On Cross-layer Slotted Random Access Schemes For IoT-oriented Satellite Networks

To achieve global connectivity,satellite communications offer a more cost-effective solution for remote areas that are difficult to be covered by terrestrial communication networks.At the same time,in the application scenarios of smart grids and utilities,the interruption of terrestrial network may damage the fixed wireless infrastructure.To implement the highest availability of data communication at a reasonable cost,satellites could provide a true alternative path.Therefore,satellite network plays a key role in supporting internet of things(IoT)applications.The employment of random access(RA)schemes for the initial access of the satellite network can avoid frequent resource applications and dynamic scheduling processes.However,as the increase of the number of IoT terminals,the collision probability in the RA channel will increase,the utilization of system resource will decrease,and the access performance will deteriorate.Therefore,the research on high-throughput RA protocols is very important for IoT-oriented satellite network.Starting from the research of slotted RA schemes,and taking the expansion of competition space in satellite channel as the entry point,we make full use of the free dimension introduced by the signal parameters in physical layer,and deeply analyze and study the slotted cross-layer RA schemes based on the new dimension.The main research contents and contributions are as follows:1.By the introduction of the polarization dimension,slotted RA protocols based on the polarization multiple-input multiple-output(MIMO)transmission scheme are proposed.Starting from the polarization MIMO transmission scheme,the system model and the polarization MIMO transmission framework are introduced in detail.Aiming at the shortcomings of the low-peak throughput in conventional slotted ALOHA(SA)protocol,the polarized MIMO slotted ALOHA(PMSA)scheme is introduced.Aiming at the deadlock problem in contention resolution diversity slotted ALOHA(CRDSA)class protocols,the polarized MIMO contention resolution diversity slotted ALOHA(PM-CRDSA)class schemes are introduced.In PMSA and PM-CRDSA class protocols,the transceiver processes are described in detail and the theoretical performance of PMSA and PM-CRDSA is deduced and analyzed.Finally,the simulation results show the performance gains brought by PMSA and PM-CRDSA class protocols in the throughput,packet loss rate(PLR),energy efficiency,and delay.The application of the polarization MIMO transmission scheme in the existing random access protocols can effectively improve the access performance,which has great appeal in the satellite random access system.2.By the introduction of the packet length dimension,RA protocols based on the adaptive packet-length assisted(APL-assisted)scheme are proposed.The main idea of which is to adopt different modulation and coding schemes(MCSs)to change the length of data packet according to the channel transmission quality to reduce the collision probability in the slot.In the low earth orbit(LEO)satellite network,the method of generating packets and the distribution of packets with different lengths in the APL-assisted schemes are introduced.To improve the peak throughput and linear throughput region in SA and CRDSA class protocols,the APL-SA and the APL-CRDSA class protocols are proposed respectively.From both the theoretical analysis and computer simulations,the proposed schemes show better than the existing protocols in terms of throughput,PLR,energy efficiency and delay.In addition,the former could achieve higher linear throughput region.3.By the introduction of the power dimension,schemes based on power water-filling and CRDSA class schemes based on power diversity are proposed and discussed.The positive impact of transmission power diversity on the performance in CRDSA is theoretically analyzed and verified by simulations.According to the characteristics of LEO satellite network,schemes based on power water-filling are proposed for the purpose of enhancing the capture effect,and the specific power control algorithm is given.Simulation results show that the proposed schemes could achieve higher throughput and PLR performance than existing protocols.Finally,comprehensive simulations and analysis are carried out for the proposed polarization MIMO transmission schemes,adaptive packet-length assisted schemes and power optimization schemes,which further demonstrates the application potential of the proposed schemes in the satellite IoT.