To see how the Extreme handled mixed draft 11n and 11g clients, I set up a second notebook with a Linksys WPC54G V3 11b/g card (Broadcom chipset). Both it and the MacBook were associated with the Extreme, which was set to its default 2.4 GHz "b/g compatible" mode with 20 MHz bandwidth. I then ran two IxChariot throughput.scr streams, alternating the STA that got on the air first.
Figure 32 shows how uplink throughput was shared when the 11n pair started first, while Figure 33 shows the 11g pair starting first.
Figure 32: Mixed 11n, 11g STAs - Uplink, N starts first
The results follow the pattern that I've seen with other draft 11n products,i.e. the 11g STA gets knocked down to 11b speeds. In this case the 11g throughput is knocked down to about 6 Mbps from its normal 22 Mbps or so, or about 75%. The 11n pair's throughput hit is only about 33%.
Figure 33: Mixed 11n, 11g STAs - Uplink, G starts first
I also ran these tests in downlink (Figure 34) which shows a smaller throughput hit for the 11n STA (about 20%), but about the same for the 11g.
Figure 34: Mixed 11n, 11g STAs - Downlink, N starts first
That about wraps up the wireless testing. I didn't run any Legacy Neighbor / CCA tests because the 40 MHz bandwidth mode is locked out in 2.4 GHz.
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