Base Station Antenna Array Size Impact on Interference Between TDD Cellular Networks

Efficient utilization and sharing in the mid-band spectrum, where time-division duplex (TDD) is widely assumed, is becoming more critical in current and next-generation (e.g., 6G) mobile networks. With technology advancements and diverging applications, interference handling in TDD via tight coordination among operators becomes more challenging. This paper analyzes the potential benefits of spectrum sharing by employing beam-forming with an increased base station (BS) antenna array size, which offers significant interference reduction and an increase in desired signal levels. A coexistence simulation framework recently developed by the 3GPP RAN4 Working Group in Release 18 was utilized to analyze the impact of BS array size on coexistence between TDD networks. Three BS array sizes, 2×2, 4×4, and 8×8, are compared. The simulation framework modeled intra-network co-channel interference and inter-network adjacent-channel interference using an aggregate of dozens of neighbor cells to a single target cell. This study addresses various practical deployment scenarios including urban-macro and urban-micro. This paper examines the impacts of unsynchronized TDD among operators, evaluates the consequential coexistence risks, and analyzes the performance benefits of interference mitigation using large BS arrays.