Analysing Transmitter Oriented Iterative PAPR Reduction Techniques In OFDM Systems

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Fehér Gábor
Department of Broadband Infocommunications and Electromagnetic Theory

As bandwidth is becoming one of the most valuable resources in today's telecommunication, the need for modulations with a greater spectral efficiency increases. Such highly efficient modulation technique is Orthogonal Frequency Division Multiplexing (OFDM). OFDM has become a key communication systems technology. Since the OFDM symbols are generated via Inverse Fast Fourier Transform (IFFT), the time domain signal is the sum of many narrowband signals. According to the Central Limit Theorem the sum of large number of independent random variables with similar distribution will be Gaussian distributed. Therefore the signal has high peak values and high Peak To Average Power Ratio (PAPR).

The large PAPR increases the complexity of the analog-to-digital and digital-to-analog converters and a reduces efficiency of the RF power amplifier, thus PAPR has been identified as the major practical problem of OFDM. Signals with high PAPR would require a wide range of dynamic linearity from the analog circuits, which usually results in expensive devices and high power consumption with lower efficiency.

This Thesis focuses on transmitter oriented iterative PAPR reduction techniques. It begins with a description of the OFDM systems in general and formulates the high PAPR problem. The document contains an analysis of the efficiency of Active Constellation Extension (ACE) and Tone Reservation (TR) the most commonly used PAPR reduction methods, and describes an OFDM modulator that is designed to validate the results provided by ACE and TR.


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