China’s Ministry of Industry and Information Technology (MIIT) has set a significant precedent by licensing operators to refarm sub-3GHz spectrum bands—traditionally used for 2G, 3G, and 4G services—into 5G bands.
This decision was widely received as a critical step in addressing the growing need for enhanced 5G coverage and communications capacity.
By reallocating existing spectrum, regulators are enabling operators to maximise their spectrum assets, reducing operational expenditure (OPEX) while improving service delivery.
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The strategic role of sub-3GHz
Sub-3GHz bands are uniquely positioned in the 5G ecosystem due to their low propagation loss, long transmission distance, and robust industry ecosystem.
These characteristics make them important for providing foundational 5G coverage, particularly in rural and suburban areas where terrain challenges traditional infrastructure.
For instance, China Mobile’s utilisation of 700MHz spectrum for its ‘5G Smart Ocean’ initiative has achieved full-scenario network coverage for coastal and oceanic regions, underlining the transformative potential of sub-3GHz bands.
For high-speed railway lines, where high mobility and penetration loss are major obstacles, operators like China Unicom are leveraging a combination of TDD (Time Division Duplex) and FDD (Frequency Division Duplex) networks on sub-3GHz bands to maintain consistent and stable connectivity.
For sea areas, where long-distance coverage is critical, FDD Massive MIMO has been deployed to extend coverage to over 100 kilometres.
Mobile AI’s network demands
The need for uplink bandwidth and low-latency connections is growing at an increased rate due to the proliferation of AI-powered mobile applications.
Because sub-3GHz bandwidth is specifically designed to satisfy these needs, services like Internet of Things (IoT) applications and RedCap (Reduced Capability) devices can operate without a hitch.
High spectral efficiency and reliable network performance are ensured by these low-frequency bands' ability to provide wide-area coverage and support cutting-edge features like beamforming technology and multi-antenna systems.
Furthermore, sub-3GHz networks' scalable architecture facilitates easy updates to support emerging technologies.
For instance, operators will be able to combine several sub-3GHz bands into a single carrier using Multi-Band Serving Cell (MBSC) technology, as outlined in 3GPP Release 18, which specifies further improvements of the 5.5G system.
By generating a 100 MHz FDD bandwidth, this invention might greatly improve spectrum efficiency and increase network capacity.
Advancing 5G with ultra-wideband solutions
As operators continue to refarm and optimise the sub-3GHz spectrum, ultra-wideband solutions are emerging as a critical tool. These solutions combine fragmented sub-3GHz bands, allowing operators to use spectrum resources without incurring excessive costs.
Advanced FDD beamforming technology further enhances the potential of these bands, allowing for narrower, more focused beams that deliver higher capacity and improved spectral efficiency.
Operators are also adopting energy-saving technologies to reduce the environmental footprint of 5G networks.
By integrating intelligent energy management into their sub-3GHz infrastructure, they are striking a balance between performance and sustainability—an increasingly vital consideration in modern telecommunications.
The broader impact of sub-3GHz 5G
Beyond individual users, sub-3GHz spectrum benefits communities and industry by promoting innovation and economic growth.
Opportunities in industries like tourism, healthcare, and education can be unlocked by improved 5G connectivity in rural and isolated locations.
Uninterrupted access to online learning platforms and real-time information, for example, is empowering people and companies and closing the digital gap that has traditionally divided urban and rural populations.
Sub-3GHz 5G networks facilitate information sharing, job creation, and infrastructural developments, they have stimulated local economic growth in China.
These networks are also essential for improving public services, such as smart agriculture and telemedicine, highlighting the socio-economic benefits of dependable and widespread 5G coverage.
A collective vision for 5G expansion
As the telecoms sector transitions to the 5.5G era, the collective focus remains to ensure that all frequency bands change to meet the increasing needs of AI and digital transformation.
With its reach and flexibility, sub-3GHz spectrum is now a fundamental component of contemporary mobile networks rather than only an adjunct to higher-frequency bands.
China's experience serves as a model for operators worldwide, highlighting the importance of refarming and optimising these bands.
The industry is ready to fully utilise sub-3GHz spectrum by adopting ultra-wideband solutions, multi-antenna systems, and cutting-edge technologies such as FDD Massive MIMO.
This evolution represents not only a technological milestone but also a commitment to inclusivity, connecting underserved communities and empowering individuals to thrive in the digital era.
In the race to build smarter, more connected societies, sub-3GHz 5G stands as a testament to the power of spectrum innovation.
