Transmit diversity versus SDMA: analytic and numerical comparisons

The capacity of a wireless link with multiple transmit antennas is compared to the average per user capacity of a multiuser wireless network with space division multiple access (SDMA). Under the assumption of a rich scattering environment and a narrow-band link, the propagation medium is modeled as a Rayleigh flat fading with a good receive diversity. By contrast to the previous works, the assumption of full decorrelation of the transmit antennas is relaxed. This enables a study of the transmit diversity scenarios where the transmit antennas occupy a limited space. The new analytic results give rise to a comparison of the capacity achievable with multiple transmit antennas within a limited transmit volume on one hand, and the capacity of an SDMA network with spatially spread users, on the other hand. The capacity simulations corresponding to an indoor wireless LAN are presented along with the theoretical results