Adding Cell Phones to Your PBX

Businesses looking to bring mobile phones under the umbrella of their corporate voice systems have an array of options. They can keep their PBX (News - Alert) on-premises or they can go with an IP-Centrex solution. Similarly, they can get their PBX-to-cellular integration capability through an equipment vendor or through a service provider. This column looks at some examples of getting the cell phone integration from a service provider while keeping the PBX on-premises.

There are two basic flavors: first, extending the capabilities of the PBX over the cellular network; second, doing this plus using a dual-mode cell phone’s WiFi (News - Alert) connection to make VoIP calls.

Verizon’s PBX Mobile Extension service is an implementation of RIM’s Ascendant Mobile Voice System. This is one of a class of solutions that makes the cell phone behave like an extension to the corporate PBX, while still using only the cellular connection (never WiFi) to carry the call. Its primary benefit is that you have all the PBX features even when you are away from the office. RIM’s solution has the further benefit that this PBX functionality is built into the Blackberry user interface seamlessly, while competitive solutions of this type usually need add-on software in the phone. It lacks all the benefits associated with running calls over WiFi, like improved coverage inside the office, which benefits the customer, and network offload, which benefits the carrier. Using the cellular connection for in-office calls is normally more expensive than WiFi, but this example is a service provider offering; Verizon (News - Alert) may choose to meter on-premises calls differently than off-premises to mitigate this disadvantage. As for the improved coverage and network offload benefits of WiFi, soon femtocells may offer a carrier-oriented alternative. So it can be argued that WiFi would not be much extra help.

RIM is not the only company offering mobile network providers equipment that integrates cell phones with corporate PBXs; there are several, for example OnRelay (News - Alert) and Tango Networks, which (like RIM) have products that work with many different PBXs. Unlike RIM’s MVS, these products also work with cell phones from multiple vendors. But it is very tough to do an elegant user interface to PBX features that works on multiple handset platforms.

A few equipment vendors go the extra step of combining the benefit of PBX feature extension to cellular with WiFi calls, and add the further benefit of seamless handover of calls in progress between the cellular and WiFi networks. These vendors tend to focus directly on enterprise customers, but some, like DiVitas and Varaha, are also beginning to get traction with specialist service providers.

Michael Stanford (News - Alert) has been an entrepreneur and strategist in Voice-over-IP for over a decade.

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