Subband Full Duplex (SBFD) is an innovative duplexing method for advanced 5G/6G cellular communication that enhances uplink coverage and minimizes communication latency compared to TDD. SBFD allows a base station to transmit and receive simultaneously in distinct downlink and uplink sub bands within the channel bandwidth of a TDD carrier. To maximize the advantages of SBFD communications, it's crucial to mitigate self-interference and cross-link interference between nodes. This paper initially discusses the enablers for interference mitigation in SBFD deployment, followed by an evaluation analysis and field measurement results of SBFD duplex technology for a 5G massive-MIMO macro network in the 5G band.

Time-division duplex (TDD) and frequency-division duplex (FDD) are mainly used in commercial new radio (NR) deployments, where the time- or frequency-domain resources are split between downlink (DL) and uplink (UL). Full duplex (FD) will enable 5G-advanced and 6G systems to go beyond TDD and FDD operation into a new duplexing mode that leverages the benefits of both TDD/FDD deployments. It achieves higher throughput and lower latency while enabling flexible UL/DL scheduling. However, there are several challenges that need to be overcome to enable FD operation in large-scale system deployment, including intranode and internode [user equipment (UE) and next-generation node B (5G base station)] interference along with intercarrier interference. In this article, we present solutions to mitigate self-interference (SI) and cross-link interference (CLI) in 5G-advanced/6G systems, provide system-level evaluations, and discuss the outcome of Third Generation Partnership Project (3GPP) study item on duplexing evolution. We introduce the concept of subband FD (SBFD) as an effective solution for a macro network to achieve the key features of FD, such as latency reduction and UL link budget improvement. Finally, we present the field test results for the performance of world-first SBFD prototype of high transmit power massive-multi-input-multioutput (MIMO) macro network.