Legacy Neighbor WLAN Tests
My last set of tests was to check the Clear Channel Assessment (CCA) mechanism that is supposed to ensure "neighbor friendly" operation with legacy WLANs. (See this page for an explanation of CCA).
For this test, I configured the 834B as an AP, set to 40 MHz bandwidth mode and Channel 1 with 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 834B was connected to.
I then set up two IxChariot throughput.scr scripts 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.
Figure 21: CCA Test - Uplink, N starts first
As has been the case with all other Draft 2.0 11n products, the 11n products dominate and severly reduce the throughput of the 11g WLAN operating on the extension channel. Spectrum monitoring shows that the 11n WLAN continues to operate with 40 MHz of bandwidth, regardless of 11g WLAN activity.
In the 834B's case, the 11g WLAN essentially is stopped while the 11n WLAN is on the air running uplink (Figure 21). Downlink (Figure 22) seems to give the 11g WLAN a little more air time, but throughput is still severly limited, i.e. ~1 Mbps.
Figure 22: CCA Test - Downlink, N starts first
If the 11g WLAN starts first, it seems to do a little better when the 11n WLAN goes active. But throughput is still around 1-2 Mbps.
Despite the performance differences, the real choice betwen the WNR854T and WNR834B comes down to the different features they offer. If a gigabit switch is most important, then go with the 854T. But if you must have wireless repeating and want to see if QoS can help better manage your paltry upstream bandwidth, then go for the 834B.
The choice is complicated that the more full-featured router (the 834B) is actually street-priced around $20 less than the 854T. That's not much in the grand scheme of things, but still a factor for some folks.
I think Netgear would be better off consolidating all the features into one single-band 11n box and putting its efforts into a nice dual-band offering.
In the meantime, if you want gigabit and QoS in one product, then the D-Link DIR-655 is still the way to go and is priced midway between the 834B and 854T. But then you lose wireless bridging. The search for the perfect draft 11n router continues...