Imperfect Channel State Information Based Robust Secure Beamforming In Satellite Terrestrial Integrated Networks

The satellite terrestrial integrated network(STIN)integrates the advantages of satellite communication networks and ground mobile networks to meet the requirements of next-generation wireless communication systems for wide-area coverage and seamless connectivity.However,the openness of the wireless channel and the wide coverage of satellite communication pose serious challenges to the information transmission security of the STIN.This paper investigates the secure Beamforming(BF)technology in STIN,utilizing physical layer security techniques,with a focus on addressing the imperfect Channel State Information(CSI)of the eavesdroppers.The main works are as follows:(1)For the scenario of spectrum sharing between satellite communication networks and ground mobile networks,a robust security BF algorithm based on the criterion of maximizing the minimum achievable secure rate is proposed.Firstly,in the case of a single user and multiple eavesdroppers,we formulate an optimization problem that seeks to maximize the minimum achievable security rate in satellite networks,subject to constraints on quality of service(Qo S),transmission power,and security interruption probability.Then,a robust BF optimization algorithm based on semi-positive definite programming and Dinkelbach is proposed,and BF weight vector is obtained by randomization method.Finally,computer simulation results show that the proposed algorithm can significantly reduce system power consumption while ensuring communication security.(2)For intelligent reflection surface(IRS)assisted STIN,a robust security BF algorithm based on the total transmitted power minimization criterion is proposed.Firstly,in the scenario of a single-user with multiple eavesdroppers,and with imperfect knowledge of the eavesdroppers’ CSI,the optimization problem is established with the objective of maximizing the minimum achievable secure rate in the satellite network while considering user service quality,limited transmission power,and a secrecy outage probability constraint.Secondly,in order to solve this non-convex problem,the upper and lower bounds of the eavesdroppers’ the output signal-to-noise ratio under the condition of imperfect CSI are derived by employing triangle inequality together with Holder inequality.Then,a joint optimization scheme of robust BF and power control based on semi-positive definite programming and penalty function method is proposed.Finally,the outcomes of computer simulations confirm the success and superiority of the method.(3)For STIN communication systems using rate splitting multiple access(RSMA),a robust security BF algorithm based on the criterion of maximizing the system energy efficiency is proposed.Firstly,a joint optimization problem is constructed with energy efficiency maximization as the target,user service quality and interception interrupt probability of eavesdroppers as the constraints.Then,a joint optimization algorithm combining Dinkelbach,successive convex approximation and penalty function is proposed to obtain BF weight vectors of satellite and base station.Lastly,the outcomes of computer simulations demonstrate that the suggested approach outperforms the conventional algorithm and brings system energy efficiency closer to the optimal state.