WPO-03 WCDMA Radio Channel Structure
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Transcript of WPO-03 WCDMA Radio Channel Structure
WCDMA Radio Channel Structure
ZTE University
Objectives
At the end of this course, you will be able to :– Master system channel types
– Master function of the channels
Content
Type of System Channel
Function of the Channels
RNS RNS
NodeB NodeBNodeB NodeB
RNC
CN
RNC
Iu Iu
Iur
Iub IubIub Iub
UTRAN System Structure
Channel Types ( UTRAN)
Physical
Channel
Transpor
tation
Channel
Logical
Channel
Node B RNC
Physical channel
Transportation channel
Logical channel
UE
UTRAN Radio Interface Protocol
L3
co
ntr
ol
co
ntr
ol
co
ntr
ol
co
ntr
ol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2/MAC
L1
RLC
DCNtGC
L2/RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2/BMC
control
PDCPPDCP L2/PDCP
DCNtGC
RadioBearers
RRC
Channel Types
For the radio interfaces in WCDMA system, according to different protocol layer, channels that carry user businesses are divided into:
Logical Channel : Directly carry user business ; according to the business that
carried is of control side or user side, it is divided into two categories, control channel and business channel.
Transportation Channel : Describe how data is transmitted at air interface; it is the interface
between radio interface 2 and physical layer, and the services that physical layer provided to MAC layer; Transportation channel is divided into private channel and public channel, which are respectively used to transmit private information to single user and public information to all users.
Physical Channel : The ultimate forms when all kinds of information are transmitted at
radio interface, with each form using a specific carrier frequency, code (spreading code and scrambling code) and relative carrier phase. All these can be considered as a specific channel.
Channels
PHY layer
MAC layer
RLC layer
Transportation channel
Physical channel
Logical channel
L1
L2
Business and Functions of L1
L1 is mainly to provide data transmission service to MAC and higher layers ;
Functions of L1 : Error detection for transportation channel Interleaving and deinterleaving of transportation channel Multiplexing and demultiplexing from transportation channel
to CCTrCH Encoded transportation channel speed adapted to physical
channel CCTrCH reflection to physical channel Weighing and combination of physical channel Modulation/demodulation, spreading/despreading of
physical channel Frequency and time synchronization Radio features measurement ( FER 、 SIR ) Close loop power control RF processing
Business and Functions of MAC
MAC business is expressed by logical channel. MAC Functions :
Reflection of logical channel and transportation channel Select proper transportation format according to real-time
speed Priority adjustment to the data flow of a same UE Inter-UE priority adjustment Multiplexing and demultiplexing of the last session data
being transported at public or private transportation channels
Business flow monitoring Type switching and encryption of transportation channel Business level selection while RACH launching
Business and Functions of RLC
Businesses that RLC provided to upper layer : Establishment/Release of RLC connection, transparent
data transmission, no-answer data transmission, answered data transmission, unrecoverable error notifications, etc.
RLC Functions : Segmentation and Reassembly Serial connection, and PADDING Transmission of user data Error detection PDU sequential delivery Repeat detection Flow control Serial number detection Protocol error detection and recovery Data information encryption Hang up and recovery of data transmission
RLC Working Mode
Transparent Mode : No protocol overhead is added to RLC before SDU. Incorrect PDU
will be discarded or marked as error. Transparent mode is generally used for real-time or streaming
business. No-answer mode
No retransmission mechanism, the accuracy of data transmission cannot be ensured. While receiving, incorrect PDU will be discarded or marked as error. At sending end, discarding will be performed based on time, the data timed out during sending will be discarded.
Typical no-answer mode application is VOIP and cell broadcast. Answered Mode
In answered mode, ARQ is used to ensure the accuracy of data transmission. RLC is two-way in answered mode. Information need to be exchanged on the two direction to judge the accurate receiving of the data, thus data will be retransmitted while failure or notification will be given to identify if data was successfully received.
Typical answered mode business is group business, such as WEB browsing, mail downloading, etc.
PDCP Functions
Reflect network PDU from network protocol to RLC protocol ;
Header compression/decompression, to reduce the redundancy control message in upper layer data, and improve the efficiency of air interface ; TCP/IP ——Non-real time IP RTP/UDP/IP in Rel4——Real time IP ( e.g. VOIP )
Cache, retransmit upper layer data
Note : PDCP exists only in PS
RRC Functions Broadcast management of system information ; Paging/notification ; RRC connection management (establishment,
reestablishment, maintenance and release) ; Radio carrier management (establishment,
reconfiguration and release) to provide service to NAS ; Mobile management of RRC connection ; Initial cell selection ; Requested Qos control and reflection to different
resources in access layer Management and control of radio resources ; UE measurement control and measurement report.
High Layer PDU
RLC SDU
High Layer PDU
RLC
Header
RLC
Header
MAC SDU MAC SDUMAC
Header
MAC
Header
Transport Block Transport Block
CRC CRC
RLC SDU
……
……
……
……
……
High Layer
L2 RLC
( Non-transparent mode )
L2 MAC
(Non-transparent mode)
L1
Segmentation
and cascadingReassembly
Data Flow at Uu Interface
Physical Channel
Dedicated Physical Channel (DPCH)
Physical Random Access Channel (PRACH)
Physical Common Packet Channel (PCPCH)
Uplink Physical Channels
Secondary Common Control Physical Channel (S-CCPCH)
Common Pilot Channel (CPICH)
Primary Common Control Physical Channel (P-CCPCH)
Synchronisation Channel (SCH)
Physical Downlink Shared Channel (PDSCH)
Downlink Physical Channels
Acquisition Indication Channel (AICH)
Page Indication Channel (PICH)
Dedicated Physical Channel (DPCH)
Transportation Channel
Random Access Channel (RACH)
Broadcast Channel (BCH)
Paging Channel (PCH)
Forward Access Channel (FACH)
Common Packet Channel (CPCH)
Common Transport Channels
Dedicated Transport Channels
Downlink Shared Channel (DSCH)
Dedicated Channel (DCH)
Logical Channel
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )
C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
Reflection of Transportation Channel and Physical Channel
Content
Type of System Channel
Functions of the Channel
Physical Channel
Transportation Channel
Uplink Physical Channel
Two dedicated uplink physical channels (DPDCH and DPCCH)
Two public physical channels (PRACH and PCPCH)
DPCCH
PRACH
PCPCH
DPCCH
uplink physical channels
public physical channels
Uplink Dedicated Physical Channel Structure
DPCCH contains 4 domains : Pilot : used for channel estimation of base station receiver and frame
synchronization ; TFCI : determine different TrCHS transmission format while multiplexing
to a same CCTrCH ; FBI : used for downlink closed loop emission classifications ; TPC : used for the power control instructions in downlink closed loop
power control
Pilot N pilot bits
TPC N TPC bits
DataN data bits
Slot #0 Slot #1 Slot #i Slot #14
T slot = 2560 chips, 10 bits
1 radio frame: T f = 10 ms
DPDCH
DPCCHFBI
N FBI bitsTFCI
N TFCI bits
T slot = 2560 chips, N data = 10*2 k bits (k=0..6)
Uplink Dedicated Physical Channel
Data side and control side of uplink dedicated physical channel are I/Q multiplexing, which means DPDCH and DPCCH are I/Q code multiplexing in every radio frame.
For a connection, no matter how many the data channel is, there is but only one control channel. In every wireless connection, there can be 0, 1, or several uplink DPDCHs.
Uplink DPDCH is used to transmit DCH. Uplink DPCCH is used to transmit the control information
generated by L1. Control information of L1 contains : Known pilot bit that support channel estimation for related
detection TPC FBI An optional TFCI (TFCI transfers the real-time parameters
of different transmission channels that multiplexed on uplink DPDCH, and meanwhile, correspondent with data that will be transmit in the same frame 。 There is but only one uplink DPCCH in one connection for each layer.)
PRACH
PRACH Data channel and control channel of PRACH message are
also I/Q multiplexing, and the minimum spreading factor of its data channel is 32, with 4 time slot formats. While control channel has only one time slot format, with two domains: Pilot domain and TFCI domain.
Pilot
N pilot bits
Data
Ndata
bits
Slot #0 Slot #1 Slot #i Slot #14
T slot = 2560 chips, 10*2 k bits (k=0..3)
Message part radio frame T RACH = 10 ms
Data
ControlTFCI
N TFCI bits
Time slot structure of PRACH message
PRACH
PRACH PRACH is made up of prefix part and message part.
Following is the structure of random access emission. Random access emission contains one or more 4096-
chip-length prefixes and one message part of 10 or 20ms.
Message partPreamble
4096 chips 10 ms (one radio frame)
Preamble Preamble
Message partPreamble
4096 chips 20 ms (two radio frames)
Preamble Preamble
Structure of PRACH access emission
Downlink Physical Channel
Downlink physical channel contains dedicated downlink physical channel, one shared physical channel and 5 public control physical channels:
DPCH
SCH
CPICH
PICH
AICH
CCPCH
PDSCH
public control physical channels
Dedicated Downlink Physical Channel
DL DPCH DPCCH and DPDCH in downlink is time division
multiplexing, and DL DPCCH contains 3 domains :TPC domain, TFCI domain and PLIOT domain, the SF of DL DPDCH can be arranged from 4 to 512.
One radio frame, Tf = 10 ms
TPC
NTPC
bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot
= 2560 chips, 10*2 k bits (k=0..7)
Data2
Ndata2
bits
DPDCH
TFCI
NTFCI
bits
Pilot
Npilot
bits
Data1
Ndata1
bits
DPDCH DPCCH DPCCH
Frame structure of DL DPCH
Public Downlink Physical Channel
CPICH CPICH is a downlink physical channel with fixed
speed (30kbps , SF = 256), which is used to transmit predefined bit/symbol sequence. The function of CPICH is to assist UE to perform channel estimation for DCH. Modulation format of CPICH :
slot #1
Frame#i+1Frame#i
slot #14
A A A A A A A A A A A A A A A A A A A A A A A A
-A -A A A -A -A A A -A A -A -A A A -A -A A A -A -A A A -A -AAntenna 2
Antenna 1
slot #0
Frame Boundary
CPICH
Divided into P-CPICH and S-CPICH ; Non-encoded channel ; P-CPICH uses fixed spreading factor (Cch,256,0), has
fixed bit rate of 30kbit/s ; Each cell has but only one P-CPICH which uses the
primary scrambling code ; Used for the searching of cell primary scrambling code ; S-CPICH can use any of the SF=256 channel codes ; Used to assist UE to perform estimation for dedicated or
public channels ; P-CPICH provides phase and power benchmark for other
channels ; P-CPICH is mainly used for measurement and estimation
while handover, cell selection and cell reselection ; Adjust the transmission power of P-CPICH to balance the
load of different cells, determine cell coverage and cell respirations ;
P-CPICH broadcast to the whole cell ;
P-CCPCH
Public control physical channel is made up of P-CCPCH and S-CCPCH.
P-CCPCH is a downlink physical channel with fixed speed (30kbps , SF=256), which is to transmit BCH , and uses the primary scrambling code of the cell.
In the first 256chips of every time slot, CCPCH performs not emission. During this period, primary SCH and secondary SCH will be transmitted, but with no Pilot/TPC/TFC domain.
Data18 bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips , 20 bits
1 radio frame: Tf = 10 ms
(Tx OFF)
256 chips
Frame structure of P-CCPCH
S-CCPCH
S-CCPCH carries PCH and FACH, and has the following characteristics :
Each cell has at least one S-CCPCH with low transmission speed ;
The difference between P-CCPCHS-CCPCH is that, P-CCPCH only has fixed and pre-defined transmission format, but S-CCPCH can use TFCI to support more transmission formats.
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 20*2k bits (k=0..6)
Pilot Npilot bits
DataNdata bits
1 radio frame: Tf = 10 ms
TFCI NTFCI bits
Frame structure of S-CCPCH
SCH
SCH Divided into P-SCH and S-SCH ; Non-spreading and non-scrambling channel ; Downlink signal used for cell searching, to provide chip
synchronization, time slot synchronization and frame synchronization for users ;
The first 256 chips of each slot is used to transmit synchronization code.
PrimarySCH
SecondarySCH
256 chips
2560 chips
One 10 ms SCH radio frame
acsi,0
acp
acsi,1
acp
acsi,14
acp
Slot #0 Slot #1 Slot #14
SCH
P-SCH contains one 256chips-length modulation code and PSC
PSC is repeatedly transmitted in each slot to transfer the completely known sequence ;
PSC of every cell in the system is the same ; S-SCH repeatedly transmit a 15-sequence modulation code,
with length of each code is 256chips. SSC is transmitted spontaneously with SCH ;
SSC is identified with csi, k, and i=0 , 1 ,……, 63,which is the sequence number of scrambling code group; k=0 , 1 , 2……, which is the time slot number.
Each SSC is selected from one of the 16 different codes with length of 256 ;
SSC contains scrambling code group information, which can be used to determine the scrambling code group that being used in the cell..
PICH
PICH carries PI (Page Indication), whose SF=256, radio frame length is 10ms, contains 300bits, among which 288 bits carries PI, and the other12 bits are Tx Off.
PICH is always connected with one S-CCPCH, which is transmitting a PCH.
In each PICH frame, Np PI were transmitted {P0, …, PNp-1}, and here Np=18, 36, 72, or 144. If the Pli of one frame is set to 1, this means the UE that correspondent with Pii should adjust the frame that related to S-CCPCH.
b1b0
288 bits for paging indication12 bits (transmission
off)
One radio frame (10 ms)
b287 b288 b299
Frame structure of PICH
Content
Type of System Channel
Functions of the Channel
Physical Channel
Transportation Channel
Dedicated Transportation Channel
DCH (UL/DL) DCH is either an uplink or downlink channel. DCH
does not care what carried is actual user data or high-layer control information, as its content is invisible in physical layer.
DCH has the following characteristics : Fast power control ; Quick speed change frame by frame ; Soft handover
Public Transportation Channel - BCH
BCH (DL) BCH is a downlink transportation channel, which is used to
broadcast specific system or cell information, such as the random accessing code, accessing slot, or the transmission diversity method being used by other channels in the cell.
BCH is always transmitted in the whole cell with an independent transmission format. Data rate of BCH is low and fixed.
If UE cannot correctly decode BCH, it will not be able to register in the cell. Therefore, the transmission power of BCH is relatively higher, in order that all the UEs in the cell coverage can receive it.
BCH is carried by P-CCPCH
Functions of FACH
FACH (DL) FACH is a downlink public transportation channel,
which can carry either control information, or a small portion of group data.
FACH has the following characteristics : Open loop power control is used, but not closed loop. At least one FACH is transmitting to the whole cell at
low speed.. Physical channel that carries FACH is S-CCPCH
Functions of RACH
RACH (UL) RACH is an uplink transportation channel, carries the
control information transmitted by UE, such as connection request, registration, location update, and it also send a small portion of group data. No matter which position in the cell, base station should be able to receive RACH that carries control information.
RACH has the following characteristics : Uses open loop power control.
Physical channel that carries RACH is PRACH
Functions of PCH
PCH (DL) PCH is a downlink transportation channel that carries
related paging data. Based on different system configuration, same paging information can be sent to one single cell or even several hundred cells. The design of paging channel directly affects the power loss of UE when it is idle.
Physical channel that carries PCH is S-CCPCH