How QCell Reshapes 5G Connectivity in Metro Scenarios—Success in China’s Metros and Beyond

If you have ever taken the metro during morning rush hour, you are familiar with the scene: platforms packed with hundreds of commuters, many using their phones to stream videos, make video calls, or scroll through social media. Then, almost simultaneously, the dreaded buffering spinner appears, rotating endlessly, or the signal bar simply vanishes.

ZTE has helped Chinese operators overcome this challenge with an innovative in-building solution. Today, metro stations, high-speed railway stations, and large shopping malls across China—places beyond the reach of outdoor macro base station signals—enjoy seamless 5G coverage, thanks to a small white “box”: QCell (i.e. pico RRU). Typically mounted on or concealed within the ceiling of station halls, it goes unnoticed by most passengers. Yet it has quietly transformed the daily underground commuting experience for millions.

Beijing Metro Line 12: China’s First 5G-A 4CC-Enabled Metro Line

Shortly after the National Day holiday in 2025, passengers on Beijing Metro Line 12 noticed a subtle change—a “5G-A” indicator appeared on their phones. Video loaded faster; scanning QR codes for entry and exit became smoother; high-definition streams played almost as smoothly as if connected to home Wi-Fi.

Behind this improvement, China Mobile and ZTE deployed 4-band QCell across all stations on Line 12 and enabled 5G-Advanced 320 MHz four-carrier aggregation (4CC) through software upgrades. Four-carrier aggregation combines spectrum resources across multiple frequency bands into a larger broadband pipe. ZTE’s QCell  aggregates four carriers—2.6 GHz (100 + 60 MHz) and 4.9 GHz (100 + 60 MHz)—and, combined with multi-antenna cooperative enhancement algorithms, significantly improves network throughput.

Field tests delivered remarkable results: average downlink throughput exceeded 4.4 Gbps, with peak rates reaching 4.6 Gbps. Line 12 thus became the country’s first metro line to offer a 4CC ultra-fast experience, and the technology now covers all platform areas along the line. The significance of Beijing Metro Line 12 lies in demonstrating the continuous evolution capabilities of the QCell-based digital indoor distribution solution in the 5G-A era—the same hardware infrastructure, through innovations such as carrier aggregation, can evolve from gigabit-level to multi-gigabit (over 4 Gbps) performance.

Shenzhen Gangxia North Station: The “Eye of Shenzhen” Gigabit Experience

Gangxia North Station, an interchange for Shenzhen Metro Lines 2, 10, 11, and 14, is currently the largest metro station in China, with an average daily passenger flow of nearly 300,000. Its main hall ceiling, resembling a giant eye, has earned it the nickname “Eye of Shenzhen.” This landmark station also presents a typical high-capacity, ultra-dense networking scenario—vast open space, extremely high pedestrian density, and complex network topology.

In 2024, Guangdong Telecom and ZTE completed the first commercial deployment of a QCell-based 5G-A SuperMIMO + CA (3CC aggregation) solution operating across the 3.3–3.6 GHz band with 300 MHz of bandwidth. It achieved a new peak downlink throughput of nearly 5 Gbps, demonstrating that 5G-A technology in transport hubs has reached commercial viability.

The elegance of the SuperMIMO scheme lies in its software-based approach: leveraging the existing QCell active digital indoor distribution system, it coordinates spatially distributed pRRUs to form a virtual large-scale antenna array akin to outdoor macro-cell systems. On the one hand, joint beamforming converts interfering signals into useful ones, enhancing the single-user experience; on the other hand, MU-MIMO efficiently enables spatial multiplexing among multiple users, significantly boosting cell capacity.

“Given how enormous Gangxia North Station is, I didn’t expect China Unicom’s network to be this fast—even when the train carriages are crowded, the connection remains smooth,” remarked a daily commuter on Line 11.

The experience at Gangxia North Station confirms a key insight: in high-density, high-value indoor scenarios such as transport hubs, the QCell digital indoor solution, coupled with software innovations like SuperMIMO, can deliver a quantum leap in performance without hardware replacement.

From Metro to Broader Scenarios

The deployment expertise accumulated in metro environments is equally transferable to other high-density indoor settings.

Large Sports Venues

In 2021, the “Big Lotus” main stadium of the Hangzhou Olympic Sports Expo Center—the venue for the opening and closing ceremonies and track-and-field events of the 2022 Asian Games—required reliable wireless connectivity for up to 80,000 spectators. Hangzhou Telecom and ZTE completed the world’s first test and verification of a 300 MHz 5G QCell at this site. In a live test, FTP downlink throughput reached 1.2 Gbps, with uplink rate sustained at 331 Mbps. With the 1D3U (DSUUU) large-uplink frame structure, peak uplink rates exceeded 730 Mbps. Key areas—including spectator stands, the field, and VIP lounges—were fully covered by 4G/5G signals using ZTE’s QCell equipment. At the Chengdu Phoenix Mountain Ice Basketball Arena, Sichuan Telecom and ZTE commercially deployed a QCell system with the 1D3U large-uplink feature enabled, effectively ensuring a reliable user experience during events.

Large Shopping Malls and Commercial Centers

In a major shopping mall in Chengdu, Sichuan Telecom and ZTE deployed QCell products featuring SuperMIMO in the 3.5 GHz band. Live test results showed 5G user rates of around 1.2 Gbps, with peak single-user rates reaching 1.5 Gbps—approaching the theoretical limit for a single user.

Airports and Other High-Density Indoor Scenarios

QCell series products have been extensively deployed in airports, large hotels, commercial shopping centers, and high-traffic office buildings. The QCell supports NR OBW meeting the full bandwidth requirements of major operators in China. It can  also connect to power dividers and ceiling-mounted antennas for flexible multi-point deployment—particularly suitable for underground parking garages with numerous obstructions and irregular layouts.

Concluding Remarks

While these deployments originate from China, the challenge of delivering stable, reliable 5G experiences in high-density scenarios is a common concern for operators worldwide. ZTE is committed to sharing the deployment insights it has gained from complex scenarios—including metros, high-speed railways, sports stadiums, and more—with global operators, offering customized solutions tailored to diverse needs.