Voice on Terminals (VOT): white paper


In today's enterprise, employees or associates communicate more frequently using a wider variety of methods and devices. Perhaps the most important business communication method is the ability to simply make a phone call. The need to communicate in real time with internal associates throughout the enterprise and to partners and customers external to the enterprise has led to a proliferation of mobile devices for both voice and data communications.

It is commonplace to see associates carrying multiple devices such as a data collection terminal, pager, cell phone or walkie-talkie. Collectively, these devices support the direct associate-to-associate and customer-to-associate communication that is a requirement of so many jobs. Raising the bar in supporting mission-critical mobile business applications includes designing voice features into a variety of mobile devices, including data collection terminals.

A wireless data device that is also connected to the enterprise private branch exchange (PBX) and to the larger public switched telephone network (PSTN) supports calls to associates, customers and vendors, making it a powerful tool for improving associate productivity and enhancing customer service. The converged solution of voice and data places all the value and benefit of a traditional desktop telephone into the hands of mobile associates while leveraging the investment of the data capabilities. The result is a single device on a single network that is used for multiple purposes, which enables organizations to do more for less.

This white paper explores the benefits and challenges of consolidating the voice communication features of multiple devices onto a single wireless local area network (WLAN) and into a single mobile handheld device.


Adoption of the Institute for Electrical and Electronics Engineers (IEEE) 802.11 standards for wireless LANs and the maturing of voice-over-IP (VoIP) technology have set the stage for a new productivity tool voice on terminals (VOT). Many organizations are already aware of the strong business value add that wireless telephony delivers and have deployed cordless or cell phones to meet this need. However, these products offer only a limited range within a business facility or add ongoing monthly costs for service contracts to operational expenses. Utilizing the installed 802.11 wireless infrastructure for both voice and data is the ideal approach to solving most employee communication requirements. This converged solution allows for leveraging wireless LAN investments to eliminate limitations found in the other communication alternatives such as limited range (building coverage) and monthly fees.

Today's Opportunity

There is a clear market interest for in-building wireless phones. Approximately 200,000 wireless phones were sold in 2002, which encompassed proprietary 900Mhz/1.9Ghz solutions, licensed personal communications services (PCS) and a rapidly growing segment of 802.11 devices. The 802.11 market segment for in-building wireless phones is projected to grow to over 500,000 thousand devices annually by 20071. Within the 802.11 market, the "softphone" is an emerging product class that is attracting significant attention. This is a wireless personal digital assistant (PDA) (i.e., HP iPAQ) that is configured with a softphone application to become a VoIP-enabled device a converged voice/data solution. With the exception of the PDA-softphone, all the other commercial offerings are voice centric and require employees to carry multiple devices to support both voice and data application access. (1Instat/MDR, March 2002.)

There is a strong requirement for a rugged, reliable, converged voice/data terminal that also provides key telephony functions. However, most consumer or retail PDA-based solutions are unable to meet the durability requirement for operation in commercial environments or provide for high quality, full function voice capabilities. Therefore, providing a single, ruggedized PDA device for execution of business data applications concurrently with PBX and PSTN connectivity and toll quality voice fills an important market need.

Strategic Approach

The successful implementation of a voice/data terminal requires attention to three technological arenas:

Hardware: To properly support the voice application, the hardware requires a design that incorporates a digital signal processor (DSP) for handling the voice compression/ decompression and mechanical design that provides for microphone, speaker or speakerphone with appropriate acoustical characteristics.

Software: Addressing all the unique wireless VoIP challenges -- wireless QOS, wireless latency, secure fast roaming -- must be addressed because current VoIP technologies lack the design considerations for a wireless 802.11 implementation.

Telephony integration: Customers adopting the wireless VoIP solution often need a total solution that provides for integration into legacy PBX systems and emerging PBX and iPBX solutions.
Making the right hardware product decisions is only part of the solution for a robust converged voice/data implementation. Addressing both the software and integration challenges require domain knowledge that includes an in-depth understanding of the challenges in implementing VoIP on wireless plus how to implement a best-in-class 802.11 wireless VoIP solution. The following sections detail the technical challenges, solution options and implementation choices for a robust converged voice/data terminal product.

The Challenges

A wireless terminal utilizes the same transport services that a desktop computer uses to support business applications. These applications are based on transmission control protocol/Internet protocol (TCP/IP), which is configured with appropriate wireless security services. Support of VOT is similar in that it is typically a TCP/IP-based application, but the challenges faced by a wireless voice application are unique. A robust wireless voice application also incorporates solutions to each of the following challenges.

3.1 Security

For chief information officers (CIOs), security is the biggest concern when considering the deployment of a wireless LAN. Fear of a hacker or spy stealing or corrupting valuable company data forces information technology (IT) managers and CIOs to take a conservative position. The security technologies applied to address these data security concerns often impact the ability to deliver good quality voice over a wireless LAN. The primary negative factor to voice quality is the additional burden of latency resulting from the implementation of the security policies. However, some security options have minimal impact on wireless voice quality.

There are a number of wireless security schemes, mechanisms and standards to choose from. The basic 802.11 standard defines wireless equivalent privacy (WEP), which is supported by all 802.11 product manufacturers. A flaw is inherent with this architecture, but unfortunately the 802.11i standard that addresses this problem is pending ratification. In the absence of a defined wireless security standard, market players have moved forward and other advanced security solutions have been implemented.

Commercially Available Solutions

The current pre-802.11i options offered by vendors include:

Virtual private network (VPN)
Kerberos with KDC

Use of a VPN is a straightforward solution to wireless security problems as it provides security control at the highest level with end-to-end encryption across a connection. VPNs meet authentication and data security requirements but impose a severe penalty on real-time applications like VoIP. Without an assist from a high-end processor or coprocessor, applying the encryption policy at the transport level degrades the resultant voice quality of a wireless PDA-class device. The tunneling of the packet flow through a VPN also adds to the overall latency within the system and further degrades the voice quality.

It almost seems, therefore, that VPNs and wireless VoIP are mutually exclusive. This is not quite true, but care must be taken in implementing and deploying a wireless VPN solution. Consideration for the computing power of the handheld, its battery capacity and the VPN design within the network fabric must all be assessed in an attempt to guarantee a secure, high-quality VoIP solution.

Wireless infrastructure vendors offer their own RF-domain security enhancements that provide some answers to the heightened wireless security concerns.

Cisco Systems offers the LEAP/RADIUS wireless security solution. In this architecture, each time a device re-inserts itself into the network (roams), it must have full re-authentication. Depending upon the complexity of the hosting network, this operation adds approximately 150-250 msec (or longer) of latency to a roam operation. Such a small fraction of a second is insignificant to a data application, but results in a degradation of the voice quality at roam time.

Kerberos is a security architecture developed at MIT and implemented in most Unix products. Used as a standard security scheme for over 20 years, Kerberos provides a method of unit authentication and key management. It is implemented to support mutual authentication when every device within the network fabric -- including access points -- is authenticated. Once authenticated within a secured network, roaming from access point to access point is made secure through the passing of pre-secured credentials verified between parties. This architectural approach supports the concept of a fast, secured roam without requiring a complete re-authentication upon each roam. In addition, Kerberos goes beyond a simple authentication scheme to provide for dynamic key management for compliant devices.

Proposed Standards-Based Solutions

The wireless industry is working, both in standards bodies and collaborative associations, to enhance the wireless security options and attempt to ensure cross-vendor interoperability of products. Good examples of these in-process works include:

Wi-Fi-protected access (WPA)
Temporal key integrity protocol (TKIP)
Advanced Encryption Standard (AES)

The works are derived from the ongoing efforts of the IEEE 802.11i task group and are focused at defining two categories of wireless security schemes:

1) Enhancing the standards-defined security that is compatible with current
hardware products; a security model that is implemented without changing
the hardware.
2) Defining a stronger security standard that may require hardware assist to
be built into future devices.

Figure 1 identifies these new components and how they relate to the original security schemes. Implementations of WPA and TKIP architectures are defined to fit into category #1 of the new security offerings. AES is a more robust security algorithm adopted by the military and federal government for their encryption standard2 and is also the driving technology for security category #2. (2AES has replaced the use of DES and Triple-DES in many government deployments.)

WPA is a drafted compliance statement from the WiFi Alliance (formerly WECA), acting as a collective in advance of ratification of the IEEE 802.11i, that defines a security platform for support by all current 802.11 vendors. Although this platform is more like an ad-hoc standard, it describes facilities for authentication/authorization and defines a stronger encryption specification for commercial availability today. The WPA includes a functional component called message integrity code (MIC); "Michael" is a specific MIC being used that is designed to detect frames generated by a rogue network device posing as a legitimate device. This further enhances the security of the network beyond simple encryption of the data. While this is a realistic approach to addressing data application security attacks, it is the less optimal approach for support of a real-time audio application. Like other security mechanisms, the MIC imposes an additional latency penalty that degrades the voice quality. There is some concern about voice applications being supported under WPA without hardware assists.

TKIP is an extension to the IEEE 802.11 WEP standard that was created to "plug the hole" in the initial draft of the RC4-based encryption standard. In this scheme, the scope of the key management scheme (initialization vector) is significantly extended along with a new requirement that each packet transmitted is encrypted with a new key. TKIP also includes the implementation of a MIC Michael that adds a per-packet source validation mechanism. When completed and ratified, this component of the 802.11i standard significantly strengthens the encryption mechanism supported by all 802.11 vendors.

AES is the ultimate standard for implementing a strong encryption scheme and is deployed in conjunction with the CCMP (Counter-Mode/CBC-Mac Protocol) service layer to provide authentication and integrity capabilities. Generally accepted as the strongest encryption method available today, AES provides stronger encryption services than RC4 but often requires hardware (ASIC) assists for optimum voice quality when designed into low-end, battery-powered devices.

3.2 Quality of Service (QOS)

Good voice quality demands the timely delivery of audio packets to the receiving device. Typically, a delay of more than 60 msec in delivering audio packets results in a deterioration of the overall voice quality. Management of this delivery problem requires enforcement of quality of service (QOS) that guarantees delivery of selected packet types within certain latency limits. For 802.3 networks, QOS is mandated by the IEEE 802.1p standard, a mechanism that tags each packet or frame with a priority label. As that frame traverses a network fabric, each switch and router enforces the indicated QOS in preference of lower QOS tagged frames. Unfortunately, in the IEEE 802.11 standard, QOS specification is unavailable so what can be done to provide a wireless VoIP product?

The wireless segment of a network, by its nature, is the more fragile component with regard to reliability frame transmission/reception where QOS is important. The 802.11e working group within the IEEE standards body is currently finalizing a wireless QOS specification, but this is only expected to be ratified in late 2003. As a result, implementations of the "e" standard are commercially unavailable until some time in 2004. Until then, today's product offerings meet this challenge using a proprietary QOS architecture.

3.3 Access Point Congestion

While wireless QOS is important in ensuring good voice quality, it is not sufficient to address a total wireless voice implementation on its own. VoIP traffic places a unique demand on the wireless infrastructure, specifically the high packet per second rate. Most data applications are "bursty" and transmit large data frames. This kind of traffic is addressed through the data throughput capacities of the access points (Kilobits per second). Voice traffic is isochronous with small packets and places a different demand on access points. Because much of a voice frame is header, there are a fixed number of frames per second that any one access point processes. In this case, it is possible that a large number of VoIP applications might choke an access point by pushing it to its packet/second limit. This creates points of congestion within a wireless infrastructure, degrades voice quality (even with QOS) and causes data application failures resulting from the voice traffic congestion.

Addressing this potential congestion problem are general approaches that either:

1) Maximize the throughput (number of calls) through any single
access point, or
2) Distribute the traffic demand more evenly across multiple network

Maximizing throughput at any one access point is best achieved through aggregation of the audio stream packets to minimize the access point packet per second demand. Implementing this technique has a demonstrable impact on being able to control congestion problems, but it requires design cooperation between the participating component vendors.

Traditionally, distribution of traffic to minimize access point congestion has been approached in one of two ways:

1) Manage congestion by creating intelligent mobile client RF modules, or
2) Manage congestion through a centralized server within the network.

Managing potential congestion at access points via intelligence within the mobile device requires collaboration with the infrastructure to provide additional access point loading information that permits making such intelligent roam decisions. This typically requires a modification of certain 802.11 signaling elements to carry this information. Fortunately, the 802.11 standard is written in such a way that this is possible without breaking another vendor's products.

Other vendors attempt to manage the access point congestion issue with a server-based architecture where each mobile unit registers and derives roam information and roam permission from the server. This is an application level architecture, a vendor/device specific solution that requires additional devices be added to the network.

3.4 Out-of-Range Management

Telephone systems are noted for their reliability and robustness even when the power goes out, the phones usually remain working. For a wireless voice application, this same level of robustness is assumed, but some application and protocol considerations must be addressed to deliver this level of reliability. Because of the nature of the wireless infrastructure and reliance on battery sources for power, wireless phones can disappear while in a call. This behavior is the result of a dead battery or merely walking out-of-range (out of coverage area).

Application behavior with this problem is typically governed by the services of the selected call control protocol (i.e., ITU H.323, IETF SIP). Since none of the standard (or proprietary) call control protocols were designed with a wireless implementation in mind, none of them provide native solutions to this problem. The consequence of ignoring this behavior is to lose calls when you walk out of the coverage area or lose system resources because the situation is not detected. An example of this is when a battery dies on a mobile unit while during a call. The telephony system should detect this fact within a short period of time (20-30 seconds) and tear down the call on the system side to release the resources for another call. Without modifications to the architecture, many standard systems take minutes to detect this problem and reset the system to a nominal state. Of course, this is unacceptable in a system that relies on high reliability and availability.

3.5 Voice Terminal Design Considerations

Once the network and RF challenges are addressed, the feature set of the mobile device itself is considered. In order to provide the best user experience with wireless VoIP, the following items need to be addressed at the mobile unit level:

A digital signal processor (DSP) is needed to supply the necessary compression codec services. Support of codecs like G.726 and G.729 place such a duty cycle burden on a host CPU that this function is often best handled with a compressor. Mobile units that are designed to support VoIP have a very fast CPU clock (400Mhz or greater) or a dedicated DSP coprocessor.
Acoustic design is important because the mechanical and electrical design of a VoIP-enabled mobile unit reflects clear design intent and support: microphone or speakerphone and/or headset. Also, assessing the basic ergonomics of the device and how a user holds the device while in a conversation is a critical consideration, because this is not usually a factor for PDA-class devices.

3.6 PBX Integration Considerations

Finally, it is vital to provide cost-effective, feature-rich solutions for integration into the customers' telephony systems (PBX or iPBX). It is through these systems that a simple phone call to the vendor or customer is made. Two solutions are available to provide such integration:

Gateway/adjunct solutions
Direct integration solutions

The gateway solution addresses the legacy market opportunities. Organizations with traditional PBXs connecting them to the PSTN are able to install a wireless VoIP solution by adding a gateway product, which also supports an analog or digital telephony interface. The gateway also provides a network interface and acts as an application bridge in support of VoIP-to-analog/digital translation of the signaling. This approach allows a business to retain their PBX investment while extending the services to include wireless VoIP.

Direct integration solutions are designed to complement the VoIP services being offered by the host PBX or iPBX. As VoIP technologies are deployed, more and more telephony vendors offer proprietary native VoIP support. Typically implemented to support an IP-desktop phone, these solutions also support wireless VoIP solutions that conform to the vendor's VoIP architecture and protocol. These solutions offer the tightest and most feature-rich solutions, but require the customer to already have made a VoIP decision with the internal telephony services.

The Solution

A robust wireless VoIP solution requires attention to supported components and functions across multiple technology disciplines. Attention to RF infrastructure design, Ethernet network configuration, security policies, acoustics, telephony and mechanical design converge across a multi-vendor landscape to result in a strong wireless VoIP solution.

Support with wireless infrastructure features (power save mode, QOS, security)
Collaboration with telephony customer premises equipment (CPE) providers
Acoustical and mechanical design requirements
Adherence to standards

Vertical Applications: Demonstrating the Value

Having telephony support in a terminal requires a demonstration of real value-add to drive market demand. Price premiums for voice-enabled terminals require a strong return on investment (ROI) justification for the expense. The answer to the ROI question is two-fold: there are hard and soft ROI realizations with such devices. The hard ROI examples identify specific and calculable savings as a result of deploying such solutions, and the soft ROI considerations are valuable and real, but often subjective in any attempts to quantify them. The detailed ROI analysis is different for each market segment based on cost structure and business dynamics in considering communication technologies.

All ROI analyses start from the consideration of a customer's direct communication requirements. Whether this is between employees, employees and customers or employees and vendors, most organizations have a real business need for reliable, quick communications to keep their companies competitive and successful.

Hard ROI values are derived through the mitigation of current expenses. Whether it is the result of lowered material costs or elimination of ongoing operational expenses, these economic considerations are easily quantified. ROI metrics are derived from:

Elimination of duplicate infrastructures: Some wireless VoIP solutions require deployment of a separate wireless network just for voice. Converged solutions (utilizing the 802.11 wireless LAN) provide a built-in reuse of the existing wireless LAN infrastructure, which also mitigates the cost and total cost of ownership (TCO) of the entire system. Additionally, if consideration of a converged wireless LAN solution is made with new construction, significant savings are realized without having to deploy a hardwired telephony infrastructure and relying solely on the wireless services for voice and data.
Elimination of duplicate devices: Deploying wireless devices that provide both telephony services and in-building communications such as walkie-talkie features eliminates the need for additional communication devices. In addition to voice, support of text messaging or paging on the same wireless device eliminates the need for pagers. Again, the concept of converged voice and data, one device for many functions, lowers overall expenditures.
Elimination of ongoing service charges: Other companies have deployed cell phones to provide for in-building communication. However, this option includes annual service contracts with the service providers. Also, some walkie-talkie products require a license to use the spectrum, which is eliminated when using a wireless LAN converged solution. Converged terminal devices are purchased as capital expenditures and ongoing service charges and license fees for devices such as pagers and walkie-talkies are mitigated through a converged solution.
Elimination of unnecessary associate functions: When deploying wireless communication devices, many companies restructure their personnel organization, resulting in a streamlining that achieves business goals with fewer associates. The fact that associates are mobile and still reachable is an important factor in how a business allocates its people resources.
Soft ROI contributions are more difficult to quantify. These benefits often fall into the category of productivity improvements and associate response time enhancements. While difficult to quantify, these considerations do contribute to an overall ROI. This simple example of productivity improvements for the management-level associate easily demonstrates the potential in positive ROI:

A manager saves 10 minutes each day by using a wireless phone. This timesaving comes from the fact that this manager answers calls while on the floor and isn't trapped at his or her desk answering voice mail. If the manager makes $80,000 per year, then each minute of his or her workday has a value of approximately 65 cents. Saving 10 minutes each day provides a $6.50 per day productivity enhancement which, when extrapolated for the whole year, amounts to $1,625. If the extra time afforded to the manager each day is economically productive in increased sales, then it is easy to justify the purchase of a wireless VoIP solution.

In addition, responding to customer and vendor calls immediately without having to interface with a voice mail system raises customer or vendor satisfaction levels. Responding to emergencies is also greatly enhanced through use of an in-building wireless VoIP application.

Beyond the basic ROI considerations listed above, support for the VoIP services provides a platform for adding other high-value applications that are mission critical to certain vertical markets. Nurse call capability is such an application in the healthcare market. With this application, teams of nurses coordinate when responding to patient needs through alerts sent to the mobile device with responses through the telephony system. Given the growing nursing shortage in the healthcare industry, this voice/data application is essential for hospitals.

Solutions from Symbol Technologies

Symbol Technologies, Inc. delivers enterprise mobility solutions that enable anywhere, anytime data and voice communication to help companies' increase productivity, reduce costs and realize competitive advantage. Voice on terminals (VOT) is an important Symbol initiative that enhances its robust enterprise mobility product and technology portfolio. Integrating advanced voice capabilities into Symbol handhelds and mobile computers is a priority, and the following section highlights the product roadmap to provide converged voice/data solutions in select Symbol terminals.

Strategic approach:

The PDT 8146 from Symbol Technologies, based on the Intel XScale processor, is an excellent example of a PDA terminal that includes a hardware platform that also provides hardware assist in compressing voice streams or DSP functions. This dynamic handheld incorporates a microphone/speaker as part of the standard electromechanical design. The chart below demonstrates how a PDT 8146 handheld is used as a PBX-connected device. In this example, the mobile device is used to place/receive calls to standard telephones at the same time it supports Microsoft Windows Pocket PC data applications in a wireless environment.

Through the initial development efforts of the WiFi VoIP NetVision phone, Symbol gained the domain knowledge that includes an in-depth understanding of implementing VoIP on wireless and how to implement a best-in-class 802.11 wireless VoIP solution. The ability to provide total integration solutions for wireless VoIP devices also requires strong partnerships between the handset developer and the telephony system provider. Symbol is currently working with select worldwide telephony providers to provide for legacy integration as well as seamless VoIP integrated solutions.

Based on the order of unique challenges presented in this white paper in Section 3, the implementation choices chosen by Symbol are detailed below.

6.1 Security

Symbol implements Kerberos wireless security as a pre-802.11i offering, because this fast, secure roam architecture is ideal for streaming applications like VoIP. Symbol also offers a pre-802.11i enhanced version of TKIP encryption called KeyGuard. Both Kerberos authentication/key management and KeyGuard provide significant enhancements to the 802.11 security issue without degrading the voice quality. Support for WPA and 802.11i (including AES) are expected to be introduced for designated products as these standards are ratified and/or certifiable.

6.2 Quality of Service (QOS)

For several years, Symbol hs invested in its 802.11 product offerings and has supported a Symbol wireless QOS service. In both the popular Spectrum24 and Wireless Switch product lines, a proprietary QOS is supported that incorporates direct support of the VoIP standards3. Unique from other proprietary QOS offerings, the Symbol implementation provides a QOS mechanism where audio frames based on the IETF real-time protocol (RTP) standard are treated with higher priority in transmission processing. An audio stream from/to a Symbol voice client is automatically given priority over data traffic to ensure the very best voice quality with minimal latency. Support for the 802.11e standard will be provided by Symbol through firmware updates to support standards-based QOS. Without a VoIP QOS, wireless LAN voice applications are unacceptable in their delivered voice quality. (3Cisco Systems AiroNet products also support Symbol VoIP QOS in their latest access point firmware).

6.3 Access Point Congestion

Symbol approaches this challenge with pre-emptive roaming and packet aggregation. Packet aggregation has been achieved in select Symbol products through a cooperative development with partners. The goal of the cooperative is to support a flexible audio stream that is optimized for each installation. Currently, Symbol offers the highest call capacity of any product offering at 10+ calls per access point.

When considering roaming, many wireless implementations implement a distressed roam model: "roam when I have to." A pre-emptive roam model is: "roam when I need to." The need is based on more than the condition of the network and includes some application optimized criteria. This intelligent client approach is the model for Symbol mobile unit clients and voice devices. Using load information from the access points, mobile devices make intelligent decisions about roaming to a new access point. Pre-emptive roaming results in load balancing within the network, and Symbol mobile units make collaborative decisions to load balance across multiple access points. Voice devices are driven in their roam decisions to ensure the best voice quality and will roam to a less congested access point. The result of this model is virtually no congested points within the network with voice quality and data throughput maximized a Symbol unique feature.

6.4 Out-of-Range Management

Wireless voice implementations from Symbol are co-developed with select telephony partners in order to deliver robust out-of-range services into mobile devices. This helps to strengthen and extend the reliability and availability of the total system.

6.5 Voice Terminal Design Consideration

Symbol meets these design challenges by making voice-centric design decisions early in the product lifecycle for many new terminal products. The NetVision phone and the PDT 8100 family of products are just the beginning of a robust offering of hardware and mechanical design in addition to software that supports VoIP applications.

6.6 PBX Integration Considerations

The Symbol strategy embraces both gateway and direct integration solution approaches. For customers that need to retain their legacy PBX investment, Symbol supports a variety of gateway options that allow for straightforward deployment of wireless VoIP devices. Through strong partnerships with strategic telephony partners, Symbol offers a virtually seamless integration solution for these partners' VoIP architectures.

A Total Solution

Symbol provides solutions in a number of disciplines including RF, security, mechanical and acoustics. Offering both mobile computing devices and the RF infrastructure enables Symbol to be a premier vendor, bringing the most comprehensive, unified wireless VoIP portfolio to the market. It enables Symbol to offer a wider array of complementary products to ensure interoperability between mobile terminals and provides value added features for products sourced from multiple vendors.

To assure the market of a continuing offering that is robust and feature rich, Symbol is committed to providing ongoing support for emerging standards that come out of the 802.11 working groups. Whether it's new security schemes or expanded QOS services, Symbol strives to support these standards.

Vertical Applications - Demonstrating the Value

Symbol's implementation of telephony services for terminals includes facilities for integration into other high-value applications plus application programming interfaces (APIs) to allow for extensions of feature sets. Simple telephony is a strong value-add, but the growing Symbol developer community delivers the capabilities to customize and enhance important features for the strongest VOT solution.

Glossary of Terms

AES: Advanced Encryption Standard an advanced encryption scheme that is more secure than the traditional encryption algorithms such as DES, Triple DES or RC4.

iPBX: IP Private Branch Exchange Private Branch Exchange systems are designed to provide VoIP services in addition to or instead of the traditional time domain multiplex (TDM) services of the PSTN.

IETF SIP: Internet Engineering Task Force Session Initiation Protocol. This standard emerged as a leading architecture for future VoIP solutions. Initially adopted for its simplified architecture, it has received worldwide industry focus.

ITU H.323: International Telecommunications Union standard H.323. This voice/video standard for packet networks is widely implemented for VoIP support.

Kerberos: This security architecture was developed by MIT and originally delivered as part of the Unix based technologies to support fast, secure roams within a fully authenticated domain.

LEAP: Light Extensible Authentication Protocol-a Cisco Systems' proprietary wireless authentication protocol.

PBX: Private Branch Exchange telephony systems hosted within businesses to provide extended features required by commercial concerns. A term that is synonymous with customer premise equipment (CPE).

PSTN: Public Switch Telephone Network is the traditional telephony hardwired international network.

RADIUS: Remote Access Dial-In User Service this industry standard was initially implemented to support authentication requirements for Internet service providers (ISP). Many wireless LAN vendors adopted this architecture for the wireless LAN authentication because of its popularity.

TKIP: Temporal Key Integrity Protocol is an IEEE security standard that is part of the proposed 802.11i standard and the WiFi Alliance WPA. This scheme extends the encryption design of WEP and addresses the flaws of the former.

VoIP: Voice over IP is a packet-based technology that is being rapidly adopted worldwide for transmission of voice traffic. In addition to carrier level adoption of this technology, many PBX telephony vendors now offer their own VoIP desktop service.

VOT: Voice on Terminal is a data terminal with a converged voice component that has value in the commercial space where daily job requirements necessitate use of both phone and data applications.

WiFi: Wireless Fidelity is a term generally applied to all commercial 802.11 products, but more specifically it refers to products that comply with the WiFi Alliance interoperability certification requirements.

WPA: WiFi Protected Access is a collectively supported "standard" for implementing enhanced wireless standards ahead of the ratification of the 802.11i. The WiFi Alliance has driven this initiative and is responsible for coordination of vendor conformance.


Following is a list of resources utilized in the course of authoring this paper:

Voice Over Wireless LAN: 802.11x Hears the Call for Wireless VoIP, In-Stat/MDR, Brian Strachman; March 2002, Report Number: IN020170LN.

Voice Over Wireless LAN: Will the Market Finally, In-Stat/MDR, Brian Strachman; March 2003, Report Number: IN020675CT.

Crossing the Chasm, Harper Business Books/Geoffrey Moore; August 20, 2002. ISBN: 0060517123.

Packet-based multimedia communications systems - H.323, International Telecommunications Union; September 1999.

SIP: Session Initialization Protocol, Internet Engineering Task Force; June 2002, RFC-3261.

WiFi Protected Access (WPA) v1.2, WiFi Alliance; December 16, 2002.

About the Author

Richard Watson is Director of Telephony Product Marketing for Symbol Technologies, Inc. He joined Symbol in 1997 as telephony engineering manager and telephony product marketing director. He has over 24 years of industry experience that includes positions at 3Com and Motorola, both leading companies in networking and wireless technology. Watson holds several networking patents and is a frequent contributor to industry publications on networking and VoIP telephony.

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