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3Com's "Gamer" Modem Pings Faster?
An anonymous reader pointed us to 3Coms Gamer Modem:
they claim faster ping times and better online play. I'm more than a little skeptical here, does anyone have more info?
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Actually, it is much more sophisticated then simply detectecting dead frequencies, and moving the signal around, and in fact it was thought of sooner, and has been done for a long time.
Think of the signal coming in as a spectrum (like winamp shows you in it's default mode). This is basically a bar graph, with frequency along the bottom axis and power on the side axis. When somebody starts jamming on their bass guitar, you get bumps in the low frequency end. When they start playing the flute, you get bumps in the high frequency end.
As a side note, I believe mp3 encoding takes advantage of this concept to achieve it's high compression rates. It (metaphorically) saves the height of the bands, and reproduces those on playback. The higher the number of (more narrow) bands, and the more accurately you measure their height, the better your sound reproduction.
Any transmission medium will distort this spectrum to some degree. If you look at the spectrum on the sending end, and the spectrum on the receiving end, you will see it changed.
Your average phone line has a pretty narrow spectrum that it can transmit. I think it ranges from about 500hz at the low end, to 3500 hz at the top end. A normal CD reproduces sounds from 20 hz to 20000 hz. Unless you are a pre-pubescent female, you likely can't hear much above 15000 hz. ( hz=Hertz, cycles per second).
So anyway, if you want to get more bandwidth (lower lows and higher highs getting crammed through a phone line), there is a neat trick to doing it (which is also used by Bose on several lines of their speakers with great results).
1) Send a known signal through your transmission medium.
2) Receive that signal, and compare it to what you sent.
3) Before you send your next signal, pre-distort it, so that when your transmission medium reshapes it, it ends up at exactly the shape you wanted in the first place.
It's kind of like buying jeans that are not pre-shrunk... by them long, so that when they shrink after being washed they end up the size you wanted.
Simple, huh?
The reason this is becomming more and more common, and that data rates are so amazingly high for such lousy transmission mediums like phone lines, is that heavy duty signal processors are just now becomming affordable enough to embed in consumer devices. It's been around for quite a while, you just could not afford it.
Signal processors (DSP = Digital Signal Processors) are simple computers that have very limited functionality but do their job blindingly fast. This functionality is now to the point where it can be embedded in a single chip, and sold for a few bucks, but the engineering that goes into these things is staggering.
There are other methods of error correction that were necessary to get data rates up the 56k speeds we now see, but they are pretty complicated.
Bill Kilgallon
Mathematically impossible requirements are technically not against policy.
Hi!
I'm an engineer in the 3Com modems group. The Game Modem is optimized for small packet sizes. Most games use tiny packets to indicate stuff like rudder position and etc, so this works better. Of course, short-packet pings fall into this category, too. Also, we ship it with some quite nice games in the box.
And, yes, it works just fine for the traditional things you use a modem for.
Happy Halloween!
Dog is my co-pilot.
Consider for a moment that compression has a time delay factor intrinsic within it--the longer one waits, the more redundant data can be filtered out of a transmission block.
Modems, by default, execute Run Length Encoding(RLE) algorithms, which if I remember correctly are statements along the lines of "Here's a string of 64 0's" instead of literally sending the stream of 0's.
Of course, to *know* one is sending 64 0's, one has to operate on a 64 byte delay. So a key strategy for reducing lag is actually sending those 64 0's live rather than waiting the delay period.
This isn't really a bad idea--waiting for the delay period when highly tuned networking applications which would *never* send such a "low entropy"(translation: almost devoid of unique information content) string is foolish.
Now, disabling modem compression is a well known tactic for decreasing ping time, and tools have been out to reconfigure Windows to do thus for years. That doesn't necessarily mean, however, that all these modems have different is a new driver disk.
56K modem technology has been described as the biggest technical hack the industry has ever seen, and I'm inclined to agree. That it works at all is near-miraculous(although actually it doesn't really go as fast as advertised, thus 3Com's upcoming $5 coupon slap on the wrists for claiming net connections would be twice as fast).
Intrinisic in the protocol are error-checking codes. Error checking *also* introduces delays, as you need to wait for the data to come in before you can sum it. Reduce your error checking, or decrease the check interval, or tweak in any number of hacks, and lag can decrease.
Also intrinsic is connection recovery--by speeding this up, making this more effective, or both, 3Com gets an edge. That there appears to be specific functionality reserved for specific ISP hardware leads me to suspect there's off-standard code being put into use.
This isn't necessarily bad.
I'd be interested in more technical documentation as to what they've done--anyone from 3Com got a real link for the rest of us?
Yours Truly,
Dan Kaminsky
DoxPara Research
http://www.doxpara.com