1. WCDMA Introduction Code Division Multiple Access
Chia-Chi Yu

2. Outline History Multiple Access Technique Why CDMA? Spread Spectrum
How CDMA work? (simulation)
Problems in a CDMA system (simulation)

3. History 1949 C. Shannon develop basic ideas of CDMA
First GSM network
Development of IMT2000 and UMTS standards
Commercial operation of CDMA system (IS-95) in Hong Kong/Korea
The first meetings of the 3GPP
release ….
UMTS service will be world wide (?)

4. Introduction Applications Need Multiple Access!
Wireless communication is the way of the future
Applications
Mobile phones
Wireless LAN
Global positioning system
Need Multiple Access!

5. Multiple Access Techniques
TDMA Time Division Multiple Access
FDMA Frequency Division Multiple Access
CDMA Code Division Multiple Access
SDMA Space Division Multiple Access

6. Why CDMA ? Frequency limited
Bandwidth Efficiency Voice Activity ~40% Variable Spreading Factor

7. Spread Spectrum FHSS Frequency Hopping Spread Spectrum
THSS Trequency Hopping Spread Spectrum
DSSS Direct Sequence Spread Spectrum

8. DSSS Data is spread by multiplying a high rate spreading code
Receiver is de-spread by using the same code

11. Spectrum

12. Spectrum

13. Problems in a CDMA Channel
Near-Far Problem

14. CDMA system needs Power Control

15. Reference http://www.umtsworld.com http://www.3gpp.org
K. Riyyol,S WCDMA system
Qualcomm, Fundamentals of Wireless Communications & CDMA
A. J. Viterbi,Ed.,CDMA. Addison-Wesley 1995
S. G. Glisic Ed.,Adipative WCDMA. Wiley 2002