WCDMA Chnl concepts.ppt

WCDMA Radio Channels

UE UTRAN CN

Uu Iu

UE – User Equipment RAN – Radio Access Network

UTRAN – UMTS Terrestrial RAN CN – Core Network

Basic UMTS Architecture

USIM

ME

Cu

UE

The 3G Network terminal is called UE and it contains two separate parts, Mobile Equipment (ME) and UMTS Service Identity Module (USIM).

The Interface between USIM and UE is called Cu interface.

User Equipment (UE)

Node B

Node B

RNC

Node B

Node B

RNC

The subsystem controlling the wideband radio access has different names, depending on the type of radio technology used. The general term is Radio Access Network (RAN).

If especially talking about UMTS with WCDMA radio access, the name UTRAN or UTRA is used

UMTS Radio Access Network (UTRAN)

Iur

RNS

RNS

Iub

Iub

The UTRAN is divided into Radio Network Subsystem (RNS). One RNS consist of set of radio elements and their corresponding controlling element. In UTRAN the radio element is Node B or Base Station (BS), and the controlling element is Radio Network Controller (RNC).

The RNSs are connected to each other over access network-internal interface Iur

UMTS Radio Access Network (UTRAN)

Node B

Node B

RNC

Node B

Node B

RNC

Iur

RNS

RNS

Node B

Node B

RNC

Node B

Node B

RNC

Iur

RNS

RNS

Iub

Iub

UMTS Base Station

• It logically corresponds to GSM BTS.

• It is also known as Node B.

• It is located between the Uu and Iub interface.

• Main task is to establish the physical implementation of Uu interface towards UE and Iub interface towards the network.

• Convert the data flow between the Iub and Uu interface.

• Participate in radio resources management.

Radio Network Controller (RNC)

•It is the switching and controlling element of the UTRAN.

•It is located between the Iub and Iu interface.

•It also has the third interface called Iur for inter-RNS connection.

•It interfaces the core network.

•It terminates the Radio Resource Control (RRC).

•It logically corresponds to the GSM BSC.

•It controls the mobility and handover within the RAN.

•It supports Radio Access Bearer (RAB) services with CS and PS data.


Logical Roles of the RNC.

1. Controlling RNC (CRNC)

2. Serving RNC (SRNC)

3. Drift RNC (DRNC)

One Physical RNC normally contains all the CRNC , SRNC and DRNC functionality.


Controlling RNC (CRNC)

The RNC controlling one Node B (i.e terminating the Iub interface towards the Node B) is indicated as the controlling RNC of the Node B. The CRNC is responsible for the load and congestion control of its own cells and also executes the admission control and code allocation for new radio link to be established in those cell.


In case one mobile – UTRAN connection uses resources from more than one RNS , the RNCs involved have two separate roles with respect to this mobile – UTRAN connection

Serving RNC (SRNC)

Drift RNC (DRNC)


Serving RNC (SRNC)

The serving RNC for one mobile is the RNC that terminates both the Iu link for the transport of user data and the corresponding RAN application part signalling to / from the CN (this connection is referred to as the RANAP connection)

The SRNC also terminates the signaling protocol between the UE and UTRAN.


Serving RNC (SRNC)

It performs the L2 processing of the data to / from the radio interface.

Basic RRM operations such as the mapping of radio access bearer (RAB) parameters into air interface transport channel parameter, the handover decision and the outer loop power control are executed in the SRNC.

The SRNC may also (but not always) be the CRNC of some Node B used by the mobile connection with UTRAN.

One UE connected to UTRAN has one and only one SRNC


Drift RNC (DRNC)

The DRNC is any RNC , other than the SRNC , that controls cells used by the mobile.

The DRNC does not perform L2 processing of the user plane data but routes the data transparently between Iub and Iur interfaces.

One UE may have zero , one or more DRNCs

Multipath Propagation

1 0

2

3

Time Dispersion

1

0

2

3

Rake Receiver

• The signals arriving at the mobile have taken different paths from the base station. • The length of each path is different so the time taken for the signals to reach the mobile is different. • These signals will be dispersed in time when they reach the mobile. Signals can combine and produce a greater signal level or can completely cancel each other out. • his phenomenon is known as multi-path fading and it affects all radio systems, not only WCDMA.

Rake Receiver

C

O

M

B

I

N

E

R Power measurements of neighboring BS

Sum of individual multipath components

Finger #1

Finger #2

Finger #3

Searcher Finger

Finger #N

Buffer/delay

CorrelatorsChannel

RAKE Receiver

Rake Receiver

The RAKE Receiver works by putting the received signal through a series of variable delays and correlating each with the desired scrambling code. A process known as the Maximum Ratio Combining is then preformed to produce the output. Each of these delays can be regarded as a separate receive, separated in phase from the others. Each of these paths is called a finger. The number of fingers that a receiver will have may be vendor specific. If for example a receiver had five fingers, four of these would be used for tracking multi-path components and the fifth for identifying other Base Stations. This finger is called the searcher finger.

RAKE principle

SELECT

COMBINE

BUFFER

FromBTS

WCDMA Frame Structure

• Frame length is 10ms.

• One frame is divided into 15 slots.

• 1 slots = 2/3 ms = 0.666ms.

• One frame is able to handle 38400 chips.

• One slot carry 2560 chips.

WCDMA radio access allocates bandwidth for users , the allocated bandwidth and its controlling functions are handled with the term Channel

What is Channel ?

Channel Organization

The Channel organization of the WCDMA is in three layers

• Logical Channel

• Transport Channel

• Physical Channel

Channel Types and their location in UTRAN

UE

Node-B RNC

Logical Channels

Transport Channels

Physical Channels

• Logical channels define what type of data is transferred.

• Transport channels define how and with which type of characteristics the data is transferred by the physical layer.

• Physical channel define the exact physical characteristics of the radio channel.



In

Downlink direction

Logical channel types are classified into two groups:

Logical Channels

• Control channels for the transfer of control information

• Traffic channels for the transfer of user information.

Logical Channels

Common Downlink Logical Channels

BCCH (Broadcast Control Channel) - Broadcasts cell and system information to all UEPCCH (Paging Control Channel) - Transmits paging information to a UE when the UE’s location is unknownCCCH (Common Control Channel) - Transmits control information to a UE when there is no RRC ConnectionCTCH (Common Traffic Channel) - Traffic channel for sending traffic to a group of UE’s.

DCCH (Dedicated Control Channel) - Transmits control information to a UE when there is a RRC Connection

DTCH (Dedicated Traffic Channel) - Traffic channel dedicated to one UE

Logical Channels

Dedicated Downlink Logical Channels

There are two types of Transport channels

Transport Channels

• Common channels

• Dedicated channels.

Common Downlink Transport Channels

Transport Channels

BCH (Broadcast Channel) - Continuous transmission of system and cell information

PCH (Paging Channel) - Carries control information to UE when location is unknown

FACH (Forward Access Channel) - Used for transmission of idle-mode control information to a UE - Control signaling during call set-up

Common Downlink Transport Channels

Transport Channels

DSCH (Downlink Shared Channel) - Used for dedicated control or traffic data (bursty traffic). Shared by several users

DCH (Dedicated Channel) - Carries dedicated traffic and control data to one UE

Mapping of Channels (Downlink Direction)

BCCH PCCH CTCH CCCH DCCH DTCH

BCH PCH FACH DCH DSCH

Logical Channels

Transport Channels

Physical Channels

The physical channel actually form the physical existence of the Uu interface between the UE domain and access domain.

UE

Node-B

Physical Channels

Uu

Physical Channels

In GSM the physical channels and their structure is recognized by the BSC but in WCDMA the physical channel really exist in the Uu interface and the RNC is not necessarily aware of their structure at all .Instead of physical channel the RNC sees transport channels.

Transport Channel carry different information flows over the Uu interface and the physical element mapping these information flows to the physical channel is the Node-B.

Physical Channels

Common Downlink Physical Channels

Primary Common Control Physical Channel (P-CCPCH) - Broadcasts system information.

Synchronization Channel (SCH)- Carries Primary and Secondary Synchronization Codes, used for slot synchronization, frame synchronization and the detection of the scrambling code group (one out of 64). It is time multiplexed (only first 10%) with the P-CCPCH (remaining 90% of timeslot).

Secondary Common Control Physical Channel (S-CCPCH)- Carries both the Paging Channel (PCH) and the Forward Access Channel (FACH). Transmits idle-mode signaling and control information to UE.

Physical Channels

Common Downlink Physical Channels

Dedicated Downlink Physical Channels

Physical Channels

Dedicated Downlink Physical Data Channel (DPDCH) - Used for sending dedicated user data .

Dedicated Downlink Physical Control Channel (DPCCH) - Used for transmitting the control information during the dedicated connection e.g power control information.

Shared Downlink Physical Channels

Physical Channels

High-Speed Physical Downlink Shared Channel (HS-PDSCH) - Used for sending users data (Shared mode).

HS-SCCH - High-Speed Shared Control Channel(s) - physical downlink channel that carries control information how to decode the information on HS-PDSCH and which UE that shall decode it.

Mapping of Channels (Downlink Direction)

BCCH PCCH CTCH CCCH DCCH DTCH

BCH PCH FACH DCH DSCH

Logical

Channels

Transport

Channels

P-CCPCH S-CCPCH DPDCH DPCCH PDSCH Physical

Channels

WCDMA Downlink

BCCHBroadcast Control Ch.

PCCHPaging Control Ch.

CCCHCommon Control Ch.

DCCHDedicated Control Ch.

DTCHDedicated Traffic Ch. N

BCHBroadcast Ch.

PCHPaging Ch.

FACHForward Access Ch.

DCHDedicated Ch.

P-CCPCH(*)Primary Common Control Physical Ch.

S-CCPCHSecondary Common Control

Physical Ch.

DPDCH (one or more per UE) Dedicated Physical Data Ch.

DPCCH (one per UE)Dedicated Physical Control Ch.

Pilot, TPC, TFCI bits

SSCi

Logical Channels(Layers 2+)

Transport Channels(Layer 2)

Physical Channels(Layer 1)

DownlinkRF Out

DPCH (Dedicated Physical Channel)One per UE

HS-DSCHHigh Speed DL Shared Ch.

CTCHCommon Traffic Ch.

CPICHCommon Pilot Channel

Null Data

Data Encoding

Data Encoding

Data Encoding

Data Encoding

Data Encoding

HS- PDSCH (one or more per UE) High Speed Physical Downlink shared Channel

S/P

S/P

S/P

I+jQI/Q

Modulator

Q

I

Cch

Cch 256,1

Cch 256,0

GS

PSC

GP

Sync Codes(*)

* Note regarding P-CCPCH and SCH

Sync Codes are transmitted only in bits 0-255 of each timeslot;P-CCPCH transmits only during the remaining bits of each timeslot

Filter

Filter

Gain

Gain

Gain

SCH (Sync Channel)

DTCHDedicated Traffic Ch. 1

DCHDedicated Ch.

Data Encoding M

UX

MUX

CCTrCH

DCHDedicated Ch.

Data Encoding

Sdl,n

Sdl,n

Sdl,n

S/P

Cch GainSdl,n

S/P

C16 GainSdl,n

AICH (Acquisition Indicator Channel)

PICH (Paging Indicator Channel )

Access Indication data

Paging Indication bits S/P

S/P

Cch

CchGain

Gain

Sdl,n

Sdl,n

HS-SCCH (<=4 per UE)High Speed Shared Control Channel .

S/P

C128 GainSdl,n

TFRI, UE Identity, HARQ

SS

SS

E-AGCH (<=4 per UE, serving cell)E-DCH Absolute Grant Channel

S/P

C256 GainSdl,n

C128 GainSdl,n

E-HICH (E-DCH Hybrid ARQ Indication Channel)

E-RGCH (non-serving cell)(E-DCH Relative Grant Channel)

ACK/NACK

Relative grant

Activation flagPower ratio

Data Encoding

Data Encoding

EUL

HSDPA

Slot 14Slot iSlot 2Slot 0

Frame 1 Frame 2 Frame i Frame 72

10 ms

One super frame = 720 ms

“IQ” MuxData Data(TFI)TPCPilot

DPDCHDPCCH

2560 Chips, 10x2k bits

Downlink Dedicated Physical Channels

DPDCH/

DPCCH

S Pbits to

symbols

Cch

• OVSF codes ensure DL orthogonality even with different rates and spreading factors for different users

Cch: Channelization codes (OVSF codes, 4-512 chips)

Cscramb: Downlink scrambling code (Gold code, 38400 chips)

Cscramb

Downlink Spreading and Modulation

QPSKmodulation


In

Uplink direction

Logical Channels

In the Uplink direction the logical channel requirement is smaller. There are only three logical channels

CCCH , DTCH and DCCH

These abbreviation have the same meaning as in the downlink direction

Common Uplink Transport Channels

Transport Channels

RACH Random Access Channel - Carries access requests, control information - Subject to random access collisions

Dedicated Uplink Transport Channels

DCH Dedicated Channel - Carries dedicated traffic and control data from one UE

Mapping of Channels (Uplink Direction)

CCCH DTCH DCCH

RACH DCH

Logical Channels

Transport Channels

PRACH DPDCH DPCCH Physical Channels

Logical Channels(Layers 2+)

Transport Channels(Layer 2)

Physical Channels(Layer 1)

UplinkRF Out

UEScrambling

Code

I+jQI/Q

Mod.

Q

IFilter

Filter

I

DPDCH #1Dedicated Physical Data Ch.

DPDCH #3 (optional)Dedicated Physical Data Ch.

DPDCH #5 (optional) Dedicated Physical Data Ch.




Q

DPCCHDedicated Physical Control Ch.

Pilot, TPC, TFCI bits

Chd,3 Gd

Chd,5 Gd

Chd,2 Gd

Chd,4 Gd

Chd,6 Gd

Ch256,0 Gd

j

DCCHDedicated Control Ch.

DTCHDedicated Traffic Ch. N

DCHDedicated Ch.

Data Encoding

DTCHDedicated Traffic Ch. 1

DCHDedicated Ch.

Data Encoding M

UX

CCTrCH

DCHDedicated Ch.

Data Encoding

HS-DPCCHHigh Speed Dedicated Physical Control Ch.

Chd,1 Gd

CCCHCommon Control Ch.

RACHRandom Access Ch.

PRACHPhysical Random Access Ch.

Data Coding

j

RACH Control Part

Chd Gd

Chc Gc

Ch256 Gd

QE-DPDCH #2

Ch 4,1

GdE-DCH

E-DPCCH

I

Ch 256,1Gd

E-DPDCH #1

Ch 4,1 Gd

j

RSNE-TFCI

Happy bit

Data Encoding

MAC-esMAC-e

Data Encoding

ACK, CQIHSDPA

EUL

j

WCDMA Uplink

Uplink Dedicated Physical Channels

DPDCH

DPCCH “Q” MuxPilot (TFI)TPC

Data

Slot 14Slot iSlot 2Slot 0

Frame 1 Frame 2 Frame i Frame 72

10 ms

One super frame = 720 ms

“I” Mux

2560 Chips, 10x2k bits

DPDCH

DPCCH

CCH,di

CCH,di

Q

I

IQMux

I+jQ

Cscramb

QPSKmodulation

Multi-code transmissionAdditional data channels DPDCHs added to either I or Q

CCH,di:Channelization codes (OVSF codes, 4-256 chips)Cscramb:Scrambling code (long Gold code, 38400 chips, or short VL Kasami code, 256 chips)

Uplink Spreading and Modulation

Codes Statistics

Total 218 - 1 = 262143 scrambling codes can be generated.

Out of 262143 total 8192 codes are used.

8192 codes are divided into 512 code sets.

Each codes sets contains 16 scrambling codes.

Out of 16 scrambling codes 1 is primary scrambling code and 15 are secondary scrambling codes.

Each scrambling code contains 256 channelization codes.

Downlink

Scrambling codes can be generated = 224.Uplink

8192 Downlink Scrambling CodesEach code is 38,400 chips of a 218 – 1 (262,143 chip) Gold sequence

Code Group # 1

Primary SCo

Secondary Scrambling Codes

(15)

Primary SCo


(15)

Primary SC7


(15)

Code Group # 1 Code Group # 1

Primary SCo


(15)

Primary SC504


(15)

Primary SC511


(15)

Code Group # 64

Codes Statistics

WCDMA Chnl concepts.ppt

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