Abstract: A communication method according to the present invention includes receiving MAP in formation, acquiring an initial scheduled frame number and a current frame number from the MAP information, calculating the difference between the initial scheduled frame number and the current frame number, comparing the difference between the initial scheduled frame number and the current frame number with a reference value and setting a scheduled frame number, and performing transmission or reception in the scheduled frame. Therefore, even though a MAP loss occurs, the mobile station can receive only downlink data effective in downlink, thereby reducing power consumption for unnecessary reception, and can exactly perform transmission in a frame in which it should transmit in uplink.

Abstract: A method of transmitting a signal according to the present invention includes: receiving a signal that is encoded with a predetermined code rate and that is modulated by a first modulation method from a base station; creating a signal that is obtained by demodulating the signal that is modulated by the first modulation method using a method corresponding to the first modulation method; creating a signal that is obtained by modulating the demodulated signal using a second modulation method while maintaining the predetermined code rate; and transmitting the signal that is modulated by the second modulation to a mobile station. Therefore, it is possible to reduce the cost of the relay station and simplify the system of the relay station. Further, during the modulation and demodulation, the symbol offset is changed to create various modulated and demodulated signals.

Abstract: The present invention relates to a URL providing apparatus and a method thereof, and a mobile station that accesses the Internet by using the provided URL, and an Internet access method thereof. The mobile station attaches an RF-ID tag that stores an RF-ID tag value corresponding to identification information of the mobile station thereto, and thus when a user brings the mobile station into an interrogation range of an RF-ID reader included in the URL providing apparatus, the URL providing apparatus receives the corresponding RF-ID tag value from the RF-ID reader. When the URL providing apparatus acquires an IP address of the mobile station by using the received RF-ID tag value and provides a URL to the mobile station by using the acquired IP address, the mobile station automatically accesses the Internet by using the URL. Such an Internet access method can minimize additional cost of the mobile station and simplify an Internet access process to a specific URL.

Abstract: A subcarrier allocating apparatus allocating data to be transmitted to a plurality of orthogonal subcarriers in an orthogonal frequency division multiplexing (OFDM) system is provided. The apparatus includes a logical index generator generating a logical index for allocating a data subcarrier to a physical index, the logical index being included with only data subcarriers and the physical index indicating a location of a substantial subcarrier within a symbol, an intermediate index converter converting the logical index into an intermediate index by performing a given operation on the generated logical index and a pilot location constant, and a physical index converter converting the intermediate index into a physical index based on the number of data subcarriers on the left and right sides of a null subcarrier for insertion of a guard interval formed by the null subcarrier.

Abstract: In a decoding apparatus in a portable Internet terminal, a channel encoded symbol received from a transmitter is decoded by one of a chase-combining scheme and a code-combining scheme selected based on an ID value of the subpacket indicating a start position of the symbol. In this case, the chase-combining scheme is partly used for the encoded symbol of the information bit. With such a mode, decoding can be performed at a low code rate.

Abstract: Disclosed is a demodulation apparatus for receiving signals by an adaptive modulation and coding method, and demodulating the signals, in an OFDMA based packet communication system, comprising: a QAM demapper for performing QAM demapping to the received signals by a modulation method using a maximum modulation ratio, until modulation methods for each of sub-channels are analyzed; a slot buffer for storing the data outputted from the QAM demapper; a channel decoder for decoding the data stored in the slot buffer and analyzing modulation methods for each sub-channels and transferring the analyzed modulation methods to the QAM demapper; and in at the same time, reading valid data from the data stored in the slot buffer, based on the analyzed modulation methods for each sub-channels, and demodulating the valid data.

Abstract: The present invention relates to a decoder for tail-biting convolution codes and a method thereof. The decoder receives an encoding bit sequence in a convolutional encoding method from a channel, generates an expanded encoding bit sequence, Viterbi decodes the expanded encoding bit sequence, and generates decoded data. In addition, the decoder selects a central bit sequence of the decoded data, rearranges the central bit sequence, and generates final decoded data. Accordingly, the decoder has a simplified configuration for decoding the bit sequence encoded in the tail biting convolutional encoding method, and the decoder also decodes a bit sequence encoded in a zero-tail convolutional encoding method.

Abstract: The present invention provides an LDPC encoder, a channel encoder of a portable internet system including the LDPC encoder, and an encoding method thereof. The LDPC encoder according to the present invention generates a Costas array, shifts it, generates an analogous circulation parity check matrix having a repeated pattern from the shifted Costas array, and performs encoding by using the parity check matrix. With this LDPC encoder, complexity of encoding system may be reduced.

Abstract: A method of transmitting a signal according to the present invention includes: receiving a signal that is encoded with a predetermined code rate and that is modulated by a first modulation method from a base station; creating a signal that is obtained by demodulating the signal that is modulated by the first modulation method using a method corresponding to the first modulation method; creating a signal that is obtained by modulating the demodulated signal using a second modulation method while maintaining the predetermined code rate; and transmitting the signal that is modulated by the second modulation to a mobile station. Therefore, it is possible to reduce the cost of the relay station and simplify the system of the relay station. Further, during the modulation and demodulation, the symbol offset is changed to create various modulated and demodulated signals.

Abstract: A communication method according to the present invention includes receiving MAP in formation, acquiring an initial scheduled frame number and a current frame number from the MAP information, calculating the difference between the initial scheduled frame number and the current frame number, comparing the difference between the initial scheduled frame number and the current frame number with a reference value and setting a scheduled frame number, and performing transmission or reception in the scheduled frame. Therefore, even though a MAP loss occurs, the mobile station can receive only downlink data effective in downlink, thereby reducing power consumption for unnecessary reception, and can exactly perform transmission in a frame in which it should transmit in uplink.

Abstract: The present invention relates to a Viterbi decoder and a Viterbi decoding method in a register exchange method. The Viterbi decoder receives an encoded bit sequence of a convolutional encoding method from a channel, generates an expanded encoded bit sequence by cyclically adding a part of the encoded bit sequence or the entire encoded bit sequence to the encoded bit sequence more than one time, performs a Viterbi decoding operation in a register exchange method, and generates decoded data. In addition, the Viterbi decoder selects an end bit sequence corresponding to the number of the unit of encoded bits among the decoded data, rearranges an order of the end bit sequence, and generates final decoded data.

Abstract: A subcarrier allocating apparatus allocating data to be transmitted to a plurality of orthogonal subcarriers in an orthogonal frequency division multiplexing (OFDM) system, the apparatus including: a logical index generator (142) generating a logical index for allocating a data subcarrier to a physical index, the logical index being included with only data subcarriers and the physical index indicating a location of a substantial subcarrier within a symbol; an intermediate index converter (144) converting the logical index into an intermediate index by performing a given operation on the generated logical index and a pilot location constant; and a physical index converter (146) converting the intermediate index into a physical index based on the number of data subcarriers on the left and right sides of a null subcarrier for insertion of a guard interval formed by the null subcarrier.

Abstract: The present invention relates to a URL providing apparatus and a method thereof, and a mobile station that accesses the Internet by using the provided URL, and an Internet access method thereof. The mobile station attaches an RF-ID tag that stores an RF-ID tag value corresponding to identification information of the mobile station thereto, and thus when a user brings the mobile station into an interrogation range of an RF-ID reader included in the URL providing apparatus, the URL providing apparatus receives the corresponding RF-ID tag value from the RF-ID reader. When the URL providing apparatus acquires an IP address of the mobile station by using the received RF-ID tag value and provides a URL to the mobile station by using the acquired IP address, the mobile station automatically accesses the Internet by using the URL. Such an Internet access method can minimize additional cost of the mobile station and simplify an Internet access process to a specific URL.

Abstract: Provided are a method of relaying a data burst in a relay station (RS) of a multi-hop relay (MMR) system using a direct relay zone, and a system using the method. The RS requests a base station to assign the direct relay zone in a frame in which a demodulation and forwarding scheme that demodulates, and then modulates and transmits a data burst is applied, receives an acknowledgement to the request from the base station, and relays a data burst using the frame in which the direct relay zone is assigned. Accordingly, since a data burst can be relayed within one frame, relay latency can be reduced.

Abstract: The present invention relates to a decoder for tail-biting convolution codes and a method thereof. The decoder receives an encoding bit sequence in a convolutional encoding method from a channel, generates an expanded encoding bit sequence, Viterbi decodes the expanded encoding bit sequence, and generates decoded data. In addition, the decoder selects a central bit sequence of the decoded data, rearranges the central bit sequence, and generates final decoded data. Accordingly, the decoder has a simplified configuration for decoding the bit sequence encoded in the tail biting convolutional encoding method, and the decoder also decodes a bit sequence encoded in a zero-tail convolutional encoding method.

Abstract: In a decoding apparatus in a portable Internet terminal, a channel encoded symbol received from a transmitter is decoded by one of a chase-combining scheme and a code-combining scheme selected based on an ID value of the subpacket indicating a start position of the symbol. In this case, the chase-combining scheme is partly used for the encoded symbol of the information bit. With such a mode, decoding can be performed at a low code rate.

Abstract: The present invention provides an LDPC encoder, a channel encoder of a portable internet system including the LDPC encoder, and an encoding method thereof. The LDPC encoder according to the present invention generates a Costas array, shifts it, generates an analogous circulation parity check matrix having a repeated pattern from the shifted Costas array, and performs encoding by using the parity check matrix. With this LDPC encoder, complexity of encoding system may be reduced.

Abstract: Disclosed is a demodulation apparatus for receiving signals by an adaptive modulation and coding method, and demodulating the signals, in an OFDMA based packet communication system, comprising: a QAM demapper for performing QAM demapping to the received signals by a modulation method using a maximum modulation ratio, until modulation methods for each of sub-channels are analyzed; a slot buffer for storing the data outputted from the QAM demapper; a channel decoder for decoding the data stored in the slot buffer and analyzing modulation methods for each sub-channels and transferring the analyzed modulation methods to the QAM demapper; and in at the same time, reading valid data from the data stored in the slot buffer, based on the analyzed modulation methods for each sub-channels, and demodulating the valid data.

Abstract: The present invention relates to a Viterbi decoder and a Viterbi decoding method in a register exchange method. The Viterbi decoder receives an encoded bit sequence of a convolutional encoding method from a channel, generates an expanded encoded bit sequence by cyclically adding a part of the encoded bit sequence or the entire encoded bit sequence to the encoded bit sequence more than one time, performs a Viterbi decoding operation in a register exchange method, and generates decoded data. In addition, the Viterbi decoder selects an end bit sequence corresponding to the number of the unit of encoded bits among the decoded data, rearranges an order of the end bit sequence, and generates final decoded data.

Abstract: An encoder using LDPC (low density parity check) codes, and an encoding method. The encoder comprises a parity check matrix generator for generating a parity check matrix H; and a codeword generator for processing the parity check matrix H to generate a codeword, and the codeword generator comprises: an AB analyzer for analyzing the parity check matrix H into matrixes A and B; a pivoting unit for pivoting the parity check matrix H; a bit-reversing unit for bit-reversing the pivoted matrix; an LU analyzer for analyzing the matrix A into matrixes L and U; and a codeword generator unit for performing a logical operation on the matrixes A, B, L and U. A bit-reversing method is used to effectively generate a parity check matrix having a high girth by using a regular encoder.