Optimal transmit covariance matrices for MIMO high speed uplink packet access

He increasing importance of uplink scheduling in future wireless systems is mirrored in the work on the high speed uplink packet access (HSUPA) radio link design. The nature of optimization problems associated with uplink schedulinghe increasing importance of uplink scheduling in future wireless systems is mirrored in the work on the high speed uplink packet access (HSUPA) radio link design. The nature of optimization problems associated with uplink schedulingT pointed up the importance of knowledge of the geometry of the capacity and stability region. This knowledge can significantly facilitate the design of delayless scheduling routines. We provide the geometrical analysis of the capacity and stability region in the multi-antenna uplink. We give an insight in the general structure and state general properties of the capacity and stability region. Concentrating on the MIMO-MAC with indvidual power constraints, we identity and interpret specific-points and regions at the boundary and characterise transmit strategies achieving them. We state a general necessary and sufficient condition for emerging of rate-sum optimal corner points in the capacity and the stability region. Finally, we analyse the behaviour of the capacity and stability region in terms of power constraint variation.