  Intelligent reflecting surface (IRS) is envisioned to be a new and
revolutionizing technology for achieving spectrum and energy efficient wireless
communication networks cost-effectively in the future. Specifically, an IRS
consists of a large number of low-cost passive elements each reflecting the
incident signal with a certain phase shift to collaboratively achieve
beamforming and/or interference suppression at designated receivers. In this
paper, we study an IRS-aided multiuser multiple-input single-output (MISO)
wireless system where one IRS is deployed to assist in the communication from a
multi-antenna access point (AP) to multiple single-antenna users. As such, each
user receives the superposed signals from the AP as well as the IRS via its
reflection. We aim to minimize the total transmit power at the AP by jointly
optimizing the transmit beamforming by active antenna array at the AP and
reflect beamforming by passive phase shifters at the IRS, subject to users'
individual signal-to-interference-plus-noise ratio (SINR) constraints. However,
the formulated problem is non-convex and difficult to be solved optimally.
