Mixing it Up - 11g
With any of the 802.11g proprietary throughput enhancement technologies, there's always the question of how well they handle standard 802.11g (and 11b...remember that?) clients. And since Linksys' marketing material says "Even your standard Wireless-G and -B equipment will work better when communicating with SRX-enabled devices", I thought I'd better check out that claim, too.
The first thing I checked was how True MIMO and standard 11g clients would mix. I set up an IxChariot test using two pair of endpoints (Figure 17). Each pair ran a Throughput.scr script using TCP/IP, sending 200,000 Bytes of data at a time and looping for 1 minute in real-time mode. One version of the script started the Linksys SRX (True MIMO) client first, then the other client 10 seconds later, while a second script reversed this delay. For each client type, I ran four tests:
- SRX (True MIMO) starts first, both pair Uplink (client - also refered to as STA - to AP)
- SRX (True MIMO) starts second, both pair Uplink
- SRX (True MIMO) starts first, both pair Downlink (AP to STA)
- SRX (True MIMO) starts second, both pair Downlink
Figure 17: Mixed WLAN Test Setup
Note is that in all cases, I used the default settings for the tested clients and for the GX. This means that 11b protection (the GX calls this control CTS Protection) was disabled in the GX. Also note that both clients were located within 10 feet (3 meters) of the router. My first test used a Broadcom-based Linksys WPC54G original version card to see how the GX handled mixed True MIMO and 11g clients.
Figure 18: Mixed SRX and 11g uplink - SRX first
(click on image to enlarge)
Figure 19: Mixed SRX and 11g uplink - 11g first
(click on image to enlarge)
Figures 18 and 19 show that the 11g client definitely gets the short end of the throughput stick, even though the True MIMO pair drops its throughput when it senses the 11g pair on the air. I also ran this test with both clients running downlink (AP to client) and obtained similar results.