  This paper investigates two performance metrics, namely ergodic capacity and
symbol error rate, of mmWave communication system assisted by a reconfigurable
intelligent surface (RIS). We assume independent and identically distributed
(i.i.d.) Rician fadings between user-RIS-Access Point (AP), with RIS surface
consisting of passive reflecting elements. First, we derive a new unified
closed-form formula for the average symbol error probability of generalised
M-QAM/M-PSK signalling over this mmWave link. We then obtain new closed-form
expressions for the ergodic capacity with and without channel state information
(CSI) at the AP.
