CDMA and OFDM: The Radio Interface

Course 077

Summary:

This five-day course provides participants with an introduction to CDMA and OFDM. CDMA is the physical interface of the IS-95 and IMT2000 3G Wideband CDMA systems, and OFDM is the radio interface of the new IEEE 802.11a and 802.16 systems. We will place special emphasis on both CDMA and OFDM (and OFDMA). Cellular concepts and fading channels are covered, as well as the basic building blocks of both CDMA and OFDM systems. The worldwide status of current and future CDMA and OFDM systems are discussed in detail.

Learning Objectives:

Upon completing the course, the participant will be able to:

• Describe the present third generation IMT2000 WCDMA physical interface proposals (3GPP, CDMA2000).
• Discuss the IS-95 physical interface.
• Explain CDMA concepts including the near-far problem, power control, RAKE receiver, sectorization, voice activity factor, space diversity, soft-handoff, Walsh functions, pseudo-random sequences.
• Describe OFDM and its DMT implementation
• Discuss the radio interface of IEEE802.11a and 802.16 LAN systems
• Elaborate on the basic building blocks of cellular systems: modulation, coding, equalization, diversity.
• State the cellular concept

Target Audience:

Engineers interested in the physical interface of current and future CDMA and OFDM systems will benefit from this introductory course. Participants should have familiarity with the Fourier transform, probability theory, and power spectral density as provided by a standard undergraduate EE studies.

Outline:

Day One

Mobile Wireless Systems
• First and second generation • Third generation : IMT2000 WCDMA proposals such as FDM, TDD, FDD • The cellular concept • Frequency reuse • FDMA • TDMA • CDMA
The Mobile Channel
• Raleigh fading • Delay spread-frequency • Selective fading • Doppler effect • Diversity techniques
Modulation and Detection
• Nyquist signaling • Linear equalization • Signal space

Day Two

Modulation and Detection (cont'd.)
• Optimum detection • Walsh functions • CDMA modulations : BPSK, QPSK, SQPSK, MPSK, QAM • Performance in Raleigh fading channels • Antenna and space diveristy
Information Theory
• Why code? Introduction to coding

Day Three

Information Theory (cont'd)
• A brief review of important results • Shannon Capacity • Why code? • Multitone concept • Discrete Multitone (DMT) implementation
OFDM - Orthogonal Frequency Division Modulation
• Adaptive modulation and coding techniques • Radio interface of IEEE 802.11a, IEEE 802.16 • OFDM as a multiple access technique • OFDM combined with BLAST

Day Four

Coding
• Block coding (Reed Solomon code) • Interleaving • Viterbi algorithm • Trellis coding • Convolutional coding • Concatenated coding • Turbo-coding • Performance over Rayleigh fading channels • Information theory bounds for fading channels • Space-Time coding

Day Five

The CDMA Concept
• CDMA detectability performance • Pseudo-random sequences • RAKE receiver • Power control • VAF, soft degradation • Intercell interference effects • Sectorization • Soft-handoff • Space diversity
IS-95
• Uplink and downlink • Channelization and spreading sequences
IMT2000 WCDMA Third-Generation
• Present proposals : 3GPP, CDMA2000 (FDM, TDD, FDD) • Family of proposals for the physical interface of the IMT-2000 third generation systems
Comparison of Different CDMA Systems
• Alamouti coding

Subject Areas Covered

CDMA/WCDMA 3G/4G LTE
Modulation Techniques
OFDM and OFDMA Technology

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