OFDM Concepts for Future Communication Systems School of

Outline of Course n n n Ch 1 Ch 2 Ch 3 Ch 4

Chapter 1: Introduction 1. 1 Radio Channel Behavior n 1. 2 Basics of the

1. 1 Radio Channel Behavior n Multi-path propagation Figure 1. 1: Multi-path propagation scenario

Time-variant n Frequency-selective behavior n Figure 1. 2: Frequency-selective and time-variant radio channel transfer

Two important system parameters The maximum multipath delay n The maximum Doppler frequency n

OFDM feature and superiority n Relationships among a single OFDM symbol duration , The

OFDM can effciently deal with all these ISI effects, n the OFDM transmission technique

1. 2 Basics of the OFDM Transmission Technique n n The general idea of

Figure 1. 3: OFDM spectrum which consists of N equidistant sinc functions

Figure 1. 4 : OFDM system structure in a block diagram

1. 3 OFDM Combined with Multiple Access Schemes Figure 1. 5: OFDM transmission technique

n OFDM-FDMA n OFDM-TDMA n OFDM-CDMA n OFDM-SDMA

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OFDM Concepts for Future Communication Systems School of Info. Sci. & Eng. Shandong Univ.

Outline of Course n n n Ch 1 Ch 2 Ch 3 Ch 4 Introduction Channel Modeling Link-Level Aspects System Level Aspects for Single Cell Scenarios Ch 5 System Level Aspects for Multiple Cell Scenarios Ch 6 OFDM/DMT for Wireline Communications

Chapter 1: Introduction 1. 1 Radio Channel Behavior n 1. 2 Basics of the OFDM Transmission Technique n 1. 3 OFDM Combined with Multiple Access Schemes n

1. 1 Radio Channel Behavior n Multi-path propagation Figure 1. 1: Multi-path propagation scenario

Time-variant n Frequency-selective behavior n Figure 1. 2: Frequency-selective and time-variant radio channel transfer function

Two important system parameters The maximum multipath delay n The maximum Doppler frequency n The coherence time bandwidth : and the coherence

OFDM feature and superiority n Relationships among a single OFDM symbol duration , The coherence time , the coherence bandwidth , and the distance between two adjacent subcarriers is

OFDM can effciently deal with all these ISI effects, n the OFDM transmission technique needs much less computational complexity in the equalization process inside each receiver. n

1. 2 Basics of the OFDM Transmission Technique n n The general idea of the OFDM transmission technique is to split the total available bandwidth B into many narrowband sub-channels at equidistant frequencies. The sub-channel spectra overlap each other but the subcarrier signals are still orthogonal. The single high-rate data stream is subdivided into many lowrate data streams for the sub-channels. Each sub-channel is modulated individually and will be transmitted simultaneously in a superimposed and parallel form.

Figure 1. 3: OFDM spectrum which consists of N equidistant sinc functions

Figure 1. 4 : OFDM system structure in a block diagram

1. 3 OFDM Combined with Multiple Access Schemes Figure 1. 5: OFDM transmission technique and some multiple access schemes

n OFDM-FDMA n OFDM-TDMA n OFDM-CDMA n OFDM-SDMA