  Reconfigurable intelligent surfaces (RISs) is a promising solution for
enhancing the performance of multihop wireless communication networks. In this
paper, we propose a double-RIS assisted multihop routing scheme for a
device-to-device (D2D) communication network. Specifically, the scheme is
dependent on the already deployed RISs and users in the surroundings. Besides
the RISs, the emphasis of this work is to make more use of the existing
intermediate users (IUs), which can act as relays. Hence, the density of RIS
deployment in the surroundings can be reduced, which leads to the avoidance of
resource wastage. However, we cannot solely depend on the IUs because this
implies complete dependence on their availability for relaying and as a result,
the aspect of reliability in terms of delay-constrained information transfer
cannot be guaranteed. Moreover, the IUs are considered capable of energy
harvesting and as a result, they do not waste their own energy in the process
of volunteering to act as a relay for other users. Numerical results
demonstrate the advantage of the proposed scheme over some existing approaches
and lastly, useful insights related to the scheme design are also drawn, where
we characterize the maximum acceptable delay at each hop under different
set-ups.
