Jia-Chyi Wu

Performance comparisons of PAPR reduction methods for the OFDM system

OFDM (Orthogonal Frequency Division Multiplexing) technique has been widely adopted in many wireless communication systems due to its high data-rate transmission ability and robustness to the multipath fading channel. One major drawback of the OFDM signal is the high peak-to-average power ratio (PAPR) problem. The high PAPR results in the in-band distortion and out-of-band radiation when the OFDM signal is fed into a nonlinear power amplifier (PA). In this paper, we propose a partition dummy sequence insertion (PDSI) method to reduce the PAPR problem and compare with the DSI method. Simulation results of the PAPR reduction and bit error rate (BER) performance for the proposed method are performed to demonstrate its capabilities.

Performance Comparison of the STBC-OFDM Decoders in a Fast Fading Channel

In a fast fading channel, the orthogonality of the two consecutive STBC-OFDM symbols will be destroyed and the received signals can not be perfectly separated. As a result, the bit error rate (BER) performance will be degraded seriously. In this paper, we analyze several CCI cancellation decoders for the STBC-OFDM in a fast fading channel including the Alamouti method, SIC method, ML method, DMLD method and the DZFD method. A simple DZFD method is given to reduce the computational complexity of the DMLD method.

Performance analysis of different HSDPA equalizers under the measured outdoor channels

To restore the orthogonality of the spreading code, an equalizer is adopted at the receiving site for a HSDPA system. In this paper, BER performance and complexity of various equalizer methods are compared and analyzed under measured outdoor channels. Besides, a FFT-circulant with tapering equalization approach is proposed for the downlink HSDPA receiver. Results show that with tapering technique, the fast FFT-circulant equalizer can ease its high conditional number problem at a high SNR multipath channel. Simulations also show that the CG method has a satisfactory BER improvement. However, its performance depends notably on its iterative number and requires higher computational complexity than the FFT-circulant with tapering method.

An Analytic Analysis of W-CDMA Smart Antennas Beamforming Using Complex Conjugate and DOA Methods

Wideband code division multiple access (W-CDMA) adopts the smart antenna techniques to increase the signal-to-interference-noise ratio (SINR) and system capacity. In this paper, we statistically derive an analytic result to prove the SINR performance for the two commonly used CC and DOA beamforming methods. Results show the both methods will have the same mean SINR performance and CC method will be more robust than the DOA method.

A Partition Dummy Sequence Insertion PAPR Reduction Method of the OFDM System

OFDM (Orthogonal Frequency Division Multiplexing) technique has been widely adopted in many wireless communication systems due to its high data-rate transmission ability and robustness to the multipath fading channel. One major drawback of the OFDM signal is the high peak-toaverage power ratio (PAPR) problem. The high PAPR results in the in-band distortion and out-of-band radiation when the OFDM signal is fed into a nonlinear power amplifier (PA). In this paper, we propose a partition dummy sequence insertion (PDSI) method to reduce the PAPR problem. Simulation results of the PAPR reduction and bit error rate (BER) performance for the proposed method are evaluated to demonstrate its capabilities.

A Group Sphere Decoder for the MIMO System

Multiple Input Multiple Output (MIMO) system employs multiple antennas at both the transmitter and the receiver to improve the BER (Bit Error Rate) and system capacity. Different signal detection algorithms have different computational complexity and BER performance. In this paper, we provide a group sphere decoder (SD) in a MIMO wireless communication system. The group sphere decoder can further reduce the computational complexity for the conventional SD method.

An Error Bound Based HARQ for HSDPA System

In this paper, we compare the throughput performance of several conventional HARQ protocols and propose an error bound based HARQ. In the proposed method, the number of bits of retransmission is determined by the BER required after decoding. In other words, the bits number on each retransmission is not fixed and can be varied according to SNR of the received signal and the ability of channel coding. Simulations have been carried out under the multipath Rayleigh fading channel with different Doppler shifts. Although the proposed method increases the traffic amount of the uplink channel, yet, results show that the proposed method can further improve the throughput compared with the conventional CC and IR HARQ methods for the HSDPA system.