While browsing through Sunday’s newspaper ads, I saw a vendor advertising “Wireless N” with some magical, rounded integer percentages of improvement over “Wireless B.” I’ve also been reading stuff about “WiMax” and “Wi-Fi.” Since it takes an EE to spell geek, and I happen to be one, I thought I’d find out what all the numbers and letters mean. Moderate amounts of EE ahead.
First, when looking at all of these long enough, you’ll notice the funky numbers of the form 802.NNz, where “NN” is a number and “z” is an optional letter. The 802 refers to the uber-standard by the IEEE) (Institute of Electrical and Electronic Engineers) for “networks with variable packet lengths.” Think of this as “the network through which you use to read this blog” versus “your cell phone’s network.” You can read a lot more about it here.
The “NN” refers to one of several major standards while the “z” is the revision of that standard. There are over a dozen “NN” numbers, but the most interesting ones for this discussion are:
- 802.11a — The original standard, higher link rate, and on a less-crowded frequency. The problem? It doesn’t work very well indoors. The devices haven’t achieved any economy of scale, e.g., are expensive for what you get. If you’re setting up a home-based network, do not buy this.
- 802.11b — ubiquitous wireless networking. This uses a lower, “unlicensed” frequency. (The “unlicensed” translates into “easily interfered with by other things.”) It’s ubiquitous and cheap. The main drawback is the slower connection speed and interference potential.
- 802.11g — This supports the higher bandwidth (meaning you can download stuff faster) that “A” offers, but it’s backward-compatible with 802.11b. The connection speed is faster and the range is improved inside the house. It’s also relatively cheap. The problem is there is a lot of marketing pollution with G and “super-G.” “super-G” isn’t technically a standard, but if you’re using the same vendor’s base station and wireless cards, you’ll see some improvement over G. (N.B. I’m running the Netgear SuperG at home with good results.)
- 802.11n — this is the “next generation” of wireless, but the standard has not been finalized. This hasn’t stopped vendors from selling it, though. Pluses — takes some of the benefits of G and super-G. Personal advice: hold off; or consider a 802.11g/Super-G device.
e.g., the connection now provided by DSL or cable internet providers,
but in convenient wireless form. Translation: potentially much cheaper. With all the media hype (e.g., the entire country of Mauritius going wireless), you’d think this was a miracle weight loss pill. While Intel, Waveset and Fujitsu are all building chipsets for these devices, the devices are stil two years from being (choose one or more) viable/purchasable/reliable/cheap.
The original specification 802.16a, was in the upper frequency range, which meant line-of-sight. (See my comment about “802.11a” above) The current specification, 802.16d, tries to eliminate the outdoor antenna. The next revision, 802.16e, is for mobile use. (They apparently don’t get along with the 802.20 committee focused on “mobile wireless broadband. >:-)
Below is a quick and dirty comparison. Do note that the “Peak Link Rate” is a theoretical number. “Your mileage may vary, and will probably be less.” Far less.
| 802.11 — "WiFi" | 802.16 — "WiMax" |
||||||||
| A | B | G | Super G | N | D | ||||
| Peak link rate | MBPs | 54 | 11 | 54 | 108 | 100 | 75 | ||
| Frequency band | GHz | 5 | 2.4 | 2.4 | 2.4 | 2.4* | 2 – 66 | ||
| Channel BW | MHz | 20 | 25 | 20 | 2 x 20 | 1.5 – 20 | |||
| Range | meters | 50 | 100 | 100 | 200 | 50,000 | |||
| Spectral efficiency | bps/Hz | 2.7 | 0.6 | 2.7 | 5.4? | 5.4 | 5 | ||
| Modulation | OFDM | DSSS | OFDM | OFDM | OFDM? | OFDM | |||
| QoS | N | N | N | Y | Y? | Y | |||
| Applications | LAN | MAN | |||||||
| Sub carriers | 64 | 64 | 256 | ||||||
And for those who have read this far, an extra special bonus useless trivia section. “What happened to the other letters?”
802.11: c & d were for bridge conections; “e” improves quality of service. “f” ensures access points from different vendors play nicely. “h” has power control management (a concern for laptops). “i” is the security specification replacing the porous “WEP” “j” supports the Japanese 5GHz frequency. “k” has some radio resource management (hand waves). “l” was skipped because it looks too much like “i,” (but apparently not enough like “1”?). “m” was a maintenance release. There are also “p” (wireless access for vehicular environments — for the love of all that’s good, please get off the fracking network while you drive); “r” is fast roaming, “s” is wireless mesh netowkring, “t” is wireless performance prediction, “u” is internetworking with non-802 networks (like cellular — fixed-length packets and all that), and “v” is wireless network management. I don’t know what happens when they run out of letters.
And for WiMax, 802.16. The original specification was 11-66GHz, high frequency, poor line-of-sight capabilities. “a” added the 2-11GHz bands. “b” included some stuff for license-exempt frequencies. “c” exanded the system profiles or the 10-66GHz range. “d” is the current one, eliminating the external antenna. “e” is ‘handoff among basestations’ — so you can read your email in the ambulance because you didn’t stop reading email while driving (ahem), and “f” adds a management information base.
wifi net news is a good source of wifi industry news and opinions. He recommends avoiding the current wave of “pre-N” products that don’t have guarantees of being able to be upgraded to the final N standard. The cheapest pre-N stuff is from belkin, which has a pretty awful firmware upgrade record.
I wasn’t going to name companies, but I do have to wonder what they’re actually selling. Belkin is one of those companies I’ve always associated with very commoditized products like KVM boxes or cables.
BTW, about four months after we got the house wired we sold it. Now I’m in the process of wiring up the house we just bought–since it has an unfinished basement, the wiring job’s much easier than it would have been on the old house (which only had a spider-infested crawl-space). But I’m basically all 802.11b/g anyway and haven’t found it to be too terrible.
what’s your current view of WiFi “vs” WiMax? Are cities planning to deploy WiFi just wasting their time and money?
It depends on what the cities’ expectations are. WiFi-G is here, now, whereas WiMax 802.16e was just approved in December of last year. WiFi equipment is very cheap, WiMax, who knows.