  Intelligent reflecting surface (IRS) is envisioned as a promising solution
for controlling radio propagation environments in future wireless systems. In
this paper, we propose a distributed intelligent reflecting surface (IRS)
assisted multi-user millimeter wave (mmWave) system, where IRSs are exploited
to enhance the mmWave signal coverage when direct links between base station
and users are unavailable. First, a joint active and passive beamforming
problem is established for weighted sum-rate maximization. Then, an alternating
iterative algorithm with closed-form expressions is proposed to tackle the
challenging non-convex problem, thereby decoupling the active and passive
beamforming variables. Moreover, we design a constraint relaxation technique to
address the unit modulus constraints pertaining to the IRS. Numerical results
demonstrate that the distributed IRS can potentially enhance the communication
performance of existing wireless systems.
