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Home LTE LTE Roaming An Interview on LTE Roaming with Laurent Dubesset, Roamware’s LTE Expert

An Interview on LTE Roaming with Laurent Dubesset, Roamware’s LTE Expert

Last week I caught up with Laurent Dubesset, Roamware’s Director of Technology and an industry renowned LTE expert. Here are excerpts from a conversation we had on LTE Roaming

With the LTE network count set to cross 200 in 2013, how big a focus is LTE Roaming going to be for operators?

I have worked to define the LTE roaming guidelines with other mobile operators within IREG PACKET group since 2009. Early in 2012, the guidelines were available but it was too soon at that time. Operators were not ready to start LTE roaming. IPX vendors were also not ready and have no LTE signaling offer to connect Mobile Operators. Since then I have seen a lot of activities in mobile operators and a lot of IPX vendors have announced officially they can interconnect LTE. LTE has been a reality in a lot of markets for more than 6 months and this is now time to start LTE roaming for them. I expect to see the first commercial LTE roaming agreements inside Europe but also between Europe, the USA and Asia by the end of H1 2013. Then the number of agreements will grow exponentially. 2014 will be the year of LTE roaming.

What are the challenges that an LTE subscriber can face in an international roaming context?

The first challenge for both subscribers and operators is the frequency band fragmentation. In the USA, Verizon, AT&T and other LTE operators have all deployed in different frequency bands: 700 MHz Upper C Block spectrum (Band 13) for Verizon, 700 MHz lower B’s and C’s (band 17) and refarmed AWS 1700/2100 (band 4) for AT&T. In Europe, you need to support the combination of three bands 2600 MHz (band 7), European Digital Dividend 800 MHz (band 20) and refarmed 1800 MHz spectrum (band 3). In Japan, NTT DOCOMO deployed in several bands (more than 4) but advises refarmed 2100 MHz (Band 1) as the main band for roaming. Some of the Asian operators also decided to deploy TDD LTE instead of FDD LTE.

Today there is no device supporting all necessary bands as well as FDD together with TDD technologies. Recently Qualcomm announced the release of a new chipset able to support all bands but it will take time before it is implemented in some devices and in all device market segments.

What are some of the technical challenges that operators face to ensure seamless LTE Roaming in multi-technology mobile ecosystem?

Operators need to build the international Diameter network over the IPX to interconnect the MNOs. They have to buy new equipment called Diameter Edge Agents. These are Diameter proxies with advanced security features like topology hiding, AttributeValuePairs filtering and even IPSEC support. They also have to purchase the LTE signaling transit service from one IPX carrier to avoid connecting directly to all their roaming partners.

Operators will also have to adapt the entire roaming VAS platform to cope with LTE including Network Traffic Redirection for Steering of Roaming (SoR) and Outreach Messaging for roamer communication.

Bill-shock is a major concern for LTE roaming. Due to the very high bandwidth of LTE, the bill-shock limit will quickly be reached. Some operators are thinking of a new wholesale business model for LTE (daily bundles). Some others want to lower down the prices on LTE compare to those on 2G/3G.

Last but not least, some networks have implemented the CSFB for voice, SMS and other Circuit Switched services. This is the intermediate solution before GSMA VoLTE. Some others directly jumped to VoLTE like Verizon as it is a former CDMA network. Roamers equipped with CSFB smart phones can’t roam on a VoLTE network and vice versa because the voice service would not be available.

 How do Roamware solutions help operators make the LTE Roaming seamless for subscribers?

There are numerous areas where Roamware solutions will ultimately help subscribers but I’d like to mention three of them:

Seamless is really the point. As mentioned above there are some networks or LTE accesses inside network where the roamer will not have voice service. Roamware’s industry pioneering steering of roaming solution – Network Traffic Redirection can make sure that the roamer is always on the best network and access and has voice service.

Today the architecture of LTE roaming is Home Routed that is to say the roamer is connected to his HPLMN. This model has some impacts on the service. The actual bandwidth is then limited by the round trip delay. Hence the subscriber may be disappointed by the quality of LTE roaming compare to the one he has in his own network. I think operators will quickly realize that and I assume the architecture will change to Local Break Out in one year or two. Roamware can help operators to implement LBO with the Local Internet Service solution.

Eventually, being an industry driver and thought leader, I am sure Roamware will find a proper solution to ensure interworking between CSFB networks and VoLTE ones.

To explore Roamware’s LTE Roaming solutions, please click


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