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From: | tianji |
Subject: | [Discuss-gnuradio] Timing/preamble trigger output from the OFDM receiver |
Date: | Wed, 10 Feb 2010 13:55:09 -0600 |
User-agent: | Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.7) Gecko/20100120 Fedora/3.0.1-1.fc11 Thunderbird/3.0.1 |
Hi there,I am logging the output 1 of the ofdm_sync block (i.e., the timing triggers after the timing synchronization) and the output 1 of the ofdm_frame_aq block (i.e., the preamble triggers after both fine and coarse frequency synchronization). I saw varied gaps between adjacent values in these two streams.
For example, using the default OFDM sender/receiver parameters (pkt size=90 bytes), in one run, I got gaps in the former stream like these: 3200 3199 3200 3200 3200 3199 3200 3199 3202 3198 3201 3197 3200 3202 3200............ The gaps in the latter stream like these: 1000 1000 1000 1000 1000 1000 1000 1000 1200 1000 1000 1000 1000 1200 1000 1200......
I wonder why the gaps are not the same.Note that I modified the latter stream so that it contains zeros and ones for each 'occupied bin' rather than each 'OFDM symbol'.
Thanks Tianji
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