06 RA41216EN40GLA0 Admission Control

Admission Control LTE Radio Parameters RL40

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© Nokia Siemens Networks

RA41216EN40GLA0

Contents 1. LTE Functionalities & Features Overview 2. Parameters Structure & SIBs 3. Physical Channel Configuration & Random Access 4. UE State Handling 5. Bearer Management 6. Admission Control 7. Power Control & Power Setting 8. Adaptive Modulation & Coding 9. MIMO Mode Control 10. Idle Mode Mobility 11. Connected Mode Mobility 12. Scheduler 13. SON 4


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Index •Task of Radio Admission Control •Admission Control Algorithms and Thresholds

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Radio Admission Control Introduction (1/3) • Scope of RAC is cell level • RAC algorithms controls establishment of – Signaling radio bearer – Data Radio Bearer

• RAC controls number of UE in a cell – Number of established RRC connection per cell – Number of active UEs (users) per cell

• RAC controls number of DRB in a cell – Number of data radio bearers (DRB) – Number of DRB with QCI=1

• RAC controls emergency calls and emergency sessions – Special margin considered for emergency calls – Special margin considered for IMS emergency sessions (RL30)

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DRB: Data Radio Bearer SRB: Signalling Radio Bearer

Radio Admission Control Introduction (2/3) • RAC applies different criteria for call estblishment and Mobility (HO) – offset in terms of number of rrc connections or active users used, etc – aim is to keep the already established sessions active and support user mobility

• RAC interacts with other RRM entities – – – –

Packet Scheduler Mobility management Radio Bearer Management UE State Management

• RAC acts based on events like: – paging – Handover Request – Call establishment request 7


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Radio Admission Control Introduction (3/3) RL40 • Smart Admission Control – Necessity when offering high bit rate services – Configuration of access control threshold per cell simplified for GBR traffic – RAC reacts on measurements and therefore is adapted in a dynamic way – Congestion control function allows more optimistic admission decisions, and the system corrects overbooking situations using preemption according to priorities (Radio)

• ARP based admission Control – Prioritize the availability of different services  Lower availability services may be offered without jeopardizing higher available services  ‘Must’ availability services like emergency sessions need no dedicated (reserved) resource – Dynamic adaptation of resources to actual need 8


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Service management High RB requests with congestion control by using of priority and smart admissions Rejected UE requests due of too high RB utilization  Only for QCI 2-4 S-RAC  Not for VoIP

Descriptions / Objective: To admit or to reject the requests for esta0blishment of Radio Bearers (RB) on a cell basis Based on number of RRC connections and number of active users per cell and allocation and retention priority (ARP)

ARP = Allocation and retention/maintenance Priority

Smart Admission control

• S-RAC only for GBR traffic

to avoid congestion on ‘guaranteed’ resources • Counter based RAC will not work in case of serving high bit rate users  Replaced by a measurement based function • S-RAC predicts load required/caused by each new GBR radio bearer – Reflecting requested transmission rates in UL/DL under given radio conditions – Considering existing GBR load

• S-RAC offers congestion handling when overbooking of resources is detected e.g. – Radio conditions of high bit rate users getting worse – Too optimistic admission was done – Bursting traffic cannot be served over time.

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RA41216EN40GLA0

Index •Task of Radio Admission Control •Admission Control Algorithms and Thresholds

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Radio Admission Control • RL20 RAC checks against operator configurable thresholds – on Call Establishment:     

max_number_of_rrc_connection max_number_of_rrc_connection_emergency_calls (LTE22 supported) max_number_of_active_users max_number_of_active_DRB (LTE7 supported) max_number_of_QCI1_DRB (LTE10 supported)

– on Intra-Frequency (incoming) Handover:  additional offsets can be defined for • time critical handover (event A5) • handover desired for radio reasons (event A3)  „all or nothing“ – SRB && DRB must be admitted in target cell

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LTE7: Support of multiple EPS bearers LTE10: Conversational Voice LTE22: Emergency Call Handling

RL20 Admission of SRB1 •

RAC compares the number of currently allocated RRC connections in the cell against following parameter: Name maxNumRrc

(LNCEL)

Range 0...840, step 1

Default 240 (420)*

Description Maximum number of UEs in the cell with an established RRC connection. Note*: min(ulChBw,dlChBW) is set to value '20 MHz'

• Admission Control criteria for Signalling Bearer: Number of currently established RRC connections < maxNumRrc

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Admission of SRB1 if min(ulChBw,dlChBw) has value ' 5MHz' and '10 MHz' - maxNumRrc value range is restricted to 0...480 (default value 240) - maxNumRrc+max(addAUeRrHo, addAUeTcHo) <= 480

if min(ulChBw,dlChBw) has value '15 MHz ' and '20 MHz' - maxNumRrc value range is restricted to 0...840 (default value 420) - maxNumRrc+max(addAUeRrHo, addAUeTcHo) <= 840

addAUeRrHo

addAUeTcHo

Additional # of active UEs, which are allowed to access a cell via handover with HO cause: "HO desirable for radio reasons", when RRC connection (maxNumRrc) or active UE (maxNumActUE) limit already reached. LNCEL; 0...840;1; 15

Additional # of active UEs, which are allowed to access a cell via handover with HO cause: "Time critical handover", when RRC connection (maxNumRrc) or active UE (maxNumActUE) limit already reached LNCEL; 0...840;1; 20

„0“ implies that no admission priority is granted for UEs accessing the cell via HO 13


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RL20 Admission of SRB1 for Emergency Call •

RAC compares the number of currently allocated RRC connections in the cell against following parameter: Range

Name maxNumRrcEme rgency

0...840, step 1

Default 440 (800)*

(LNCEL)

Description

Maximum number of UEs in the cell which may establish a RRC connection for an emergency call. Note*: min(ulChBw,dlChBW) is set to value ‚15 MHz‚ or '20 MHz'

• Admission Control criteria for Signalling Bearer: Number of currently established RRC connections < maxNumRrcEmergency Note: maxNumRrcEmergency should be greater than the actual configured threshold maxNumRrc

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LTE22: Emergency Call Handling

RL20 Admission of Single non-GBR radio bearer • •

As part of the S1AP initial context setup, the bearer management function requests RAC to admit the single non-GBR data radio bearer setup request for UEs for which the SRB1 and SRB2 have been successfully established. RAC compares the number of currently UEs with established DRB in the cell against following parameter: Range

Name maxNumActUE

(LNCEL) •

0...840, step 1

Default 120 (240)

Description Maximum number of UEs in the cell with established DRB. Note: default 240 for 20MHz

Admission Control criteria for non-GBR radio bearer:

number of currently active UEs < maxNumActUE

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Admission of single non-GBR radio bearer if min(ulChBw,dlChBw) has value '10 MHz' - maxNumActUE value range is restricted to 0...480 (default value 120) - maxNumActUE +max(addAUeRrHo, addAUeTcHo) <= 480

if min(ulChBw,dlChBw) has value '20 MHz' - maxNumActUE value range is restricted to 0...840 (default value 240) - maxNumActUE +max(addAUeRrHo, addAUeTcHo) <= 840

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addAUeRrHo

addAUeTcHo

Additional # of active UEs, which are allowed to access a cell via handover with HO cause: "HO desirable for radio reasons", when RRC connection (maxNumRrc) or active UE (maxNumActUE) limit already reached. LNCEL; 0...840;1; 15

Additional # of active UEs, which are allowed to access a cell via handover with HO cause: "Time critical handover", when RRC connection (maxNumRrc) or active UE (maxNumActUE) limit already reached LNCEL; 0...840;1; 20


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RL20 Admission of Multiple EPS bearers • •

The bearer management function requests RAC to admit the Data Radio Bearer setup request for UEs for which the SRB1 and SRB2 have been successfully established. RAC compares the number of currently established DRB in the cell against following parameter: Range

Name maxNumActDrb

(LNCEL) •

0...4200, step 1

Default 360 (720)

Description maximum number of established DRBs in the cell. Note: default 720 for 20MHz

Admission Control criteria for Multiple EPS bearers:

number of currently established DRBs < maxNumActDrb

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LTE7: Support of multiple EPS bearers

Admission of Multiple EPS bearers If dlChBw is set to '5 MHz' or '10 MHz'

- maxNumActDrb + max(addNumDrbRadioReasHo, addNumDrbTimeCriticalHo) <= 2400

If dlChBw is set to '15 MHz' or '20 MHz'

- maxNumActDrb + max(addNumDrbRadioReasHo, addNumDrbTimeCriticalHo) <= 4200

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addNumDrbRadioReasHo

addNumDrbTimeCriticalHo

Additional margin for the maximum number of active DRBs in the cell accessing the cell via HO with HO-cause: "HO desirable for radio reasons“. LNCEL; 0...4200;1; 35

Additional margin for the maximum number of active DRBs in the cell accessing the cell via HO with HO-cause: "Time Critical HO". LNCEL; 0...4200;1; 60


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RL20 Admission of QCI1 Conversational bearers • •

The bearer management function requests RAC to admit the data radio bearer setup request for UEs‘ conversational voice RAC compares the number of currently established QCI=1 DRB in the cell against following parameter:

Range

Name maxNumQci1Drb

•

Default

0...200, step 1

100

Description Max Number QCI1 DRBs (GBRs)

(LNCEL) Admission Control criteria for QCI=1 Conversational EPS bearers:

number of currently established QCI=1 DRBs < maxNumQci1Drb

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LTE10: Conversational Voice

Admission of QCI1 Conversational bearers If dlChBw is set to '5 MHz' - maxNumQci1Drb + max( addNumQci1DrbRadioReasHo, addNumQci1DrbTimeCriticalHo) <= 150, If dlChBw is set different to '5 MHz' - maxNumQci1Drb + max( addNumQci1DrbRadioReasHo, addNumQci1DrbTimeCriticalHo) <= 200

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addNumQci1DrbRadioReasHo

addNumQci1DrbTimeCriticalHo

Additional margin for the maximum number of active DRBs in the cell accessing the cell via HO with HO-cause: "HO desirable for radio reasons“. LNCEL; 0...200;1; 15

Additional margin for the maximum number of active DRBs in the cell accessing the cell via HO with HO-cause: "Time Critical HO". LNCEL; 0...200;1; 20


RA41216EN40GLA0

Radio Bearer Management • Main feature of RL20 is retrieval & utilisation of UE capabilities in RRM – A Layer 3 RRC signaling procedure – 3GPP TS 36.306 defines UE capabilities eNB

UE

RRC: UECapabilityEnquiry Ue-RadioAccessCapRequest (eutra)

RRC: UECapabilityInformation {(eutra, ueCapabilitesRAT-Container (UE-EUTRA-Capability)), optional UE capabilitities for other RAT types}

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Radio Bearer Management • Radio Admission Control may select UL/DL maximum bitrates for a UE: – based on UE capability information received from UE (mbrSelector=0) – based on O&M parameters maxBitRateUl and maxBitRateDl (mbrSelector =1) mbrSelector LNCEL; 0 (ueCapability), 1 (OaM) ; 0

• The max. Bitrate for a UE in UL & DL for all radio bearers incl. SRBs are limited to O&M parameter setting:

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maxBitRateDl

maxBitRateUl

LNCEL; 50…300000kbps;50 ; 170000 Kbps

LNCEL; 50…75000kbps;50 ; 50000 Kbps


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Radio Admission Control for Intra-Frequency HO • For LTE intra-frequency handover there can be separate admission control thresholds defined depending on HO trigger cause:

– Time Critical Handover – flag is set when HO trigger is event A5 (urgency is „high“ for coverage handover (event A5))

– Handover Desirable for Radio Reasons – flag is set when HO trigger is event A3 (urgency is „low“ for power budget handover (event A3))

• Better to support the call with Handover rather than rejecting and/or dropping

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Radio Admission Control for Intra-Frequency HO Definition of new admission control threshold for time critical HO: • HoThreshRrc = maxNumRrc + max(addAUeTcHo, addAUeRrHo) • HoThreshUe = maxNumActUe + max(addAUeTcHo, addAUeRrHo) • HoThreshDrb = maxNumActDrb + max(addNumDrbRadioReasHo, addNumDrbTimeCriticalHo) • HoThreshGbr = maxNumQci1Drb + max( addNumQci1DrbRadioReasHo, addNumQci1DrbTimeCriticalHo)

If

NumRRC < HoThreshRrc (SRB1 &2) AND NumActUE < HoThreshUe (Single Non-GBR RB) AND NumActDrb < HoThreshDrb (Multiple EPS bearers) AND NumQci1Drb < HoThreshGbr (Conversational Voice) then admit HO request in target cell Otherwise reject HO request for target cell

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Smart admission Control RL40

• Smart Radio Admission Control – Default: max 75% of PRBs (air transmission resources) available for GBR traffic – RAC checks unchanged compared to RL40  Amount of RRC_Connections (SRBs)  Amount of active Ues  Amount of active DRBs

– New

maxGbrTrafficLimit Maximum radio resource consumption (PRBs) for GBR traffic in UL and DL LNCEL; 30... 90; 75

addGbrTrafficRrHo

 Estimation of needed resources for GBR-DRBs  Load measurements are base for admission decision  Max. amount of GBR-DRBs (CR ongoing)

Additional margin on the threshold "maxGbrTrafficLimit" in case of handover for radio reasons. LNCEL; 0... 30; 5

addGbrTrafficRrHo Additional margin on the threshold "maxGbrTrafficLimit" in case of handover for time critical reasons . LNCEL; 0... 30; 10

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Smart admission Control RL40

– GBR-DRB admission takes into account:  Requested bit rate UL/DL (incl. corrections for header info, etc)  Radio conditions derived from CQI information etc (=> transmission efficiency in bits/PRB)  Current load in cell (available PRB resources)  Configured threshold for GBR traffic – Congestion Handling  If GBR-traffic cannot be scheduled according to QoS requirements RAC is informed to select candidates (with the help of ARP-AC) to be kicked out in order to free resouces.

– Emergency Handling:  No resources reserved for emergency traffic, because this is handled by ARP-AC

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Smart admission Control RL40 Estimate throughput capacity

•

eNodeB estimates throughput per capacity efficiency; kbit/s possible per RB from CQI / SINR

•

eNodeB knows GBR requested by new user

•

eNodeB calculates from efficiency number of RBs to fulfill requested GBR

GBR-DRB request is admitted when;

User requested GBR

Calculate required RB

no

Refer to ARP for possible pre-emption

Is # PRBs required less than PRB max – reserved ?

yes

k

( PRB i  PRB new)  PRB max  PRB res i 1

PRB new 

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grossreqbitrate transm.efficiency RA41216EN40GLA0

Admit bearer

ARP Based Admission Control –RL40

• Basic rules for preemption (according to 3GPP) – Priority Level  Values between 1 and 14  1  highest priority; 14  lowest priority  Only E-RABs with lower priority may be preempted  Note: Value 15 is ‘no priority’ and correspond to preemption capability and vulnerability unset maxNumPreEmptions – Preemption Capability Limits the number of pre-emptions which  If set, this E-RAB may preempt others the admission of a set of E-RABs may cause. – Preemption Vulnerability LNBTS; 1..32; 20  If set, this E-RAB may be preempted by others

• LTE534 extension to 3GPP rules – If preemption needed, useful and allowed, it shall happen – Preemption done in order of decreasing priority level for vulnerable E-RABs – Multiple vulnerable E-RABs with same priority, the most resource consuming shall be preempted first

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ARP Based Admission Control –RL40 • Examples – Example 1: Single commercial operator  Offered services: • Background TCP-based data transfer (e.g. e-mail, ftp, ..) • Foreground TCP-based data transfer (e.g. Web browsing, chat) • Conversational video (live streaming) • Conversational voice • Emergency calls – Proposed ARP Settings

Service

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Priority level

Capability

Vulnerability

Emergency calls

7

Y

N

Conversational voice

10

Y

Y

Conversational video

12

Y

Y

Foreground data

12

Y

Y

Background data

14

N

y


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ARP Based Admission Control –RL40 • Examples – Example 2: Single commercial operator and one public safety (PS) operator  Additional offered services compared to example 1 : • PS Background TCP-based data transfer (e.g. e-mail) • PS Foreground TCP-based data transfer (e.g. database access) • PS Conversational voice • PS Emergency calls – Proposed ARP Settings

Service

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Priority level

Capability

Vulnerability

PS Emergency calls

2

Y

N

PS Conversational voice

4

Y

Y

PS Foreground data

5

Y

Y

PS Background

6

Y

Y

Emergency calls

7

Y

N

Conversational voice

10

Y

Y

remaining table see example 1 .

.






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ARP Based Admission Control –RL40 Emergency session handling ARP based admission control for E-RABs means no reserved resources for IMS emergency session E-RABS are longer necessary. Therefore, the eNB capacity for normal E-RABs can be used more effectively. Values for ARP handling for emergency IMS sessions done on a per PLMN basis. LNBTS managed object;

• • •

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emerSessArpPreemCap Whether a service data flow can get resources that were already assigned to another service data flow with a lower priority level. emerSessArpPreemVul Defines whether a service data flow can lose the resources assigned to it in order to admit a service data flow with higher priority level. emerSessArpPrioLev For emergency sessions, only ARP priority levels 1-8 may be applied


RA41216EN40GLA0

06 RA41216EN40GLA0 Admission Control

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