Recently, China Mobile, in collaboration with ZTE Corporation, achieved a significant milestone by completing the world's first Unified Time and Frequency Division Duplex (UDD) technology network verification. This achievement marks a solid step from theoretical research to practical implementation. UDD represents a breakthrough in mobile communication duplex technology, enabling base stations to simultaneously transmit and receive on a single carrier. It significantly enhances spectrum flexibility, boosts uplink throughput by over 70%, and substantially reduces transmission latency (achieving zero-slot waiting delay at the terminal). UDD is a pivotal technology for 5G evolution and a hallmark for future 6G.
Drawing upon extensive technical expertise and commercial network experience, China Mobile and ZTE have led the industry in exploring dual-mode research, theoretical studies, international standard formulation, and prototype testing.
Mobile communication duplex modes define the direction and timing of data transmission on spectrum resources. Currently, there are two main modes: Time Division Duplex (TDD) and Frequency Division Duplex (FDD). If we liken communication spectrum resources to lanes, FDD operates like a dual-carriageway where vehicles can only travel in one direction per lane. In contrast, TDD functions as a single lane where vehicles travel in different directions at different times. FDD achieves higher communication efficiency by utilizing twice the resources. However, under the relentless efforts of China Mobile and ZTE, simultaneous bidirectional transmission within a single lane has become a reality.
Theoretical Guidance Translated into Practical Success: The Industry's First UDD Base Station Equipment
China Mobile pioneered the UDD technology, addressing the industry challenge of effectively suppressing nonlinear interference in high-power multi-antenna systems through an "external reference, internal isolation" technical approach. "External reference" involves AI deep learning methods to analyze and reconstruct interference signals, utilizing neural networks' nonlinear solving capabilities for interference elimination at the receiving end. Additionally, separation-based antenna architecture and sub-band filters are employed to isolate interference signals. "Internal isolation" refers to scheduling uplink and downlink data within the same communication carrier at different frequency domain positions, thereby reducing the base station's interference suppression requirements. In 2022, China Mobile, in collaboration with ZTE, introduced the industry's first UDD base station equipment. By combining spatial, frequency, analog, and digital domains for interference suppression through the "external reference, internal isolation" approach, severe self-interference has been reduced by over 130 dB.
Driving UDD into 5G-A Standards: Contributing to Industry Chain Improvement
In the promotion of 5G-A standards, China Mobile played a pioneering role as the rapporteur in 3GPP, establishing and leading the completion of the NR Duplex Operation Evolution study project. China Mobile and ZTE submitted multiple proposals, including key technology research and prototype test results. This study item concluded in December 2023, with China Mobile as the lead author of Technical Report TR 38.858. The feasibility of UDD technology was preliminarily confirmed, and subsequent efforts will continue to drive the formulation of 3GPP R19 duplex evolution standards (Work Item).
Significant Achievements in Series of Test Results: Network Verification Facilitates Commercial Deployment Expansion
Since 2023, China Mobile and ZTE have continuously promoted critical capability verification for UDD, including validation in industrial field network applications. Recently, China Mobile Research Institute and China Mobile Beijing, in collaboration with ZTE, completed the world's first UDD network verification. Test data revealed that single-terminal uplink throughput increased by over 70% compared to 5G commercial networks, average end-to-end latency decreased by over 50%, and reliability improved by a factor of 9. This verification also provided valuable reference data for cross-slot interference research and commercial deployment.
Excellent Backward Compatibility: Seamless Access for Existing 5G Terminals to UDD Systems
UDD technology boasts remarkable backward compatibility. By upgrading base stations, existing 5G terminals can enjoy enhanced network capabilities and improved user experiences. China Mobile has completed interoperability verification with numerous mainstream commercial terminals both domestically and internationally. Through intelligent resource scheduling at base stations, optimal service experiences can be provided to different users on demand.
Enabling More Application Scenarios: Preparing for Future 6G Evolution
UDD liberates control over transmission and reception, disrupting traditional network spectrum utilization patterns. It represents a significant milestone in dual-mode technology breakthroughs. Looking ahead, China Mobile will continue to collaborate with industry partners to address challenges related to high-power base stations, simultaneous same-frequency self-interference suppression, and full-duplex technology. Ultimately, the dream of full-duplex technology will become a reality.
China Mobile, in partnership with ZTE, will continue to innovate and drive UDD to create new spectrum application models, gradually turning the dream of full-duplex technology into reality.
