Net Waves: Voice Over Wi-Fi: Are You Prepared?

I strongly believe, however, that voice over Wi-Fi will become thekiller wireless LAN application that we've been waiting for. Myconsulting firm, Wireless-Nets, has seen a widespread trend towardcreating voice over Wi-Fi products, and many companies that aredeploying wireless LANs also have an eye on voice.

Several Wi-Fi-enabled telephones are on the market now, includingSpectralink's NetLink e340 and Cisco's Wireless IP Phone 7920.Traditional wireless LAN infrastructure players Cisco and Proxim haveworthy hardware for voice solutions, and startups such as Meru Networkshave well-designed access points that enhance voice over Wi-Ficonnectivity. Non-traditional service providers like Vonage are evenoffering voice over Wi-Fi service plans for nationwide calling that aremuch less expensive than cell phones.

The Federal Communications Commission has spoken, ruling last month thatVoIP (voice over IP) services are interstate in nature and not subjectto traditional state public utility regulation. For example, Vonage isavoiding the Minnesota Public Utility Commission's efforts to treat itsservice as traditional phone company service. While the FCC will furtherdecide what regulations apply to Internet telephony over the next year,it seems at this point that regulation will stay out of the way.

Some of my clients are currently deploying voice over Wi-Fi solutions,and the majority of the remaining ones are planning to do so in thefuture. The benefits of voice over Wi-Fi in enterprises yieldsubstantial returns on investment because mobile telephone usage isenabled within facilities and because combining telephone and datanetworks lowers costs. The returns are just too substantial to resist.This leads to the bad news. Most existing wireless LANs installationswill not adequately support voice over Wi-Fi applications mainly because802.11 wireless LANs were meant to support data, not voice. Many ofthese networks definitely don't meet Cisco's guidelines for deploying wireless VoIP phones.

When performing onsite testing, I often find wireless LANs with lots ofcoverage holes throughout the facility, low signal strength instaircases and hallways where phones will likely operate, sloppy RFchannel assignments, and access point handoffs that are too slow. Wi-Fiphone usage on these networks is generally full of crackles and pops,with frequent dropped calls as users roam about the facility.

In addition, QoS (quality of service) is lacking in most existingwireless LAN installations. In fact, I feel that limited QoS is theprincipal obstacle to deploying effective voice over Wi-Fi solutionstoday. QoS is available, but sifting through the alternatives iscomplex, and the solutions are proprietary. Several flavors ofproprietary QoS are available, but SpectraLink's SVP (SpectraLink VoicePriority) is currently an unofficial industry standard and isimplemented in most enterprise-grade access points. Hopefully, 802.11ewill become available within the year to help solidify a common methodfor QoS to make voice (and video) communications better over wirelessLANs.

Redesigns of existing wireless LAN installations are necessary to offerthe optimum blend of antenna types and access point configurations,along with possibly replacing access points with ones that offer fasterroaming. Most existing wireless LANs today are 802.11b. Through testing,I've found them to only support up to a half dozen simultaneous phonescalls. This isn't good enough for a dense population of phone users whowill likely be present even in smaller offices.

If you're an enterprise considering the installation of a new wirelessLAN, determine early in the project whether you'll be supporting voiceover Wi-Fi now or in the future. Most likely, you'll be moving in thedirection of voice, which will definitely impact your selection ofwireless infrastructure. So be sure to review infrastructure designswith an emphasis on meeting requirements for voice.For example, consider deploying an infrastructure that effectivelysupports an 802.11a network overlaid on an 802.11b/g system. 802.11a hasmuch more capacity for supporting simultaneous voice calls and itdoesn't interfere with an 802.11b network dedicated to carrying datatraffic. This gives merit to those multislot access points from vendorssuch as Cisco and Proxim. You can start with 802.11b/g today, and add802.11a in the future when you get around to deploying voiceapplications.

Jim Geier is the principal of Wireless-Nets Ltd., a consulting firm assisting companies with the implementation of wireless mobile solutions and training. Read more analysis from Jim on his Wireless LAN Blog. Contact him at [email protected].