Hi3G: Leading the Era of LTE TDD/FDD Convergence

Scandinavia has a history of producing innovative operators and vendors. Many cutting-edge innovations, advanced communication technologies, and high-end communication services are conceived there. Swedish operator TeliaSonera launched the world’s first commercial FDD LTE network at the end of 2009; Danish operator TDC became the second  to deploy an LTE network in Europe in June 2010; and Swedish operator Net4Mobility deployed an LTE commercial network at the end of 2010.

Another Scandinavian operator, Hi3G, has the fourth largest market share in Sweden and Denmark. Its competitors have all deployed LTE networks, and this has greatly impacted Hi3G’s development. Therefore, it is imperative for Hi3G to launch LTE.

Many high-end operators are choosing traditional FDD mode. However, Hi3G believes that after FDD and TDD standards are converged, a 4G network with TDD will have the same quality as FDD but will be cheaper because of spectral resource efficiency. Building LTE TDD/FDD dual-mode networks is the best choice for operators. Hi3G has only 2 × 10 MHz in the 2.6 GHz band for FDD in Sweden and Denmark. This narrow bandwidth makes it hard to provide competitive data throughput in hotspots. Hi3G therefore has to consider using an LTE TDD/FDD hybrid network that can cater for high-rate data services and leverage existing spectral resources.

In September 2010, Hi3G put out a tender for an LTE TDD/FDD dual-mode network solution. Interoperability between LTE TDD/FDD and Hi3G’s existing UMTS was a requirement. Moreover, the LTE FDD network had to provide wide coverage, and both TDD and FDD had to be applied in the same hotspots. Later, the LTE TDD network would be further expanded to cover more hotspots. From equipment delivery to installation and commissioning, the entire converged network had to be completed within three months.

Early in the bidding, Hi3G selected two suppliers to build its LTE network in Sweden. As the project proceeded, ZTE stood out from the competition with its advanced LTE TDD/FDD dual-mode solution, multimode SDR platform, diverse base stations, customized transmission solutions, leading multimode terminals, and powerful project delivery and logistics capabilities. In March 2011, Hi3G selected ZTE as its exclusive LTE vendor.

ZTE’s TDD LTE/FDD LTE/UMTS multimode converged solution met the requirements for interoperability and load balancing between Hi3G’s existing 3G network and the new LTE network. The solution improved system security and stability and ensured network throughput in hotspots. With shared BBUs, antennas, GPS, transmission, OMC and EPC, the LTE TDD/FDD dual-mode network meant that site investment and network O&M costs were reduced for Hi3G, and the network was constructed quickly.

Because of system interference caused by co-siting the TDD LTE, FDD LTE, and UMTS networks, ZTE offered a co-antenna solution that was warmly received by Hi3G. ZTE used two-path broadband antennas that reduced interference between TDD LTE and FDD LTE through proper antenna isolation and customized combiners.

Hotspots require high network throughput. Hi3G has limited site resources and sought to make full use of their existing UMTS sites. Winter temperatures are very low in Sweden, and this places very high requirements on base stations in terms of capacity, size, installation flexibility, and performance. In response to these needs, ZTE provided different LTE base stations that could be used in different scenarios and perform well even at -40 degrees Celsius. ZTE’s FDD/TDD dual-mode SDR base stations, compact outdoor BBU cabinets, large outdoor BBU cabinets, and outdoor distributed base stations were combined in different arrangements according to the environment. The eNB can be installed indoors or outdoors, mounted on a tower, or under a tower. This helped Hi3G save on engineering, alleviate installation difficulty, and speed up network construction.

"we have chosen ZTE for an additional 3G 900/2100 rollout and for LTE mobile broadband networks in Sweden because of the possibility to house three different mobile standards in the same physical infrastructure and the low cost of ownership. Furhtermore, ZTE has advanced LTE dual-mode solutions and quick consignment responses that really meet our requirements," said Peter Ramel, CEO of Hi3G.

Hi3G was a pioneer in 3G, and lagging behind in 4G development was never an option. Fast network deployment and differentiated 4G terminals are key to LTE commercialization. ZTE launched the world’s first data cards based on Qualcomm chipsets that support 3G, TDD LTE and FDD LTE systems. This helps Hi3G rapidly commercialize its LTE network.

For operators, failure to commercialize a network leads to a tremendous loss of revenue and creates the risk of perpetually lagging behind the competition. ZTE set up professional project management teams for site acquisition, civil engineering, equipment installation, and managed services. Hi3G was very satisfied with ZTE’s standardized operation and quality project delivery.