Over the past few weeks we've been discussing fixed-mobile convergence from a number of angles, all primarily focusing on future technologies and ultimate solutions that we might see in wireless/wireline convergence and interoperability. This time we want to circle back on that discussion with a slightly different angle based on converging current generation cellular with IP telephony.

There's no doubt that cell phones and IP telephony are two of the essentials for most enterprises today. However, the convergence of the two had a less-than-obvious path. In general, the IP telephony installation is implemented and managed as an on-premise, internal project. By contrast, cellular service is provided by a service provider. And even though the feature sets of the two have some overlap, the features are usually implemented independently.

One approach to converging these two disparate entities is the emergence of the dual mode 802.11 and cellular phone. However, these devices are just entering the mainstream of the marketplace and they still may or may not provide the full feature set.

As an alternate approach, some companies, including Avaya and Nokia, are porting a significant portion of the IP telephony feature set to a cell phone. The general idea is that the specialized cell phone "homes" to the IP PBX network via the traditional cellular network. Once connected to the corporate network, the full (or at least a substantial subset) of the IP telephony feature set is available on the cell phone. Essentially, the cell phone becomes yet another off-premise extension of the IP telephony network.

This can provide some major operational advantages. For example, calls that are started on either the cellular phone or on the IP phone can be transferred smoothly without loss of significant features. An even more dramatic advantage can come in processing international calls. For most companies, the cost per minute for international calls over the IP network is minimal. At the same time, international calling plans for most cellular companies are still quite expensive. In this scenario, outbound international calls are simply routed to the internal IP telephony network, thus providing tremendous potential savings.

For more information on how the Avaya/Nokia solution works, there's a white paper available written by Avaya.  We're sure we'll also be hearing about other similar partnerships, and we'll pass along this information in a later newsletter.

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Larry Hettick is a principal analyst at Current Analysis.