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

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

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

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

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.

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

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

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

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.

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)

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”

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

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

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

Protocol Termination RRC RLC MAC RRC RLC Radio Network Controller Physical MAC RLC RRC Physical Radio Network Controller Iub Node B User Equipment Uu wray castle browser Internet Search http:/www.wraycastle.co.uk XXXXXXX XXX XXXXX XXXX XXXX XXX XX Figure 6

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

Common Pilot Signal Node B All UEs use the same common pilot Pilot wray castle browser Internet Search xxxxxxxxx XXXXXXX XXX XXXXX XXXX XXXX XXX XX wray castle browser Internet Search xxxxxxxxx XXXXXXX XXX XXXXX XXXX XXXX XXX XX Signalling/Traffic wray castle browser Internet Search xxxxxxxxx XXXXXXX XXX XXXXX XXXX XXXX XXX XX Node B wray castle browser Internet Search xxxxxxxxx XXXXXXX XXX XXXXX XXXX XXXX XXX XX All UEs use the same common pilot Figure 20

Channel Associated Pilot Pilot sequences Traffic/ Signalling Traffic/ Signalling wray castle browser Internet Search xxxxxxxxx XXXXXXX XXX XXXXX XXXX XXXX XXX XX wray castle browser Internet Search xxxxxxxxx XXXXXXX XXX XXXXX XXXX XXXX XXX XX Node B wray castle browser Internet Search xxxxxxxxx XXXXXXX XXX XXXXX XXXX XXXX XXX XX wray castle browser Internet Search xxxxxxxxx XXXXXXX XXX XXXXX XXXX XXXX XXX XX UEs Each channel carries its own pilot Figure 22

Three Sector Six Sector Sectorisation Three Sector Six Sector Figure 33

Frame Structure Superframe Duration 720 ms 1 2 71 1 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 40.96 s Figure 10

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

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

Resource Unit Frequency Code Timeslot Time 10 ms Radio Channel Code 2 3 4 5 6 7 10 ms 8 9 10 11 12 13 14 Radio Channel Code Figure 34

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

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 wray castle browser Internet Search http:/www.wraycastle.co.uk XXXXXXX XXX XXXXX XXXX XXXX XXX XX Node B Uu UE Figure 20

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

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

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

SSDT SRNC lub lub 1 2 lub Node B Node B 3 1 Node B DPDCCH/ DPCCH DPCCH only Node B wray castle browser Internet Search http:/www.wraycastle.co.uk XXXXXXX XXX XXXXX XXXX XXXX XXX XX DPCCH only 3 UE nominates Node B as Primary 1 Node B Figure 32

Intra- and Inter-Frequency Measurements UMTS Macro UMTS Macro wray castle browser Internet Search http:/www.wraycastle.co.uk XXXXXXX XXX XXXXX XXXX XXXX XXX XX F1 F1 UE F2 F1 UMTS Macro UMTS Macro UMTS Micro UMTS Macro Rake receiver is only able to see neighbour cells on the same frequency Figure 34

Transmit Diversity Node B UE TX 2 TX 1 Multipath set from antenna TX 2 FBI bit used in closed loop mode wray castle browser Internet Search http:/www.wraycastle.co.uk XXXXXXX XXX XXXXX XXXX XXXX XXX XX Node B UE Multipath set from antenna TX 1 Figure 40

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