802.11ac actual physical and application layer data rates in ns-3.26

[Mahesh]

Hi all,

I want to know what are the actual physical and application layer data rates supported with 802.11 ac in ns-3.26. I ran the vht-wifi-network.cc example with MCS = 8, Channel Width = 80 MHz and Guard Interval = 400 ns and it gave a TCP throughput of around 264 Mbps.

When I run other simulations of my own with multiple nodes in adhoc mode with the same 802.11 ac parameters, with spectrumPhy, multi-model spectrum channel and friis propagation loss and constant speed propagation delay models, I get around 42 Mbps TCP throughput only. Though a fall in rates is expected, but what is the upper bound on the TCP throughput that I can achieve in this case.

In the wikipedia link, it shows a data rate of 390 Mbps for MCS = 8, Channel Width = 80 MHz and Guard Interval = 400 ns. It is the application/TCP layer rate, right ? Also, what all factors make it difficult to realise the actual rates that 802.11 ac should support in ns-3.26.

Kindly elucidate.

Thanks,
Mahesh

[Yiannis]

Hi Mahesh,

First, the data rate of 390 Mbps is the physical bit rate and not TCP or MAC throughput (App < TCP < MAC < 390).
Secondly, there are a lot of factors that affect throughput (i.e. IFS, retransmissions, ACKs, aggr size etc.).
Retransmissions due to collisions could be the case for you (multiple number of nodes). 42 Mbps is per user or the aggregated one?
 
yiannis

[Mahesh]

Hi Yiannis,

Thanks for your kind reply. So I have 5 nodes (see the attached topology), with the central node 0 sending TCP traffic to nodes 1, 2, 3, 4. I am using a directional antenna configured on the central node. The total throughput obtained for all the 4 flows (0--1, 0--2, 0--3, 0--4) combined is 42 Mbps.

I guess the fall in throughput is also due to 802.11 ac features not being fully supported in ns-3.26 from what I heard. Could you please tell whether I can expect such a throughput with 802.11 ac parameters.

Thanks,

Mahesh

[Sebastien Deronne]

Please attach your simulation script to better help you.

[Mahesh]

Hi all,

When I run the attached scenario, I get a combined throughput of around 42 Mbps with 802.11ac. Node 0 is sending TCP traffic to nodes 1, 2, 3, 4. Why am I getting such a low combined throughput ?

I have attached the script, flow stats and the topology. Please go through it. You can run it as it is.

Looking forward to your kind reply at the earliest.

Thanks,

Mahesh

[Mahesh]

Please reply.

[Sebastien Deronne]

Mahesh,

I do not forget you and I will reply asap, I had no time so far to investigate your issue.

Hopefully this week I will go through it.

 

[Sebastien Deronne]

The throughput is matching the tx offered, so this is not a wifi issue.