Joint Optimization Of Precoding Schemes And Common Message Rate Allocation For RSMA In MISO Downlink Transmission

RSMA is a method proposed in recent years to improve MIMO transmission performance.Its basic idea is that the transmitter splits each message into a common and a private message,then the common parts,which are combined into a whole,and the private parts are transmitted in the same time-frequency resource block.The paper focuses on the joint optimization of RSMA precoding matrix and common message rate allocation,and compares its transmission performance with traditional SDMA and NOMA transmission methods.The main work of the thesis is as follows:Firstly,aiming at RSMA downlink MISO transmission,with the goal of maximizing the minimum user achievable rate,a joint optimization algorithm for precoding matrix and common message rate allocation is proposed.The main work includes: 1)For the mathematical optimization model corresponding to the problem,use the WMMSE method to convert it into an equivalent optimization problem;2)For the equivalent optimization problem,using equalizer variables,weight variables,and precoding matrices,common message rate allocation alternate optimization method,an iterative algorithm is proposed,and the solution of the original problem can be obtained according to the solution of the iterative algorithm;3)In the two scenarios of random channel and fixed channel respectively,simulations compared the achievable rate performance of the three transmission schemes under the condition of maximizing the minimum user achievable rate of RSMA,SDMA and NOMA,it is found that the performance of RSMA is better than the other two schemes,and the performance of SDMA and NOMA has its own advantages and disadvantages in different scenarios.Secondly,aiming at RSMA downlink MISO transmission,with the goal of maximizing minimum user energy efficiency,a joint optimization algorithm for precoding matrix and common message rate allocation is proposed.The main work includes: 1)For the non-convex optimization model corresponding to the problem,the continuous convex approximation method is used to propose a low-complexity iterative algorithm;2)The simulation compares the weighted sum rate and achievable rate performance of the cooperative RSMA based on the SCA method and the cooperative RSMA based on the WMMSE method,the non-cooperative RSMA,the equal time allocation cooperative RSMA,and the SDMA,It is found that the performance of the cooperative RSMA problem based on the SCA method and the WMMSE method is the same,but the algorithm complexity based on the SCA method is lower;for the weighted sum rate performance,the cooperative RSMA is better than or equal to the non-cooperative RSMA;for the sum rate performance,the two are equivalent;comparing the rate performance and the minimum user achievable rate performance,cooperative RSMA is always better than or equal to RSMA,which shows that cooperative RSMA is more conducive to the fairness of users than RSMA;the performance of equal time allocation cooperation RSMA and SDMA have their own advantages and disadvantages in different scenarios.Thirdly,aiming at the RSMA downlink MISO multi-user cooperative transmission scenario,with the goal to maximize the system weighted sum rate and maximize the minimum user achivable rate,respectively,a joint optimization algorithm of precoding matrix,common message rate allocation and cooperative transmission time allocation is proposed.The main work includes: 1)For both optimization problems,the continuous convex approximation method is used for convex approximation,and a low-complexity iterative solution algorithm is proposed;2)The simulation compares the weighted sum rate and achievable rate performance of the cooperative RSMA based on the SCA method,the non-cooperative RSMA based on the WMMSE method,and the equal time allocation RSMA and SDMA,it is found that the performance of solving the problem based on the SCA method and the WMMSE method is consistent,but the algorithm complexity based on the SCA method is lower;for the weighted sum rate performance,cooperative RSMA is better than or equal to non-cooperative RSMA;for the sum rate performance,the two are equivalent;comparing the sum-rate performance and the minimum user achievable rate performance,cooperative RSMA is always better than or equal to RSMA,which shows that cooperative RSMA is more conducive to user fairness than RSMA;the performance of equal time allocation RSMA and SDMA have their own advantages and disadvantages in different scenarios.Fourthly,aiming at the RSMA downlink MISO multi-user cooperative transmission scenario where there is a single-antenna eavesdropping user,with the goal of maximizing anti-eavesdropping secrecy sum rate,a joint optimization algorithm of precoding matrix and cooperative transmission time allocation is proposed.The main work includes: 1)Propose a strategy to use public messages as artificial noise to prevent eavesdropping,and based on this idea,establish a joint optimization mathematical model of precoding matrix and cooperative transmission time allocation;2)In view of the different value of the secrecy rate,the mathematical optimization problem is decomposed into four sub-problems to solve;the continuous convex approximation method is used to solve the four sub-problems;3)In the anti-eavesdropping scenario,with the goal of secrecy sum rate,the simulation compared the anti-eavesdropping performance of cooperative RSMA and NOMA,non-cooperative RSMA,NOMA,and SDMA.The results show that: for the same type of MA transmission,cooperative and non-cooperative confidentiality performance is equivalent;the confidentiality performance of RSMA is significantly better than the other two transmissions,and the confidentiality performance of SDMA is better than that of NOMA.