Now-a-days, wireless communications gets more attention from the Communication industry and provide quality information transfer between portable devices.Applications like Autonomous sensor networks, Multimedia, Videoconferencing, and Distance learning and Internet enabled cell phone are developed by 3G system. Also Long Term Evolution (LTE) is going to increase the data rate, throughput, decrease latency, etc, for the above applications and also to bring lot of applications. Our primary aim of this book is to minimize the error probability of a LTE system and to bring the spectrum efficiency through a process known as adaptive modulation and coding rate. Chapter 1 introduces the features of fourth generation communication systems. Chapter 2 discusses about Literature review of OFDM, CDMA LTE systems. Chapter 3 analyses the OFDM in AWGN channel for different modulation techniques. Results are discussed in Chapter 4. Chapter 5 brings out the conclusion. This monograph is useful for all Engineering undergraduate, graduates students and practicing engineers.