In OFDM Transmitter, when you do the IFFT of input samples x(0),x(1),x(2)....x(N-1), then at the output of the IFFT block you get a sequence X[0],X[1],....X[N-1]. My question is, that do we then transmit X[0],X[1],....X[N-1] one by one over the channel (and hence the need for parallel to serial blockafter IFF block)? If that is so, don't you think we only need to transmit only one element from the set {X[0],X[1],....X[N-1] } ??? because if you consider, lets say, X[0] then this particular element has information about all the samples of x(0),x(1),x(2)....x(N-1) (according to the formula of DFT) and we need only send only this element and not the complete set {X[0],X[1],....X[N-1] }? _____________________________ Posted through www.DSPRelated.com

# In OFDM, do we need to send all the outputs of the IFFt block?

Started by ●January 7, 2014

Reply by ●January 7, 20142014-01-07

On Tuesday, January 7, 2014 9:19:59 AM UTC-5, engrMunna wrote:> If that is so, don't you think we only need to transmit only one element > from the set {X[0],X[1],....X[N-1] } ??? because if you consider, lets say, > X[0] then this particular element has information about all the samples of > x(0),x(1),x(2)....x(N-1) (according to the formula of DFT) and we need only > send only this element and not the complete set {X[0],X[1],....X[N-1] }? >You're wrong. X[0] is a function of all the elements x[0...N-1], but in the general case you cannot recover all of x[0...N-1] just from X[0]. If c=a+b, can you compute both a and b just from observing c?

Reply by ●January 7, 20142014-01-07

On Tue, 7 Jan 2014 07:01:41 -0800 (PST), julius <juliusk@gmail.com> wrote:>On Tuesday, January 7, 2014 9:19:59 AM UTC-5, engrMunna wrote: >> If that is so, don't you think we only need to transmit only one element >> from the set {X[0],X[1],....X[N-1] } ??? because if you consider, lets say, >> X[0] then this particular element has information about all the samples of >> x(0),x(1),x(2)....x(N-1) (according to the formula of DFT) and we need only >> send only this element and not the complete set {X[0],X[1],....X[N-1] }? >> > >You're wrong. X[0] is a function of all the elements x[0...N-1], but in the general case you cannot recover all of x[0...N-1] just from X[0]. > >If c=a+b, can you compute both a and b just from observing c?It'd be a very popular compression scheme if it worked. ;) Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com

Reply by ●January 7, 20142014-01-07

On Tuesday, January 7, 2014 1:01:01 PM UTC-5, Eric Jacobsen wrote:> On Tue, 7 Jan 2014 07:01:41 -0800 (PST), julius <juliusk@gmail.com> > > wrote: > > > > >On Tuesday, January 7, 2014 9:19:59 AM UTC-5, engrMunna wrote: > > >> If that is so, don't you think we only need to transmit only one element > > >> from the set {X[0],X[1],....X[N-1] } ??? because if you consider, lets say, > > >> X[0] then this particular element has information about all the samples of > > >> x(0),x(1),x(2)....x(N-1) (according to the formula of DFT) and we need only > > >> send only this element and not the complete set {X[0],X[1],....X[N-1] }? > > >> > > > > > >You're wrong. X[0] is a function of all the elements x[0...N-1], but in the general case you cannot recover all of x[0...N-1] just from X[0]. > > > > > >If c=a+b, can you compute both a and b just from observing c? > > > > It'd be a very popular compression scheme if it worked. ;) > > > > > > Eric Jacobsen > > Anchor Hill Communications > > http://www.anchorhill.comDon't give them any ideas, now ... !

Reply by ●January 7, 20142014-01-07

On 1/7/14 1:03 PM, julius wrote:> On Tuesday, January 7, 2014 1:01:01 PM UTC-5, Eric Jacobsen wrote: >> On Tue, 7 Jan 2014 07:01:41 -0800 (PST), julius<juliusk@gmail.com> >> wrote:>> >>> If c=a+b, can you compute both a and b just from observing c? >> >> It'd be a very popular compression scheme if it worked. ;) >> > > Don't give them any ideas, now ... !remember that Zeosync farce from around 2000? -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."

Reply by ●January 7, 20142014-01-07