  The synergy of metasurface-based holographic surfaces (HoloS) and
reconfigurable intelligent surfaces (RIS) is considered a key aspect for future
communication networks. However, the optimization of dynamic metasurfaces
requires the use of numerical algorithms, for example, based on the singular
value decomposition (SVD) and gradient descent methods, which are usually
computationally intensive, especially when the number of elements is large. In
this paper, we analyze low complexity designs for RIS-aided HoloS communication
systems, in which the configurations of the HoloS transmitter and the RIS are
given in a closed-form expression. We consider implementations based on
diagonal and non-diagonal RISs. Over line-of-sight channels, we show that the
proposed schemes provide performance that is close to that offered by complex
numerical methods.
