Simple question:
Does Sierra Wireless modules (Q26, SL6087, SL80xx) properly send RP-SM-MEMORY-AVAILABLE to the network after deleting SMSes from a full SIM-card?

This question has come up after comparing to various cell-phones, what happens if an SMS is sent to the module (or cell phone) when the SIM-card (or other storage area) is full, and an SMS is sent.
On the sending side I get a report saying that the SMS can’t be delivered right away.

If I then delete SMSes on the cell phone, the SMS is delivered almost right away.
If I delete SMSes on Q26/SL6087/SL80xx however, I have to wait at least 10 minutes before the SMS is delivered.

10 minutes is the SMSC default retry time obviously, but this discrepancy seems to indicate that the SiWi modules does not notify the network that it can receive new SMSes.

This can also be noticed when the SMS is send while module or cell phone is turned off.
On cell phone, the SMS tends to get delivered right away when it logs in to the network, but SiWi modules have to wait for the SMSC to retry normally…

Any guidance from Sierra or anyone else that knows more would be welcome.

Side question:
Does anyone know if cell phones usually send an RP-SM-MEMORY-AVAILABLE to the network during startup?


Revision to above post…

If Q24/Q26/SL6087 module is turned off by simply removing power, then it takes time for SMS to arrive when it is turned on again.
If those modules are turned off properly by using AT+CPOF before removing power, then the SMS arrival time seems to be on par with cell phone.
This indicates that proper de-registration from the network is necessary.
I’m guessing that the network in this case is able to send a RP-ALERT from the HLR to the SMSC if and only if the module de-registered properly before shutdown.

Seems to work fine on SL809x as well after correct shutdown procedure was used.
AT+CFUN=0 was sent on MODEM port instead of AT Command port.


Yes - it certainly is!

Remember that pressing the “Off” button on a cellphone does not cut the power - it simply starts the detach-and-then-power-down sequence.

For a comparative test on a cellphone, you would have to just pull the battery out while it was running…


After checking with my colleagues, it seems that they were sending AT+CFUN=0 on the MODEM port instead of the AT Command port.
The MODEM port just answers OK for most commands.
So the only “issue” at hand is the difference in time it takes for SMS to arrive when going from full SIM to empty SIM.


You can chalk up some of the confusion about this to firmware 7.44.0…
Even when issuing AT+CPOF and waiting for OK before powering down, it seems that network deregistration is not handled correctly.

One of my colleagues compared R7.44.0 and R7.46.0 and noted that even with correct shutdown procedure he could get 5-15 minutes wait for SMS to arrive after starting up again on R7.44.0 while on R7.46.0 it took at most 20 seconds from power on until the SMS arrived.

Testing performed several times on both firmwares to rule out that it was only temporary on R7.44.0.