IMS (IP Multimedia Subsystem)

The All-IP network is the foundation of the IP Multimedia Subsystem. It can map and implement all communication services between various parties during switching and transfer. Although they are also used in fixed-line networks, IMS systems are predominantly used in mobile networks.

What is an IP Multimedia Subsystem (IMS)?

IP Multimedia Subsystem (IMS) is a standards-based architectural framework that enables the delivery of multimedia communications services like audio, video, and text messaging over IP networks. The 3rd Generation Partnership Project (3GPP) originally developed the IMS specifications to standardize the operation of future mobile networks.

The core network functionality necessary to supply multimedia communication services is outlined in the IP Multimedia Subsystem standards, along with the different parts in charge of delivering each feature and a well-defined set of reference interfaces to each component.

IMS allows operators to select the best components for each operational feature and prevent vendor lock-in while also ensuring their interoperability and interworking.

The highly decomposed network functions, outlined in the IMS specifications, neatly separate signaling and media services by using a hierarchical design approach. In contrast to the monolithic vertical scaling strategies used in current carrier infrastructures, this sets the framework for extremely effective, granular, horizontal scaling.

IMS Architectural Breakdown

There are three different layers that make up the IMS architectural framework: the service/application, control, and transport layers. These three distinct layers provide the tools required for managing traffic and signaling for multimedia applications.

• Service layer/Application layer
  Services offered to users (such as 4G/5G mobile networks, WiFi, or any other network infrastructure) are hosted and executed at the application layer.

• Control layer
  This layer is responsible for session control and management. By authenticating and allocating traffic (such as the Proxy-/I-/S-CSCF), the control layer manages the flow of information between the transport layer and the service/application layer.

• Transport layer
  This layer supports the architecture's core network by serving as a gateway between access layers and IP networks.

IMS Advantages and Benefits

IP Multimedia Services offer better flexibility and extensibility than conventional monolithic communications service provider network architectures by defining a layered network architecture with open interfaces. The benefits of IP multimedia services for service providers include:

• Application, network, and device independence
  The transport layer and applications are separated. Service providers can deliver common applications and services with unified authentication, authorization, and accounting across a variety of devices and access networks, including LTE mobile networks, Wi-Fi networks, fixed networks, and MSO networks.

• Standards-based solutions
  Service providers can reduce costs and vendor lock-in by using standards-based network elements.

• Service interconnection
  IMS offers standardized methods for connecting various networks operated by communications service providers and for facilitating smooth roaming across networks.

• Service diversity
  The IMS standards make it possible to use a range of IP-based communications services, such as phone, video, text chat, multiparty conferencing, and collaboration tools.

• Quality of service
  IMS enables policy-based QoS mechanisms to guarantee SLAs and provide seamless experiences for specific applications or across specific access networks.