Belkin N1 Wireless Router: Neighbor-Friendly but Flawed Draft 11n

Wireless Tests - Mixed and Neighboring WLANs

I didn't spend much time checking out how well the N1 router supported other flavors of wireless clients. My previous draft 11n product interoperability tests told me that I probably would be able to associate clients with the N1 router just fine, and that other draft 11n or 11g products would at best operate at 11g rates, i.e. around 20 Mbps.

Turns out that's pretty much what I found. I tried a Linksys WPC54G 802.11b/g Cardbus card based on Broadcom's Airforce 11g chipset and Belkin's own "Pre-N" Cardbus card that uses the first-generation Airgo "True MIMO" chipset. Figure 23 shows the results from the "Pre-N" card run.

Belkin Pre-N client with N1 router - Up and Down throughput

Figure 23: Belkin Pre-N client with N1 router - Up and Down throughput (click to enlarge)

As expected, total average throughput would come in around 20+ Mbps, if it weren't for the throughput dropout problem which appears to carry over into non-xspaN clients. I obtained similar, but slightly higher, results with the Broadcom-based WPC54G card.

As an additional test, Netgear's SPH101 Skype Wi-Fi phone was able to associate and work just fine with the N1 acting as an AP.

After my disappointment with the N1's throughput variation and security mode throughput loss, I was pleasantly surprised by the results of my "bad neighbor" (adjacent WLAN interference) check. To recap the method, I set up an 802.11g WLAN comprised of a Linksys WRT54G router and WPC54G Cardbus card in the same room as the N1 Both routers are set to function as APs, are set to Channel 6 and are connected to my LAN so that the IxChariot console can control everything.

Figure 24 shows that the N1 cooperates very well when running uplink traffic, quickly dropping its throughput in the presence of 11g traffic. I presume that the N1 switched from its 40 MHz channel-bonded mode to its 11b/g compatible 20 MHz mode, but since the card driver doesn't appear to update its link status information I couldn't confirm this.

"Bad neighbor" test results - uplink

Figure 24: "Bad neighbor" test results - uplink (click to enlarge)

Figure 25 shows similar "good neighbor" behavior with downlink traffic.

"Bad neighbor" test results - downlink

Figure 25: "Bad neighbor" test results - downlink (click to enlarge)

Needless to say, I'm very pleased to see these results, especially from Atheros. Their experience with Super-G should have given them the technology to be able to constantly keep track of what's happening on the airwaves in between transmissions, and it appears that it has. So right now, Atheros xspaN is the only neighbor-friendly draft 802.11n technology.