Wireless networks: like VCR clocks, but 10x worse

A few months ago, I joined a team that builds software for wireless routers at Google. Some time after that, I found that I’d started noticing how well my laptop’s wireless connection was working even when I wasn’t deliberately trying to.

I recently went home for vacation for the first time since then, to visit my lovely family and their ISP-provided router in the basement. I haven’t regretted the visit, but I definitely regretted paying attention to the wireless network. It dropped constantly, and after a while of this I asked if I was the only one it was working badly for. I wasn’t; they’d just been putting up with the malfunctions and hadn’t thought to say anything.

Investigating the slowness

Being in the basement might have contributed to the problems, but the router was there for a reason. The house had come pre-wired with Category 5 cable, and the builders collected them into a bundle and dropped them in the center of the basement. When we got FiOS, the installer simply ran cable to to where all of the existing cables were. Moving the router would have required moving all of this, which was beyond our ability to do.

A quick scan with the airport command showed that there were other networks using the same channels as ours. Additionaly, every visible network was on a 2.4 GHz channel, and none were on 5 GHz channels. Installing an access point that could serve a network on a 5 GHz channel - the ISP router couldn’t - would likely solve the network problems, and I offered two ways to do this:

Knowing that they could use the network backup features of an Airport Extreme, I suggested the latter.

Connecting the home network

There were more cables bundled at the router than there were ports on the router to connect to, and no room near the router to install additional equipment; the router took up the only shelf-like space available.

So we made more room. I bought some brackets from Home Depot and my Dad and I installed a shelf that extended the space next to the router. Then I installed a switch on the shelf, and I connected all the rooms in the house to it.

(Except for one. There’s one Cat 5 cable where we never did locate the other end of it, and we left it unterminated and lying on the floor. Best not to connect cables to your network when you don’t know where they lead.)

Setting up the AirPort Extreme

The first location we tried for the AirPort Extreme was a guest bedroom. I unboxed the router, connected it to the network, and asked my sister Sam to set it up from her computer. It figured out that it was behind another router and defaulted into bridge mode, and was serving a wireless network within 15 minutes of being turned on.

We turned off the wireless network from the ISP router, which there didn’t seem to be much reason to join anymore, and started testing.

But wait, there’s more

My sister ran a speed test from her laptop next to the router, and got terrible speeds - 17 Mbps down, and only slightly faster up. I tried again from further away and get 40 Mbps both directions.

Option-clicking the wireless Menu Extra showed that my laptop was on

Channel: 132 (DFS, 5 GHz, 40 MHz)

which seemed great - we were the only 5 GHz network that showed up in a scan. Watching a bit longer showed that the noise would periodically spike above the RSSI, even close by, and the laptop would eventually give up and switch to channel 6. And then the AirPort Extreme was just as slow as the ISP router.


DFS stands for “dynamic frequency selection”; it means that the wireless channel may be shared with radar, and the router must watch for radar and stop transmitting if it is detected. The technical details are out there if you’re interested.

Our home is near a municipal airport, and my guess is that this is due to radar that shares these channels. Trying to explain this to my family quickly turned into an Abbot and Costello sketch:

Me: So the radar from the airport is interfering with the network from the AirPort…

Dad: Huh?

and then they went to bed shortly after.

Getting to fast

I thought about this for a bit, and realized that this could likely be worked around by changing the wireless network channel to 149, which isn’t shared with radar. By this point it was almost 1:00 AM.

I didn’t make the change right away though. Wireless network problems often only show up when people around you are using the network too, which means they have a day-night cycle that follows the day-night cycle where you are. It’s early enough, and pronounced enough, here that even the balky DFS channel from earlier was working without apparent difficulty.

I went to bed instead, too.

In the morning, I asked my sister to change the channel to 149 and then let me know if the performance problems persisted. They didn’t; she reported that it had noticeably improved over the old router. I stopped noticing drops too, and as best I can tell the issues have been completely resolved.

The take-aways

Wireless networks are hard. And Scott Hanselman’s “WARNING TO THOSE GEEKS IN RELATIONSHIPS” (in the middle of this post) applies to familial relationships as well as romantic ones.

Nevertheless, I think they’re keeping the AirPort Extreme.