Introduction
This is part 2 of the blog series on OFDMA in Wi-Fi. In the first part of our series, we have done tests with VoIP calls between WiFi6 clients connected to a Wi-Fi6 AP with OFDMA enabled and compared it with a case where the OFDMA feature has been disabled on the AP.
https://aletheatech.com/blog/ofdma/
In this blog we would examine the impact of OFDMA on DL TCP for a similar setup. We would also change the packet size to check to see if this gives us any insight on the workings of OFDMA allocation algorithms.
Test Setup
To test the impact of OFDMA, we have used the test setup which contains 1 LinA box which has 12 intel AX200[2] cards each.[1]. So we have a total of 12 clients with 1 AP in a single RF Chamber. Alethea End Point is a specialized equipment that can act as source or sink for different types of traffic (ex:Iperf3,video streaming, browsing).We would use iperf3 for generating TCP traffic and in parallel ping traffic is used to measure latency independently. At the time of the test, support for Buffer Status Report is not present for Intel AX200 and hence OFDMA allocation doesn’t happen on UL for these clients. However, BAs from the clients are using OFDMA
The test equipment gives detailed information on traffic (latency, throughput) as well as a sniffer output with analysis of types of frames seen on air.
Test Results IPERF3 DL TCP
Tests were done in groups of 2,4,8,12 tests were done for packet sizes 64,256,512,1370.The results for the DL TCP Iperf 3 traffic are tabulated below.
OFDMA ON
OFDMA OFF
The system also calculates the Total % of DL Data with MU Frames from the sniffer logs. An example for 2 packets sizes is shown below
Inferences
- There is no significant gain in aggregate throughput with OFDMA switched on. The 64 packet throughput for 4 clients is the only case where there is some improvement.
- The aggregate throughput doesn’t seem to change with packet size. The 64 packet throughput is an outlier though.
- Latency results with and without OFDMA do not show any pattern or improvement
- The MU Frame % seems to increase with the number of clients to an extent.
Conclusion
OFDMA as a technology in Wi-Fi is evolving. As seen from the experiments, we have seen some improvement for specific use-case of a few VoIP calls but no clear cut improvement in aggregate throughput. The theoretical efficiency predicted has not come into light as yet.
References
1)https://aletheatech.com/wicheck-lina-wifi-6e-testing/
