WIRELESS NETWORKS
Choosing between 802.11a and 802.11b
by Lisa Phifer, VP, Core Competence
02.11.2003
Rating: -4.26- (out of 5)
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Welcome to our new tip, the Wireless LAN Advisor. As part of SearchNetworking.com's Wireless LAN Info Center, site expert Lisa Phifer will be providing you with practical deployment advice for your wireless LANs. In this issue, she focuses on the differences between 802.11a and 802.11b, which to many may seem like comparing apples and oranges. Join Lisa as she analyzes the differences and what they mean to you.
Apples or oranges? To squeeze juice, most people buy oranges. For baking pies, apples are the crowd favorite. But suppose you just need a ready-to-eat fruit to keep your kids happy. Perhaps you should buy some of both. Or what about those new genetically-engineered "orpples" that artsy cafe downtown plans to serve? Hard to find at your grocer and not yet FDA-approved. Hmmm, better stick to apples and oranges right now.
Deciding whether to use 802.11a or 802.11b does feel a bit like choosing between apples and oranges. Until recently, all Wi-Fi products were based on 802.11b. Now that 802.11a products are available, how do they compare?
The 5 GHz band (802.11a) is less crowded than the 2.4 GHz band (802.11b). 802.11a avoids interference from cordless phones, microwaves, and neighbors. However, 802.11a faces regulatory issues in some countries due to legacy systems in the 5 GHz band.
The maximum rate for 802.11a (54M bits/sec.) is much faster than 802.11b (11M bits/sec.) But speed and distance are inversely related. According to Atheros, 802.11a throughput drops to 21M bits/sec. at 65 feet. However, that's still 4 times faster than 802.11b under similar conditions.
802.11a access point density is greater. To avoid channel overlap, only three 802.11b APs can have the same footprint. The 802.11a limit is 12, although many products support only eight non-overlapping channels. 802.11a also reduces co-channel interference because APs using the same channel are farther apart.
802.11b has an edge when it comes to maturity, per-station pricing, availability, and interoperability. Over 500 802.11b products have been certified by the Wi-Fi Alliance since March 2000. By mid-January 2003, just seven 802.11a products were Wi-Fi certified.
A single radio cannot support 802.11a and 802.11b simultaneously, so migrating from b to a requires hardware upgrade. Even if you're starting a new WLAN, many laptops and PDAs exist with embedded 802.11b. These "legacy" stations will be around for a while.
Residential users and small businesses should opt for 802.11b -- availability and selection are better, prices are lower, and most don't need higher density or bandwidth. Businesses with existing 802.11b should add 802.11a overlays in high-usage areas where bandwidth and density are pressing problems. 802.11a can be selectively deployed for power users that run bit-hog applications. The rest should either wait for Wi-Fi certified 802.11g, or buy dual-band products now.
Dual-band is the best of both worlds, at a premium price. Products include APs with two slots for replaceable radios, cards with two radio chips, and chipsets with two integrated radios. Dual-band APs support 802.11a and 802.11b stations simultaneously. Users with dual-band cards can associate with APs on either band. But flexibility isn't free. For example, Fry's 1/31/03 pricing for Netgear cards: 802.11b ($46), 802.11a ($69), and dual-band ($129).
According to Allied Business Intelligence, dual-band will surpass solo-802.11b sales in early 2004. Furthermore, ABI predicts that dual-band will top solo-802.11a sales almost immediately. Recent announcements support this theory. For example, Toshiba just released Satellite Pro 6100 notebooks with integrated a+b support. The Wi-Fi alliance just certified its first a+b product, the Atheros AR5001X CardBus. Once 802.11g is ratified, many expect tri-mode (a+g+b) products to rule.
Do you have comments about this article, or suggestions for Lisa to write about in future columns? Let us know!
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