In December 2013, China's fourth-generation mobile communication (4G) license was issued, and 4G technology was officially commercialized. At the same time, the research and development of the fifth generation of mobile communication (5G) for the next generation of mobile communication demand has already been carried out in full swing in the world.
At the initial stage of 5G research and development, how to establish a comprehensive set of key technology evaluation index system and evaluation methods for 5G, achieve objective and effective third-party evaluation, and meet the development needs of service technology and resource management are also important issues facing the current 5G technology development. As the national radio management technology institution, the National Radio Monitoring Center (NRMC) is actively participating in the organization and research projects related to 5G. At present, the monitoring center spectrum engineering lab is strongly based on service-oriented architecture (SOA) open electromagnetic compatibility analysis test platform, to achieve large-scale software, hardware, and the integration and application of high performance testing instruments and meters, for radio management institutions, research institutes and industry related units to provide good radio systems research, development and validation of experimental environment. For the evaluation of 5G key technologies, the monitoring center plans to use the platform to build a testing and validation environment for 5G systems, so as to achieve objective and efficient evaluation of various key technologies of 5G.
In order to fully grasp the lifeblood of 5G technology and ensure that it keeps pace with The Times, the monitoring center actively engages in the tracking, sorting and research of 5G key technologies, and carries out technical reserves in advance for 5G frequency planning, monitoring, and key technology evaluation, test and verification. Some of these key technologies are briefly analyzed and interpreted below.
Key 1: High frequency transmission
Mobile communication under the traditional operating mainly in 3 GHZ frequency band, which makes the spectrum resource is very crowded, but at high frequencies (e.g., millimeter wave, centimeter wave band) available spectrum resource is rich, can effectively relieve the strain on spectrum resources present situation, can achieve very high short distance communication, support 5 g capacity and the demand of transmission rate, etc.
The application of high frequency band in mobile communication is the development trend in the future, which is highly concerned by the industry. Adequate available bandwidth, miniaturized antenna and equipment, and high antenna gain are the main advantages of high frequency millimeter-wave mobile communication, but there are also disadvantages such as short transmission distance, poor penetration and diffraction ability, and easy to be affected by climate and environment. The problems of RF devices and system design also need to be further studied and solved.
The monitoring center is currently actively carrying out research on high-frequency demand and the selection of potential frequency candidates. Although high frequency resources are abundant at present, scientific planning and overall consideration are still needed to optimize the allocation of precious spectrum resources.
Key 2: New multi-antenna transmission
Multiple antenna technology has experienced the development from passive to active, from 2D (2D) to 3D (3D), and from high-order MIMO to large-scale array. It is expected to achieve a ten-times or higher improvement in spectral efficiency, which is one of the important research directions of 5G technology.
Due to the introduction of the active antenna array, the number of cooperative antennas that can be supported by the base station side will reach 128.In addition, the original 2D antenna array is expanded to 3D antenna array, forming a novel 3D-MIMO technology, which supports multi-user beam intelligent modeling and reduces inter-user interference. Combined with high-frequency millimeter-wave technology, the wireless signal coverage performance will be further improved. At present, researchers are working on large-scale antenna channel measurement and modeling, array design and calibration, pilot channel, codebook, feedback mechanism and other issues. In the future, it will support more user air separation multiple access (SDMA), significantly reduce the transmission power, achieve green energy saving, and improve the coverage capability.
Key 3: Simultaneously same frequency full duplex
In recent years, the simultaneous, co-frequency, full-duplex technology has captured the industry's attention. Compared with the traditional TDD and FDD duplex, this technology can theoretically increase the spectral efficiency of the port by one time. Full-duplex technology can break through the limitations of FDD and TDD in the use of spectrum resources, making the use of spectrum resources more flexible. However, full duplex technology requires high interference cancellation ability, which poses a great challenge to the interference cancellation technology. At the same time, there is also the problem of the same frequency interference in adjacent cells. In the case of multi-antenna and networking, the application of full duplex technology is more difficult.
Key 4: D2D
In traditional cellular communication system, the base station is the center to realize cell coverage, but the base station and the relay station cannot be moved, so the flexibility of the network structure is limited. With the continuous increase of wireless multimedia services, the traditional service providing mode based on base station can no longer meet the business needs of a large number of users in different environments.
D2D technology can realize the direct communication between communication terminals without the help of base station, and expand the network connection and access mode. Due to short distance direct communication and high channel quality, D2D can achieve higher data rate, lower delay and lower power consumption. Through widely distributed terminals, coverage can be improved to achieve efficient utilization of spectrum resources; Support more flexible network architecture and connection methods to improve link flexibility and network reliability. At present, D2D uses broadcast, multicast and unicast technology. In the future, D2D enhancement technology will be developed, including D2D-based relay technology, multi-antenna technology and joint coding technology.
Key 5: Dense network
In the future 5G communication, the wireless communication network is evolving towards the direction of network diversification, broadband, integration and intelligence. With the popularity of all kinds of intelligent terminals, data traffic will appear blowout growth. In the future, data operations will be mainly distributed indoors and in hot spots, making ultra-dense networks one of the main means to achieve the 1,000-fold traffic demand of 5G in the future.
Ultra-dense networks can improve network coverage, greatly increase system capacity, and distribute traffic, with more flexible network deployment and more efficient frequency reuse. In the future, for high frequency band and large bandwidth, a more intensive network scheme will be adopted, with the deployment of more than 100 small cells/sectors.
At the same time, the increasingly intensive network deployment also makes the network topology more complex. Inter-cell interference has become the main factor restricting the growth of system capacity, which greatly reduces the network energy efficiency. Interference elimination, rapid cell discovery, collaboration between dense cells, and mobility enhancement schemes based on terminal capability enhancement are all the research hotspots in dense networks.
Key 6: New network architecture
At present, the LTE access network adopts the network flat architecture, which reduces the system delay and the cost of network construction and maintenance. Future 5G May adopt C-RAN access network architecture. C-RAN is a green wireless access network architecture based on centralized processing, collaborative radio, and real-time cloud computing architectures.
The basic idea of C-RAN is to build a wireless access system covering hundreds of base station service areas, or even hundreds of square kilometers, by making full use of low-cost and high-speed optical transmission network to transmit wireless signals directly between remote antennas and centralized central nodes. C-RAN architecture is suitable for the use of collaborative technology, which can reduce interference, reduce power consumption, improve spectral efficiency, and facilitate intelligent networking for dynamic use. Centralized processing helps reduce costs, facilitates maintenance, and reduces operating expenses. Current research topics include the architecture and functionality of C-RAN, such as centralized control, baseband pool RRU interface definition, closer collaboration based on C-RAN, such as base station cluster, virtual cell, etc.
The comprehensive construction of a 5G technology test and evaluation platform can provide an efficient and objective evaluation mechanism for 5G technology, which is conducive to accelerating 5G research and industrialization process.5G test and evaluation platform will smoothly evolve on the basis of the requirements of the existing certification system, thus accelerating the standardization and industrialization of the test platform, which is conducive to China's participation in the future international 5G certification system and building a bridge for the development of 5G technology.
In the future, the main tasks of the intelligent laboratory include: establishing the intelligence assessment system of AI intelligent system, and carrying out the intelligence assessment of artificial intelligence in the world; Carry out Internet (city) cloud brain research plan, build Internet (city) cloud brain technology and enterprise map, and serve to improve the intelligence level of enterprises, industries and cities.