Hidden-Pilot-Aided precoding schemes for throughput improvement in OFDM-based wireless systems

Abstract

Orthogonal frequency division multiplexing (OFDM) has emerged as one of the most attractive transmission schemes for digital communications in recent years. OFDM is essentially a block-modulation scheme in which the data symbols are multiplexed onto multiple orthogonal subcarriers. The throughput performance of OFDM systems is critically dependent on the accuracy of channel estimation and the efficiency of bandwidth utilization. In this dissertation, a hidden-pilot-aided precoding scheme is proposed in OFDM-based systems for various wireless communication environments. This scheme has the virtue of high performance of throughput thanks to the bandwidth efficient channel estimation and high frequency diversity. A hidden-pilot-aided approachs for multiple input multiple output (MIMO)-OFDM and multiuser MIMO-OFDM access (MIMO-OFDMA) are investigated, including the mathematical analysis on the reduction of peak to average power ratio (PAPR). Then, the solution of allocating power to the pilot which maximizes effective signal to interference plus noise ratio (SINR) is derived. Furthermore, in the slowly time-varying channel, the time-multiplexed channel estimation method which yields performance improvement in channel capacity is presented. Considering the concurrent transmissions in a wireless personal area network (WPAN), density-aware exclusive region-based scheduling is proposed to enhance the total network throughput. Simulation results show that the proposed scheme outperforms the throughput of the conventional schemes.