Katy Qian wrote:
Hi,For the majority of my tests (ex. below), with benchmark_ofdm_*, the receiver terminates prematurely with: ... ok: True pktno: 7501 n_rcvd: 4537 n_right: 4263 ok: True pktno: 7502 n_rcvd: 4538 n_right: 4264 ok: True pktno: 7503 n_rcvd: 4539 n_right: 4265 Exception in thread Thread-1: Traceback (most recent call last): File "/usr/local/lib/python2.4/site-packages/gnuradio/gr/gr_threading_24.py", line 446, in __bootstrap self.run() File "/usr/local/lib/python2.4/site-packages/gnuradio/blks2impl/ofdm.py", line 294, in run self.callback(ok, payload) File "./benchmark_ofdm_rx.py", line 168, in rx_callback (pktno,) = struct.unpack('!H', payload[0:2]) error: unpack str size does not match format uOuOuOuOuOuO ... It seems a certain combination of fftlength, occupied tones, and cp length allows the program to run to completion (FFT/OT/CP = 64/28/54 and 40/20/32 works but 256/160/128 ends early). Does anyone know the "magic" behind these sets of values, or can explain something I have overlooked?
This is an error that occurs when the packet is corrupted in a way that ends up with an empty payload, usually due to a bad value for the packet length in the header.
Also, is there a way to control / define exactly which subcarriers are being used to transmit the data?
No. You have to hack the C++ code in gr_ofdm_mapper. Others have been looking to do the same thing, but I'm not sure how far they have gotten.
Any help is appreciated, thank you in advance. Katy
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