High peak to average power ratio (PAPR) is one of the major drawbacks in orthogonal frequency division multiplexing (OFDM) systems. In recently years, various methods have been proposed to reduce the PAPR performance. The selected mapping (SLM) scheme is perhaps the most popular one because it provides outstanding PAPR reduction performance. In addition, the subcarrier magnitude remains the same in the SLM scheme. However, there are two major shortcomings in the SLM scheme. First of all, it requires a number of inverse fast Fourier transforms (IFFTs) to produce candidate signals, dramatically increasing the computational complexity. In addition, side information has to be transmitted to the receiver to indicate the candidate signal that results in the best PAPR, leading to the decrease in bandwidth utilization. To overcome these two drawbacks, this thesis proposes a novel SLM scheme that does not need side information. The proposed scheme is based on a low complexity SLM scheme [C.-P. Li, S.-H. Wang, and C.-L. Wang, ¡§Novel low-complexity SLM schemes for PAPR reduction in OFDM systems,¡¨ IEEE Trans. Signal Process., vol. 58, no. 5, pp. 2916¡V2921, May 2010] in pilot-aided OFDM system. Simulation experiments are conducted to verify the performance of the proposed scheme. It is shown that the bit error rate (BER) performance of the proposed scheme is very similar to that of the traditional SLM scheme with perfect knowledge of the side information. Therefore, the proposed scheme not only has the advantages of low complexity and high bandwidth utilization, but also has a superior BER performance.

Selected mapping (SLM) schemes are commonly employed to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. It has been shown that the computational complexity of the traditional SLM scheme can be substantially reduced by adopting conversion vectors obtained by using the inverse fast Fourier transform (IFFT) of the phase rotation vector in place of the conventional IFFT operations [21]. Unfortunately, however, the elements of these phase rotation vectors of the conversion vectors in [21] do not generally have an equal magnitude, and thus a significant degradation in the bit error rate (BER) performance is incurred. This problem can be remedied by utilizing conversion vectors having the form of a perfect sequence. This paper presents three novel classes of perfect sequence, each of which comprises certain base vectors and their cyclic-shifted versions. Three novel low-complexity SLM schemes are then proposed based upon the unique structures of these perfect sequences. It is shown that while the PAPR performances of the proposed schemes are marginally poorer than that of the traditional SLM scheme, the three schemes achieve an identical BER performance and have a substantially lower computational complexity.

Selected mapping (SLM) is a well-known technique used to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. Although SLM scheme can reduce PAPR efficiently, the side information (SI) must be transmitted to the receiver to indicate the candidate signal that generates the OFDM signal with the lowest PAPR. Robust channel coding schemes are typically adopted to prevent erroneous decoding of SI, leading to the lower bandwidth efficiency. To reduce PAPR efficiently and avoid the bandwidth efficiency loss caused by the transmission of SI, two novel PAPR reduction methods are proposed in SFBC MIMO-OFDM systems with two transmitter antennas that employs the Alamouti coding. The candidate signals are constructed in the frequency-domain and time-domain in the first proposed scheme and the second proposed scheme, respectively. In addition, the orthogonality of the space frequency block code is preserved resulting in the data recovery and the corresponding SI can be easily obtained from the conventional Alamouti detection method for both transmission methods. Simulation results show that the BER performance of a SFBC MIMO-OFDM system with the proposed SI detection algorithm is very close to that of perfect SI detection if the extension factor is larger than 1.3.

Selected mapping (SLM) schemes are commonly employed to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. It has been shown that the computational complexity of the traditional SLM scheme can be substantially reduced by adopting conversion vectors obtained by using the inverse fast Fourier transform (IFFT) of the phase rotation vectors in place of the conventional IFFT operations. To ensure that the elements of these phase rotation vectors have an equal magnitude, conversion vectors should have the form of a perfect sequence. This study firstly presents three novel classes of perfect sequence, each of which comprises certain base vectors and their cyclically shifted versions. Three novel low-complexity SLM schemes are then proposed based upon the unique structures of these perfect sequences. It is shown that while the PAPR reduction performances of the proposed schemes are marginally poorer than that of the traditional SLM scheme, the three schemes achieve a substantially lower computational complexity. Since the three proposed PAPR reduction schemes cannot be utilized in the orthogonal frequency division multiple access (OFDMA) system. A low-complexity scheme for PAPR reduction in OFDMA uplink systems using either an interleaved or a sub-band sub-carrier assignment strategy is also proposed in the second part of this study. The proposed scheme requires just one IFFT operation. The PAPR reduction performance of the proposed scheme is only marginally poorer than that of the traditional SLM scheme. However, the proposed schemes have significantly lower computational complexities. Besides, multiple-input multiple-output (MIMO) OFDM systems with space-frequency block coding (SFBC) are well-known for their robust performance in time selective fading channels. However, SFBC MIMO-OFDM systems have a high computational complexity since the number of IFFTs required scales in direct proportion to the number of antennas at the transmitter. Furthermore, SFBC MIMO-OFDM systems have a high PAPR. Accordingly, a low-complexity PAPR reduction scheme for SFBC MIMO OFDM systems with the Alamouti encoding scheme is proposed in this study. Extending this scheme obtains two low-complexity transmitter architectures for SFBC MIMO-OFDM systems with a general encoding matrix and an arbitrary number of transmitter antennas. The proposed schemes achieve a significant reduction in computational complexity by fully exploiting the time-domain signal properties of the transmitted signal. In addition, a PAPR reduction scheme is presented based on the proposed transmitter schemes. It is shown that the PAPR reduction performance of the proposed scheme is almost as good as that of the traditional SLM scheme, but is achieved with a substantially lower computational complexity.