Power amplifier non-linearity treatment with distorted constellation estimation and demodulation for 60 GHz single-carrier frequency-domain equalisation transmission

Power amplifier (PA) non-linearity is extremely significant for 60 GHz millimetre-wave communications, which distorts signal constellation seriously. In dealing with this problem, the commonly used digital predistortion (DPD) becomes unaffordable for 60 GHz systems in both power consumption and price. This study proposes to handle PA non-linearity with distorted constellation (DCS) estimation and demodulation for 60 GHz systems with single-carrier frequency-domain equalisation transmission, which has a low implementation cost. Employing the least-square (LS) algorithm, the DCS is estimated both before and after equalisation, where LS after equalisation has a lower computational complexity than LS before equalisation. Subsequently, the estimated DCS, instead of the standard constellation, is used as a criterion for demodulation, which is shown to achieve a significant improvement on the symbol-error-rate (SER) performance, especially when the non-linear distortion is severe. Moreover, compared with DPD, the proposed method achieves a better SER performance and behaves more robustly in the low range of input power back-off (IBO), whereas achieving a close SER performance in the high-IBO range.