Leading 4G in Hong Kong: CSL’s Successful Implementation of EPC Technology

CSL is the leading mobile operator in Hong Kong and offers advanced technology, innovative services, and superior customer experience. In November 2010, CSL launched the world’s first commercial dual-band 4G LTE/DC-HSPA+ mobile broadband network. Since then, CSL has continued to push ahead with international LTE roaming, IPv6 deployment, MME pooling, and IMS-based high-definition voice over LTE (VoLTE). This has greatly enhanced customer experience and driven the development of EPC technology.

Fully Converged Network, Low-Cost Operation

In 2008, CSL analyzed its network in depth and decided to fully converge the architecture by introducing a unified, large-capacity platform. ZTE’s uMAC (SGSN/MME), xGW (GGSN/SAE-GW), and USPP (HLR/EIR/HSS) products were used to converge CSL’s three separate TDM core networks into an end-to-end, all-IP network that could support GSM, UMTS and LTE. The network reconstruction reduced network maintenance overhead and allowed for smoother network upgrades. It also directly reduced network opex.

Continuous Innovation: Leading in VoLTE

With the upsurge in LTE deployment worldwide, profiting from LTE networks has become important. VoLTE is considered one of key services that can demonstrate the value of LTE. VoLTE is a general term for LTE-based voice and video, and it represents the evolution of traditional circuit-switched services. Telecom vendors are fiercely competing over VoLTE.

At Mobile Asia Congress 2010 in Hong Kong, CSL and ZTE jointly demonstrated VoLTE using an LTE mobile phone with IMS soft terminal. In 2011, CSL again worked with ZTE to launch a commercial VoLTE solution based on circuit-switched fallback. With this solution, voice calls fall back to the 3G circuit-switched domain for processing, and the LTE network is only used for data services. At the beginning of 2013, ZTE used IMS technology to make a high-definition VoLTE call with enhanced single radio voice call continuity. ZTE also used IMS so that the CSL’s LTE network was interoperable with its existing 3G high-definition terminals.

International Roaming between HK and Korea

People from Hong Kong and South Korea frequently interact with each another. According to statistics, in 2011, more than 1 million Koreans visited Hong Kong each month, and 30,000 Hong Kong residents visited South Korea each month.

In June 2012, CSL and SK Telecom rolled out the world’s first international LTE roaming service. This service allows people from Hong Kong and South Korea to seamlessly use LTE networks in both countries without any difference in user experience. ZTE made all CSL EPC elements interoperable with SK Telecom network and terminals and designed related roaming architecture. This demonstrated ZTE’s leadership in EPC network design as well as ZTE’s ability to supply open, mature EPC interfaces.

IPv6 Expanding User Development Space

In the age of mobile broadband, more and more people have a permanent connection. Feature-rich mobile applications require a user to have at least one IP address. However, a lack of IPv4 addresses has restricted the expansion of LTE services and customer bases.

To tackle this problem, CSL has worked with ZTE to introduce IPv6 into CSL’s EPC network. 128-bit IPv6 has almost infinite address space, so services and customer bases can grow without constraint. Because IPv4 is still widely used, IPv4 and IPv6 networks will coexist for a long time to come. For this reason, ZTE uses IPv4/IPv6 dual stack in EPC elements so that IPv4 and IPv6 addresses can be allocated to users when they access the EPC network. In this way, people can access internet via IPv4 or IPv6 addresses. Terminals that support only IPv6 can access IPv4 resources through a 6in4 or 6to4 tunnel.

MME Pooling for a Highly Reliable Network

Separate control and bearer plane is characteristic of an EPC network architecture. The mobility management entity (MME) is the control plane element in an EPC network and is the brain of the network. MME controls user access, authentication, and mobility. An increased number of LTE customers and the rapid development of mobile internet services have greatly challenged the signaling processing capability of MME. A soaring signaling load may even cause network failure. For example, a 4G network of one big operator in North America failed and caused interruptions that seriously affected smartphones and wireless hot spots across the country.

CSL has adopted ZTE’s MME pool to cater for the rapid increase in LTE customers, to build a highly reliable EPC network, and to guarantee network security. The MME pool provides NE redundancy so that if a single point failure occurs, services are not affected. The MME pool has abundant SAE-GW selection policies based on network topology and priority level to balance traffic load. The MME pool can also significantly reduce signaling load generated by inter-MME updating and handover. This improves user experience when a terminal is moving.

Smart Pipes for Optimized Operation

CSL has taken into account the complex service environment in Hong Kong as well as various customization demands and has introduced ZTE’s optimized operation and management solution, ZOOMs, into its EPC network.

A flexible policy and charge control solution, combined with deep packet inspection function, helps CSL inspect hundreds of different service protocols in its network. With dynamic and static policy configuration as well as a release function, CSL can provide differentiated charging and QoS for different services and users.

Conclusion