The market thus far has overlooked the opportunity to apply unlicensed mobile access’ (UMA) proven consumer architecture to certain types of business, where its simplicity can be a strength and its advantages are clear-cut.

Thornycroft: Enterprises can make their own coverage using UMA.

When discussing fixed-mobile convergence (FMC) or unified communications (UC) with CIOs, you would typically begin by asking about the needs and aims of the organization.  If the enterprise needs instant messaging, integrated voice and e-mail and other enterprise-centric services to be available to traveling employees on their cell phones, it likely needs some form of UC.  Powerful but complicated, a UC deployment entails a number of difficult choices.

If, on the other hand, the company has an enterprise wireless LAN (WLAN) and wants to use it for voice services but with no PBX integration, there are immediate steps it can take.  Carrier-based FMC services that use unlicensed mobile access, such as HotSpot@Home from T-Mobile, are good alternatives to consider.

UMA is sometimes disparaged because IMS-based networks will use a pervasive SIP architecture, but GSM operators don’t have many IMS installations today, and UMA is a good fit for their current networks.  There are currently perhaps 1.5 million UMA phones in service, more than for any other form of FMC.

UMA allows a dual-mode phone (GSM and Wi-Fi) to detect a suitable Wi-Fi access point (AP) and connect to it, setting up an IPSec tunnel back across the Internet to the cellular core network, where a UMA network controller (UNC) translates it to interface with the existing infrastructure.  Thus authentication and encryption is based on the SIM card in the phone, while signaling is essentially GSM encapsulated in the IPSec tunnel.  Media streams are carried by VoIP within the IPSec tunnel, and converted in the UNC to the core network’s protocols.

UMA OVER WLAN
Originally targeted for the home user, UMA has much to offer organizations concerned about coverage, cost savings and data performance rather than UC features.  Any business with a WLAN and where normal cell phone features are all that users require is a candidate for UMA service.  Conversely, a business where the PBX numbering plan and features are central to communication will look to UC for a solution.

Companies will find it relatively straightforward to enable UMA over a WLAN, and the handsets themselves are only slightly more expensive than regular cell phones. To ensure compatibility, companies simply acquire dual-mode phones with UMA service from their carrier and re-configure their WLAN as required.

Once activated, the phone must be configured to work with the enterprise WLAN security.  Most WLANs advertise a guest network where the device is allowed to connect without authentication, but all traffic is routed outside the corporate firewall.  If only voice services are needed, this is an acceptable solution, and the phone should be configured to recognize and connect to the guest SSID.  If Web page – captive portal – authentication is used, this can be more complex, but for instance the BlackBerry can be configured with credentials for this.

SECURITY AND QOS
Most corporate voice and data users will want to connect to the corporate LAN, however, inside the firewall.  Enterprise WLANs today use Radius-based 802.1x authentication with 128-bit AES encryption, so the ideal would be for UMA devices to use the same protocol, and indeed, the high-end smartphones such as the BlackBerry are capable of this highest level of security, known as WPA2-enterprise by the Wi-Fi Alliance.  Various alternatives exist within WPA2-enterprise, but perhaps the most common is MSCHAPv2, where the phone is configured to recognize the WLAN’s X.509 certificate and then authenticate using user id and password, in exactly the same way as a notebook PC.

Another consideration is quality of service (QoS).  UMA devices implement the Wi-Fi Alliance WMM certification to ensure their voice traffic gets priority on the WLAN, and with 802.1p tagging on the IPSec tunnel for LAN priority, this is more than adequate for good voice quality.  The new UMA traffic may displace or delay existing data traffic, but the bandwidth required for voice calls is low – less than 180 kbps per call – and is unlikely to cause disruption unless extremely large numbers of phones are active on a single access point.

This brief overview shows how an enterprise can enable its employees’ UMA phones to route calls over corporate Wi-Fi and the Internet, while maintaining the security and integrity of the WLAN.  There are three main benefits from this arrangement.

First, the enterprise can make its own coverage.  If there are areas where employees want to make calls, but where cellular coverage is poor, the IT group can make sure there is Wi-Fi coverage and the problem is solved.

Second, data services, when connected to the WLAN, will be completely secure and much faster than cellular data, allowing mobility within the enterprise based on the UMA phone.

Finally, the enterprise will enjoy some cost benefits from using UMA.  These will be dependent on the carriers’ fees. For example, for T-Mobile’s HotSpot@Home service in the United States, companies pay for the cost of the UMA phone and $10/month, and all calls over Wi-Fi are free.  Of course, this is in the context of large buckets of nationwide calling minutes at low rates, but data service  and international roaming fees can both be avoided when in Wi-Fi coverage, and these can represent considerable savings for certain users.

Obviously, UMA service is not for every business.  There is no integration with the PBX, so PBX features and 4-digit dialing will not work –although, today many employees continue to use their cell phones while in the office.  By providing a true single-number, single-device service with no learning required of the employee,   the handoff from cellular to Wi-Fi is imperceptible, and features are unaffected by the connection method.  The service is commercially available in many countries, and easy for IT groups to set up.  For many businesses, it is certainly worth considering.

Thornycroft is a technologist with Aruba Networks.