WLANs have quickly become a fixture throughout households and enterprises. At the same time, companies have started adopting Voice over IP technology in order to lower calling expenses. The next stage integrates these two technologies to form an exciting application — Wireless VoIP. In this application, voice is carried over the WLAN network using standard VoIP protocols like SIP.

Wireless VoIP works with both 802.11a and 802.11b networks. 802.11b can support just three uncompressed audio streams, which means you’ll need to use compression in order to support more simultaneous calls. 802.11a can support four times the voice traffic. As an emerging standard for Quality of Service on WLAN, 802.11e should greatly improve call and service quality.

Wireless VoIP offers several compelling advantages. First, it significantly reduces calling costs, especially “on net” calls. In a campus environment, hospital, or warehouse, individuals can call one another without having to go through the cellular network. It’s like making intra-office telephone calls without being tied to your office. Second, wireless VoIP offers higher-bandwidth data transfer rates than cellular service. WLAN networks are much easier and cheaper to deploy than installing a cell tower.

Even with its advantages, VoWLAN won’t replace the cell phone any time soon. Industry experts view the two as complementary technologies and dual-mode cellular/VoWLAN phones are gaining in popularity. With these phones, you can use WLAN when you’re on the premises (either in the office building, at home, or in the warehouse) and then switch to cellular when you leave.

Wireless VoIP will have the greatest impact on the mobile workforce, where employees must be in constant contact while moving around; this group includes healthcare workers, retail staff, shipping and warehouse workers, and hotel staff. This new application will be particularly useful in healthcare environments, since hospitals prohibit cell phone use due to RF interference. Most of the large warehouse retail chains have already deployed WLAN. By adding VoWLAN (and with “push-to-talk” technology), retail staff can instantly check pricing and inventory. Truck loaders and warehouse staff can be in constant contact, facilitating real-time inventory management.

Wireless VoIP devices can range from WiFi handsets to dual-mode cellular phones, or PDAs with voice capability. Industrial-grade PDAs are also available that can withstand rugged environments like warehouses and loading docks.

As promising as the technology is (and researchers predict big numbers for VoWLAN), there are still a few obstacles to overcome before VoWLAN goes mainstream. First and foremost is call quality. In 2005, the publication Network World conducted a test on various wireless VoIP solutions. They found that products delivered toll-quality voice, but only with voice traffic alone. As soon as data traffic was added to the mix, calls were dropped and sound quality was poor.

Other challenges include security and call hand-off. Since wireless VoIP calls are carried over WLAN, they can be subject to the same vulnerabilities as WiFi. In addition, the infrastructure is not there yet to support roaming between VoWLAN and cellular networks. If you place a call in the office using a WiFi-enabled handset, you can’t expect the call to stay up as you travel outside the WLAN.

See also:

• Digital Adapters
• Fax
• IP Phones
• Service Providers

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