This paper discusses a new 5G-Advanced duplex scheme called sub-band full-duplex (SBFD) and the details of implementing it for 5G TDD spectrum. The SBFD requires an advanced self interference cancellation (SIC) which is designed to handle extremely high level of cross link interference. Novel SIC techniques were designed for base stations (BSs) operating on 3.4 GHz with massive MIMO and on 26 GHz with multi-beam capability. By utilizing electromagnetic walls in conjunction with electromagnetic bandgap, an extremely high level of isolation between transmit and receive antennas is achieved. Residual interference is further removed using fractional nonlinear interference estimation in baseband. Two Proofs-of-Concepts (PoCs) have been implemented for feasibility verification. The first PoC was for a massive MIMO BS operating with 32 cross polarized antenna ports on 3.4 GHz and a bandwidth of 100 MHz. The second PoC was for a multi-beam BS with 256 antenna elements operating on 26 GHz and a bandwidth of 400 MHz. It was observed that the self-interference in SBFD can be suppressed in real time to a level of less than 0.7 dB over the RX noise floor for both 3.4 GHz and 26 GHz in an outdoor environment.