As I write this in the summer of 2008, it's a difficult time to be buying wireless LAN gear. That's because we are in the middle of a technology transition, which is always an uncomfortable place to be. Of course, I'm referring to the transition from 802.11g to 802.11n.
Many people think, with the help of the marketing folks at Linksys, NETGEAR, et al., that the only sane thing to do is to buy 802.11n gear, even though it is still a draft standard that won't be finalized until sometime next year. And I admit that draft 11n is an attractive technology, if you have the problem that it is primarily designed to solve (higher throughput / increased bandwidth).
But as many unhappy buyers of draft 11n products have found, the technology isn't perfect and in many cases falls far short of delivering the Expanded Range! and HD Streaming! that is breathlessly described on product packaging.
I always try to understand my requirements and cut through marketing hype to get to what a product will really deliver before making a product purchase decision. In other words, I try to have my expectations in line with reality before clicking the Buy button or swiping my credit card. (Like most buyers, I usually end up buying a product that has more than I need "just in case", but that's another story...)
In the case of wireless LAN gear, expectations usually boil down to range and speed, with price, of course, still somewhere in the mix. So it's important to repeat here my Three Rules of Wireless Networking. Repeat after me:
With those guiding words in mind, let's start with understanding expectations.
WLAN vs. Ethernet
Let's first establish that no current WLAN technology is the equivalent of 100 Mbps Ethernet. Said another way, there is no WLAN product that you can buy today (or in the foreseeable future) that will deliver bits as quickly, consistently and reliably as good ol' Ethernet. Period. If you need more convincing, go read Draft 11n ≠ 100 Mbps Ethernet and come on back.
At the risk of driving the point into the ground, let's take another look at wired vs. wireless speed. Figure 1 is a plot of throughput over time for 100 Mbps Ethernet and one of the best-performing 11n 5 GHz products that I have tested, the NETGEAR WNHDE111 [reviewed].
Figure 1: 100 Mbps Ethernet vs. 5 GHz, 40 MHz bandwidth draft 802.11n
Note that the 100 Mbps plot is lower than 100 Mbps, due to the periodic glitches and TCP/IP overhead. But also notice that, except for the glitches, throughput doesn't vary. Now look at the variation in the lower wireless plot line. Some products that I have tested have less and others have more. But all wireless products have similar throughput variation, which results in lower average delivered throughput.
One last point and I'll stop beating this. The wireless test in Figure 1 was run under "best-case" conditions, i.e. with the transmitter and receiver within 10 feet of each other with no other RF sources or WLANs in range and no physical obstructions. If I added obstructions, increased distance or brought in RF sources, throughput would decrease. On the other hand, Ethernet speed is not affected by distance, as long as the 100 M per-segment maximum cable length is not exceeded.