Summary:With the development of 5g commercial license in ChinaDistribution, network scale deployment becomes very important. This paper analyzes the combination of 5g scale deployment from multiple anglesTimely opportunity, as well as possible problems and challenges in 6 aspects, and finally for the main challengesGive corresponding measures.

preface

On December 6, 2018, the Ministry of industry and information technology issued the license for the use of medium and low frequency test frequency of 5g system to the three major telecom operators. Among them, China Telecom and China Unicom obtained the license to use 3500MHz frequency band test frequency, and China Mobile obtained the license to use 2600mhz and 4900mhz frequency band test frequency. Frequency resource is the core strategic resource of mobile communication network. The issuance of 5g system test frequency use license in China effectively ensures that telecom operators carry out the construction of 5g scale test network in an all-round way, and further promotes the maturity and development of 5g industrial chain in China.

The three operators also actively carry out the construction of 5g test network all over the country. In 2018, China Mobile built a scale test network in five cities: Shanghai, Suzhou, Hangzhou, Guangzhou and Wuhan, and expanded to 40 cities in 2019. China Telecom has built a cross provincial and cross regional pilot network dominated by SA and mixed SA / NSA networks, and carried out 5g innovation demonstration pilot projects in 17 cities such as Beijing, Shanghai, Guangzhou and Shenzhen; China Unicom promoted the deployment of "7 33 n" 5g pilot network, contacted and covered the core areas of seven cities such as Beijing, Shanghai, Guangzhou, Shenzhen, Nanjing, Hangzhou and xiong'an, realized the coverage of hot areas in 33 cities, and customized 5g network in n cities.

On June 6, 2019, the Ministry of industry and information technology issued 5g commercial licenses to China Telecom, China Mobile, China Unicom and China Radio and television. China has officially entered the first year of 5g business, and the scale deployment of 5g network construction is the primary task faced by telecom operators. This paper analyzes the possible problems and challenges of 5g scale deployment from the perspectives of standards, equipment, basic resource reserves and vertical industry applications.

Timing of 5g scale deployment

The advance issuance of 5g commercial license in China does not mean that it has the conditions for scale deployment immediately.Compared with the 4G commercial process, the first version of R8 standard was issued in 2009, and foreign operators have been commercial since 2009. After ITU officially approved LTE advanced as the official 4G standard in 2012, China officially issued the 4G license in December 2013. Because there are mature standards, equipment and foreign scale construction experience for reference, domestic operators immediately carried out large-scale network deployment.The 5g complete standard (R16) will not be promulgated until 2020. At present, the standard, chip, equipment and application do not have the conditions for full deployment.The timing of large-scale 5g deployment depends on several important factors.

1.1} standard process

The two versions of R15 standard (OPTION3 and option2) were issued in December 2017 and June 2018 respectively, and the late drop version standard (option4 / 7) was issued in June 2019. The R16 standard that truly realizes all functions of 5g will be frozen in March 2020 and promulgated in June. From the standard process, the current network can only support embB and basic urllc services.

1.2 mature chips and equipment

In January 2019, the imt-2020 (5g) promotion team announced at the summary meeting of phase 3 of 5g technology R & D test held in Beijing that the phase 3 test of 5g was basically completed. 5g base station and core network equipment can support non independent networking and independent networking modes, and the main functions meet the expectations and reach the pre commercial level.

On May 21, 2019, the Ministry of industry and information technology said at the regular policy briefing of the State Council held by the State Council Information Office that China's 5g products are becoming more and more mature, and the links such as systems, chips and terminals have basically reached the commercial level and have the conditions for commercial deployment.

The supply process of main 5g network side and terminal side products is shown in Table 1 and table 2.

 

 

Table 1 network side industrial chain

1.3 basic resource reserve

Compared with 4G network, 5g has undergone revolutionary changes from networking structure to equipment form, and has higher and stricter requirements for various basic resources. The reconfiguration of Cu / Du / AAU and the new service requirements have triggered the adjustment of the network structure of 5g access network. Major changes such as the increase of front-end bearer, Cu / Du convergence (c-ran Networking), UPF / MEC sinking and so on. For the demand for access side transmission resources (optical communication, pipeline, optical cable) and convergence room, the adjustment, optimization and addition shall be completed as far as possible before the deployment of large-scale base stations.

The existing tower mast and floor resources have carried 2 / 3 / 4G network equipment of various systems and frequency bands of the three major telecom operators, and the degree of co construction and sharing is very high. It is very difficult to add 5g AAU, especially to meet the simultaneous deployment of multiple operators. Before large-scale deployment, it is necessary to model, integrate and optimize the existing tower mast and system in detail, Improve the availability and value of stock station sites.

1.4 application maturity

5g's design goal is to fully meet the needs of three scenarios (embB / urllc / mmtc), from starring in to C to flying with both wings of to C and to B. in a sense, 5g's mission is to fully enable various vertical industries and drive the informatization and intelligent upgrading of all walks of life in the whole society through integration with vertical industries. At present, the integrated application of 5g and vertical industries is still in the preliminary exploration stage (as shown in Figure 1). Telecom operators show network capabilities and application prospects through various 5g application demonstrations, build platforms, build circles and hold groups, realize mutual penetration and mutual influence, drive the real commercial maturity of 5g applications, and in turn promote more perfect network construction.

Fig. 1 5g application development stage and typical application

1.5 local government support

Based on the maturity of standards and technologies, local governments have issued policies to support the development of 5g related infrastructure and industries, and formulated clear action plans and development goals. Taking the implementation opinions of Zhejiang Provincial People's Government on accelerating the development of 5g industry as an example, The construction tasks and network coverage targets to be completed at two time nodes (2020 and 2022) are planned in detail. Based on 2022, 5g can be widely used and deeply integrated in various economic and social fields, reach the international leading level, build an excellent 5g industrial ecology, and become a national leading area for 5g network construction and a 5g Industrial Development Cluster with international important influence 5g innovative application demonstration area.

1.6 # scale deployment and appropriate timing

Based on the above factors, it is suggested that the pace of domestic 5g network deployment is as follows: in 2019, it will start from the hot areas of key cities and regions with high demand, and then continue to develop and promote; The first large-scale deployment will be carried out after the official launch of R16 standard in 2020, and the network driven business will further mature. From 2012 to 2022, we will continue to expand the breadth and depth of network deployment, refine the network deployment strategy and capability sinking in combination with coverage and business scenarios, and effectively match and support the integrated development of various industries and 5g.

Challenges faced

After the standards and equipment are mature, promoting the scale deployment of 5g network also faces various difficulties and challenges in network planning, basic resources and project implementation. The following points are summarized.

2.1 selection of network NSA / SA deployment

In the initial stage, 5g mainly gives play to the large bandwidth access capability and supports large traffic services, such as VR, AR, 4K / 8K HD live broadcast return, etc. in order to quickly commercial 5g, NSA (OPTION3 scheme) based on 4G core network EPC can be selected for deployment in the initial stage. With the maturity of standards, equipment and industry, and the demand for more low latency and large connection services, it is necessary to build an SA (5gc NR, option2 scheme) network that fully supports 5g new service requirements and related functions.

From the perspective of seizing market opportunities, it is necessary to quickly deploy the 5g network based on NSA, and then transform and upgrade it to sa network. From the analysis of comprehensive construction cost (TCO), the cost of building NSA first is higher than that of directly deploying SA network on demand.

2.2 what are the changes and effects of GNB after Cu / Du reconfiguration

The reconstructed 5g base station GNB of Cu / Du is divided into three logical functions Cu Du AAU, which leads to the following problems: whether the physical entities of Cu / Du are combined or separated, what method is used for the forward bearer between AAU and Du, the influence of AAU shape (volume, weight and power consumption), and whether the wireless access network architecture needs to be adjusted. Among these problems, the form and deployment of Cu and Du are the most critical. At present, the equipment form provided by the industry is Cu / Du combination, which is similar to 4G BBU. It can be deployed in a centralized or decentralized manner. The transmission bearer is divided into forward and back transmission. In the later stage, based on the business requirements, Cu and Du are independent physical entities, forming a three-level architecture (cu-du-aau). The deployment location of Cu can be high or low. Du can be aggregated and dispersed based on the business requirements. The transmission bearer is divided into forward transmission, middle transmission and return transmission.

2.3} whether 5g NR access network architecture has been adjusted

Since the emergence of the distributed base station (BBU RRU), the wireless access network has two construction modes: dran and c-ran. The c-ran mode saves the computer room resources through the BBU, improves the efficiency through the collaboration of baseband resources, and effectively reduces the remote construction cost, but also increases the transmission resources and maintenance pressure. In the 5g era, c-ran has more important value. In the face of diversified and flexible business scenarios, the wireless access network architecture is required to be more flexible and robust, and the network supports on-demand access of services; Cu / Du separation and Du aggregation are conducive to the introduction of SDN / nfv, flexible arrangement / slicing of resources and automatic network maintenance; Vertical industry integration requires the sinking of network functions, the deployment of MEC and the sinking of media. The 5g NR access network based on c-ran can effectively support telecom operators to optimize connection services, strengthen connection applications, and create the ability to compete positively with Internet companies. Of course, it also faces the huge construction and maintenance pressure of basic resources such as computer room, pipeline and optical communication.

2.4 satisfaction of macro / micro station site resources at sub 6GHz

Three domestic telecom operators have obtained 5g frequency band below sub 6GHz. In terms of coverage capacity, China Mobile has the strongest 2.6GHz capacity. In terms of industrial maturity, China Telecom and China Unicom are more advanced in 3.5GHz. At present, the 2 / 3 / 4G network site resources of the three major telecom operators are very rich, but there are many site property attributes, including operator owned, tower company owned, third-party company owned and public attributes (various lamp poles, floor resources, etc.).

The availability of existing sites involves many factors, including the coverage capacity of 5g base stations (2.6 / 3.5GHz), the satisfaction of existing sites, the acquisition of new sites, and the acquisition of rod resources of small and micro base stations; In terms of stock resources transformation, it includes two aspects: machine room supporting and sky tower and mast; From the perspective of network structure, including the basic resource system under c-ran networking and how to anchor 4G base stations; From the perspective of meeting business requirements, it includes different value areas, special business scenarios and different network deployment and site requirements for 2B business.

2.5 requirements for supporting transformation of 5g GNB equipment

The requirements of the new 5g GNB base station for computer room support and sky support are much higher than those of the previous 2 / 3 / 4G base stations, mainly due to the increase in volume, weight and power consumption of the new AAU equipment. Table 3 is the parameter table of the current typical equipment.

Table 3 physical parameters of 5g GNB equipment of main manufacturers

The new AAU product morphology and physical parameters bring four factors.

a) Space is tight. Under the background of co construction and sharing, multi operators and multi systems are deployed in the same tower, resulting in the shortage of sky resources and the difficulty of adding 5g AAU equipment.

b) High load-bearing requirements. 5g # AAU usually has large volume (more than 35L), high weight (more than 40kg) and large windward surface (more than 0.5m2). The process transformation requirements of sky tower and mast are significantly higher than 4G.

c) Beautifying the sky is limited. The internal installation space of the existing beautified ceiling is limited, which can not meet the installation space and equipment heat dissipation requirements of 5g AAU.

d) Transformation of AC / DC power supply system. After the addition of 5g system, it will bring great pressure on the AC and DC power supply system of the existing base station. Especially in the scenario of multiple shared stations, the lack of AC capacity and transformation are the key limiting factors for 5g scale deployment. The power supply system is shown in Figure 2.

Fig. 2 AC / DC power supply system diagram of 5g base station

2.6} discussion on the construction mode of 5g room

The indoor environment is a high incidence area of data services, and many scenarios are also high-value areas of 5g services. However, the construction of 5g rooms needs to face and consider the following problems.

a)Diversity.

(a) The diversity of indoor coverage construction modes of the current network, including DAS, small panel, leaky cable, leather station, etc.

(b) 5g needs to provide diversified business support capabilities.

(c) Facing the problem of how to build diversified coverage scene types.

b) Complexity.

(a) Traditional DAS is a passive room subsystem, which can not be monitored and managed, so it is difficult to repair faults and build new roads.

(b) The proportion of digital office branches is not high, which can not support fine evaluation and network resource prediction.

(c) How to transform and maintain needs to invest huge human and material resources.

c) Value.

(a) 5g typical indoor business scenarios include VR / AR, intelligent manufacturing, smart energy, wireless medical, etc.

(b) Customized indoor coverage system scheme is required for different value scenarios.

d) Economy.

(a) With large demand and many stations, most of the existing rooms need to be upgraded.

(b) In the middle and later stage of 4G network, operators have introduced digital room sub scheme on a large scale. For 5g, the usage of digital room sub will be greatly increased, and whether the cost will be effectively reduced.

(c) Different scenarios need to be constructed to achieve the best cost performance.

a) Starting from the end, the capacity is embedded. Deeply excavate the existing station site, machine room, transmission and other resources, take the full coverage of 5g SA network as the goal, combined with the network structure adjustment of 5g NR wireless access network, and carry out resource planning and capacity embedding in advance according to the overall c-ran planning, so as to form perfect basic resources (station site, machine room, pipeline and optical cable) for large-scale commercial use.

b) Equipment standby, supporting first. Considering the upgrading and supply capacity of 5g main equipment in the initial stage, there is no hurry to fully deploy. Based on the station site part of 5g comprehensive deployment plan, the station site, sky surface, machine room supporting facilities to be reconstructed and newly built shall be reconstructed as needed in advance to meet the needs of 5g rapid scale deployment.

c) Set up special projects and go hand in hand. According to the scale deployment of 5g network, 5g special project implementation center and multi professional promotion modes including wireless, transmission, computer room and full service are established to reduce the loss of professional communication and coordination and improve the progress and quality of project construction.

d) First mover advantage, lock resources. Give play to the advantages of China Mobile 5g first mover scale deployment, and combine the station location attributes to lock high-quality station location, sky and computer room resources with the tower company in advance.

3.2 taking c-ran as the infrastructure to form basic resource capacity reserve

Before 5g scale deployment, it is necessary to reserve the capacity of basic resources. Considering reducing investment and operation and maintenance costs and facing future technology development and business deployment, c-ran is adopted as the infrastructure of 5g NR wireless access network, and the planning and construction of c-ran relies on the construction of comprehensive business area, The overall network planning and capacity reserve of corresponding basic resources can be completed in the order of plane (comprehensive service area) to point (c-ran convergence room) and then to line (forward / return bearer network). In order to better realize the rapid deployment of 5g wireless network in the future, it is recommended to comprehensively carry out the evolution planning of c-ran architecture for 5g evolution as soon as possible in the existing 4G network planning. The specific suggestions are as follows.

a) Take the forward transmission access of the remote RRU site as the transmission service access demand, carry out the transmission planning, take an optical cable network as the target guidance, and carry out the c-ran area subdivision planning within the scope of the comprehensive service area. It is recommended that a single c-ran area includes about 8 ~ 10 macro station physical points, with an area of 0.5 ~ 5km2, and a single comprehensive service area is subdivided into 3 ~ 4 c-ran areas.

b) Carry out the access computer room planning for the evolution needs of c-ran architecture, and select the computer room with good conditions as the centralized setting point of BBU. The location of the machine room is recommended to be around the primary fiber distribution point, which is conducive to the upward double hanging of two converging machine rooms into a ring. For the area of the machine room, it is recommended to configure at least 20 m2.

c) Carry out forward transmission access planning for c-ran evolution: at this stage, color light can be considered to realize forward transmission, and a single physical point can carry out reasonable wave combining and splitting design and transmission core configuration according to the current frequency points and subsequent frequency expansion requirements. In terms of the selection of remote station access points, the co location station can give priority to the old existing optical cable routes, such as the macro station to the old convergence access ring, and the micro station to the old uplink optical cable; For stations across the comprehensive business area, the hooking needs to be adjusted. According to the new site scheme, it is recommended to connect to level 2 and below optical communication nearby, and it is not recommended to connect directly through level 1 optical communication, which is conducive to saving backbone fiber core resources.

3.3 complete the optimization and integration of sky and surface in advance to ensure the availability of towers and masts at the stock station site

In order to solve the shortage of space resources for 5g construction, on the premise of making use of the old station site as much as possible, combined with the current situation of space resources, prepare high-quality space for 5g AAU according to the following priorities: making use of the old holding pole - New holding pole - replacement holding pole - Space Integration (multi port antenna).

The sky surface integration can be carried out before 5g scale deployment through single project in advance. It is recommended to follow the following rectification principles.

a) Tianmian integration and reconstruction covers urban areas, counties and hot area stations, while tianmian integration will not be carried out for rural and trunk road stations for the time being.

b) Keep the total number of existing sky systems unchanged. In principle, no new sky systems or reduced sky systems are added (except for single sky site systems).

c) As far as possible, 5g antenna and existing 4G antenna share a set of sky system.

d) During the transformation of the sky surface, the network optimization and adjustment shall be carried out simultaneously to ensure the stability of network coverage. During the transformation and integration of the sky surface, the sky surface of the main 4G coverage layer shall be kept unchanged as far as possible.

3.4 classification transformation of AC / DC power supply system

For the transformation of AC / DC power supply system, on the one hand, the current situation of stock stations shall be considered, on the other hand, 5g equipment and later evolution shall be considered. The requirements of current equipment for AC / DC system are shown in Table 4.

 

 

Table 4 requirements for AC / DC system of 5g GNB equipment

Transformation principles and steps:

a) Power matching: give priority to the old machine room, switching power supply and battery, and add new power matching according to the site conditions to meet the construction needs of 5g construction power supply.

b) External power: give priority to the old external power. In case of insufficient external power, the demand for 5g external power can be solved by means of battery peak shaving and capacity expansion to minimize the construction cost. The transformation of external power is a difficulty, and the transformation can be completed according to the steps shown in Figure 3.

Fig. 3 AC system transformation scheme

3.5 build differentiation room subsystem by scene

There are many scenarios for the construction of sub rooms. In combination with 5g business characteristics and requirements, it is suggested to follow the differentiated satisfaction strategy.

a) For high-value areas, it is recommended to use digital rooms.

b) For medium value areas, Picchi station DAS is adopted.

c) For low value areas, outdoor coverage and indoor coverage are adopted.

d) 5g source is used to feed into the existing DAS system for specific scenarios.

Conclusion

buildGood use is not the purpose of 5g. Good use is the real purpose of 5g.5g network coverage will start from hot areas and areas with high demand, and then continue to develop and promote based on the needs of users and services.The main goal of 5g network is to realize the interconnection of all things and Zhilian society. Therefore, the network deployment strategy and mode are different from 4G network. It is more necessary to comprehensively consider all aspects of resources in order to deploy a robust, powerful and flexible 5g network.

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