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Re: [Discuss-gnuradio] precise transmit scheduling

From: Steven Clark
Subject: Re: [Discuss-gnuradio] precise transmit scheduling
Date: Thu, 4 Nov 2010 18:11:07 -0400

On Thu, Nov 4, 2010 at 5:33 PM, Yan Nie <address@hidden> wrote:
Dear all,

I am developing a transmitter on USRP1 with LFTX daughterboard. This transmitter sends a BPSK modulated Barker code sequence up-converting to a frequency ranging from 1MHz to 20MHz. I implemented the transmission of the whole sequence in one fixed frequency in the requried range on one USRP1 board and receiving on the other USRP1 board.

My question is :

How can I scheduling the transmitter by sending several bits of the sequence a time and the delays between each time transmitting are 1ms?

How can the RF frequency be linearly hopping from 1MHz to 20MHz by secheduling?

I've seen that m-blocks appears partially motivated by precise scheduling of transmission. Is the m-block implements is suitable for this scheduling?  If so, could anyone give me any suggestion on how can it implement the scheduling for my project? Tons of thanks in advance! I really need your help with this scheduling.


I am also very interested in this. I have had some success by using gr.message_source, and having a python thread that periodically pushes new data into the system by putting it on the message queue. Transmitter auto_tr is enabled so that when the usrp runs out of data it turns off the transmit until the next message arrives. Scheduling at the python level seems very rough, with intervals varying ~+/- 1ms without tuning each time, and ~+/- 10ms when tuning before each burst. I was under the impression that calling set_rx_freq() to tune just the DUC rather than usrp.tune() should be faster/more responsive, but I haven't seen this to be true...

Any scheduling / hopping tips would be greatly appreciated!


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