Patent ID: 7639660

Claim:
An apparatus for OFDMA (Orthogonal Frequency Division Multiple Access) transmission, which is for coherent detection in an uplink of a wireless communication system supporting multiple subscribers, the apparatus comprising: a channel encoder for channel-encoding a subscriber data block; a symbol mapper for mapping encoded data of the channel encoder into a data symbol; a pilot symbol generator for generating a pilot symbol, the pilot symbol having the same transmission power as the data symbol; a resource-block-based time-frequency mapper for mapping the data symbol output from the symbol mapper and the pilot symbol from the pilot symbol generator into a time-frequency index of an OFDM signal according to a resource-block-based mapping method, the resource-block-based mapping method mapping multiple resource blocks that are well-distributed in time and frequency domains to a channel allocated to a subscriber, each resource block comprising consecutive subcarriers of consecutive OFDM symbols and including at least one pilot symbol and multiple data symbols; and an OFDM modulator for generating an OFDM signal from the mapped output of the resource-block-based time-frequency mapper, wherein each resource block includes a single pilot symbol at the center of the resource block, the size of the resource block determined by R f x R t , where R f and R t satisfy the following expressions: f D T s R t <<½, and τ max Δf/R f <<½, where f D is a maximum Doppler frequency of the channel, T s is a symbol interval, and τ max is the maximum delay time of the channel, and Δf is the subcarrier spacing, or each resource block includes multiple pilot symbols located at the same frequency and spaced in the time domain by a time spacing P determined by the following expression: f D T s P< 1/2 .