The only thing certain about Wi-Fi is that standards are evolving almost as fast as hotspots are multiplying. The adapter you buy today will likely be outmoded in a year or two. But for a $50-$75 investment, that's not too big a problem, and there will be backward compatibility for most cards for a good while. So don't let the promise of change hold you back from joining the Wi-Fi world now.

Here's what in store for Wi-Fi in the next few years.

Stirring the Alphabet Soup

Several more letters will soon be added to the Wi-Fi alphabet, but the ones that will concern US consumers the most are 802.11i and e. 802.11i adds new encryption technologies to the 802.11 family, including Temporal Key Integrity Protocol (TKIP) and a form of Advanced Encryption System (AES).

Much of 802.11i is already available through WPA (Wi-Fi Protected Access), an interim standard promoted by the Wi-Fi Alliance. Most older 802.11b and virtually all new 802.11g devices have WPA firmware and driver upgrades available. WPA includes just the improved but not government-grade TKIP.

For full 802.11i support with AES (which the Wi-Fi Alliance will certify as WPA2) you may have to buy new hardware. If you currently have b routers and cards, and were considering upgrading to g, this is a reason to wait a bit longer. Much, but not all, of the 802.11g hardware being sold starting in early 2003 will be upgradable to 802.11i. Check with the manufacturer to be sure. Virtually all 2002 and earlier devices will need a hardware swap.

Another possible reason to wait to buy a new router is 802.11e. This new standard adds Quality of Service (QoS) features to the existing 802.11 protocols. QoS ensures that streaming audio and video data receive some priority over regular data, improving the media's smoothness and continuity. The 802.11e standard will help bring networked home entertainment and voice services (such as making phone calls over your Wi-Fi network) into the mainstream. Soon you will be able to watch video from the DVD player in the living room on any TV in the house, and stream photos, music and video from your PC to your home theater, as well as make inexpensive long-distance calls over the Internet.

The Incredible Shrinking Wi-Fi Card

While Wi-Fi standards are mushrooming, chipsets are shrinking rapidly in both size and price. Tiny Secure Digital (SD) Wi-Fi cards are already here, for use in PDAs and cell phones, using low-power chips from Broadcom and SyChip. Affordable chips like these will help make Wi-Fi ubiquitous -- in digital cameras, MP3 players, home appliances, stereo and video equipment, smart watches, and even cars.

Meanwhile, the popularity of Wi-Fi means that it is shipping as standard equipment in more and more laptops, so you won't need to buy a separate card. Intel's Centrino mobile chipset is a prime driver of this trend. AMD is following Intel's lead, partnering with Atheros to provide Wi-Fi chips for use with its Athlon 64 processors.

But built-ins will always lag a generation behind, technology-wise. If you like to stay on the bleeding edge, your next Wi-Fi card may well be an ExpressCard, the coming replacement for the venerable PC Card slot. ExpressCard slots will offer data transfer rates of up to 250MBps in both directions, compared to the relatively lethargic 132MBps PC Card standard. Laptops with Intel's Alviso chipset, needed to support the ExpressCard slot, are expected to be available in early 2005.

Phoning It Home

As happy as the Wi-Fi chip makers are about the burgeoning number of computer users and hotspots, cell phones are an even bigger target. Already many forms of Voice-over-IP (VoIP) calling are offered by major long distance companies, and all are looking to offer more Internet-based services in the near future. VoIP calls bypass expensive long-distance lines and offer huge cost savings to both consumers and businesses, although quality is not (yet) as good as traditional landline service. And Wi-Fi is a natural adjunct to VoIP.

Wi-Fi Everywhere

When Wi-Fi starts getting integrated into most cell phones, not to mention kitchen appliances and home entertainment devices, it will truly have arrived as a mass market phenomenon. That's when Metcalfe's Law, which states that the utility of a network equals the square of the number of users, will really kick in. In other words, the more people and devices connected via Wi-Fi, the more useful it will become. The telephone itself didn't become a utility until most people were hooked up.

With Wi-Fi, ubiquitous devices will enable a transition to "mesh networking," in which every Wi-Fi device is essentially an access point, able to broadcast to every other. Just like with the Internet, Wi-Fi signals will be able to hop from device to device to reach their intended destination, rather than relying on extended-range antennas. So an audio stream from your PC to your stereo may be transmitted by way of your Wi-Fi-equipped microwave and TV.

Don't let all this future talk stop you from buying Wi-Fi now, however. It will be years before all this comes to pass, and meanwhile you will be enjoying the benefits of surfing on your deck, at the airport gate, and in the local coffeeshop, not to mention the office conference room.