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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.
Radio Network Controller (RNC)
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.
Radio Network Controller (RNC)
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.
Radio Network Controller (RNC)
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)
Radio Network Controller (RNC)
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.
Radio Network Controller (RNC)
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
Radio Network Controller (RNC)
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.
Channel Organization
Channel Organization
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
Channel Organization
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.
DPDCH #2 (optional) Dedicated Physical Data Ch.
DPDCH #4 (optional) Dedicated Physical Data Ch.
DPDCH #6 (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
Secondary Scrambling Codes
(15)
Primary SC7
Secondary Scrambling Codes
(15)
Code Group # 1 Code Group # 1
Primary SCo
Secondary Scrambling Codes
(15)
Primary SC504
Secondary Scrambling Codes
(15)
Primary SC511
Secondary Scrambling Codes
(15)
Code Group # 64
Codes Statistics