Duplex evolution: subband full duplex (SBFD), cross-link interference

From Half-Duplex TDD to Subband Full Duplex

Traditional TDD alternates the entire carrier bandwidth between downlink and uplink in time, creating inherent latency as UL transmissions must wait for scheduled UL slots. Subband Full Duplex (SBFD), introduced in Rel-18, divides the carrier bandwidth into simultaneous DL and UL subbands within the same time slot. A typical SBFD configuration might allocate the upper portion of a 100 MHz TDD carrier to DL, a guard subband in the middle, and the lower portion to UL — all active simultaneously. This dramatically reduces UL latency since devices no longer wait for TDD UL slots, and improves UL…