  Intelligent reflecting surface (IRS) has been widely considered as one of the
key enabling techniques for future wireless communication networks owing to its
ability of dynamically controlling the phase shift of reflected electromagnetic
(EM) waves to construct a favorable propagation environment. While IRS only
focuses on signal reflection, the recently emerged innovative concept of
intelligent omni-surface (IOS) can provide the dual functionality of
manipulating reflecting and transmitting signals. Thus, IOS is a new paradigm
for achieving ubiquitous wireless communications. In this paper, we consider an
IOSassisted multi-user multi-input single-output (MU-MISO) system where the IOS
utilizes its reflective and transmissive properties to enhance the MU-MISO
transmission. Both power minimization and sum-rate maximization problems are
solved by exploiting the second-order cone programming (SOCP), Riemannian
manifold, weighted minimum mean square error (WMMSE), and block coordinate
descent (BCD) methods. Simulation results verify the advancements of the IOS
for wireless systems and illustrate the significant performance improvement of
our proposed joint transmit beamforming, reflecting and transmitting
phase-shift, and IOS energy division design algorithms. Compared with
conventional IRS, IOS can significantly extend the communication coverage,
enhance the strength of received signals, and improve the quality of
communication links.
