyway). 

I am curious if anyone has worked on a project like this with multiple gateways and what are your experiences / advice? 

Some questions that come to mind:

How should MetaSensors be configured (log, or stream)?

Should gateways coordinate some sort of handover process?

What are the best practices for graceful termination of connections with sensors?

Any recommendations or thoughts are appreciated.

Eric

1. Depends on your use case.  What are you planning on using the sensors for?
   
2. Again, depends on what you are using the sensors for.  If they are acting as beacons, the hubs don't need to do anything other than continually scan for the ad packets.
3. Once the sensors go out of range, the connection will automatically close.

sev

1. Gait and activity analysis for inpatients. It's expected they won't always be in range of a gateway, but it's a fair assumption that this would be rare.

2. We do not use these sensors as beacons. We will use gyro and accel.

3. How does this affect logging? For example, if connection is lost during log download.

Eric

You can try a hybrid approach where the sensors stream when in range, then switch to logging when connection is lost.  

Alternatively, depending on how long your tests are, you could just only log data then download it after you are done with that experiment.  This calculator will estimate how long you can log data for depending on your sensor settings.

https://mbientlab.com/tutorials/Calculator.html

The firmware will resend the remaining log data though it may also resend some data.  Normally the SDKs will filter this out but if another device resumes the download, you will have to filter out the duplicate data yourself.

sev

Yes we will need to do some experiments. 

Regarding the hybrid approach, how could one do that? Using the disconnect handler function https://mbientlab.com/cppdocs/latest/settings.html#handling-disconnects ?

Eric

Yes, use the disconnect handler to start the logger when connection is lost.   When connection is restored, your connect callback can stop the logger.