Re: [Discuss-gnuradio] How the upstream block of TDMA engine get the current time of the network

[John Malsbury]

Alex,

I'm on a machine without GNU Radio installed, so I have to confirm that I'm actually sending the right examples, but the attahced files may add some insight.

The examples were intended for demonstration of the timed streaming features and currently rely on a 1 PPS signal to provide synchronization across multiple units.

-John

On Mon, Feb 4, 2013 at 8:33 AM, Alex Zhang <address@hidden> wrote:

Hi Josh,

Sorry the unclear question. Actually I am asking how the transmitter organize the TX samples to the specified time slot..

On Mon, Feb 4, 2013 at 9:45 AM, Josh Blum <address@hidden> wrote:

On 02/04/2013 01:32 AM, Alex Zhang wrote:
> Previously, the pre-cog introduced a simple implementation of TDMA:
> http://gnuradio.4.n7.nabble.com/Introduction-to-Pre-Cog-td37906.html
>
> I read roughly the code in the tdma_engine.py.
> For the transmitter, it seems that this tdma_engine works like a throttle
> to send the messages to the downstreams only when the time_update is  later
> than the time_transmit_start.
> And these time are computed based on the tags in the incoming items
> inserted by upstream block.
> My question is that, where does the upstream block get the correct time? I
> know that the usrp_sink can get_time_now but it is on the very downstream,
> and it is different block which means different thread.
>
> If my question is not clear, please give your comments.

time indication should be coming from the usrp source block. the rx
samples are timestamped, which allows the engine to line up with a time slot

-josh

>
> Thanks.
>
>
>
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Alex,

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tdma_hier.grc
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tdma_radio.grc
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