A key decision you'll need to make is whether you want a single or dual-band router. If you select an AC router, that decision is already made; you'll be buying a dual-band. If you opt an N router, you still get to make the choice. So here's what you need to know to make that decision.
G and single band N routers operate in the 2.4 GHz radio band. This is the same frequency band that many other wireless devices operate in, including some cordless phones, intercoms, baby monitors and microwave ovens. It's also where most wireless networks operate, at least in the U.S..
The more of these devices that are in range of your wireless network, the lower and less consistent your speed will be. In really crowded areas, you may find your laptop or other wireless device constantly dropping connection to your router, or speeds wildly swinging from fast to snail-slow.
The 2.4 GHz band has 11 channels (in the U.S.), each of which is 20 MHz wide. If you do the math (or look at Figure1) you'll see that only three of them (Channels 1, 6 and 11) don't overlap. Channel overlap is bad, because it's another form of interference, which reduces your wireless LAN's speed and reliability.
Although there is nothing stopping you from setting your router to any of the other channels, for best performance, use only channels 1, 6 or 11. Contrary to what you might think, using the other channels doesn't improve performance. That's because your signal looks like interference to networks on 1, 6 and 11 and vice versa.
Figure 1: 2.4 GHz band channels
Wi-Fi Hotspots: Setting Up Public Wireless Internet Access
(Cisco Press, 2006) by Eric Geier , used by permission
Dual band N and AC routers provide access to the 5 GHz band. The channels in this band are also 20 MHz wide. But because the frequency range that the band is allowed to use is greater than in 2.4 GHz, the channels can be spaced further apart and don't overlap. Figure 2 shows the complete list of channels in the 5 GHz band.
Figure 2: 5 GHz band channel list
Because some of the frequencies are shared by public safety services like police radio and radar, only channels 36, 40, 44, 48, 149, 153, 157 and 161 are used by most N or AC routers. (Some routers throw in Channel 165 for good measure.)
Because it is not as heavily used as 2.4 GHz, the primary benefit of using the 5 GHz band is lower interference. This can improve your wireless network's speed and connection reliability. The primary downside of 5 GHz is reduced range. This is because a 5 GHz signal is reduced more than a 2.4 GHz signal when passing through walls and other physical obstacles. So a router operating the the 5 GHz band may not be able to provide a usable connection in the same location that it can when switched to the 2.4 GHz band.
The 5 GHz band also has the advantage of more non-overlapping channels than 2.4 GHz. So this increases your chances of finding a channel that doesn't interfere with neighboring networks. Enjoy this advantage while it lasts, however. As more draft AC routers hit the airwaves, they will gobble up those free channels like hungry, hungry hippos.
Dual-band N and draft AC routers operate in both the 2.4 GHz and 5 GHz bands. Single-radio N models (N300, N450) make you choose one band or the other. Two-radio models (also called "simultaneous" or N600, N750, N900) allow you to support devices that connect in both bands at the same time. If you're going to go dual-band, don't cheap out. Buy a simultaneous dual-band router. Switchable single-radio dual-band routers are mainly for when you want to add a second router to upgrade your network to 5 GHz.
One more thing. Before you decide that 5 GHz will solve all your problems, you should know that many mobile devices (phones, tablets, e-readers) don't support 5 GHz operation. This will change over the next few years as new devices get fitted with single-stream AC radios, which will provide higher thoughput (at the expense of eating up 5 GHz channels - see below). Don't worry if you don't have an AC router because AC is backward compatible to N.
Those 20 and 40 MHz bandwidth modes I told you about earlier really refer to how many channels the router is simultaneously using. 20 MHz mode means it is using only one channel; 40 MHz mode means it is using two. The 80 MHz mode used by draft AC gear uses—you guessed it—four channels. So you can see Why 802.11ac Will Kill The 5 GHz Wi-Fi Band as these products come into mainstream use.
The advantage that 40 MHz mode provides is higher throughput. But because it eats up more channels, it can increase interference for nearby networks, which reduces throughput and, in extreme cases, wireless connection reliability. This is why most N routers have an "Auto 20/40" mode instead of a 40 MHz mode.
Properly designed, i.e. compliant with the IEEE 802.11 spec and with Wi-Fi Alliance Certification requirements, routers are supposed to detect any interfering networks and fall back to using 20 MHz mode. Manufacturers also have the option of not supporting 40 MHz operation in 2.4 GHz at all, which is the choice Apple has made for some of its wireless products.
There are no such limitations on 40 MHz (or 80 MHz) mode operation in 5 GHz. Which is why some manufacturers default their routers to 40 or 80 MHz mode in that band.
Throughput & Range
Wireless performance is the squishiest spec to pin down, yet usually the driving force behind the urge to buy a new router. Manufacturers are happy to have you confused, because confused consumers usually buy the product with the highest number on the box, which usually is the most expensive. That's why they use link rates and show the sum of the maximum link rates of both radios in simultaneous dual band products. But, by now, you know that number on the box is 2X to 5X greater than the best throughput you'll actually get.
What you really want in a wireless router is the best throughput vs. range. But because of the way Wi-Fi networks work, this number is highly variable. It is highly dependent on the RF (radio frequency) and physical environment that the router is operating in, as well as the capabilities of the wireless devices using the router.
That's why the wireless performance testing we do for our Charts and Rankers uses a "clean" RF environment (no other networks or devices operating), the same test locations and the same test clients. Keeping as many things constant as we can, provides the best relative comparison among products available anywhere.
To get you in the right ballpark, however, here's a table of actual measured best case downlink throughput taken from our Router Charts for many N and AC product classes. These numbers represent performance with router and client in the same room about 10 feet apart and with clients that support the maximum router link rate.
|Class||Typical maximum 2.4 GHz throughput (Mbps)
20 MHz B/W
|Typical maximum 5 GHz throughput (Mbps)
40 MHz B/W N devices
80 MHz B/W AC devices
|N300 or N600||60 - 80||60 - 80|
|N450 or N900||75 - 85||150 - 200|
|AC1200||80 - 90||200 - 300|
|AC1750||110 - 130||300 - 370|