System Description

Confidential
Chapter 1 Samsung LTE System Overview
SOL230 System Description v1.0 2
Copyright © 2017, All Rights Reserved.
Figure 1. Functional Distinctions of E-UTRAN and EPC
S1
MME
S-GW
P-GW
EPC
eNB
E-UTRAN
Packet Filtering
UE IP address allocation
Mobility Anchoring
NAS Security
Idle State Mobility
Handling
EPS Bearer Control
Inter Cell RRM
RB Control
Connection Mobility Cont.
Radio Admission Control
eNB Measurement
Configuration & Provision
Dynamic Resource
Allocation (Scheduler)
RRC
PDCP
RLC
MAC
PHY
eNB
The eNB is a logical network component of Evolved UTRAN (E-UTRAN), which
is located on access side in the LTE system.
The eNBs can be interconnected with each other by X2 interface. The eNBs are
connected by S1 interface to the Evolved Packet Core (EPC).
The wireless protocol layer of eNB is divided into layer 2 and layer 3. The layer 2
is subdivided into Media Access Control (MAC) layer, Radio Link Control (RLC)
layer, and PDCP layer, each of which performs independent functions. Also,
layer3 has Radio Resource Control (RRC) layer.
The MAC layer distributes air resources to each bearer according to its priority. It
also performs multiplexing function and HARQ function for the data, which is
received from the multiple upper logical channels.
The RLC layer performs the following functions:
 Segments and reassembles the data, which is received from PDCP layer under
the size specified by MAC layer
 Requests retransmission to recover if data transmission fails in the lower layer
(ARQ)
 Reorders the data recovered by performing HARQ in MAC layer (re-ordering)
The PDCP layer performs the following functions:
 Compresses and decompresses a header
 Encrypts/decrypts user plane and control plane data
CONFIDENTIAL