An Introduction to 5G

13Registration Procedures

We will now move on to a set of seven chapters that cover the end‐to‐end operation of 5G. Throughout these chapters, the main focus will be on architectural options that involve the 5G core network, although we will restrict some aspects to architectures that require a master gNB. To keep things simple, we will mainly assume the use of an integrated gNB, but we will discuss what happens if the gNB is split into central and distributed units as part of Chapter 18. We will also address inter‐operation with the evolved packet core in Chapter 19.

The main specification for these discussions is TS 23.502 [1], which covers the signalling procedures within the 5G core. The equivalent procedures in the radio access network (RAN) form part of TS 38.300 [2], while full details of the resulting signalling are in the corresponding stage 3 specifications, which were laid out in Chapters 2 and 3. The use of service‐based interfaces and HTTP/2 makes the core network's signalling more intricate than in previous generations, and readers may wish to review the discussion of HTTP/2 in Chapter 2 before proceeding.

In this chapter, we will address the procedures by which the mobile registers with the 5G core network when it switches on. In doing so, we will cover the procedures for network and cell selection, for the establishment of a radio resource control (RRC) signalling connection with the RAN and for registration itself. As part of the discussion, we will address ...