1/60 UMTS AIR CHANNEL TYPES AND THEIR FUNCTION by Nasir Faruk Dept of TCS, UNILORIN.

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UMTS AIR UMTS AIR CHANNEL TYPES CHANNEL TYPES

AND THEIR AND THEIR FUNCTIONFUNCTION

bybyNasir FarukNasir Faruk

Dept of TCS, UNILORINDept of TCS, UNILORIN

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UMTS AIR CHANNEL TYPES

• There are 3 types of channels across air interface

Physical channel: carries data between physical layers of UE and NodeB

Transport channel: carries data between physical layer and MAC layer

Logical channel: carries data between MAC layer and RRC layer

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Air Interface Access Stratum

Figure 5

Control Plane Signalling User Plane Information

L3

L2

L1 Physical Layer

Medium AccessControl (MAC)

TransportChannels

LogicalChannels

Radio LinkControl (RLC)

Radio ResourceControl (RRC)

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UE to UTRAN protocol stack (air interface layers)

The radio interface is divided into 3 layers:

1.Physical layer (Layer 1, L1): used to transmit data over the air, responsible for

channel coding, interleaving, repetition, modulation, power control, macro-diversity combining.

2. Link layer (L2): is split into 2 sub-layers – Medium Access Control (MAC) and Radio Link Control (RLC).

a)MAC: responsible for multiplexing data from multiple applications

onto physical channels in preparation for over-the-air transmission.b)RLC: segments the data streams into frames that are small enough

to be transmitted over the radio link

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Upper layer (L3): vertically partitioned into 2 planes: control plane for signaling and user plan for bearer traffic.

RRC (Radio Resource Control) is the control plan protocol: controls the radio resources for the access network.

In implementation:

1. UE has all 3 layers.

2. NodeB has Physical Layer.

3. RNC had MAC layer and RRC layer.

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Transport Channels• Two types

1.Dedicated transport channels (DCH): Single User

i. Downlink shared channel (DSCH)

ii. DCH

2. Common transport channels (CCH): Group of Users

i. Broadcast channel (BCH)

ii. Forward access channel (FACH)

iii.Paging channels (PCH)

iv.Random access channel (RACH)

v. Uplink common packet channel (CPCH)

Only I,ii,III and iv are needed for basic network

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Physical Channels1. Common control channel:i. P-CCPCH :

ii. S-CCPCH

iii. P-SCH

iv. S-SCH

v. CPICH

vi. AICH

vii. PICH

viii. PDSCH

ix. PRACH: UL

x. PCPCH: UL

xi. CD/CA-ICH.

2. Dedicated channel:

i. DPDCH: UL

ii. DPCCH: UL

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Mapping of Transport channels onto the Physical Channels

Transport Channels Physical channels

BCH PCCPCH

FACH SCCPCH

PCH

RACH PRACH

DCH DPDCH

DPCCH

DSCH PDSCH

CPCH PCPCH

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Logical Channels

MAC

FACH DSCH DCH

BCCH PCCHDCCH CCCH

CTCHDTCH

BCH PCH

Physical Layer

CPCH RACH

P-CCPCH PDSCHS-CCPCH DPDCH

DPCH

DPCCH

SCHCSICH CPICHAICHCD/CA-ICH

AP-AICH

PICH

TransportChannels

Layer 2

Layer 1

PRACHPCPCHPhysical

Channels

NB. The bubbles are SAPs, Service Access Points, logical software gateways between the different layersSome channels only originate from and in the Physical Layer, e.g. CSICH etc.

UMTS Logical-Transport-Physical Channel Mapping

Node B RF Modulator/Demodulator© Dr Maaruf Ali

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Physical Channels in Details• DPDCH: UL, carries data from one user

– DPCCH: UL, use to carry control information–power control command and –format associated with the DPDCH.

– Usually only one DPCCH regardless of the no. of DPDCHs

• PRACH: UL, is used to carry RACH msgs– It uses slotted ALOHA protocol

I. UE Tx preamble to BTS

II. If no ack, then

III.UE TX with higher power

IV.Repeat III until ack is rcv

V. Then, UE TX PRACH msg at this power level

VI.Msg (Data + contr)

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• Physical common packet channels (PCPCH)– Shared CH, carries packet-based data

– CH access based on CSMA/CD

• Common pilot channel (CPICH)– Conti.. DL pilot CH– Training sequence– Aid channel assessment/estimation– They are Transmitted at fixed rate

–Two types of CPICH:–P-CPICH:

»Used for measurement for handover and cell selection»Control cell load by adjusting the power level, forced handover if power level is reduced»Characterized by fixed channelization code, P-SC

–S-CPICH:»May have many channelization code of length 256, S-SC

»Usually, used to serve “Hot spots”

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• Common control physical channel (CCPCH)– Used to carry upper layer transport CHs

– E.g BCH carried on P-CCPCH

– FACH and PCH carried on S-CCPCH

• P-CCPCH:– Used to send cell specific information to all UEs

– It operates on SF of 256= 30 kbps on the air interface

– It is time multiplexed with the SCH

– The 1st 256 chips are used by SCH, the remaining 2304 chips are used by the P-CCPCH to carry BCH

• S-CCPCH:– Used to carry FACH to send infor to UEs after UE makes a random

access attempt on the PRACH

– Used to carry PCH, carries pages from BTS to a UE

– S-CCPCH carrying PCH must be transmitted over the whole cell area regardless if it carrying FACH

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• Synchronisation channel (SCH)– The first channel UE looks for at strat-up rem GSM initialization

process!– SCH active only during the first 256 chips of each slot

• Two types:

• P-SCH: – carries the same signal for all cell in the system and it is used by

the UE to obtain chip, symbol and slot synchronization

• S-SCH: – is different for each cell. It carries pattern of secondary

synchronization codes (SSC) that repeat every frame. Once UE receives this sequence it will have sync

• Physical downlink shared channel (PDSCH)– Used to carry downlink shred transport channel– Carries control info for several users that shared the channel

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• Indicator channels

• Paging indicator channel (PICH)– To notify all UEs in a giving paging group

• Acquisition indicator channel (AICH)– To notify UE that it has rcv the UE’s PRACH

preamble during the open loop power control

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Protocol Termination

Figure 6

Physical

MAC

RLC

RRC

Physical

MAC

RLC

RRC

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UserEquipment Uu

Iub

RadioNetwork

Controller

NodeB

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Functions of MAC

Figure 12

Logical to TransportChannel Mapping

Selection of Transport Format

PriorityHandling

Identification ofUEs on Common

Transport Channels

Multiplexing ofPDUs into Transport

Blocks

Traffic VolumeMonitoring

Dynamic TransportChannel Type Switching

MAC FunctionsMAC Functions

Access Class Selectionfor RACH and CPCH

Ciphering for TrM RLC

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Common Pilot Signal

Figure 20

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Node B

All UEsuse the samecommon pilot

Pilot

Signalling/Traffic

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Channel Associated Pilot

Figure 22

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Node B

UEs

Pilot sequences

Traffic/Signalling

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Each channelcarries its own pilot

Traffic/Signalling

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Sectorisation

Figure 33

Three Sector Six Sector

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Frame Structure

Figure 10

0 1 71

Superframe Duration 720 ms

0 1 2 3 4 5 6 7 8 9 11 12 13 1410

Radio Frame Duration 10 ms

0 2 4,0944

Hyperframe Duration 40.96 s

Timeslot Duration666.7 µs2,560 chips

2

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TDD Switching Points

Figure 32

0 1 2 3 4 5 6 7 8 9 11 12 13 1410

Single Switching Point

0 1 2 3 4 5 6 7 8 9 11 12 13 1410

Multiple Switching Point

DL UL DL

DL UL DL UL DL UL DL UL DL UL DL UL DL UL DL

Frame 10 ms

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Variable Spreading or Variable Codes

Figure 33

Code 1 High Bit RateLow SpreadingFactor

TS N–1 TS N TS N+1 TS N+2

666.7 µs

Code 1

Code 2

Code 3

Code 4

Code 5

Code 6

Low Bit RateHigh SpreadingFactor

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Resource Unit

Figure 34

Time

Frequency

Co

de

Timeslot

RadioChannelCode

10 ms

1 2 3 4 5 6 7 8 9 1011 12 13 14

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Burst Types

Figure 36

Timeslots666.7 µs

GP

96chips

Data symbols61,122,244,488,976

976 chips

Data symbols61,122,244,488,976

976 chips

Midamble

512 chips

BURST TYPE 1

BURST TYPE 2

GP

96chips

Data symbols69,138,276,552,1104

1104 chips

Data symbols69,138,276,552,1104

1104 chips

Midamble

256 chips

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Measurement Control

Figure 20

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UE

Node B

RRC

Measurement Contro

l RNC

Iub

Uu

• Measurement type• Measurement identity number• Measurement command• Measurement objects• Measurement quantity• Reporting quantities• Measurement reporting criteria• Reporting mode

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Requirement for Synchronisation

Figure 22

Cell Scrambling Code Derived from SCH

BCCH Spreading Code Known

BCCH Rate Known

Code Time Alignments Derived from SCH

Slot/Frame Time Alignments Derived from SCH

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UL

Data

TCPPilot TFCI FBI

DPDCH

DPCCH

I/Q Multiplexed in the UL

Pilot : For channel assessmentTransport format combination identifier: Combine several TF from transport channels to form TFC block

Feedback information indicator: Channel diversity

Transmitter power control: Power control

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DL

DataData TPC TFCI

DPDCH DPCCH

Time Multiplexed in the DLPilot

DPCCH DPCCHDPDCH

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SSDT

Figure 32

12

3

SRNC

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Node B

lub

Node B

Node B1

lub

lub

DPDCCH/

DPCCH

DPCCH only

DPCCH only

UE nominatesNode B

as Primary

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Intra- and Inter-Frequency Measurements

Figure 34

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UMTS Macro

UMTS Macro

UMTS MacroF1

F1

F1

UMTS Macro

UMTS Macro

F1

F2

F1

UE

UMTS Micro

Rake receiver is only able to see neighbourcells on the same frequency

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Transmit Diversity

Figure 40

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UE

Node B

FBI bit used in closed loop mode

Multipath set fromantenna TX 2

Multipath set fromantenna TX 1

TX 2

TX 1

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Any Questions ?Any Questions ?

1/60 UMTS AIR CHANNEL TYPES AND THEIR FUNCTION by Nasir Faruk Dept of TCS, UNILORIN.

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Transcript of 1/60 UMTS AIR CHANNEL TYPES AND THEIR FUNCTION by Nasir Faruk Dept of TCS, UNILORIN.