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

2. 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

3. Air Interface Access Stratum
Control Plane Signalling
User Plane Information L3
Radio Resource
Control (RRC)
Radio Link
Control (RLC) L2
Logical
Channels
Medium Access
Control (MAC)
Transport
Channels L1
Physical Layer
Figure 5

4. UE to UTRAN protocol stack (air interface layers)
The radio interface is divided into 3 layers:
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).
MAC: responsible for multiplexing data from multiple applications onto physical channels in preparation for over-the-air transmission.
RLC: segments the data streams into frames that are small enough to be transmitted over the radio link

5. 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.

6. Transport Channels Two types
Dedicated transport channels (DCH): Single User
Downlink shared channel (DSCH)
DCH
2. Common transport channels (CCH): Group of Users
Broadcast channel (BCH)
Forward access channel (FACH)
Paging channels (PCH)
Random access channel (RACH)
Uplink common packet channel (CPCH)
Only I,ii,III and iv are needed for basic network

7. Physical Channels Common control channel: 2. Dedicated channel:
P-CCPCH :
S-CCPCH
P-SCH
S-SCH
CPICH
AICH
PICH
PDSCH
PRACH: UL
PCPCH: UL
CD/CA-ICH.
2. Dedicated channel:
DPDCH: UL
DPCCH: UL

8. 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

9. UMTS Logical-Transport-Physical Channel Mapping
Channels
MAC
FACH
DSCH
DCH
BCCH
PCCH
DCCH
CCCH
CTCH
DTCH
BCH
PCH
Physical Layer
CPCH
RACH
P-CCPCH
PDSCH
S-CCPCH
DPDCH
DPCH
DPCCH
SCH
CSICH
CPICH
AICH
CD/
CA-ICH
AP-
PICH
Transport
Layer 2
Layer 1
PRACH
PCPCH
Physical
Node B RF Modulator/Demodulator
© Dr Maaruf Ali
NB. The bubbles are SAPs, Service Access Points, logical software gateways between the different layers
Some channels only originate from and in the Physical Layer, e.g. CSICH etc.

10. 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
UE Tx preamble to BTS
If no ack, then
UE TX with higher power
Repeat III until ack is rcv
Then, UE TX PRACH msg at this power level
Msg (Data + contr)

11. 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”

12. P-CCPCH: Common control physical channel (CCPCH) S-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

13. 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

14. Paging indicator channel (PICH) Acquisition indicator channel (AICH)
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

15. Protocol Termination RRC RLC MAC RRC RLC Radio Network Controller
Physical
MAC
RLC
RRC
Physical
Radio
Network
Controller
Iub
Node B
User
Equipment Uu
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Figure 6

16. Channel Type Switching Access Class Selection
Functions of MAC
Logical to Transport
Channel Mapping
Selection of
Transport Format
Priority
Handling
MAC Functions
Identification of
UEs on Common
Transport Channels
Multiplexing of
PDUs into Transport
Blocks
Traffic Volume
Monitoring
Dynamic Transport
Channel Type Switching
Access Class Selection
for RACH and CPCH
Ciphering for TrM RLC
Figure 12

17. Common Pilot Signal Node B All UEs use the same common pilot Pilot
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Signalling/Traffic
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Node B
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All UEs
use the same
common pilot
Figure 20

18. Channel Associated Pilot
Pilot sequences
Traffic/
Signalling
Traffic/
Signalling
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Node B
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UEs
Each channel
carries its own pilot
Figure 22

19. Three Sector Six Sector
Sectorisation
Three Sector
Six Sector
Figure 33

20. Frame Structure Superframe Duration 720 ms 1 2 711 2 71
Radio Frame Duration 10 ms 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Timeslot Duration
666.7 µs
2,560 chips 2 4
4,094
Hyperframe Duration s
Figure 10

21. Single Switching Point Multiple Switching Point
TDD Switching Points
Single Switching Point DL UL DL 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Frame 10 ms
Multiple Switching Point DL UL DL UL DL UL DL UL DL UL DL UL DL UL DL 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Figure 32

22. Variable Spreading or Variable Codes
High Bit Rate
Low Spreading
Factor
Low Bit Rate
High Spreading
Factor
Code 1
Code 2
Code 3
Code 4
Code 5
Code 6
TS N–1
TS N
TS N+1
TS N+2
666.7 µs
Figure 33

23. Resource Unit Frequency Code Timeslot Time 10 ms Radio Channel Code2 3 4 5 6 7
10 ms 8 9 10 11 12 13 14
Radio
Channel
Code
Figure 34

24. Burst Types Timeslots 666.7 µs Data symbols 61,122,244,488,976
976 chips
Data symbols
61,122,244,488,976
976 chips GP 96
chips
Midamble
512 chips
BURST TYPE 2
Data symbols
69,138,276,552,1104
1104 chips
Data symbols
69,138,276,552,1104
1104 chips GP 96
chips
Midamble
256 chips
Figure 36

25. Measurement Control Measurement Control Iub RRC RNC Measurement type
Measurement identity number
Measurement command
Measurement objects
Measurement quantity
Reporting quantities
Measurement reporting criteria
Reporting mode
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Node B Uu UE
Figure 20

26. Requirement for Synchronisation
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
Figure 22

27. UL I/Q Multiplexed in the UL DPDCH Data TFCI FBI DPCCH Pilot TCP
Pilot : For channel assessment
Transport format combination identifier: Combine several TF from transport channels to form TFC block
Feedback information indicator: Channel diversity
Transmitter power control: Power control

28. DL Time Multiplexed in the DL Data TPC TFCI Data Pilot DPCCH DPDCH

29. SSDT SRNC lub lub 1 2 lub Node B Node B 3 1 Node B DPDCCH/ DPCCH
DPCCH only
Node B
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DPCCH only 3
UE nominates
Node B
as Primary 1
Node B
Figure 32

30. Intra- and Inter-Frequency Measurements
UMTS Macro
UMTS Macro
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UMTS Macro
UMTS Macro
UMTS Micro
UMTS Macro
Rake receiver is only able to see neighbour
cells on the same frequency
Figure 34

32. Transmit Diversity Node B UE TX 2 TX 1 Multipath set from antenna TX 2
FBI bit used in closed loop mode
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Node B UE
Multipath set from
antenna TX 1
Figure 40

33. Any Questions ?