Patent ID: 7609609

Claim:
An apparatus for processing a digital signal in a transmitter of an orthogonal frequency division multiple access (OFDMA) wireless communication system, the apparatus comprising: a memory for storing a number of allocated subcarriers and an inverse discrete Fourier transform (IDFT) coefficient; an inverse fast Fourier transform (IFFT) block for determining each of a bitwidth for the IDFT coefficient and a bitwidth for data according to the number of the allocated subcarriers, and performing multiplication calculations on the IDFT coefficient and the data; and a controller for outputting a mode selection signal indicating a transmission mode or a reception mode to the IFFT block, wherein the IDFT coefficient is defined by the following equation: x ⁡ [ n ] = ∑ k = 0 N - 1 ⁢ s ⁡ ( k ) ⁢ ⅇ j ⁢ ⁢ 2 ⁢ ⁢ π / Nkn ≤ ∑ k = 0 N - 1 ⁢  s ⁡ ( k )  ⁢  ⅇ j ⁢ ⁢ 2 ⁢ ⁢ π / Nkn  = ∑ k = 0 N - 1 ⁢ s ⁡ ( k ) ≤ N ⁢ ⁢ max ⁢ ⁢  s ⁡ ( k )  wherein x[n] denotes the IDFT coefficient, n denotes an orthogonal frequency division multiplexing (OFDM) symbol index, N denotes the number of the allocated subcarriers, s(k) denotes an input signal to the IFFT block, and k denotes a subcarrier index.