  User scheduling and beamforming design are two crucial yet coupled topics for
wireless communication systems. They are usually optimized separately with
conventional optimization methods. In this paper, a novel cross-layer
optimization problem is considered, namely, the user scheduling and beamforming
are jointly discussed subjecting to the requirement of per-user quality of
service (QoS) and the maximum allowable transmit power for multicell multiuser
joint transmission networks. To achieve the goal, a mixed discrete-continue
variables combinational optimization problem is investigated with aiming at
maximizing the sum rate of the communication system. To circumvent the original
non-convex problem with dynamic solution space, we first transform it into a
0-1 integer and continue variables optimization problem, and then obtain a
tractable form with continuous variables by exploiting the characteristics of
0-1 constraint. Finally, the scheduled users and the optimized beamforming
vectors are simultaneously calculated by an alternating optimization algorithm.
We also theoretically prove that the base stations allocate zero power to the
unscheduled users. Furthermore, two heuristic optimization algorithms are
proposed respectively based on brute-force search and greedy search. Numerical
results validate the effectiveness of our proposed methods, and the
optimization approach gets relatively balanced results compared with the other
two approaches.
