Device-to-device (D2D) communication provides an effective way to meet growing mobile traffic and capacity demand. D2D communication can improve existing cellular systems in several ways. When UEs are located in close proximity, they can communicate through direct links bypassing the base station (BS). In this way, the transmitter consumes less power while better Quality-of-Service can still be provided. D2D links can also increase both energy and spectrum efficiency by reusing downlink and uplink cellular resources. However, integrating D2D links into the cellular infrastructure complicates the interference situation because D2D communication might increase the co-channel interference and degrade cellular link quality. In this thesis, the interference mitigation techniques including resource allocation, power control and multiple antenna are proposed for D2D communications underlaying cellular systems to increase the data rate of both the cellular users and D2D pairs. The Zero-Forcing technique is carried out for interference mitigation by assuming perfect channel state information at the BS side. The effect of a limited feedback link for downlink cellular communication and channel estimation for uplink communication are considered for underlying multi antenna cellular system.