Non-orthogonal Multiple Access Based Resource Scheduling For Space-based Internet Of Things

The space-based Internet of Things can make full use of the advantages of satellite global coverage and wide-area connectivity,so that it is able to effectively cope with the challenge of global seamless access of Internet of Things nodes in large-scale,cross-regional and complex environments.It has become the cross-research hotspot of international aerospace and network communication.Resource scheduling is a key technology that determines the capacity and spectrum efficiency of wireless systems.Compared with the traditional ground Internet of Things,satellite links have the characteristics of limited power and link asymmetry.The space-based IoT faces severe challenges in terms of system capacity and number of access terminals,and puts higher requirements on resource scheduling.As the key technology of the fifth generation mobile communication,non-orthogonal multiple access can effectively increase the system capacity and greatly increase the number of access terminals,providing an important means for solving the large-scale massive access of space-based Internet of Things.This paper has carried out research on the key technologies of non-orthogonal multiple access resource scheduling in space-based Internet of Things.The main work is as follows:Firstly,for the problem that the user's quality of service cannot be met,a downlink resource scheduling scheme QDRS is designed for user expected rate optimization.In QDRS,the pre-grouping processing for users' quality of service requirements is carried out,and the non-orthogonal multiple access downlink resource allocation model of space-based IoT is constructed.The user clustering greedy algorithm for system capacity optimization is proposed.A power allocation algorithm that takes into account the user's expected rate is designed.The simulation experiment is carried out by using the real parameters of the Iridium satellite.The results show that compared with the traditional multiple access scheme of the Iridium satellite,QDRS can effectively increase the average system capacity by 13.88% and reduce the outage probability by 35.68%.Secondly,aiming at the problem of limited system capacity,an uplink resource scheduling mechanism QURS based on satellite-borne serial interference decoding is proposed.In QURS,a space-based IoT non-orthogonal multiple access uplink resource allocation model for users' quality of service requirements is established.A user clustering algorithm based on multi-user system capacity and outage probability optimization is designed.The power allocation algorithm of receiver sensitivity is simulated by using real link propagation model of the Iridium satellite.The results show that compared with the traditional multiple access scheme of the Iridium satellite,QURS has an obvious improvement in system capacity,and the performance improves with number of users in each cluster.The average outage probability is reduced by more than 9.98%,which can effectively meet the user's expected rate of personalized customization needs.