Multi-group Multicast Beamforming In Millimeter Wave Satellite-terrestrial Cooperative Communication System

In order to meet the increasing demand of user capacity and transmission rate,the future communication network needs to provide larger bandwidth,higher spectrum efficiency,and accommodate more users.When the existing frequency bands are gradually unable to meet these needs,millimeter wave technology,which has massive undeveloped spectrum resources in it's communication frequency band,are becoming a key technology that has received widespread attention in the research of next-generation wireless communication networks.At the same time,satellite communication has good application foreground in networks that have higher demands for high capacity,low latency and wide coverage because of the unique ability to provide seamless connections and high data rate at the same time.Combining the advantages of providing high communication rate and ensuring high user coverage,the millimeter wave satellite-terrestrial cooperative communication system will play an extremely important role in the realization of B5 G and 6G communication systems.Based on the above background,this article first briefly introduces some technical points involved in the millimeter wave satellite-terrestrial communication system,such as the millimeter wave technology with the problems and difficulties in its implementation,the fundamental of multi-group multicast and beamforming technology,as well as satellite-terrestrial communication technology with its main difficulties.Then taking a simple model of multi-group multicast beamforming technology as an example,some optimization algorithms suitable for the beamforming design in communication system are introduced.Then,for the problem that some existing satellite-terrestrial communication system power optimization design schemes did not fully utilize the satellite-terrestrial joint optimization performance gain,based on a millimeter wave satellite-terrestrial cooperative communication system model using multi-group multicast,this paper proposes a satellite-terrestrial joint beamforming design scheme that is constrained by Quality of Service(Qo S),and the goal of this scheme is to minimize the satellite transmission power.For this beamforming design scheme,an optimization algorithm based on positive semi-definite relaxation and randomization method is given to solve the beamforming vectors,and the performance of this algorithm is verified by simulation.Finally,in order to improve the anti-interference performance of the millimeter-wave satelliteterrestrial cooperative communication system with multi-group multicast,this paper applies the rate splitting strategy to give a beamforming design scheme suitable for this type of system.Based on the principle of Max-Min Fairness(MMF),the optimization problem is expressed as maximizing the minimum achievable rate among all users under the system transmission power constraint.Due to the coupling rate constraint,this problem is a complex non-convex problem,which is difficult to solve using traditional methods.Based on the Weighted Minimum Mean Square Error(WMMSE)and the Alternating Direction Method of Multipliers(ADMM),this paper proposes an effective algorithm to solve the beamforming vector by iteratively solving a series of convex subproblems.This paper presents the specific steps of the algorithm,and uses the simulation results to verify the effectiveness of the algorithm.