Wireless LAN-enabled mobile phones and handhelds are on the way, whether network administrators are ready for them or not.

ABI Research raised its forecast for this year's shipments of wireless handsets in a new report, and predicted that Wi-Fi enabled phones are about to swamp the market, creating fresh complications for enterprises managing wireless LANs.

A "somewhat more bullish economy" and the emergence of niche-oriented consumer handsets like Nokia's N-Gage are helping to create demand for next-generation wireless gadgets, ABI said. But the most significant trend for enterprises is the arrival of Wi-Fi phones from the likes of Motorola, HP and NEC, as well as a more general boom in Wi-Fi-enabled, data-oriented handhelds. These devices will see a huge increase in data and VoIP traffic on enterprise WLANs, ABI said - they will soon amount to double the number of Wi-Fi networking chipsets, such as those found in laptops.

"Starting this year, and gaining momentum over the next two years, Wi-Fi-capable phones will ship in large and growing numbers," said Philip Solis, ABI Research's senior analyst for wireless connectivity. "The number of embedded Wi-Fi ICs sold will surpass that of Wi-Fi networking chipsets by 2006, and is forecast to account for more than twice as many units shipped by 2007."

The proliferation of Wi-Fi data devices poses security questions for system administrators, according to industry experts - the cheapness of access points and the fact that WLAN chipsets are now found in most business laptops means that unauthorised WLAN usage is now a fact of life in businesses. The increase in Wi-Fi devices is likely to increase the need for security equipment designed to monitor and lock down wireless networks. Last week, Engim and Airmagnet launched what they call the first access point reference design with a built-in security sensor; the device could show up in other vendors' Wi-Fi systems next year.

Wireless VoIP poses other problems; it means increased numbers of users with less predictable roaming patterns, placing more capacity demands on the Wi-Fi infrastructure, experts say. For some businesses it may be necessary to bring in a higher-density WLAN with the ability to distinguish between voice and data traffic and manage the quality-of-service issues associated with VoIP, industry analysts say.

(For more on security and QoS issues, see the Techworld feature: "WLAN Hurdles".)

Motorola, HP, NEC and others are currently targeting Wi-Fi mobile phones mainly at enterprises. Motorola has handsets such as the clamshell CN620 and the MPx on the way, which Motorola promises will be able to switch seamlessly between VoIP and cellular networks while a call is in progress. HP is selling handsets such as the 6315 iPaq with VoIP and cellular capabilities. In Japan, NEC is shipping a Linux-based model called the N900iL that combines Wi-Fi and 3G.