20121115-bearers in lte
TRANSCRIPT
7/30/2019 20121115-Bearers in LTE
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Bearers in LTE
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Introduction
Multiple applications may be running in a
UE at the same time
each one having different QoS requirements In order to support multiple QoS
requirements
different bearers are set up within EPS each being associated with a QoS
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Bearers
Categories
Minimum Guaranteed Bit Rate (GBR) bearers
Non-GBR bearersClassification is based on the nature of the
QoS the bearers provide
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Bearers
GBR bearers
can be used for applications such as VoIP
an associated GBR value for which dedicated transmission resources are
permanently allocated at bearer
establishment/modification
Bit rates higher than the GBR may be allowed if resources are available
a Maximum Bit Rate (MBR) parameter
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Bearers
Non-GBR bearers
do not guarantee any particular bit rate
can be used for applications such as webbrowsing or FTP transfer
no bandwidth resources are allocated
permanently to the bearer
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Bearers
Each bearer hasan associated QoS Class Identifier
QCI
an Allocation and Retention Priority
ARP
QCI
characterized by priority, packet delay budget
and acceptable packet loss
The QCI label for a bearer determines the
way it is handled in the eNodeB
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Bearers
ARPThe ARP of a bearer is used for call
admission control
To decide whether or not the requested bearer
should be established in case of radio congestion
Governs the prioritization of the bearer
for pre-emption with respect to a new bearer
establishment request
Once a bearer is successfully established
a bearer’s ARP does not have any impact on the
bearer-level packet forwarding treatment
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Bearers
An EPS bearer has to cross multiple
interfaces
the S5/S8 interface from the P-GW to the S-GW,
the S1 interface
from the S-GW to the eNodeB,
the radio interface
from the eNodeB to the UE
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Bearers
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Bearers IP packets mapped to the same EPS
bearer
receive the same bearer-level packet
forwarding treatment
e.g. scheduling policy, queue management policy
Providing different bearer-level QoS thus
requires
a separate EPS bearer is established for eachQoS flow
user IP packets must be filtered into the
different EPS bearers.
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Bearers
Traffic Flow Templates: TFTs
Packet filtering into different bearers is based
on TFTsUse IP header information to filter packets
e.g. source and destination IP addresses,
Transmission Control Protocol (TCP) port numbers
Each packet can be sent down the respectivebearers with appropriate QoS
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Bearers
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Bearers
An UpLink TFT
UL TFT: associated with each bearer in the
UE
filters IP packets to EPS bearers in the uplinkdirection
A DownLink TFT
DL TFT: in the P-GW filters IP packets to EPS bearers in the downlink
direction