Building a solid network foundation is a strategy for operators' mid- and long-term 5G development and also one of their traditional strategic directions. Most operators have gone through the network planning and construction from 2G to 4G. Given the more complex networks and more stringent service requirements in the 5G era, the mid- and long-term network planning will be more challenging. With its long-term experience and E2E product delivery capability, ZTE provides a top-level network design and E2E network planning to help operators build a highly cost-effective 5G network.
Starting with a Top-Level Design
Before planning a network, operators first need to define their mid- and long-term vision and goals, including market share, user scale, revenue, and cash flow, as well as their key strategies, for instance, being the first to launch commercial 5G services to preempt high-end users, maximizing the value of the existing networks, and using TCO to increase the operating income. Under the guidance of these strategic goals, operators can make the top-level network design from three aspects: spectrum, architecture, and deployment pace.
—Spectrum strategy: Spectrum is the primary consideration in a top-level design. In 5G spectrum planning, industry maturity, spectrum fees, and network performance need to be considered. 3.5 GHz is the mainstream 5G spectrum as it provides a larger capacity with wider bandwidth in most countries. Despite its high licensing fees, it is still the first choice for most operators. Compared with 3.5 GHz, 2.6 GHz is more advantageous in coverage and would be a good choice if sufficient bandwidth can be obtained. In the mid- and long-term, operators need to use a mix of low-band, mid-band, and high-band spectrum to achieve low-cost coverage of the 5G network.
—Network architecture strategy: NSA is the initial 5G deployment choice while SA is the ultimate goal. Operators need to make a reasonable choice based on their mid- and long-term development goals. Those with enough investments can select SA at the beginning of 5G deployment since SA reduces the TCO over the mid- and long-term and supports the fast integration of 5G into the vertical industry market. Those who start from the NSA and transition to the SA in the future can consider smooth evolution solutions, such as a converged core network and NSA/SA dual-mode BTS, to avoid or reduce repeated investments and lower the engineering difficulties.
—Deployment pace: A demand-driven approach is critical in network deployment. The initial stage of 5G deployment focuses on eMBB services dominated by big video. During this period, a large number of users still stick to 4G with the average traffic per user increased continuously, thus making 4G enhancement still a priority. 5G can be started out in dense urban areas of select cities. In the 5G growth phase, the sub-6 GHz 5G service is gradually extended to most of the cities, towns and suburbs around the country, and a large number of users migrate to the 5G network. Meanwhile, portions of the 4G FDD spectrum can be refarmed to 5G, making up the 5G coverage layer. In the 5G maturity phase, the sub-6 GHz network covers all towns with the use of small cells and mmWave for in-depth coverage in urban areas.
Wireless Access Network Planning
In wireless access network planning, a deep analysis of the existing network is important in that operators can identify high-value areas, which helps them plan and deploy an enhanced 4G network and precisely address hotspot areas in the early 5G stage, and a reuse of the existing site resources is crucial for accelerating 5G deployment and reducing 5G deployment costs. Based on the analysis of the existing network, the mid- and long-term wireless network planning focuses on full-scenario equipment selection, KPI planning, and key technology applications.
—Full-scene wireless network planning and model selection: First, match different coverage scenarios with the most suitable products to improve the cost-performance ratio and then deploy them in phases. For example, in the early stage, 3.5G@64TR AAU is used for general urban coverage and the 32TR solution for expanding coverage into the suburban areas. In the middle and later stages, small cells are used to secure coverage for indoor hotspots and low-cost differentiated equipment for special scenarios such as local hotspots, blind spots, high-speed railway and tunnels.
—Service KPI planning: 5G coverage is limited in the uplink, and thus defining the cell-edge uplink rate is key to determining the site density. Setting a reasonable cell-edge uplink rate meets user experience expectations and also controls the network construction scale. Based on an analysis of the resolutions for smartphone front cameras, the cell-edge uplink rate can be set at 1 Mbps to 2 Mbps for 5G in its initial phase. With the increasingly high service requirements, terminal capabilities, and deepening 5G coverage, the cell-edge uplink rate can be increased to about 10 Mbps in urban areas.
—Planning and application of key technologies: Some key technologies are needed in wireless network planning to improve network performance, for example, FDD assisted super TDD (FAST) for enhanced uplink capability, the dynamic spectrum sharing solution SuperDSS, AI-based automatic antenna pattern control (AAPC) and 1+X SSB.
Core Network Planning
The core network needs to be planned from a long-term perspective by taking into account both the current service requirements and the future capability evolution. Therefore, the converged architecture Common Core is deployed at the very beginning, and functions as vEPC in the NSA phase, EPC + 5GC in the NSA+SA hybrid networking phase, enabling smooth evolution. Both software and hardware can be reused to help reduce costs and the impact on user experience. Core network planning and deployment focuses on such aspects as multi-level DCs, 4G and 5G interoperability, voice services, user data platform, policy platform, network orchestration and management platform. The planning for multi-level DCs is discussed here.
Planning and deploying multi-level DCs is to meet the low-latency and large-bandwidth requirements posed by 5G services. Generally, two to three levels of DCs are planned for 5G networks, including central, regional and edge DCs. The private network UPF and MEC for vertical industry applications are deployed in the edge DC, the public network UPF and the control-plane NEs for vertical industries in the regional DC, and other control-plane NEs, user data platforms, and IMS in the central DC. Multi-level DCs are deployed in phases and on demand. The central DCs are deployed first, and then regional DC, with edge DCs deployed on demand.
Transmission Network Planning
Transmission networks are moving towards high bandwidth, low latency, high-precision synchronization, automation and intelligence. Microwave has been the primary backhaul technology for 2G/3G/4G in most countries. At present, 5G microwave can deliver a throughput of over 10 Gbps, meeting the transmission requirements of most 5G sites. Therefore, transmission network planning needs to take into account both the microwave transmission and the optical fiber transmission for the optimal network construction cost. The increasing use of fiber in wireless access networks and OTN downshifting are also general trends. Considering the requirements for 5G transmission bandwidth, it is recommended to build a 50 Gbps or 100 Gbps platform in the access ring, a 200 Gbps/400 Gbps platform in the aggregation ring, and provide Tbps-level capacity for the backbone network. In addition to capacity, new technologies need to be gradually introduced to fully meet 5G service requirements, including FlexE, SRv6, SDN, high-precision synchronization and TSN. Meanwhile, if the existing equipment can be upgraded to meet the 5G requirements, reuse it as much as possible; if not, replace it or build a dual-plane transport network to carry 4G and 5G services respectively.
A Planning Case
ZTE has made a mid- and long-term 5G E2E network planning for an operator in Southeast Asia (Fig. 1). In this plan, 3.5 GHz is used as the primary 5G coverage layer, 700 MHz+2.1 GHz as the bottom layer for extensive coverage, 26 GHz for FWA and high-demand hotspots. The first phase of 5G network is NSA, followed by NSA+SA hybrid networking, and a migration to SA. In the first stage of network deployment, to realize a low-cost, fast 5G commercial deployment, 3.5G@64TR AAUs are co-located with 1.8 GHz sites in the proportion of 1:1, and 4G services are deployed on the newly acquired 700 MHz spectrum. In the second stage, the 3.5G@32TR network covers most suburban areas and towns, and new 5G sites are built to ensure a cell-edge uplink rate of 2-5 Mbps. Also at this stage, 26 GHz is used for FWA, and additional 700 MHz sites are deployed for capacity expansion with some sites re-farmed to 5G. In the third stage, the 3.5 GHz network is further expanded with the use of small cells for deep 5G coverage, and 2.1 GHz is used to provide 3G voice, 4G data and 5G URLLC services through dynamic spectrum sharing.
To plan an end-to-end 5G network over the mid- and long-term, operators can adopt a top-down approach, with a focus on a top-level design and coordinated planning between RAN, core network and transmission network, building a solid foundation for 5G development.