Interference alignment in cellular system with multiple D2D networks

In this paper, we have modeled underlaying multiple D2D networks into interference channel and used interference alignment (IA) in two different ways. In the first IA design, all the cell and D2D users (CUs & eNB and DUs & DRs) are considered in mitigating the interference, while in the second design, the group of CUs and eNB is omitted in IA design to reduce the overhead of channel state information (CSI). To show the distance or location dependence, the cross channel variance (τ) between DUs-eNB group and the CUs-DR groups has been varied. The rate loss upper bound between the two IA schemes is calculated that shows, the rate difference increases with increase in SNR and is proportional to cross channel variance. The simulation results show that for small values of τ, the second IA scheme gives almost similar sum rates. For large values of τ, the DU sum rates are low and show a constant rate loss. Thus, second IA technique can be utilized to reduce overhead in D2D communication.