System Description

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Chapter 2 SOL230 Overview
SOL230 System Description v1.0 13
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(MIB) and System Information Blocks (SIBs), which are system information, to
allow the UE that receives them to perform proper call processing.
Call Control and Air Resource Assignment
The SmallCell allows the UE to be connected to or disconnected from the network.
When the UE is connected to or released from the network, the SmallCell
transmits and receives the signaling messages required for call processing to and
from the UE via the Uu interface, and to and from the EPC via the S1 interface.
When the UE connects to the network, the SmallCell performs call control and
resource allocation required for service. When the UE is disconnected from the
network, the SmallCell collects and releases the allocated resources.
Handover
The SmallCell supports intra-frequency or inter-frequency handover between
intra-SmallCell cells, and S1 handover between SmallCells. It also processes
signaling and bearer for handover. At intra-SmallCell handover, handover-related
messages are transmitted via internal SmallCell interfaces at S1 handover, via the
S1 interface.
To minimize user traffic loss during S1 handovers, the SmallCell performs the data
forwarding function. The source SmallCell provides a forwarding method to the
target SmallCell: indirect forwarding via the S1 interface.
The SmallCell allows the UE to receive traffic without loss through the data
forwarding method at handover.
Admission Control
The SmallCell provides capacity-based and QoS-based Admission Control(AC)
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 allowed in the SmallCell. Call admission is determined depending on
whether the connected UEs and bearers exceed the thresholds.
 QoS-based admission control
The SmallCell determines whether to admit a call based 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 SmallCell performs the Automatic Repeat Request (ARQ) function for the
RLC Acknowledged Mode (AM) only.
When receiving and transmitting packet data, the RLC transmits the SDU by
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