Samsung Electro-mechanics Co., Ltd.

Osong Medical Innovation Foundation, Korea University Research and Business Foundation

Intellectual Discovery Co., Ltd.

Korea University Industrial Academic Collaboration Foundation

Samsung Electronics Co., Ltd.

Electronics and Telecommunications Research Institute

Young Chai Ko

Chul Gyun Park

Joun Sup Park

Hyun Ho Lee

Kyung Tae Jo

Sung Jin Kim

Sang Hyun Lee

Sun Ho Kim

Myung Sun Song

Gwangzeen Ko

Igor Kim

Tae Jun Lee

Jung Hoon Suh

Jinhyung Oh

Myeong Jin Kim

Yong Hun Jang

Hae Woon Nam

Kyu Sung Hwang

Seung Sik Eom

Byung Ju Lim

Seung Sik Eum

Ju Hyung Lee

Jun Young Seo

Won Young Kang

Disclosed herein are a time synchronization method and apparatus for a low-orbit satellite cluster. The time synchronization method for a low-orbit satellite cluster includes: receiving time information from N participating satellites directly connected; calculating a reference time using time information based on a reliability of each of the N participating satellites; performing time synchronization using the reference time and then recording a synchronization history; and generating a new block using the synchronization history.

Time synchronization method and apparatus for low-orbit satellite cluster

A random access method for a terminal with the processor and the memory to access a low earth orbit satellite network formed by multiple low earth orbit satellites (LEO SAT) includes: the stage where a Deep Reinforcement Learning (DRL) algorithm is applied for a pre-set time to decide which one between the first and the second actions should be performed at every access cycle, and to perform the random access to the low earth orbit satellite network based on the above decision while learning it; and the stage where, according to the learning result of the DRL algorithm performed for above pre-set time, it decides which of the first and the second actions should be chosen when attempting to access the low earth orbit satellite network at a new access cycle and then to perform the random access to the low earth orbit satellite network according to the above choice.

Deep reinforcement learning-based random access method for low earth orbit satellite network and terminal for the operation

Disclosed is a phase noise mitigation method using a MIMO system in which each antenna has an independent oscillator. The phase noise mitigation method includes: receiving a transmission signal transmitted from a transmitting antenna, through a receiving antenna and an oscillator; estimating multiple parameters for a phase noise of a transmission terminal and a phase noise of a receiving terminal on the basis of a result of mathematical modeling of signals transmitted and received through the MIMO system in which each antenna has an independent oscillator; and mitigating phase noises of the transmission terminal and the receiving terminal which are estimated from the received signal.

MIMO systems with independent oscillators and phase noise mitigation method thereof

Disclosed is a method for removing signal interference in a MIMO-based interference removing apparatus including transmitting a reference signal to at least one receiver; if channel information is estimated by the receiver, receiving the estimated channel information from the receiver as a feedback signal; and producing transmission pre-coding matrix, beam forming matrix, and weighted matrix using the received channel information. Further, the method includes transmitting information containing the transmission pre-coding matrix, the beam forming matrix, and the weighted matrix by including them in a pilot signal to the receiver, and the MIMO-based interference removing apparatus comprises at least one transmitter.

Method for removing signal interference based on multiple input multiple output

A method and an apparatus for transmitting and receiving a signal in a communication system are provided. The method includes transmitting a signal to a receiver through one of the antennas, receiving an antenna switching indicator indicating to switch the transmitting antenna from the receiver, and switching the transmitting antenna according to the antenna switching indicator, and transmitting a signal to the receiver through a switched antenna.

Method and apparatus for transmitting and receiving a signal in a communication system

There are provided an apparatus and a method for reducing a peak to average power ratio (PAPR) through the recombination of an orthogonal frequency division multiplexing (OFDM) symbol. The apparatus includes an orthogonal frequency division multiplexing (OFDM) symbol transforming unit, a peak power measuring unit, and an OFDM symbol selecting unit, wherein the OFDM symbol transforming unit generates the plurality of OFDM symbols by (a) performing a process of rotating the OFDM symbol by a predetermined angle in a complex plane and performing cyclical shifting with respect to the rotated OFDM symbol and (b) repetitively performing process (a) with respect to the cyclically shifted OFDM symbol. Therefore, diversity is secured, whereby the PAPR may be reduced.

Apparatus and method for reducing peak to average power ratio through recombination of orthogonal frequency division multiplexing symbol

The present invention relates to a symbol-wise beamforming apparatus and method in an OFDM communication system using multiple antennas. A weight vector calculator calculates a transmit weight vector using a signal received through the multiple antennas as an input on the basis of channel information in the time domain and covariance matrix information about interference and noise and computes a receive weight vector using the calculated transmit weight vector. At least one of the calculated transmit weight vector and receive weight vector is transmitted to a transmission apparatus through a transmitter.

Beamforming apparatus and method in multi-antenna system

Disclosed are a beam forming method and a multiple antenna system using the same. There is provided a multiple antenna system which forms optimal beam patterns through a transmission of a training sequence between a transmitter and a receiver, each including a plurality of antennas, the multiple antenna system comprising: a transmitter selecting antennas to be activated according to a level and transmitting the training sequence to a receiver through the selected antennas; a receiver selecting the antennas to be activated according to the level and transmitting to the transmitter an index of an optimal transmission weight vector significantly reducing a cost function based on the training sequence transmitted from the transmitter, wherein the transmitter selects antennas so that the beam patterns formed by the antennas selected at a q-th level (q: the index of the level) include the beam patterns formed by the antennas selected at a q+1-th level. As a result, the transmission frequency of the training sequence may be reduced.

Beam forming method and multiple antenna system using the same

A multi-antenna system using adaptive beamforming includes a phase shift unit, a signal combination unit, a frequency down-converter, and an analog-to-digital (A/D) converter, and a beamforming control unit. The phase shift unit includes a plurality of phase shifters which shift the phases of signals received from a plurality of antennas. The signal combination unit combines phase-shifted signals output from the plurality of phase shifters. The frequency down-converter down-converts a signal output from the signal combination unit into a baseband signal. The A/D converter converts the baseband signal into a digital signal. The beamforming control unit searches for a weight vector higher than a preset threshold signal-to-noise ratio (SNR) when a reception SNR of the digital signal output from the A/D converter is lower than the threshold SNR, and changes a currently set weight vector into the searched weight vector to provide to the phase shift unit.

Multi-antenna system using adaptive beamforming

A terminal device and a relay node selection method of the terminal device are described. The terminal device may sequentially compare a threshold value and an output signal to noise ratio (SNR) of a plurality of relay nodes based on a set test order, and select a relay node having an output SNR greater than the threshold value as a relay node to perform a cooperative communication.

Terminal device and relay node selection method of terminal device

A beamforming apparatus for a multi-antenna system includes a phase control unit including a plurality of phase shifters which respectively control the phases of signals according to a preset phase weight vector; a signal combination unit combining the signals outputted from the plurality of phase shifters; a frequency down converter down-converting the combined signal outputted from the signal combination unit into a baseband signal; an analog/digital (A/D) converter converting the baseband signal into a digital signal; and a radio frequency (RF) beamforming control unit providing a plurality of preset phase weight vectors to the phase control unit according to a preset application sequence, deciding a maximum signal-to-noise ratio (SNR) among a plurality of SNRs corresponding to the applied phase weight vectors by using the digital signal outputted from the A/D converter, and controlling the beamforming of the phase control unit by using the maximum SNR.

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Seoul, South Korea

Young Chai Ko