USB stick modems significantly faster than older GSM modems

USB stick modems significantly faster than older GSM modems SearchSearch
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ashot shahbazian
New member
Username: Animatele

Post Number: 47
Registered: 06-2004
Posted on Monday, October 12, 2009 - 09:19 pm:   

Hi Bryce, Des

The subj is from your email newsletter. Does it refer to better performance for GPRS/EDGE/HSPA IP upload/download or SMS send/receive speed is CSD mode as well?

If SMS, do you have any comparative performance data for particular models of USB stick modems via-a-vis com-port modems utilising Wavecom modules?

Thanks!

Kind regards,
Ashot
Bryce Norwood - NowSMS Support
Board Administrator
Username: Bryce

Post Number: 7860
Registered: 10-2002
Posted on Tuesday, October 13, 2009 - 04:34 pm:   

Hi Ashot,

Let me preface some of the enthusiasm in that newsletter with the caveat that it was a marketing production, taking some of our best material off of the Tech Support Blog.

Our marketing and sales people have been in love with the concept of compact USB modems for a long time. In particular, they liked the original Falcom modem ... it worked reasonably well for simple installs, but it was hard to get excited about from a technical perspective.

But ... obviously 3G/HSPA is a big deal if you are sending/receiving MMS, and if you're looking for a 3G/HSPA modem, USB stick modems are the form factor.

So we started looking more closely at these modems.

The downside of these modems is that because they use USB, manufacturer drivers are required.

If you read about our trials with the Huawei E160 (http://blog.nowsms.com/2009/10/sms-and-mms-with-huawei-e160-usb-modem.html), you'll get an idea of the driver issues. We wrote a bashing review of this modem until we realised that it worked just fine as long as its modem software was active concurrently with NowSMS.

We've got some information on the Alcatel X200 that should be posted in the next few days, and it has a somewhat similar issue, just not as severe as the Huawei.

Or consider the Sierra Wireless modems that we've tried (they bought Wavecom), where the install routine does not bother to install a modem driver for the AT command port (http://blog.nowsms.com/2009/09/send-and-receive-sms-and-mms-with_225.html).

That's a bit off the point, but a significant consideration when dealing with these modems. I love COM port modems because these drivers are a non-issue.

Back to the point ...

What really has surprised us was the speed difference with regard to SMS in CSD mode, even in areas with only 2G network coverage (technically 2.5G coverage, but we shouldn't be using the .5G part if sending SMS in CSD mode).

We're not seeing the SMS over packet switch speeds that we chased after years ago.

But in most cases, we're seeing 2 seconds per SMS per modem without external antennas. Some slower, some faster. Of the bunch, SonyEricsson is slower at 3 seconds per SMS. I did get 40 messages out in a minute via an Option ICON 322 with a strong signal.

Of all of the modems, I'd have to say that it is the Option models that we have been the most impressed with. They seem to have a slight, but consistent performance advantage.

The only downside is that I haven't seen any external antenna support in their products!

What we haven't yet had a good opportunity to test is multiple of the same USB modem on the same system. So far it's been about getting different modems ... and we've tested with multiple USB modems simultaneously, just not multiple of the same modem.

There's a lot more to be tested. And USB drivers can be a big headache.

But it seems that there is some promise. For single modem installations, I have no hesitation.

-bn
ashot shahbazian
New member
Username: Animatele

Post Number: 48
Registered: 06-2004
Posted on Tuesday, October 13, 2009 - 06:54 pm:   

Hi Bryce,

The SMS over GPRS is unfortunately a thing of the past at most networks..

If the signal is strong and that from the closest BS is at least 6-8 dbm stronger than the next strongest sector you can use up to 12 modems per sector in CSD mode without worrying if it would cause trouble to the operator or that your modems would drop messages.

It would be great if you could evaluate performance for several (e.g. 8-12) Option modems, as follows:

- sending concurrently
- receiving concurrently
- sending and receiving concurrently (disable the DLR request flag though, it's useless for modems since the message/DLR dropping is common not only with Sony USB Stick modems but in all others we've tried, when the sending is dense.)

You would be surprised to learn that the combined speed is not at all linear. In other words, if the receiving rate is 1 SMS in 2 seconds - you won't even get close to 4 SMS/sec. on 8 modems if your inbound texts are 100-160 characters each. The other way around, for sending - it does look a lot more consistent, but only in a load-shared scenario.

I also suggest you try it on an old 5-6 year old server and on a modern one. We've noticed a large difference, even though the old server's CPU won't show any noticeable CPU load.

Another caveat it seems is that when you send messages with sender IDs matched to the modem numbers (in other words, an individual message can only submit from one modem) the sending speed is slower by almost an order of magnitude as compared to a "load-shared" scenario where you'd set no Source Address for the outbound batch - even if the Source Addresses in the 1st batch were distributed evenly. Try this:

- set up 8 modems on one server
- send a stream of messages at 2 SMS/sec to these modems - from an outside service (not from the same NowSMS server or the modems)
- send a batch of 80 messages to outside numbers (preferrably 40-80 numbers, not on the same NowSMS server so that you don't get the effect of "Subscriber Busy for MT") with sender IDs going from modem 1 to modem 8 then again, in round-robin fashion.
- measure the time it took to send all 80
- repeat the test to 80 numbers with no Source Addr in the outbound message batch - so that they load-share.
- measure the time it took them to submit. We've seen a BIG difference, especially on an older/slower server.

We've not had time to analyse the modem exchange and come up with a possible reason, but I'm sure you would figure if you tried the tests yourselves. Sending with pre-determined numbers concurrently with receiving is functionality useful for 2-way interworking between networks of different standards, but we've found it difficult to use NowSMS for the purpose because of the slowdown.

Please let me know if we can help with the tests (perhaps send messages for the inbound stream?)

Kind regards,
Ashot