different directions. The device is listening to the network from only one direction, although in a real environment it might also be a beam-sweeping intersection. Eventually, the gNB's transmission direction and the device's reception direction becomes aligned in such a way that the device can correctly decode the SS block. Since the device knows the SS block time index, it can derive when and where to send a PRACH transmission, as shown in the right pane of the figure. Mapping between DL SS Blocks and corresponding UL resources for PRACH SS Block 1 SS Block 2 SS Block 3 SS Block 4 Same Tx beam direction as in the DL Tx beam Rx PSS, SSS and PBCH PRACH Transmission Figure 5.3 - Mapping between DL and UL beam directions when UL/DL reciprocity is reliable The network knows whether an SS block is transmitted in one spatial direction, and any devices listening to it transmit the PRACH at a specific time and with a specific set of resources. Hence, the gNB knows in advance that, at a given time, it must listen for the PRACH in the same direction as the corresponding SS block in the downlink it sends. This is the assumption for both the gNB and the device that will enable communication, without any prior knowledge of the physical location of any of them. Other remaining system information As we described before, an SS block carries synchronization signals and the PBCH. The PBCH contains the minimum system information, but that is not enough for a device to send the PRACH. More information will be needed. This is where the Remaining Minimum System Information Initial access and beam management (RMSI) comes in. The RMSI carries all the information that a device requires to access a network, and the minimum system information in the PBCH contains the basic information the device needs to decode the RMSI. The concept of beam sweeping is still used, and for each SS block, there is an RMSI transmitted in the same direction as the corresponding SS block. The RMSI is carried on the PBCH, as we discussed, and its configuration 