Capacity of MIMO-MAC with transmit channel knowledge in the low SNR regime

We study the sum capacity of the uplink multiuser multiple-input multiple-output (MIMO) multiple-access channel (MAC) in the low signal-to-noise ratio (SNR) regime under double-scattering and Rician fading scenarios. The receiver is assumed to have perfect channel state information (CSI), while each transmitter knows only its statistical CSI. We first derive analytical expressions for the minimum ¿
_b
/N
₀
and the wideband slope of MIMO systems employing statistical beamforming, based on which we then present new analytical approximations for the sum capacity of the MIMO-MAC at low SNRs, and investigate the effects of transmit, receive and scatterer correlation, as well as Rician K-factor.