Linear carrier predistortion for inter-carrier interference mitigation in multicarrier-RF systems

摘要

Linear carrier pre-distortion specifically designed to rearrange the spatial distribution of data-symbols in the constellation diagram is proposed for Intercarrier Interference Mitigation in an electrical multicarrier (MC) system. The linear carrier pre-distortion is achieved by convolving a pre-designed transfer function with each radiofrequency carrier previous by means of a redistribution of the QPSK data-symbols over IQ plane for each carrier composing the MC signal before the up-conversion to RF. At the receiver, an adaptive linear equalizer (Least Mean Squared) re-constructs the QPSK constellations for each radiofrequency carrier after signal demodulation. Our proposal is numerically validated by simulation in a 3 × 0.5 Gbaud Nyquist PSK multicarrier system. For BPSK, the inter-carrier overlapping percentage (IOP) takes values from 90% down to 75%, this enables a reduction of 15% in carrier spacing, and a symbol error rate (SER) gain of 1.2 dB for a Nyquist separation of 0.75. Whereas for QPSK, the reduction achieved is 15%, and the SER gain is 1.8 dB for a Nyquist separation of 0.85 (Being ideal a carrier spacing equal to 100% as carrier bandwidth). We believe that the proposed linear carrier pre-distortion technique enables further investigations on signal constellation re-distributions allowing controlled inter-carrier interference in the context of next broadband generation technologies.