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boliveira
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Posts: 7
Joined: Wed Jul 20, 2011 1:31 pm

LTE mobility problems on RB912UAG-2HPnD with MC7710

Thu Jul 17, 2014 2:15 pm

Hello,

The problem is that i am using RB912UAG-2HPnD with Sierra Wireless MC7710 (fw 3.05.23.02) inside vehicles. Unfortunately the RouterOS have a few implementation problems on this scenarios with mobility.

The first problem is that the LTE interface with the "Network Mode" setting on auto, it takes to many time to connect to a 3G network if the 4G network isn't available. Besides the time it takes to downgrade, when it does, it stays on that technology even if a better network is available again. The problem is that when the modem connects to GSM tech it says on it forever, it only upgrade again if i restart the LTE interface or power reset the modem.

This on a scenario where the Mikrotik is inside a vehicle, with constant change of the access technologies, doesn't work as expected.

The other problem that i am facing is with the GPS on the MC77110. After some time the GPS stalls and it will only work again if i power reset the modem. This is again another problem because when i reset the modem it takes a few seconds to come back again plus if there is no 4G access it will wait to timeout to connect to 3g, this takes around 30+ seconds where the users lose connectivity.

The question is, can the LTE Network Mode selection be improved, so the downgrades can be more transparent and support access tech upgrades when there are better technology available?

Also is there any way to deactivate the GSM mode? i am using a script that from time to time it checks if the LTE interface is on GSM and if it is the script restart the LTE interface, it works but it is not an elegant solution.

Kind regards,
Bruno
 
RogerWilco
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Joined: Wed Feb 16, 2011 6:02 am
Location: Australia

Re: LTE mobility problems on RB912UAG-2HPnD with MC7710

Fri Jul 18, 2014 2:21 am

Also is there any way to deactivate the GSM mode? i am using a script that from time to time it checks if the LTE interface is on GSM and if it is the script restart the LTE interface, it works but it is not an elegant solution.
You can block GSM altogether via the SW modem. Not sure if that is ideal. Basically, the modem will pretend it can't pick up GSM.

AT!SELRAT? will return the current radio access technology (RAT). By default, it should be set to 00 - automatic.
AT!SELRAT=? will show what the modem can connect to.

To force it to LTE, use AT!SELRAT=06
To force it to 3G or LTE, use AT!SELRAT=11

Again, not sure if that is ideal because the modem won't be able to connect to a GSM tower unless you set it to another RAT ID or back to automatic.
 
boliveira
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Posts: 7
Joined: Wed Jul 20, 2011 1:31 pm

Re: LTE mobility problems on RB912UAG-2HPnD with MC7710

Fri Jul 18, 2014 2:16 pm

RogerWilco thanks for the reply.

I think that network access type verification should be done automatically by routerOS by using AT commands like "AT!SELRAT=?" and do the technology transitions more smooth. But the feature that i really needed is the ability for the routerOS detects that there is a better technology available than the current one and switch to it, something similar to what our mobile phones do and other 4G routers on the market.
The thing is with LTE interface i can't execute AT commands and read the return values, the only think i can do is to put AT commands on the "Modem Init" option.

I really like to use routerOS on this scenarios because of the flexibility, but the LTE access network technologies transitions doesn't work that well.

Kind regards,
Bruno

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