When you are traveling abroad the last thing you want to worry about is loss of service from your mobile phone. And you also don’t want to start worrying about your next bill. Now that LTE (News - Alert) is here, why can’t you just enjoy fabulous data speeds while downloading or watching a video and forget about the costs. Wouldn’t it be great if you could simply enjoy the local culture, exotic cuisines, colorful scenes and sit back and chat, talk and video about all these with your friends and family back home?!!
Roaming, what’s that about really?
Many people don’t realize what roaming entails and what it means for both the user and the telco operator. Apart from the basic concept of throwing your smartphone or other devices in your carry-on luggage there is a lot of technology support their operation. Currently, there are over 100 networks live with 4G capabilities offering subscribers rich experiences while at home. Undoubtedly, 4G subscribers expect the same quality and level of service to continue while they travel abroad. However, if you would have looked “behind the scenes” even way before 4G, enabling roaming required SS7 supported signaling for just voice and text messages in visited networks. With the evolvement of 2G/3G data, these roaming capabilities have become even more complex.
For SS7- based roaming, there are some very good intelligent roaming solutions available. Many, if not most, operators use them. Typically they are based on so-called OTA (over the Air) mechanisms to remotely control the preferred visited network list. They are often enhanced with SS7-based network traffic steering. The OTA mechanism tells the SIM what is the order of network preferences for logging on.
Usually, the SIM memory for this list is limited, so that in practice, the selection of visited networks can change frequently. Therefore to direct the roamer’s selection, a network traffic steering mechanism is often used which ignores attempts of a roamer to locate a specific network that is not among the top preferences of the home operator, forcing the handset to select another network until it either gets to the preferred network or selects the second best available network.
This solution works because the signaling is sent back to the home network, enabling the home operator to decide the preferred network in real-time for each subscriber. Customers benefit as the best quality can be selected. However, the main driver behind this mechanism however, is that the home network can select the visited network chosen for the best negotiated price (even if this price can change on a daily basis in theory, but usually every few months contracts are agreed upon for a price per minimum volume).
One important note is that with always-on services, like Blackberry email push, once the visited network has been selected, there is minimal chance that the roamer can update to another network. The selected network is completely invested in keeping roamers hooked in. And typically this happens with high usage, always on, high value roamers.
Now we are entering the LTE/4G roaming era in which we have a fundamentally different situation. For the subscriber with a 4G smartphone, it doesn’t mean that much changes as the phone also supports the frequencies of the visited network. Operators want it to look simple and “just make it work.” The important technical change is that in LTE there is no longer use of SS7 signaling. Now Diameter is the chosen signaling protocol for mobility management (and for other functions like policy control, charging and more). Another major technical difference in LTE is that there is always a default bearer active, so that all smartphones/devices will be always on.
Diameter-based Intelligent Roaming
Take the scenario of a visited LTE network and assume the visiting customer has an LTE/4G supported device for that network. Also assume that there is a commercial LTE roaming agreement in place, and the roamer wants to use his smartphone just as he did in 3G technologies.
The GSMA (News - Alert) has defined how roaming for LTE should work commercially and technically. So in theory, there is nothing else needed other than implementing what the GSMA has defined. But now we get to the real unique value that can be added to the roaming experience. Here is how in a very intelligent way, the home network can remotely control the selection of the visited network by a specific subscriber. Here is how to force the device to reselect the network it originally selected, even overruling attempts by visited networks to capture the revenue generating customer.
In addition to what was already possible in an SS7 based network, where a specific device could be steered to register to a preferred network, now there are customer, device and service-aware intelligent roaming capabilities.
Since the intelligent roaming solution is configured as an application on the Diameter Agent functionality (DRA) that is required per GSMA guidelines (as per IR.88), it has full visibility of what’s going on in a specific device. It “sees” what services are being used and how “active” those services are. In other words, a network operator has real-time access to the signaling supporting policy control (typically Gx and/or S9 interfaces) and charging functions (typically Gy or related interfaces) while roaming. In addition, it has visibility to the service quality and the availability of all potential visited networks at any given moment. Simply put, we have a complete set of information to make the smartest decisions at any specific moment. So the operator can make decisions as to the best service selection for every roaming smartphone/device given all the business and operational alternatives available.
The criteria used to decide to which network to connect is a real differentiator for the home network. The different factors can range from best quality to best price. The home network now has the power to control the redirection of high value traffic. This is possible even following the initial selection of a visited network. So at any given moment the home network can decide to interrupt the active default bearer or any other active link. With this capability the home network has full control of the revenue it can generate on a specific visited network.
This capability of controlling the assigned traffic also allows the home network to negotiate a better price than when the home network will generate revenues almost at random for the visited network. With this capability, we’ve made a major jump in the roaming value chain. And keeping in mind that the global roaming market size is about 45 Billion (see reference1 by Visiongain (News - Alert)), the value of controlling the use of a specific visited network or minimize to use a specific network is huge.
Operationally speaking, when other traffic on the visited network, either generated by the visited networks’ own subscribers or by other visitors, cause the visited network to behave below a certain expected level, the home network can select an alternative network. In this way an operator can deliver a truly premium service to its own customers, according to the service agreements, customer and application experience for any individual customer, device and service.
By deploying a Diameter Router (DRA) with intelligent roaming capabilities in addition to the GSMA required Diameter Edge Agent (DEA) functionality, operators can benefit from real-time control of the user experience while roaming abroad. And this benefit continues regardless of the time or service used by customers and devices. Diameter signaling and its unique position in the network for total visibility make this possible.
1 Visiongain has determined that the value of the global roaming market in 2012 will reach $45.1billion.
Peter Nas serves as Senior Solution Architect at F5 Networks (News - Alert). Nas has over 20 years of telecom experience. He is a frequent speaker at industry conferences on the subject of signaling.
Edited by Rich Steeves