ABSTRACT
A modern approach for wireless fading channels is to use multiple antennas both at the Tx and Rx in combination with sophisticated space–time signal processing techniques, as space–division multiple access (SDMA) and multiple-input multiple-output (MIMO). The well-known SDMA and MIMO algorithms for frequency-flat fading channels can therefore be used also in frequency-selective channels, by applying them individually on each orthogonal frequency division multiplexing (OFDM) subcarrier. Most MIMO-OFDM prototypes in the recent literature transmit the signals over the air and perform the processing off-line. There is an ever-increasing demand for higher bandwidths in mobile communication systems. While the target of the first generations was mobile telephony, deployed systems aim to enhance people’s lives by enabling high-speed mobile access to the Internet anywhere and at any time. In a mobile communications environment, the base station often has sector antennas and knows the direction of the terminal equipped with omnidirectional antennas only coarsely.
