Wifi Bandwidth Experiment

I had been noticing pretty poor Wifi performance with my Mecanumbot, especially when I’m trying to visualize data with rviz remotely. After a couple weeks of dealing slow performance and tethering the robot with an Ethernet cord, I finally decided to kick my Netgear WNR2000 v2 router to the curb and look for something new. I ended up with the Linksys E4200 after a quick search for “best Wifi router.” The E4200 bests my old router with simultaneous dual band support, gigabit wired ports, and the ability to upgrade the firmware to DD-WRT.

The new router arrived today, and like any good engineer, I had to test the router to see if the upgrade was really worth it. To compare the bandwidth difference between routers, I decided to use iperf between two local machines. The basic commands are iperf -s (which I ran on my desktop) and iperf -c SERVER_IPĀ (which I ran on the Mecanumbot.) This configuration downloaded data from the Mecanumbot to the desktop, similar to the scenario when using rviz. Both routers were using their default settings. Below are the results of the tests. Each number represents the average of five trials and the standard deviation between the trials.

Test WNR2000 v2 (Mb/s) E4200 (Mb/s) E4200/ER1000 (Mb/s)
wired, 10/100 95.9, 0.0
wired, 10/100/1000 942.6, 0.5
802.11g, same room 29.2, 8.0 63.9, 24.0
802.11g, different room 10.5, 0.9 28.6, 1.5 13.7, 3.4
802.11g, in-between room 25.4, 5.6

The results show that the E4200 improved performance by 2 to 3 times over the WNR2000. Along with my new router, I also purchased a Linksys brand range extender – the RE1000. I was surprised to see that this in fact reduced performance with the E4200. I actually unplugging and replugging in the RE1000 a couple of times because I didn’t believe the results. But each time the range extender was unplugged, I got better bandwidth. Looks like I’m keeping the E4200 and returning the RE1000…

In case you are curious, I also ran a set of 5 iperf tests from my Macbook with the 5Ghz 802.11n link and got an average of 55.1 Mb/s in the “different room.” Not too shabby.

Update: Turns out that range extenders decreases bandwidth by design. Multiple access points or better antennas is the only way to augment an existing router without decreasing bandwidth. More info on the Wifi Wikipedia article.

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