Waveform in 4G (OFDM) - Part II — Lesson 5

This lesson covers the waveforms for the 4th generation and beyond. It delves into the foundation of the waveform for 5G, which is essentially OFDM (Orthogonal Frequency Division Multiplexing). The lesson discusses the features, properties, and structures of OFDM, including its spectral efficiency, bandwidth saving, and orthogonality. It also explains how OFDM combats frequency selective fading, which occurs due to multi-path reflection. The lesson further explores the transmitter structure and the critical parameters of OFDM, such as sub-carrier bandwidth and guard interval. For instance, if you're using 64 QAM, you'll be sending 1024 multiplied by 6 bits simultaneously.

Video Highlights

00:18 - Introduction
01:22 - Orthogonality in OFDM and visualization of waveforms in the time domain
06:28 - Mathematical explanation and important aspects of OFDM
12:04 - Signal model and normalizing factor
16:56 - Transmitter structure of OFDM and symbol mapping
25:06 - Critical parameters in OFDM system design

Key Takeaways

- OFDM is the foundation for the waveform for 4G and 5G.
- OFDM offers high spectral efficiency and bandwidth saving.
- Orthogonality is a key feature of OFDM.
- OFDM effectively combats frequency selective fading.
- The transmitter structure of OFDM involves binary input bits, symbol mapping, and IFFT operation.
- Critical parameters of OFDM include sub-carrier bandwidth and guard interval.
- The symbol duration in OFDM must be smaller than the coherence time of the channel, and the sub-carrier spacing must be less than the coherence bandwidth.