Viettel_Introduction to WCDMA RAN

WCDMA Wireless Technology Introduction: 

WCDMA Wireless Technology Introduction Viettel Technologies Hoang Duc Giang R&D Department

Contents: 

Contents WCDMA Introduction Multiple Access Technologies WCDMA Key Technical Specifications Overview Architecture Overview Code Types in WCDMA Modulation method Handover in WCDMA WCDMA Transmitter

Introduction to WCDMA: 

Introduction to WCDMA WCDMA stands for W ideband C ode D ivision M ultiple A ccess WCDMA is a radio access technology used for UMTS – a 3G system WCDMA is standardized by 3GPP ( 3G P roject P artner) WCDMA covers both FDD and TDD modes Viettel Technologies

3G standardization: 

3G standardization 2 different standards bodies developed and proposed 2 families of standards: 3GPP2 with CDMA2000 family of standards 3GPP with WCDMA (UMTS) family of standards Viettel Technologies

Main WCDMA milestones: 

Main WCDMA milestones 01/1998, ETSI chosen WCDMA as a standard for the next mobile system generation-3G that inherited in 3GPP The first full set off WCDMA is released in 1999 called R99 Several releases were introduced like as R5 (in 2005), R6 (in 2007) Viettel Technologies

Multiple Access Technologies(1): 

Multiple Access Technologies(1) TDMA -Time Division Multiple Access: Each user has a unique time slot, channels separate by time FDMA -Frequency Division Multiple Access: Frequency used to separate channels WCDMA -Code Division Multiple Access: All users work on the same frequency, at the same time but different codes. Codes are used to separates channels Viettel Technologies

Multiple Access Technologies(2): 

Multiple Access Technologies(2) Viettel Technologies

Key WCDMA specifications (1) : 

Key WCDMA specifications (1) Direct-Sequence Code Division Multiple Access (DS-CDMA) system The chip rate of 3.84Mcps leads to a carrier bandwidth of approximately 5 MHz WCDMA supports highly variable user data rates WCDMA supports two basic modes of operation: Frequency Division Duplex (FDD) and Time Division Duplex (TDD) Viettel Technologies

Key WCDMA specifications (2): 

Key WCDMA specifications (2) WCDMA supports the operation of asynchronous base stations –no need GPS WCDMA employs coherent detection on uplink and downlink based on the use of pilot symbols or common pilot The WCDMA air interface has been crafted in such a way that advanced CDMA receiver concepts Viettel Technologies

Key WCDMA specifications (3): 

Key WCDMA specifications (3) WCDMA is designed to be deployed in conjunction with GSM Viettel Technologies

UMTS/WCDMA Architecture Overview: 

UMTS/WCDMA Architecture Overview Radio part(RNS) : UEs Node Bs RNCs Core Part: MSC/VLRs SGSN/VLRs Viettel Technologies

WCDMA Code types: 

WCDMA Code types Two types: Channelization codes (Orthogonal codes, OVSF codes, spreading codes, Walsh codes) Scrambling codes ( PN codes, Long codes, SSMAC) Viettel Technologies

Channelization codes properties : 

Channelization codes properties The codes in the same spreading factor ( SF ) are orthogonal to each others Determine user data rate: the higher SF, the lower data rate and Viettel Technologies Channelization code tree SF= 2 SF= 4 SF=1

PowerPoint Presentation: 

Usage Uplink: Separation of physical data (DPDCH) and control channels (DPCCH) from same terminal Downlink: Separation of downlink connections to different users within one cell Length 4–256 chips (1.0–66.7µs) Downlink also 512 chips Number of codes Number of codes under one scrambling code = spreading factor Code family OVSF Spreading I ncreases transmission bandwidth Viettel Technologies Channelisation code

Scrambling code properties (Downlink): 

Scrambling code properties ( Downlink ) Primary Scrambling Code (PSC): Value from 1 to 512 (downlink) A unique PSC is assigned to each cell Each scrambling code has low cross-correlation with any other scrambling code, regardless of the timing offset between the two scrambling code There are 7680 available Secondary Scrambling Code (SSC) when no more channelization codes Viettel Technologies

Scrambling code properties (Uplink): 

Scrambling code properties ( Uplink ) Each UE is assigned one of about 17 million PNs codes Used for user separation Viettel Technologies

PowerPoint Presentation: 

Usage Uplink: Separation of terminal Downlink: Separation of sectors (cells) Length Uplink: (1) 10 ms = 38 400 chips or (2) 66.7µs = 256 chips. Option (2) can be used with advanced base station receivers Downlink: 10 ms = 38 400 chips Number of codes Uplink: several million Downlink: 512 Code family Long 10 ms code: Gold code Short code: Extended S(2) code family Spreading No, does not affect transmission bandwidth Viettel Technologies Scrambling code

Cellular CDMA (PN codes and Orthogonal codes): 

Cellular CDMA (PN codes and Orthogonal codes) Viettel Technologies

Handover Types in WCDMA(1): 

Handover Types in WCDMA(1) Soft Handover More than one connections in the same frequency, the same UMTS but different Node Bs Softer Handover Two connections in the same frequency, the same UMTS but different cells in the same Node B Viettel Technologies

Handover Types in WCDMA(2): 

Handover Types in WCDMA(2) Hard Handover Inter Frequency in the same UMTS Inter RAT: Between UMTS and GSM or TD-SCDMA… Viettel Technologies

WCDMA transmitters(1): 

WCDMA transmitters(1) Viettel Technologies

WCDMA transmitters(2): 

WCDMA transmitters(2) Codes are used to separate different data channels User data are simply added together in a linear summation device The power is the shared resource, so each channel is weighted to ensure the combined result is a fixed level The composite signal is multiplied by PN code to separate different transmitters Viettel Technologies

Modulation in WCDMA: 

Modulation in WCDMA QPSK modulation 1symbol represents 2 bits Modulation efficiency =2bits/symbol Viettel Technologies

QPSK-Modulation: 

QPSK-Modulation Input data stream is converted from serial to independent parallel I and Q branch Viettel Technologies

QPSK-De-modulation: 

QPSK-De-modulation Original signal recovered from two components by local oscillator, phase shifter and two mixers Viettel Technologies

PowerPoint Presentation: 

Thanks For Your Attention! Viettel Technologies

Questions (1): 

Questions (1) Q1. What is WCDMA? Why call ‘Wideband”? Q2. What standard body is responsible for UMTS/WCDMA specifications? Q3. Which codes (spreading or scrambling) are used to separate users on UL in WCDMA? Q4. As the Spreading Factor increases, does the data rate increase or decrease? Viettel Technologies

Questions (2): 

Questions (2) Q4. What modulation method is used in WCDMA –R99? Q5. How many types of handover are there in WCDMA? Q6. In WCDMA, how many scrambling codes are there in the downlink? Q7. In WCDMA, which code make transmission bandwidth increase? Viettel Technologies

Questions (3): 

Questions (3) Q8. What is the usage of spreading codes in downlink? Q9. What is the usage of spreading codes in uplink? Q10. What is the usage of scrambling codes in downlink? Q11. What is the usage of scrambling codes in uplink? Viettel Technologies