Abstract: A relay wireless communication system is provided. A Relay Station (RS) includes a buffer for storing packets to be sent to at least one Mobile Station (MS); a scheduler for allocating resources to the at least one mobile station of which the packets are stored to the buffer; a generator for generating a message which comprises information about at least one mobile station of which packets are not stored to the buffer; and a communicator for sending the message to a Base Station (BS) and sending the packets stored to the buffer to the at least one mobile station allocated the resources.

Abstract: An apparatus and a method for selecting one of a plurality of relay modes in a wireless communication system are provided. The method includes checking a channel state between a Mobile Station (MS) and each of at least one Relay Station (RS), selecting the relay mode for supporting a relay service using the determined channel state between the MA and each of the at least one RS, and providing the relay service to the MS using the selected relay mode. Thus, system throughput and outage performance can be enhanced by using the appropriate relay mode based on the MS distribution or the channel condition.

Abstract: A transmitter for a mobile communication system based on an OFDM scheme and a method for controlling the same. The transmitter can implement a characteristic of a multiple access scheme based on an OFDM scheme, a characteristic of a CDMA scheme, and a characteristic of a frequency hopping scheme which has very strong resistance to the frequency selective fading.

Abstract: A transceiver system and method in an OFDM communication system which enables exact symbol synchronization acquisition and improves performance for frequency offset and channel estimation. In the apparatus, a guard interval filling unit copies data at a predetermined interval in an input data row inputted to be transmitted, and fills in the copied data in the preset guard interval in the input data row. A selection unit selectively receives an output data row outputted from the guard interval filling means and unique words having a constant amplitude and a non-periodic auto-correlation characteristic, and outputs the OFDM symbol in which the unique words are inserted in the output data row.

Abstract: A method for controlling a sleep mode operation by a mobile station (MS) in a communication system. In the sleep mode operation control method, after entering a sleep mode, the MS transitions to an awake state in a listening interval. When there is data to transmit or receive to/from a base station (BS) in the awake state, the MS causes a neutral interval following the listening interval to transition to the awake state, and transmits or receives the data. The neutral interval is an interval where transition to the awake state and sleep state is available according to the data transmission/reception of the MS operating in the sleep mode.

Abstract: An apparatus and method for communicating channel information in a relay wireless communication system are provided. A Base Station (BS) apparatus includes a message generator for generating a channel measurement request message to be transmitted to a Relay Station (RS) when the RS is connected; a Transmit (TX) modem for performing a physical layer processing on a message generated by the message generator and for transmitting the processed message; a message analyzer for analyzing a channel measurement response message received from the RS and for obtaining channel estimation information; and a scheduler for performing data scheduling by using the channel estimation information for a predetermined duration corresponding to a plurality of frames.

Abstract: An apparatus and method for providing a relay service in an OFDM mobile communication system are provided, in which symbol synchronization is acquired from a received OFDM signal, an OFDM signal is acquired using the symbol synchronization, and a relay signal is reconfigured by removing a cyclic prefix from the acquired OFDM signal, amplifying the relay signal, and transmitting the relay signal.

Abstract: An apparatus for generating a preamble sequence in an orthogonal frequency division multiplexing (OFDM) communication system using A subcarriers in a frequency domain. A preamble sequence generator generates a length?M+N+k preamble sequence, where M+N+k is less than A, by combining a length?N Golay complementary sequence with a length?M Golay complementary sequence. An inverse fast Fourier transform (IFFT) processor assigns elements constituting the preamble sequence to the M+N+k subcarriers among the A subcarriers on a one-to-one mapping basis, assigns null data to remaining subcarriers excluding the M+N+k subcarriers from the A subcarriers, and then IFFT-transforms the assigned result into time-domain data.

Abstract: A method for generating a preamble sequence in an orthogonal frequency division multiplexing (OFDM) communication system having A subcarriers in a frequency domain. The method comprises generating a length-2×M×N preamble sequence, where 2×M×N is less than A, by using a length-N Golay complementary sequence and a length-M Golay complementary sequence; and assigning elements constituting the preamble sequence to 2×M×N subcarriers among the A subcarriers on a one-to-one mapping basis, assigning null data to the remaining subcarriers excluding the 2×M×N subcarriers from the A subcarriers, and then IFFT-transforming the assigned result into time-domain data.

Abstract: A mobile communication system for modulating input data with a specific size into an OFDM (Orthogonal Frequency Division Multiplexing) symbol and transmitting the OFDM symbol through at least two different antennas. A replica generator generates replica data by cyclically-circulating the input data. An encoder generates a first antenna signal and a second antenna signal by encoding the input data and the replica data. A first IFFT (Inverse Fast Fourier Transform) block generates a first OFDM symbol by performing IFFT on the first antenna signal, and a second IFFT block generates a second OFDM symbol by performing IFFT on the second antenna signal. A first antenna transmits the first OFDM symbol, and a second antenna transmits the second OFDM symbol.

Abstract: In a mobile communication system, a relay station (RS) is used for signal exchange with a base station (BS), and includes a first antenna set including at least one antenna, used for signal exchange with the BS, and a second antenna set including at least one antenna, used for signal exchange with a mobile station (MS). The RS selects at least one antenna from the second antenna set for each of the at least one MS, and exchanges a signal with the MS using the selected at least one antenna.

Abstract: Provided is an apparatus and method for providing a synchronous relay service in a multi-hop relay BWA communication system. In the method, a BS-MS link subframe and an RS-MS link subframe are configured for a first section of a subframe in an ith frame. At least one of a BS-RS link subframe, an RS-RS link subframe and an RS-MS link subframe is configured for a second section of a subframe in the ith frame. The BS-MS link subframe and the RS-MS link subframe are configured for a first section of a subframe in an (i+1)th frame. At least one of the BS-RS link subframe, the RS-RS link subframe and the RS-MS link subframe is configured for a second section of a subframe in the (i+1)th frame.

Abstract: An apparatus and method of providing relay service in a broadband wireless access (BWA) communication are provided. The communication method includes dividing an entire frequency band into a plurality of bands to support a plurality of links; determining subcarrier allocation schemes for the divided bands independently from one another; and communicating using the determined subcarrier allocation schemes by the plurality of the links. When the direct link and the relay link are distinguished through the frequency multiplexing in the multihop relay BWA communication system, the present invention enables the independent channel estimation from the relay link by adopting the dedicated pilot based permutation scheme for the relay link.

Abstract: A apparatus and method for estimating a channel condition of a forward link by a mobile station in a mobile communication system including the mobile station and a base station for performing an operation of transmitting/receiving data using a plurality of subcarriers having mutual orthogonality. The method comprises measuring carrier-to-interference ratio (C/I) values of the subcarriers using a signal received from the base station; determining from the received signal a subcarrier for transmitting feedback information in a given coherence bandwidth; generating feedback information to be transmitted over the determined subcarrier; and transmitting the generated feedback information to the base station as information for estimating a channel condition of the forward link.

Abstract: Disclosed herein is a ranging method for a mobile communication system based on an OFDMA (Orthogonal Frequency Division Multiple Access) scheme. In the communication system for classifying a ranging procedure between a transmission side and reception sides into an initial ranging process, a bandwidth request ranging process, and a periodic ranging process, the ranging method includes the steps of determining the number of initial RCs(ranging codes) for the initial ranging process, the number of bandwidth request RCs for the bandwidth request ranging process, and the number of periodic RCs for the periodic ranging process, determining a backoff value of the periodic RCs according to the number of the periodic RCs, and sending the initial RCs, the bandwidth request RCs, the periodic RCs, and the backoff value of the periodic RCs to the reception sides.

Abstract: Apparatus and method for performing Automatic Retransmission reQuest (ARQ) in a wireless relay communication system are provided, which include performing ARQ with the base station (BS), transmitting data successfully received from the BS to mobile station (MS), and retransmitting corresponding data to the MS when a retransmission indication message is received from the BS. Since the relay station (RS) relays only the errorless data to the receiver, the reliability of the data received at the receiver can be enhanced. The load on the RS can be reduced because the transmitter controls the ARQ.

Abstract: An apparatus and method for performing Automatic Retransmission reQuest (ARQ) of a Relay Station (RS) in a wireless communication system using a relay scheme are provided. The method includes receiving data from a transmitter and transmitting the received data to one or more receivers; and receiving Acknowledgment (ACK)/Negative-Acknowledgment (NACK) information for the data received from the one or more receivers and transmitting the received ACK/NACK information to a Base Station (BS).

Abstract: A mobile communication system for modulating input data with a specific size into an OFDM (Orthogonal Frequency Division Multiplexing) symbol and transmitting the OFDM symbol through at least two different antennas. A replica generator generates replica data by cyclically-circulating the input data. An encoder generates a first antenna signal and a second antenna signal by encoding the input data and the replica data. A first IFFT (Inverse Fast Fourier Transform) block generates a first OFDM symbol by performing IFFT on the first antenna signal, and a second IFFT block generates a second OFDM symbol by performing IFFT on the second antenna signal. A first antenna transmits the first OFDM symbol, and a second antenna transmits the second OFDM symbol.

Abstract: An apparatus and method is disclosed for frequency reuse to avoid interference between a Relay Station (RS) and a Mobile Station (MS) in a multi-hop relay system. The method includes measuring a preamble signal strength of a serving RS, measuring a preamble signal strength of a neighboring RS, and computing a preamble signal strength ratio using the preamble signal strength of the serving RS and the preamble signal strength of the neighboring RS.

Abstract: An apparatus and method for negotiating a relay service function of a relay station (RS) in a multihop relay Broadcast Wireless Access (BWA) communication system are provided. The method includes transmitting a first message containing function information supportable by an RS to a serving station, confirming the RS supportable function using the first message received from the RS, transmitting a second message containing relay service function information to be performed by the RS to the RS, and executing the relay service according to the RS service information of the second message.