Experience report: Using Modems für GSM/GPRS M2M Solutions

Hi

I'd like to share some of our experiences implementing a
SMTP-Application using a serial modem.


Please see my other Threads in http://www.modem-gsm.de/forum for
detailed descriptions of our problems with the Telit modem.


We startet with the Telit Modem PCS-Version. After some time we had
major problems with the internal timing in the modem. Some at-Commands
must be handled very carefully not to make the Telit modem hang. for
example: you ask the modem if it is connected to the gsm-network
(at+creg), if the modem isn't registered on the modem and you fire
the command that it should tell you that it has registered (unsolicited

result), then Telit modem sometimes shutdown completely and you need to

power it off/on to get it back to work. There are other circumstances
when it crashed and you need to power off/on.
But when you get the timing right it will work.
Then we implemented the SMTP-Protocol (using the Indy stack) because we

needed some extra functionality. The problem there is, that the modem
will work fine, but in the middle of the transmission it will send a
break signal and crashed, we weren't able to find out why and how to
prevent it from crashing. We asked Telit but they weren't able to
reproduce the problem. So we hadn't a solution for 6 months.


After waiting for Telit we decided to try a different vendor. So we
tried SonyEricssons GM29. No timing problems there but a major bug in
the TCP/IP stack. It will not send a TCPIP datapackage if it is smaller

than 300 bytes. There is no way telling the modem to send a small IP
telegram. SE service was very friendly, they can reproduce the problem
but we are now waiting for 4 weeks and no fix available. They also told

us that the gm29 will be discontinued and the followup product isn't
available yet.


So we tested the wavecom fastrack M1306B. And here we are, modem works
find, no timing problems, the IP-Stack works as well, we are able to
send huge EMails. In addition the commandset is much bigger than
Telit's or SEs and there is useful description and examples.  At the
moment we are testing more functions and it looks good.


This is a real experience report, we are not on the wavecom payroll !


if you like to contact us please feel free to send us an EMail:
publicfr...@connective.biz. we would be happy to help or to discuss
some issues. 


  Kind regards 
    Ruediger

Ruediger wrote:
> Hi
>
> I'd like to share some of our experiences implementing a
> SMTP-Application using a serial modem.
>
>
> Please see my other Threads in http://www.modem-gsm.de/forum for
> detailed descriptions of our problems with the Telit modem.
>
>
> We startet with the Telit Modem PCS-Version. After some time we had
> major problems with the internal timing in the modem. Some at-Commands
> must be handled very carefully not to make the Telit modem hang. for
> example: you ask the modem if it is connected to the gsm-network
> (at+creg), if the modem isn't registered on the modem and you fire
> the command that it should tell you that it has registered (unsolicited
>
> result), then Telit modem sometimes shutdown completely and you need to
>
> power it off/on to get it back to work. There are other circumstances
> when it crashed and you need to power off/on.
> But when you get the timing right it will work.
> Then we implemented the SMTP-Protocol (using the Indy stack) because we
>
> needed some extra functionality. The problem there is, that the modem
> will work fine, but in the middle of the transmission it will send a
> break signal and crashed, we weren't able to find out why and how to
> prevent it from crashing. We asked Telit but they weren't able to
> reproduce the problem. So we hadn't a solution for 6 months.
>
>
> After waiting for Telit we decided to try a different vendor. So we
> tried SonyEricssons GM29. No timing problems there but a major bug in
> the TCP/IP stack. It will not send a TCPIP datapackage if it is smaller
>
> than 300 bytes. There is no way telling the modem to send a small IP
> telegram. SE service was very friendly, they can reproduce the problem
> but we are now waiting for 4 weeks and no fix available. They also told
>
> us that the gm29 will be discontinued and the followup product isn't
> available yet.
>
>
> So we tested the wavecom fastrack M1306B. And here we are, modem works
> find, no timing problems, the IP-Stack works as well, we are able to
> send huge EMails. In addition the commandset is much bigger than
> Telit's or SEs and there is useful description and examples.  At the
> moment we are testing more functions and it looks good.
>
>
> This is a real experience report, we are not on the wavecom payroll !
>
>
> if you like to contact us please feel free to send us an EMail:
> publicfr...@connective.biz. we would be happy to help or to discuss
> some issues.
>
>
>   Kind regards
>     Ruediger

We have some years of experience using the GR47 (a superset of the
GM29) M2M device, and your description seems to be one based on perhaps
a few weeks of  testing.

The bottom line for the GR47 is it is a great device, but now not
available (nor will the GM29 as far as I know) as it's not RoHS
compliant. Replacement is the GR/GS64 for the GR47.

Great as it may be, as soon as I found out the Sony-Ericcson M2M
business had been bought by Wavecom, I designed it out. I will use the
GR64 for existing designs (because I had to change the design to
accomodate it - it is NOT a pin for pin replacement), but when those
products get superseded (in about 3 months), they're out.

I won't touch Wavecom with a 10 foot bargepole.

Cheers

PeteS

We have used a number of GSM modules for designs over the past 7 years.
My conclusions are that they seem to be getting better but there are
still problems for M2M use where reliability is everything. I have yet
to find a GSM module that stays powered and logged onto the network
succssfully for an extended period of time. In general we always
include the facility to power down and reset the GSM module by using a
small, low-cost micro with an external watchdog on the micro.
We have used a number of manufacturers and I have spoken to people
using other devices and their experiences are similar.
On TCP/IP we have used Siemens TC45 with Java. This has been
discontinued due to RoHS compliance issues and has been replaced with
the TC65.
It seems that GSM modules are replaced frequently but in general
Siemens seem to have the replacement available whereas we have had
problems with Ericsson discontinuing products without having
replacement product available.

Iain

www.claritech.co.uk

Hi PeteS

Thanx for your reply.

Are you using the TCPIP Stack? Did you have any problems defining the
timeout for transmitting IP-Packets?

The point with the GM29 was that it did not send the IP-Packet if it
was less than the minimum size even if we waited for minutes. We
implemented a SMTP Protocol and there you need to send small chunks of
data like <HELO domain>  to tell the SMTP-Server who you are. The
Problem was that GM29 did not send that packet and the SonyEricsson
service was unable to find a fix. They said: "Yes we can reproduce the
problem." And then they went silent. Because we had a deadline on the
project we need to find a solution and Wavecom modem do work well.

But you are correct i do only have about 5 days of experience with the
GM29 because it didnt solve our problem.

Bad thing is: Sony Ericsson didnt find a solution till now and thats
now 2 months and 5 days.

If you have any experience with the Wavecom modem i would be happy to
know the bad ends of that device. That can save a lot of time.

Thanks and kind regards
  Ruediger

Ruediger wrote:
> Hi PeteS
>
> Thanx for your reply.
>
> Are you using the TCPIP Stack? Did you have any problems defining the
> timeout for transmitting IP-Packets?
>
> The point with the GM29 was that it did not send the IP-Packet if it
> was less than the minimum size even if we waited for minutes. We
> implemented a SMTP Protocol and there you need to send small chunks of
> data like <HELO domain>  to tell the SMTP-Server who you are. The
> Problem was that GM29 did not send that packet and the SonyEricsson
> service was unable to find a fix. They said: "Yes we can reproduce the
> problem." And then they went silent. Because we had a deadline on the
> project we need to find a solution and Wavecom modem do work well.
>
> But you are correct i do only have about 5 days of experience with the
> GM29 because it didnt solve our problem.
>
> Bad thing is: Sony Ericsson didnt find a solution till now and thats
> now 2 months and 5 days.
>
> If you have any experience with the Wavecom modem i would be happy to
> know the bad ends of that device. That can save a lot of time.
>
> Thanks and kind regards
>   Ruediger

Our experience with the TCP-IP stack is very positive, although there
are some unusual bugs in the GR47. Sony-Ericsson (now Wavecom) aren't
working on that as it is a discontinued product and all effort is going
into the GR64/GS64 for OEM modules.

I will say that the onboard implementation works better than either the
Linix or WinCE stacks.

As to discontinuing product, expect that to get worse now Wavecom owns
them (just my personal opinion).

Cheers

PeteS