A New Chapter for VoLTE

In late August 2014, ZTE enabled voice over LTE (VoLTE) for CSL’s customers in Hong Kong, delivering a superior voice and video calls. At the end of 2014, VoLTE had been activated for more than 1 million CSL subscribers so that they can use VoLTE on any compatible device.

Early Mover on VoLTE
Hong Kong’s mobile penetration is one of the highest in the world. With a population of more than 7 million, there are a total of 17 million mobile subscribers by July 2014, it pushes the mobile subscriber penetration rate to 236.2%. In addition, there are four mobile operators in Hong Kong and users may port their numbers to the other operators. This makes Hong Kong’s wireless market even more competitive.
CSL is Hong Kong’s leading mobile operator and has partnered with ZTE to commercialize the most advanced technologies and launch higher-quality mobile voice services. This helps CSL maintain its competitive edge in the wireless market.

The Way to Commercial VoLTE
ZTE has been engaged in continual discussion, cooperation and innovation with CSL on VoLTE from the beginning of 4G construction and has finally commercialized VoLTE on CSL’s network.
● In 2010, ZTE demonstrated the first VoLTE call based on CSL’s commercial LTE network at the GSMA conference.
● In 2011, ZTE’s CS fallback (CSFB) solution was successfully commercialized for CSL. CSFB allows wireless terminals to fall back to the CS domain to send and receive voice calls, while the LTE network carries the data service only. ZTE’s CSFB helped CSL speed up LTE commercialization.
● In February 2013, ZTE successfully demonstrated a HD voice call using enhanced single-radio voice call continuity (eSRVCC) on CSL’s commercial LTE network. The eSRVCC solution solves the problem of voice handover between 2G, 3G and 4G.
● In August 2014, ZTE enabled end-to-end VoLTE interconnection between the VoLTE networks of CSL and HKT. This gave Hong Kong’s mobile operators invaluable experience with interconnection.
● In late August 2014, CSL commercialized their VoLTE service. At the end of 2014, VoLTE had been activated for more than one million of their network subscribers.

Focusing on Customer Experience, Winning the Future of 4G Voice
With the rapid development of the 4G market, network quality is the key to measuring customer experience. ZTE draws on its rich experience with network construction worldwide to bring CSL’s end users a new VoLTE experience and helps CSL stay ahead of its competition and build the best brand.

Faster Voice Call Set-up
A call connection on a 3G network currently takes around seven seconds. Now, ZTE’s IMS-based VoLTE solution transmits voice packets through the LTE bearer network, which greatly shortens the call set-up time. During testing, call connection between two VoLTE users was as fast as one second. If a VoLTE user calls a 3G network user, the call connection is connected in around four seconds. This solution ensures a superior HD experience for CSL users.

Enhanced Video Call Quality
The HD codec technology in the VoLTE solution increases the sampling rate and reduces background noise to provide the end user with clear, natural, authentic voice. A video call connected using VoLTE has a resolution of up to 640 × 480 pixels. The picture is very clear—high-quality and without any grids. When a voice call is being processed, the user can switch the call to video with the click of a button. The user can switch back from video call to voice call in the same way. It is very convenient. This solution helps CSL differentiate its products and stand out from the competition.

Instant Switching between Voice and Video Calls
eSRVCC enables seamless handover from VoLTE to CS voice calls. When a user moves outside the LTE coverage area, the ongoing call is not interrupted. The user can enjoy VoLTE service anytime and anywhere.

Smooth Evolution to 4G
ZTE has come up with a creative solution for 3G to VoLTE evolution. The user can enjoy voice and video calls via the 4G network by using a VoLTE-compatible handset, such as Samsung Galaxy Note 3, iPhone 6 or LG G3, without changing phone numbers or cards and subscribing to 4G service. This solution enables CSL to implement VoLTE at maximum speeds and minimum cost and prepare for large-scale migration to VoLTE.

Together Stronger
With innovative, cutting-edge technologies and solutions, mature network deployment and delivery, and a customer-centered philosophy, ZTE will focus on improving network quality and creating the best network in Hong Kong. Meanwhile, ZTE will also begin interworking and roaming tests on VoLTE networks in other countries. CSL and ZTE are moving forward towards the common goal of giving the people of Hong Kong the best mobile voice service. 
(*) CSL Mobile Ltd., which was acquired by HKT Ltd. in May 2014