Coverage And Capacity Analysis Of LEO Satellite Network Supporting Internet Of Things

Because of the characteristics of low orbit,large bandwidth,and full coverage,LEO satellite network can provide all-around access not bound by geographic positions.It provides an effective way to connect IoT devices which are deployed in inaccessible areas such as desert and sea.However,polar orbit or near-polar orbit usually used in LEO satellite constellations may result in uneven coverage on different latitudes.This uneven coverage restricts the number of devices can be accessed in the network.So it is important to model the uneven coverage for quantitatively analyzing the relationship between parameters and performance of LEOIoT.In this paper,we focus on two problems that 1)how to measure the uneven coverage with the change of latitude and 2)how to measure the uneven network capacity caused by uneven coverage.To solve these problems,we propose a metric named Coverage Degree to measure average cover level during a return circle of a satellite constellation in different latitudes.We first use an indicator function to represent whether the observation point is covered by a satellite.Then,considering the spot beam communication process with TDMA as a discrete time queueing process,we put forward a metric named Device Density to express the number of devices can be accessed in a unit area during a period.Finally,we develop an LEO satellite IoT coverage and capacity analysis system and use the Iridium constellation to test and evaluate it.The experiment result shows that the coverage and the capacity are influenced by many factors such as latitudes,half cone angle,spot beam number and slot number.