| The contradiction between the ever-increasing demand for communication capacity and the limited spectrum resources is the core problem faced by the current wireless communication system.Multi-user sharing of wireless resources is an idea to solve the above-mentioned contradictions,but this may cause interference among multiple users.In order to solve the inter-user interference,the combination of multi-antenna technology and precoding technology is an effective research direction.However,the traditional multi-antenna technology has been unable to meet the demand for the rapid increase in the amount of communication data and the number of mobile devices.Massive Multiple-Input Multiple-Output(m MIMO)technology is used to solve the above problems,because it can continuously tap space resources,thereby significantly improving the system's spectrum efficiency.Hybrid precoding technology combines analog precoding and digital precoding,which can compromise system performance and system complexity,and has become one of the research hotspots in m MIMO systems.On the other hand,because the symbol level precoding(Symbol Level Precoding,SLP)technology can not only use CSI,but also the constellation structure of the symbols to be transmitted,SLP can achieve higher performance than traditional precoding.Therefore,this article combines the hybrid precoding and SLP technologies for the m MIMO system.The specific research content is as follows:(1)In this paper,under the constraints of Symbol Error Probability(SEP)at the user end,the constellation diagram size and the mixed precoding signal are jointly optimized to minimize the signal transmission power at the transmitter.In order to make the research more practical,considering that the conversion rate of analog precoding may not meet the theoretical requirements.This paper proposes a multi-symbol analog and symbol-level digital hybrid precoding scheme.According to SEP constraints and the rate of change of analog and digital precoding,the multi-symbol analog and symbol-level digital precoding are matched,and the problem of minimizing the transmission power is established.In order to solve this problem,first solve the all-digital SLP that minimizes the transmission power under the SEP constraint.Then,establish the least squares problem of all-digital SLP and hybrid precoding.Specifically,the method of sequentially updating the analog precoding column vector and then using the least squares to obtain the digital precoding matrix is used to solve the problem.In this way,a hybrid precoding signal based on the user's SEP constraint is obtained.Finally,the design scheme is simulated and verified,and the simulation results show the effectiveness of the scheme.(2)This paper studies the problem of minimizing the user's maximum SEP when the transmit power is given.And consider and propose a multi-symbol analog and symbol-level digital hybrid precoding scheme.According to the transmission power constraint and the rate of change of analog and digital precoding,the multi-symbol analog and symbol-level digital precoding are matched,and the problem of minimizing the maximum SEP of the user is established.Because the analog precoding and digital precoding variables are coupled,the mixed precoding signal is difficult to obtain directly.Therefore,this paper divides the original optimization problem into two sub-problems.Firstly,under the constraints of the transmit power,find the all-digital SLP with the largest SEP of the user and the smallest.Then,the hybrid pre-encoded signal is used to approximate the obtained all-digital SLP signal,thereby obtaining the hybrid pre-encoded signal.Finally,the design scheme is simulated and verified.The simulation results show that the analog precoding of different symbols matches the symbol-level digital coding.The faster the change rate of the analog precoding,the better the performance of the system,but the transmission power will increase accordingly,which increases the energy consumption of the system. |
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