Research On Multi-slot Pilot Allocation Random Access Protocol For Space Internet Of Things

As an inevitable development trend of mobile communication,the space Internet of things(S-IoT)is expected to be commercially available in building an integrated information infrastructure network of the space,air,ground and ocean,etc.The S-IoT is promising to provide wide area coverage,which allows for breaking through the bottleneck of fragmented network in the ground Internet of things,and providing global seamless coverage,instant access to mobile broadband services.Considering the massive machine-type communication(mMTC)access demand in satellite communication scenarios,an innovative multi-slot pilot allocation(MSPA)random access protocol is proposed,which can significantly improve the system throughput while ensuring the access failure probability requirements of devices.Moreover,a mixed device access scenario with unequal access delay requirements is considered.Based on the MSPA random access protocol,a random access scheme with unequal access latency(UAL)protection mechanism is proposed in this dissertation,where the devices are divided into multiple groups and are permitted to access in particular phase.Considering massive connectivity requirements of S-IoT and the long time delay token by the link between the earth and satellite,a multi-slot pilot allocation(MSPA)random access protocol is proposed,where the dense devices are permitted to jointly transmit randomly chosen pilot sequences along with their data packets over multislot.By utilizing the power control method and the finite length analyses for SIC process,the satellite can detect the types of pilot,and derive the closed-form expressions to the access failure probability and system throughput.The results show that by increasing the access time slot properly,the access opportunity of each device can be increased so as to alleviate pilot collision in the overload.Compared with the existing random access protocols,the MSPA protocol can not only guarantee the access failure probability,but also improve the system throughput.Further,considering the mMTC devices with diversified access latency requirements in S-IoT,two MSPA based UAL random access schemes are proposed in this dissertation,namely independent UAL-MSPA(I UAL-MSPA)scheme and expanded UAL-MSPA(E UAL-MSPA)scheme,where the devices are divided into multiple groups based on their access latency requirements,and the transmission frame is divided into multiple stages.The closed-form expressions to the AFP and throughput of each group in these two schemes are derived.Moreover,the above derived expressions are utilized to optimize the E UAL-MSPA scheme by formulating a joint parameter optimization problem under diverse access failure probability and access latency constraints.Simulation results show that compared with the I UALMSPA scheme,the E UAL-MSPA scheme can utilize the redundant pilot resources that are allocated to the high priority group to provide offloading for the low priority group,which significantly alleviates the pilot collision of low priority devices and thus reduces the access latency.