CSL's Next G, the Shining Star in Hong Kong

2009-12-22     Yan Haibo, Zheng Hong

On 30 March 2009, the commercial promotion conference titled “Tomorrow’s Technology >>> Today” was held jointly by CSL, the largest mobile operator in Hong Kong, and ZTE in the Exhibition Center in Hong Kong. This conference symbolizes the commercial launch of Next GTM, the fastest all-IP mobile broadband network in the world.

Next GTM supports a maximum download data rate of 21Mbps. Its mobile broadband services are characterized by the most extensive coverage, the highest data rate, and the most reliable performance of any broadband available. “The launch of Next GTM reaffirms CSL’s position as the leading mobile network operator in Hong Kong, demonstrating our ability and commitment to bring the most advanced mobile communication technologies and applications to Hong Kong. We believe that the fastest speed, superior capacity and quality of our network are what differentiate us from the competition and enable us to exceed our customers’ expectations,” said Tarek Robbiati, CEO of CSL at the launch ceremony.

Just one year ago, CSL was confronted with serious challenges. Competition for the mobile telecom market in Hong Kong was extraordinarily fierce. Competitors with market shares lagging behind CSL were launching 3.6Mbps and 7.2Mbps HSPA data services to the market one after another, while CSL could only offer HSDPA data rate of 1.8Mbps. Moreover, CSL operated four networks of two modes (GSM/WCDMA) and three frequency bands. To upgrade the networks, CSL had to pay costly fees for software/hardware upgrade and engineering service, and the upgrade needed be accomplished within a very short period. Under such circumstances, CSL decided to choose a new vendor to help them replace the existing infrastructure and combine the four networks into one network that supports HSPA+ and the evolution towards LTE. This would resolve their predicament and restore CSL’s leading position for future development.

After an in-depth technological exchange, an onsite survey, and a comparison of solutions from different vendors, CSL eventually selected ZTE’s SDR based Uni-RAN solution that can combine multiple networks into one network through software radio technology so as to greatly improve network performance. The solution uses ZTE’s SDR base stations to replace the 2800 base stations in the network.

The implementation of the solution was divided into three stages: In the first stage, ZTE used the SDR base stations to replace the existing WCDMA equipment operating in 2100MHz and constructed some new base stations; In the second stage, ZTE swapped all GSM equipment operating in GSM 900MHz and 1800MHz and deployed a 900MHz WCDMA network; In the third stage, ZTE upgraded the network into the one supporting 64QAM and MIMO, and deployed a high speed wireless network evolvable towards HSPA+ and LTE.

The Most Complicated Wireless Environment, the Fastest Engineering Construction

As the most prosperous economic entity in the world, Hong Kong is famous for its skyscraper forest and numerous downtown areas. The environment for wireless networks here is extremely complicated, bringing about tremendous challenges in wireless network construction. Hong Kong government’s approval procedures for property related construction are very mature, well regulated, and stringent. The property related tasks, including site entry, site acquisition, engineering survey and design, and construction permission acquisition, are indispensable to the overall project. These four tasks should be approved one by one rather than concurrently. As the partner of CSL, ZTE was responsible for the turnkey project. To guarantee the successful delivery of the project, ZTE transferred 1500 experienced engineers from around the world and hired dozens of senior project management experts especially for this project.

In the existing network, CSL adopted 2G/3G co-site construction. During the swapping process, the equipment in the existing network had to work for a certain period of time. Therefore, there was insufficient space in the equipment room for new network equipment. According to the SDR solution, the project adopts distributed BBU+RRU base stations, without occupying any equipment room. As a result, this networking mode substantially improved the utilization of equipment room and facilitated site acquisition and property negotiation.

At the same time, CSL definitely required that the RRU should be installed outdoors and near the rooftop for the purpose of reducing the loss in the feeder antenna and improving network coverage quality. In the actual engineering construction, the rooftop RRU is usually 8–10 floors away from the indoor BBU, and the average distance between the RRU and the BBU exceeds 60m. Therefore, the BBU is connected to the RRU through an optical fiber to reduce the loss in the feeder and the cost of the feeder antenna. According to the actual network test, the newly-constructed 3G network adopting BBU+RRU distributed base stations can increase its network coverage quality by 5 to 6 dBm.

To reduce frequent handoff and improve network key performance indicators in the densely populated urban areas, CSL adopted ZTE’s innovative multi-RRU cell combination technology and tackled many coverage problems, for example, coverage in a complicated environment, internal coverage in large buildings, and the coordination between internal coverage and external coverage. As a result, the coverage quality of the overall network has been improved considerably. To provide coverage for scenic spots in mountainous areas, the engineering team even used the helicopter to carry the materials necessary for quick project delivery.

After 12 months of hard work, CSL had finished swapping, constructing, commissioning, and optimizing more than 2000 2100MHz WCDMA base stations in the frist phase of the project. The Next GTM network built in a record of only 12 months is a miracle in the network construction history of Hong Kong.

With the commercial application of Next GTM, the swap of users from the existing network to the new network was the next common challenge facing CSL and ZTE. After adequate discussion and sufficient analysis of the existing network, CSL adopted ZTE’s network cutover and user swap scheme for smooth network cutover, uninterrupted service provisioning, and high service quality. To realize these objectives, CSL and ZTE spent half a year on solution experimentation and testing, involving a thousand test items.


After careful and comprehensive preparation, CSL started to migrate its users to the new network in April 2009. On April 11, the first batch of 30,000 users were successfully cut over to the new network; On April 24, all prepaid users, a portion of postpaid users, and corporate users were successfully cut over; On May 23, the last batch of users were successfully migrated to the new network. So far, CSL’s 400,000 3G users have been completely migrated to the SDR based Next GTM. CSL’s CTO Christian Daigneault highly praised ZTE for its achievements, “We have been operating wireless networks in Hong Kong for a long time. Our networks involve a wide variety of terminals, bringing many troubles to the network and user cutover process. ZTE’s cutover scheme was very suitable for CSL that can allow every user of CSL to be migrated to the new network without their knowledge.”

SDR Based Green HSPA+ Network

SDR is not just a technological innovation but a revolution in the development of mobile broadband network. CSL is the first mobile operator in the world to adopt the SDR technology. CSL’s selection of SDR not only embodies its unrelenting pursuit of advanced technology and excellent network quality, but also indicates its accurate forecast of future technological development trends.

CSL’s Next GTM can improve the HSPA capability of the overall network (14.4Mbps HSDPA and 5.76Mbps HSUPA). The actual tests showed that Next GTM reached an average HSUPA data rate of over 4.5Mbps in the outdoor vehicle-mounted condition, an outdoor average HSUPA data rate of 1Mbps, and an indoor average HSUPA data rate of 3Mbps, each of which is much higher than that of networks provided by other operators. In the beginning of 2009, CSL successfully upgraded its Next GTM to support HSPA+ that can increase the data rate to 21Mbps. This successful software upgrade made Next G GTM the fastest mobile network in the world and enabled CSL to regain its leading position in the telecom industry. Currently, in CSL’s 1010 specialty store, users can enjoy the services of the fastest mobile broadband network in the world. Through the “HP connection manager” terminal, users can experience 15.27Mbps downloading.

In June 2009, CSL announced the successful cutover to the world’s fastest SDR-based HSPA+ commercial network. By adopting energy-saving SDR base stations and intelligent temperature control technology, and reducing the load on the power system, air conditioners and ventilation system, CSL has reduced the yearly energy consumption of the overall network by 39% and the emission of carbon dioxide by 7,187 tons, equivalent to the emissions from 1,000 automobiles in 3 years over 60,000 km. This green network not only reduces operational costs but also highlights the courage of CSL in shouldering social responsibilities.

Due to the advanced technologies and excellent performance of the Next GTM network, CSL and ZTE jointly won the National Mobile Services Award at the Global Telecoms Business Innovation Awards Ceremony held in London in June 2009.

In September 2009, ZTE and CSL revealed details of their plans to expand the Next G GTM network capabilities with the roll-out of UMTS in the 900MHz band and the building of a 4G or LTE network in Hong Kong. In a successful live demonstration of new LTE technology, they demonstrated the fastest mobile speeds in Hong Kong with peak download speeds in excess of 100Mbps. This successful trial of LTE technology confirms CSL and ZTE’s position at the forefront of the global mobile communications industry.

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