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 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 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 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 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: An apparatus for generating a network clock reference (NCR) packet for acquiring network synchronization between satellite communication devices in two-way satellite communication system, the apparatus including a clock reference determiner configured to determine an NCR based on a trigger signal with respect to a start of a first frame, a synchronization compensator configured to determine a synchronization compensation value by reflecting frame variable length information from the first frame to a second frame into which an NCR packet is to be inserted, and a packet generator configured to generate the NCR packet by combining the NCR and the synchronization compensation value, is provided.

Abstract: Provided is a system and method for synchronization between digital-to-analog converters (DAC) for high speed signal processing. A synchronization method of a multi-DAC apparatus may include: inputting a clock to a multiplexer (MUX) DAC; dividing the clock into a first clock and a second clock; transferring a phase difference between the first clock and the second clock to a D flip-flop; and synchronizing the first clock and the second clock by processing the phase difference.

Abstract: Provided is a system and method for synchronization between digital-to-analog converters (DAC) for high speed signal processing. A synchronization method of a multi-DAC apparatus may include: inputting a clock to a multiplexer (MUX) DAC; dividing the clock into a first clock and a second clock; transferring a phase difference between the first clock and the second clock to a D flip-flop; and synchronizing the first clock and the second clock by processing the phase difference.