[Discuss-gnuradio] About packetized MIMO Tx/Rx,

[Sungro Yoon]

Hello,

I am currently trying to implement 2x2 MIMO packet transmission and
having difficulties.. I need help and any comment will be really
useful..


My main references are benchmark_tx.py and fm_tx_2_daughterboards.py.

As I cannot directly connect signal sources to gr.interleave() unlike
in fm_tx_2_daughterboards.py (sending data is put into queue of
message_source only when send_pkt(payload) is called), what I have
done is as follows.

* I created multi_mod_pkts class that is similar to mod_pkts. Here I
created two separate message_source (_pkt_input1 and _pkt_input2).

* I connected those two message_sources into interleaver and then
self, using following code

        self._pkt_input1 = gr.message_source(gr.sizeof_char, msgq_limit)
        self._pkt_input2 = gr.message_source(gr.sizeof_char, msgq_limit)

        intl = gr.interleave(gr.sizeof_char)

        self.connect(self._pkt_input1, (intl, 0))
        self.connect(self._pkt_input2, (intl, 1))

        self.connect(intl, self._modulator, self)

* Whenever send_pkt(payload1, payload2) is called, those messages are
put into msg queue of message_source. respectively.

* In the main program, I created usrp_sink_c object and set mux using
following code

        self._u = usrp.sink_c (which=self._which,
                                nchan=2,
                                fusb_block_size=self._fusb_block_size,
                                fusb_nblocks=self._fusb_nblocks)

        self._subdev = (self._u.db(0, 0), self._u.db(1, 0))
        self._u.set_mux(0xba98)

        self._subdev[0].set_gain(self._subdev[0].gain_range()[1])   #
set max Tx gain
        self._subdev[1].set_gain(self._subdev[1].gain_range()[1])   #
set max Tx gain

        self.set_freq(0, freq0)
        self.set_freq(1, freq1)

        self._subdev[0].set_enable(True)             # enable
transmitter
        self._subdev[1].set_enable(True)             # enable
transmitter

        self._dxc = self._which

       self.connect(self, self._u)


That's all. But the receiver does not sense any incoming traffic. What
could be done to make it work?

Thank you in advance!

Sungro