Research On Hybrid Pilot Non-orthogonal Multiple Access For Satellite-based Internet Of Things Networks

As the supplement of terrestrial network,satellite-based internet of things(S-Io T)will provide global coverage and cost-effective broadband access for massive type communications(m MTC)in the forthcoming fifth generation(5G)Io T,In order to satisfy the access requirements of massive user equipment in S-Io T scenario,this paper studies the superimposed pilot non-orthogonal access(SP-NOMA)protocol,and analyzes the performance of outage probability and achievable throughput under successive interference cancellation(SIC)and successive joint(SJD)decoding methods.Furthermore,a hybrid pilot scheme is proposed to further improve the access ability of m MTC services in S-Io T.As the SP mechanism leads to the traditional least square estimation algorithm failed.Firstly,an iterative channel estimation algorithm based on ridge regression(ICEK)is proposed,and based on the statical information of activated user equipments' power to identify the pilot collision.The expressions of outage probability and achievable throughput under SJD and SIC are derived under shadowed-Rician channel for SP-NOMA.Monte Carlo simulation verifies the accuracy of the theoretical derivation.The achievable throughput performance of between superimposed pilot system and orthogonal pilot system are compared.The simulation results show that the superimposed pilot system is more suitable for short packet length communication scenarios for m MTC.On this S-Io T,the HP-NOMA mechanism is further studied to explore the optimal pilot scheme of S-Io T under different communication parameters.A low complexity iterative channel estimation algorithm based on kaczmarz(ICEK)is proposed,and the convergence factor is added to accelerate the convergence speed of the estimation algorithm.Based on this,the expression of outage probability under HP-NOMA is given,and the closed expression of key parameters in HP-NOMA is deduced and optimized.The novelty of this paper is designing the HP-NOMA mechanism in S-Io T,analyzes the performance of system under different parameters of S-Io T when using RP,SP and HP mechanism.Furthermore,the optimal adaptation scenarios of three pilot mechanism is provided and verifies by Monte Carlo simulation.