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Feature Article
September 2004

Wireless VoIP - The PDA Challenge


Being in contact with your associates and customers is often the key to success in today’s hectic business world. Text messaging remains a popular mode of communicating, as is the ability to reach someone by cell phone while away from the desk. Another mode of communication that is increasing in popularity in the enterprise is “walkie-talkie” mode, the ability to instantly reach out to one or more team members for an ad hoc meeting. Complicating the requirement to support these modes of communication is the fact that many mobile workers also require a portable or handheld computer to access or update corporate information via software applications.

How does the modern mobile worker take advantage of these multiple modes of communication? Many companies have addressed the problem by equipping their associates with application-specific units, resulting in users appearing to have the fabled “Batman utility belt.” A dedicated pager, phone, walkie-talkie and PDA will meet the requirements for communications and application productivity, but risk making it more difficult for the user, all while delivering higher CAPEX and OPEX expenditures.

So, what is the solution? One appealing option is the concept of a converged PDA device that will support all of these forms of communication. While it seems simple enough to envision such a converged device, there are specific challenges to delivering a device that meets the market’s functional, cost, and ergonomic requirements.

The primary requirement for many enterprise workers is access to software programs that support business applications, such as purchasing, receiving, inventory control, and customer relation management (CRM). Which application is being used typically dictates the basic form factor of the mobile unit. A converged solution could potentially include wireless LAN and WAN access, as well as support for audio input/output, but a single solution set may not fit all users’ needs.

It is pretty easy to design a PDA with a microphone and speaker, but is that all it takes to support voice applications? A major consideration for a successful converged PDA is the usage model for the voice application. Typically, we find that there are three possible usage scenarios:

  • Handset – unit is held to the ear and used like a standard cell phone.
  • Headset – unit is capable of being connected to a headset with a microphone and headphone(s).
  • Speakerphone – hands-free usage.

Some job duties require the use of a handset “phone,” a lightweight unit where the unit is held to the ear like a cell phone. This is usually accomplished with a slim device that is used primarily for telephony service. Such a form factor requires attention to mechanical acoustics in the design of the unit to minimize internal echo between the speaker and microphone. In addition, there are regulations (e.g., HAC — Hearing Aid Compatible) that govern the design of such devices to accommodate users with hearing aides. Most commercial PDAs do not offer this mode of use or even optimized audio support, like advanced echo cancellation.

Almost universally, voice-enabled PDAs provide headset support. While affording virtually echo-free voice quality, there is often a problem with the fact that the headset is tethered to the PDA. This poses a problem in some markets, like healthcare, where the user also needs to have easy stethoscope access. This problem can (to some degree) be addressed by using cable-less (e.g., wireless) headsets that take advantage of technologies like Bluetooth.

For applications that require hands-free usage, the mobile unit must support a speakerphone. This design will allow a user to “listen” to audio traffic with the unit on their belt or can be used as a mobile conference phone when used in a full-duplex mode. Additional electro-mechanical design considerations must be made to support a push-to-talk (PTT) mode, such as providing a dedicated, external PTT key. A totally hands-free-only model with a speakerphone will have limited market appeal and could have a battery life (power management) problem.

What is learned from understanding these facts? No single form factor will address all the market requirements and some “shopping” will be necessary to find the right PDA that supports the correct feature set required.

How and what wireless technology is used to access the network is also a challenge. If wireless connectivity isn’t already embedded in the device, many PDAs can be made “wireless” through the addition of a CompactFlash Wi-Fi card. While not a major hurdle, this approach requires site-specific configuration and on-going device configuration management. In addition, the most appealing wireless design is a dual-mode design. Conceptually, this is a device with both wide-area and local-area wireless radios built into the unit. With such a device, one can continuously use the PDA both indoors (WLAN) and outdoors (WAN). Such devices are coming to the market, but are initially going to have vendor-specific limitations. Early offerings also may not meet the conceptual expectations of a ubiquitous communication device.

Perhaps one of the biggest and most subtle problems with the PDA form factor is the challenge of security. These devices will support converged voice and data streams, and therefore, enforcement of security policies will be very important to the enterprise IT team. Because of the fact that the most rigorous wireless security schemes impose increased latency on network traffic, any voice application executing on these devices will be impacted with lower voice quality. Since real-time applications (telephony or streaming video) are highly sensitive to latency, selecting the optimal security policy will be a key factor in implementing a successful configuration. In the final analysis, when choosing a security policy, you must consider whether you want to enforce maximum security or optimize voice quality.

An end-to-end, converged PDA solution requires components from multiple vendors — a PDA that supports the right hardware feature set, the right network access hardware (WLAN and/or WAN), the proper applications software, and network service provider. Putting all these pieces together in a coherent solution is a challenge and requires a thoughtful approach in understanding the market and spending some time evaluating the matrix of possible solution configuration options, as no single vendor provides the total solution. An elemental challenge often revolves around identifying a properly configured PDA and a software component that has been modified to take advantage of vendor-specific hardware features. This multi-vendor challenge makes it difficult to select best-of-breed components for the overall solution. Vendors must partner together to provide an “optimized” solution set, but such solution components are often marketed through different channels, which further complicates the task of defining a complete solution.

It can be a challenge to define and deliver a wireless, converged PDA solution. Is it easy? No. Are their any universal solution sets? Not today. Being able to select and deploy the right configuration will depend upon defining a complete solution set that includes a PDA that offers support for required input/output options, software applications that are designed to accommodate the chosen hardware platform, and a network designed to provide the right access and performance characteristics.

What is the best advice regarding exploring options for converged PDA solutions? Be patient and evaluate products as they become available. Make sure you know what minimum feature set you need and make your decision based on the ability to meet minimum feature requirements, as well as a complete ROI analysis. c

Richard Watson is director of product management for LongBoard, Inc. He previously was director of telephony product marketing for Symbol Technologies’ Wireless Systems Division in San Jose, CA, where he was responsible for marketing Symbol’s NetVision family of WiFi Telephony products, managing its software engineering team and developing Symbol’s WiFi Telephony products.

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