BRIDGING THE GAP BETWEEN 3G AND LTE
BRIDGING THE GAP BETWEEN 3G AND LTE
Jim Machi is vice president of product management for Dialogic, where he is responsible for driving the overall roadmap and product strategy for the company. Jim has been recognized by Internet Telephony magazine as one of the Top 100 Voices of IP Communications and by VoIP-News as one of the 50 most influential people in VoIP.
There’s no doubt about it: mobile is mainstream. A recent report from ABI Research states that by 2014, the amount of mobile data traffic registered in a single month will equal the total data traffic during the entire year of 2008. As a result, mobile network operators are facing the realization that 3G networks in their current state are not equipped to sustain this level of growth. These service providers are looking to migrate to LTE and IP multimedia subsystem (IMS) to provide the bandwidth required to support subscribers’ appetites for data-hungry devices and applications.
As LTE rollouts occur around the globe to create faster networks, the need to interconnect with existing 3G, signaling system legacy (SS7) networks arises at some point along the way. The nature of a mobile subscriber is to move around, both physically and between network types, which means interactions with both 3G networks and 4G networks, and SS7 and Diameter protocols are bound to occur. Many mobile users just want to watch YouTube or log in to Facebook; others want to run mobile applications or conduct voice calls. But regardless of the task, all subscribers move around in one way or another, making the need to connect to various multi-protocol networks important for revenue generation. Additionally, carriers can proactively direct smart devices to Wi-Fi so they can offload data traffic from their cellular networks. Either way, providers need a method to bridge the gap between 3G and LTE networks so users can still use apps and carriers can monetize usage accordingly.
DIAMETER: THE TECHNOLOGY BEHIND LTE
Diameter is the accepted signaling protocol used to enable applications across IMS and LTE networks. The protocol serves as the engine of each app, allowing the device to authenticate and authorize apps and even signal when to charge the device when it’s roaming. Given the skyrocketing use of smartphones and tablets that are either now running on LTE networks or will be LTE-enabled in the future, Diameter signaling usage is expanding. It’s important to remember that interpretation of the Diameter protocol spec, like all specs, is open to interpretation, especially in the “early days” of the protocol’s deployment. As a result, I’ve read that there are currently more than 70 different variants of the basic Diameter protocol. As a result, service providers must consider solutions that connect the dots between all networks and protocols so subscribers see no gap in service regardless of Where they roam.
Within the IMS control and service planes, Diameter plays a major role in policy, charging, authentication and mobility management. For several years, mobile operators have relied upon SS7 as the international, standardized protocol to communicate globally between operator networks. Diameter is a peer-to-peer protocol that involves delivering attribute-value pairs (AVPs). Typically a Diameter message includes a header along with one or more AVPs. The collection of AVPs in each message is determined by the type of Diameter application, and the Diameter protocol also allows for extension by adding new commands and AVPs. Diameter enables multiple peers to negotiate their capabilities with one another, and it defines rules for session handling and accounting functions.
DIAMETER IN ACTION
Diameter also enables applications beyond just roaming from one type of network to another. For instance, applications enabling equipment identity register (EIR) functionality allow operators to control which handsets or devices can be used in their networks. For example, when a smartphone or tablet is lost or stolen, it can be disabled using EIR.
Since LTE uses Diameter as a signaling protocol, operators have a need for Diameter interworking solutions. This has given rise to the Diameter interworking function (IWF, which moved onto the center stage at Mobile World Congress this year.
It’s a critical element to enable the successful rollout of LTE and a seamless user experience across different networks.
HERE ARE SOME COMMON USE CASES THAT DEMAND IWF FUNCTIONALITY:
1. WI-FI INTERWORKING. Wi-Fi interworking requires signaling conversion from RADIUS to Diameter to connect the Wi-Fi network to the carrier’s central traffic management and charging systems. This allows carriers to offer subscriptions that combine mobile and Wi-Fi connectivity into a single bundle.
2. LEGACY NETWORK INTERWORKING. This is a typical scenario involving signal conversation from Diameter to SS7/MAP. This includes roaming between LTE and 2G/3G networks, as well as security hand-offs and location register subscriber authentication. As LTE access networks become more widespread, this roaming use case will be critical for LTE-legacy network interoperability.
3. IT INTERWORKING. This requires connecting the new Diameter-based systems, such as a PCRF or a Diameter signaling controller, to either SOAP or XML/HTTP so IT information systems, such as CRM and subscriber databases, can be used for policy and routing decisions.
4. LTE-TO-IMS INTERWORKING. On the surface, both LTE and IMS use Diameter, but interworking between these protocols is still required. In the VoIP world, just because SIP is on one device doesn’t mean it talks to another SIP device automatically. Different SIP versions might be used, or the vendors might have interpreted the specs differently, both of which result in poor interworking.
Perhaps the most important function for Diameter interworking is credit control application support, which is used for mobile payments, price inquiries, prepaid service charging, real-time service charging, and more. This enables a mobile device to easily pay for or charge for a unit of whatever the application is doing, whether it’s paying for something on the Internet with money, debiting either a unit of time or prepaid byte downloads, and more.
The 3GPP and GSMA have identified elements called Diameter routing agent (DRA), Diameter edge agent (DEA), and Diameter interworking function (IWF), which is more closely aligned to the interworking described above. Infonetics identifies the Diameter signaling controller market in a recent report with an almost 40 percent compound annual growth rate through 2017.
Given that these issues are real, how do service providers address them?
What’s required is a next-generation solution that connects the carrier LTE/IMS and policy control environment to existing 2G/3G/Wi-Fi and back office environments. Service providers must consider these various use cases and subscriber scenarios ahead of time and proactively bridge different technologies and overcome incompatibilities through configuration and existing market-ready solutions, not additional, costly research and development. Vendor partners with any-to-any connectivity solutions will help providers solve this challenge, and subscribers won’t even know what is happening in the background. They’ll just know it works.