Voicing Concerns Over Wireless

The idea of extending Wi-Fi beyond traditional mobile data applications to support telephony continues to capture the attention of vendors and enterprises. We have concerns regarding the maturity of voice over IP over 802.
Written by Chris Kozup, Contributor

The idea of extending Wi-Fi beyond traditional mobile data applications to support telephony continues to capture the attention of vendors and enterprises. We have concerns regarding the maturity of voice over IP over 802.11 wireless networks; users must proceed with caution.

META Trend: During 2003, campus-LAN initiatives that focus on increasing network availability will receive priority over emerging applications (e.g., VoIP). However, network intelligence will enable convergence of voice, video, and data, while increasing the ease of wireless LAN deployments. By YE03, wireless LAN standards will converge into dual band, with enterprises relying more on wireless technologies to cut costs and increase productivity. By 2H04, wireless LAN security will be standards-based and interoperable, as market focus shifts to management and service ubiquity across wired and wireless networks.

Despite a down economy, the attractiveness of Wi-Fi has resulted in greater innovation and investment in additional uses for the technology. One of the major investment areas centers on the use of Wi-Fi as transport for voice - a square departure from incumbent data-centric applications previously touted by vendors and users. Enterprises are increasingly aware of the benefits that mobility can bring in improving employee productivity. The enterprise voice infrastructure is seen by many as the next logical extension of these benefits. Although wireless extensions to the private branch exchange (PBX) have existed for some time (e.g., Nortel Companion, DECT), actual deployment has been bleak due to the expense and complexity of implementation. However, the popularity of Wi-Fi and the belief by most enterprises that Wi-Fi access will eventually become pervasive within the building are driving IT organizations to explore the possibility of converging voice and data across the wireless LAN (WLAN). Unlike cellular voice, voice over Wi-Fi is reliant on a private infrastructure of 802.11 clients and access points as well as enterprise-owned call-processing capabilities. Numerous vendors have started developing products to enable voice over Wi-Fi. Users should carefully assess the maturity of these solutions to determine the appropriate uses.

Although cellular technologies can meet the requirements of the extended workforce, in-building requirements are poorly met by incumbent cellular offerings due to coverage issues and prohibitive costs. Wi-Fi has emerged as a competitive offering to more proprietary in-building systems (e.g., cellular extension, 900MHz, DECT), and the ability to IP-enable communications paints an attractive picture of enhanced features and integration into the emerging IP telephony infrastructure. However, unlike cellular technology, Wi-Fi is designed for data transport, and the desire to support voice presents significant challenges and requires much re-engineering to provide adequate service levels to ensure a high level of voice quality. Despite some initial proprietary solutions to enhance the quality-of-service level offered across the WLAN, a standard defined by IEEE Task Group E will not be completed until mid-2004, with product availability by 3Q04. However, more important is the fact that both IP telephony and WLANs are plagued by their own immaturities, and combining the two technologies opens the door to a host of additional problems.

Although the market for voice over Wi-Fi remains immature, META Group clients have deployed some for specific niche applications. In the short term (2003/04), voice over Wi-Fi deployments will be limited to test-bed implementations and small-scale vertical applications (e.g., warehouse, retail, healthcare). By 2005, voice over Wi-Fi will be combined with WLAN systems for small office-in-a-box deployments but will not displace incumbent telephony systems in large enterprises to any significant extent. Longer term (2006/07), devices will offer both Wi-Fi and cellular connectivity, enabling users to carry one phone and be connected across public and private wireless networks. Users will prefer traditional desk phones while in the office due to constrained usability and functionality of mobile handsets.

Articulating the Attraction. Wireless telephony is a requirement for many businesses as they seek to provide communication capabilities to a mobile workforce. Currently, the main adopters of in-building wireless systems include retail, healthcare, logistics, and education industries, as well as general warehousing applications. At first glance, the cost of deploying voice over Wi-Fi appears to be lower than incumbent in-building systems due to decreasing Wi-Fi component pricing and the ability to converge voice and data over a single wireless infrastructure. Yet the quality and reliability of voice over Wi-Fi do not currently equal that of incumbent solutions - driving up support costs and causing adoption to be limited. A hybrid approach that combines cellular and Wi-Fi into a single telephony device has sparked the interest of enterprises and vendors alike. Mobile carriers view these solutions as a double-edged sword, because a dual-mode architecture implies the loss of call revenues during the period the user is passing calls over the enterprise-owned Wi-Fi infrastructure. However, to maintain competitive advantage and decrease customer churn, carriers will need to evolve traditional services and should use Wi-Fi for differentiation.

Proclaiming the Problems. The largest issue hindering broader voice over Wi-Fi adoption is the immaturities that still exist within WLANs (e.g., security, management, scalability, predictability, quality of service). A new breed of WLAN systems will solve many of these issues (see Delta 2399). However, adding insult to injury, voice over IP systems have yet to offer the stability of traditional time division multiplexing (TDM)- based systems. Voice-over-Wi-Fi solutions are currently based on the 802.11b standard and are thus limited in bandwidth and scalability. Our research indicates the average access point can support four to five simultaneous calls before voice quality starts to degrade. Startup vendor Vocera offers a stripped-down feature set and greater compression, increasing that number toward 15 to 20 simultaneous calls; however, it lacks complete integration into the existing PBX (or IP PBX) infrastructure.

Security is a problem with any application running over the Wi-Fi network, and telephony is no exception. Few voice over Wi-Fi handsets offer support for new Wi-Fi security standards such as 802.1x and WPA (Wi-Fi Protected Access). Furthermore, enabling security can cause substantial mobility issues, often resulting in dropped calls due to the time it takes for the device to successfully reauthenticate to the neighboring access point. Some vendors (e.g., Cisco) get around this problem through proprietary protocols and wireless system-level intelligence (e.g., Airespace, Meru Networks) that pre-empts client roaming.

As with any mobile device, wireless IP phones have a limited battery life due to the relatively heavy power consumption of 802.11b. Current-generation products support three to four hours of talk time and up to 80 hours of standby. Improvements in 802.11b components will continue to decrease the power drain and improve total talk time.

Vocalizing the Vendors. The in-building wireless market has been dominated for some time by SpectraLink, with 71% of its revenues in 3Q03 coming from the 900MHz systems, and Wi-Fi based products accounting for 29%. Symbol Technologies had been the alternative handset provider, though its market presence has substantially declined, with most vendors choosing to partner with SpectraLink. All the major IP telephony vendors have sought to augment their existing portfolios with voice over Wi-Fi solutions either through partnerships with SpectraLink and Symbol (e.g., 3Com, Avaya, Nortel) or internally developed systems (e.g., Cisco). However, most of the vendors still lack sizable customer deployments of voice-over-Wi-Fi solutions. Vocera offers a voice over Wi-Fi solution that is designed to meet the in-building telephony requirements for healthcare and retail verticals and is based on speech recognition and push-to-talk features. Our research indicates Vocera is gaining traction within these vertical markets; however, we see limited crossover into the horizontal enterprise due to the lack of integration with existing telephony infrastructure and the limited set of features provided by the system.

Business Impact: Assessing the reliability of infrastructure - especially when supporting mission-critical applications - must be the cornerstone of the deployment decision.

Bottom Line: The promise of voice over Wi-Fi continues to attract enterprise attention; however, the realities of current solutions limit the extent to which IT organizations can reliably adopt the solution. Organizations with a real requirement for wireless telephony should adequately assess the stability of emerging Wi-Fi-based systems or rely on incumbent in-building wireless solutions.

META Group originally published this article on 1 December 2003.

Editorial standards