Pioneering and Leading 4G in Hong Kong

Successful Practice of EPC Key Technology in CSL, Hong Kong

As the leading mobile operator in Hong Kong, award-winning , CSL offers  advanced technology, innovative services and superior customer  experience. After launching the world’s first commercial dual band 4G LTE/DC-HSPA + mobile broadband network in November 2010, CSL continues to achieve  , international LTE roaming, IPv6 deployment, MME POOL and the tdemonstration of the IMS-based High Definition.

VoLTE (Voice over LTE) service with HD calls on its existing LTE wireless network.These have greatly enhanced customers experience , at the same time contributed to the development and improvement of EPC core network technology.

Fully-Convergent Network, Low-Cost Operation

In 2008, according to an in-depth  analysis about the state of complicated network, CSL decided to adopt a unified platform with large capacity to build fully-convergent network architecture. After introducing ZTE’s convergent NE products, uMAC (SGSN/MME), xGW (GGSN/SAE-GW) and USPP (HLR/EIR/HSS), CSL changes original 3 separated TDM core networks into one end-to-end All-IP convergent network that not only supports GSM and UMTS, but also supports LTE access.

This successful network reconstruction not only provides solutions to high network maintenance overheads and limitation to upgrade smoothly, but also reduces network operation costs.

Continuous Innovation -Building a Leading VoLTE

With the coming of global LTE upsurge, how to generate benefitsfrom LTE network is under spotlights, and VoLTE is considered as one of key service functions that shows the value of LTEquickly. VoLTE is the general technical name of the voice and video services based on LTE network architecture, and it is the revolutionary evolution of traditional CS voice/video/SMS services. Communication vendors are fiercely competing for this.

During the 2010 Hong Kong Mobile Asia Congress, CSL together with ZTE presented the scenario of an LTE mobile phone installed with IMS soft terminal  for  VoLTE service. In 2011, CSL, together with ZTE again, promoted the CSFB (Circuit Switched Fallback) based commercial LTE voice solution. This solution falls voice call back to the 3G CS domain for procession, and only uses the LTE network to provide data service.. At the beginning of 2013, based on the IMS technology, ZTE successfully achieved the HD voice call continuity in eSRVCC (Enhanced Single Radio Voice Call Continuity) switchover environment, and interworked with the 3G HD terminal in the existing LTE wireless network of CSL.

International Roaming between HK and Korea

Hong Kong and South Korea are both developed areas in Asia, and people of the two areas interact and contact frequently. According to statistics, in 2011, there were more than 1 million people visiting Hong Kong from South Korea, while there were 30000 people visiting South Korea from Hong Kong each month. To enable LTE customers of the two areas able to seamlessly enjoy LTE networks and superior customer experience, in June 2012, CSL and SK Telecom, the key mobile operator of South Korea, achieved the first international LTE roaming service in the world. To help  CSL to achieve international roaming between Hong Kong and South Korea, ZTE, the EPC equipment vendor of CSL’s LTE network, successfully completed the integration and interworking among all EPC NEs and the network and terminals of SKT, and the design of roaming architecture. ZTE fully presented the openness and maturity of its EPC NE interfaces, and its leadership in EPC networking design.

IPv6 Expanding User Development Space

In this mobile broadband age, customers are always online and keep efficient contact with outside. The feature of using various applications  by mobile broadband at anytime and anywhere requires each user having 1 IP address at least. The shortage of IPv4 address resource limits the development of new customers and new service in LTE network. .

To tackle this, CSL together with ZTE adopts IPv6 technology in the EPC network. The 128-bit IPv6 address has almost infinite address space, so the development of new user and new service will not be subjected to address space constraints. As IPv4 networks and applications are now applied widely, IPv4 and IPv6 networks will coexist for a long time. ZTE EPC NEs adopt IPv4/IPv6 dual stack technology to allocate IPv4 and IPv6 addresses when users access the EPC network, so that users can access IPv4 network as well as IPv6 network with IPv6 addresses. For the terminal only supporting IPv6, it can access IPv4 resource through 6in4 or 6to4 tunnel technology.

MME POOL Building Highly-Reliable Network

One characteristic of EPC network architecture is “Separated Control and Bearer Planes”. MME (Mobility Management Entity), the pure control plane NE in the EPC network, is the “Brain” of the EPC network. It controls user access, authentication and mobility. The increase of LTE customers and the rapid development of mobile Internet services are seriously challenging the signaling processing capability of MME. The soaring signaling load even causes network failure. For example, the 4G network of one big operator in North America has encountered several service interruptions, impacting smartphone and wireless hot spots users across the country.

To cater for the rapid increase of LTE customers and build a highly-reliable EPC network, CSL adopts ZTE’s MME POOL technology to maintain network reliability. MME POOL achieves NE redundancy, avoiding single point failure causing impact on user service; it uses SAE-GW selection policies based on network topology and priority level to balance service traffic and control NE load level. Besides, MME POOL significantly reduces the signaling load generated during inter-MME updating and handover, and improves customer experience when terminal moves.

Smart Pipe Achieve Refined Operation

Facing  the competitive  service environment in Hong Kong and various customized user requirement, CSL introduces ZOOMs (ZTEs Optimized Operation and Management Solution) in the EPC network to achieve optimized  operation of mobile broadband network.

Flexible Policy and Charge Control (PCC) solution, combined with powerful Deep Packet Inspection (DPI) function, is able to reliably identify hundreds of different service protocols used in CSL network. Together with combined dynamic and static policy configuration and dynamic release function, CSL provides differentiated charging and QoS policy control for different services and users.


The building of a fully convergent EPC network, continuous innovation technological advancement and solutions such as international LTE roaming, IPv6, MME POOL and ZOOMs, has set up a  leading  model for LTE/EPC network design, construction and operation in the mobile Internet age, contributing to CSL’s leadership in network, in one of the most competitive market in the world.

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