As mobile communication develops rapidly, the IoT and 5G era is just around the corner. Many countries have put forward their commercial 5G plans to seize first-mover advantages. China has planned to put 5G into commercial operation in 2020. Korea has planned to roll out a pre-commercial 5G network in 2018, expecting to first provide 5G services for the Olympic Winter Games to be held in Pyeongchang. Japan is aiming to launch 5G in 2020 when the Tokyo Olympic Games will be held. The US telecom operator Verizon has proposed taking the lead in commercializing 5G in 2017. In Europe, every country is required to nominate at least one major city to be ‘5G enabled’ by the end of 2020. All leading operators around the globe are striving to pioneer 5G commercialization.
On September 8, 2016, Japan’s SoftBank held a global conference, announcing the official start of their 5G project, which oriented the next-generation high-speed communications standard. SoftBank became the world’s first operator to put Pre5G Massive MIMO into commercial operation. As a strategic 5G partner of SoftBank, ZTE is an important facilitator of this program.
TDD Being the Magic Weapon to Win in the Data Era
SoftBank has both FDD and TDD spectrum resources, so it has used open network architecture to leverage the advantages of both systems. The FDD network that features symmetrical uplink and downlink channel resources and relatively lower frequencies is chiefly used to carry voice and some data services, while the TDD network based on the flexible configuration of uplink and downlink channel resources is chiefly used to carry data services. According to SoftBank, the TD-LTE network, in the fourth quarter of 2016, carried 63% of SoftBank’s entire mobile broadband downlink data traffic, 43% of its uplink data traffic, and 55% of its total 4G users. These data traffic and users were all supported by SoftBank’s 30 MHz TD-LTE spectrum, which accounted for only 20% of SoftBank’s commercial spectrums.
In the next three to five years, SoftBank will use Pre5G Massive MIMO and 8T8R to enhance TDD spectrum efficiency and to gradually move towards 5G. Based on SoftBank’s frequency and technology plans, TDD will handle at least 70% of data traffic in the network by 2020.
Innovative Solutions to Build Highly Competitive Networks
SoftBank selected ZTE’s innovative tailor-made solutions for its existing networks. The solutions include advanced C-RAN architecture, TD-LTE/PHS co-site shared antenna and feeder design, and SuperCell, which can be used to address the interference issue to improve network capacity, and to build quality networks with high performance and high competitiveness.
Advanced C-RAN Architecture
C-RAN, a state-of-the-art architecture solution for radio access network, has four features: centralized, cooperative, cloud, and clean. BBUs are centrally deployed to greatly reduce energy consumption and O&M costs of the radio access network. Baseband resources are shared for intra-site and inter-site synergies. This can significantly improve radio network performance.
TD-LTE/PHS Co-site Shared Antenna and Feeder Design
The costs for new-site construction account for more than half of total network construction costs. After carrying out a number of field surveys and network planning and simulation activities, ZTE came to the conclusion that SoftBank’s existing PHS sites could be reused as new TD-LTE sites. According to the statistics, approximately 80% of SoftBank’s TD-LTE and PHS sites are co-located. Through a series of ZTE’s tailor-made solutions, SoftBank’s TD-LTE and PHS equipment can share antennas and transmission facilities. This co-site shared antenna and feeder design can significantly reduce site rental and auxiliary hardware costs.
Innovative Interference Avoidance
SoftBank’s TD-LTE network uses omni-directional antennas, and the distance between two sites is much smaller than that in an ordinary LTE network. This causes serious co-channel interference. To solve this problem, SoftBank and ZTE jointly launched the SuperCell+SDMA technology that can avoid inter-cell interference by combining adjacent physical cells. The tests performed after the SuperCell+SDMA technology is used in SoftBank’s actual network show that the average network capacity is significantly expanded with the control signal interruption rate being less than 2% and the cell-edge user spectral efficiency going up by 150%.
3.5 GHz 8T8R Solution to Further Improve Network Competitiveness
To meet SoftBank’s requirement for lowering TCO, ZTE has put forward the 3.5 GHz 8T8R solution based on the C-RAN architecture and the existing 2.5 GHz TD-LTE and 1.9 GHz PHS co-site shared antenna and feeder design. The 8T8R solution allows the 3.5 GHz TD-LTE, 2.5 GHz TD-LTE and 1.9 GHz PHS networks to share sites, antennas, and feeders to considerably lower TCO. The C-RAN solution is beneficial to the implementation of subsequent centralized solutions, so that the 8-antenna based 3.5 GHz network solution, including 2CC CA and 256-QAM, can not only achieve the basic 1 Gbps requirement from Japan’s Ministry of Internal Affairs (MIC) but also enable SoftBank’s network to evolve to 5G more easily.
Introducing Latest Technologies to Establish As a Technology Pioneer
In 2015, SoftBank and ZTE signed a Memorandum of Understanding (MOU). Both parties agreed to actively cooperate in Pre5G and 5G research to jointly promote the development and commercialization of new TD-LTE technologies and products. In June 2016, SoftBank, together with ZTE, tested and verified the ultimate performance of Massive MIMO. In a real commercial environment, the peak throughput of a single Massive MIMO cell reached up to 316 Mbps. Massive MIMO also could simultaneously access 200 UEs to smoothly handle various services such as watching videos and browsing web pages, offering users extremely good experience. For cell edges with weak signal strength, compared with traditional macro base stations, Massive MIMO brought 8 to 10 times better internet access experience, greatly reducing the proportion of low-rate users in the network and dramatically improving overall cell performance and user experience.
After five years of rapid development, SoftBank has deployed over 66,000 commercial TD-LTE sites across Japan. From the previous sparse network covering only the first few major cities to the current nation-wide seamless network, the number of TD-LTE users has reached 22 million. Now SoftBank and ZTE are jointly carrying out more extensive research and cooperation in terms of innovative 5G technologies. Committed to becoming the world’s No.1 mobile internet company, SoftBank will surely seize the next-generation network deployment opportunity to lead Japan or even the world in the telecom market.