Throughput vs. Path Loss
Of course, after I had gone through all the walk-around tests, it occured to me that I could get around the Azimuth ACE MIMO test software's limitation of not being able to handle a client that's an Ethernet bridge. All I had to do was use the 1522 as an AP and throw a dual-band client into my notebook. So I also ran a full set of throughput vs. path loss tests using the Azimuth system to get a more detailed look at how the 1522 performed over its entire dynamic range.
I started out by using the Netgear WNDR3100 RangeMax Dual Band Wireless-N USB 2.0 Adapter, which uses an Atheros Xspan chipset. But very low (8 - 9 Mbps) uplink throughput with the router set to its default 2.4 GHz, 20 MHz bandwidth caused me to swap in a Linksys WPC600N Ultra RangePlus Dual-Band Wireless-N Notebook Adapter (Cardbus format), which uses a Broadcom Intensifi draft 11n chipset. The WPC600N not only solved the uplink problem, but had higher downlink throughput, too!
Figure 14 shows throughput vs. path loss performance for all 2.4 GHz modes and directions. Uplink performance appears to be better than I achieved in the walk-around tests with the pair of 1522s. This could be due to the three antenna configuration in the WPC600N card.
It's a bit hard to tell in this composite plot, but the 40 MHz mode tests stop 3 dB sooner than the 20 MHz.
Figure 14: 2.4 GHz Throughput vs. Path Loss mode comparison
You can't directly compare 2.4 and 5 GHz results from the Azimuth system because it doesn't correct for the higher attenuation of 5 GHz signals. But it's plain to see that 5 GHz range is significantly less than the 2.4 GHz mode and falls off faster. But that's the story for pretty much all 5 GHz draft 11n products I've tested. So we have to compare the 1522 to its competition.
Figure 15: 5 GHz Throughput vs. Path Loss mode comparison
Figure 16 compares the 1522 with the D-Link DGL-4500 [reviewed] and the current dual-band darling, the Linksys WRT600N [reviewed]. Keep in mind that the 1522 may be at some disadvantage in this comparison because it is not being used with a "matching" adapter.
Figure 16: Competitive comparison - 2.4 GHz 20 MHz mode, downlink
Figure 17 shows the uplink comparison, with all products maintaining their relative positions. In the interest of space, I'm not going to take up space here with the 40 MHz mode plots. Here is 40 MHz down and 40 MHz up.
Figure 17: Competitive comparison - 2.4 GHz 20 MHz mode, uplink
The 5 GHz plots are even more interesting because, as luck would have it, the client used with each product is the Linksys WPC600N! For downlink (Figure 18), the Linksys WRT600N is the clear winner and the DAP-1522 bests the DGL-4500 only at the stronger signal levels (lower path loss).
Figure 18: Competitive comparison - 2.4 GHz 20 MHz mode, downlink
Figure 19: Competitive comparison - 2.4 GHz 20 MHz mode, uplink
I think the main factor that accounts for the 1522's low comparative ranking is D-Link's choice to go with a two-antenna 2T2R design to hit the $100 price point. The other two products are three antenna 3T3R / 2T3R designs, which will have a throughput advantage.