Considerations for 5G Network Deployments

5G will not only bring much faster access rates, but also penetrate into every corner of the world through flexible network slicing. It will drive the digital transformation of vertical industries and become the cornerstone of digital society.

With the freeze of R15 standard, the release of 5G spectrum, the maturity of 5G equipment and the accelerated development of 5G terminal chip, 2019 will be the first year for 5G commercialization. At this stage, the focus of mobile operators is gradually shifting from 5G equipment testing and verification to more practical network deployment. This article will discuss the key challenges in 5G network deployment, and give some suggestions to operators who are preparing for 5G deployment.

Choosing the Most Suitable Network Architecture

5G deployment has two architecture options: standalone (SA) and non-standalone (NSA). With NSA, a first-mover advantage can be derived from architecture maturity, but it is only applicable to eMBB services and involves complex coupling with 4G network. SA, as the ultimate target network of 5G, has obvious advantages in new service support, coverage, performance, network flexibility and terminal energy efficiency. At present, the major concerns operators have with SA architecture include network coverage, SA terminal and 5GC maturity.

From the 5G R&D roadmaps unfolded by 5G terminal chip vendors like Qualcomm, Intel and MTK, chipsets released from 2019 onwards will support both NSA and SA at the same time; thus for operators starting 5G network construction after 2019, terminal is not a decisive factor in choosing NSA or SA.

Considering the maturity of 5GC, there is no need to have complete features in the initial stage of 5G deployment. Operators can adopt the target architecture in one step, open the interfaces step by step, and introduce the functions in stages, so that the commercial time of 5GC can be advanced to Q1 2019. Therefore, 5GC does not constitute a constraint factor to the commercialization of SA.

Taking the obvious advantages of the SA architecture into account, if operators could achieve continuous 5G coverage with reasonable investment and build an independent 5G network, operators are not very motivated to choose the NSA architecture. Therefore, besides the mandatory requirement of new service, we believe that the coverage capability of 5G base station and the operator's 5G network investment are the key factors for choosing SA or NSA, whether 4G and 5G co-site deployment is feasible highly depends on the cell edge speed requirement of 5G and the density of existing 4G base stations.

Once the quantity of antenna elements, the independent transceiver channels and the transmit power of the 5G AAU are determined, the coverage of the 5G base station mainly depends on the available 5G frequency bands, the complexity of the wireless environments, and the KPI requirements for 5G services, especially the cell-edge access rates. And the planning of cell-edge access rates depends on the minimum network performance requirement of 5G services, whether to support seamless mobility, and the acceptable 5G network construction cost.

Based on the above principles, if an operator only has the millimeter-wave spectrum for 5G construction, it is more appropriate to select the NSA architecture because millimeter-wave has larger propagation loss and poor scattering or diffraction capabilities compared with 1.8 GHz or 2.6 GHz band. When millimeter-wave spectrum is used for mobile access service, it can hardly achieve continuous coverage as 4G network, so it’s better to rely on the 4G network coverage and only use it as a capacity layer to the ultra-high-speed service in hotspot areas.

If an operator can obtain the mainstream 3.5 GHz spectrum, has reasonable cell edge access rate requirement, for example 50 Mbps downlink (supporting 2K/4K HD video and AR applications), 2 Mbps uplink (supporting 720p video upload anytime, anywhere), and also has enough investment to build a 5G continuous coverage network in dense urban areas, we believe that SA is a one-step and more suitable network construction mode. According to ZTE's field test data, in dense urban scenarios where the inter-site distance is less than 400 meters, it is possible to achieve continuous coverage of 5G through 4G/5G co-site deployment; in the area where the site spacing is more than 400 meters, an appropriate number of 5G macro or micro base stations can be added to meet the uplink data rate requirement of 2 Mbps.  

Of course, if an operator has very limited investment at the initial stage of 5G deployment, can only deploy a small number of 5G base stations in 4G network hotspots for marketing purpose, it is more economical and practical to choose the NSA network construction mode.

If the operator has higher requirements for network edge performance, such as increasing the uplink rate to 5 Mbps (supporting 1080p video upload anytime, anywhere), it is recommended to use carrier aggregation of 3.5 GHz spectrum and 1800/900/700 MHz spectrum. Since 1800/900/700 MHz bands have been refarmed for 5G New Radio, the network construction mode is still SA. We think it is very difficult to achieve 5 Mbps uplink data rate in NSA mode with around 400 meters inter-site distance even if the uplink capability of both 4G and 5G is utilized; deploying a large number of new base stations also involves high investment costs, and supplemental uplink solution is too complex.

Maximizing the Value of Existing Site Infrastructure

Besides the network architecture, how to introduce 5G into the existing sites with high-density of RAN equipment is also a major challenge for operators. At present, the majority of operators have multiple bands (such as 900 MHz, 1.8 GHz, 2.1 GHz and 2.6 GHz) and multiple standards (GSM, UMTS, LTE and NB-IoT) in the same site. It is also very common for several operators to share the same site infrastructure such as towers and cabinets. Most of the sites have dense deployments of antennas and RRUs, making it difficult to add 5G AAUs. Building new sites also faces such problems as difficult site acquisition, high investment costs, and long construction periods.

The introduction of multi-band, multi-port passive antennas, active + passive hybrid antennas, and ultra-wideband RRU provides a new way to solve the problem of tight antenna installation space in the macro base station. Operators can consolidate and optimize the multiple antennas of each sector of the existing network before or during 5G construction. Thus, valuable space will be released for installing 5G AAUs, and each sector will only use one or two multi-band antennas to cover all frequency bands and wireless standards for 2G, 3G and 4G, and one active antenna to serve 5G networks. In this way, the 5G network can be deployed without adding new sites, and the multi-network operation and maintenance (O&M) costs can be reduced.

Regarding the 5G AAU equipment, ZTE recommends using 64T64R AAU in dense urban areas to achieve the highest performance, and 16T16R AAU in urban and suburban areas to make a good balance between coverage and network construction costs. The 64T64R AAU consists of a large number of independent transceiver channels, which can support accurate horizontal and vertical beamforming at the same time, thus achieving ideal capacity gains with space division multiplexing in densely populated areas. In addition, 64T64R AAU has strong beam reflection, diffraction, and anti-interference capability. Even in dense urban areas with complex wireless environments, 3.5G NR can achieve the same coverage as existing 1.8 GHz 2T2R LTE with co-site deployment mode, thus reducing the difficulty and cost of 5G network deployment. For the general urban and suburban scenarios with a small number of data users, low traffic density, a very low pairing probability of MU-MIMO, 16T16R AAU is recommended, because it has higher cost-performance ratio, and also enables 3.5G NR to have the same coverage as 1.8G LTE even with co-site deployment mode.

For 5G network blind spots or hotspots, it is recommended to use pad micro station to improve local performance. The pad-sized 5G micro base station can be installed in a concealed location like the exterior wall of the building, the street light pole and the advertising light box, which significantly reduces the difficulty of the site acquisition and can quickly increase the hotspot capacity and eliminate blind spots.

In terms of baseband processing unit, the future-oriented high-capacity baseband processing unit can support all wireless standards from 2G to 5G, and flexible deployments of centralized units (CUs) and distributed units (DUs). Besides converged 4G/5G networking capability, it can support smooth transfer of hardware processing resources from 2G and 3G to 4G and 5G in the future when the existing 2G/3G network reaches the end of its life cycle, thereby maximally protecting the investments of operators.

Introducing AI to Improve Multi-Network O&M Efficiency  

In the 5G era, operators will face the challenges of complex networks, diversified services, and personalized experiences.

The network complexity is mainly reflected in the coexistence of multiple networks; and with the dense networking of large-scale antenna arrays, the complexity of beam control and parameter configuration in 5G is increased by an order of magnitude compared with 4G. The SDN, NFV, and cloud deployments also disrupt the familiar network O&M model of the operator's O&M team. Business diversification is mainly reflected in the fact that 5G exceeds eMBB business and penetrates into vertical industries such as industrial manufacturing, agricultural production, smart home, telemedicine and autopilot. Experience personalization is mainly reflected in the fact that 5G delivers customized and differentiated services for specific industries or users, builds network access, data analysis and application services covering a user's full business processes and full business scenarios, and allows lifecycle management and continuous optimization of customized network slices. The above three challenges urgently need the introduction of AI to improve O&M efficiency.

AI technology represented by machine learning and deep learning can be widely used in network alarm, fault root cause analysis, network coverage, performance optimization, network capacity prediction, accurate network construction, network-level energy management, dynamic scheduling of cloud network resources, and intelligent network slicing, thereby improving network O&M efficiency and reducing network O&M costs. The application of AI can be roughly categorized into intelligent site equipment, intelligent O&M, intelligent edge cloud engine, and intelligent network planning and optimization.

Summary

Although operators will face various during the 5G network deployment period, 5G’s flexible slicing capability and its potential for digitalization and intelligent transformation of vertical industries also give operators confidence about the network profitability in the 5G era. ZTE is willing to closely cooperate with operators to solve the problems in network deployment and O&M, and work together to create a brilliant future!

[Keywords] 5G, 5G network deployments, NSA, SA, Multi-network O&M