IMS network architecture has been around for a long time. While it was originally conceived for mobile IP networks, it first gained acceptance in wireline IP networks, such as cable networks. To date it has had spotty acceptance in the mobile arena. All this is changing. But why now?  Dialogic (News - Alert) has a unique perspective on that since it provides both next-generation network and IMS network infrastructure.

The NGN infrastructure is in the form of softswitches, gateways, and media servers, and the IMS network infrastructure is in the form of media gateway control function, media resource function, and various other gateways. We’ve seen that various factors come together to enable IMS deployments. In a nutshell, though, I would say that common sense and practicality have reigned supreme. Imagine that.

One obvious factor is the emergence of LTE (News - Alert) networks. In fact, more than 300 LTE networks have been deployed worldwide so far, with hundreds more planned. LTE networks are essentially IP networks, so it makes sense that IMS would be the network architecture best suited to roll out an LTE network. So implementing an IMS network in this case clearly makes sense.

However, there is another very important reason that seems to have been somewhat overlooked. Many IMS deployments are occurring because the NGN architectures that were deployed in the early 2000s are now in need of an upgrade. Yes, the NGN is no longer next-gen. The equipment is getting old and needs to interoperate with newer networks to survive. We have seen instances of NGN softswitches that are now out of service being replaced with our more modern C4 switches that have IMS capabilities, because the communications service provider wants to bridge the existing network with newer IMS networks. You can think of this as some kind of hybrid IMS deployment. 

We have also seen older media servers in the form of board-level solutions being replaced with software-based MRFs. The application might still be a network voicemail (which could now include network video mail), but the media server architecture supporting the application can be more of an IMS architecture, where the app server and media server can be remote from each other. These MRFs can operate in full IMS architectures as well as NGN architectures.

In other words, CSPs are indeed going ahead and strategically replacing their circuit-switched equipment with packet-switched technology (including softswitches, media servers, and session border controllers) in an effort to reduce costs and converge voice, data, and video communications into richer multimedia sessions using the session initiation protocol standard. And the packet-switching architecture of choice is IMS.

It’s also important to underscore that co-existence and phasing is vital in many of these deployments where VoLTE/IMS networks, IP-based NGNs, and circuit-switched networks not only continue to coexist, but are also poised to do so for many years to come. However, it will require interworking between these different network architectures. The need for interworking across multi-generation networks through an IP-based foundation is something that the industry has long anticipated, and the new IMS architecture seems to be the appropriate solution. IMS provides a network model that addresses two key considerations facing CSPs as they migrate to modern networks: The delivery of converged media-rich applications over packet-switched, all-IP networks, and

the critical interworking needed to support voice communications between 4G LTE, 3G, 2G, and fixed legacy and NGN networks

The outstanding challenge for these CSPs is managing this migration without incurring high costs or disrupting customer service. In a market climate where the average revenue per user is either flat or growing at a minimal rate, and where low-cost or free over-the-top communications applications are eroding market share, the prevailing sentiment is often that CSPs need to manage their migration carefully and leverage their existing network assets for as long as is practically possible. CSPs are looking for a smart approach that will provide a seamless transition from legacy to NGN to IMS/VoLTE.

This is what I call smart IMS. These CSPs are using IMS to solve multiple problems at once. They are leveraging IMS without implementing a forklift network upgrade approach. In other words, they’re using a smart migration strategy that allows them to leverage NGN network elements through built-in IMS capabilities and migrate the rest of the network over to IMS as their capex allows. An additional advantage is that many of the IMS solutions are currently either software-based or at least running on COTS architectures, enabling them to more easily migrate to network function virtualization initiatives as they get rolled out by the industry.