The ABGs of wireless LANs

Dual-mode chipsets could spell relief for network execs grappling with long-term migration issues.

First came 802.11b wireless LAN devices a couple of years ago. Then 802.11a gear hit the market this year. And 802.11g products are slated to ship next year. As if that isn't confusing enough, 802.11b and 802.11a are incompatible, while 802.11g will be compatible with 802.11b, but not 802.11a. So let's sort it all out.

The IEEE's 802.11g standard is designed as a higher-bandwidth - 54M bit/sec - successor to the popular 802.11b, or Wi-Fi standard, which tops out at 11M bit/sec. An 802.11g access point will support 802.11b and 802.11g clients. Similarly, a laptop with an 802.11g card will be able to access existing 802.11b access points as well as new 802.11g access points.

However, products based on the 802.11g standard won't be available until at least mid-2003. And if you're looking for a higher-speed alternative to 802.11b, 802.11a products are out now and offer top speeds of 54M bit/sec. The main drawback with 802.11a is a lack of interoperability with 802.11b devices as well as 802.11a's network interface cards (NIC) costing 50% more and its access points being priced 35% more than their 802.11b counterparts.

This alphabet soup of wireless LAN standards doesn't make it easy for network executives to develop a long-term strategy.

But new multimode chipsets could result in the interoperability and migration issues melting away because next-generation devices will be able to handle any standard you decide to use.

Let it B

So far, enterprise IT managers have opted overwhelmingly for 802.11b, says Greg Collins, director of the Dell'Oro Group. Very little 802.11a gear has been installed since it became available in quantity in the third quarter of 2001, mainly in low-end small office/home office-type applications, Collins says.

One factor in 802.11b's favor is that it was introduced in 1999 and is now in its fourth or fifth generation. It has had most of the kinks worked out and has come down to near-commodity pricing. Plus, its 1M to 6M bit/sec throughput is adequate for a range of applications.

There were 15 million 802.11b radios in use by the end of 2001, according to Jim Zyren, director of strategic marketing for 802.11 chip manufacturer Intersil. Almost all wireless LANs in public places, such as airports, hotels and coffee shops, are based on 802.11b.

Interoperability action plan
Technology tussle
802.11 insecurity

If you already have 802.11b or are considering adopting it, your high-speed migration plan would be to wait until mid to late-2003, when 802.11g devices come out. By then, some multivendor interoperability testing should have been completed under the auspices of Wireless Ethernet Compatibility Alliance (WECA).

What up, G?

Other than ease of migration, there are three main reasons to wait for 802.11g rather than opt for the immediate gratification of 802.11a: lower power consumption, longer range and better penetration.

Also, 802.11g may offer cost advantages because lower-frequency devices are easier to manufacture. These same advantages apply to 802.11b today, which runs at 2.4GHz as opposed to 802.11a, which runs at 5GHz. So theoretically, 802.11g incorporates most of the good qualities of the other two standards (see graphic).

Eventually the pricing gap between 802.11b and 802.11a will narrow. Rich Redelfs, CEO of Atheros, currently the only chip maker shipping 802.11a chipsets, says 802.11a chips will be close to 802.11b in price "before long."

Another choice emerging in advance of 802.11g is multimode products that support 802.11a and 802.11b. These will be available in the third quarter this year. Multimode 802.11 a/g (which by definition includes 802.11b) will follow, probably in mid-2003. Redelfs also predicts that dual 80211.a/g chipsets won't cost much more than 802.11a-only chipsets.

A/B > A + B

Arguments in favor of dual 802.11a/b or 802.11a/g NICs and access points are clear -- dual clients can "tune in" to whatever network happens to be available in a particular area.

Envara, LinCom Wireless and Synad have announced dual-mode a/b chipsets. Atheros and Intersil plan to produce chipsets with 802.11a, 802.11b and "802.11g-like"capabilities. Although multimode chipsets could be used in access points, they are primarily for client cards, where space is limited and cost considerations often paramount, Redelfs says.

Cisco, Intel and Proxim are vendors leading the charge to dual-mode products:

Cisco's Aironet 1200 Series Dual Radio wireless LAN access point supports only 802.11b. In August, Cisco is expected to ship an 802.11a module for the Aironet 1200. The company says it will offer dual client cards, although no timing has been announced. While Cisco hasn't announced any 802.11g products, its support of 802.11g is strong. For instance, Cisco and Intersil said that they would cooperate to create an 802.11g reference platform.

According to the Synergy Research Group, Cisco held 18% of the total and 37% of the enterprise wireless LAN market at the end of last year, making it the top vendor in the field. The total wireless LAN market was $2.4 billion in 2002, projected to grow to $4.9 billion by 2006, according to Synergy.

Proxim's product line is currently 802.11a-only. Although Proxim has not officially announced dual products, Lynn Lucas, director of marketing, says the company will have dual 802.11a/802.11b client cards this year. Proxim sees separate 802.11a and 802.11b access points as a more cost-effective approach than dual-mode access points.

Intel has promised an optional kit to add 802.11b capability to the 802.11a-only Pro/Wireless LAN Access Point. There's currently no time frame for releasing the kit.

And Texas Instruments is working on combined 802.11a and 802.11g products, says Bill Carney, director of business development and marketing for TI's wireless network business unit, and plans to release them in 2003. TI was a major player in developing the 802.11g standard, even though it suffered a setback when its favored modulation method (Packet Binary Convolutional Code) was made an option rather than a requirement.

Chipset challenges

The IEEE 802.11a committee has made sure that 802.11a products and 802.11b products can be built largely from the same components, excluding the radios (which operate on different frequencies). This facilitates the manufacture of dual-band 802.11a/802.11b products.

From the a chipset maker's point of view, once you implement 802.11a and 802.11b in a chipset, it is virtually "free" to implement 802.11g. Thus, instead of dual 802.11a/802.11b, chip makers Intersil and Atheros are talking about dual 802.11a/802.11g chipsets.

There could be 802.11g-only chipsets, which could be less expensive than 802.11a-only or multimode chips, because they wouldn't need a 5-GHz radio, Collins says.

"It is hard to tell what impact 802.11g will have on a stand-alone basis," Collins says. What is clear, he says, is that "multimode solutions in [802.11b, .802.11a or 802.11g] will gain the lion's share in the not too distant future."

A vs. B vs. G
Here’s how the three wireless LAN standards stack up against each other.

Standard 802.11a 802.11b 802.11g

Number of channels X

Interference X

Bandwidth X X

Power consumption X X

Range/ penetration X X

Upgrade/ compatability X

Price X X

X indicates superior technology or feature.

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Dual-band downsides

There are some technical issues with dual-band devices:

If the 802.11b or 802.11g component of an access point has a significantly longer range or better penetration than the 802.11a component, network design becomes more complicated. You might need a number of dual-mode access points and a number of 802.11a-only access points to provide gap-free coverage for both technologies.

On the client side, it remains to be seen how smoothly clients can transition from one band to the other.

Seamless roaming might be quite a technical challenge for equipment designers, says Yang Minshin, director of technical marketing for Symbol Technologies, a vendor of wireless data-management systems. However, this is mainly an issue for applications such as voice over IP, where retransmission is not an acceptable solution to data loss.

The ABGs of wireless LANs

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