| As an important application scenario of the 6G ‘integrated communication network of heaven,earth and sea’,the ocean’s vast marine environment and huge share of marine trade have created a new paradigm for the Internet of Things,that is the Maritime Internet of Things.Similar to other Io T scenarios,Machine Type Communication(MTC)is the key to the maritime Io T.Without the support of the maritime MTC communication system,the maritime Io T will only be a fantasy.As an important component of the maritime MTC communication system,the Low Earth Orbit(LEO)satellite undertakes the task of providing communication services for the ocean environment.In order to meet the needs of maritime Io T communications,LEO satellites are equipped with multi-beam transmit antennas to increase speed and capacity,but this will cause severe inter-beam interference and affect transmission.Therefore,in this thesis,the research on satellite multi-beam transmission technology around the maritime Internet of things is carried out for the problem of inter-beam interference.In terms of specific research,first of all,this thesis briefly introduces the generation principle of satellite multi-beam,the antenna pattern used to present the spatial structure of the beam,analyzes and establishes the ground coverage model of the satellite equipped with multi-beam antenna,and obtains the ground received signal and SINR distribution diagram.,revealing the inter-beam interference existing in the coverage area.Then,for the problem of inter-beam interference suppression,this thesis firstly investigates the multi-beam satellite communication system using precoding technology,studies the theory of classical precoding algorithm,and conducts simulation verification.Considering that the classical algorithm cannot well compensate the channel damage to the received signal,a precoding scheme in the form of Kalman filter is proposed to approximate the channel inverse matrix through finite iterations.Finally,these algorithms are applied to the marine Io T scenario for comparative analysis.Simulation results show that the proposed precoding scheme has better performance in symbol error rate and system sum rate.Second,in addition to precoding techniques,satellites can also perform interference mitigation from a beam coordination perspective.This thesis firstly analyzes the specific form of inter-beam interference under beam overlap,and introduces a signal whitening scheme.Then on this basis,two beam coordination interference suppression methods,beam coordination and beam selective muting,are proposed respectively,and the corresponding beam selection principles are given.The experimental results show that the two methods of beam cooperation and beam selective muting can effectively suppress the interference of overlapping cells,improve SINR,and improve the sum rate.Finally,according to the different SINR conditions of terminals in adjacent beams,a combined algorithm based on beam cooperation and beam muting is proposed to further improve the performance of the system.The experimental results show that compared with beam cooperation and beam muting,the proposed combined algorithm can improve the actual sumrate of the system.Finally,the mobility interference management of the terminal in the case of satellite movement was studied.Firstly,the motion model of satellite and user terminal is introduced,and the movement trajectory of a terminal is given,so as to explain the problem to be solved more clearly.Then,the different services in the maritime Internet of Things are briefly introduced,and the Quality of Service(Qo S)required by different services is defined and classified.On this basis,different interference suppression algorithms are designed for different Qo S requirements,and the SINR and rate trajectories of mobile terminals under the management of different algorithms are given by simulation.The results show that the SINR and sum rate of the mobile terminal are improved with different algorithms.Finally,the ubiquity of different Qo S interference suppression algorithms for terminals at any location in the beam coverage area is verified,and the SINR and sum rate cumulative distribution function curves of different interference management algorithms are given.The experimental results of each algorithm show that the algorithm meets the design requirements. |
