LTE RRC Message Journey – Wrapping & Unwrapping of Protocol Layers (Explained Layer by Layer)
Opening Hook (Catchy Start):
“When a UE sends an RRC message… does it travel straight to the eNodeB’s RRC layer?
No! It takes a layered ride — wrapping and unwrapping itself like a courier parcel!”
Let’s explore how each protocol layer adds value, one wrap at a time —
and how the eNodeB unwraps it layer by layer till it reaches the RRC gate! 
The Core Analogy: Parcel Wrapping & Delivery
Imagine you want to send a shirt (RRC Message) to your friend (eNodeB).
You don’t just throw the shirt across the street, right?
You wrap it:
First with a plastic cover (PDCP)
Then a cardboard box (RLC)
Stick address & courier info (MAC)
Hand over to delivery van (PHY)
Send across the road (Air Interface)
Your friend unwraps layer by layer until the shirt is in their hands!
That’s exactly what happens in LTE!
UE Side: Layer-by-Layer Wrapping (Encapsulation)
As the UE generates an RRC message, it’s not sent alone.
It is wrapped by protocol layers — one after the other — before hitting the air interface.
RRC Layer (Application)
Creates the RRC Connection Request, the actual content to be delivered.
PDCP Layer
Adds sequence numbers, applies ciphering, and integrity protection.
Think: Clean packaging + tracking seal.
RLC Layer
Splits or reassembles data into chunks, adds segment info.
Think: Parcel might be broken into parts to fit transport rules.
MAC Layer
Adds channel ID, scheduling, priority — to help transmission.
Think: Address label and dispatch priority.
PHY Layer
Converts message to radio signals, with modulation & coding.
Think: Delivery van moves it on real road — wireless spectrum!
End Result:
By now, your tiny RRC message is a heavily wrapped, protocol-compliant, protected unit ready to fly.
Air Interface: Over-the-Air Delivery
- Air Interface = Wireless channel = The road
Just like parcels go through traffic, signals go through fading, interference, noise
That’s why such strong wrapping is needed in the first place!
eNodeB Side: Layer-by-Layer Unwrapping (De-encapsulation)
Now eNodeB acts like a professional delivery guy — opening each layer:
PHY Layer
Demodulates and decodes signal — removes radio wrapping.
MAC Layer
Checks logical channel ID, removes MAC label.
RLC Layer
Reassembles pieces if needed, removes its header.
PDCP Layer
Decrypts, validates integrity, removes PDCP headers.
RRC Layer
Receives the actual RRC Connection Request — mission accomplished!
Layer Stack Summary:
Stage What’s Added/Removed Purpose
RRC Message Signaling & Control
PDCP Header, Ciphering Security & Reordering
RLC Header, Segments Fragmentation/Reassembly
MAC Scheduling Info Multiplexing + Prioritization
PHY Modulation, Coding Radio Transmission
LinkedIn: 