Re: [Discuss-gnuradio] Transmit time synchronization

[Muhammad Shahmeer Omar]

thanks for the input Jeff. I am fairly new to GNURadio so any suggestions on how i can create the said network. My main goal is to implement the multiple relay network and demonstrate its advantages. As i understand it, a differential modulation scheme is my only option if i want to achieve diversity gain on rx without having to estimate the channel. Any suggestions on how i go about doing this?

On Mon, Oct 13, 2014 at 7:05 PM, Jeff Long <address@hidden> wrote:

On 10/13/2014 08:57 AM, Muhammad Shahmeer Omar wrote:

sorry disregard previous mail

I am trying to implement a multi-relay cooperative network using
gnuradio and USRP B200. I cannot figure out how to synchronize the relay
transmissions using GNU-Radio (without editing FPGA code or using
external clock source).

I created an out of tree module derived from the tags_demo example of
uhd but i encounter a problem with the packet encoder.

my flow graph is something like

USRP source ---> tagging_block ---> DBPSK demod -->packet decoder -->
encoder --> mod --> USRP sink.

when i attach tag debug block, i see that the packet decoder is not
propogating my tags. Are their any substitutes to the encoder or is

The packet_decoder block has a message queue in the middle of its implementation, so tags are not propagated. Not sure how to get around this.

there any problem with my code which is attached. Any help would be very
welcome. Thanks!



On Mon, Oct 13, 2014 at 5:53 AM, Muhammad Shahmeer Omar
<address@hidden <mailto:address@hiddenpk>> wrote:

    Hello all,

    I am trying to implement a multi-relay cooperative network using
    gnuradio and USRP B200. I cannot figure out how to synchronize the
    relay transmissions using GNU-Radio (without editing FPGA code or
    using external clock source).

    I created an out of tree module derived from the tags_demo example
    of uhd but i encounter a problem with the packet encoder.

    my flow graph is something like

    USRP source ---> tagging_block ---> DBPSK demod -->packet decoder
    --> encoder --> mod --> USRP sink.




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