User's Manual

Ver.
CHAPTER 1. Samsung LTE System Overview
2600-00FKQFGA2
1.0
The figure below shows the functional distinctions between the eNB of E-UTRAN, MME,
S-GW, and P-GW according to the 3GPP standard. The eNB has a layer structure and the
EPC has no layer.
Figure 1. Functional Distinctions of E-UTRAN and EPC
eNB
An eNB is a logical network component of the Evolved UTRAN (E-UTRAN) which is on
the access side in the LTE system.
eNBs can be interconnected with each other by means of the X2 interface. The eNBs are
connected by means of the S1 interface to the Evolved Packet Core (EPC).
The wireless protocol layer of the eNB is divided into layer 2 and layer 3. Layer 2 is
subdivided into the Media Access Control (MAC) layer, the Radio Link Control (RLC)
layer, and the PDCP layer, each of which performs independent functions. Layer3 has the
RRC layer.
T
he MAC layer distributes air resources to each bearer according to its priority, and
performs the multiplexing function and the HARQ function for the data received from the
multiple upper logical channels.
T
he RLC layer performs the following functions.
 Segments and reassembles the data received from the PDCP layer in accordance with
the size specified by the MAC layer
 Requests retransmission to recover if data transmission fails in the lower layer (ARQ)
 Reorders the data recovered by performing HARQ in the MAC layer (re-ordering)
S1
MME
NAS Security
Idle State Mobility
Handling
EPS Bearer Control
S-GW
Mobility Anchoring
P-GW
Packet Filtering
UE IP address allocation
EPC
eNB
Inter Cell RRM
RB Control
Connection Mobility Cont.
Radio Admission Control
eNB Measurement
Configuration & Provision
Dynamic Resource
Allocation (Scheduler)
RRC
PDCP
RLC
MAC
PHY
E-UTRAN
© SAMSUNG Electronics Co., Ltd.
page 9 of 72