[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: connection speed when using pon

On Monday 31 January 2005 13:06, John Hasler wrote:
>I wrote:
>> But they do not take into consideration the compression done by
>> the modem.
>Gene Heskett writes:
>> Oh, but it does.
>Those numbers represent the raw bit rate (not baud rate) between the
>modems.  The effective data transfer rate can be much higher but
> depends on the compressibility of the data.
>John Hasler

I hate to disapoint you John, but the modems are doing all possible 
amounts of compression to achieve the data rates they advertise.  The 
compressions they use are not the same as the equ of bzip2, and work 
in the phase & amplitude domains of the signals exchanged in order to 
achieve a 56k download rate on what is, according to bandwidth 
theory's carved in stone back in the late 50's by some very smart 
people in information theory at bell labs as to the maximum data rate 
that can be sent over what is basicly a 2400 hz of bandwidth circuit.  
That 56k is the data rate through the most restrictive piece of the 
transmission path, the POTS line to the CO, and is what you will get 
over any period long enough to calculate an average from, such as any 
one 10 second period, measured at the computers side of the modems on 
either end.

I believe a fellow named Robert Heinlein said it best when he 
popularized the phrase/acronym TANSTAAFL 40 years ago.

Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
99.32% setiathome rank, not too shabby for a WV hillbilly
Yahoo.com attorneys please note, additions to this message
by Gene Heskett are:
Copyright 2005 by Maurice Eugene Heskett, all rights reserved.

Reply to: