High-speed Photonic Terahertz Wireless Communication Assisted By Digital Signal Processing

Terahertz wave is the electromagnetic wave with the wavelength range lying between 0.03-3 mm,which features strong penetrability,low photon energy,high directivity,and extremely high carrier frequency.Therefore,it has great potential in terahertz high-speed wireless communication,imaging and other applications.Nowadays,most of the wireless communication systems are focusing on the microwave band,but it is difficult to increase the communication rates,due to the limitation of bandwidth.Under this circumstance,terahertz technologies have been naturally considered as a good candidate for achieving higher communication capacity.However,terahertz has some drawbacks,such as short transmission distance limited by the radiation power,high sensitivity requirement for the receiver.In the view of this situation,we consider to expand the wireless transmission distance by improving the receiver sensitivity,which is performed by developing advanced digital signal processing(DSP)demodulation algorithms.For this purpose,we study high speed terahertz photonic wireless communication based on digital signal processing.In this thesis,we firstly introduces the basic framework and key components of the terahertz photonic wireless communication system,and then carries out the link power budget.Next,based on the propagation property of advanced modulation formats in a terahertz photonic wireless link,two digital demodulation receivers are designed and developed for quadrature phase shift keying(QPSK)and Quadrature Amplitude Modulation(16-QAM)signals,respectively.The overall framework of'the receiver and the enabling algorithms are also introduced.The key DSP algorithms for demodulating QPSK signals include Gardner Timing-error Detector based timing recovery,constant modulus algorithm(CMA)based blind equalization,carrier quad-power algorithm based frequency offset estimation and compensation,and Viterbi algorithm based carrier phase recovery.To demodulate 16-QAM signals,a preprocessing module,multi-modulus algorithm(MMA)based blind equalization,and blind phase search algorithm(BPS)based carrier phase noise estimation and recovery are employed.Finally,we experimentally demonstrate a high speed THz photonic wireless communication system in the 350 GHz band carrying QPSK and 16-QAM signals.In the experiment,30 Gbaud/s QPSK and 25 Gbaud/s 16-QAM signals are transmitted over up to a 2 m THz wireless link,with respect to the HD-FEC BER performance,and hence 100 Gbit/s THz photonic wireless transmission with an extended wireless reach is successfully achieved in the proposed system by using our homemade digital receiver,resulting in an enhanced bitrate-distance product of 200 Gbit/s m.Furthermore,the work of this thesis is expected to pave the way to further develop of terahertz high speed wireless communication.