[Discuss-gnuradio] Re: Simultaneously transmitting on two transmitters

[jiqun qi]

On Wed, Mar 5, 2008 at 8:43 PM, Wee Shinhan <address@hidden> wrote:

def send_pkt0(self, payload0='', eof=False):

       print "Antennna 0"
       self.subdev0 = (self.u.db[0][0])
       self.subdev0.set_enable(bool(1)

self.subdev0.set_gain(self.subdev0.gain_range()[1])

       self.packet_transmitter.send_pkt(payload0, eof)
       return True

def send_pkt1(self, payload1='', eof=False):

       print "Antennna 1"
       self.subdev1 = (self.u.db[1][0])
       self.subdev1.set_enable(bool(1)

self.subdev1.set_gain(self.subdev0.gain_range()[1])

       self.packet_transmitter.send_pkt(payload1, eof)
       return True

So i forced payload0 to be sent by antenna0 and
payload1 to be sent by antenna1. Then in
benchmark_tx.py i used the following codes to send the
data:

               send_pkt0(payload)
               send_pkt1(payload1)

In principle, in USRP, if these two transmit daughter boards share "one common clock", it could not achieve the "strict-sense simultaneously transmitting" because your program is executed in "sequence", not "parallel". However, you can "first" transmit the symbol s1 on antenna 1, "then" transmit s2 on antenna 2 "almost simultaneously" from the view point of well programming.

For example,  you can send symbols s1 and s2 to the transmit buffer first, then enable the two antennas for transmitting, so the transmit time  cycle difference \delta_t will be smaller than the way that you send symbol s1 to the antenna 1, and enable it for transmitting, then do the symbol s2, because there is the time cycle consumption that you send symbol s2 to the transmit buffer.

I am not sure how actually it would be in practice. And I will try my best to do it in the following days.