IMS: Key in LTE Age

End users always expect to enjoy ubiquitous high-bandwidth services through their mobile phones. Mobile operators, in order to get an edge in the competition, are stepping into LTE testing and deployment stage with the purpose of providing high-performance, high-bandwidth and better user experience for their customers. They also hope to get an upper hand in operating LTE networks and services. In the next three to eight years, LTE will undoubtedly become an important enabler in the transformation of mobile networks.

The high bandwidth of LTE will result in rapid increase of packet traffic. Thus higher requirements are raised for operators’ network resource management, for example, how to implement policy-based resource management, and how to charge flexibly. The resource management, traffic control, DPI, and charging functions have transformed operators into “smart pipe” providers that have good service awareness. However, the operators are not satisfied to be considered as simple pipe providers. Most of them still hope to have control over services, play an even more important role in the value chain, leverage the advantage of managing large user data base, and generate more revenues from a variety of new service deployments.

IMS, based on SIP call control architecture, adopts the separation of media, services and control that enables fast deployment of all kinds of multimedia services through a flexible and open service platform. Its access-agnostic nature and resources control features provide the operators with sources of income from application services.

ZTE, a global leader in mobile communications, has rolled out its IMS solution for LTE access (see Figure 1) based on the years of experience in deploying Circuit Switched (CS), Packet Switched (PS), and IMS services.

ZTE is capable of delivering end-to-end IMS solutions including IMS core network, service platform, access, and operations support. It provides operators with network resources management as well as self-operating services. ZTE’s Resource and Charging Control Platform (ZXUN RCP) provides resource admission control, policy and charging control. When there is heavy LTE data traffic, ZXUN RCP can coordinate with ZTE’s Call Session Control Function (ZXUN CSCF) and ZTE’s Gateway (ZXUN xGW) to allow real-time services like voice and video to get the priority in using transmission resources, thus effectively ensuring the quality of LTE real-time services. The Session Continuity Application Server (SCAS) in Figure 1 is used to ensure the continuity of voice and other multimedia services with the existing CS services. This is especially important in the initial deployment stage when the LTE coverage is not so wide.

Multimedia Services over LTE

As a new wireless broadband technology, LTE boasts a wireless data rate comparable to the fastest one so far supported by the fixed broadband technology, which can greatly reduce latency and allow users to experience quality multimedia services on a real-time basis. In addition, the open structure of IMS also helps to shorten the time required for service deployment, facilitating operators to deliver feature-rich services.

Multimedia services are the key to attracting end users. ZTE’s IMS provides operators with an ideal architecture to deploy their own-controlled multimedia services and meanwhile it is open to other application developers that could bring more varieties of applications.

ZTE’s IMS solution can provide individuals and enterprise users with diversified services including high-definition video conference, video surveillance, three-screen (PC, TV and mobile phone) interaction, multimedia ring tone, and multimedia called ID. Apart from the services defined by the RCS Initiative such as Presence, Instant Messaging, Media Sharing, and Network Address Book, ZTE can also offer file sharing, click-to-dial, electronic whiteboard service, etc.

To work with Web 2.0, ZTE’s IMS system also offers open interfaces for application developer to use the call control, messaging, conference capabilities to integrate into their own applications.

With the launch and development of LTE mobile phones, multimedia services over LTE will definitely become the key to attracting users.

Voice Services over LTE

The high bandwidth, high mobility and low latency of LTE ensure that users can enjoy the same voice service over LTE as over traditional CS network. In the LTE specifications, the CS core network is no longer supported. Even though voice is not the key driving force for LTE, voice over LTE is a must because it is still the big revenue generator. Currently LTE uses the Single Radio (SR) mode, which makes it impossible to deploy services on both LTE and UTRAN/GERAN, so there are requests for voice handoff and CS access, especially when LTE is initially deployed as hotspot islands. One approach is to instruct an LTE handset to “fall back” to the CS network when a voice call is being imitated or received; another approach is Single Radio Voice Call Continuity (SRVCC), which uses IMS system to perform call anchoring and handover based on third party call control mechanism.

Backed by a sound IMS core network, powerful packet data service control units ZXUN uMAC and ZXUN xGW, and the Mobile Service Control Server/Mobile Gateway (ZXWN MSCS/MGW) supporting evolution to LTE, ZTE is capable of delivering complete voice and multimedia over LTE solutions, including the CS Fallback (CSFB) solution and the IMS-based SRVCC solution.

We believe LTE deployment will boost IMS market. The nature of IMS allows it to easily fit into LTE network and create rich services for end users. ZTE is one of the few vendors in the world that offer end-to-end IMS solutions. In September 2009, ZTE launched its brand-new ZIMS 2.0 solution, featuring full-service operation capabilities. It takes the lead in Chinese IMS market, with large-scale commercial deployments throughout the Chinese market. With numerous innovative and mature application cases, ZTE has been among the global mainstream IMS providers.