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signetlabdei / ns3-mmwave-iab

IAB feature for the ns-3 mmWave module
GNU General Public License v2.0
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Uplink hop delay in linear topology #1

Closed mnegroy closed 4 years ago

mnegroy commented 5 years ago

Hello!

I am now measuring uplink delay in linear multi-hop topology.

What I found is that even though I eliminated the propagation loss and interference, uplink UDP traffic suffers from approximately 10 ms delay per hop.

I think this delay is abnormal considering scheduling delay. If you have any idea on the problem, I'd appreciate it if you let me know.

mychele commented 5 years ago

Hi, that would depend on the saturation of the network, the interaction of the RLC buffering and scheduling, and the frame structure that you are using. Let us know if you can understand what is the cause of the latency - if it's a bug, we can work on a fix together. Thanks, Michele

Il giorno ven 29 nov 2019 alle ore 03:39 mnegroy notifications@github.com ha scritto:

Hello!

I am now measuring uplink delay in linear multi-hop topology.

What I found is that even though I eliminated the propagation loss and interference, uplink UDP traffic suffers from approximately 10 ms delay per hop.

I think this delay is abnormal considering scheduling delay. If you have any idea on the problem, I'd appreciate it if you let me know.

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Postdoctoral Researcher Dept. of Information Engineering (DEI) - SIGNET Research Group University of Padova Via Gradenigo 6/B, 35131 Padova (Italy)

email: michele@polese.io web: polese.io - mmwave.dei.unipd.it

mnegroy commented 5 years ago

Topology I used is Doner - IAB - IAB - ... - IAB - UE

Here, just the UE is generating UDP traffic with 1500 bytes and inter-packet interval of 200 us. (56 Mbps) I think this is light traffic considering the system bandwidth.

Thanks. Jungjun Kim

mychele commented 5 years ago

Hi, and what is the subframe length, number of symbols per subframe? Did you try the same setup in downlink?

mnegroy commented 5 years ago

Hello, The subframe length is set to 1 ms and symbols per subframe is set to 240, which are the default configurations of your simulator. (All other settings are the defaults too)

And yes I tried downlink scenario. Also the similar problem happens, but in downlink scenario the hop-delay is more varying.

Thanks.

mychele commented 5 years ago

You can try to play with the SF duration and see if you can decrease the latency (especially for uplink, where reporting & scheduling at the BS introduce more delay)