On August 25th, the Huanggang Road Yellow River Tunnel in Jinan officially opened to traffic, marking a major milestone for the city’s infrastructure. As the world’s largest underwater shield tunnel by diameter, it has dramatically cut travel time between Jinan’s main urban area and the new development zone to just five minutes, creating a vital new artery that connects the north and south banks of the river. Deep within this underground corridor, China United Network Communications Limited has simultaneously deployed a wireless network to ensure continuous and stable mobile signal coverage throughout the entire tunnel journey.

The tunnel’s enclosed, narrow structure creates a complex propagation environment for wireless signals, and the high speed of vehicles places extreme demands on network continuity and seamless handovers. Achieving clear calls, uninterrupted navigation, and a stable connection inside the tunnel became a key challenge for the network optimization team. To address this, engineers from the Jinan branch of CHINA UNICOM conducted repeated on-site surveys before the tunnel opened, meticulously mapping the tunnel’s structure and traffic flow, while identifying potential signal dead zones to precisely determine equipment placement for a customized coverage plan.

Moving away from generic solutions, the project team adopted a macro-cell coverage approach tailored to the tunnel’s conditions. By using high-power remote radio units paired with high-gain panel antennas, the signal is distributed uniformly along the tunnel’s length. This method, compared to traditional setups, greatly reduces the amount of cabling required, achieving efficient coverage while also simplifying construction and ongoing maintenance. After the scheme was implemented, the team carried out multiple rounds of field testing and optimization, focusing on key areas such as the tunnel entrances and exits, upper and lower lanes, curved sections, and connection points.

Engineers worked to fine-tune antenna azimuths, optimize network parameters, and review link budgets to address issues like signal attenuation, handover problems, and weak edge coverage. The few signal bars on a phone’s display are the result of countless trips into the tunnel to collect data and adjust equipment. Now, as drivers travel under the Yellow River, they benefit from both faster commutes and uninterrupted connectivity, with precise navigation, clear voice calls, and reliable support for information queries, video links, and emergency requests all backed by the Unicom network. For passengers, this high-quality network service works quietly in the background, ensuring the signal stays online from entry to exit, without any dropouts.

While the tunnel provides a physical link across the Yellow River, the robust network builds a solid digital foundation for travel. This tunnel’s wireless coverage project had no existing playbook to follow, making it a brand-new challenge. The Jinan branch of CHINA UNICOM tackled it with rigorous professionalism and a pragmatic approach, optimizing each point and overcoming obstacles one by one to complete the communication tasks to a high standard. This effort directly supports a major public works project for the city’s development. Looking ahead, the company will keep pace with urban growth, focusing on transportation network construction and applying the same pursuit of excellence to city expressways, transport hubs, and key commercial areas. By filling coverage gaps and enhancing user experience, CHINA UNICOM aims to empower the city’s high-quality development with superior communication networks.