Maximum Wireless Bandwidth
I've noticed that N routers sometimes can produce higher aggregate bandwidth using multiple connections vs. a single connection. So I duplicated the tests run on the E4200 and other simultaneous dual band routers, running multiple simultaneous IxChariot scripts on each radio to see how the E4200 fared.
Figure 13 shows the setup used for this and the Stress test that follows below. For testing maximum wireless bandwidth I used two notebooks, both using Intel Wi-Fi Link 5300 AGN mini-PCIe cards. The "WAN" endpoint computer shown in Figure 12 is not used in this test.
Figure 13: Max Wireless Bandwidth and Stress Test setup
The Acer Aspire 1810T notebook was used as the 5 GHz client and ran Win 7 Home Premium and Intel's Win 7 220.127.116.11 driver for the Intel card. A Dell Mini 12 running WinXP Home SP3 and using Intel's Win XP 18.104.22.168 driver served as the 2.4 GHz client. Both wireless clients were in the same room within 10 feet of the E4200, set to Auto (20 / 40 MHz) mode and with WPA2 / AES encryption enabled. The WNDR4000 was set to Channel 1, Up to 300 Mbps mode (40 MHz bandwidth) on 2.4 GHz and Channel 36, Up to 450 Mbps mode on 5 GHz.
Each wireless client was paired with a wired test "endpoint" connected via Gigabit Ethernet. One of the two wired machines ran the IxChariot console, which coordinated all endpoints for the test. I probably could have gotten by using only one wired machine, but wanted to be sure that I wouldn't run out of bandwidth or CPU.
I started by running one downlink stream on each band with a staggered start. This checks to see if there is interaction between the radios, as there is in the E4200. Figure 14, however, shows that both radios appear to be independent, since there is no effect on 2.4 GHz throughput when the 5 GHz radio starts 10 seconds into the test.
Figure 14: Simultaneous wireless bandwidth test - 1 stream each radio
I then ran four downlink streams on each radio to see how much total wireless bandwidth I could coax from the WNDR4000. Figure 15 shows I got 192 Mbps total throughput from both radios. You can see that with this many streams running, throughput was distributed fairly equally among clients and bands, but limited to around 25 Mbps per stream.
Figure 15: Simultaneous wireless bandwidth test - 4 streams each radio
So it looks like the WNDR4000 bests the E4200 in this test for both radio independence and total wireless bandwidth.
This test shows what happens when both the wireless and routing sections of the router are running full tilt. The setup is the same as shown in Figure 1, but this time I ran only one downlink stream each on the 2.4 and 5 GHz radios and added a single WAN to LAN wired stream.
Figure 16 is a run with no bandwidth limits, i.e. blasting each stream as fast as it would go. The test starts traffic on the two wireless radios first, then the WAN to LAN routing traffic. You can see the dip in wireless throughput when the routing traffic starts and a huge rise in routing throughput when the wireless traffic stops.
Figure 16: Simultaneous 2.4 and 5 GHz plus routing - full bandwidth
As I did with the E4200, I then repeated the test, but limiting the routing WAN to LAN stream to 100 Mbps, then 50 Mbps. Figure 17 shows the results with the 50 Mbps routing limit, which still shows a throughput reduction on the faster 5 GHz band stream.
Figure 17: Simultaneous 2.4 and 5 GHz plus routing - 50 Mbps WAN to LAN traffic limit
For comparison, Figure 18 shows how the E4200 did on the same test, with once again, a dip in the faster wireless stream.
Figure 18: Cisco Linksys E4200 simultaneous 2.4 and 5 GHz plus routing - 50 Mbps WAN to LAN traffic limit
This is mainly an exercise to explore the design limits of the product and it's unlikely you would see these effects in real world use. You would have to have a fast Internet connection loaded with heavy, continuous download traffic while running heavy, continuous streaming traffic on either or both wireless radios.
The bottom line is that the E4200 and WNDR4000 behave similarly when wired router and both radios are simultaneously heavily loaded.
If you're trying to decide whether the WNDR4000 is a step up from the WNDR3700v2, it's not. In 2.4 GHz, both seem evenly matched for strong to medium signal strength. But when you move to weaker signals, neither router does as well as the Linksys E4200 for consistent, mid-teen throughput.
In the 5 GHz band, the three-stream Broadcom radio doesn't give the WNDR4000 any more performance edge than it did the Linksys E4200; neither could reach into our Locations E and F. But the WNDR4000 seemed to provide a bit higher throughput in Location D than the E4200. But I can't say whether that would translate into noticeably better performance at your home.
The bottom line is that the WNDR4000 offers no advantage over the WNDR3700v2 unless you happen to have a 5 GHz three-stream capable notebook. And if you're trying to decide between a Cisco Linksys E4200 and WNDR4000, it's a toss-up on performance, but a win for the WNDR4000 if WDS repeating and bridging is something you want.