Abstract: The present invention relates to a communication method in a mobile communication system. An exemplary embodiment of the present invention provides a mobile satellite communication system having a complementary terrestrial component among various mobile communication systems. The mobile satellite communication system can simultaneously provide a communication service and a broadcasting service to a terminal according to integration between communication and broadcasting. Different signal transmission methods are used between the complementary terrestrial component and a satellite. Specifically, a time division duplex method and a frequency division duplex method are used together and resources are allocated. As a result, system throughput can be increased, and local broadcasting contents can be effectively transmitted to the terminal.

Abstract: An apparatus and method for phase recovery in a wireless communication system employs independently decodable component codes. The apparatus includes a decoding unit for decoding the input signal to thereby output the decoding value; an estimation unit for estimating phase errors of the received signal by estimating phase errors of the each component codeword in the received signal to thereby generate phase error estimation values; and a correction unit for correcting the phase of received signal using the phase error estimation values to thereby generate the phase corrected signal in an effective manner.

Abstract: The present invention relates to a method of transmitting a signal in a satellite communication system with a terrestrial component. The present invention transmits a signal using a method of transmitting a space-time code for joint communication between a satellite and a terrestrial component in a satellite system with a terrestrial component. Therefore, using the method of transmitting a space-time code, it is possible to obtain a space-time diversity gain in a satellite communication system with a terrestrial component. Further, it is possible to improve the receiving quality of a satellite signal at an area where the terrestrial component is located and increase the coverage of the terrestrial component.

Abstract: The present invention relates to a system and method of reusing radio resources capable of improving radio resource efficiency. According to an embodiment of the present invention, in a communication system including a repeater that retransmits signals transmitted from a satellite to user terminals, it is possible to reuse some of the radio resources used in a wide area coverage, such as the satellite, in a repeater coverage. Therefore, it is possible to ensure radio resources such that repeater data can be transmitted to user terminals without additional radio resources.

Abstract: The present invention is directed to a method of changing a transmission mode, a method of requesting a packet retransmission, and a method of retransmitting a packet with respect to a broadcasting or multicast service. According to the invention, a plurality of terminals provided with one broadcasting or multicast service shares one random access channel (RACH) so as to transmit channel information. Accordingly, a base station receives the channel information through one RACH from the terminal or detects a packet collision generated in the RACH to confirm a request for changing the transmission mode or a request for maintaining the transmission mode by the terminal.

Abstract: Provided is a device for tracking polarizations. A receiving polarization tracking device includes a feeder for finding vertical and horizontal vector components by receiving vertical and horizontal polarizations, a polarization estimator for estimating distortion of polarizations using the vertical and horizontal vector components outputted from the feeder, a polarization controller for controlling amplitudes and phases of vertical and horizontal polarizations based on information about the estimated distortion from the polarization estimator and an output signal from the receiving polarization tracking device, and a combiner for combining the vertical and horizontal polarizations controlled from the polarization controller.

Abstract: Provided is a method of establishing an uplink in a mobile satellite communication system, the method including: receiving a random uplink access signal from terminals included in a coverage of a satellite beam; estimating a location of each of the terminals; calculating an uplink transmission point in time when each of the terminals transmits an uplink signal, based on the estimated location of each of the terminals; transmitting, to each of the terminals, the calculated uplink transmission point in time; and receiving the uplink signal from each of the terminals at the calculated uplink transmission point in time.

Abstract: A disclose is a frequency sharing apparatus and method for a mobile satellite service using a satellite and a CGC of the satellite. The frequency sharing method may include measuring a signal strength of a signal received from a satellite, determining a communication mode according to the measured signal strength; and communicating with one of the satellite and a CGC of the satellite, depending on the communication mode.

Abstract: Disclosed is a hierarchical random access method for a wireless communication system having a significantly large cell. According to the present invention, a length of a preamble sequence and a length of a reference slot may be designed based on a terminal having greatest capacity of adjusting a timing error arrived at a base station, and a slot length may be designed to be an integer multiple of the length of the reference slot depending on a timing error correction capacity, thereby enabling terminals to use various slot lengths.

Abstract: Disclosed is an interaction method between an automatic repeat request (ARQ) and a hybrid automatic repeat request (HARQ) in a system having a long roundtrip delay. A transmission window for the ARQ is operated using inner feedback information from the HARQ, and a waiting window is operated using ARQ status information.

Abstract: Provided is a communication method of a mobile terminal in an orthogonal frequency division multiplexing (OFDM) based multi-beam satellite system reusing the same frequency band for all the beams, the method including: receiving location information of the mobile terminal from a satellite to determine a location of the mobile terminal within multiple beams; determining a subcarrier group for a communication with the satellite according to the location of the mobile terminal within the multiple beams; and communicating with the satellite using the subcarrier group for the communication with the satellite.

Abstract: Disclosed are a non geostationary satellite orbit (NGSO) communication apparatus that extends an operation time using an ancillary territory component (ATC) and reduces a number of satellites, and an ATC and an operating method thereof. The NGSO communication apparatus for extending an operation time using an ATC and reducing a number of satellites may include a first ATC that communicates with a mobile earth station (MES), and a second ATC that communicate with the first ATC to relay data between the MES and the satellite when the first ATC is unable to communication with the satellite revolving along an orbit.

Abstract: Provided is a method for preventing consecutive packet errors in a transmitter by combining a hybrid automatic repeat request (HARQ) type II with a selective automatic repeat request (ARQ), including: transmitting a data packet from the transmitter to a receiver; when a negative acknowledgement (NACK) packet corresponding to the data packet is received from the receiver, checking stored information in the NACK packet wherein the stored information represent whether or not the data packet is stored in a buffer; when the data packet is stored in the buffer, transmitting a packet having parity bits to the receiver and storing the data packet in a retransmission queue; and when the data packet is not stored in the buffer, re-transmitting the data packet and maintaining the data packet stored in a transmission queue.

Abstract: Provided are a time synchronization method and a frequency offset estimation method using the same in an OFDM system. The time synchronization method using a preamble transmitted from a transmitter to a receiver in the OFDM communication network includes the steps of: a) calculating a moving sum of a first sequence and a second sequence obtained by a product of neighboring elements in a received signal when the received signal containing a preamble is received from the transmitter; b) estimating a location of the received signal corresponding to the moving sum having a maximum value; and c) acquiring a time synchronization with respect to the received signal, based on the estimated location, wherein the first sequence is obtained from a product of neighboring elements in the preamble and a correlation value obtained by correlating another sequence with the first sequence is smaller than a predetermined value.

Abstract: Provided is a satellite communication system for obtaining a diversity gain by transmitting a signal applied with STBC. When a signal transmission band of a link between a satellite and a terminal differs from that of a link between a satellite and a repeater, the satellite communication system includes: a satellite for transmitting a first signal encoded to STBC using a band of a link formed between the satellite to a terminal and transmitting a second signal encoded to STBC using a band of a link formed between the satellite to a repeater; and at least one of frequency transforming repeaters for receiving the second signal through the band of the link formed between the satellite to the repeater, transforming the received second signal to a signal with other frequency band, and transmitting the transformed second signal using a band of a link formed to a terminal.

Abstract: Provided are a method and mobile communication terminal for handover in a mobile communication network including at least one mobile communication base station and a communication satellite.

Abstract: An apparatus and method for phase recovery in a wireless communication system employs independently decodable component codes. The apparatus includes a decoding unit for decoding the input signal to thereby output the decoding value; an estimation unit for estimating phase errors of the received signal by estimating phase errors of the each component codeword in the received signal to thereby generate phase error estimation values; and a correction unit for correcting the phase of received signal using the phase error estimation values to thereby generate the phase corrected signal in an effective manner.

Abstract: A power control system and method for communication system using space-time transmit diversity scheme. In the power control method, transmission power information of a plurality of antennas or a plurality of subcarriers is monitored. A new space-time code is generated by concatenating the monitored transmission power information and symbols to be transmitted. Symbols encoded using the generated space-time code are generated and the encoded symbols are transmitted. Accordingly, after determining the transmission power of each antenna, the transmission power information is monitored so that the transmission power information that does not experience the channel gain can be used at a next slot. Therefore, the performance degradation due to the round trip time can be reduced, thereby improving the system capacity and performance.

Abstract: There is provided a method for packet scheduling in a selective hybrid automatic repeat request (HARQ) including the steps of: increasing a priority of a receiver buffer after a packet is transmitted to the receiver; receiving a feedback packet for the transmitted packet and determining whether the feedback packet is an ACK packet or a NACK packet; lowering the priority of the receiver buffer if the feedback packet is an ACK packet; determining whether the feedback packet is a NACK packet for initial transmission or the feedback packet is a NACK packet for retransmission if the feedback packet is the NACK packet, increasing the priority of the receiver buffer if the feedback packet is the NACK packet for the initial transmission, and lowering the priority of the receiver buffer if the feedback packet is the NACK packet for retransmission; and scheduling packets after calculating a priority of each receiver buffer by performing the priority increasing step to the determining step for all of receivers.

Abstract: A multi-beam transmitting and receiving apparatus in a wireless communication system includes a plurality of transmitting beam forming units for forming timely-divided multiple beams, each of the timely-divided multiple beams having a period of a total number of time division NTD at every time TD when the beams are activated; and a beam controller for controlling the transmitting beam forming units to select an arbitrary beam forming unit of a plurality of the transmitting beam forming units according to information about the time division, wherein the number of the beam forming units is determined as the total number of the beams NBM divided by the number of time division NTD.