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Wireless Reviews

Wireless Performance - 5 GHz, Two Stream

Moving up to 5 GHz, here is the Performance Table for 5 GHz, 2 streams. The ASUS takes three out of four comparisons, but is bested by both the NETGEAR and Cisco running uplink in 40 MHz bandwidth. The 66U's particularly strong showing in Location D throughput disappears in this test group, too.

The IxChariot plot for 20MHz mode downlink (Figure 14) shows well-behaved throughput—a characteristic that is carried through to the other plots. I should note that in the simultaneous up/downlink tests downlink throughput is about 2X uplink.

ASUS RT-N66U IxChariot plot summary - 5 GHz, 20 MHz mode, downlink, 2 stream
Figure 14: ASUS RT-N66U IxChariot plot summary - 5 GHz, 20 MHz mode, downlink, 2 stream

Remember that even though there are no Location F results, the two-stream client was able to remain connected to the router, albeit with an unusable connection. But what is unusable in my test location, might be perfectly fine in yours. Don't expect miracles, though!

Here are links to the other plots for your reference.

Wireless Performance - 5 GHz, Three Stream

Last, but not least is the Performance Table for 5 GHz, 3 streams. If you're looking to stream HD video, this is where you'd like to see the highest throughput. Unfortunately, the Dark Knight doesn't deliver. Oddly, it produced its highest throughput of 136 Mbps running uplink in 40 MHz bandwidth mode. Downlink performance was very disappointing in this mode (57 Mbps), with very high variation. Figure 15's view of 20 MHz mode downlink shows fairly high variation, too.

ASUS RT-N66U IxChariot plot summary - 5 GHz, 20 MHz mode, downlink, 3 stream
Figure 15: ASUS RT-N66U IxChariot plot summary - 5 GHz, 20 MHz mode, downlink, 3 stream

Here are links to the other plots for your reference.

Stress Test

When there's a top-end router on the bench, I like to push it a bit to check for interactions and limitations. So I set up my two test laptops with the three-stream N Lenovo x220i on 2.4 GHz and the Acer Aspire 1810T on 5 GHz with two streams. Both radios were set to 40 MHz bandwidth mode and both laptops were about 10 feet away from the router in the same room.

The test consisted of six test pairs running the IxChariot throughput script with TCP/IP. One pair was 2.4 GHz three-stream up/downlink, the second pair was 5 GHz 2 stream up/downlink and the last pair was wired routing LAN>WAN and WAN>LAN. I staggered the start times of the scripts and adjusted the length of each pair so that the effects of each pair could be seen. Figure 16 tells the tale.

The 2.4 GHz, 3 stream pair starts first and hums along at maximum throughput. But when the 5 GHz, 2 stream pair starts at the 20 second mark, I was surprised to see the 2.4 GHz pair throughput drop. Since each radio has its own BB/MAC processor and there is a separate CPU handling routing, this indicates a bottleneck somewhere. I'd have to guess the CPU, since it's the only thing common to both radios.

ASUS RT-N66U wireless and wired stress test
Figure 16: ASUS RT-N66U wireless and wired stress test

When the wired routing pair kicks in at the 40 second mark, both radios again lose throughput. The only exception is the 5 GHz uplink stream, which is down around 35 Mbps. When the routing pair stops at the 1 minute mark, you can see both radios' throughput jump back up.

When the 2.4 GHz pair stops, you can see the 5 GHz downlink trace reach a new high, indicating it had been held back by the 2.4 GHz radio when it started. And finally, when the 5 GHz downlink stops, the uplink test reaches its own high, which shows the downlink/uplink interaction we saw previously on the performance tests.

Note that I limited the routing pair throughput to 100 Mbps. I did this first, because I found the wireless throughput would have been even more negatively impacted if I didn't. But more on a practical basis, there aren't that many people who will be running the router at 100 Mbps up/down. I also ran a test limiting routing throughput to 50 Mbps, which showed no additional reduction of wireless throughput and with no limit.

The no-limit test pushes the 2.4 GHz pair throughput down further to 20 - 25 Mbps. But it also plays havoc with the wired routing throughput, causing high variation, as is clearly shown in the plot.

I'm surprised by the interaction of the two radios, given the architecture of the router, with its separate CPU and fully independent radio SoCs. I would expect a throughput hit, and got one, with a router like the original Cisco Linksys E4200, which uses one of the radio CPUs as the router's main CPU.

Whether you see the effects of any of this in real life will depend on how much you push the router. Remember that I'm using continuous streams with no bandwidth limits (except as noted for the router). Even a 1080p HD stream isn't going to do that, although a long local wireless filecopy could.

Closing Thoughts

As good as the RT-66U is, our wireless performance results once again show that no router is good in every mode that we test. But that said, the Dark Knight clearly outperformed both the NETGEAR WNDR4500 and Cisco Linksys E4200V2 in most of our two and three-stream tests. And it's the only router in recent memory able to reach to our worst-case/lowest-signal test location on the 5 GHz band, albeit with barely-usable throughput. Still, this is an accomplishment in itself.

If you're going to spend close to $200 for a wireless router, you should get a lot for your money. The Dark Knight seems to deliver wireless performance to justify its high price and has routing speed fast enough to handle any service a consumer is likely to have, even our friends in Europe and Asia.

But other aspects of the product are a work in progress. Documentation is poor and incomplete, with no mention of many of the product's key features like IPv6, USB Download Master, VPN server and 3G backup WAN support. And the non-functional DLNA server isn't bringing smiles to some buyer's faces. So if you decide to take the plunge, be prepared to wait for both firmware updates and better documentation to make the Dark Knight all that I'm sure ASUS wants it to be.

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