  This paper investigates the optimization of beamforming design in a system
with integrated sensing and communication (ISAC), where the base station (BS)
sends signals for simultaneous multiuser communication and radar sensing. We
aim at maximizing the energy efficiency (EE) of the multiuser communication
while guaranteeing the sensing requirement in terms of individual radar
beampattern gains. The problem is a complicated nonconvex fractional program
which is challenging to be solved. By appropriately reformulating the problem
and then applying the techniques of successive convex approximation (SCA) and
semidefinite relaxation (SDR), we propose an iterative algorithm to address
this problem. In theory, we prove that the introduced relaxation of the SDR is
rigorously tight. Numerical results validate the effectiveness of the proposed
algorithm.
