Patent ID: 7257166

Claim:
A data communication apparatus based on orthogonal frequency division multiple access (OFDMA) comprising a first user transmitting unit through which a user transmits user information to a base station in units of first symbol blocks each including a first predetermined number M of symbols in data communication between the user and the base station, the first user transmitting unit comprising: a first encoder for generating a first sub-block composed of a second predetermined number M u of user symbols a k (u) for a u-th user by encoding the user information, where M u is an integer greater than or equal to 1 and no greater than M, “k” is a time index and an integer greater than or equal to 0 and no greater than M−1, “u” is a user index and an integer greater than or equal to 1 and no greater than U, and U indicates the number of users sharing the first symbol block and is 1 or a positive integer greater than 1; a first block repeater for repeating the first sub-block a third predetermined number L u of times to generate M symbols a k′ (u) , wherein L u is M/M u , k′=k % M u , and k % M u indicates the remainder when “k” is divided by M u ; a first multiplier for multiplying the M symbols a k′ (u) generated from the first block repeater by γ u exp(j2πkm u /M) and outputting the result of multiplication as a signal x k (u) for the u-th user, wherein γ u indicates a magnitude control factor for the u-th user signal x k (u) , and m u indicates a unique frequency offset number allocated to the u-th user; a first cyclic extension symbol inserter for outputting the first symbol block completed by inserting a cyclic extension symbol into the u-th user signal x k (u) ; and a first signal transmitter for converting the completed first symbol block into a symbol block signal and transmitting the symbol block signal, wherein M 1 +M 2 +M 3 + . . . +M u does not exceed M where M represents the number of symbols in data communication between the user and the base station, Mu is an integer greater than or equal to 1 and no greater than M, ‘u’ is a user index and an integer greater than or equal to 1 and no greater than U, and U indicates the number of users sharing the first symbol block and is 1 or a positive integer greater than 1.