Wireless Performance - 2.4 GHz
I tested the 855 using our wireless test procedures, which use both open-air testing and Azimuth's ACE 400NB Channel Emulator. I started testing the 855 by running open-air IxChariot tests in my lab with the router and notebook containing the DWA-160 Xtreme N Dual Band USB Adapter that D-Link sent along, about 10 feet away from each other in the same room. No other networks were active. But when I saw the results in Figure 8, I had to switch into detective mode.
Figure 8: 2.4 GHz, 20 MHz mode wireless throughput w/ DWA-160
Long story short, the 855 was fine and the problem was the DWA-160's driver. D-Link said it is working on an updated driver, but I didn't want to hold up the review. So I tried both a Linksys WPC600N Dual-band Notebook card and Netgear WNDA3100 dual-band USB adapter, which both turned in proper performance.
I settled on using the Netgear adapter for the remainder of my testing because it is essentially a copy of the DWA-160, using the same Atheros AR9170 MAC/BB and AR9104 Dual-band 2x2 MIMO radio.
The WNDA3100 USB adapter was inserted into a Fujitsu P7120 Lifebook (1.2 GHz Intel Pentium M, 504 MB) notebook running WinXP Pro SP2 with all the latest updates. I used the latest 220.127.116.11 driver and Netgear Smart Wireless 18.104.22.168 utility during testing.
The router had 1.00 firmware and I left all factory default settings in place, except to set Channel 1 for 2.4 GHz tests and Channel 36 for 5 GHz tests. I left WISH enabled (which is the default).
Figure 9 shows a composite IxChariot plot of 2.4 GHz band wireless uplink, downlink and simultaneous up and downlink tests in the default 20 MHz channel bandwidth mode. The best 1 minute average of 56 Mbps was found running simultaneous up and downlink. Similar to other Atheros-based products that I have tested, throughput seems to ramp up at the start of the test. Speed seems to bounce around a bit, too.
Figure 9: Up and downlink throughput - 2.4 GHz band, 20 MHz bandwidth
I repeated the tests switching to Auto 20/40 mode and used a Cognio Spectrum Expert to confirm that Channels 1 and 5 were used with the Channel Width control set to Auto 20/40 MHz. The plot is here, where you can see improved average speeds of just shy of 80 Mbps up/down, 68 Mbps down and 66 Mbps up.
Since not everyone is a fan of the throughput vs. path loss method, I did a quick walk around to my five test locations. With a 2.4 GHz, 20 MHz mode connection, Location 3 speed dropped into the mid-teens and down below 1 Mbps in my difficult Locations 4 and 5. (The Location 5 connection was very tenuous).