Pooria Varahram

Power Efficiency in Broadband Wireless Communications

Power Efficiency in Broadband Wireless Communications focuses on the improvement of power efficiency in wireless communication systems, especially of mobile devices. Reviewing cutting-edge techniques for conserving power and boosting power efficiency, the book examines various technologies and their impact on consumer devices. It considers each technology, first by introducing the main physical layer components in recent wireless communication systems along with their shortcomings, and then proposing solutions for overcoming these shortcomings.The book covers orthogonal frequency division multiplexing (OFDM) signal generation and formulation and examines the advantages and disadvantages of OFDM systems compared to alternative multiplexing. It introduces one of the main drawbacks of OFDM systems, peak-to-average power ratio (PAPR), and discusses several PAPR techniques. It also explains how to overcome the main drawbacks of real-world OFDM system applications. Considers power amplifier linearization for increasing power efficiency and reducing system costs and power dissipation Describes the implementation scenario of the most promising linearization technique, digital predistortion Presents some experimental demonstrations of digital predistortion when the device under test is in the loop Because the most costly device in a communication system that has a direct impact on power efficiency and power consumption is the power amplifier, the book details the behavior and characteristics of different classes of power amplifiers. Describing the evolution of the mobile cellular communication system, it details a cost-effective technique to help you increase power efficiency, reduce system costs, and prolong battery life in next generation mobile devices.

FPGA Implementation of Inverse Fast Fourier Transform in Orthogonal Frequency Division Multiplexing Systems

In modern communication systems, Orthogonal Frequency Division Multiplexing (OFDM) systems are used to transmit with higher data rate and avoid Inter Symbol Interference (ISI). The OFDM transmitter and receiver contain Inverse Fast Fourier Transform (IFFT) and Fast Fourier Transform (FFT), respectively. The IFFT block provides orthogonality between adjacent subcarriers. The orthogonality makes the signal frame relatively secure to the fading caused by natural multipath environment. As a result OFDM system has become very popular in modern telecommunication systems. Beside all the advantages of OFDM system, there is a main drawback of high Peak to Average Power Ratio (PAPR). There have been many approaches on reducing PAPR in time domain and frequency domain. Some of them work in time domain such as Partial Transmit Sequence Insertion (PTS) and some other methods perform in frequency domain such as Dummy Sequence Insertion (DSI) and Selected Mapping (SLM) methods (Bauml et al., 1996; Muller et al., 1997). Since according to (Baxley et al., 2007), the SLM method reduce PAPR with the least computational complexity and least additional modification requirements on the current technology, therefore most of recent researches have considered SLM based method modifications for their work. Most of these methods modified the OFDM transmitter in a way that multiple IFFT processors are required for implementation. This will increase the number of additions and multiplications that are needed for implementation.