NG-RAN and 5G-NR

85G-NR Radio Interface – Data Link Layer

The data link layer is made up of four sublayers:

1. – SDAP (Service Data Adaptation Protocol);
2. – PDCP (Packet Data Convergence Protocol);
3. – RLC (Radio Link Control);
4. – MAC (Medium Access Control).

A level n sublayer provides services to the n + 1 layer.

Each level n layer receives data from the upper layer which it transfers to the lower layer by inserting control information in a header H.

Figure 8.1. Data link layer protocol. For a color version of this figure, see www.iste.co.uk/launay/5g.zip

The data received by the upper sublayer is referred to as Service Data Unit (SDU).

The frame transmitted to the lower sublayer comprises the SDU data to which control information is added.

8.1. SDAP protocol

Connectivity to a data network through 5G-NR radio access and the 5G Core network (5GC) is provided by a PDU (Packet Data Unit) session.

Figure 8.2. PDU session. For a color version of this figure, see www.iste.co.uk/launay/5g.zip

The PDU session is defined by:

1. – the format of the data to be transported (Ethernet, IP, unstructured);
2. – the SMF (Session Management Function) involved in the establishment of the sessions;
3. – the type of service in an S-NSSAI (Single – Network Slice Selection Assistance Information).

The PDU session consists ...