ultra-broadband experience is always the most important pursuit for users. Their demands for wireless network bandwidth have been growing explosively with the rapid development of mobile terminals and related applications. Although current 4G networks can meet most needs for video watching, internet surfing, and social networking services, new technologies such as high definition /ultra high definition (HD/UHD), virtual reality (VR), and augmented reality (AR) have entered people’s daily life, and 4G bandwidth capacity has gradually become a bottleneck to the growth of mobile business. 5G networks are expected to increase the peak data rates to 10 Gbps or above to bring users a completely new broadband service experience. However, it will be several years before 5G will be officially launched in 2020. Expanding the existing 4G network capacity and performance has become a practical concern of operators.
In June 2016, ZTE was the first to put forward its Pre5G concept and solutions to creatively apply 5G technologies to 4G networks. The solutions can improve 4G network performance indicators and capabilities by an order of magnitude while protecting existing investments of operators. Giga+ MBB, one of four key Pre5G solutions, can increase data rates of a mobile network to the Giga+ level and allow users to have ultra-broadband service experience in advance.
Key Giga+ MBB Technologies
ZTE’s Pre5G Giga+ MBB is neither a brand new wireless technology nor a complete transformation of the existing network, but the introduction and convergence of multiple technologies to allow wireless data rates to reach the Giga+ level. It involves using in advance some key commercially available 5G technologies such as Massive MIMO in the 4G network to provide 5G experience based on existing commercial 4G terminals. It also includes LTE-A Pro related technical enhancements defined by 3GPP, scalable 5G technologies such as 4×4 MIMO, Massive CA, license assisted access (LAA), LTE WiFi aggregation (LWA) and 256QAM, ZTE’s innovative neat cell solution for improving higher-order modulation enabler ratio, and ZTE’s unique X-Site solution for smooth evolution to multiple sectors and higher-order MIMO. The key Giga+ MBB technologies are listed below:
Through the introduction of 256QAM—a higher-order modulation scheme, the peak rate can be increased by 33% compared to 64QAM. Due to the strict requirements for wireless environments, 256QAM is mainly used in indoor coverage and hotspot scenarios. Moreover, ZTE has also launched its innovative neat cell solution to reduce pilot interference and inter-cell interference. This can improve the signal-to-interference-plus-noise-ratio (SINR) and channel quality, thereby increasing the 256QAM modulation enabler ratio, cell throughput, and spectrum efficiency.
Carrier aggregation (CA) is an important means of expanding network capacity. The CA technology evolves from two-carrier aggregation to cross-carrier aggregation and then to LAA/Massive CA.
● From 2CC to 3CC to 5CC to Massive CA: Five-carrier aggregation (5CC) is a milestone of the CA technology for LTE-A, while Massive CA—a key technology of LTE-A Pro will support the aggregation of 32 carriers at most.
● Cross-carrier aggregation: Pre5G means not only the evolution of a single technology but also the convergence of multiple wireless technologies. With the aggregation of FDD and TDD carriers, network convergence is implemented more easily, and network capacity is therefore expanded.
● Carrier aggregation using unlicensed frequency bands: The licensed spectrum resource is limited and expensive. To meet the needs for ultra bandwidth, unlicensed frequency bands have been gradually used in the telecom industry as a supplementary resource. LAA and LWA can allow the unlicensed spectrum to be used in LTE and Wi-Fi. LAA aggregates LTE carriers in both licensed and unlicensed bands, while LWA aggregates carriers in licensed LTE bands and unlicensed Wi-Fi bands to exponentially expand bandwidth capacity.
● 4×4 MIMO: 4×4 MIMO is a MIMO system with four input antennas and four output antennas. In theory, more antennas indicate higher transmission rates and higher reliability. The simulation results show that the average cell throughput of a 4×4 MIMO cell is increased by over 90% compared with 2×2 MIMO. ZTE’s unique X-Site solution helps operators smoothly evolve to 4×4 MIMO while protecting their investments for maximum benefits. The evolution to 4×4 MIMO can be implemented in three ways: using RRU cascading to save combiners and antennas and implement 4×4 MIMO configurations for multiband sites; splitting vertical cell sectors to prepare for future smooth evolution to 4×4 MIMO; and using ZTE’s patented X-antenna to enable seamless software switching of 6-sector 2×2 MIMO to 3-sector 4×4 MIMO.
● FDD Massive MIMO: Massive MIMO is a key 5G technology that uses large-scale antenna array to support both horizontal and vertical 3D beamforming and provide larger site throughput than that of any existing multi-antenna base station solution. Massive MIMO can greatly improve spectrum efficiency. Pre5G Massive MIMO is the best solution that directly applies key 5G technologies in 4G networks and is compatible with existing 4G terminals. Pre5G FDD Massive MIMO uses the dense 128-antenna array in combination with ZTE’s TDD Massive MIMO application based big data analysis and its unique patented algorithm to address the worldwide problem of uplink and downlink channel reciprocity. When combined with ZTE’s unique vector chips, it can also efficiently analyze and track users in real time and send them accurate narrow beams to deliver ultra-high throughput services and offer a six- to eight-fold increase in spectrum efficiency (Fig. 1).
Recommended Giga+ MBB Deployment
Giga+ MBB provides Giga+ ultra broadband experience. The following two areas are preferred for Giga+ MBB deployment.
● Heavy-traffic hotspot areas: Hotspots are mainly located in central business districts (CBDs), city squares, commercial centers, stations, and gymnasiums in dense urban areas. In these places, the network environment is complicated due to high population density, high data traffic, and numerous tall buildings.
● Areas requiring ultra-high-speed services: Ultra-high-speed services include HD/UHD videos, UHD online games, VR and AR. These services require high bandwidth and low network delay.
In the next few years with the continued growth of network usage and user needs, operators can gradually expand the areas for deploying Giga+ MBB and finally deploy it across the whole network.
Giga+ MBB involves multiple technologies that have different levels of maturity. Operators can introduce different technologies in stages based on their own requirements, technological maturity levels, and terminal commercialization. ZTE has recommended that operators would deploy Giga+ MBB in accordance with the following plan in the next two years.
● In 2017: Upgrade software to support 256QAM and deploy 3CC/4CC, LAA, and 4×4 MIMO on a small scale (Even if 4×4 MIMO is not available currently, it is also recommended that 4T RRUs be selected preferentially in hotspot areas to prepare for future 4×4 MIMO launch).
● In 2018: Deploy 4×4 MIMO and LAA on a large scale, run 5CC trials on a small scale, and launch FDD Massive MIMO selectively for hotspot areas.
Successful Giga+ MBB Applications
Since ZTE officially launched Pre5G in June 2016, the Giga+ MBB solution has received special attention of operators from both home and abroad. The operators have actively worked with ZTE to carry out Giga+ MBB tests, field verification and commercial deployment, and have created industry records one after another.
In November 2016, ZTE successfully demonstrated Pre5G FDD 1.75 Gbps service with a single terminal at the ZTE VOICE Towards 2020 Summit in Kuala Lumpur, Malaysia. The demonstration became the focus of attention in the summit.
In December 2016, in a 4G+ wireless network enhancement technology seminar held by China Unicom, ZTE accomplished 3CC aggregation and 4×4 MIMO based on the existing network devices and spectrum, and demonstrated 1 Gbps rates using 256QAM technologies. ZTE worked with Belgium’s Telenet to complete the Pre5G field test, and Telenet became the first in Europe to offer a rate of 1.3 Gbps in a real environment, which was fourfold the rate of the existing 4G network. ZTE and Indonesia’s largest operator Telkomsel jointly held a press conference to officially announce the rollout of a commercial Pre5G network in two tourist cities: Makassar and Manado. The Pre5G network increased the rate of the existing network by 2.6-fold. In Budapest, ZTE and Hungary’s Telenor announced the successful demonstration of Pre5G Giga+ MBB services with the peak rate close to 1.2 Gbps, which was also the first Pre5G demo in the Telenor Group.
Since 2017, more operators have started to introduce ZTE’s FDD Giga+ MBB solution. So far, this solution has been tested and deployed in more than 20 networks in 15 countries, leading global mobile broadband towards the Gigabit+ level.