Re: [Discuss-gnuradio] benchmark_tx and rx : too many FALSE packet

[West, Nathan]

There's been some subtle miscues in this thread. Let's start over from the fundamentals.

First, think about what the flowgraph is. You must understand the transmit and receive chains to do meaningful work with GNU Radio flowgraphs.

This is a rather old example of sending packetized data that doesn't use error correction. There is a function that checks the CRC of packets. If a single bit is wrong the packet fails. (As a side note building packetized/bursty modems in the way these flowgraphs work is NOT recommended).

Given this information, for the same SNR and channel what would you expect to happen to bit error rates (and therefor packet error rates) as you change modulations from GMSK, BPSK, etc to QAM?

Finally, as I mentioned these flowgraphs are sort of deprecated. Maybe you can tell us what you're really going for and someone can suggest a better tool.

Cheers,

Nathan

On Sun, Mar 13, 2016 at 4:22 AM, SangHyuk Kim <address@hidden> wrote:

Hi all.

I'm using benchmark_tx(rx).py example

I experimented variety modulation schemes and GMSK, BPSK, QPSK modulation worked well

However, when I used QAM modulation, most of received packet were corrupted (FALSE)

ENV)

both TX and RX uses USRP N210 with ANT500 and CBX 40MHz

distance between TX and RX is shorter than 3m

TX)

./benchmark_tx.py -f 1.5G -m qam -S 8 --tx-gain=30

RX)

./benchmark_rx.py -f 1.5G -m qam -S 8

RESULTS ON RX)

ok = FALSE  pktno = 1  n_rcvd = 1  n_right = 0
ok = FALSE  pktno = 2  n_rcvd = 2  n_right = 0
ok = FALSE  pktno = 3  n_rcvd = 3  n_right = 0
...

ok = TRUE  pktno = N  n_rcvd = N  n_right = 1
...

Is this normal case of qam modulation ?

How can I get more TRUE packet using QAM modulation ?

Thanks.

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