As mobile data usage moves to mainstream, demand for uninterrupted service connections is escalating. At the same time, operators struggle to cope with the conflicting requirements of accommodating surges in traffic growth and controlling capacity expansion costs. Multi-radio mobile devices (such as 3G laptops, iPhone, & smartphones) offer the option to connect to services and the Internet by two or more wireless networks, but the user must access and subscribe to each network separately and connections cannot remain open as the user moves in and out of network range. This fragmented experience erodes customer satisfaction, while operators lose the opportunity to leverage multiple networks to optimize revenues.

Uninterrupted voice, video and file transfer at 60 km/hour

KT successfully performed uninterrupted handover of a mobile data session between 3G, Wi-Fi, and WiBRO/WiMAX networks. The results were achieved by integrating software developed by KT Central R&D Laboratory, and Stoke's SSX-3000 multi-access convergence gateway. The solution uses MOBIKE, a standard protocol defined by the IETF that enables secure connection management while the mobile device changes access networks. The implementation is an overlay solution that does not require reconfiguring or changing any of the intermediary network elements -- no matter which wireless networks are involved.

"We explored a number of different techniques for achieving media-independent handover. In the end, Stoke's SSX-3000 Multi-Network Mobility Anchor capabilities, together with KT's own client software, enabled uninterrupted video, VoIP, and file transfer on a laptop while driving at 60Km/hour, managing sessions between WiBro & HSPA networks," said Hyung-Keun Ryu, Director, Wireless Technology Department at KT. "The SSX-3000 Mobility Anchor is purpose-designed to deliver very large volumes of secure subscriber sessions over different access networks and, with its high capacity throughput and small form factor, is ideally suited for this requirement."

For mobile data services, one size does NOT fit all

Some wireless technologies perform better than others depending on circumstances such as location inside or outside a building, and each network has specific cost characteristics. As an example, spectrum allocation for today's 3G cellular network services means that service coverage inside buildings is unreliable, and very expensive to build out and maintain. Wi-Fi is relatively inexpensive, is virtually ubiquitous in the workplace, retail, homes, and in public spaces, but quality and coverage are variable. Fourth generation WiBro/WiMAX networks offer higher-speed data services at a comparatively lower cost, but deployment is currently geographically limited, although expected to expand.

Stéphane Téral, principal analyst at US research firm Infonetics Research ( www.infonetics.com ), commented, "Mobile subscribers are increasingly in range of more than one broadband wireless network, including Wi-Fi and 3G, with LTE and WiMAX just on the horizon. Stoke's Multi-Network Mobility Anchor provides operators the means to ensure a seamless user experience while optimizing traffic demand and costs across all of the wireless networks available to subscribers. This capability will improve the user experience by using the best available connection, improve broadband service coverage at a very low cost to the operator, and can improve operator data services profitability by offloading their cellular infrastructure."

"Mobile data subscribers care more about being connected than which network they are using, but currently they are forced to notice since their services are interrupted as they move," said Vikash Varma, president and CEO of Stoke. "For operators to rely on a single network to ensure total coverage does not make sense technically or financially. These trials demonstrate to operators that a major barrier to convergence has been removed and signals that KT's convergence capabilities are placing KT at the forefront of mobile data services."