frequency division multiplexing

April 13, 2009 at 22:16:27
Specs: Windows XP
does fdm splits the speed of the channel?? i mean suppose,there are 4 hosts using FDM to share a 10 Mbps will now this speed be divided or wat?? it will obviously split the bandwidth, but is it true about speed also??

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April 14, 2009 at 06:39:55
electrical flow across a wire is a constant - just slightly shy of the speed of light. "Speed" is a constant.

The oscillation of the waveform [frequency] are different between divisions. This allows multiple waveforms to travel down the same wire at the same time.

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April 14, 2009 at 07:31:12
even i think dat, but accrdng ko a networking author..if a channel has R bps capacity then if N channels are using the channel thrgh FDM , den each channel will recieve a R/N bps speed...refer to "computer networking a top down approach featuring internet..., by kurose and ross..."

in chapter no 5 data link layer...

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April 14, 2009 at 13:11:39
Depends on the system but for the most part each channel has full speed to the media.

Think of it like a guitar playing a G and A note for each 0 and 1 for host 1.
Host 2 has a B and C and so on.
The media has full access to the entire set of tones.

In more complex systems you'd have tone packages. Most would use 4/8 or some multiple of that to assign each channel with a group of tones for each + and - or 0 and 1. A full computer word would be transmitted each clock cycle and could be for each channel at each clock cycle.

"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10

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April 15, 2009 at 06:27:45
i have enough logics (presented by u people as well as my own) to get convinced abt the same speed for each of the channel. but i really can't dare to reject the facts presented in that text..dats a very popular and very recommended book even in IIT's. Please consider this sentence...m writing as in it's original form given in the book...while TDM shares the broadcast channel in time,FDM divides R bps channel into different frequencies. FDM thus creates N smaller channels of R/N bps out of the single,larger R bps very cleary it's stating that speed will be splitted plz tell me is there anything worng m perceiving from it...

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April 15, 2009 at 06:41:21
It NEVER says speed. It says BANDWIDTH. You are mixing the two.

page 12

Bandwidith is the width of the freeway. Speed is the rate the cars go down that freeway. Speed is a constant as explained above. All that matters is the ratio of cars to width of the freeway. More lanes more cars. Less lanes less cars.

You can think of TDM as the stoplight to the freeway on ramp.

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April 15, 2009 at 09:12:34
actually we are messing up wid two confused computing world the term speed is somehow used wrongly for the term bandwidth...i dnt think we have a formal definition for speed apart frm that of bandwidth...first of all tell me hw u can differentiate the speed frm bandwidth?? suppose i have 10 Mbps lan, den wat is bandwidth and wat is speed here?? u can extend this by taking an internet connection of 2 Mbps and having and internal lan operating at 10 u tell wat's the speed and wat's the bandwidth???

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April 15, 2009 at 09:36:08
speed is how quickly you can move a file from point A to point B @ bandwidth is = to 10mb [or whatever] measured in the time to xfer.

The real difference comes to light when you staturate your bandwidth. You can have one file download in 1 minute or you can have 10 files download in 1 minute.

And yes there is a lot of confusion in the industry concerning speed vs bandwidth. Mostly due to marketing.

Bandwidth is what decides if you can support 10 files in 1 minute.

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April 15, 2009 at 12:26:01
have u experienced this thing or wat? does this practically ever happen wid our internet connection even if we have some gud plan like 2 Mbps broadband..means if u can download a file in 1 minute then practically it wd take almost 10 minutes(excluding the time we take to start the download ) to download 10 files..have u ever come across this, that u still able to download those 10 files in 1 minute whereas it was also taking 1 minute in downloading a single file of the same size?? i think m upto the conclusion point..and m not retarding ur presentations..i am only trying to map this concept into practical scenario,hope u getting me...

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April 15, 2009 at 16:11:26
abhhishekkunal we are talking concepts here.

2mb internet access is a poor example to use.

Consider instead two pcs with 10/100/1000mb nics.
xfer the same gig file at 10mb then 100 then 1000
then xfer 10 1gig files at each mb rating.

You will see a difference though small. This is a tiny example of network bandwidth.

Might want to review the differences between Token Ring and Ethernet networks to gain a better understanding of network bandwidth.

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April 15, 2009 at 23:44:30
hmmmm, i can understand it nw..but y dont the vendors provide two separate parameters?? if we really have two different things..bandwidth being the width of the tunnel (an analogy) and speed being hw fast water can run thrh y dnt they provide one measurement for speed and another for bandwidth?? however,i wd like to revert back at a point and that is..the speed is however related to the width of the tunnel..coz our hosts can pump data at any desired speed(bcoz of the network traffic we can consider the speed of disposing the data frm host as comparatively infinite), so it's the width of the tunnel which will decide at wat speed it is transferring the ultimately in this way we have only one parameter(not talking abt latency and througput, they are other issues) that can be associated with networking infrastructure..i think we are really not concerned abt hw fast a signal is propagating on the wire, we shd only care abt hw many bits we are getting in an unit time and dat leads to term nw wat m concluding that speed is wat or shd be hw fast one pulse moving on a using FDM many pulses will still move wid the same speed but the overall capacity of the wire is splitted accrdingly..coz in previous case when only one channel was using the wire was it cd receive n bits traveling at certain speed, nw by FDM some bits will correspond to a particular waveform and some will correspond to the other and hence the bandwidth is splitted..

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April 16, 2009 at 11:27:12
2 lane hwy at 55mph
10 lane hwy at 55mph

At the level we are talking about [physical layer] the 10 lane doesn't go down to 5.5 mph per lane.

Congestion/saturation is up the OSI model.

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