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[Discuss-gnuradio] OFDM TX/RX with large packet_len size


From: Mohd Fadzli
Subject: [Discuss-gnuradio] OFDM TX/RX with large packet_len size
Date: Thu, 26 Mar 2015 23:50:39 +0800

Hi,

I've problem to use a large packet_len size (ie; 1500 bytes) in OFDM Flowgraph as in the digital folder examples. I got this error:

sched: <block ofdm_cyclic_prefixer (34)> is requesting more input data
  than we can provide.
  ninput_items_required = 34
  max_possible_items_available = 31
  If this is a filter, consider reducing the number of taps.


My setup is:

FFT=256
Packet_len=1512
header_mod=QPSK
payload_mod=QAM16
min output buffer in cyclic prefix=100000

Btw, if i'm using FFT=64, it does works fine when I increase the kernel shmax value. I attached the GRC that i'm using. Please kindly advice for this problem. My objective is to make this OFDM flowgraph to works with UDP/TCP packets. Or maybe there is another workaround to implement this?

Another question, is this OFDM TX/RX example is working good for QAM16? I've try this with my b200, it seems I got lots of packet lost when I'm trying to transmit a file or some random source.

Thanks

Attachment: ofdm_txrx_new_256.grc
Description: application/gnuradio-grc


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