Capacity Management
Outline
Overview
Capacity Management Functions -
Dedicated Monitored Resource Handling Admission Control Congestion Control
Outline
Overview
Capacity Management Functions -
Dedicated Monitored Resource Handling Admission Control Congestion Control
Overview Capacity Management is responsible for the control of the load in the cell. It consists of 3 main functions:
Dedicated Monitored Resource Handling:
tracks utilization of
critical resources of the system.
Admission Control:
Congestion Control:
accepts/refuses admission requests based on the current load on the dedicated monitored resources and the characteristics of the request detects/resolves overload situations
Congestion Control
Admission Control Parameters
Dedicated Monitored Resource Handling
Capacity Management
Overview Capacity Management Architecture Overview
Capacity Management functionality is located in the RNC.
The controlling RNC is responsible for the load and congestion control of its cells and the execution of the admission control.
Dedicated Monitored Resources The Dedicated Monitored Resources Handling function is responsible for collecting and providing information about the utilization of resources that are critical to the load of the cell: by performing event-based and periodic measurements by keeping track of every link setup, addition, deletion and modification in the cell.
Dedicated Monitored Resource Handling Monitoring Algorithm Update Cell Load Information →Downlink channelization codes Monitor →Histogram Monitor →Downlink Transmitted Carrier Power →All interface Speech Equivalents (ASEs) →Uplink Received Total Wideband Power (RTWP) →RBS hardware utilization
Measurements
Dedicated Monitored Resources Resources monitored under the Capacity Management scope:
Downlink Channelization Codes Monitor: provides a measure for code tree utilization in DL.
Histogram Monitor: keeps track of -
-
-
SF usage in the DL: tracks the number of connections using a certain SF (except SF=16, reserved for HSDPA connections). SF usage in the UL Number of Compressed Mode radio links: used to avoid too much interference from the compressed mode radio users. Number of users allocated to the HS-DSCH
Dedicated Monitored Resources
Downlink Transmitted Carrier Power Monitor: monitors the total amount of Non-HS downlink transmitted carrier power in the cell.
All interface Speech Equivalent (ASE) Monitor: accounts for the air interface resources usage for DL and UL. The ASE of a radio link depends on the connection type and is expressed in terms of the equivalent number of speech radio bearers that generate the same amount of air interface load.
Uplink received total wideband power (RTWP): provides information to Congestion Control regarding uplink interference.
RBS Hardware Monitor: HW is a limited resource that depends on the amount of installed HW (channel elements) and the licensing restrictions.
Admission Control
Admission control accepts or refuses requests for utilization of dedicated monitored resources. It is performed on cell basis. The admission requests are initiated when: -
A new connection is set up. An existing connection is modified. Soft Handover is performed.
The request for admission specifies the amount of resources that the radio connection requires: -
Setup type: handover or new connection. Service Class: guaranteed, guaranteed-hs or non-guaranteed service. Compressed mode resources requested if any. Downlink Transmitted Carrier Power requested if any. Downlink Channelization Code resources requested if any. ASEs in uplink and downlink if any.
The requirements are compared to the available resources and the configured
Admission Control RAB request over the Iur interface 1. RAB request sent from SRNC to CRNC by means of RNSAP message over the Iur interface. 2. RNSAP is converted into RBs and DCHs attributes. 3. Required monitored resources are estimated on the basis of the set of DCHs and admission requested for those resources. 4. If request is admitted, the CRNC allocates necessary resources. 5. Admission Control informs SRNC by means of RNSAP message.
Admission Control
Admission control is responsible for -
-
Dividing the available resources among the non-guaranteed connections. Differentiating access to guaranteed, guaranteed-hs and non-guaranteed connections. Reserving part of the dedicated monitored resources for handover connections. Non-guaranteed
Guaranteed
Guaranteed-hs
Traffic class ‘background ‘ or ‘interactive’
Traffic class ‘conversational’ or ‘streaming’
HSDPA service
(Example: FTP and internet web services)
(Example: speech and video services)
NonHandover
Best effort services. New connections.
New connections
New connections.
Handover
Best effort services. Add radio link for existing connections in new cells.
Add radio link for existing connections in new cells.
Add radio link for existing connection in new cell.
Combinations of requests for admission depending on setup type and service class
Admission Control The Downlink Channelization Code Admission Policy Code blocking for non-handover requests is performed to reserve codes for users in handover. Non-guaranteed admission requests are blocked when DL Code Usage > dlCodeAdm beMarginDlCode Guaranteed admission requests are blocked when DL Code Usage > dlCodeAdm
When a request is blocked on the downlink channelization code admission, the soft congestion mechanism is triggered.
Admission Control Trial: Downlink Code Admission Settings: beMarginDlCode=0 DlCodeAdmin=variable
Results: DlCodeAdm (%) No. 1 2 2 3
beMarginDlCode (%) Result 0 RRC Connection Setup Rejected 0 RRC Connection Setup Rejected
3
4
0
Voice call admitted, PS call rejected
4
35
0
5
37
0
6 7
39 40
0 0
Voice call admitted, PS call rejected SRB admitted, PDP context activation rejected. SRB admitted, PDP context activation rejected. PS Call admitted up to 384 Kbps
Admission Control The Histogram Admission Policy Controls the SF usage in DL and UL at cell level, the number of radio links in compressed mode and the number of simultaneous HS-serving links in a cell. Non-guaranteed Service Class in DL Requests demanding SF8 are blocked when usage of SF8 > sf8Adm Requests demanding SF16 are blocked when usage of SF16 > sf16Adm Requests demanding SF32 are blocked when usage of SF32 > sf32Adm
Admission Control The Histogram Admission Policy (cont) Guaranteed Service Class in DL Requests demanding SF16 in DL (streaming PS16/128 radio connection type) are blocked when usage of SF16 > sf16gAdm
By setting this parameter, the access for high and low consuming guaranteed services can be differentiated. Guaranteed-hs Service Class in UL Requests demanding SF4 in UL (PS384/HS radio connection type) are blocked when usage of SF4 > sf4AdmUl
In cells where the optional PS384/HS radio connection is activated, this parameter may be reduced if the uplink experiences problems.
Admission Control The Histogram Admission Policy (cont) Compressed Mode Radio Links Limits Requests demanding a radio link in compressed mode are blocked when Current number of radio links > compModeAdm
The presence of connections using SF/2 compressed mode may degrade the quality of the common channels. That may be avoided by adjusting compModeAdm .
Number of Simultaneous HS-Serving Links Limits The number of users allocated to the HS-DSCH may be limited to ensure sufficient end-to-end quality. Admission request will be blocked when number of users assigned to the HS-DSCH > hsdpaUsersAdm
Admission Control Trial: Histogram Admission Settings: sf32Adm= 32 sf16Adm= 16 , 8 sf8Adm= 8 , 0
Results:
No. sf32Adm
s16Adm
sf8Adm Max Throughput (Kbps)
1
32
16
8
384
2
32
16
0
128
3
32
0
0
64
Admission Control The Downlink Transmitted Carrier Power Admission Policy This admission policy controls the downlink power utilized by R99 connections. Non-Guaranteed, Non-Handover requests are blocked when DTCP > pwrAdm - beMarginDlpwr Guaranteed, Non-Handover & Non-Guaranteed Handover requests are blocked when DTCP > pwrAdm Guaranteed, Handover & Guaranteed-hs requests are blocked when DTCP > pwrAdm + pwrAdmOffset
When a request is blocked on the DL Transmitted Carrier Power policy, the soft congestion mechanism is triggered.
Admission Control Trial: Downlink Transmitted Carried Power Admission Settings: beMarginDlPower=0 pwrAdmOffset=0 pwrAdm=variable maxpwerMax=15
Results: pwrAdm (%)
beMarginDlPwr (%)
1
13
0
0
4.8
RRC Connection Setup Rejected
2
16
0
0
4.8
RRC Connection Setup Rejected
4.8 4.8 15
Signalling Radio Bearer admitted, but PDP context activation blocked PS call admitted up to 64Kbps PS call admitted up to 384Kbps
No.
3 4 5
17 18 18
0 0 0
pwrAdmOffset maxPwrMax (%) (dB)
0 0 0
Result
Admission Control The ASE Admission Policy Provides information of air interface usage per radio link type in cell for DL and UL. The UL ASE Admission Policy Non-Guaranteed, Non-Handover requests are blocked when ASE UL Usage > aseUlAdm - beMarginAseUl Guaranteed, Non-Handover & Non-Guaranteed, Handover requests are blocked when ASE UL Usage > aseUlAdm Guaranteed, Handover & Guaranteed-hs requests are blocked when ASE UL Usage > aseUlAdm + aseUlAdmOffset
ASE is the only resource for admission control on the UL
Admission Control The DL ASE Admission Policy Non-Guaranteed, Non-Handover requests are blocked when ASE DL Usage > aseDlAdm - beMarginAseDl Non-Guaranteed, Handover & Guranteed & Guaranteed-hs requests are blocked when ASE DL Usage > aseDlAdm
Admission Control Trial: ASE Admission Settings: dlCodeAdm=100 beMarginDlCode=0 beMarginAseUl=0 aseUlAdm=500 beMarginDlPwr=0
Results: No
1 2 3 4 5 6
aseDlAdm 1 2 3 9 19 41
Result
CS Voice rejected, PS Rejected CS Voice rejected, PS Rejected CS Voice admitted, PS Rejected PS call admitted up to 64Kbps PS call admitted up to 128Kbps PS call admitted up to 384Kbps
Admission Control The RBS Hardware Admission Policy Provides information of hardware usage in a local cell group for DL and UL The UL RBS Hardware Admission Policy Non-Guaranteed, Non-Handover requests are blocked when UL HW Usage > ulHwAdm - beMarginUlHw Guaranteed, Non-Handover & Non-Guaranteed, Handover & Guaranteed-hs, Non-Handover requests are blocked when UL HW Usage > ulHwAdm Guaranteed, Handover & Guaranteed-hs,Handover requests are blocked when UL HW usage arrives at 100%
Admission Control The DL RBS Hardware Admission Policy Non-Guaranteed, Non-Handover requests are blocked when DL Hardware Usage > dlHwAdm - beMarginDlHw Guaranteed, Non-Handover & Non-Guaranteed, Handover & Guaranteed-hs, Non-Handover requests are blocked when DL Hardware Usage > dlHwAdm Guaranteed, Handover & Guaranteed-hs,Handover requests are blocked when DL HW usage arrives at 100%
When a request is blocked on the DL RBS Admission, the soft congestion mechanism is triggered.
Admission Control Soft Congestion Mechanism The Soft Congestion Mechanism is triggered when a request for admission is blocked.
This mechanism consists of down-switching an non-guaranteed connection to a lower rate after ₋ a guaranteed admission control is blocked ₋ a guaranteed-hs admission control is blocked ₋ a non-guaranteed admission control of a lower rate is blocked
The Soft Congestion mechanism targets connections originating over the Iu interface (present product not able to down-switch connections originating over the Iur interface)
Admission Control Soft Congestion Mechanism (cont) Soft congestion triggered by non-guaranteed request blocking The rate of an existing connection is reduced depending on the requested downlink rate: ₋ request for 384 kbps blocked → not affect existing connections in cell ₋ request for 128 kbps blocked → reduce exiting 384 kbps to 128 kbps ₋ request for 64 kbps blocked reduce 384 kbps to 128 kbps or (if not 384 kbps connections available) reduce 128 kbps to 64 kpbs
Soft Congestion triggered by guaranteed request blocking The non-guaranteed connections are targeted in decreasing order of their downlink rate (first 384 kbps connections are reduced, then 128 kbps connections are targeted, …)
Congestion Control Congestion Control Detection Congestion is detected in the RNC by means of measurements of the Downlink Transmitted Carrier Power and the Uplink Received Total Wideband Power.
The Downlink Transmitted Carrier Power is continuously measured. When the power goes above a predefined threshold, an event –based measurement is sent to the RNC. As long as the power is above the threshold, an event – based report is sent to the RNC every second.
Congestion Control DL Cell Congestion Detection
DL congestion is solved when the DTCP is below the setup threshold for longer that the hysteresis time or until next periodic event-based measurement indicating DTCP below threshold arrives.
Congestion Control UL Cell Congestion Detection
UL congestion is solved when the Uplink RTWP is below the setup threshold for longer that the hysteresis time or until next periodic event-based measurement indicating URTWP below threshold arrives.
Congestion Control Congestion Resolve Handling
Congestion Control Congestion resolve actions in mixed services congested cell: Non-guaranteed connections are targeted immediately: their rate is decreased
If congestion persists and there are no more Non-guaranteed connections, the resolve actions start for Guaranteed-hs connections. They will be dropped.
The guaranteed services are the last ones to be targeted by Congestion control. The resolve actions on Guaranteed services are more severe, causing the drop of the connections.
