Enabling Advanced Duplex in 6G

In this paper, an advanced duplex (AD) scheme is proposed to use flexible downlink (DL) and uplink (UL) allocation in time division duplex (TDD) carrier in 6G. By utilizing self-interference cancellation (SIC) capability at a base station to handle the interference from DL signal to UL signal, the proposed duplex scheme enables to simultaneously operate UL and DL on the same carrier but on different frequency resources. To do so, both TDD's ability to efficiently handle asymmetric UL and DL traffic and frequency division duplexing's coverage advantage can be achieved together in the AD scheme. To verify the feasibility, a Proof-of-Concept is developed where it is observed that the benefits of AD scheme can indeed be realized using the proposed SIC techniques. In a system having a 100 MHz bandwidth in the 2.4 GHz band, a multi-level SIC is applied to suppress the self-interference to less than 1 dB without a guard band between DL and UL signals. Based on this technology, in 6G, various duplex techniques can be applied in a time-varying manner, so that a significantly higher resource utilization than the existing 5G will be possible.