Achievable sum rate analysis of relay aided overlay device to device communication among multiple devices

In this paper, we consider device to device (D2D) communication
overlaying cellular network where a group of D2D
users exchange messages among themselves. We investigate the
case when the channel conditions of the direct links among these
D2D users are not strong enough to support direct communication
and hence, an intermediate relay node assists the communication
among the D2D users. Here we consider capacity achieving lattice
codes at the D2D users along with compute-and-forward protocol
at the relay. Based on these, we derive the received SNR at the relay,
as well as the D2D users and formulate upper bounds on the achievable
sumrate. We also investigate the achievable sumrate when the
devices communicate using the direct links and compare with that
of the relay aided D2D communication. We find that when the D2D
users are closer to the relay, relay aided communication achieves
better performance compared to direct communication. However,
for the same distances, the sum rate degrades more for relay aided
communication. It is also shown that when the links between most
of the D2D users and the relay have good channel conditions compared
to the direct links, relay aided communication can achieve
better sum rate performance than the direct communication.