Abstract: An ultra-low power data transmission method and apparatus are disclosed. An ultra-low power data transmission method to be performed by a user terminal of an ultra-low power data transmission system includes performing channel coding on a payload included in a transmission packet; interleaving a payload obtained through the channel coding, spreading the interleaved payload using a gold code and an orthogonal variable spreading factor (OVSF), combining a synchronization header spread using the gold code and the OVSF with the spread payload, and modulating a transmission packet in which the payload and the synchronization header are combined.

Abstract: A method and an apparatus for network synchronization in a satellite communication system is provided. a satellite station receives a superframe start timing (SST) and an initial counter value from a center station, and receives traffic information sent from a terminal station at a time determined based on the SST. Then, the satellite station generates a compensation value for the SST upon receiving the traffic information, and corrects the SST in accordance with the compensation value.

Abstract: Provided is an intelligent disaster management method and an apparatus using a satellite image. The disaster management method includes receiving a satellite image to monitor a disaster, setting a location of an area for disaster monitoring and a type of disaster to be monitored and selecting at least one satellite image associated with the location of the area and the type of disaster among the received satellite images through a satellite image selection model, synthesizing the selected satellite images through a satellite image synthesis model and generating disaster image data which enables to monitor a disaster, and monitoring a disaster of the area for disaster monitoring by using the disaster image data.

Abstract: A satellite cluster system may comprise: at least one slave satellite; a master satellite sharing a control signal and an information signal with the at least one slave satellite through an inter-satellite link; and a terrestrial control system for adjusting positions of the master satellite and the at least one slave satellite and transmitting the control signal and the information signal to the master satellite.

Abstract: An operation method of a terminal in a communication system may comprise: receiving, from a satellite, transmission timing information including information on a first transmission timing of a first SSB of each of at least one local cell and information on second transmission timings of second SSBs of sub-cells belonging to each of the at least one local cell; identifying the first transmission timing of the first SSB and the second transmission timings of the second SSBs based on the transmission timing information; attempting to receive the second SSBs when the first SSB is received at the first transmission timing; acquiring cell access information from the second SSBs by receiving the second SSBs; and accessing the satellite by using the acquired cell access information.

Abstract: A method for receiving a wireless signal, performed by a first communication node, may comprise: storing a wireless signal received by the first communication node as samples in a buffer; performing partial correlation operations on the stored samples by a plurality of partial correlators; performing a first FFT operation on results of the partial correlation operations; performing a cumulative product operation on results of the first FFT operation; performing a second FFT operation based on a result of the cumulative product operation; and performing synchronization estimation based on the results of the first FFT operation and a result of the second FFT operation.

Abstract: An operation method of an IoT terminal performing communications with a satellite may comprise: receiving a first signal from the satellite; determining a number of symbols constituting a preamble based on the first signal; generating a first frame including a preamble generated according to the determined number of symbols, and transmitting the generated first frame to the satellite; and generating a second frame including a preamble generated according to the determined number of symbols when a response signal to the first frame is received from the satellite, and transmitting the generated second frame to the satellite.

Abstract: A method for receiving a wireless signal, performed by a first communication node, may comprise: storing a wireless signal received by the first communication node as samples in a buffer; performing partial correlation operations on the stored samples by a plurality of partial correlators; performing a first FFT operation on results of the partial correlation operations; performing a cumulative product operation on results of the first FFT operation; performing a second FFT operation based on a result of the cumulative product operation; and performing synchronization estimation based on the results of the first FFT operation and a result of the second FFT operation.

Abstract: An ultra-low power data transmission method and apparatus are disclosed. An ultra-low power data transmission method to be performed by a user terminal of an ultra-low power data transmission system includes performing channel coding on a payload included in a transmission packet; interleaving a payload obtained through the channel coding, spreading the interleaved payload using a gold code and an orthogonal variable spreading factor (OVSF), combining a synchronization header spread using the gold code and the OVSF with the spread payload, and modulating a transmission packet in which the payload and the synchronization header are combined.

Abstract: Disclosed is a communication method of a satellite and a ground station and apparatuses performing the same. The communication method includes transmitting a plurality of frames to a satellite based on a beam hopping time plan (BHTP) of the satellite and a ground station and synchronizing the BHTP based on an index of a frame received through a beam switching window (BSW) allocated to the ground station among the plurality of frames, and an identification value indicating at least one sub-frame included in the frame.

Abstract: Disclosed is a communication method performed between a satellite and a ground station and apparatuses performing the communication method. The communication method includes transmitting a plurality of frames based on a beam allocation time schedule (BATS) between a satellite and a ground station, and synchronizing the BATS based on a reception time and a detection time of one or more frames among the plurality of frames to be received through a beam open window (BOW) allocated to the ground station.

Abstract: Disclosed is a communication method of a satellite and a ground station and apparatuses performing the same. The communication method includes transmitting a plurality of frames to a satellite based on a beam hopping time plan (BHTP) of the satellite and a ground station and synchronizing the BHTP based on an index of a frame received through a beam switching window (BSW) allocated to the ground station among the plurality of frames, and an identification value indicating at least one sub-frame included in the frame.

Abstract: Disclosed is a communication method performed between a satellite and a ground station and apparatuses performing the communication method. The communication method includes transmitting a plurality of frames based on a beam allocation time schedule (BATS) between a satellite and a ground station, and synchronizing the BATS based on a reception time and a detection time of one or more frames among the plurality of frames to be received through a beam open window (BOW) allocated to the ground station.

Abstract: Disclosed is a star network/mesh network accessing method and apparatus of a terminal in a satellite communication system, the method including receiving time slot resources from a central station and operating in a time division multiple access (TDMA) start network communication mode between the central station and a terminal, transferring, to the central station, a TDMA mesh network connection request message for a destination terminal, receiving traffic burst time plan (TBTP) information corresponding to the TDMA mesh network connection request message from the central station and operating in a TDMA mesh network communication mode between terminals, and switching from the TDMA mesh network communication mode between the terminals to a single channel per carrier (SCPC) mesh network communication mode between the terminals when Voice over Internet Protocol (VoIP) traffic is greater than a threshold.

Abstract: Disclosed is a star network/mesh network accessing method and apparatus of a terminal in a satellite communication system, the method including receiving time slot resources from a central station and operating in a time division multiple access (TDMA) start network communication mode between the central station and a terminal, transferring, to the central station, a TDMA mesh network connection request message for a destination terminal, receiving traffic burst time plan (TBTP) information corresponding to the TDMA mesh network connection request message from the central station and operating in a TDMA mesh network communication mode between terminals, and switching from the TDMA mesh network communication mode between the terminals to a single channel per carrier (SCPC) mesh network communication mode between the terminals when Voice over Internet Protocol (VoIP) traffic is greater than a threshold.

Abstract: Disclosed is a network synchronization apparatus and method of a time division multiple access (TDMA)-based mesh network satellite communication system, the network synchronization method of a terminal in a satellite communication system including receiving timing error information from a central station, generating a mesh superframe start time (SST?) by reversing a sign of the timing error information, and receiving traffic information transmitted by a transmission terminal using the mesh SST?.

Abstract: Disclosed is a network synchronization apparatus and method of a time division multiple access (TDMA)-based mesh network satellite communication system, the network synchronization method of a terminal in a satellite communication system including receiving timing error information from a central station, generating a mesh superframe start time (SST?) by reversing a sign of the timing error information, and receiving traffic information transmitted by a transmission terminal using the mesh SST?.

Abstract: A satellite communication system and a method of cancelling interference in the satellite communication system are disclosed. The method of cancelling interference in the satellite communication system may include receiving a signal by a central station from a terminal via a satellite transponder, estimating, from the signal, a nonlinear characteristic associated with a central station signal transmitted from the central station, and cancelling an interference signal from the signal using the estimated nonlinear characteristic.

Abstract: Provided is an apparatus for an interference signal cancellation of a central station. The apparatus includes: a communication unit; a storage unit configured to store a transmission signal of the central station received via the communication unit; and a signal processor configured to extract first time synchronization information (NCR) of a current time and second time synchronization information (NCR) included in an overlapping signal and calculate a difference value between the two time synchronization information, when the overlapping signal which is an overlapped signal of a terminal station is received on the same channel as a channel of the transmission signal of the central station, and to extract the transmission signal of the central station stored in a previous time in the storage unit based on the difference value and remove an interference signal included in the overlapping signal.

Abstract: Provided is an apparatus for an interference signal cancellation of a central station. The apparatus includes: a communication unit; a storage unit configured to store a transmission signal of the central station received via the communication unit; and a signal processor configured to extract first time synchronization information (NCR) of a current time and second time synchronization information (NCR) included in an overlapping signal and calculate a difference value between the two time synchronization information, when the overlapping signal which is an overlapped signal of a terminal station is received on the same channel as a channel of the transmission signal of the central station, and to extract the transmission signal of the central station stored in a previous time in the storage unit based on the difference value and remove an interference signal included in the overlapping signal.