The good news is that using WPA doesn't have to end up costing you throughput. But, at least in the early going, all WPA implementations aren't created equal. Since Broadcom seems to be leading the pack slightly in WPA releases, I'll start with a few examples of products based on their chipsets.

NOTES:

- As with draft-802.11g when it first appeared, WPA is in its early stages. Even though WPA is a released spec., manufacturers are still on the learning curve and tuning their implementations. Your mileage may vary when you try your own experiments with later drivers.

- All testing was done under close-range conditions, with client and AP about 5 feet apart and data flow from client to AP. All clients were tested in a Dell Inspiron 4100 notebook running WinXP Home SP1 with WPA patch.

Since Belkin was first to have both client and AP that are 11g released-spec and WPA complaint, my initial testing focused on those products. Figure 10 shows a throughput comparison for a Belkin F5D7010 11g Client and Belkin F5D7130 11g AP test pair with the following test conditions:

Figure 10: Belkin F5D7010 11g Client and Belkin F5D7130 11g AP
Condition 1 Throughput vs. Security modes
(click on image for a larger view)

The results are a little tough to see using the plots due to the periodic change in throughput that seems to be a part of at least these Belkin released-spec 11g products. But the numbers in the screen shot reveal that the only throughput hit is approximately 15% in the WPA-PSK TKIP mode. Guess now we know why Broadcom chose to add the optional support for AES!

To see if there was a difference in Broadcom client implementations, I tested a Linksys WPC54G with the first driver that Linksys released that supported WPA, but not 11g spec compliance.

Figure 11: Linksys WPC54G 11g Client and Belkin F5D7130 11g AP
Condition 1 Throughput vs. Security modes
(click on image for a larger view)

Figure 11 shows more consistent throughput performance in all modes, but still has about a 15% throughput decrease in WPA-PSK / TKIP mode.