OFDM Cyclic Prefixer: Difference between revisions

Latest revision as of 13:26, 23 November 2022

Adds a cyclic prefix and performs pulse shaping on OFDM symbols.

Input: OFDM symbols (in the time domain, i.e. after the IFFT). Optionally, entire frames can be processed. In this case, Length Tag Key must be specified which holds the key of the tag that denotes how many OFDM symbols are in a frame.

Output: A stream of (scalar) complex symbols, which include the cyclic prefix and the pulse shaping.; Note: If complete frames are processed, and Rolloff is greater than zero, the final OFDM symbol is followed by the delay line of the pulse shaping.

The pulse shape is a raised cosine in the time domain.

Rolloff: Length of the rolloff flank (in samples). That parameter can sometimes be found described as a percentage of the FFT Length, so that would be Rolloff (%) = (Rolloff (samples)/ FFT_len) * 100.; An explanation of this parameter can be found here

This flowgraph can be found at [1].

@@ Line 18: / Line 18: @@
 ; Rolloff
-: Length of the rolloff flank in samples
+: Length of the rolloff flank (in samples). That parameter can sometimes be found described as a percentage of the FFT Length, so that would be Rolloff (%) = (Rolloff (samples)/ FFT_len) * 100.
+: An explanation of this parameter can be found [https://rfmw.em.keysight.com/wireless/helpfiles/n7615b/Content/Main/ofdm_cosine_windowing.htm here]
 ; Length Tag Key
@@ Line 25: / Line 26: @@
 == Example Flowgraph ==
-Insert description of flowgraph here, then show a screenshot of the flowgraph and the output if there is an interesting GUI.  Currently we have no standard method of uploading the actual flowgraph to the wiki or git repo, unfortunately.  The plan is to have an example flowgraph showing how the block might be used, for every block, and the flowgraphs will live in the git repo.
+This flowgraph can be found at [https://github.com/gnuradio/gnuradio/blob/master/gr-digital/examples/ofdm/tx_ofdm.grc].
+[[File:Tx_ofdm_fg.png|800px]]
 == Source Files ==