hsdpa l2 overview

8/12/2019 HSDPA L2 Overview

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High Speed Downlink Packet Access :Overview on Layer 2


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2

Radio Interface Protocol Architecture [2]

L3

con

trol

con

trol

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trol

Logical

Channels

Transport

Channels

C-plane signalling U-plane information

PHY

L2/MAC

L1

RLC

DCNtGC

L2/RLC

MAC

RLC

RLC

RLCRLC

RLC

RLC

RLC

Duplication avoidance

UuS boundary

BMCL2/BMC

control

PDCP

PDCP L2/PDCP

DCNtGC

Radio

Bearers

RRC

Layer 1 (L1)

Physical

Layer 2 (L2)

Medium Access Control

Radio Link Control

Broadcast/MulticastControl

Packet DataConvergence Protocol

Layer 3 (L3)

Radio Resource Control

MAC interfaces to:

L1, RLC, RRC layers


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3

PHY

MAC

RLC

PDCP

PHY

MAC

RLC

PDCP

UE Node B RNC

PHY

MAC

RLC

PDCP

PHY

MAC

RLC

PDCP

UE Node B RNC

MAC-hs MAC-hs

Without HSDPA

With HSDPA


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4

Traffic Related ArchitectureUTRAN Side

HS-DSCH HS-DSCH

Associated Uplink

SignallingAssociated Downlink

Signalling

FACH RACH

DCCH DTCHDTCH

DSCH

MAC Control

Iur or local

MAC Control

DCH DCH

MAC-d

USCHTDD only

MAC-c/sh

CPCHFDD only

CCCH CTCHBCCH SHCCHTDD only

PCCH

FACHPCH USCHTDD only

DSCHIub

MAC Control

MAC-hs

Configuration

ithout MAC-c/sh

Configuration

ith MAC-c/sh

Configuration

ith MAC-c/sh


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MAC-d Flow

Each HS-DSCH MAC-d

flow is carried on aseparate Iub/Iurtransport bearer

Each UE can have oneor multiple MAC-d

flow

RLC

Logical

Channels

C/T Mux

UE x UE yRB wRB zRB v RB mRB n

MAC -d

FP

Iub interface

FP

AC -hs

Transport bearer

AC -hs

Transport Channels

RNC

Node B

MAC-d flow


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MAC-hs ArchitectureUTRAN Side

MAC-hs

MACControl

HS-DSCH

TFRC selection

Priority Queuedistribution

Associated DownlinkSignalling

Associated UplinkSignalling

MAC-d flows

HARQ entity

Priority Queuedistribution

PriorityQueue

PriorityQueue

PriorityQueue

PriorityQueue

Scheduling/Priority handling


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MAC-hs FunctionsUTRAN Side

Flow control

MAC-c/sh and MAC-dentities provide acontrolled data flow

Intended to reducediscarded/retransmitted data due tocongestion

Priority Queue

distribution

Priority Queue

distribution

Priority

Queue

Priority

Queue

Priority

Queue

TFRC selection

Priority

Queue

MAC-hs


HARQ entity

MAC-d flow

HS-DSCHAssociated UL

Signaling

Associated DL

Signaling

FlowControl

FlowControl


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Scheduling/Priority

Handling Managing of HS-DSCH

resources and data flowsaccording to priority

Either new transmissionor retransmission isdetermined based onstatus reports from theassociated uplinksignaling

It determines the QueueID and TSN for each newMAC-hs PDU

Priority Queue

distribution

Priority Queue

distribution

Priority

Queue

Priority

Queue

Priority

Queue

TFRC selection

Priority

Queue

MAC-hs


HARQ entity

MAC-d flow


Signaling

Associated DL

Signaling


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HARQ entity

One HARQ entity handlesHARQ functionalities forone user

One HARQ entity iscapable of supportingmultiple HARQ processesof stop-and-wait HARQprotocols

Priority Queue

distribution

Priority Queue

distribution

Priority

Queue

Priority

Queue

Priority

Queue

TFRC selection

Priority

Queue

MAC-hs


HARQ entity

MAC-d flow


Signaling

Associated DL

Signaling


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TFRC selection

Selection of anappropriate transportformat and resource

Channelization code set,modulation scheme, etc.

Priority Queue

distribution

Priority Queue

distribution

Priority

Queue

Priority

Queue

Priority

Queue

TFRC selection

Priority

Queue

MAC-hs


HARQ entity

MAC-d flow


Signaling

Associated DL

Signaling


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MAC-hs ArchitectureUE Side

MAC-hs

MAC Control

Associated Uplink Signalling

To MAC-d

Associated Downlink Signalling

HS-DSCH

HARQ

Reordering Reordering

Re-ordering queue distribution

Disassembly Disassembly


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MAC-hs FunctionsUE Side

HARQ

Handling of the tasksrequired for hybrid ARQ,e.g.,:

Handling of the ProcessID and the New Data

Indicator Delivering of the decoded

MAC-hs PDU to thereordering entity

Generates ACKs or NACKs


Reordering

HARQ

MAC-hs


MAC-d flow


Signaling

Associated DL

Signaling

Reordering


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Reordering Queue

distribution Routing of the MAC-hs

PDUs to the correctreordering buffer based onthe Queue ID


Reordering

HARQ

MAC-hs


MAC-d flow


Signaling

Associated DL

Signaling

Reordering


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Reordering

There is one reorderingentity per Queue ID

Reordering of receivedMAC-hs PDUs according tothe TSN

MAC-hs PDUs withconsecutive TSNs aredelivered to thedisassembly function


Reordering

HARQ

MAC-hs


MAC-d flow


Signaling

Associated DL

Signaling

Reordering


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Disassembly

Removing of the MAC-hsheader and any paddingbits

Extraction of MAC-d PDUsDisassembly Disassembly

Reordering

HARQ

MAC-hs


MAC-d flow


Signaling

Associated DL

Signaling

Reordering


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Priority Queue

distribution

Priority Queue

distribution

Priority

Queue

Priority

Queue

Priority

Queue

TFRC selection

Priority

Queue

MAC-hs


HARQ entity

MAC-d flow


Signaling

Associated DL

Signaling

MAC-d

Logical channel RLC PDU

MAC SDUC/T


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Priority Queue

distribution

Priority Queue

distribution

`Priority

Queue

Priority

Queue

Priority

Queue

TFRC selection

Priority

Queue

MAC-hs


HARQ entity

MAC-d flow


Signaling

Associated DL

Signaling

MAC-d

Logical channel

Scheduling:

CQI analysis

Priority handling

Re-ordering Queue selection

HARQ processRV selection

TFRC selection

CQI analysis

Priority handling

VF Queue ID TSN SID1 N1 F1 SID2 N2 F2 SIDk Nk Fk

MAC-hs header MAC-hs SDU MAC-hs SDU Padding (opt)

MAC-hs payload


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MAC-hs payload

VF: Version Flag

( = 0 for R5)

Transmission Sequence Number

No. of MAC-dPDUs

Flag

( =0 for next SID=1 for payload)

SID:

Size Index


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Reordering

HARQ

MAC-hs


MAC-d flow


Signaling

Associated DL

Signaling

Reordering

MAC-d

Logical channel RLC PDU

MAC SDUC/T



MAC-hs payload


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Control of HS-DSCH TX/RX: scheduler

Scheduler: Network side

Schedules all UEs within a cell

Distributes the MAC-hs SDUs to priority queues accordingly

Determines the HARQ entity and the queue to be serviced

Sets TSN for the MAC-hs PDU transferred from the selected

queue Indicates the Queue ID and TSN to the HARQ entity

Schedules a new transmission or a retransmission

Determines a redundancy version and indicates to L1


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Control of HS-DSCH TX/RX: HARQ entity

Network side

There is one HARQ entity per UE in UTRAN

Sets the Queue ID and TSN in the MAC-hs PDUs

Sets the HARQ process identifier and signals to L1

UE side

Processes HARQ process identifiers in received MAC-hsPDUs

Each received MAC-hs PDU shall be allocated to the HARQprocess indicated by the HARQ process identifier


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Control of HS-DSCH TX/RX: HARQ process

Network side

Sets the New Data Indicator and signals to L1

Processes received status messages and deliver to thescheduler

UE side

Multiple HARQ processes are used parallel Each of them processes the New Data Indicator and the

Queue ID of the corresponding MAC-hs PDU

Depending on the situations, UE shall:

Generate an ACK/NACK signal

Replace the data in the soft buffer with the received data

Discard the received data or combine with the previous data

Deliver the decoded MAC-hs PDU to the reordering entity


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Control of HS-DSCH TX/RX: Reordering entity

Parameters

Transmitter window size (TRANSMIT_WINDOW_SIZE)

TRANSMIT_WINDOW_SIZE is the size of the transmitterwindow

Receiver window size (RECEIVE_WINDOW_SIZE)

RECEIVE_WINDOW_SIZE is the size of the receiver window


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State variables

next_expected_TSN

The TSN following the TSN of the last in-sequence MAC-hs PDU

All received MAC-hs PDUs with consecutive TSNs fromnext_expected_TSN up to the first not received one aredelivered to the disassembly entity

RcvWindow_UpperEdge

The RcvWindow_UpperEdge represents the TSN, which is at theupper edge of the receiver window. After the first MAC-hs PDU has been received successfully, it also corresponds to the MAC-hsPDU with the highest TSN of all received MAC-hs PDUs. The initi

al RcvWindow_UpperEdge equals 63 T1_TSN

The TSN of the latest MAC-hs PDU that cannot be delivered tothe disassembly entity, i.e., T1_TSNnext_expected_TSN


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Timers

Re-ordering release timer (T1)

T1 controls the stall avoidance in the UE reordering buffer

T1 starts when a MAC-hs PDU with TSN > next_expected_TSN iscorrectly received

When T1 expires and T1_TSN>next_expected_TSN, some PDUs

in the reordering buffer are delivered to the disassembly entity

Other definitions

Receiver window

Defines TSNs of those MAC-hs PDUs that can be received in the receiver without causing an advancement of the receiver window

Size of the receiver window equals RECEIVE_WINDOW_SIZE

Spans TSNs going from RcvWindow_UpperEdgeRECEIVE_WINDOW_SIZE + 1 to RcvWindow_UpperEdge included


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Control of HS-DSCH TX/RX: Stall avoidance (T1)

TSN=0 TSN=1 TSN=2 TSN=3

NET = 1 NET = 2

Node B

UE

Start of T1 timer

Successful recovery

TSN=4 TSN=2TSN=2 TSN=3

Node B

UE

NET = 2

T1_TSN = 3

Start T1 timer

NET = 2

T1_TSN = 3

Start T1 timer

NET = 5

Deliver 2 ~ 4 to

disassembly entity


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Control of HS-DSCH TX/RX: Stall avoidance (T1)


NET = 2 NET = 2NET = 2T1_TSN = 3

Start T1 timer

Node B

UE

Expiry of T1 timer

Expiry of T1 timer


NET = 2 NET = 2

Node B

UE

TSN=9

NET = 2

T1 expires

NET = 10Deliver 3 ~ 9

to disassembly entity

TSN=7TSN=6 TSN=8

NET = 2

T1 expires

NET = 6 / T1_TSN = 8

Deliver 3 ~ 5

to disassembly entity

NET = 2

T1_TSN = 3

Start T1 timer


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Control of HS-DSCH TX/RX: Buffer flush

In case a UE has insufficient memory to process a

received MAC-hs PDU select TSN_flush such that: next_expected_TSN < TSN_flush

RcvWindow_UpperEdge + 1;

deliver all correctly received MAC-hs PDUs with TSN < TSN_flush tothe disassembly entity;

if the MAC-hs PDU with TSN=TSN_flush has previously beenreceived:

deliver all received MAC-hs PDUs with consecutive TSNs fromTSN_flush (included) up to the first not received MAC-hs PDU to thedisassembly entity;

advance next_expected_TSN to the TSN of this first not received MAC-hs PDU.

else:

set next_expected_TSN to TSN_flush.


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Control of HS-DSCH TX/RX: Buffer flush

2


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Control of HS-DSCH TX/RX: Disassembly entity

Disassembly entity

Remove any padding bits if present for each MAC-hs PDU

Remove the MAC-hs header

Deliver the MAC-d PDUs in the MAC-hs PDU to MAC-d


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Control of HS-DSCH TX/RX: MAC-hs Reset

MAC-hs Reset

If requested by upper layers, the UE shall:

Flush soft buffers for HARQ processes and reordering buffers

Initialize T1, TSN and other parameters

Disassemble all MAC-hs PDUs and deliver to the MAC-d entity

INDicate to all AM RLC entities


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Control of HS-DSCH TX/RX: Reconfiguration

Reconfiguration of MAC-hs parameters

The parameters for a MAC-hs entity may be reconfiguredby upper layers

hsdpa l2 overview

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