User's Manual

Table Of Contents

Ver.

CHAPTER 2. System Overview

2600-00FKQFGA2

1.0

Handover Procedure

For more information on the handover procedure, see the ‘Message Flow’ section

below.

Admission Control (

AC)

The eNB provides capacity-based admission control and QoS-based admission control for

a bearer setup request from the EPC so that the system is not overloaded.

 Capacity-based admission control

There is a threshold for the maximum number of connected UEs (new calls/handover

calls) and a threshold for the maximum number of connected bearers that can be

allowed in the eNB. Call admission is determined depending on whether the connected

UEs and bearers exceed the thresholds.

 QoS-based admission control

The eNB determines whether to admit a call depending on the estimated PRB usage of

the newly requested bearer, the PRB usage status of the bearers in service, and the

maximum acceptance limit of the PRB (per bearer type, QCI, and UL/DL).

RLC ARQ

The eNB performs the ARQ function for the RLC Acknowledged Mode (AM) only.

When receiving and transmitting packet data, the RLC transmits the SDU by dividing it

into units of RLC PDU at the transmitting side and the packet is retransmitted (forwarded)

according to the ARQ feedback information received from the receiving side for increased

reliability of the data communication.

QoS Support

The eNB receives the QoS Class Identifier (QCI) in which the QoS characteristics of the

bearer are defined and the GBR, the MBR, and the Aggregated Maximum Bit Rate (UE-

AMBR) from the EPC. It provides the QoS for the wireless section between the UE and the

eNB and the backhaul section between the eNB and the S-GW.

Via the air interface, it performs retransmission

to satisfy the rate control according to the

GBR/MBR/UE-AMBR values, priority of bearer defined in the QCI, and scheduling

considering packet delay budget, and the Packet Loss Error Rate (PLER).

Via the backhaul interface, it performs QCI-based packet classification, QCI to DSCP

mapping, and marking for the QoS. It provides queuing depending on mapping results, and

each queue transmits packets to the EPC according to a strict priority, etc.

In the Element Management System (EMS), in addition to the QCI predefined in the

specifications, operator-specific QCI and QCI-to-DSCP mapping can be set.

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