Research On Energy Saving Resource Allocation Algorithm Based On SCMA

The application scenarios of future wireless communication systems have the characteristics of continuous wide-area all-round coverage,high-capacity distribution in hotspots,low energy consumption,and millions of connections.In order to meet these demands,the problems of high energy consumption and limited spectrum are facing unprecedented severe challenges.Lower energy consumption is the key to reducing carbon emissions,extending the battery life of wireless devices,and green communications.In order to make full use of spectrum resources,improve spectrum utilization and reduce energy consumption,this paper considers a sparse code multiple access(SCMA)technology with superimposed transmission signals.SCMA is a nonorthogonal multiple access technology based on multi-dimensional codebook.By designing a nearly optimal sparse codes to achieve code domain multiplexing,it not only improves the spectral efficiency significantly,but also reduces the access delay and terminal energy consumption by means of license-free access.Firstly,this paper introduces the basic principle and technical characteristics of SCMA,including the basic definition,coding principle,codebook design and decoding principle of SCMA.Specifically,such as high-dimensional modulation and sparse spread spectrum technology used in encoding and codebook design,and the message passing algorithm(MPA)involved in decoding.Furthermore,this article also introduces the basic definitions and principles of cognitive radio technology and MIMO technology,and combines them to illustrate the basic structural characteristics of cognitive MIMO networks.In addition,the theoretical basis and objective function establishment of using resource allocation to achieve energy-saving effects are discussed.Next,we consider a sparse code multiple access downlink system energy-saving strategy to minimize the total system power consumption by jointly optimizing power allocation and subcarrier resource allocation algorithms.In this system,the problem is a non-convex programming problem,which is hard to solve.To make it traceable,we first transform the power allocation problem into a standard convex optimization problem by using the relaxation integer and Lagrange dual decomposition.Furthermore,considering the characteristics of users,a fast search algorithm is proposed to allocate subcarriers.Simulation results show that the proposed joint power allocation and sub-carrier resource allocation algorithm can effectively reduce the transmission power consumption of the downlink system and the user fairness can be also be guaranteed.Finally,in order to further verify the compatibility of SCMA and highlight its superiority,this paper designs a SCMA non-orthogonal allocation scheme combined with cognitive MIMO system to discuss the energy-saving effect of the scheme.Traditional cognitive MIMO networks use time division multiple access(TDMA)orthogonal time slot allocation to optimize energy consumption.Although it achieves the purpose of energy saving,it limits the number of users who can access the system.In view of the above problems,this solution can convert the orthogonal time slot units of TDMA into non-orthogonal shared time slot units of multiple secondary users(SUs).A method of increasing virtual users is adopted,in which each SU is regarded as multiple SUs occupying a shared unit to facilitate group access.Then,a greedy algorithm is used to calculate the time slot assignments that do not occupy the shared time slot unit.The simulation results show that compared with the orthogonal scheme,the non-orthogonal slot allocation based on SCMA can not only further reduce the time consumption.When there are more access users,the average power interference of SUs to the main link users will be reduced by nearly 2 dB.In addition,under the constraints of meeting user rate requirements,the system user capacity has also increased.