|
| From: | David Scaperoth |
| Subject: | Re: [Discuss-gnuradio] Latency with B200-mini / Ack Messages for Transmit |
| Date: | Fri, 15 Apr 2016 06:48:44 -0400 |
See below for some thoughts/questions. Good luck.
If you want to optimize the b200 transport latency you need a simpler setup....
On Apr 15, 2016 3:52 AM, "murat tas" <address@hidden> wrote:
>
> Hi,
>
> I have a use case similar to the one mentioned in this series of posts:
> http://lists.gnu.org/archive/html/discuss-gnuradio/2013-04/msg00421.html
>
> I am using B200-mini with gnuradio flowgraph containing tx and rx parts. Transmit part contains a udp source block connected to a physical layer block(that processes channel encoded bits) and that is connected to a uhd sink block. Receive part has similar structure with uhd source, phy block and Socket Pdu block.
>
> The transmit part should send data continuously to B200-mini. So there should be signal broadcasted all the time.(Think of it like a base station broadcast signal) To achieve this, the upper layer of gnuradio flowgraph sends packets periodically to gnuradio.
>
> The receive part has very low latency when i measure with a known signal( from a test instrument).
>
> When using both transmit and receive parts, I measure the time passed between the moment a packet enters the udp source block on transmit side and the moment the same packet sent out from the receive part of the flowgraph to upper layer. The time passed changes between 150 to 300 ms for each run of the flowgraph. These numbers are for GR_FIXED_BUFFER_SIZE decreased to 2048. With default value of 32k, the time passed is around 2-3 seconds.
>
> I have three questions:
>
> 1) What to do to fix the latency so that it does not change each time the flowgraph is run?
> 2) Can I decrease latency below the measured values?
What is the latency without the b200 (loopback flow graph)?
Does the latency change/drop if you didn't have the udp source/sink?
What do you want your latency to be?
> 3) Can B200-mini send ack packets for send calls, when there is no sob/eob flags are used?
>
> If anyone previously dealt with a similar use case can offer alternative methods, it would be great!
>
> Thanks in advance,
>
> Murat
>
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