Re: [leshan-dev] Conceptual questions for using LWM2M with NB-IoT

[Simon Bernard <contact@xxxxxxxxxxxxxxx>]

Hi,

1. Registration.

In LWM2M, a device need to register itself to a LWM2M server. The registration(this is a kind of session) contains all information needed by the server to send request to device (e.g the IP address).
Registration has a lifetime, this way the server can clean up unused/expired registration.
To maintain the registration alive and avoid the clean up at server side, the device should "update" its registration before the expiration.

The lifetime of this registration can be set in the device or configured by a LWM2M Bootstrap Server or LWM2M Server. (Object Server(1)/ Resource Lifetime(1))
This is an integer so you should be able to set a lifetime to 12 or 18 months.

2. Observe

> Typically, NB-IoT devices wake up and send
>         date from the device to the cloud and go back to sleep
>       
      This looks like very much to LWM2M Queue mode. When a device uses
      QueueMode (Binding UQ), server considers that device is not
      reachable most of the time. To annonce to the server it is
      reachable again for few (seconds/minutes), a device should send a
      registration update. ( see §8.3-Queue
        Mode Operation)
      
> Does that completely rule out observe use
>         cases for NB-IoT devices? 
      Just to be sure you call "observe", the LWM2M observe request
      mechanism described at §5.5.1-Observe ? Queue Mode is compatible
      with Observe but Observe has several drawback.
      So generally, if this is possible I advice to avoid it. If there
      is no other solution, then go for it.
      
      Simon

Le 02/04/2020 à 01:44, Ralf Rottmann a écrit :

Hi everyone, I hope you guys are doing okay during these times of the pandemic!

We are currently evaluating the use of LWM2M via CoAP for low-powered NB-IoT devices. I have two key questions and would love if anybody could shed some light on those for me.

1. Registration

It is my understanding that typically LWM2M devices extend their registration regularly. However, in a scenario where we have to optimize for battery life, we ideally would eliminate the need to “re-register”. Would it be possible to sort of register devices in the factory (factory provisioning) and configure Leshan in a way that it does not require registration extending for 12 to 18 months?

2. Observe

NB-IoT does not cater for cloud initiated requests to devices. Typically, NB-IoT devices wake up and send date from the device to the cloud and go back to sleep, so cloud initiated requests cannot reach them. Does that completely rule out observe use cases for NB-IoT devices? Will LWM2M really work as expected given this “major” constraint?

Thanks for taking the time to look into this.

Ralf

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