While I have long been a proponent of using wireless LAN to mobilize voice service in enterprise organizations, the first wireless service we see being used for mobile unified communications is cellular. When we weigh the availability cellular services against the challenges involved in upgrading a wireless LAN to support enterprise quality voice services, it is not surprising that most organizations choose the path of least resistance.

Fixed-mobile convergence (FMC) is the term we use to describe services that integrate cellular with other wired or wireless networks and provide the capability to hand off calls between the two environments. The original vision for FMC was built on the idea of having dual mode WLAN/cellular handsets and a solution that transferred calls transparently between the two wireless environments. However, the model of FMC that is first taking shape is one that combines cellular with traditional wired telephone service.

The most widely used FMC solution is what the IP PBX providers call simultaneous ring or extension to cellular. With this solution, incoming calls to a user’s wired business number can be rung simultaneously to their desk phone and to their cellular number; when the call is answered on either device, the ringing is stopped on the other. Some of the solutions also provide the capability for the user to manually transfer calls from one device or the other without interrupting the connection.

While these solutions fall short of the “grand vision” of fully integrated networks where calls can be automatically handed off the different environments, they do deliver the first line benefits of enterprise FMC:

1. Single Number Accessibility: The user can be reached at one number regardless of whether they are at their desk, in the facility (assuming you have decent indoor cellular coverage), or out of the office.
2. Single Voicemail: Any missed calls will be routed to a single voicemail (i.e. the PBX’s voicemail system).
3. Control of the Telephone Number: Most importantly, the business maintains control of the telephone number.

That last point is typically overlooked, but has the greatest management impact. Businesses that allow employees to receive business calls on their personal cellular numbers are taking a major risk. Simply consider, what happens if that employee leaves the company and goes to work for a competitor? If customers continue to call that number, they are calling a (possibly disgruntled) former employee, who now has a different product to sell.

For any employee who is dealing with customers, it is imperative that the business be in control of those communications. In particular, the customer must be calling a number that is owned by the company. One of the major advantages of a simultaneous ring/extension to cellular configuration is that the customer is always calling the employee’s business number; the cellular number is stored in the IP PBX but not visible to outside callers. When the employee leaves, their replacement’s number can be substituted in the IP PBX.

Maintaining control of the number also means that the employee should not call customers or other business contacts directly from their cell phone. With caller ID, the called party would be privy to the cell phone number on the first call, potentially circumventing the PBX on all subsequent calls. In short, if it’s “our business”, it should be “our phone number”.

Needless to say, there is a cost associated with this type of solution. Every incoming call that is forwarded through the IP PBX will entail:

1. A local outbound call from the PBX to the cell phone
2. An incoming cellular call
3. That call also ties up two trunks on the IP PBX (that configuration is referred to as “Hairpinning” or “Tromboning”)

The costs of calls originating from the cell phone are harder to pin down. While those calls would be routed through the IP PBX, the call can be originated from the cell phone to the PBX, or the PBX can call outbound to the cell phone. There are some important security concerns regarding how those calls are originated that we will investigate in another article. It turns out that routing outgoing cellular calls might actually save money, particularly if users are placing international calls. Calls routed through the PBX will be billed as originating from the PBX at wireline rates, rather than at the cellular carrier’s international call rate.

The other management advantage of routing cellular calls through the IP PBX is that the call detail recording can capture all of the cellular call activity. That allows better monitoring for unauthorized use, and that usage information may be critical in deciding which is the most cost effective billing option when it’s time to negotiate the next cellular contract.

Conclusion

Cellular spend is one of the most poorly managed elements in enterprise communications. Industry research tells us that roughly half of existing enterprise cellular usage goes over employee-owned cell phones with reimbursement handled through expense vouchers. That is not just uncontrolled spending, it’s uncontrollable spending. While enterprises weigh the benefits of one-number accessibility and resulting productivity improvements, the real justification for fixed-mobile convergence might be our ability to control our phone numbers and finally begin managing our cellular usage.