Research On Uncoordinated Random Access Protocol For Space Information Networks

The space information network is an international scientific frontier and strategic national infrastructure,which plays an important role in navigation positioning,ocean-going voyages,emergency rescue,relay communication,air transport,aerospace measurement and control,real-time transmission,and space exploration.The access system is one of the most important components of SIN.In order to meet the access requirements of various user terminals in the SIN,the key issue is to solve the problem of access to a large number of terminals in SIN.In order to achieve random access with large capacity and high reliability for large-scale non-cooperative Machine-type Communications(MTC)equipment,this dissertation innovatively proposed the Joint Random Pilot and multi-slot Access(JRPMSA)protocol based on competitive random access protocol framework of the non-cooperative users.In view of the diversification of large-scale user delay requirements in space information networks,this dissertation proposes a pilot random access feedback scheme.The scheme guarantees the random access performance of users with different delay requirements.Based on the characteristics of the long-term delay of the satellite link in the spatial information network,combined with the scenario of large-scale equipment non-cooperative burst access communication demand of mMTC in the future,the second chapter studies the non-cooperative user contention-based random access procedure.The continuous interference cancellation(SIC)algorithm is used to recover the conflicting user information on the access satellite.Focusing on the access failure probability and throughput performance of Contention Resolution Diversity Slotted ALOHA(CRDSA)protocol and Frameless ALOHA protocol in the above scenarios,theoretical analysis and simulation verification have laid a solid foundation for the subsequent research ideas and analysis methods.When a large-scale non-cooperative MTC device accesses a spatial information network,collisions are likely to occur and access failure occurs.In Chapter 3,the Multi-Slot Random Pilot Access protocol is proposed.The specific process of the JRPMSA protocol is designed.The pilot selection of the device in multiple access slots is established by the bipartite graph,and the degree distribution expression of each node in the bipartite graph is derived.Then use the "and-or tree" tool to analyze the probability update of each node information is not restored,and derive the expression of access failure probability and throughput that characterize system performance.The simulation results show that the protocol can still achieve 0 access failure probability when the system is slightly overloaded,which can greatlyimprove the access success rate compared with the existing access protocol.Further,considering that large-scale non-cooperative MTC devices may have different access delay requirements,Chapter 4 proposes a hierarchical JRPMSA protocol,which classifies user packets and time slots according to access delay requirements to meet different access times.In order to alleviate the pilot collision situation caused by different priorities in each time slot,an intermediate feedback mechanism is introduced to reduce the interference of the successfully transmitted device in the preamble time slot to the subsequent time slot.Three feedback schemes are proposed,full feedback,partial feedback and group feedback.The access failure probability of devices with different delay requirements in the three schemes is derived.The simulation results show that the hierarchical JRPMSA protocol can select different feedback mechanisms in different load intervals,which can effectively reduce the access failure probability.