The opportunities and challenges of 5G rapidly gain great attention from academics, industries, and governments. International standard organizations such as 3GPP and ITU, have initiated working groups for establishing standards of a faster and more efficient next generation (called the 5G) wireless network. One of the advances of the 5G beyond the previous standards is its ambitious performance requirements, such as high peak transmission rate, high spectrum utilization, and high energy efficiency. A promising solution answers part of performance requirement of the 5G, especially for stationary or low velocity users, is an ultra dense small cell wireless network with massive multiple input multiple output (MIMO) antennas and MU-MIMO technique for improving spectrum utilization. Moreover, the 5G network should allow heterogeneous wireless device communication, perform the cooperative mechanism for enhancing the transmission diversity, use cognitive radio technology for spectrum reuse, and consider energy efficiency. This paper lists several resource management issues in ultra-dense 5G smallcell networks.