From: Johnathan Corgan <address@hidden>
To: Bill Stevenson <address@hidden>
Cc: address@hidden
Sent: Wednesday, December 3, 2008 2:57:55 PM
Subject: Re: [Discuss-gnuradio] a report on dqpsk modulation in gnuradio
On Mon, Dec 1, 2008 at 1:07 PM, Bill Stevenson
<
address@hidden> wrote:
> python
benchmark_tx.py -f 2479M -r 2000k -m dqpsk -s 100 (-s 800 or -s 1500)
> python
benchmark_rx.py -f 2479M -r 2000k -m dqpsk
What is the CPU type and speed you are using? In my experience, data
rates above about 500 kbps are difficult to receive on a typical
laptop platform due to lack of sufficient CPU cycles. On an Intel
Core2 Duo at 2.1 GHz (IBM Thinkpad T60), I can't go above 800 kbps.
Your rate of 2 Mbps is likely much too high. Are you seeing any "uO"
on your output?
-Johnathan
Thank you, Johnathan! I did my experimentation again with different configuration. Below are the arguments I used for my experimentation:
-r 400k -s 1500: 50% of the transmitted packets are received, but 0 right. The received packet number increased continuously.
-r 400k -s 500: 66% of the transmitted packets are received, but 0 right. The received packet number increased continuously.
-r 400k -s 300: 71% of the transmitted packets are received, but 0 right. The received packet number increased continuously.
-r 400k -s 200: 93.6% of the transmitted packets are received, but 0 right. The received packet number increased irregularly.
One USRP is controlled by my laptop (Compaq Presario C700, 1.46GHz Dual-Core Pentium, 1GB RAM), which is used for Tx and another USRP is handled by a desktop (Gateway, 2.40GHz, Core 2 Dual, 2GB RAM), which is used for Rx. The two USRP are 3m apart from each other. The reason why we used 2Mbps for dqpsk case was that when the bit rate is up to 2Mbps, the PER ratio could somehow reach its 'minimum value', and there is no uO sign on my desktop PC, but there was one or two uU signs on my laptop part when s is set to 100. I really cannot figure out why I cannot get dqpsk scheme done when you have successfully verified it works fine in your configuration. I am totally confused, is there anything wrong with my setup described above, Johnathan? I really need guidance. Thank you!!!
Bill