As applications such as online education, telemedicine, and remote work expand rapidly, 5G indoor scenarios are becoming more common. To address limitations of macro base stations, small base stations that offer small size, low cost, high performance, low power consumption, and easy deployment have emerged. 5G small base stations are now considered a key element of network infrastructure development.
Renewed interest in small base stations
Shortly before the Mobile World Congress 2023, Vodafone released a prototype small base station built on a Raspberry Pi platform and Lime Microsystems software-defined radio (SDR) boards, with a 3D-printed enclosure roughly the size of a consumer router. Vodafone expects that a low-cost prototype based on Open RAN standards can serve as a model for industry innovation and support enterprise demand for private mobile networks, particularly to address the 5G private network market for millions of small and medium-sized enterprises in Europe. The prototype attracted wide attention at MWC2023, indicating strong market interest in low-cost, innovative small base station products.
Similarly, in the weeks before MWC2023, China Telecom Beijing Research Institute announced successful development of a 5G extended small base station pRRU product intended primarily for indoor deployments to address wireless coverage in small enclosed spaces. Notably, the product integrates RF transceivers and digital front-end chips sourced from domestic suppliers, achieving full domestic integration of chips and components. China Mobile Research Institute and its design institutes also completed development of a 5G cloud small cell based on a domestically produced Feiteng CPU in 2022 and won procurement contracts for extended small cells for 2022–2023.
Major operators' investments in small base station R&D have renewed expectations for a "small base station revival". However, reflecting on past development, the industry is cautious. Since the femtocell products of the 3G era, small base stations have periodically become hot topics when macro network coverage matured, offering a lower-cost means to fill coverage gaps. Yet during the 3G and 4G eras, the anticipated widespread adoption of small cells did not materialize. Whether the 5G era will change this remains to be seen.
New demands in the 5G era
Improving indoor network coverage has long been a priority for operators. In the mobile Internet era, approximately 70%–80% of data traffic is generated indoors, and indoor service quality strongly affects user experience. Small base stations are an important tool for operators to improve indoor coverage, but they face competition from other technologies. In some cases, Wi-Fi or long-established distributed antenna systems (DAS) offer lower-cost alternatives while delivering acceptable service. Cost-benefit considerations contributed to the lukewarm commercial success of small cells in the 3G and 4G eras.
In the 5G era, the situation is shifting. 5G systems operate at higher frequencies, where penetration losses are more pronounced. Tests by China Mobile show that in a 2.6 GHz 5G deployment, average indoor downlink rates were only about one-quarter to one-third of outdoor rates, with uplink gaps potentially reaching orders of magnitude. For mainstream 3.5 GHz deployments, the gap can be even larger. Additionally, the 3.5 GHz band often lies outside the operating range of existing DAS systems, preventing operators from reusing existing DAS deployments. These factors increase demand for 5G small base stations.
The development of industry-specific 5G applications also opens new use cases for small base stations. Many verticals, such as manufacturing, healthcare, warehousing, and mining, operate in indoor environments and require higher-quality network services that current Wi-Fi systems cannot fully satisfy. As noted by Li Nan, deputy director at the Wireless and Terminal Technology Research Institute of China Mobile Research Institute, "Small base stations are a key entry point for end-to-end private network solutions. Industry users in factories, mines, and hospitals have strong demand for flexible 5G small cell deployments. The to-B market may reach millions of BBUs and tens of millions of RRUs, and industry network products are expected to yield higher margins than public networks."
For these reasons, small base stations may see renewed growth in the 5G era. Capturing this opportunity will require ongoing industry effort.
Defining "small" in small base stations
Traditionally, the "small" in small base stations referred to lower transmit power and smaller coverage. As market needs evolve, the industry should consider a broader definition.
In many private network deployments, industry users require guaranteed service quality at a contained cost. This explains interest in small base stations built on low-cost commercial general-purpose hardware and Open RAN architectures. Compared with dedicated-hardware small cells, platforms based on commercial off-the-shelf hardware can significantly reduce device cost. More importantly, a decoupled software-hardware architecture and general-purpose hardware lower the development barrier for communications equipment, encouraging more vendors to enter the market and fostering competition and innovation.
Reference designs for 5G cloud small cells and related industrial promotion have demonstrated that open architectures help diversify the ecosystem. In China Mobile's 2022 procurement for extended small cells, both traditional vendors and nontraditional vendors were shortlisted, injecting new vitality into the market. This should improve commercial competition and technical innovation, promoting wider deployment of 5G private networks.
However, small base station specifications require balanced assessment. Although many industry applications are indoor, they can present complex propagation environments, such as heavy obstruction in industrial workshops or underground tunnels. These scenarios often require higher transmit power to ensure coverage but do not demand large system capacity, creating a market niche between traditional small cells and macro cells. Similar cases appear in remote wide-area coverage where higher transmit power is needed but capacity demands are low. In such instances, the "small" aspect refers more to smaller capacity configuration than to lower transmit power. Qualcomm's recently released compact millimeter-wave "macro" base station platform targets the "high power, low capacity" niche, an approach worth industry consideration.
Small base stations as part of computing networks
Deployed close to users in both consumer and enterprise markets, small base stations act as true network edge nodes and can support operators' innovative services. In the context of compute-network convergence, leveraging general-purpose processors in cloudified small cells or adding compute resources to traditional small cells can turn small base stations into edge compute-network platforms that support industry digital transformation.
Because small base stations are deployed near users with shorter inter-site distances than macro cells, they have inherent advantages in user positioning and sensing. Especially indoors, macro cells often cannot obtain navigation satellite signals. If indoor cellular systems can integrate precise sensing and positioning capabilities, they could better serve industry digital applications.
3GPP has defined indoor positioning capabilities for 5G, and discussions on communication-sensing integration are underway, potentially becoming an important part of 5G-Advanced systems. With such sensing and positioning features, small base stations could play an increasingly important role in compute-network convergence architectures.
In summary, market evolution in the 5G era, driven by industry digitalization, gives reason to expect that small base stations will assume a larger role. Achieving this will require collaboration across the industry to build a more open and diverse small base station ecosystem.
