Frequency-Domain Punctured Turbo Codes

Abstract

This paper presents a frequency-domain puncturing method for turbo codes. Conventional rate control for turbo codes is achieved by time-domain puncturing where some of the coded bits (parity bits) are punctured to increase the coding rate. The proposed puncturing method is done in the frequency domain. After applying the discrete Fourier transform (DFT) to the transmission coded symbols, some of the frequency components (spectrum) are punctured to increase the coding rate. The difference from the conventional time-domain puncturing is that the frequency-domain puncturing can transmit all the coded bits. Therefore, the coding gain is expected to increase. However, the frequency-domain puncturing operation causes inter-symbol interference (ISI). Therefore, we propose applying frequency-domain turbo equalization based on a soft canceller followed by the minimum mean squared error filter (SC/MMSE) at the receiver to mitigate the ISI. The simulation results show that the additional use of the frequency-domain puncturing can improve the bit error rate (BER) and frame error rate (FER) compared to pure time-domain puncturing.