OFDM is used for WiFi, HomePlug, and HD radio. How much data rate increase do you get by using the multiple carriers, as opposed to just one carrier? For example, HomePlug 1.0 goes upto 20Mhz in carriers. How much benefit do you get by using its 84 carriers, as opposed to just using one 20Mhz carrier at the highest data rate you can make work? WiFi is 2.4Ghz. Same type of question? Should wired digital audio and video networks also use OFDM? ************** Come Join: http://groups.google.com/group/realtime_signal_and_control
OFDM for wired?
Started by ●February 9, 2007
Reply by ●February 9, 20072007-02-09
frank.agee@gmail.com wrote:> OFDM is used for WiFi, HomePlug, and HD radio.OFDM is a technical trick. It allows for the cheap and simple demodulator. There are no fundamental advantages.> How much data rate increase do you get by using the multiple > carriers, > as opposed to just one carrier?None.> > For example, HomePlug 1.0 goes upto 20Mhz in carriers. How much > benefit do you get by using its 84 carriers, as opposed to just using > one 20Mhz carrier at the highest data rate you can make work?None.> > WiFi is 2.4Ghz. Same type of question?None.> > Should wired digital audio and video networks also use OFDM?No connection.> ************** Come Join: > http://groups.google.com/group/realtime_signal_and_controlWhat for? Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Reply by ●February 10, 20072007-02-10
DSL MODEMS ARE BASED ON OFDM RIGHT OR FOR THAT MATTER ADSL OR VDSL OR NEWER VERSIONS USE THEY PROVIDE NEARLY 25 MBPS OF DATA AND REMEMBER THEY USE QAM-(2^16)----->PROPRIETARY TECHNOLOGIES ARE THERE WITH CERTAIN COMPANIES. particlereddy On Feb 9, 3:14 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com> wrote:> frank.a...@gmail.com wrote: > > OFDM is used for WiFi, HomePlug, and HD radio. > > OFDM is a technical trick. It allows for the cheap and simple > demodulator. There are no fundamental advantages. > > > How much data rate increase do you get by using the multiple > > carriers, > > as opposed to just one carrier? > > None. > > > > > For example, HomePlug 1.0 goes upto 20Mhz in carriers. How much > > benefit do you get by using its 84 carriers, as opposed to just using > > one 20Mhz carrier at the highest data rate you can make work? > > None. > > > > > WiFi is 2.4Ghz. Same type of question? > > None. > > > > > Should wired digital audio and video networks also use OFDM? > > No connection. > > > ************** Come Join: > >http://groups.google.com/group/realtime_signal_and_control > > What for? > > Vladimir Vassilevsky > > DSP and Mixed Signal Design Consultant > > http://www.abvolt.com
Reply by ●February 10, 20072007-02-10
"frank.agee@gmail.com" <frank.agee@gmail.com> wrote:>How much data rate increase do you get by using the multiple >carriers, >as opposed to just one carrier?You can not beat physical limitations, OFDM is just a modulation scheme, making data transfer over difficult propagation media more robust against multipath and frequency dependent influences over the occupied bandwidth.
Reply by ●February 10, 20072007-02-10
"PARTICLEREDDY (STRAYDOG)" <particlereddy@gmail.com> wrote:>DSL MODEMS ARE BASED ON OFDM RIGHT >OR FOR THAT MATTER ADSL OR VDSL OR NEWER VERSIONS USE >THEY PROVIDE NEARLY 25 MBPS OF DATAAnd guess what bandwidth and symbol rate they use. They can not overcome the physical limitations, they just use OFDM because it is relatively easy made adaptive, to use the part of the spectrum that gives best performance.
Reply by ●February 10, 20072007-02-10
PARTICLEREDDY (STRAYDOG) wrote:> DSL MODEMS ARE BASED ON OFDM RIGHTNot quite. The DSL modems are based on DMT.> OR FOR THAT MATTER ADSL OR VDSL OR NEWER VERSIONS USE > THEY PROVIDE NEARLY 25 MBPS OF DATA > AND REMEMBER THEY USE QAM-(2^16)----->PROPRIETARY TECHNOLOGIES ARE > THERE WITH CERTAIN COMPANIES.So what? Why are you screaming? Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com> > On Feb 9, 3:14 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com> > wrote: > >>frank.a...@gmail.com wrote: >> >>>OFDM is used for WiFi, HomePlug, and HD radio. >> >>OFDM is a technical trick. It allows for the cheap and simple >>demodulator. There are no fundamental advantages. >> >> >>>How much data rate increase do you get by using the multiple >>>carriers, >>>as opposed to just one carrier? >> >>None. >> >> >> >> >>>For example, HomePlug 1.0 goes upto 20Mhz in carriers. How much >>>benefit do you get by using its 84 carriers, as opposed to just using >>>one 20Mhz carrier at the highest data rate you can make work? >> >>None. >> >> >> >> >>>WiFi is 2.4Ghz. Same type of question? >> >>None. >> >> >> >> >>>Should wired digital audio and video networks also use OFDM? >> >>No connection. >> >> >>>************** Come Join: >>>http://groups.google.com/group/realtime_signal_and_control >> >>What for? >> >>Vladimir Vassilevsky >> >>DSP and Mixed Signal Design Consultant >> >>http://www.abvolt.com > > >
Reply by ●February 10, 20072007-02-10
On Sat, 10 Feb 2007 15:37:39 GMT, Vladimir Vassilevsky <antispam_bogus@hotmail.com> wrote:> > >PARTICLEREDDY (STRAYDOG) wrote: >> DSL MODEMS ARE BASED ON OFDM RIGHT > >Not quite. The DSL modems are based on DMT.So what's the difference between OFDM and DMT? Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org
Reply by ●February 10, 20072007-02-10
Eric Jacobsen wrote:> So what's the difference between OFDM and DMT?DMT is a wider notion then OFDM. DMT carriers are not necessarily orthogonal, and they can use the different modulation and the different power level for every carrier. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Reply by ●February 10, 20072007-02-10
hi all,
for all other related issues you raised..please check up with
centillium communications DSL modems..and their documents and
specifications sheet and for that matter cioffi's papers.
particlereddy
On Feb 10, 12:11 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com>
wrote:
> Eric Jacobsen wrote:
> > So what's the difference between OFDM and DMT?
>
> DMT is a wider notion then OFDM. DMT carriers are not necessarily
> orthogonal, and they can use the different modulation and the different
> power level for every carrier.
>
> Vladimir Vassilevsky
>
> DSP and Mixed Signal Design Consultant
>
> http://www.abvolt.com
Reply by ●February 11, 20072007-02-11
On Sat, 10 Feb 2007 20:11:51 GMT, Vladimir Vassilevsky <antispam_bogus@hotmail.com> wrote:>Eric Jacobsen wrote: > >> So what's the difference between OFDM and DMT? > >DMT is a wider notion then OFDM. DMT carriers are not necessarily >orthogonal, and they can use the different modulation and the different >power level for every carrier.I think that's the first time I've heard someone assert that DMT tones can be non-orthogonal, but OFDM can have a different modulation and power level on each subcarrier as well. Anyway, in the DSL spec the "DMT" subcarriers are still orthogonal. I asked because I've never really seen anyone explain a difference in the two other than the name. Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org
