Legacy Neighboring WLAN Tests
I decided to run my Legacy Neighbor / CCA tests, because this is the first time I've had a Ralink draft 11n client in the lab and it was mixed with an Atheros-based AP. (See this page for an explanation of CCA.) I was surprised by the results!
For this test, I configured the Vision as an AP, set to 20 MHz+40 MHz auto mode, Wireless Channel 1 and no encryption. This made Channel 1 the primary channel and Channel 5 the extension.
I then set up a second wireless LAN using a Linksys WRT54G router (original rev) and WPC54G V3 CardBus card. The WRT54G had most recent firmware and was set to its default Mixed mode and Channel 5—the extension channel. I also operated it as an AP and connected it to the same switch that the Vision was connected to.
Two IxChariot throughput.scr scripts were used to drive traffic to both 11n and 11g test pairs. I tested both uplink and downlink traffic and alternated between having the 11n and 11g WLANs start first. (If you need a diagram of the test setup, this one showing a similar test setup should give you the basic idea.) I also used the Cognio Spectrum Expert to monitor spectrum use.
Figures 20 and 21 clearly show that the Draft 11n WLAN recognizes the presence of the 11g WLAN in the Extension channel and tries to accomodate it. The Cognio spectrum display sure looked like the Vision fell back to using only the Primary channel (Channel 1) the entire time when the 11g WLAN was active. This would be a first among all of the products that I've tested.
While I've seen other draft 11n products, the D-Link DIR-655 in particular, try to not trash a neighboring 11g WLAN using its Extension channel, the Vision seems to have moved the ball a bit more toward the goal.
Figure 20: CCA Test - Downlink, N starts first
Although its implementation is by no means ideal, the Vision's algorithm seems a bit better tuned than the DIR-655 and doesn't overcompensate and kill the 11n network's throughput.
Running uplink is even better, with the Vision WLAN appearing not to flail around as much. But the 11n WLAN still gives up perhaps more throughput than it should, dropping down to 11g speed.
Figure 21: CCA Test - Uplink, N starts first
Although not shown, similar results were observed when the 11g WLAN was on the air first and the Vision WLAN started later. Throughput is far from smooth when both WLANs are on the air. But the bandwidth sharing is much more equitable than any other product that I've seen so far.
I ended up liking the N1 Vision more than I thought I would, despite its flashy, but not-so-useful front panel display / navigation pad and first-generation routing features. What saved the day is its wireless performance.
Although it didn't turn in the fastest wireless throughput, its overall throughput vs. path loss curves rank it among the top-performing Draft 2.0 11n products that I've seen, in both 20 and 40 MHz channel bandwidth modes.
The icing on the cake, however, is that it plays well with others when you enable the 40 MHz channel mode. Not perfect by any means, but much better than any other Draft 2.0 product that I've seen to date. And don't forget that its gigabit switch does support Jumbo frames.
The main thing going against it is its price, which currently starts around $160 and goes up to over $200! Although Belkin might be trying to pay for the fancy case and front panel display, there are just too many other single-band draft 11n routers available with better feature sets, lower prices or both.