Compelling new voice-over-wireless-LAN products signal big changes in enterprise telecommunications. The desk phone could go the way of the phone once bolted to your kitchen wall. Companies can reduce telephone tag and increase productivity by giving users mobile handsets that are as reliable as desk phones and have features such as dual-mode operation (cellular and Wi-Fi), presence and location. Dual-mode operation promises one phone with one number and one voice mailbox that works everywhere.

Fixed-mobile convergence has been touted for years. At times it sounds more like science fiction than practical business solution. There is, nonetheless, reason to take another look. The key components finally are coming together: VoIP, Wi-Fi handsets, WLANs designed to handle voice traffic, and core network solutions for seamlessly handing off calls and data sessions between WLANs and mobile networks.

Putting enterprise phone traffic over WLANs is no trivial task. The WLAN is expected to assume the job of existing PBX wiring while continuing to handle data traffic without degrading performance or compromising security.

The WLAN industry has prepared for this opportunity by developing media access control (MAC) layer protocol enhancements to minimize latency and improve battery performance - specifically, the 802.11e QoS and Wi-Fi Multimedia standards.

There are bigger quality issues, however. Users want wireless handsets that work everywhere within the enterprise and are as secure and reliable as desk phones. This requires more than MAC-layer protocol enhancements. Wireless notebook users might tolerate dead spots in corridors, elevators and stairwells, but wireless phone users might not. The first thing a firm implementing a VoWi-Fi must do is ensure complete coverage.

Though the typical voice call uses much less bandwidth than the typical data session, companies must ensure that the vast majority of calls go through on the first try; latency does not exceed specified limits; handoffs between access points are transparent and reliable; and calls are seldom dropped. There must be enough capacity to handle voice and data traffic, and this capacity must be properly distributed and managed.

Companies also must take care that voice traffic does not create security vulnerabilities. Call setup, handoff and teardown create opportunities for rogue users to sneak through. The WLAN must recognize and closely track each call, taking the proper security precautions at each stage of the call process.