I used the open air test method to test the 825's wireless performance. Testing was done using a D-Link DWA-160 B1 USB adapter 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 Win XP SP2 1.02.01.0000 driver and D-Link V2.1 client utility during testing. The router had the latest 1.01 firmware and I left all factory default settings in place, except to set channel 1 for the 2.4 GHz mode tests and channel 36 for the 5 GHz tests.
Figure 9 shows a composite of downlink throughput tests made at the six test locations in four wireless modes: 2.4 GHz, 20 MHz channel; 2.4 GHz, 40 MHz channel; 5 GHz, 20 MHz channel; and 5 GHz, 40 MHz channel. Each column represents the average throughput from a one minute test.
You can see best-case (Location A) throughput is 94 Mbps using a 40 MHz channel in the 2.4 GHz band. This is significantly better than the 68 Mbps 855 did for the same test. But keep in mind that I used different client adapters, although the NETGEAR WNDA3100 I used with the 855 is Atheros based.
Figure 9: DIR-825 six location downlink summary
Like most dual-band products that I've open-air tested so far, the client wasn't able to even see the 825 in test Locations E and F when using the 5 GHz band. The connection was also iffy in Location D using 20 MHz mode, averaging only around 4 Mbps.
In the 2.4 GHz band in the 40 MHz bandwidth mode, the DWA-160 could see the 825 and connect, but not reliably pass traffic in Locations E and F. In the 20 MHz mode, the client could still see the 825, but connection was very iffy at Location F.
Figure 10 shows a composite of the IxChariot test results running downlink 2.4 GHz w/ 20 MHz channel. There are plenty of 50% drops in throughput, which would not deliver trouble-free high-def video streaming.
Figure 6: Six location wireless throughput - 2.4 GHz, 20 MHz channel, downlink
Figure 11 shows the six location plots in the uplink direction. Performance was very similar to downlink, with best-case throughput of 83 Mbps again measured at Location A using a 40 MHz channel in the 2.4 GHz band. Unfortunately, uplink was also essentially unusable in locations E and F. Throughput variation actually was lower running uplink, however, as you can see in this plot.
Figure 11: DIR-825 six location uplink summary
Wireless Security Performance
I also tested for throughput reduction with wireless security set to WEP, WPA/TKIP and WPA2/AES and found the usual penalty in WEP and WPA/TKIP—about 70% in this case (Figure 12). The difference between the results for no encryption and WPA2/AES is basically due to high throughput variation.