Wondering about Wi-Fi? 802.11b, 802.11a, and 802.11g--which one is right for you?

FOR MOST SMALL BUSINESSES or lone wolf telecommuters, the benefits of wireless networking are seductive. Take your network with you, check your e-mail at the airport while you wait for that delayed flight, and tap into your company network from your hotel room. Back at the office, free your life from the tyranny of cabling. Connect as easily from the conference room or ware house as you do from your desk. It's a no-brainer: We want it, and we want it now.

The cost is surprisingly reasonable, too. Wi-Fi products have rapidly matured, and a wealth of high-quality equipment is available in all ranges of price and capability. For as little as a few hundred dollars, you can take a small network wireless. But (there's always a catch), in this vigorous and dynamic market, how do you choose from the galaxy of products? Your first step is to choose among the three most popular Wi-Fi standards: 802.11b, 802.11a, and 802.11g. Here's your guide to making sense of Wi-Fi standards.

The Goldilocks analysis

Folklore instructs us that Goldilocks was a fastidious girl when it came to scalability. Like Goldy, the choices with which you're faced in establishing a Wi-Fi network have a lot to do with how much capacity you need: How many users will connect simultaneously? Over how large an area? How much data traffic will the aggregate generate? What other RF devices operate nearby?

Users connect to your WLAN through small radio devices called wireless access points. The key decision you face in building a wireless network is choosing the type best suited to your needs and budget. To reap the greatest benefits with the least investment, start planning your wireless network by comparing your requirements to the capabilities of existing access point standards. Read on for a brief account of each, along with their strengths and weaknesses.

The Wi-Fi standards

For starters, I'll define the term "Wi-Fi." IEEE number 802.11 identifies standards that make up the family of wireless networking technologies with which you're concerned. The 802.11 standards acquired the nickname Wi-Fi, a contraction of "Wireless Fidelity," for two reasons. First, "802.11" lacks a certain lyrical insouciance, and second, the Wi-Fi Alliance wanted to help make 802.11 is a strong, definitive standard. Any device labeled as Wi-Fi-compliant will work seamlessly and interoperably with any other device so labeled. The take-away is that Wi-Fi isn't a loosely applied term, but instead a guarantee of compatibility.

There are lots of wireless solutions that aren't Wi-Fi-compliant, and they vary in price. Some of the least expensive gear, marketed to home and small office users, is non-standard. On the other hand, many expensive, enterprise-grade solutions are also proprietary. My point is that you can't use price as a guide.

The interoperability of your equipment is paramount. It's important to understand that today there are three generations of the Wi-Fi standard. Although devices of a specific generation are compatible (meaning their signals don't conflict), they aren't always able to "talk" to each other.

Wi-Fi 802.11b

The most widely deployed Wi-Fi equipment falls under the 802.11b standard. These devices have a maximum theoretical data throughput of 11Mbps, operate in the 2.4GHz range, can usually host between 20 and 30 simultaneous users per access point, and broadcast on three non-overlapping channels.

Actual data throughput is something on the order of 4.5Mbps. This rate is high enough to support most networked applications and file transfers. To date, there are more than 30 million 802.11b devices deployed. Of all the Wi-Fi standards, this one is the most mature, the least expensive, and for many people, an obvious choice. Because 802.11b operates at a lower frequency than other Wi-Fi devices, it has the greatest range. It works over distances of about 500 meters in open environments and penetrates obstacles such as walls and floors better than 802.11a. In addition, low-frequency operation means it drains batteries of laptops and other client devices more slowly than higher-frequency devices.

802.11b networks are protected from eavesdropping by the Wired Equivalent Privacy (WEP) mechanism. 802.11b WEP encryption depends on 40- or 104-bit shared key cryptography. Many think WEP offers a rather weak form of encryption, but it isn't the encryption that's weak. In fact, WEP uses the same cipher used by SSL (HTTPS Web sites). The problem is that WEP improperly implements the encryption, exposing it to a range of attacks.

Wi-Fi 802.11a

The 802.11a devices have a maximum theoretical data throughput of 54Mbps, operate in the 5GHz frequency range, can usually host between 50 and 65 simultaneous users, and broadcast on 12 non-overlapping channels. Actual data throughput is somewhere around 27Mbps, but some products offer a proprietary "turbo" mode that substantially increases this rate.

Although introduced at the same time as 802.11b, 802.11a has caught on slowly However, the market is beginning to adopt it and prices for 802.11a equipment are dropping. For more information on 802.11a's adoption in the marketplace, see the ADVISOR ANSWERS column on page 12 of this issue.

Although, still more expensive than 802.11b, in situations where there is heavy, localized demand, 802.11a might be the better bargain because of its high throughput and larger number of available channels. In addition, the fact that it operates in the 5GHz range makes 802.11a much less susceptible to radio interference than 80211b, which shares the 2.4GHz frequency range with microwaves, baby monitors, Bluetooth devices, and other consumer gadgets. There are disadvantages to high-frequency operation, however. 802.11 a operates over much smaller distances, isn't good at penetrating obstructions, and quickly drains batteries of connecting devices.

Some 802.11a devices use an improved but proprietary form of WEE featuring 152-bit encryption keys.

Coming soon: Wi-Fi 802.11g

The 802.11g specification is an extension of 802.11b, due to be formally ratified by the IEEE in May 2003. Early devices are already on the market, but the dust hasn't settled on the IEEE specs so the manufacturers are only making good guesses at what the standard will require. When the standard is finally published, these products are likely to need a field update of firmware to be certified as Wi-Fi compliant.

Functionally, 802.11g is the same as 802.11b, except it offers theoretical maximum throughput of up to 54Mbps. Actual throughput is about three to five times that of 802.11b in the same application. 802.11g devices are backward-compatible with 802.11b, although combining the two might result in a performance hit. However, once the standard is final, these performance problems should disappear, making 802.11g useful for improving throughput while preserving your investment in 802.11b equipment.

Spot the standard

Some of the best things about Wi-Fi are its flexibility and low cost of entry. This complicates shopping a bit because, except for the simplest scenarios, there are probably several Wi-Fi strategies that could work well for a given situation. Table 1 will help you compare your requirements to the features of the various Wi-Fi access points and give you a ballpark idea of what to expect in terms of cost.

Wi-Fi Alliance has a certification program to help consumers make sure they're buying 802.11-compliant products. Wi-Fi CERTIFIED has become the global symbol for interoperability between wireless LAN products from different vendors (figure 1).

[FIGURE 1 OMITTED]

"Any organization can make multiple products work together if they're based on a single silicon solution and a set of drivers," says Sarosh Vesuna, Wi-Fi Alliance technical committee chairman. "However, it's much more complex to certify for the interoperability of products based on several independently developed silicon solutions--the way customers in the enterprise and home use Wi-Fi-based wireless LANs in the real world. Achieving interoperability between different vendors' products requires a rigorous testing protocol. Only products that have passed this testing program are allowed to display the Wi-Fi CERTIFIED logo."

The Wi-Fi Alliance has announced the first round of 5GHz IEEE 802.11a-based products to pass its rigorous Wi-Fi interoperability certification testing. At the time this article went to press, it had only certified one dual-band (802.11b and 802.11a) product, the Atheros AR5001 X CardBus Reference Design Board/AR5BCB-00022A.

Keeping your options open

I'll bet you're trying to decide whether to build your wireless network around 802.11a or 802.11b, right? Well, relax. You can have both, thanks to dual-band access point technology. Dual-band access points provide 802.11a and 802.11b access in a single device. This pairing gives a WLAN maximum range, throughput, and user capacity from a single access point.

Dual-band technology is seeing aggressive adoption, making prices competitive with 802.11 a gear, and combines the advantages of both technologies in one unit. Dual-band access points are the obvious choice when maximum connection density is required or when you need to support both types of wireless networks in close proximity to one another. If you can wait, you'll start to see a/g chipsets; but, if you need something now, your choice is a/b.

MOBILE BUSINESS BENEFITS

When designing a wireless network, one of the first (and most Important) decisions you'll face is which Wi-Fi standard to use: 802.11b, 802.11a, 802.11g, or some combination of standards. Your choice will determine the capacity, speed, and range of your wireless network.

Table 1: Wi-Fi access point shopper's guide--Each standard
offers its own pros and cons.

DEVICE TYPE       BEST USES                   ADVANTAGES

802.11b access    Use where range is a key    * Low-cost
points            factor. Data throughput     * Mature, widely
                  demands are reasonably        deployed solution
                  modest, so it's best to     * Greatest range
                  use for networks that       * Low power consumption
                  aren't expected to grow       improves client
                  quickly. Good for             battery life
                  standard office appli-      * Interoperates with
                  cations such as print         dual-band and 802.11g
                  sharing and low-bandwidth     devices
                  jobs such as e-mail.

802.11a access    Use for bandwidth-intense   * Resistant to radio
points            applications like real-       interference
                  time data collection,       * Highest wireless data
                  telemetry, or video. For      throughput
                  high connection density
                  areas, and for applica-
                  tions where improved data
                  privacy is needed. Also a
                  good option when radio
                  interference makes
                  802.11B unreliable.

Dual-band (a/b)   Use when you require        * Highest connection
access points     maximum connection            density
                  density and where both      * Large number of
                  802.11a and 802.11b           channels reduces
                  infrastructures co-exist.     chances of
                  Dual band lets you            interference
                  combine maximum connec-     * Ease of administration
                  tion range and maximum
                  throughput in one access
                  point.

802.11g access    Use with existing 802.11b   * Costs less than
points            networks to improve           802.11a or dual-band
                  throughput. Also a good       solutions
                  option when you require     * Offers long-range
                  high data transfer rates      operation and three to
                  and long-range operation.     five times the data
                                                transfer rate of
                                                802.11b
                                              * Preserves existing
                                                investment in 802.11b
                                                networks

DEVICE TYPE       DISADVANTAGES                           PRICE POINTS

802.11b access    * Doesn't support high connection       $60-$150
points              densities or high-volume data
                    transfer as well as other options
                  * May be disrupted by devices
                    operating in the 2.4GHz range
                  * Weak privacy protection might
                    be inappropriate for sensitive data

802.11a access    * More costly than 802.11b              $250-$400
points            * High-frequency operation tends
                    to drain client batteries quickly
                  * Operates over relatively short
                    distances
                  * Doesn't effectively penetrate
                    obstructions

Dual-band (a/b)   * More costly than some single-band     $200-$300
access points       options

802.11g access    * Although the two standards don't      $120-$150
points              interfere with each other, 802.11g
                    and 802.11a do not interoperate
                  * Standard isn't set
                  * Combining with b networks can slow
                    speed

Nancy Nicolaisen is a software engineering consultant, trainer, and author of a new book, Making Win32 Applications Mobile: Porting to Windows CE, published by John Wiley & Sons. Her firm. N2 Software Engineering, recently released FieldTrip, a forms-based data collection program for handheld computers, http://www.fieldtrip2go.com.