802.15.4 transmitted signal structure

Hello GR,

Is there any one who has monitored the signal generated by
transceiver.py
related to the 802.15.4 implementation. I want to understand the meaning
its
structure.

I find out that it consist of a bursty transmission of a signal compound
of
11 to 12 msec of wide-band signal followed by a narrower 400 Khz signal
that
lasts around 10 msec and is 20 db stronger then the wide-band signal.

  • Another unrelated point: I need to decrease at minimum the signal
    transmitted, if I choose the gain at transmission at 0 dB. Is there a
    way to
    even go beyond that:
    Does it make sense to have the “blocks.multiply_vcc” in the
    transceiver.py
    flowgraph values between 0 and 1 ? or that have nothing to do with
    decreasing the magnitude of the signal transmitted ?

Regards,
Ruecan


View this message in context:
http://gnuradio.4.n7.nabble.com/802-15-4-transmitted-signal-structure-tp47199.html
Sent from the GnuRadio mailing list archive at Nabble.com.

I find out that it consist of a bursty transmission of a signal compound of
11 to 12 msec of wide-band signal followed by a narrower 400 Khz signal that
lasts around 10 msec and is 20 db stronger then the wide-band signal.

The wideband signal is the packet. Actually, it should be terminated
with a tx_eob tag. Do you see any Us on you console? AFAIK, if the
packet does not end with an tx_eob tag you might see the oscillator as
narrow band signal.

  • Another unrelated point: I need to decrease at minimum the signal
    transmitted, if I choose the gain at transmission at 0 dB. Is there a way to
    even go beyond that:
    Does it make sense to have the “blocks.multiply_vcc” in the transceiver.py
    flowgraph values between 0 and 1 ?

Yes, that works.

Bastian

Hi Bastian,

Bastian B.-2 wrote

The wideband signal is the packet. Actually, it should be terminated with
a tx_eob tag. Do you see any ‘U’s on you console? AFAIK, if the packet
does not end with an tx_eob tag you might see the oscillator as narrow
band signal.

Yes I see 'U’s on the console. However I am not sure that the
implementation
contain such element (tx_eob).
I’ve checked the mac.cc code but did not found something referring to a
tag
or end of burst.

May be that’s why I may see that narrow band signal. If may
understanding is
correct that should be fixed right and I should add such tag in the
packet
structure.

Bastian B.-2 wrote

Does it make sense to have the “blocks.multiply_vcc” in the
transceiver.py
flowgraph values between 0 and 1 ?

Yes, that works.

But If for example I try to use 0.5 as value (blocks.multiply_vcc(0.5))
I
got this error:
TypeError: in method ‘multiply_cc_make’, argument 1 of type ‘size_t’

Ruecan


View this message in context:
http://gnuradio.4.n7.nabble.com/802-15-4-transmitted-signal-structure-tp47199p47223.html
Sent from the GnuRadio mailing list archive at Nabble.com.

May be that’s why I may see that narrow band signal. If may understanding is
correct that should be fixed right and I should add such tag in the packet
structure.

You have to open the PHY block. The pdu_to_tagged_stream block inserts a
pdu_length tag. Later the burst_tagger block inserts tx_sob and tx_eob
tags based on the pdu_length tag. You can use the tag_debug block to see
where things go wrong. Also check the tag names in the blocks parameter.

But If for example I try to use 0.5 as value (blocks.multiply_vcc(0.5)) I
got this error:
TypeError: in method ‘multiply_cc_make’, argument 1 of type ‘size_t’

I think you want something like
blocks.multiply_const_vcc((.5,))

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