HSDPA Mobility discussion session

8/8/2019 HSDPA Mobility discussion session

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28.Aug 2006

www.huawei.com

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Mobility in HSDPAMobility in HSDPA

Discussion sessionDiscussion session


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28.Aug 2006

www.huawei.com

Mobility in HSDPAMobility in HSDPA

Discussion sessionDiscussion session


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Upon completion of this presentation, you will learn moreabout:

Some Important concepts in HSDPA.

Mobility Management in HSDPA.


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Presentation planPresentation plan

Overview.

Some important HSDPA concepts:

Three new channels were introduced.

High speed channels advantages.

Retransmission in HSDPA.

Fast time Scheduling in HSDPA.

HSDPA Basic Signaling Flow.

MobilityManagement:

Measurement event for best serving HS-DSCH cell.

Handover Procedures of PS Calls using HSDPA.

Intra-Node B HS-DSCH to HS-DSCH Handover. Inter-Node B HS-DSCH to HS-DSCH Handover.

HS-DSCH to DCH Handover.

DCH to HS-DSCH Handover.

Practical exercises from HSDPA Drive test Analysis.

End.


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Mobility in HSDPAMobility in HSDPAMobility in HSDPAMobility in HSDPA

Important HSDPA concepts.Important HSDPA concepts.

Mobility Management.


These important points will help you to understand theHSDPA operation quickly:


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Threenew channelswere introduced

To implement the HSDPA feature, three new channels are introduced in the

physical layer specifications:

High-Speed Physical Downlink Shared Channel (HS-DSCH) carries

the user data in the downlink direction.

High-Speed Shared Control Channel (HS-SCCH) carries the necessary

physical layer control information to enable decoding of the data on HS-

DSCH.

Uplink High-Speed Dedicated Physical Control Channel (HS-

DPCCH) carries the necessary control information in the uplink.


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Highspeed channels advantagesHighspeed channels advantages

high-speed Physical Downlink Shared Channel (HS-DSCH) :

This new channel has specific characteristics in many ways compared with existing

channels in Release 99:

Shorter TTI, Transmission Time Interval, which has been defined to be 2 ms toachieve a shorter round trip delay for the operation between the terminal and Node-B

for retransmissions, and its shorter compared to the 10, 20, 40 or 80 ms TTI sizeswhich supported in Release 99.

Adding a higher order modulation scheme, 16 QAM.

Multicode transmission : 5, 10, or 15 codes, depending on the terminal (UE)capability.


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High-speed shared control channel HS-SCCH:By listening to these control channels, the UEs will receive information during

the call and know which data packets, which have been sent on an HS-PDSCH, belong to which mobile.

Highspeed channels advantagesHighspeed channels advantages


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RetransmissioninHSDPARetransmissioninHSDPA

Retransmission from NodeB instead of

RNC:

Retransmission from NodeB instead of

RNC: In Release 99 there is no difference in physical layer operation, regardless of whether the

packet is a retransmission or a new packet.

With HSDPA the packet is first received in the buffer

in the NodeB, then the NodeB keeps the packet in the

buffer even if has sent it to the user and, in case of

packet decoding failure, retransmission automatically

takes places from the base station without RNCinvolvement.

Also HSDPA is using new retransmission technique

HARQHARQ Hybrid ARQ, by which the receiver store

the erroneous block, if its detected, without discarding

it, and request the NodeB for retransmission, then it

combines the received re-transmission with previously

received transmission


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Fast timeSchedulinginHSDPAFast timeSchedulinginHSDPA

Fast time Scheduling:Fast time Scheduling:

Scheduling determines which user shall be transmitted, between the usersdepending on the users needs and the link CQI.

Scheduler may be based on:

Channel condition (CQI)*.

Amount of data waiting in the queue (delay).

Fairness between users to make all of themsatisfied as possible as can.

Cell throughput.

* The CQI is the channel quality indicator,

which represents the uplink feedback information,and its carried on the HS-DPCCH.


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HSDPA Basic SignalingFlowHSDPA Basic SignalingFlow

Node B

RNCUE

5) ACK/NACK on HS-DPCCH

6)Data packet+retransmit(if need)On HS-DSCH

Data Packet

2) Schedule and determineHS-DSCH parameter

3) Send HS-DSCH Parameter on

HS-SCCH and Data on HS-PDSCH

4) Check HS-DSCH parameter, If Ok,Receive, Store data and demodulate

1) CQI on HS-DPCCH


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Important HSDPA concepts.

Mobility Management.Mobility Management.




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MobilityManagementMobilityManagement

HSDPA does not use soft handover, since HS-DSCH and HS-SCCHtransmission take place only from a single cell, called the serving HS-DSCH

cell.

The RNC determines the serving HS-DSCH cell for the active HSDPA UE,

and this serving HS-DSCH cell is one of the cells which in the UEs active set.

The serving HS-DSCH cell may be changed without updating the usersactive set.

An HS-DSCH serving cell change is typically based on measurement reportsfrom the UE.

3GPP Release 5 includes a new measurement procedure, using the 1D event

to inform the RNC of the best serving HS-DSCH cell. Serving HS-DSCH cell change can be through intra-Node B or Inter-Node B

HS-DSCH to HS-DSCH handover.

Inter-frequency handovers with compressed mode measurements are alsosupported for HSDPA users.


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Measurement event for best serving HSMeasurement event for best serving HS--DSCH cellDSCH cellMeasurement event for best serving HSMeasurement event for best serving HS--DSCH cellDSCH cell

The serving RNC makes the handover decisions directly based on the measurementwhich reported by the UE.

A measurement event 1d* has been defined, which is called the measurement event forbest serving HS-DSCH cell.

This measurement reports the CPICH Ec=N0 of the best cell.

Usage of a hysteresis margin to avoid fast change in the serving HS-DSCH cell ispossible for this measurement event.

As well as specification of a cell-individual offset (CIO) to favor certain cells, forinstance, to extend their HSDPA coverage area.

Note:

* Actually 1d event is already defined in R99: (Event 1d, Change of Best Cell)

When any (Active Set,Monitored set, and Detected) cell becomes stronger than

the best cell+hysteresis1d /2 in the Active Set, during a time at least equal totimeToTrigger1d ,event 1d occurs.


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1d event for best serving HSevent for best serving HS--DSCH cellDSCH cell1d event for best serving HSevent for best serving HS--DSCH cellDSCH cell


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Handover Procedures of PS Calls using HSDPAHandover Procedures of PS Calls using HSDPAHandover Procedures of PS Calls using HSDPAHandover Procedures of PS Calls using HSDPA

Intra-Node B HS-DSCH to HS-DSCH Handover.

Inter-Node B HS-DSCH to HS-DSCH Handover.

HS-DSCH to DCH Handover.

DCH to HS-DSCH Handover.


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IntraIntra--Node B HSNode B HS--DSCH to HSDSCH to HS--DSCH HandoverDSCH HandoverIntraIntra--Node B HSNode B HS--DSCH to HSDSCH to HS--DSCH HandoverDSCH Handover

Once the serving RNC decides to make an intra-Node B handover from a sourceHS-DSCH cell to a new target HS-DSCH cell under the same Node B, the servingRNC sends a synchronized Radio link reconfigurationRadio link reconfigurationprepare message to theNodeNodeBB, as well as a radio resource control (RRCRRC) physical channel reconfigurationreconfigurationmessagemessage to the useruser.

At a specified time index where the handover from the source cell to the new targetcell is carried out the source cell stops transmittingsource cell stops transmitting to the user, and theMAC-hspacket scheduler in the target celltarget cell is thereafter allowed to control transmission totransmission tothe userthe user.

Similarly, the terminal starts to listen to

the HS-SCCH from the new target cell,

the new serving HS-DSCH cell.

All the PDUs for the user are moved

from theMAC-hs in the old source cell

to theMAC-hs in the target cell during

the HS-DSCH handover..


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InterInter--Node B HSNode B HS--DSCH to HSDSCH to HS--DSCH HandoverDSCH HandoverInterInter--Node B HSNode B HS--DSCH to HSDSCH to HS--DSCH HandoverDSCH Handover

Here, the new target cell is under another Node B, and potentially might be under

another RNC.

Once the serving RNC decides to initiate such a handover, a synchronized RadioRadio

link reconfiguration prepare messagelink reconfiguration prepare message is sent to the drifting RNCRNC and theNode BNode B

that controls this target cell, as well as a radio resource control (RRCRRC) physical

channel reconfiguration messagereconfiguration message to the useruser.

At the time, the cell change is implemented,

theMAC-hs for the user in the old sourceold source

cell is resetcell is reset, which basically means that all

buffered PDUs for the user are deleted,

including the pending PDUs in the hybrid

ARQ manager.

At the same time index, the flow control

unit in theMAC-hs in the target cell starts

to request PDUs from theMAC-d in the

serving RNC, so that it can start to transmit

data on the HS-DSCH to the user.


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HSHS--DSCH to DCH Handover.DSCH to DCH Handover.HSHS--DSCH to DCH Handover.DSCH to DCH Handover.

Handover from an HS-DSCH to DCH may potentially be needed for

HSDPA users that are moving from a cell with HSDPA to a cell without

HSDPA (Release 99).

Once the serving RNC decides to initiate such a handover, a synchronised

radio link reconfiguration prepare message is sent to the involved Node Bs,as well as a radio resource control (RRC) physical channel reconfiguration

message to the user.

In a similar way to the inter-Node B HS-DSCH to HS-DSCH handover, the

HS-DSCH to DCH handover results in a reset of the PDUs inMAC-hs in

the source cell, which subsequently requires recovery via higher layerretransmissions such as, for instance, RLC retransmissions.


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DCH to HSDCH to HS--DSCH Handover.DSCH Handover.DCH to HSDCH to HS--DSCH Handover.DSCH Handover.

This handover type may, for instance, be used if a user is moving from a

non-HSDPA-capable cell into an HSDPA-capable cell, or to optimize the

load balance between HSDPA and DCH use in a cell.


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Important HSDPA concepts.

Mobility Management.

Practical exercises from HSDPA Drive test Analysis.Practical exercises from HSDPA Drive test Analysis.



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How to know the contentof the testfile Isrelated

toHSDPAservice test?!!



To know that you should check the Radio Bearer setup messageRadio Bearer setup message Open one message from

the list Go to the end of this message to see the SF which was used in this RadioBearer setup:

1.1. SF =SF = 1616 this test file relating to HSDPAHSDPA test.

2. SF = 128 this test file relating to Voice test.

3. SF = 32 this test file relating to either VP or PS service.


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Also from the content of Radio Bearer setup message, you can find moreinformation which related to HSDPA channels HS-DSCH & HS-SCCH..






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Intra-NodeB Best Cell Change (1d Event)Intra-NodeB Best Cell Change (1d Event)

The new target HS-DSCH cell under the same Node B..


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Radio channelreconfigurationRadio channelreconfiguration

The serving RNC sends a radio resource control (RRCRRC) physical channelreconfiguration messagereconfiguration message to the useruser.


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TheChangeof Best Cell was done..TheChangeof Best Cell was done..


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Inter-NodeB Best Cell ChangeInter-NodeB Best Cell Change

If the new target cell is not one of the Active set members, 1a1a event will besent by UE, then an Active set updateActive set update will take place..


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Inter-NodeB Best Cell ChangeInter-NodeB Best Cell Change

Updating the active set, by connecting with cell PSC=330.


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Best cell change 1deventBest cell change 1devent


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Radio channelreconfigurationRadio channelreconfiguration


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HS-DSCH toDCHHandoverHS-DSCH toDCHHandover


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HS-DSCH toDCHHandoverHS-DSCH toDCHHandover

The same procedure will be for the HS-DSCH to DCH Handover, but in

this case UE needs to make Radio Bearer reconfiguration, since the Bearer

type is different between HS-DSCH to DCH channels..


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HSDPA Mobility discussion session

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