Remark 6 The proposed beamforming design for the MIMO
FDR network can be extended to a more general case of
multiple users served by each relay. For this case, extra MUI
rom each relay need to be added in the received signal model
given by (5), followed by some modifications of the coefficient
matrix E in (15) that is used in the partial Lagrangian in (18),
and then the ensuing convergence analysis also needs to be
modified to finish the corresponding distributed beamforming
algorithm (counterpart of the proposed Algorithm 1) for this
case.