Patent ID: 8873651

Claim:
An Orthogonal Frequency-Division Multiplexing (OFDM) generation apparatus for generating Absolute OFDM transmission signals from OFDM symbols, each comprising a plurality of OFDM subcarriers, for transmission in a multi-carrier data transmission system, said apparatus comprising: circuitry configured to: determine receiver mixing frequencies for use by an OFDM decoding apparatus of a receiving apparatus for mixing a received OFDM transmission signal from a passband frequency down to a baseband frequency by use of a receiver mixing frequency f DS,c to obtain complex time-domain samples of a data symbol in a receiver, wherein the receiver mixing frequencies are selected such that common phase rotations of the OFDM subcarriers of the data symbol with respect to adjacent data symbols of the same data segment are avoided or compensated after mixing the received OFDM transmission signal from the passband frequency down to the baseband frequency by use of the selected receiver mixing frequencies; inverse Discrete Fourier Transform (DFT) OFDM symbols into complex time-domain samples; and perform frequency mixing of said complex time-domain samples of said OFDM symbols from a baseband frequency up to a passband frequency by use of a mixing frequency f c to obtain said Absolute OFDM transmission signals, wherein the mixing frequency f c is selected such that common phase rotations of the OFDM subcarriers of said OFDM symbols with respect to adjacent OFDM symbols of said Absolute OFDM transmission signals are avoided or compensated after said mixing, and wherein the mixing frequency f c is selected as f c = k c T U with the OFDM subcarrier k c at the mixing frequency f c being selected as k c = ⌊ K m ⁢ ⁢ ax + K ⁢ m ⁢ ⁢ i ⁢ ⁢ n 2 · Δ T U + 1 2 ⌋ · 1 ( Δ T U ) , where T U is the useful OFDM symbol duration, Δ is the duration of the guard interval, K min is the carrier index of first active carrier having the lowest frequency, and K max is the carrier index of last active carrier having the highest frequency.