Theories behind OFDM synchronization

[Antonio_Magma]

synchronization in ofdm

Can anyone of u recommend me any resources regarding synchronization in OFDM? I'm building an OFDM power line modem.

Books, papers, anything that can teach me the concept (preferably with less maths). Thx alot!

 

[Gandharva]

channel estimation in ofdm

"ML Estimation of Timing and Frequency Offset in Multicarrier Systems"

this paper deals with OFDM symbol synch and Freq Offset estimation. power line channels dont introduce Frequency offsets , this can be neglected, but, OFDM symbol synchronization cant be neglected, this has to be done.

"Timing Recovery for OFDM Transmission"

this paper gives a overview of all the types of errors and the methods of correcting them.

hope this should help you.

 

[Antonio_Magma]

ofdm and synchronization

Hi Gandharva

power line channels dont introduce Frequency offsets , this can be neglected..

Why so? To inject the baseband signal into the power line channel you do have to upsample it to the carrier frequency right? wouldnt that mean there will be variations between the Tx and Rx oscillating frequency?

 

[Gandharva]

ofdm synchronization with verilog

Frequency offset erros in OFDM occurs because of two reasons,

1) Tx - Rx oscillator mismatch
2) doppler frequency shift

doppler shift is a more predominant factor than oscillator mismatch. as this is not present in a wired system we can neglect the 1st factor.

still to be safe from freq offset errors, we can confine ourselves to small ofdm symbol duration. you can refer to the second paper which i have uploaded, it discusses these things in more detail.

 

[Antonio_Magma]

ofdm+on line+books

Ah, that's 1 less thing to worry then

Thx man...

 

[canthackit]

ofdm synchronization

Fair amount of work is done in this area... especially in Wireless.. that is where it is called OFDm....

on wireline ofcourse it is DMT... but people are saying OFDm for power line...


The WLAN products use pilots/training/preamble for synchronization.... so most of the popular algorithms are of this type... by the way check out Schmidl and Cox also on this one...

There are advanced stuff using semiblind, blind, iterative, etc... which probably do not buy u much ...

Now on power line.... u can use preamble based if u r doing packed based comm. and adapt these popular algorithms to your case....

one more thing is channel static or not.... and take this into account in yout choice.

all the best

Added after 22 minutes:

want to add bit more.....

synchro. in ofdm is lot different.... in the sense it is more of an estimation problem..... open loop that too.... u may find closed loop for tracking phase....


open loop because quick nature of packet comm. and rx sleeping... power coservation of handhelds etc.... if these assumptions are different for power line.. u may be looking at different suite of algorithms altogether...

and synch. ofdm is group of algorithms...

thanks

 

[Antonio_Magma]

doppler oscillator ofdm

Is there any books u all would recommend on OFDM synchronization, channel estimation etc?

And another thing, there are quite a few types of synchronization methods for OFDM. For you guys who have experience implementing OFDM what method would have better low complexity vs performance tradeoff?

 

[hariharan4000]

how to implement ofdm

hi
visit www.vlsibank.com. i saw a paper by WIPRO technologies on OFDM implementation
I think it will be useful for u.
regards
haran

 

[Antonio_Magma]

ofdm synchronization book

thx for d link hariharan..

but i've alredy got that paper. Besides it uses VLSI, i have to use DSP but thx anyway

 

[mnosrati]

ofdm synchronization verilog code

you must read this book
"OFDM for wireless multimedai communications "
by rechard van nee

 

[hariharan4000]

hi
u can use DFT algorithms ,which includes all DSP concepts to implement ofdm.i did my same prject in my M.tech. i used verilog for coding.
DFT is the suitable one.do u know how to implement vetrbi decoder ?

 

[Antonio_Magma]

DFT algorithms? U mean discrete fourier transform?

I'm using IFFT/FFT to produce my ofdm symbols...

the only viterbi i'm using is the 1 in Simulink which later will be directly converted into the DSP

 

[alameer]

can any one upload these files on megaupload plz..

i need it too

 

[shockie]

I think you can find some Verilog or VHDL example of Viterbi decoder on ipcore website.

 

[rostam63]

this file cotains good information aout ofdm.