levy
commented
4 years ago Hmm, I don't think that the larger AIFSN value is enough to explain this. The larger NAV vector mean value is suspicious. I guess due to the TxOp the channel is protected for a longer period of time. My feeling is that there may be an issue that needs to be fixed. Unfortunately, I lack the time to look into this in more detail right now. Nevertheless, thanks for reporting, I'll come back eventually.
Hi, we are currently looking into using HCF/EDCA and QoS in IEEE 802.11. During our testing, we experienced that EDCA results in a far lower throughput than DCF when using only traffic that is classified as "best effort". To show this, we modified the wireless QoS showcase to include only the "best effort" traffic and disabled MSDU aggregation. The throughput over time measured at the application layer is shown in the following figure with the red plot showing the HCF/EDCA result and the blue plot showing the DCF result:
It can be seen that using HCF/EDCA results in only about 2/3 of the throughput that can be achieved with DCF. We have not found out yet where this reduction in throughput results from. One difference between both channel access methods that we found is that the AIFSN is 3 for AC_BE in HCF/EDCA and 2 in DCF. However, this seems to be only a minor difference and also changing the AIFSN for AC_BE in HCF/EDCA to 2 results in no significant change in the results.
One thing that we noticed is that using HCF/EDCA results in higher values for the NAV. However, we do not know why it is like this.
As we are unsure if this is a bug in INET or a valid difference between these two channel access methods, we hope you do not mind that we ask this question here. We appreciate any advice.
Our simulation model can be found here: dcfvshcf.zip