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Lucent Technologies Proprietary 1
W-CDMA Air Interface Fundamentals
Prepared By: Rupy Sikka
E-mail: [email protected]
Ph: +1 (630) 2240 192
Lucent Technologies Proprietary 2
OBJECTIVES
• Describe the requirements and drivers behinds the W-CDMA Air Interface.
• List the layers UMTS radio Air Interface protocol stack and the responsibility of each layer
• UMTS Channel Types and their purpose• Gain understanding of UMTS Modes: FDD and TDD• Protection in UMTS:Describe the forward error correction
employed by UMTS Air interface• Channelizations in UMTS• Source Identification: Scrambling codes/Gold Codes
Lucent Technologies Proprietary 3
W-CDMA OVERVIEW-ARCHITECTURE
RNC
Iub Iub
RNS
Uu Uu
Node B Node B
Iu-CS
3G-MSC SGSN
Iu-PS
GGSN PDN/InternetPSTN
Core Network
UTRAN
Lucent Technologies Proprietary 4
WCDMA OVERVIEW-UTRAN FUNCTIONS
• UTRAN Functions:– Overall System Access Control
– Security and Privacy
– Handover
– Radio Resource Management and Control
• RNC Functions:
– Intra UTRAN Handover
– Frame Synchronization
– Radio Resource Management: Radio Bearer Control
– Outer Loop Power Control
– Radio Resource Allocation
Lucent Technologies Proprietary 5
UTRAN FUNCTIONS
• Node B
– Termination of Iub Interface from RNC
– Conduct Radio Environment Survey (BER estimate, Rx signal strength etc..)
– Inner Loop Power Control
– Open loop power control
– Radio Channel Coding/decoding
– Mapping of coded composite transport channels on physical channel
– modulation and spreading/dispreading of physical channels
– Frequency and time Synchronization
– Error detection on transport channels and indication to higher layers
– Termination of Uu interface from the UE etc..
Lucent Technologies Proprietary 14
RADIO PROTOCOL STACK FUNCTIONS
• Physical Layer Functions (Layer-1)– Forward error correction, coding,interleaving– Measurements– Soft handover execution– Multiplexing/mapping of services on dedicated physical code channels– Modulation, spreading, demodulation, dispreading of physical channels– Frequency and time synchronization– Fast closed-loop power control– RF processing
• MAC Layer Function (Layer-2L)– Selection of appropriate transport format– Service multiplexing on RACH, FACH and dedicated channels– Scheduling– Access resolution on RACH– Contention resolution on RACH etc..
Lucent Technologies Proprietary 15
RADIO PROTOCOL STACK FUNCTIONS
• RLC Functions (Layer-2U):– Segmentation and assembly– Transfer of user data– Error correction through retransmission optimized for physical layer– Sequence integrity– Flow control
• PDCP Function (Layer-2U)– Service specific. Exists only in the User Plane and only for services from PS
domain. Contains compression methods needed for better spectral efficiency
• RRC Functions:– Broadcast of system information– Radio Resource handling– Control of requested QOS – UE measurements reporting and control of the reporting
Lucent Technologies Proprietary 17
OBJECTIVE
• UMTS W-CDMA Channels Structure
• Map channels to radio interface protocol stack
Lucent Technologies Proprietary 22
LOGICAL CHANNELS
Traffic Channels - Dedicated Traffic Channel (DTCH)- Common Traffic Channel (CTCH)
Control Channels - Dedicated Control Channel (DCCH)- Common Control Channel (CCCH)- Broadcast Control Channel (BCCH)- Paging Control Channel (PCCH)
Lucent Technologies Proprietary 23
TRANSPORT CHANNELS
Dedicated Channels - Dedicated Channel (DCH)
Common Channels - Random Access Channel (RACH) - Forward Access Channel (FACH) - Broadcast Channel (BCH) - Paging Channel (PCH)
- Common Packet Channel (CPCH) - Downlink Shared Channel (DSCH)
(CPCH & DSCH are optional channels and
are not supported in Lucent’s initial release)
Lucent Technologies Proprietary 24
PHYSICAL CHANNELS
• Uplink– Dedicated Channels
• Dedicated Physical Data Channel (DPDCH)• Dedicated Physical Control Channel (DPCCH)
– Common Channels• Physical Random Access Channel (PRACH)• Physical Common Packet Channel (PCPCH)
• Downlink– Dedicated Channel
• Dedicated Physical Channel (DPCH)– Common Channels
• Common Pilot Channel (CPICH)• Primary Common Control Physical Channel (P-CCPCH)• Secondary Common Control Physical Channel(S-CCPCH)• Synchronization Channel (SCH)• Physical Downlink Shared Channel (PDSCH)• Acquisition Indication Channel (AICH)• Page Indication Channel (PICH)
Lucent Technologies Proprietary 25
UMTS RADIO CHANNEL MAPPING
BCCH
PCCH
CCCH
DCCH
DTCH
CTCH
BCH
CPCH
DSCH
DCH
RACH
FACH
PCH
P-CCPCH
S-CCPCH
P-CPICH
PRACH
DPDCH
DPCCH
PDSCH
PICH
P-SCH
S-SCH
AICH
S-CPICH
PCPCH
Logical Channels Transport Channels Physical Channels
DPCHKey: Uplink
Downlink
Bidirectional
Data Transfer
Association
Control Ch
Traffic Ch
Common Ch (no FPC)
Common Ch (FPC)
Dedicated Ch (FPC)
Info Channels
Assoc Channels
Fixed Channels
Lucent Technologies Proprietary 28
W-CDMA PHYSICAL LAYER PROCESSING
• Protecting Data/User Information:– Forward error correction mechanism are applied to allow adding information to the
data streams enabling receiver to correct the errors during decoding process.– Achieved by digital coding techniques such as:
• Convolution coding: – Can use ½ or 1/3 rating coders. – Used for services 19.2Kbps or less e.g. Voice
• Turbo Coding: – Uses two convolution coder working in parallel.– Turbo coder defined as 1/3 rate. – Additional processing relative to convolution coder.– Added delay due to additional processing makes it perfect for non real-time
services such as WEB browsing. – Used for services data rate 19.2Kbps or higher.
• Interleaving:– Reorder original coded data streams to help error correction
Lucent Technologies Proprietary 29
W-CDMA PHYSICAL LAYER PROCESSING
• Channel Separation– Uses OVSF codes
– OVSF is applied to achieve 3.84Mcps fixed channel rate
• Source Identification– Scrambling codes are used for
Node-B and UE identification
– The set of scrambling codes are known as Gold codes
– 2-24 Gold codes for UL (UE)
– 512 are assigned for DL(Node-B)