Performance of Coded 16-QAM OFDM Modulation with Equalizer Over an Aeronautical Channel

Abstract

The main objectives of iNET (Integrated Network Enhanced Telemetry) are increased data rate and improved spectral efficiency [1]. In this paper we propose that transmission scheme for the physical layer is coded 16-QAM OFDM (Quadrature Amplitude Modulation-Orthogonal Frequency Division Multiplexing) which enables high data rate and spectrum efficiency. However in high mobility scenarios, where the channel is time-varying the receiver design is more challenging. Therefore in this paper pilot-assisted channel estimation is used at the receiver, with convolutional coding and error correction to enhance the performance; while the effect of inter symbol interference (ISI) is mitigated by cyclic prefix. The focus of this paper is to evaluate the performance of OFDM with 16-QAM over an aeronautical channel. The 16-QAM with OFDM enables 4 bits/symbol and provides a higher data rate than QPSK hence it is chosen in this paper. The implementation of OFDM is done using Inverse Fast Fourier Transform (IFFT) and the Fast Fourier Transform (FFT). In this paper we simulate how the performance of Coded 16-QAM OFDM is enhanced using equalization to compensate for inter symbol interference, convolutional coding is used for error correction, puncturing for improving data rate and the insertion of cyclic prefix (CP) to avoid inter carrier interference.