wcdma aclcpc 001

8/13/2019 Wcdma Aclcpc 001

1/10

1 NOKIA WCDMA_ACLCPS.PPT/21.3.2002 Kari Heiska, TLI361-WCDMA radioverkkosuunnittelu - luentosarja Jyvaskyln yliopistossa(Reproduced by permission of John Wiley & Sons Limited)

RRM

Radio Resource Management (RRM)Radio Resource Management (RRM)Admission Control (AC), Load Control (LC) & Packet Scheduling (PAdmission Control (AC), Load Control (LC) & Packet Scheduling (PS)S)

Kari Heiska 21.3.2002


ContentsContents

Air Interface Load

Admission Control (AC)

Packet Scheduling (PC)

Load Control (LC) Resource Management (RM)


2/10


Air Interface LoadAir Interface Load The air interface loadhas to be under the planning targets in order to keep the guaranteed

network performance

Different definitions for load:

Wideband power based uplink load:

Uplink load factor:

Uplink noise rise:

Throughput-based uplink loading:

Wideband power-based DL loading:

Nothown PIIPrxTotal ++=

PrxTotal

II othownUL

+=

ULNP

PrxTotalNR

==

1

1

( )

+

+=

k

kk

kUL

R

W

i

1

1

Ptxmax

PtxTotalUL =


Air Interface LoadAir Interface Load

Wideband power-based DL loading:

Throughput-based downlink loading:

Downlink loading can be also defined as:

Ptxmax

PtxTotalUL =

Rmax

RN

k

k

UL

=

= 1

=

+=

k

i

iDLiiii

DL iW

R

1

, )1(


3/10


Admission ControlAdmission Control

The Admission Control (AC) decides whether a new RAB is admittedor a current RAB can bemodified

AC derives from the bearer parameters the transmission bit rate, the processing gain, as well asthe radio link quality requirements (BER, BLER, SIR target)

AC determines the L1 transmission parameters for the RAB to be used during the call: thetransport format (TF) or the set of transport formats (TFS) of the transport channel (in multibearercase AC determines the L1 parameters for TrCH multiplexing)

For RT traffic (conversational and streaming) the AC decides whether a mobile station is allowedto enter the network. The AC algorithm estimates the load increase caused by RAB establishmentor RAB modification. If the RAB would cause too high interference access is denied.

For NRT traffic (interactive and background) the optimum scheduling of packets (time and bit-rate) must be determined after the RAB has been admitted. This will be done in close co-operationof AC and PS

UL and DL load will be determined separately. Both UL and DL admission criterias have to befulfilled before RAB admission/modification

The load estimation will be performed for all cells which belongto the active set. Therefore the ACalgorithms are located in the Radio Network Controller (RNC)

For the admission/modification decisions the AC uses thresholds produced by RNP


Admission Control (WB power based, UL)Admission Control (WB power based, UL)

In the uplink the RT RAB will be admitted to the network if1) for the non-controllable loadPrxNC:

where the non-controllable load means the RT load or close-to RT load +other cell load +noise

and

2) for the total wideband interference:

Prxtarget is a threshold andPrxOffset is an offset parameter both set by the RNP. Condition 1 is forthe RT users only and condition 2 is both for RT and NRT users.

Iis the increase of wideband interference power caused by the new RAB.Ican be estimated asfollows:

,PrxTargetIPrxNC +

PrxOffsetPrxTargetPrxTotal +

Max plannednoise rise

Interferencelevel

load h

I threshold

I total_old

Estimatedincrease of

interference I

L

LPrxTotal

I

1

R

WL

+

=

1

1


4/10


Admission Control (WB power based, UL)Admission Control (WB power based, UL)

In the downlink the RT RAB will be admitted to the network if1) for the non-controllable loadPrxNC:

where the non-controllable load means the RT load

2) for the total wideband interference:

Ptxtargetis a threshold and PtxOffsetis an offset parameter both set by the RNP. Condition 1 is forthe RT users only and condition 2 is both for RT and NRT users

P is the increase of wideband interference power caused by the new RAB.Ican be estimated asfollows:

,PrxTargetPPrxNC +

PtxOffsetPtxTargetPtxTotal +

Max planned DLnoise rise

Ptx power

load h

Pthreshold

Ptotal_old

Estimatedincrease of

Ptx power I

L

L

PrxTotal

I 1

R

WL

+

=

1

1


Admission Control (throughput based, UL)Admission Control (throughput based, UL)

In the throughput based Admission control a new RAB is admitted only if the total load afteradmittance stays below the thresholds:

In uplink:

In downlink:

whereoldUL

andoldDL

are the network load before the bearer request andL is the load increase.

Comparison between Wideband based and throughput based AC:

LthresholdUoldUL L +

LthresholdDoldDL L +

WB power

load

WB power based AC: constantcoverage, variable throughput

i=0.3

i=0.5

Throughput based AC: constantthroughput but variable coverage


5/10


Packet SchedulingPacket Scheduling In UMTS Quality of Service Concept RAB services are divided into four class:

Conversational class circuit or packet switched core network

very delay sensitive real-timeapplications: voice over IP, video

Streaming class circuit or packet switched core network

services: streaming video, music

Interactive class non real-time services with packet core network

services: web-browsing

Background class delay insensitive

services: e-mail, advertisements

no guaranteed bit-rate

Packet data traffic consists of packet sessions which consists of one or several packet calls During one packet call several packets will be generated which causes bursty nature of the packet data traffic. Also the

interference is bursty.

Packet scheduling takes care of allocating the radio resources (time and power) for the packets of interactive and backgroundtype of traffic


Packet SchedulingPacket Scheduling

TCP ACK

Call duration = Query response time

1/= mean SDU inter-arrival time

SDU(or IPpacket)

( TCP) Session duration

Call setup delay(queue time)

User A places arequest to server

Primary PDP contextUser A CN

User Aconnect to IP

User A places nextrequest Outgoing channel :

UMTS UL

Return Channel :UMTS DL

User A

Server

When user A places next calldepends on the completion of current call

Reading periodTransfer time

Packet call (web browsing)


6/10


Packet SchedulingPacket Scheduling Functions of the packet scheduler

determines the available radio interface resources for the NRT servicessharing of radio interface resources between NRT servicesto monitor the allocations for NRT servicesswitching between transport channels: common (FACH,RACH), dedicated (DCH), shared

(DSCH)

monitoring of system loading load control for the NRT RABs

Work sharing between AC and PS:

time

BitrateNRTRAB allocated / packet service session

RACH/FACH,DCH/DSCHallocation /packet call

AC handles

PS handles


Packet SchedulingPacket Scheduling

PS allocates capacity for both uplink and downlink separately due to asymmetric traffic When reserving capacity for one direction the PS has to reserve low data rate channel for the

other direction as well carrying higher layer acknowledgements (TCP), data link layeracknowledgements, data link layer control and the power control (=return channel)

RT load can not be controlled efficiently. Thus RT load +other cell interference +backgroundnoise is called non-controllable load

The maximum load (Prxtarget/Ptxtarget) subtr. by the non-controllable load can be allocated forNRT traffic which is called controllable load

Power

time

non-controllable load

controllableload

PrxNc / PtxNc

PrxTotal / PtxTotal

PrxNrt / PtxNrt

PrxTarget / PtxTarget

PrxOffset / PtxOffsetPrxTotalandPtxTotalare values measuredby base station, whichare planned to bebelow the targetvalues

The controllablepower (load targetsubtracted by thenon-controllablepower) isusedforNRTusers on besteffort basis by thepacket scheduler

PrxTarget / PtxTargetare set by radio network planning (RNP) so that those will be the optimal operatingpoints of the systemload and the current used systemradio resource. Instantaneously these targets can beexceeded due to changes of interference and propagation conditions


7/10


Packet SchedulingPacket Scheduling Measurements associated to PS

BS performs total received power and total/link specific transmitted power measurements andreports them to RNC over Iub

RNC makes throughput measurementsUE measures uplink transport channel throughput and reports to RNC

The UE selects the uplink NRT transport channel based on RNP parameters (from RNC) and thesystem load

Downlink PS channels are DCH, FACH and DSCH

Dedicatedchannel

Dedicatedchannel Common channels

Common channels Sharedchannel

Sharedchannel

DCHDCH FACHFACH RACHRACH

Uplink / downlink

Uplink / downlink

Both

Both

Downlink

Downlink

Uplink

Uplink

Code usageCode usageAccording tomax.bit rate

According tomax.bit rate

Fixed codesper cell

Fixed codesper cell

Fixed codesper cell

Fixed codesper cell

DSCHDSCH

Downlink

Downlink

Code sharedbetween users

Code sharedbetween users

Power controlPower control Fast closed loopFast closed loop Open loopOpen loop Open loopOpen loop Fast closed loopFast closed loop

Soft handoverSoft handover YesYes NoNo NoNo NoNo

Suited forSuited forMedium/ largedata amounts

Medium/ largedata amounts

Small dataamounts

Small dataamounts

Small dataamounts

Small dataamounts




Packet Scheduling MethodsPacket Scheduling Methods Time division scheduling

Capacity is allocated to one or very few radio bearers at a time. The allocated bit- rate can bevery high and the time needed to transfer the data in the buffer is short

Scheduling time depends on the load of the systemDownlink Shared Channel is typically scheduled with time division+high bit-rates, low Eb/N0, lower delay

- short transmission time, higher variations in interference levels, overhead when setting up

Code division schedulingCapacity has been shared between a large number of radio bearers, allocating low bit-rate

simultaneously for each use

Scheduled bit-rate depends on the load+long transmission time, no variations in interference levels, low setting up overhead

- lower bit-rates (higher delay), higher Eb/N0

In practice the packet scheduler is a combination of these two methods.


8/10


Packet Scheduling Methods (DSCH)Packet Scheduling Methods (DSCH)

BS MS2

MS3

MS1

MS4

DSCH

Associated

DCH's

Bitrate

Power

DSCH

Associated

DCH's

DSCH bitratedepends on location

DCH bitrate

is constant

DSCH power isabout constant

DSCH is time division channel In DSCH link adaptation tries to keep the

DSCH transmission power constant byvarying the bit rate.

Thus, a terminal in the edge of a cellwould be allocated a lower bit ratethan one close to the base station.

Link Adaptation leads toimproved capacityand coverage.


Load ControlLoad Control

LC updates the load status based on measurements and estimationsprovided by AC and PS In the nominal state LC takes care that the network is not overloaded and remains in a stable

state

Close co-operation with AC and PS In overload situations LC takes care of reducing the load quickly and bringing the network back

into nominal state defined by RNP parameters

LC functionalities locate in RNC and in BS Fast LC actions in BTS

Ignores power up TPC commandsDecreases the SIR target used by the fast closed PC

LC actions located in RNCLower bit-rates of RT users (speech service circuit switched data) Interfrequency or intersystem handoverDrop single call in a controlled manner


9/10


Load ControlLoad Control

Measurements used in WB power based RRM Prxtotal in uplink and Ptxtotal in downlink Network planning parameters

Uplink/Downlink PrxTarget/PtxTarget

PrxOffset/PtxOffset

Normal state

Load

Power

Preventive state

Overload state

Packet Scheduler

LoadControl

AdmissionControl

no new RAB

drop RT bearers

overloadactions

preventiveLC actions

no actionsPS schedulespacket trafficnormally

no new capacityrequest scheduled

bit rates not increased

decrease bit ratesNRT bearers to FACH

drop NRT bearers

new RT bearers only ifRT load belowPrxTarget/PtxTarget

AC admits RABs normally

Target + offset

Target

DL:offset = PtxOffset

UL:offset = PrxOffset

DL:target = PtxTarget

UL:target = PrxTarget

In overload situation the PS decreases the bit raterandomly taking into account the bearer class andby the priorities. The bit rate should not decreasedbelow the minimum allowed bit rate (RNP param.)


Resource ManagementResource Management

Target is to allocate physical radio resources when requested Located in RNC and in BS RM reserves a certain proportion of the available physical radio resources according to the request Input data to RM: radio network configuration, allocation parameters Main tasks

Maintains the code tree, Allocates the DL spreading codes, UL scrambling code

Manages the BTS logical resources BTS reports the available logical HW resources in Radio ResourceIndication message

over the Iub interface

RNC HW manager (L1/L2)Transport managerRequests for the other resources


10/10


Interactions of AC and other RRM functionsInteractions of AC and other RRM functionsRAB setup/modify/release request

Admission Control

Load change estimationRAB admission decisionProducing of L2 parametersProducing of TFSDL power allocation

Iu

LoadControl

Producing of loadinformation

Power Control

UL Outer loop

power control

Handover Control

Active state mobility control

ResourceManager

Code allocationTransport resource allocation

Resource information

Active setinformation

RB information

Load information

Target BLER, SIR

Load changeinformation

Load information

Packet Scheduler

Radio resourcescheduling

wcdma aclcpc 001

Documents