  We investigate the use of an intelligent reflecting surface (IRS) in a
millimeter-wave (mmWave) vehicular communication network. An intelligent
reflecting surface consists of passive elements, which can reflect the incoming
signals with adjustable phase shifts. By properly tuning the phase shifts we
can improve link performance. This is known as phase optimization or passive
beamforming. We consider the problem of rate maximization in the uplink, which
utilizes an IRS. However, using an IRS brings more challenges in terms of
channel estimation. We propose two schemes to reduce the channel estimation
overhead associated with utilizing an IRS. One method uses the grouping of
reflecting elements and the other one performs passive beamforming based on the
position of the device. Numerical results show IRS can bring significant
improvements to existing communication. Furthermore, to get a practical insight
into vehicular communications aided by an IRS, we use a commercial ray-tracing
tool to evaluate the performance.
