  In this paper, we investigate a unified linear transceiver design with
mean-square-error (MSE) as the objective function for a wide range of wireless
systems. The unified design is based on an elegant mathematical programming
technology namely quadratic matrix programming (QMP). It is revealed that for
different wireless systems such as multi-cell coordination systems, multi-user
MIMO systems, MIMO cognitive radio systems, amplify-and-forward MIMO relaying
systems, the MSE minimization beamforming design problems can always be solved
by solving a number of QMP problems. A comprehensive framework on how to solve
QMP problems is also given.
