Using the Curves
The result is a complete throughput profile of the AP and STA pair over its entire signal operating range. Figure 4 shows sample downlink test results for a D-Link DIR-655 and DWA-652, plotted along with an 100 Mbps Ethernet line for reference.
Figure 4: Throughput vs. path loss test results
Note that the X axis in Figure 4 is Path Loss (or signal attenuation between AP and STA) in dB, not distance. Because there is no fixed relationship between Path Loss and distance due to the varying attenuation characteristics of real-world environments, these results can only be used comparatively. In other words, while they won't tell you exactly how far you can expect a product to operate, you will be able to use the results to compare the relative performance of products.
How you use the curves to select products depends on the performance that you are looking for. But here are some general guidelines:
- The further out that the curve's "waterfall" portion is (that's the part where throughput starts to fall off), the better. This means that throughput will remain higher for longer distances.
- The steeper the slope of the "waterfall", the quicker a product will lose connection as you move out of range.
- Products that operate at path losses of 100+ dB are not necessarily better. 5 Mbps might be fine for web surfing and checking email, but no good for video streaming or large file transfers.
Since we have a quiet RF environment, other wireless testing is conducted in free air using the antennas supplied with the products. Tests are run with the IxChariot throughput.scr script and the products in their default settings unless otherwise noted.
Other tests include:
Maximum throughput - We run a maximum throughput test for 1 minute with devices approximately 3 to 10 feet apart. This serves as a "sanity check" on the Azimuth results and is the throughput plot typically shown in most reviews.
Security mode throughput - We set AP and STA to any of the following security modes that are supported—WEP 128, WPA-PSK / TKIP and WPA2 / AES—and run a throughput test for 1 minute.
Other testing is performed as needed, including throughput with mixed clients and neighboring WLAN interaction testing. These tests are described in the reviews in which they are run.
If you have comments or questions about these test methods, please post a comment below or contact us.