Adaptive pre-distortion and peak-to-average power ratio reduction in OFDM wireless communications

Orthogonal Frequency Division Multiplexing (OFDM) is a prime modulation choice for the emerging telecommunication standards by virtue of its well-known desirable attributes. However, its high Peak-to-Average-Power Ratio (PAPR) seriously limits the power efficiency of the transmitter's High Power Amplifier (HPA). This is because PAPR forces the HPA to operate beyond its linear range with a consequent nonlinear distortion in the transmitted signal. This distortion is viewed as a major impediment to progress by the RF system design community. In this dissertation, we present two different approaches to solve this problem. As a first approach, we provide a new mixed computational/analytical approach for adaptive pre-compensation of this nonlinear distortion for the cases in which the HPA is a Traveling Wave Tube Amplifier (TWTA) and Solid State Power Amplifier (SSPA), and thus increase the linear dynamic range up to the saturation region of the HPA. However, these pre-distortion techniques only work in the limited range that extends up to the saturation region of the HPA. In order to solve this problem, we develop, as a second complementary approach, several PAPR reduction techniques which pull down the PAPR of the OFDM signal to an acceptable range. These new techniques include: (1) an enhanced version (denoted by EIF-PTS) of the Cimini/Sollenberger Iterative Flipping procedure for implementation of the Muller/Huber Partial Transmit Sequence (PTS) algorithm; (2) a decision-oriented tree-structured modification (denoted by T-PTS) of the PTS algorithm, which seeks the best complexity/performance trade-off in the implementation of the resulting simplified PTS algorithm; (3) a combination of clipping and Selective Mapping (SLM) techniques for flat and frequency selective fading channels; and (4) and an extension of some of the underlying PAPR reduction concepts to MIMO (Multiple Input Multiple Output) OFDM-based wireless communication systems. The validity of all of the above techniques is established by computer simulations and analysis.