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I am trying to understand how the receiver decides the length of OFDM symbol in time domain before it goes into DFT process at the receiver. The complete OFDM symbol (with Cyclic Prefix added) is propagated by the transceiver through the channel and it is received at the receiver with a time delay. This delay is caused by the propagation channel due to the objects or channel characteristics. And now lets say we have received the signal and first need to know what the symbol start time so that receiver can start the OFDM symbol and cut it at the end of the symbol. Then start for the consecutive symbol...

Could anyone please explain how to visualize this?

Thanks in advance!

tuner
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1 Answers1

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First of all, the timing, phase and frequency offsets of the channel are removed. After synchronization, the cyclic prefix is removed, to avoid ISI between OFDM symbols. Now because the transmitter and receiver agree upon a common standard before the communication begins, the receiver knows how many samples to consider as a symbol.

Generally, the the number of samples in an OFDM symbol depend upon the bandwidth.

phanitej
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  • Thanks for the answer and sharing the link as well! I have looked at this and have questions below:

    1-For time synchronization, if the data-aided method is used, should the one complete OFDM symbol contain all training subcarriers and then all are correlated with the known trainings one by one at the receiver?

    2-Or the OFDM symbol contains a few training subcarriers and when they are received by the receiver each of the trainings is correlated by the known pilots?

    Thanks!

     – tuner Apr 30 '15 at 09:36
  • no you second question is true.. ofdm symbol has only a few pilots, to estimate the channel..this pilots are not used for timing synchronization – phanitej May 01 '15 at 07:39