Efficient OFDM communications with interference immunity

Abstract

The present invention relates to employing OFDM modulation in combination with spatial diversity and space-time block coding to provide high data rates and exceptional interference immunity. For transmission, quadrature modulated data is encoded in space and time to create individual series of encoded symbols. Each of these series of encoded symbols is subjected to a type of inverse Fourier Transform in corresponding transmission paths. In each transmission path, cyclic extensions may be appended to the resultant symbols, which are subsequently converted to an analog format, modulated, amplified, and transmitted from one of multiple antennas. Preferably, such communications are implemented from base stations to mobile terminals in an environment where the frequency reuse factor is approximately one and the base stations are synchronized to a common clock signal.

1 . A wireless communication system supporting orthogonal frequency division multiplexing (OFDM) having a base station comprising: 
 a) a quadrature modulator adapted to generate symbols from data to be transmitted;    b) a symbol encoder adapted to encode the symbols based on space and time wherein constellation position and timing of the symbols are affected to provide a plurality of series of encoded symbols;    c) transform circuitry adapted to provide a type of inverse Fourier Transform (IFT) on each of the plurality of series of encoded symbols to provide a series of IFT symbols; and    d) a plurality of transmission paths, each of which being coupled to one of a plurality of antennas and adapted to modulate one of the series of IFT symbols for transmission from one of the plurality of antennas to provide spatial diversity.