Section 2 - NR Protocols Flashcards
What are the functionalities of the SDAP layer
Service Data Adaptation Protocol: Is new to NR, mapping the N3 tunnel (between gNB and Core) into the air interface. Main role is to map quality of service flows into UL and DL packets. Transfers user plane data. There is an SDAP entity configured for each individual PDU session
How the routing of data is determined in NSA
The eps-bearer or sdap-config bearer determine how the data is routed
Can a Master Cell Group (MCG) DRB use the same bearer ID as a split DRB
No
For a split DRB, same ID is used for MCG and Secondary Cell Group (SCG)
Yes
(T or F) Is NAS control protocol terminated at SMF on the network side?
No, it is terminated at AMF
What are the functions of the NAS control protocol
NAS ciphering and integrity protection, registration management, connection management, reachability management, transport for session management between UE and SMF, access authentication and authorization, transport for SMS messages
What are the functions of the RRC
Broadcast system information; paging, initial security activation, establishment/modification/suspension/resumption/release of RRC connection, RRC connection mobility, establishment/modification/release of RBs carrying user data (DRBs), radio control configuration, recovery from radio link failure; inter-RAT mobility; measurement configuration and reporting
What is the name of the new connection state introduced in NR?
Inactive
How are the actions of going from Connected to Inactive and vice versa called?
Suspend and resume respectively
Which technology carries the initial NR RRC signaling in NSA
LTE RRC
Describe the process for connecting to NSA
Register in LTE -> Network ask to measure and report NR -> Network asks UE to register to NR -> Complete RACH procedure to complete NR adding
What are the three options for the control plane architecture for NSA
Basic method, where all 5G signalling is sent to LTE eNodeB which then puts it in a container and sent it on the LTE air interface. Enhancement 1, where all layers of the control plane are directly used in NR on a SRB. Enhancement 2, where the NR control plane is sent in a split SRB, with layers RLC and below done in NR
What are the three options for the user plane protocol stack architecture for NSA
Option 3, where the PDCP is anchored on LTE or eNodeB and connected to EPC and there is data in LTE and NR. Option 3a, with the MCG only used for signaling and all the data plane comes on the NR side. Option 3x, where the PDCP is anchored to gNB but data can be sent on both sides (most used)
What new functionalities where added to MAC layer in NR
Reordering and duplicate detection (changed from RLC in LTE), PDCP PDU routing for split bearers, and duplication of PDCP PDUs (allows to transmit the same packet in multiple layers), beam management
What are the physical signals in the uplink
DMRS, PTRS, SRS
