Achievable DoF of an Underlay Two-User Gaussian Interference Channel in Heterogeneous Networks

This paper studies a new symmetric two-user Gaussian interferencechannel (IC) in heterogeneous networks where twotransmitter-receiver pairs are underlaid with one primarytransmitter-receiver pair. When underlay transmitters must restricttheir transmission to guarantee target degrees of freedom (DoF) of aprimary receiver, the achievable DoF of the underlay receivers inheterogeneous networks is investigated. Either transmit power ortransmission time is regulated to secure the target DoF of a primaryreceiver and their effects on the achievable DoF are analyzed for thesimple Han-Kobayashi scheme. Our analytical results show that theachievable DoF of the underlay two-user IC is substantiallydifferent from that of a conventional two-user IC due to the imposedrestriction on the underlay users. It is also shown that jointdecoding capability at the primary receiver using common codebookrelaxes the restriction imposed on the underlay users and henceimproves the achievable DoF of the underlay receivers.