I tested using the open air test method described here using a Belkin N+ Wireless USB Network Adapter (F5D8055 v1) 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 18.104.22.168 driver and Belkin's 22.214.171.124 wireless utility during testing. I left all factory default settings in place, except to set Channel 1 for 2.4 GHz tests.
Figure 9 shows a composite of downlink throughput tests made at the six test locations in the 20 MHz and 20/40 MHz bandwidth modes.. Each column represents the average throughput from a one minute test. Best case downlink throughput in the 20 MHz mode was 61 Mbps and 84 Mbps in 20/40 MHz mode.
Figure 9: Belkin N+ wireless benchmark summary - downlink
The table in Figure 9 shows 0 for Location F, but the Belkin USB adapter in fact was able to associate to the Plus in that spot. However, there wasn't enough reliable throughput to either successfully ping or to run a complete test. Actually, I was able to get 0.016 Mbps of throughput running uplink in Location F in 20 MHz mode. But since I round to one decimal point, the chart shows 0.
Figure 10 shows a composite of IxChariot plots for all 20 MHz mode downlink tests. Best case uplink throughput in the 20 MHz mode was 70 Mbps and 85 Mbps in 20/40 MHz mode. Throughput variation seems to calm down a bit with lower signal level. But note the ramp-up in throughput at the beginning of each run. The 40 MHz mode downlink plot is here and shows much more variation in the Location A test.
Figure 10:Wireless throughput detail - 2.4 GHz, 20 MHz channel downlink
Figure 11 pulls together all of the uplink average test results, which are reasonably well matched to downlink speeds. As with downlink, using 40 MHz mode in uplink provides an effective throughput boost in the stronger signal test locations A through D.