The multiple access channel interfering with a point to point link: Linear deterministic sum capacity

In this paper, we use the linear deterministic approximation model to study a two user multiple access channel (MAC) mutually interfering with a point to point link, which represents a basic model for the situation of device-to-device communication inside a cell. We derive upper bounds on the achievable sum rate and construct coding schemes achieving the upper bounds. For a large parameter range, the sum capacity is identical to the sum capacity of the interference channel obtained by silencing the weaker user in the MAC. For other interference configurations, the sum rate can be increased using interference alignment, which exploits the channel gain difference of the users in the MAC. From these results, lower bounds on the generalized degrees of freedom for the Gaussian counterpart are derived.