| Emergency response is the swift and decisive action taken in response to various unforeseen incidents.As an important part of the national emergency system,it directly reflects the response ability in the face of emergencies.Low Earth Orbit(LEO)satellite Internet can effectively solve the problems such as slow network reconstruction and difficult data return in emergency response,with its advantages such as wide communication coverage,fast and flexible networking,and strong anti-destruction ability.It has great practical value and broad application prospects.In the emergency response based on the LEO satellite Internet,on the one hand,it is necessary to strengthen the construction of emergency communication network to provide communication support for emergency response,However,problems such as large transmission delay,frequent handover and increasingly serious inter-satellite interference in satellite Internet have brought new challenges to the construction of emergency communication networks.On the other hand,under the guarantee of satellite Internet,mobile crowdsensing can recruit terminals to help in real-time data collection,assist decision-makers to understand the situation on the site as soon as possible and make timely decisions and deployments.However,the difficulty of terminal recruitment and low sensing quality in emergency crowdsensing bring new challenges to the accuracy of sensing data.Therefore,in response to the above challenges,the main contributions from the two aspects of emergency communication and emergency crowdsensing of this thesis are summarized as follows:1.Research on low-latency and high-reliable access technology in satellite InternetTo realize the low latency,high-reliable and stable connection with satellite Internet,initial access and handover are optimized respectively in this research point.For initial access process,the access process is simplified in order to reduce the access delay,and the details of the two-step random access process are specific defined.Besides,in order to apply the New Radio(NR)protocol to the satellite Internet,as well as reduce the energy consumption of terminals,we redesigned the random access preamble and response time window.Additionally,a Physical Uplink Shared Channel(PUSCH)resource selection method is proposed to reduce collision probability and the number of PUSCH occasions that may be occupied.For handover process,a seamless handover mechanism based on handover prediction and resource reservation is proposed to avoid user’s interruption during frequent handovers.Moreover,to reduce resource waste while ensuring seamless handover,the impact of resource reservation time interval in advance on performance is investigated.The proposed methods can realize low delay and high reliable access to the satellite Internet and ensure service continuity.2.Research on high energy efficiency interference avoidance technology for satellite InternetIn order to improve the network performance in the multi-constellation coexistence scenario with increasing interference,this thesis proposed the high energy efficiency interference avoidance technology in satellite Internet.Firstly,a high energy efficiency power control algorithm is proposed to mitigate interference and improve constellation’s energy efficiency.Moreover,a multiattribute handover decision algorithm is proposed to select the optimal satellite for handover when the interference limit is not satisfied.On this basis,a prediction-based seamless handover mechanism in multi-constellation coexistence scenario is proposed to ensure the service continuity under the constraint of interference limitation for users.The above methods can maximize the energy efficiency of the constellation,guarantee the continuity of service and improve the quality of service while meeting the interference limit.3.Research on high-credibility emergency crowdsensing in satellite InternetIn order to achieve accurate and reliable data collection,a reputation-based participant recruitment scheme in satellite Internet is proposed in this thesis.The scheme includes reputation calculation method and reputation-based recruitment algorithm in satellite Internet,which can effectively select trusted terminals to perform sensing tasks.The reputation value calculation method takes into account the factors such as the terminal’s past behaviors,the terminal’s own ability and time fading,and realizes the real-time reputation evaluation of the terminal in the emergency scenario.The reputation-based recruitment algorithm in satellite Internet comprehensively considers the terminals’ reputation value,sensing quality,cost and connection status,and realizes the trusted terminal recruitment in emergency scenario.The scheme can detect the trusted and malicious terminals quickly and accurately,reduce the recruitment cost and improve the sensing quality. |
