Modem initialisation string question

buffalobill

buffalobill

Senior Member
Joined
Jun 20, 2004
Messages
844
I've been thinking that maybe one can tweak the modem init string for better performance. I see that there's an extra string: AT+CGATT?<cr><lf>AT. Removing it seems to make no difference. Any idea what this does? Any thoughts on improving performance this way?

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
I have an inferiority complex. But it's only a little one.
 
TheRoDent

TheRoDent

Cool Ideas Rep
Joined
Aug 6, 2003
Messages
6,218
Not performance related at all. The AT+CGATT? queries the modem to display the currently connected tower and frequency.

AT+CGATT can also be used to set the frequencies that the modem should operate on, but it appears to use these instructions purely as "hints", and latches on to what it believes is the strongest signal it can find automatically.

For a full listing of the known modem commands and their functions, check http://rodent.za.net/MyModemCommands


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buffalobill

buffalobill

Senior Member
Joined
Jun 20, 2004
Messages
844
Maybe that string makes a marginal difference. I've been buggering around and trying a few things. Here's my test report. Any comments?

Test on Modem extra initialisation command

Ran PCPitstop (http://pcpitstop.com/internet/Bandwidth.asp) speed test with this string:
AT+CGATT?&lt;cr&gt;&lt;lf&gt;AT

1. 31 kilobits/sec
2. 64 kilobits/sec
3. 30 kilobits/sec
4. 21 kilobits/sec
5. 44 kilobits/sec
Average: 38

Removed the string and ran PCPitstop 5 times:
1. 17 kilobits/sec
2. 21 kilobits/sec
3. 92 kilobits/sec (!)
4. 46 kilobits/sec
5. 31 kilobits/sec
Average: 41.4

Put the init string back and ran Internet Speed Autofix (http://www.pcpitstop.com/pcpitstop/autofix.asp?file=IntSpeed.hta) to set receive buffer size at 64240.

1. 24 kilobits/sec
2. 21 kilobits/sec
3. 40 kilobits/sec
4. 36 kilobits/sec
5. 34 kilobits/sec
Average: 31

Terrible, so I set receive buffer size at 32120:
1. 30 kilobits/sec
2. 36 kilobits/sec
3. 25 kilobits/sec
4. 30 kilobits/sec
5. 44 kilobits/sec
Average: 33

Marginal difference and not significant. So, let’s try buffer size 32120 without that modem string:
1. 39 kilobits/sec
2. 48 kilobits/sec
3. 51 kilobits/sec
4. 26 kilobits/sec
5. 27 kilobits/sec
Average: 38.2

Better, so let’s try no init string and buffer of 62240:
1. 33 kilobits/sec
2. 43 kilobits/sec
3. 19 kilobits/sec
4. 34 kilobits/sec
5. 28 kilobits/sec
Average: 31.4

No good so let’s go back to the Windows default and try this reg edit thing at http://www.dslreports.com/faq/dial/7+Dial-Up+Tweaks:

1. 20 kilobits/sec
2. 16 kilobits/sec
3. 16 kilobits/sec
4. 16 kilobits/sec
5. 10 kilobits/sec
Average: 15.6

Well that was a disaster. Restore the registry. As a control, let’s now try that test without the string and with normal settings again:

1. 27 kilobits/sec
2. 62 kilobits/sec
3. 30 kilobits/sec
4. 49 kilobits/sec
5. 21 kilobits/sec
Average: 37.6

Once again with that init string re-inserted:
1. 27 kilobits/sec
2. 39 kilobits/sec
3. 29 kilobits/sec
4. 28 kilobits/sec
5. 44 kilobits/sec
Average: 33.4

Both times performance was marginally better without that string although speed was all over the place, peaking at 92kbps. I’m going to leave it out. It seems to make a small difference.



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I have an inferiority complex. But it's only a little one.
 
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