Mixed mode
My last round of tests checked the handling of simultaneous 802.11b and 11g traffic. Again using Chariot, I set up a test using two client pairs. The reference 802.11g test pair for each test was a WinXP Home Dell Laptop with USR5410 Cardbus card to Win98SE Ethernet client. The second pair used a WinXP Home Compaq Presario 1650 Laptop with various 802.11b cards to a different Win98SE Ethernet client. I tested the following cards:
- Linksys WPC11 v3 (Intersil PRISM III)
- NETGEAR WAB501 (Atheros 5001X ) [forced to 11b mode]
- ORiNOCO Gold (Agere Systems)
- D-Link DWL-650+ (TI ACX100)
In each test, I started the USR card first, then kicked in the 802.11b card. Both cards then run simultaneously for awhile, with the USR card stopping first to let the 11b card finish by itself. The AP was set to Mixed mode, 4x mode enabled for all tests. Figures 13 -16 show the results.
Figure 13: Mixed mode test - USR5410 & Linksys WPC11 v3
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Figure 14: Mixed mode test - USR5410 & NETGEAR WAB501
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Figure 15: Mixed mode test - USR5410 & ORiNOCO Gold
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Figure 16: Mixed mode test - USR5410 & D-Link DWL-650+
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It was interesting to see that the Atheros-based card, which had the worst 11g performance, also had the next-to-slowest 11b mixed-mode throughput. The honors for slowest 11b mixed-mode performance go to the ORiNOCO Gold with Agere Systems chipset.
The other point of note is that the USR 11g card's throughput dropped to about 12Mbps once an 11b station associated with the AP. This is pretty much what I've seen with other 802.11g products. What's different for USR is that it takes 15 minutes for throughput to return to its higher (20Mbps) value once all 11b stations shut down! This will be a moot performance point for folks who need to run mixed 11b, b+ and g networks, but I'm not sure why this wait is so long. Competitive APs typically take 1 minute or less to recover once the last 11b client disassociates.
So what's all this mean? Here are my takeaway bullet points:
- Superior throughput vs. range
- No throughput boost with "4x / turbo"
- Works with all tested clients with performance variation typical of competing products