One of the major impediments to the progress of cellular services is the slow path to inter-operator roaming. The complex issues include billing, customer ownership and cross-payments. GSM only became a real success once roaming had taken off. For WiMAX to achieve broad uptake on an international scale, roaming challenges should be addressed at an early stage. WiMAX roaming challenges are actually no different than the challenges operators faced in 2G and 3G.

The first challenge for WiMAX roaming is interoperability. In order for users to access WiMAX services outside of their operator’s WiMAX network coverage area, devices must be interoperable across other WiMAX networks and between various vendors’ equipment. The WiMAX Forum has programs in place to help certify devices, which helps to ensure interoperability. The WiMAX Forum is aiming to have certified 2.3 GHz Mobile WiMAX products out in the market early next year, to add to the existing certified products at 2.5 GHz and 3.5 GHz. This will help widen the roaming footprint to include Korea and Malaysia. 2.3 GHz license awards are also in the pipeline in India.

The second challenge for WiMAX roaming is that of multiple WiMAX air interface profiles. Operators do not necessarily have the same frequency bands available within their respective geographic regions. Depending on the country, carriers may use different radio bands for their WiMAX networks, such as 2.5 GHz or 3.5 GHz, and client devices may be equipped to use only one of these. The WiMAX industry is in need of devices that support multiple bands. This was a challenge for previous generations of technologies as well, and was addressed by the availability of dual band, tri band and quad band devices. The same is expected to happen within the WiMAX space to address frequency challenges.

Another challenge surrounds the concept of “bill shock.” On the domestic level, this is what happens when a customer grossly overuses their data applications without an appropriate data plan; internationally, bill shock is often caused when users underestimate the roaming charges involved in data usage. With a voice only plan, a roaming subscriber is aware that there will be surcharge for every minute spent talking. For a data plan however, a subscriber is not able to track the data being transferred while running different applications like voice or video chat. A mobile device may be transferring data in the background unbeknownst to the subscriber.

In the EU, governments have eliminated bill shock by requiring service providers to warn customers when they have gone over their data and minute limits. There is speculation that this legal precedent will be copied internationally, prompting widespread industry response to solve this problem. For WiMAX, it is important to leverage the lessons learned from 3G regarding bill shock as a catalyst to provide more transparency around data usage.

Lessons learned from the previous generations of technologies can be applied to WiMAX to avoid the same pitfalls. In fact, these lessons are beginning to be accounted for within the WiMAX standards community, where there have been a fair number of roaming initiatives. Clearwire, UQ Communications and Scartel (Yota) have an MOU for international roaming. These operators are starting to look at roaming as another revenue channel. For instance, Clearwire will continue to work with its global partners, including Malaysia's YTL Communications, Pakistan's wi-tribe, Taiwan's Vee Telecom, and Global Mobile on steps to facilitate roaming.

The six WiMAX license holders in Taiwan are working towards national roaming to ensure they have full coverage of the island; they will be following up this initiative with international roaming. The northern and southern WiMAX operators in Taiwan have provisional roaming agreements in place to make WiMAX coverage nationwide. However, they all had hoped to have WiMAX services up and running at various points by the end of 2008, but postponed launches until sometime later this year. Tatung president Peter Yen revealed to Maravedis that he would like to see other WiMAX operators move faster in their launches to improve overall service coverage. He further explained that Tatung needs more coverage so its subscribers can roam anywhere in Taiwan without losing service. Korea Telecom has plans to establish roaming services in 2009.

Clearwire and DigitalBridge (DBC) in the US are involved in a trial roaming partnership with Intel. In doing so, they are helping to flush through some of the early adopter type problems that operators may face. Cisco and Alvarion are participating in the roaming trial by virtue of supplying DBC’s ASN gateway and BTS respectively; Cisco also supplies DBC’s AAA server. On the Clearwire side, Motorola’s BTS and ASN gateway will be used in the trial, while Bridgewater supplies the Clearwire AAA server. The clearinghouses involved in the trial are: Aicent, Comfone, Mach, Syniverse, and Transaction Network Services. The wireless IP clearinghouses take care of billing, clearing and settlement processes. The clearinghouse also settles the account with all the network providers involved in the service on a regular basis. As a result, the wholesale providers can deal with just one point of contact and one invoice, rather than having to settle separately with all those parties involved.

For more information you can contact the author at basharat@maravedis-bwa.com

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