Sub-3GHz UBR UniSite for Modernizing 4G RAN in 5G Era

34 countries have recently completed 5G-suitable allocations or licensing procedures in at least one spectrum all over the world. Another 40 countries have announced formal plans for allocating 5G-suitable frequencies between now and end-2021. Over 20 countries have offered commercial 5G services this year. Whether in SA or NSA mode, 5G construction usually starts from hotspots to urban and suburban areas, from macro sites to micro sites. The introduction of 5G network brings great challenges to existing 2G/3G/4G sites.
Overloaded legacy sites: After several 2G/3G/4G deployments, multi-band and multi-standard wireless sites have become normal practice. However, the site infrastructure systems including towers and poles have been increasingly congested and overburdened. The top priority for upgrade is to simplify existing sites and reserve space for 5G NR.
No evolution capability: Based on spectrum analysis, the LTE band in sub-3GHz is an ideal resource for 5G NR in the future. If existing 2G/3G/4G sites cannot be upgraded smoothly, they will become a huge obstacle to 5G evolution.

During the rise of 5G NR, 4G network development has some key features.
Continuous LTE evolution: The development of global LTE has not yet reached its peak. 2G/3G users are being handed over to 4G, and 4G still has expansion expectations and a long-term development window.
Multi-band combination to expand services: With years of development, operators often have multiple bands. More spectrum means more chances. For example, the 700 MHz band is popular in 5G around the world. More countries have added the 700 MHz band to their 5G spectrum. In Europe, 700 MHz is introduced as a new frequency band. Integrating the new spectrum into existing networks without increasing the site load is the concern of operators. 
5G evolution and dynamic spectrum sharing (DSS): The DSS feature in 3GPP R15 allows frequency resources to be shared between LTE and 5G NR. This can balance the residence of existing 4G users and the attraction of new 5G users. 5G evolution and DSS capabilities are powerful tools for operators.

Modernizing 4G networks is therefore the best and necessary choice for operators in the process of 5G deployment. ZTE has developed its ultra-broadband UniSite solution that can help operators continuously optimize 4G network coverage and capacity while enabling the simplest wireless sites to evolve quickly and smoothly to 5G.

As early as 2014, ZTE launched the industry's first innovative ultra-broadband radio (UBR) products. Over the years, ZTE has been innovating its UBR products to fulfill the requirements on frequency bands, power, and performance in various regions. ZTE has rolled out nine UBR device types, covering RRU, AAS, small cell, and micro eNodeB (Fig. 1). More than 150,000 UBR devices have been used in over 20 networks around the world.

ZTE has also released two types of tri-band UBRs with industry leading performance. One is sub-1GHz UBR that works at 700 MHz, 800 MHz and 900 MHz and can be used for large-capacity applications in ultra dense urban or network sharing scenarios, and the other is sub-3GHz UBR that works at 900 MHz, 1800 MHz and 2100 MHz. The tri-band UBRs have the following attractions.
More powerful but smaller RRU: Compared with traditional three equivalent RRUs, a tri-band UBR reduces in size by 20% and in quantity by 66%. It saves footprint, rental, transportation and installation fees, and O&M cost, and reserves space for high-frequency 5G.
Dynamic spectrum sharing: The tri-band UBR supports DSS through software upgrade. The DSS function allows dynamic spectrum sharing between LTE and 5G NR. It attracts new 5G users while ensuring 4G user experience in the existing network.
Large capacity to meet multi-mode configuration: The sub-1GHz tri-band UBR supports large capacity in GSM/UMTS/LTE/NB-IoT/NR multi-mode configuration. 2×140W ToC output power can be dynamically distributed to three frequency bands. The other sub-3GHz tri-band UBR features 6×80W ToC output power, multi-mode configuration, large capacity, and 4T4R in both B1 and B3. The UBR product family can meet the requirements of high-speed data traffic in dense urban scenarios. 
Environment-friendly RRU: To reduce energy consumption, the latest sub-3GHz tri-band UBR adopts the power amplifier with higher efficiency. The system efficiency improves from 26% to over 32%.

In one project in Europe, for example, an operator plans to introduce the 700 MHz band into a 5G network, while its devices that work at 800 MHz, 900 MHz, 1800 MHz, 2100 MHz and 2600 MHz bands in the existing network are restricted by the evolution capability and installation space.

In this scenario, ZTE's UBRs can be used to transform the site to a full capable compact one that supports multi-band operation, smooth 5G evolution, LTE/NR DSS, and carrier aggregation (CA). In this way, spectrum resources can be flexibly allocated to attract new 5G users.

ZTE's sub-3GHz UBR UniSite solution take into full consideration the site deployment requirements during the transformation in early 5G era. The industry-leading UBR series help operators rebuild high-quality 4G networks that provide multi-mode, multi-band and full-scene coverage. The solution aims at the long-term operation of 4G networks and supports DSS as well as 5G smooth upgrade in terms of device capabilities and network architecture, laying a solid foundation for a smooth migration to 5G.