Transmission Policy Over Time-varying Channels For Space Information Networks

The future of Space Information Network(SIN)can achieve land-based networks,air-based networks,space-based network interoperability,combine information acquisition,information processing,information releasing efficiently and intelligently.With the help of SIN technology,the coverage area and effectiveness of information processing can be improved significantly.High-throughput satellites of the future can provide information broadcasting and terminal access services,to achieve ubiquitous broadband access.Compared to S/X/C band,the Ka-band channels can provide an appealing capacity for the future deep-space communications and SIN,which is viewed as a primary solution to satisfy the increasing demands for high data rate services.However Ka-band channel is much more sensitive to weather conditions of ground station area,bad weather like rainstorm may result high data loss.An optimal transmission scheme based on Partially Observable Markov Decision Process(POMDP)is proposed,which can effectively improve the throughput and efficiency.Based on the ITU-R rainfall attenuation model,the Markov transition process is used to simulate rain attenuation events,get the channel transition probability matrix.Knowing the depth of rainfall decline,it is reasonable to divide the rainfall events.The rainfall process is equivalent to moving from one state to another.The state transition has Markov chain characteristics.Rainfall decay slope model is used to solve the transition probability matrix,which simulates rain attenuation events by Markov chain.Considering the algorithmic complexity of adaptive transmission strategy decision,the time-varying rain attenuation at Ka-band channel is modeled to a two-state GE channel.The Ka-band link is affected by rainfall,which causes the state of the GE channel changing randomly.In order to ensure the efficient and stable data transmission,an optimal transmission scheme based on POMDP for single link and multiple identical links are proposed.Considering the huge distance and long propagation delay in SIN,generally,the delay tolerant network protocols that Consultative Committee for Space Data Systems File Delivery Protocol(CFDP)and Licklider Transmission Protocol(LTP)are widely used in SIN communication scenarios,where the transmitter can obtain the delayed Channel State Information(CSI)from Negative Acknowledgment(NACK)feedback.When the space communicates with multiple ground stations,the weather conditions of different ground stations are different.A multi-link data transmission scheme based on multiple link belief probability for adaptive power allocation decision was designed.Combined with the power allocation scheme,the Geosynchronous Earth Orbit(GEO)satellite communication system and the Low Earth Orbit(LEO)satellite communication system are taken as examples to design a multi-downlink optimal transmission scheme.We compare the long-term effect of the expected throughput of our adaptive data transmission scheme with conventional fixed-rate schemes,to validate the optimality of our POMDP-based transmission policy over Ka-band channels for SIN communications.