Module8 HSDPA Scenario

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All Rights Reserved Alcatel-Lucent 2007Alcatel-Lucent W-CDMA UMTS Radio Principles

Module 8HSDPA Scenarios

3JK10665AAAAWBZZA Edition 1

Section 4HSDPA Description



All Rights Reserved Alcatel-Lucent 2007Alcatel-Lucent W-CDMAUMTS Radio Principles

HSDPA Description HSDPA Scenarios 4 8 2

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First editionLast name, first nameYYYY-MM-DD01

RemarksAuthorDateEdition

Document History





Objectives

After this section, you will be able toz Describe main procedures associated with

HSDPA call establishment and mobility.





Objectives [cont.]






Table of Contents

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1 Call Setup 71.1 Call Establishment 8

Channel Type Selection 91.2 Initial Connection Establishment 101.3 RAB Assignment Phase 11

2 Mobility 122.1 Intra-Frequency Mobility 13

HS-DSCH Primary Cell Change 142.3 Inter-frequency HSDPA HHO with Measurements 15

3 Iub Flow Control 163.1 Flow Control Principles 173.2 HS-DSCH Capacity Allocation 18

Summary 19Self-Assessment on the Objectives 20End of Module 21





Table of Contents [cont.]

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1 Call Setup





1 Call Setup

1.1 Call Establishment

How is HSDPA triggered by the network?

CoreNetwork

1. Request for service(e.g. Web Browsing)

UE

Node B

RNC

2. RAB AssignmentRequest4. HS-DSCH

Establishment

3. DCH ? HS-DSCH ?Channel Type Selection





1.1 Call Establishment

Channel Type Selection

RAB assignment request from CN

HS-DSCH or DCH ?

HS-DSCHselection

RAB Traffic Class

Traffic Class =

Interactive/Background

UE Capabilities

Cell Capability

HSDPA UE?

Primary Cell = HSDPA Cell?

Service = PS?

With the introduction of HSDPA in the UTRAN, a new type of transport channel can be allocated to serve the RAB requested from the CN. Thus, the channel type selection algorithm allows selecting either DCH or HS-DSCH depending on the RAB characteristics received from the CN.

At reception of a RAB assignment Request, the SRNC selects the transport channel type between DCH and HS-DSCH according to the following constraints:

z RAB traffic class} Only PS RABs with traffic class interactive and background are transported on HS-DSCH

z UE capability to support HS-DSCH} HS-DSCH can be selected only if UE supports it, as indicated by the UE capability Support of HS-PDSCH,

and if UE supports the combination of already established DL DCH and HS-DSCH, as indicated by the UE capability DL capabilities with simultaneous HS-DSCH configuration

z Cell capability to support HS-DSCH} HS-DSCH can be selected only if one cell of the active set supports HSDPA or if one collocated cell (on

another carrier) supports HSDPA.

Channel type selection is performed prior to radio admission control. Then depending on the channel type selection, either DCH RAC or HSDPA RAC is triggered.




HSDPA Description HSDPA Scenarios 4 8 10NodeBUE RNC SGSN

1 Call Setup

1.2 Initial Connection Establishment

RRC / RACH / RRC Connection Request

Establishment CauseAS Indicator

NBAP / RL Setup Request

NBAP / RL Setup Response

RRC / RACH / RRC Connection Setup Complete

RRC / FACH / RRC Connection Setup

SRB Definition (DCCH)U-RNTITarget RRC State (Cell_DCH)

HSDPA CapabilityUE Category

RRC / DCCH / Initial Direct Transfer (Service Request)

RANAP / Service Request

RRC / DCCH / Measurement Control

Most of the steps of this first phase are common to all type of calls. There are few elements specific to HSDPA.

RRC Connection Request embeds the Establishment Cause and the AS Indicator that may be used for Traffic Segmentation.

RRC Connection Setup states the properties of the SRB to be used and includes a first Adio NEtwork Temporary Identifyer.

RRC connection Setup Complete indicates to RNC UE capabilities.





1 Call Setup

1.3 RAB Assignment PhaseNodeBUE RNC SGSN

NBAP / RL Reconfiguration Prepare

NBAP / RL Reconfiguration Ready

Measurement Power OffsetScheduler & HARQ propertiesMAC-d PDU sizeHS-DPCCH properties

RRC / DCCH / Radio Bearer Setup

RANAP / RAB Assignment Request

RRC / DCCH / Radio Bearer Setup Complete

HS-SCCH CodesNumber of HARQ

NBAP / RL Reconfiguration Commit

RANAP / RAB Assignment Response

HS-SCCH CodesHARQ number and propertiesH-RNTIMeasurement Power OffsetHS-DPCCH properties

In this second phase only the NBAP Radio Link Reconfiguration procedure and RRC Radio Bearer Reconfiguration are modified because of HSDPA.





2 Mobility





2 Mobility

2.1 Intra-Frequency Mobility

R4 cell HSDPA cell HSDPA cell HSDPA cell

DCHFallback

HS-DSCHTransition

HS-DSCHMobility

Core Network

RNC

HS-DSCHMobility

RNC

NodeB NodeB

Primary Cell

DCH only

HS-DSCH+DCH

HS-DSCHMobility

HS-DSCHMobility

Primary cell change

As defined by 3GPP HS-DSCH is established in only one cell so is never in soft handover. In Alcatel-Lucent implementation HS-DSCH is established in the primary cell because it is the best candidate (good radio conditions and not changing too often).

Each time the primary cell changes the HS-DSCH RL is deleted on the former primary right after the RRC Measurement Control procedure has been performed, and it is re-established under the new primary, using a synchronous reconfiguration.

If the new primary cell does not support HSDPA then the RB is reconfigured to DCH (iRM CAC is performed). If the new primary cell supports HSDPA while the former did not, and given that the UE supports HSDPA, then the RB is reconfigured to HS-DSCH (HSDPA CAC is performed).





Activation CFN

2.1 Intra-Frequency Mobility

HS-DSCH Primary Cell Change

RNC source Node B

target Node B

UE

RB Reconfiguration (Activation CFN)

RL Reconfiguration Ready

Measurement Control (new neighbouring list)

RL Reconfiguration Prepare

RB Reconfiguration Complete

Primary cell change

RL Reconfiguration Ready

RL Reconfiguration Prepare

RL Reconfiguration Commit (Activation CFN)

RL Reconfiguration Commit (Activation CFN)

As defined by 3GPP HS-DSCH is established in only one cell so is never in soft handover. In Alcatel-Lucent implementation HS-DSCH is established in the primary cell because it is the best candidate (good radio conditions and not changing too often).

Each time the primary cell changes, the HS-DSCH RL is deleted on the former primary and it is reestablishedunder the new primary, using a synchronous reconfiguration. During the reconfiguration data transfer on HS-DSCH is suspended by the RNC.

If it is not possible to re-establish HS-DSCH on the new primary (CAC failure) then the radio bearer may fall back to DCH.

If the new primary cell does not support HSDPA then the RB is reconfigured to DCH (iRM CAC is performed). In case of CAC failure for the DCH then the PS RAB is released.

If the new primary cell supports HSDPA while the former did not and given the UE supports HSDPA, then the RB is reconfigured to HS-DSCH. In case of CAC failure the radio bearer stays on DCH.

In the case the current primary cell is not present in the new active set, the HS-DSCH link is deleted right after the Active Set procedure (and before the Measurement Control procedure) and the UE releases the HSDPA link. A new HS-DSCH link is then setup using a normal SRLR procedure on the new primary cell after the Measurement Control.





2 Mobility

2.3 Inter-frequency HSDPA HHO with Measurements

R99 cellFrequency 1

HSDPA cell Frequency 2

Core Network

SRNC

The HSDPA Inter-freq mobility (HHO) with measurements (i.e. Compressed Mode on associated DCH) is

supported with UA05.

The feature values are to Enable HSDPA call handover to another cell based on criteria thresholds, avoiding

drop calls and to allow HSDPA mobiles entering an HSDPA cell through an alarm handover to benefit from

HSDPA service.

UE solution supporting the Compressed Mode on DCH once in HSDPA operation (i.e. HS-PDSCH(s) usage).





3 Iub Flow Control





3 Iub Flow Control

3.1 Flow Control Principles

IubCapacity Request

Control FPCapacity Allocation

Control FPData FP

RNC

RNC Buffers

NodeB Buffers

QId0 QId1 QIdNQId2 QId0 QId1 QIdNQId2

With HSDPA, the effective throughput per UE is not deterministic and quite variable. A flow control mechanism has been introduced between the RNC Mac-d and the NodeB MAC-hs entities in order to fill the NodeB buffers with sufficient data to provide to the UEs and be quite reactive to throughput variations.

This flow control mechanism is based on three main procedures:

z the Capacity Request procedure that provides means for the RNC to indicate for each session of each UE its buffer occupancy (at MAC-d level).

z the Capacity Allocation procedure generated by the NodeB to indicate to the RNC how many PDUs are required for the desired session and the interval in which data should be sent. This is based on the estimated throughput for this session and the amount of unsent data in NodeB transmission buffers.

z the HS-DSCH data transfer procedure in which the RNC sends the MAC-d PDUs grouped in FP frames (1 to 255 PDUs per FP frame). The updated buffer occupancy is also given. The RNC may choose to send all the required MAC-d PDUs in a single FP frame, or to space out (within the notified interval) the transmission in several FPs.





3.1 Flow Control Principles

3.2 HS-DSCH Capacity Allocation

ServingRNC

NB.: The UE is in cell_DCH state

UE Node B

HS-DSCH FP

MAC-hsMAC-hs

HS-DSCH FP

HS-DSCH FPHS-DSCH FP

9. Data Transfer

11. Data Transfer

10. HS-SCCH

Priority Indicator, UE buffer Size

8. HS-DSCH Capacity Allocation

HS-DSCH credits, inter-TTI interval,

7. HS-DSCH Capacity Request

After HS-DSCH Configuration

As soon as the SRNC detects the necessity to send HS-DL data on one HS-DSCH, it sends an HS-DSCH Capacity Request control frame within the HS-DSCH Frame Protocol to the CRNC. Parameters: Common Transport Channel Priority Indicator and User Buffer Size. The CRNC forwards this message (HS-DSCH Capacity Request control frame) to the Node B. So in this example sequence, the CRNC does not interfere with the HS-DSCH scheduling.Parameters: Common Transport Channel Priority Indicator and User Buffer Size.

The Node B determines the amount of data (credits) that can be transmitted on the HS-DSCH and reports this information back to the DRNC in a HS-DSCH Capacity Allocation control frame in the HS-DSCH Frame Protocol.Parameters: Common Transport Channel Priority Indicator, HS-DSCH Credits, HS-DSCH Interval, HS-DSCH Repetition period, Maximum MAC-d PDU length.The DRNC sends the HS-DSCH Capacity Allocation control frame to SRNC. So again, the DRNC does not react itself to that message in this example.Parameters: Common Transport Channel Priority Indicator, HS-DSCH Credits, HS-DSCH Interval, HS-DSCH Repetition period, Maximum MAC-d PDU length.

The SRNC starts sending DL data to the Node B. This is done via the two HS-DSCH Frame Protocol "hops" on Iurand Iub interface. The Node B schedules the DL transmission of DL data on HS-DSCH which includes allocation of PDSCH resources.

The Node B transmits the control information for the concerned UE using the HS-SCCH.

The Node B sends the HS-DSCH data to the UE on the HS-PDSCH(s).





Summary





Self-Assessment on the Objectives

z Please be reminded to fill in the formSelf-Assessment on the Objectivesfor this module

z The form can be found in the first partof this course documentation





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