Abstract: In a satellite and terrestrial integrated communication system in which a satellite communication system and a terrestrial communication system share and use an identical frequency band, an interference to a mobile earth station (MES) of the satellite communication system using an identical frequency by an uplink signal transmitted to a base station of the terrestrial communication system by a user equipment (UE) may be mitigated. When a communication of the MES is requested, a satellite communication apparatus to perform resource block (RB) allocation for a satellite communication in the satellite and terrestrial integrated system may include a controller configured to allocate a first RB to the MES, and a communicator configured to transmit a use notification of the first RB to at least one terrestrial base station located in an interference range of an uplink signal of the MES.

Abstract: Provided is a communication method for downlink transmission with a low peak to average power ratio (PAPR) and compatibility with long-term evolution (LTE)-based downlink transmission in an LTE-based mobile communication system in which the performance degradation may occur due to a high PAPR in multi-carrier transmission caused by non-linearity of a power amplifier in a base station including a satellite, to have the effects of supporting a terminal that reuses an existing terrestrial LTE chipset and a terminal that enables downlink reception with a low PAPR with no collision between the terminals, and of implementing an integrated satellite/terrestrial mobile communication system with a minimum change of an existing mobile communication system to ensure economic efficiency.

Abstract: A random access method in a mobile communication system, the random access method for supporting random access with a cell size of about 100 kilometers (km) or more and a power limited terminal, and a preamble structure thereof are provided. While a conventional long term evolution (LTE) random access preamble sequence is reused, a difference in a round-trip delay time between terminals in a large cell area may be compensated. Additionally, since higher power transmission is achieved per bandwidth, a higher link margin may be secured. Also, compatibility with resource scheduling of the conventional LTE may be maintained. Random access may be supported in a large cell, and a preamble structure of a satellite mobile communication may be implemented based on terrestrial LTE.

Abstract: In a satellite and terrestrial integrated communication system in which a satellite communication system and a terrestrial communication system share and use an identical frequency band, an interference to a mobile earth station (MES) of the satellite communication system using an identical frequency by an uplink signal transmitted to a base station of the terrestrial communication system by a user equipment (UE) may be mitigated. When a communication of the MES is requested, a satellite communication apparatus to perform resource block (RB) allocation for a satellite communication in the satellite and terrestrial integrated system may include a controller configured to allocate a first RB to the MES, and a communicator configured to transmit a use notification of the first RB to at least one terrestrial base station located in an interference range of an uplink signal of the MES.

Abstract: Provided is a power control and link adaptation method for compensating for a long round trip delay time and slow channel fading in a long term evolution (LTE)-based mobile communication system having a long round trip delay time, similar to a satellite mobile system, the method that may compensate for the long round trip delay time of the satellite mobile system in which a distance between a base station and a terminal is relatively long, when compared to a terrestrial LTE system, support a modulation and coding scheme (MCS) level requested by a terminal, by predicting a channel after the round trip delay time elapses, maintain compatibility within an existing LTE frame, by generating a transmit power control (TPC) instruction for an uplink closed-loop power control, on a frame by frame basis, and compensate for slow channel fading of the satellite mobile system.

Abstract: A transmission apparatus and method for implementing frequency selectivity in a multi-beam satellite system that transmits a signal to user equipment through one or more antenna feed groups. The transmission apparatus includes: an antenna feed group selecting unit configured to select one or more antenna feed groups from the one or more antenna feed groups; a cyclic delay offset determining unit configured to determine a cyclic delay offset according to a determination result of the antenna feed group selecting unit; and a transmitting unit configured to apply the cyclic delay offset determined by the cyclic delay offset determining unit to a signal to be transmitted through the one or more antenna feed groups selected by the antenna feed group selecting unit, and to transmit a resultant signal.

Abstract: Disclosed are an apparatus and a method for normally receiving data by accurately estimating and compensating for a frequency offset for a wireless frequency channel through which data are transmitted in a communication system under wireless frequency environment. In the present invention, data transmitted through the wireless frequency channel are received, the frequency offset in the wireless frequency channel from the receive data is estimated based on an interpolation scheme using the periodogram, and the frequency offset is compensated to receive the data by frequency-synchronizing with the wireless frequency channel.

Abstract: A random access method in a mobile communication system, the random access method for supporting random access with a cell size of about 100 kilometers (km) or more and a power limited terminal and a preamble structure thereof are provided. While a conventional long term evolution (LTE) random access preamble sequence is reused, a difference in a round-trip delay time between terminals in a large cell area may be compensated. Additionally, since higher power transmission is achieved per bandwidth, a higher link margin may be secured. Also, compatibility with resource scheduling of the conventional LTE may be maintained. Random access may be supported in a large cell, and a preamble structure of a satellite mobile communication may be implemented based on terrestrial LTE.

Abstract: Provided is a power control and link adaptation method for compensating for a long round trip delay time and slow channel fading in a long term evolution (LTE)-based mobile communication system having a long round trip delay time, similar to a satellite mobile system, the method that may compensate for the long round trip delay time of the satellite mobile system in which a distance between a base station and a terminal is relatively long, when compared to a terrestrial LTE system, support a modulation and coding scheme (MCS) level requested by a terminal, by predicting a channel after the round trip delay time elapses, maintain compatibility within an existing LTE frame, by generating a transmit power control (TPC) instruction for an uplink closed-loop power control, on a frame by frame basis, and compensate for slow channel fading of the satellite mobile system.

Abstract: Provided is a communication method for downlink transmission with a low peak to average power ratio (PAPR) and compatibility with long-term evolution (LTE)-based downlink transmission in an LTE-based mobile communication system in which the performance degradation may occur due to a high PAPR in multi-carrier transmission caused by non-linearity of a power amplifier in a base station including a satellite, to have the effects of supporting a terminal that reuses an existing terrestrial LTE chipset and a terminal that enables downlink reception with a low PAPR with no collision between the terminals, and of implementing an integrated satellite/terrestrial mobile communication system with a minimum change of an existing mobile communication system to ensure economic efficiency.

Abstract: Disclosed are an apparatus and a method for normally receiving data by accurately estimating and compensating for a frequency offset for a wireless frequency channel through which data are transmitted in a communication system under wireless frequency environment. In the present invention, data transmitted through the wireless frequency channel are received, the frequency offset in the wireless frequency channel from the receive data is estimated based on an interpolation scheme using the periodogram, and the frequency offset is compensated to receive the data by frequency-synchronizing with the wireless frequency channel.

Abstract: Disclosed is a communication method of a satellite mobile communication system. The communication method of a satellite mobile communication system, includes: receiving system information indicating frame intervals in which first user equipments using a satellite radio interface in commonality with a terrestrial radio interface do not perform communications from a base station; accessing the base station in the rest frame intervals other than frame intervals in which the first user equipments do not perform communications, based on the system information; transmitting the system information from the base station to second user equipments using a satellite radio interface optimized for satellite environment; and accessing the base station in the rest frame intervals based on the system information received in the second user equipments.

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: According to the present invention, a random access method between a terminal and a base station comprises: a system information transmission step in which the base station transmits, to the terminal, system information including route values sequentially selected from among a set of routes; a random access preamble transmission step in which the terminal generates a random access preamble on the basis of the system information and transmits the generated random access preamble to the base station; a period setup step in which the base station sets a period available for an arrival of the random access preamble; and a random access preamble detection step in which the base station detects the random access preamble in said available period.

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: 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: 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: A transmission apparatus and method for implementing frequency selectivity in a multi-beam satellite system that transmits a signal to user equipment through one or more antenna feed groups. The transmission apparatus includes: an antenna feed group selecting unit configured to select one or more antenna feed groups from the one or more antenna feed groups; a cyclic delay offset determining unit configured to determine a cyclic delay offset according to a determination result of the antenna feed group selecting unit; and a transmitting unit configured to apply the cyclic delay offset determined by the cyclic delay offset determining unit to a signal to be transmitted through the one or more antenna feed groups selected by the antenna feed group selecting unit, and to transmit a resultant signal.

Abstract: A communication method and apparatus using a symbol interleaver in a long term evolution (LTE)-based satellite communication system are provided. The communication method may include determining whether to use an interleaver based on service information, and interleaving the data using the symbol interleaver designed based on interleaver information. Also, the communication method may include generating random data using a timer and interleaving the random data.

Abstract: Disclosed is a communication method of a satellite mobile communication system. The communication method of a satellite mobile communication system, includes: receiving system information indicating frame intervals in which first user equipments using a satellite radio interface in commonality with a terrestrial radio interface do not perform communications from a base station; accessing the base station in the rest frame intervals other than frame intervals in which the first user equipments do not perform communications, based on the system information; transmitting the system information from the base station to second user equipments using a satellite radio interface optimized for satellite environment; and accessing the base station in the rest frame intervals based on the system information received in the second user equipments.