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Feature Article
January 2003

VoIP Protocols -- Wireless Friendly?


It is clear from market response that Voice over IP (VoIP) has been embraced by commercial enterprise and telephony manufacturers alike. Viewed for some time as a technological curiosity, VoIP was thought to be incapable of delivering the necessary voice quality and telephony feature set required by today�s demanding marketplace. These concerns have now been addressed and companies are purchasing and deploying more than 10,000 IP-phone handsets per month. An additional validation of the �mainstream arrival� of VoIP is the fact that all major telephony vendors have a VoIP solution as part of their product offerings. VoIP has been accepted by business as a maturing, viable technology that not only delivers the requisite voice quality and telephony features, but can be a significant factor in managing telephony costs across an enterprise. The adoption of VoIP solutions is so rapid that industry analysts project that deployment of VoIP-only solutions will outstrip traditional TDM-based PBX solutions within the next three years.

Parallel to the adoption of VoIP has been the enterprise acceptance of 802.11b wireless LANs (WiFi). With the availability of inexpensive high-rate (11Mbps) wireless data infrastructures, businesses from enterprises to SOHO have recognized the value in this technology and have begun deploying wireless solutions.

Strong acceptance of both WiFi and VoIP by the enterprise signals the possibility of a new market offering not previously possible: WiFi Telephony, or WiFi Voice over IP, solutions. WiFi devices are �standard� network devices attached to the hard-wired network via wireless base stations (�access points�), while offering the mobility of wireless handheld devices. Development of a marketable WiFi telephony solution can now become a reality.

While technologically possible, offering a robust wireless telephony solution may not be as simple, as it might seem. There are many non-obvious considerations to be made in developing such a solution. This is the first of several articles focusing on WiFi telephony and discussing the issues of implementing popular call control protocols in light of wireless specific requirements.

Market LANscape

One of the first questions to ask is: �what drives the market for a WiFi telephony product?� The answer is that there are real requirements for mobile telephony capabilities found in a broad spectrum of industries. Whether retail, healthcare, hospitality, transportation, or logistics, in the absence of a WiFi solution, many in these market segments have deployed wireless solutions consisting of everything from cordless phones (single base stations), to PCS cellular phones, to proprietary RF solutions -- at the rate of 200,000 phones per year. The benefit of a WiFi telephony solution in these markets is:

It provides a converged solution on a single RF network. Both voice and data coexist on a single RF network that is simpler to deploy and manage. Strong ROI results can be realized in this �single-network� approach.

It provides the best approach to guaranteeing seamless �in-building� wireless coverage. Single cell solutions and PCS (in-building-WWAN) have limitations in providing optimal coverage.

Driven by these value-add benefits, you will find these WiFi telephony solutions available in today�s market:

� Embedded WiFi devices -- There are two currently on the market. It is expected that additional embedded WiFi telephony solutions will be offered during CY-2003.

� Softphones -- Many telephony vendors are offering software telephony solutions that can be run on today�s high-end wireless PDA devices.

While these mobile WiFi offerings are available today, the total solution set is somewhat complicated and disjointed. Not all solutions utilize the same call control protocols and may or may not provide for simple integrated solutions. Each vendor has approached the WiFi telephony solution slightly differently and is somewhat bound by the selected call control protocol.

Protocol Alphabet Soup

A �call control� protocol is a layer-3 protocol that typically manages call setup, call monitoring, and call termination. The most popular international standard protocols are:

  • ITU H.323 -- Perhaps the most mature call control protocol and the predominant call control protocol implemented in VoIP solutions.
  • IETF Session Initialization Protocol (SIP) -- Emerging standard challenging for predominate call control, but still evolving.
  • ITU H.248/Megaco -- Another international standard that has been defined and implemented by a number of vendors.
In addition to the international standards defining call control protocols; there are a host of vendor-specific proprietary VoIP protocols that have evolved. This is due to the fact that the standards don�t address all the functional requirements necessary to support an IP-handset. These extended features include facilities for controlling the phone display and keypad for management of specific functions accessible by the user. Some of the most popular vendor solutions are:
  • Cisco�s Skinny Client Control Protocol (SCCP) �Base control protocol for Cisco�s AVVID VoIP solution.
  • Nortel�s UniStim - Base protocol used in support of Nortel�s 2004 IP phone solutions.
  • Mitel�s MiNET - Base protocol used in support of Mitel�s ICP IP PBX solutions.
  • Alcatel�s UA - Base protocol used in Alcatel�s IP PBX solutions.
  • 3Com�s H3 - Base protocol used in 3Com�s NBX IP PBX solutions.
Subsequent articles in this series will begin to detail some of the additional challenges related to supporting popular call control protocols over WiFi networks.

Richard Watson is director of telephony product marketing for Symbol Technologies� Wireless Systems Division in San Jose, CA. Prior to taking on the marketing role for Symbol�s NetVision family of WiFi Telephony products, he managed the software engineering team for three years and was responsible for developing Symbol�s WiFi Telephony products.

[ Return To The January 2003 Table Of Contents ]

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