# Benchmark\_rx is not receiving any packet for 8PSK modulation

**URL:** <https://www.ruby-forum.com/t/benchmark-rx-is-not-receiving-any-packet-for-8psk-modulation/212996>\
**Category:** GNU Radio\
**Created:** [October 20, 2011, 8:42am UTC](https://www.ruby-forum.com/t/benchmark-rx-is-not-receiving-any-packet-for-8psk-modulation/212996 "2011-10-20T08:42:43Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\
**Post date:** [October 20, 2011, 8:42am UTC](https://www.ruby-forum.com/t/benchmark-rx-is-not-receiving-any-packet-for-8psk-modulation/212996/1 "2011-10-20T08:42:43Z")

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Hello,

I am working on the effect of adaptive modulation in packet loss. I am  
running my codes in USRP2 with XCVR2450 daughter-board and I am using  
UHD\_003\_001\_002 image. I am using benchmark\_tx and benchmark\_rx codes in  
the  
gnuradio-examples/python/digital folder to find packet loss for  
different  
modulation schemes.

Now, when I run my the benchmark codes with dbpsk and dqpsk modulation,  
the  
receiver receives packets. However, when I run the codes with d8psk  
modulation scheme, the receiver just sits idle waiting for the packets  
but  
does not receive anything. Let’s say I am giving the following commands  
in  
the benchmark programs:

./benchmark\_tx.py -f 2.4G -r 1M -e eth2 -m d8psk --tx-ampl 0.95 (I am  
using  
a very high transmitter power)

./benchmark\_rx.py -f 2.4G -r 1M -e eth2 -m d8psk

I am getting the following packet reception ratios for different  
modulation  
schemes:

dbpsk: 99% dqpsk: 92% d8psk: 0% !!

I expected to get less packets (higher packet loss) through d8psk  
modulation  
since it is transmitting at a higher data rate. But the receiver is not  
receiving anything at all !! Does it mean that the channel between the  
transmitter and the receiver is simply not good enough to transmit 3 bit  
per  
second per Hz? In other words, am I exceeding Shannon’s capacity here?

Thanks,

Nazmul

–  
Muhammad Nazmul I.

Graduate Student  
Electrical & Computer Engineering  
Wireless Information & Networking Laboratory  
Rutgers, USA.

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**Author:** ![Nazmul\_I](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/e495f1/32.png) [@Nazmul\_I](https://www.ruby-forum.com/u/Nazmul_I)\
**Post date:** [October 24, 2011, 11:21am UTC](https://www.ruby-forum.com/t/benchmark-rx-is-not-receiving-any-packet-for-8psk-modulation/212996/2 "2011-10-24T11:21:57Z")

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I have similar problem. My stats look on par with yours for dbpsk and  
dqpsk.

I have a USRP1, Flex900, DBS-RX and using  
./benchmark\_tx.py -f 900e6 -m d8psk --tx-gain 3000 (\<-- diff from ampl  
.95)  
I get high BER output at the Rx side.  
The Rx side detects numerous packets, but none of which are correct.

Jerry