LTE Quality of Service | LTE QoS Class Identifier
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This page describes LTE Quality of Service(QoS) basics, mentions GBR and non GBR LTE bearers and QoS class identifier(QCI). It covers QCI-1, QCI-2, QCI-3, QCI-4, QCI-5, QCI-6, QCI-7, QCI-8 and QCI-9.
LTE QoS allows both LTE compliant subscribers and services to be differentiated.
Premium subscribers can be priotized over basic subscribers. Real time services can
be prioritized over non realtime services.
As we know unloaded network will not create any problems to LTE subscribers as per as service provision is concerned. The real challenge is when network gets congested. This is the time when LTE QoS comes in place. As the network load will increase, prioritization determines which subscribers and performing well and which are not performing.
Like other systems, LTE QoS also impacts admission control decisions. Connections with guaranteed QoS require larger resources. These connections will be blocked in case of insufficient resources.
Table-1 mentions QoS parameters associated with each LTE bearer type. QoS is applied between UE and PDN gateway within LTE network.
|QoS Class Identifier||Supported||Supported|
|Allocation and Retention Priority||Supported||Supported|
|Guaranteed Bit rate||Supported|
|Maximum Bit rate||Supported|
|APN Aggregate Maximum Bit rate||Supported|
|UE Aggregate Maximum Bit rate||Supported|
Table-2 below represents relationship between QCI and associated set of QoS characteristics. 3GPP has adopted this to reduce both the signalling requirement and maximum no. of possible parameter combinations.
LTE QCI-1 to QCI-9
|LTE QCI||Resource Type||Priority||Packet Delay Budget||Packet Error Loss Rate||Example Services|
|QCI-2||4||150ms||10-3|| live streaming of conversational voice
|QCI-3||3||50ms||Real time gaming|
|QCI-4||5||300ms||10-6||Non conversational video(Buffered streaming)|
|QCI-6||6||300ms||Video (buffered streaming),TCP based applications|
|QCI-7||7||100ms||10-3||Voice, video (live streaming) , interactive gaming|
|QCI-8||8||300ms||10-6||Video (Buffered streaming) , TCP based applications|
As mentioned LTE QCI determines which bearers are categorized as GBR and which as non GBR. The priority associated with each QCI is applied when forwarding packets across the LTE network. A priority of 1 corresponds to highest one.
Packet delay budget defines upper bound for packet delay between UE and PCEF with PDN gateway. Average delay between eNodeB and PCEF of 20ms is assumed and rest of the delay budget is available for RAN.
LTE QCI table-2 mentions packet error loss rate. It is defined as % of higher layer packets which are lost during periods during when network is not congested.
LTE QoS References: 3GPP TS 36.300, 3GPP TS23.401,3GPP TS23.203