NR-U Random Access Latency via RO-SSB Mapping

The patent applies preliminary action by performing LBT operation in advance before the scheduled RO time. The WTRU conducts the listen-before-talk procedure during a determined time window prior to the RO, so that channel access is secured beforehand. This allows the preamble to be transmitted immediately at the RO without additional LBT delay, thus reducing access latency while maintaining reliable channel access through the preliminary LBT check.

The patent applies dynamics by making the RO-SSB mapping flexible rather than fixed. The WTRU determines the mapping relationship between ROs and SSBs dynamically based on whether they share the same index. When an RO and its associated SSB have the same index, the WTRU can directly use that RO without switching, simplifying the process. This dynamic adaptation allows the system to reduce latency when possible while managing mapping complexity through conditional logic rather than rigid reconfiguration.

The patent eliminates the need for LBT at the moment of preamble transmission by performing the channel assessment in advance. The WTRU determines whether the channel is free during a time window before the RO, and if clear, proceeds with immediate preamble transmission at the RO without waiting for additional LBT. This preliminary action enables faster access speed while maintaining collision avoidance through the advance channel check, as the cleared channel state is utilized for the scheduled transmission.