From the course: 5G Accessibility KPI Engineering and Optimization

Initial access procedure

From the course: 5G Accessibility KPI Engineering and Optimization

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Initial access procedure

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(bright music) - [Instructor] The second step comes in a 5G call flow is the radio resource control. Before any data can flow, whether it is browsing the web, initiating a voice call, or adjusting with the code network, the user device must first access the radio network. And in this case, after the RACH, there is a three step procedure comes into picture for RRC, which includes the RRC setup request, RRC setup message goes from gNodeB to the user, and RRC setup completion. And this three step procedure makes a control plane between the user and the gNodeB. The first step is the RRC connection request, and this message is sent when the UE wants to establish a connection to the network to either sending certain data. It also used when responding to a paging message, or of course beginning any network registration. This message is being transmitted over the common control channel and then after it includes certain information about the user identity, which is a temporary identity at this particular stage during RRC connection request. It includes the reason for this establishment, why user wants to connect to the network, what kind of registration it is. It's a mobile originated signaling, or it is a paging where it is a mobile terminating messages. The second step is the RRC connection setup, where the SRB-1, which is signaling radio bearer one is being sent and it upgrades the signaling capabilities for ongoing RRC messages. It also includes configuration for bandwidth parts, et cetera. This message gives the user device a green light to establish a robust control plane communication path. Then there is a RRC connection setup complete message, which comes from the user device to the gNodeB. It activates the SRP-1 and finalize its configuration. Now it encapsulates the NAS registration request inside this message, which is marking the start of a UE interaction with the core network. So in summary, the three-step position includes the RRC connection request, which is a initial access. The second step is a RRC connection setup to allocate certain resources from the network to the user. And then there's the last step, which finalize the setup and register with the core network via NAS registration message.

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