Experience report: Using Modems für GSM/GPRS M2M Solutions


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

Please see my other Threads in

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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: snipped-for-privacy@connective.biz. we would be happy to help or to discuss some issues.

Kind regards Ruediger

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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.



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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 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

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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.


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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).



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