Yajun Kou

A New Peak-to-Average Power-Ratio Reduction Algorithm for OFDM Systems via Constellation Extension

Peak-to-average power-ratio (PAPR) reduction for OFDM systems is investigated in a probabilistic framework. A new constellation extension technique is developed whereby the data for each subcarrier are represented either by points in the original constellation or by extended points. An optimal representation of the OFDM signal is achieved by using a de-randomization algorithm where the conditional probability involved is handled by using the Chernoff bound and the evaluation of the many hyperbolic cosine functions involved is replaced by a tight upper bound for these functions. The proposed algorithm can be used by itself or be combined with a selective rotation technique described in the paper and with other known algorithms such as the coordinate descent optimization and selective mapping algorithms to achieve further performance enhancements at the cost of a slight increase in the computational complexity. When compared with other existing PAPR-reduction algorithms, the enhanced algorithm offers improved PAPR-reduction performance and improved computational complexity although, the transmit power is increased somewhat

New peak-to-average power-ratio reduction algorithms for OFDM systems using constellation extension

New peak-to-average power-ratio reduction (PAPR) algorithms for orthogonal frequency-division multiplexing systems are investigated in a probabilistic framework. Specifically, two de-randomization algorithms for PAPR reduction are developed by applying the so-called conditional probability method. Our simulations demonstrate that the proposed algorithms outperform several existing algorithms and the computational complexity of the proposed algorithms is found to be significantly less than that of existing algorithms.

Application of space-time block coding in DS-CDMA communication systems

The basic theory of space-time block coding (STBC) is reviewed and its potential applications in DS-CDMA communication systems in a number of system configurations are investigated. Simulation results show that significant bit-error-rate (BER) performance improvement can be achieved by integrating STBC into DS-CDMA systems.

Application of sphere decoding in intercarrier-interference reduction for OFDM systems

While fast variations of wireless channel characteristics cause intercarrier interference (ICI) in orthogonal frequency-division multiplexing systems, they also introduce frequency diversity, which can be exploited to improve the demodulation performance. An ICl-reduction algorithm is proposed based on a sphere decoding (SD) algorithm. By considering channel information, a new search strategy is developed to reduce the computational complexity of the SD algorithm. Design examples are presented which demonstrate that the proposed algorithm outperforms several existing algorithms in terms of BER performance.

New peak-to-average power-ratio reduction algorithms for multicarrier communications

Two new peak-to-average power-ratio (PAPR) reduction algorithms for passband multicarrier systems are deduced by applying optimization to modulation constellations. The associated optimization problem can be solved by two different methods, namely, the second-order cone programming method and the least-pth unconstrained optimization method. Our simulations show that the proposed PAPR-reduction algorithms outperform several existing algorithms.

An iterative intercarrier-interference reduction algorithm for OFDM systems

A low-complexity iterative algorithm is proposed for intercarrier-interference reduction in orthogonal frequency-division multiplexing systems. Design examples are presented which demonstrate that the proposed algorithm outperforms several existing algorithms in terms of bit-error-rate performance and computational complexity.

Peak-to-average power-ratio reduction algorithms for OFDM systems via constellation extension

New peak-to-average power-ratio (PAPR) reduction algorithms for orthogonal frequency-division multiplexing (OFDM) systems are investigated in a probabilistic framework. Specifically, derandomization algorithms based on the Chernoff bound for PAPR reduction are developed by applying the so-called conditional probability method. Our simulations demonstrate that the proposed algorithms outperform several existing algorithms and the computational complexity of the proposed algorithms is found to be significantly less than that of existing algorithms.

Peak-to-average power-ratio reduction via channel hopping for downlink CDMA systems

The effect of Walsh code assignment and data correlation on the peak-to-average power-ratio (PAPR) of a downlink CDMA signal is investigated. A PAPR-reduction algorithm is proposed using data reversal and channel hopping. Simulations show that improved PAPR reduction and bit-error rate performance can be achieved by the proposed algorithm.

An improved peak-to-average-power ratio reduction algorithm for multicarrier communications

An improved peak-to-average-power ratio reduction algorithm for discrete multitone systems is deduced by simultaneous optimization of the quadrature-amplitude-modulation constellation and the unused discrete multitone subsymbols. The proposed method is also applicable to multicarrier systems where all subchannels are active. Our simulations demonstrate that considerable performance improvement can be achieved over several existing methods at the cost of increased computational complexity.

Peak-to-average power-ratio reduction for OFDM systems based on method of conditional probability and coordinate descent optimization

A new constellation extension technique for peak-to-average power-ratio reduction (PAPR) in orthogonal frequency-division multiplexing systems is proposed. Two new algorithms for PAPR reduction are developed by applying the so-called method of conditional probability (MCP) and coordinate descent optimization (CDO). Our simulations demonstrate that the proposed algorithms outperform several existing algorithms and the performance can be further improved by combining the MCP, CDO, and the selective mapping algorithms