  Intelligent reflecting surface (IRS) has recently emerged as a promising
technology for beyond fifth-generation (B5G) and 6G networks conceived from
metamaterials that smartly tunes the signal reflections via a large number of
low-cost passive reflecting elements. However, the IRS-assisted communication
model and the optimization of available resources needs to be improved further
for more efficient communications. This paper investigates the enhancement of
received power at the user end in an IRS assisted wireless communication by
jointly optimizing the phase shifts at the IRS elements and its location.
Employing the conventional Friss transmission model, the relationship between
the transmitted power and reflected power is established. The expression of
received power incorporates the free space loss, reflection loss factor,
physical dimension of the IRS panel, and radiation pattern of the transmit
signal. Also, the expression of reflection coefficient of IRS panel is obtained
by exploiting the existing data of radar communications. Initially exploring a
single IRS element within a two-ray reflection model, we extend it to a more
complex multi-ray reflection model with multiple IRS elements in 3D Cartesian
space. The received power expression is derived in a more tractable form, then,
it is maximized by jointly optimizing the underlying underlying variables, the
IRS location and the phase shifts. To realize the joint optimization of
underlying variables, first, the phase shifts of the IRS elements are optimized
to achieve constructive interference of received signal components at the user.
Subsequently, the location of the IRS is optimized at the obtained optimal
phase shifts. Numerical insights and performance comparison reveal that joint
optimization leads to a substantial 37% enhancement in received power compared
to the closest competitive benchmark scheme.
