The paper investigates robust wireless communication in high-scattering environments using multi-element antenna arrays (MEA's) at both transmit and receive sites. A simplified, spectrally efficient space-time communication processing method is presented, where the user's bit stream is mapped to a vector of independently modulated equal bit-rate signal components transmitted simultaneously in the same band. A detection algorithm similar to multiuser detection is employed to detect these components in white Gaussian noise (WGN). For a large number of antennas, a more efficient architecture offers only about 40% more capacity compared to the simple architecture. A testbed operating at 1.9 GHz with up to 16 quadrature amplitude modulation (QAM) transmitters and 16 receive antennas is described. Under ideal conditions with 18 dB signal-to-noise ratio (SNR), using 12 transmit antennas and 16 receive antennas, the theoretical spectral efficiency is 36 bits/Hz, while the Shannon capacity is 71.1 bits/Hz. The paper also discusses the vertical BLAST (V-BLAST) algorithm, which is simpler than the diagonally layered architecture, and shows that it can achieve a significant fraction of the bit rates of the diagonal approach. The authors conclude that the flexible, simple vertical architecture eases implementation and significantly increases communication efficiency, with the vertical Shannon capacity growing linearly with the number of antennas.The paper investigates robust wireless communication in high-scattering environments using multi-element antenna arrays (MEA's) at both transmit and receive sites. A simplified, spectrally efficient space-time communication processing method is presented, where the user's bit stream is mapped to a vector of independently modulated equal bit-rate signal components transmitted simultaneously in the same band. A detection algorithm similar to multiuser detection is employed to detect these components in white Gaussian noise (WGN). For a large number of antennas, a more efficient architecture offers only about 40% more capacity compared to the simple architecture. A testbed operating at 1.9 GHz with up to 16 quadrature amplitude modulation (QAM) transmitters and 16 receive antennas is described. Under ideal conditions with 18 dB signal-to-noise ratio (SNR), using 12 transmit antennas and 16 receive antennas, the theoretical spectral efficiency is 36 bits/Hz, while the Shannon capacity is 71.1 bits/Hz. The paper also discusses the vertical BLAST (V-BLAST) algorithm, which is simpler than the diagonally layered architecture, and shows that it can achieve a significant fraction of the bit rates of the diagonal approach. The authors conclude that the flexible, simple vertical architecture eases implementation and significantly increases communication efficiency, with the vertical Shannon capacity growing linearly with the number of antennas.