[Discuss-gnuradio] is this normal behavior of benchmark_rx.py

[Sahoo, Anirudha]

Hi,

I have two USRPs (N210) connected to each other through a channel

emulator (via RF cable) which is emulating a lossless channel.

When I run the benchmark_rx.py I see some

spurious bytes being received by the receiver even when the sender

application (benchmark_tx.py) has not been started. I have enabled

VERBOSE in the file “digital_ofdm_frame_sink.cc”. Below is a sample output from the receiver

(note the sender has not been started at all).  I see that intermittently

the cc layer prints out the following block which means it got some

bytes (symbols). How can receiver get these bytes when there is no sender?

What is more bothersome is that when I change the occupied-tones

to 120 (i.e., I run it with “python benchmark_rx.py --args "addr=usrp4" -f 795.5M --occ 120 -W 4M”),

(in this case “bytes from demapper = 14” printed instead of 29)

then the following block is printed *continuously*. I am wondering where is the

receiver getting bytes/symbols when there is no transmitter? I am running

gnuradio 3.6.2.

 

==================

@ enter_have_sync

Header Search bitcnt=0, header=0x00000000 bytes from demapper = 29

got header: 0xb06fe351

@ enter_search

 

 

$ python benchmark_rx.py --args "addr=usrp4" -f 795.5M --occ 240 -W 4M

linux; GNU C++ version 4.4.6 20120305 (Red Hat 4.4.6-4); Boost_104100; UHD_003.004.003-221-g9d6f9492

 

-- Opening a USRP2/N-Series device...

-- Current recv frame size: 1472 bytes

-- Current send frame size: 1472 bytes

 

UHD Warning:

    Unable to set the thread priority. Performance may be negatively affected.

    Please see the general application notes in the manual for instructions.

    EnvironmentError: OSError: error in pthread_setschedparam

 

No gain specified.

Setting gain to 19.000000 (from [0.000000, 38.000000])

Using Volk machine: avx_64_mmx

>>> gr_fir_ccf: using SSE

>>> gr_fir_fff: using SSE

@ enter_search

Warning: failed to enable realtime scheduling

@ enter_have_sync

Header Search bitcnt=0, header=0x00000000 bytes from demapper = 29

got header: 0x50b5f4e3

@ enter_search

@ enter_have_sync

Header Search bitcnt=0, header=0x00000000 bytes from demapper = 29

got header: 0x10ffc9c1

@ enter_search

TIMEOUT

@ enter_have_sync

Header Search bitcnt=0, header=0x00000000 bytes from demapper = 29

got header: 0xb06fe351

@ enter_search

TIMEOUT

 

thanks and regards

 

--Anirudh Sahoo

Advanced Network Technology Div.

National Institute of Standards and Technology (NIST)

100 Bureau Drive,

Gaithersburg, MD - 20878

Room – B230, bldg.- 222

Phone- 301-975-4439