Good Neighbors Are Hard To Find

But the more interesting question is what happens to available bandwidth when there are neighboring WLANs in range that you have no control over. My first "neighbor" simulation used the two-WLAN setup that I described previously. But this time the IxChariot data went to the "Neighbor" WLAN and the video stream to the "Home" WLAN. I thought of this as an almost best case scenario since all but one of the products in the WLANs come from the same vendor and use the same Broadcom chipset that doesn't get too fancy with proprietary throughput enhancement tricks.

But Figure 9 below reveals significantly different behavior from that in Figure 6. In this setup, the "Neighbor" WLAN didn't politely give up the bandwidth needed by the "Home" WLAN video stream. The result was an unwatchable video that nonetheless managed to play completely to the end. This is behavior more like I would expect, with each WLAN battling for airtime and bandwidth.

Figure 9: Linksys "Home" LAN video w/ mixed "Neighbor" WLAN (click image to enlarge)

I next moved on to see how a Super-G neighboring WLAN would affect the home WLAN. Super-G technology has maintained its "bad neighbor" reputation, despite Atheros' many attempts to redeem it. I pulled out a Netgear WGU624 Dual-Band router, which I last used in my Do Extended WLAN technologies deliver article, upgraded it to the latest 2.0.1.1 firmware and substituted it for the Linksys WRT54G in the "Neighbor" WLAN. I shut off the 802.11a radio and adjusted the settings on the 11g radio as shown in Figure 10.

Figure 10: Netgear WGU624 wireless settings (click image to enlarge)

According to Netgear's help screens, these settings should have put the router into its most neighbor-friendly mode and kept it from switching into its neighbor-killing channel bonding mode with non Super-G WLANs in range. But the behavior shown in Figure 11 shows why Super-G still maintains its reputation as the technology of choice for wreaking WLAN revenge.

Figure 11: Linksys "Home" LAN video w/ Super-G "Neighbor" WLAN (click image to enlarge)

The plot shows that not only does the Super-G WLAN battle the home WLAN streaming video (and win) for bandwidth during the early part of the plot, but that it does switch into channel bonding mode shortly before a minute has elapsed. Looks like Atheros' "Adaptive Radio" feature - that is supposed to prevent this from happening - still needs work. Needless to say, the result on the "Home" WLAN was that the video wouldn't even start.

By the way, sharp-eyed readers might note QoS set to "None" in Figure 10. I actually tried it both ways, didn't see any difference in behavior and left it off.

So how does a Super-G WLAN work if it's your WLAN? Quite well, actually, as Figure 12 shows. I got a little more thoughput than with the Linksys / Broadcom WLAN, even without channel-bonding and the video played without problems.

Figure 12: Shared data and video stream - Atheros SuperG AP and Client (click image to enlarge)

Curiously, I didn't see the Super-G WLAN switch into channel-bonding mode when the Linksys / Broadcom WLAN was idle - behavior that I would have expected given the fact that it would switch when the Linksys / Broadcom WLAN was active!

Tags: Tutorial, Video streaming, WiFi,

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