hsdpa l2 overview
TRANSCRIPT
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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
con
trol
con
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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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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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
Scheduling/Priority handling
HARQ entity
MAC-d flow
HS-DSCHAssociated UL
Signaling
Associated DL
Signaling
FlowControl
FlowControl
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MAC-hs FunctionsUTRAN Side
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
Scheduling/Priority handling
HARQ entity
MAC-d flow
HS-DSCHAssociated UL
Signaling
Associated DL
Signaling
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MAC-hs FunctionsUTRAN Side
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
Scheduling/Priority handling
HARQ entity
MAC-d flow
HS-DSCHAssociated UL
Signaling
Associated DL
Signaling
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MAC-hs FunctionsUTRAN Side
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
Scheduling/Priority handling
HARQ entity
MAC-d flow
HS-DSCHAssociated UL
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
Disassembly Disassembly
Reordering
HARQ
MAC-hs
Re-ordering queue distribution
MAC-d flow
HS-DSCHAssociated UL
Signaling
Associated DL
Signaling
Reordering
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MAC-hs FunctionsUE Side
Reordering Queue
distribution Routing of the MAC-hs
PDUs to the correctreordering buffer based onthe Queue ID
Disassembly Disassembly
Reordering
HARQ
MAC-hs
Re-ordering queue distribution
MAC-d flow
HS-DSCHAssociated UL
Signaling
Associated DL
Signaling
Reordering
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MAC-hs FunctionsUE Side
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
Disassembly Disassembly
Reordering
HARQ
MAC-hs
Re-ordering queue distribution
MAC-d flow
HS-DSCHAssociated UL
Signaling
Associated DL
Signaling
Reordering
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MAC-hs FunctionsUE Side
Disassembly
Removing of the MAC-hsheader and any paddingbits
Extraction of MAC-d PDUsDisassembly Disassembly
Reordering
HARQ
MAC-hs
Re-ordering queue distribution
MAC-d flow
HS-DSCHAssociated UL
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
Scheduling/Priority handling
HARQ entity
MAC-d flow
HS-DSCHAssociated UL
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
Scheduling/Priority handling
HARQ entity
MAC-d flow
HS-DSCHAssociated UL
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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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
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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Disassembly Disassembly
Reordering
HARQ
MAC-hs
Re-ordering queue distribution
MAC-d flow
HS-DSCHAssociated UL
Signaling
Associated DL
Signaling
Reordering
MAC-d
Logical channel RLC PDU
MAC SDUC/T
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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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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Control of HS-DSCH TX/RX: Reordering entity
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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Control of HS-DSCH TX/RX: Reordering entity
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)
TSN=4 TSN=5TSN=2 TSN=3
NET = 2 NET = 2NET = 2T1_TSN = 3
Start T1 timer
Node B
UE
Expiry of T1 timer
Expiry of T1 timer
TSN=4 TSN=5TSN=2 TSN=3
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