In the last chapter we learn about LTE User Plane Protocol stack, in this chapter we shall see LTE Control Plane Protocol Stack.
Below 2 images shows detailed description of Control Plane Protocol Stack.
Below is the simplified version of control plane protocol stack.
On a high level, the control plane protocol stack on the UE side is similar to User plane protocol stack, with an additional “NAS” and “RRC” layer.
The “NAS” layer from the UE side will communicate directly with MME “NAS” layer.
The “RRC” layer from the UE side will communicate with eND “RRC” layer.
The working of PDCP, RLC, MAC layer will remain same as we saw it in previous chapter.
We shall see the functions of “NAS”, “RRC” layers in detail.
1. PDCP : Packet Data Convergence Protocol
Below are few of the functions of PDCP Control plane layer:
1. Ciphering and Integrity Protection
2. Transfer of control plane data
2. NAS: Non-Access-Stratum (NAS) Protocol
3. RRC: Radio Resource Control (RRC)
Below are different types of Procedures available:
Physical Layer Procedure
1. Random Acess
2. PLMN selection/ Intr-Rat PLMN selection
3. Cell Selection and reselection/ Inter-RAT cell selection and reselection
4. Closed subscriber group cells.
RRC Layer Procedure:
1. RRC connection establishment
2. RRC connection release
3. RRC connection reconfigureation
4. Measurement configuration control and reporting
5. RRC others – Radio link failure
6. RRC others – Redirection to E-UTRAN
NAS Layer Procedure – EPS mobility management
1. Authentication procedure
2. Security mode control procedure
3. Identification procedure
4. Attach procedure
5. Detach procedure
6. Tracking area updating procedure; Service request procedure
7. Paging procedure
NAS Layer Procedure – EPS session management
1. Dedicated EPS bearer context activation
2. EPS bearer context modification
3. EPS bearer context deactivation
4. UE requested PDN connectivity
5. UE requested PDN disconnect
6. UE requested bearer resource allocation
7. UE requested bearer resource modification
Summary:
The user plane protocol stacks of the LTE-Uu are:
PDCP
RLC
MAC
PHY
For the control plane, the protocol stack is comprised of:
NAS
RRC
RLC
MAC
PHY
