The LTE Femtocells system can satisfy the users' requirements regarding the throughput in indoor zones and the outdoor ones. Thanks to the femtocells' deployment, the LTE Femtocells system can satisfy the fourth generation requirements beside to the good existent coverage. When the femtocells are deployed inside the LTE macrocells, a mutual electromagnetic interference, EMI, can exist between the macrocells and the femtocells. This interfernce eresults from the operation of the macrocells and the femtocells on the same spectrum. There should be an interference mitigation technique in order to improve the performance of the LTE femtocells system. The scope of this paper is the summarization of the different tools, which can be applied, in order to reduce or completely mitigate the interference between the macrocells and the femtocells. These tools are illustrated in details and simulated. Moreover, their performance is compared.