ink grant can be implicitly reused according to the periodicity defined by RRC, until deactivated (see Fig. 4.26). When a configured uplink grant is active, if the UE cannot find its C-RNTI/CS-RNTI on the PDCCH(s), an uplink transmission according to the configured uplink grant can be attempted. Otherwise, if the UE finds its C-RNTI/CS-RNTI on the PDCCH(s), the PDCCH allocation overrides the configured uplink grant. Retransmissions other than repetitions are explicitly allocated via PDCCH(s). When carrier aggregation is configured, one configured uplink grant can be signaled per serving cell. Similarly, when bandwidth adaptation is configured, one configured uplink grant can be signaled per BWP. In each serving cell, there can be only one configured uplink grant active at a time. A config- ured uplink-grant for one serving cell can either be of Type 1 or Type 2. For Type 2, activa- tion and deactivation of configured uplink grants are independent among the serving cells. When SUL is configured, a configured uplink grant can only be signaled for one of the two uplink carriers of the cell [11]. 4.1.4 Synchronization Signals In order to connect/attach to the network, a UE must perform initial cell search and down- link synchronization. The objective of initial cell search is to find a strong cell signal for connection establishment, to obtain an estimate of frame timing, to obtain cell identification, and to find the reference signals for coherent demodulation of PBCH and PDCCH. For this purpose, the PSS and SSS are used. The PSS and SSS are transmitted in SSBs together with PBCH. The blocks are transmitted per slot at a fixed slot location. During initial cell search, the UE correlates the received signals and the synchronization signal sequences by means 478 Chapter 4 Secondary synchronization signal Primary synchronization signal Physical layer cell identity (PCI) Figure 4.27 Derivation of PCI based on PSS and SSS sequences [6]. of matched filtering and attempts to locate the PSS in order to obtain symbol and hal