For high-speed users, overcoming the effect of frequently handover in small cells is the second challenge. To solve this challenge, the concept of a cooperative small cell group is presented to support high -speed user handover among small cells. In this case, multiple small cells must cooperatively transmit traffic to a high-speed user. When the high-speed user departs a small cell, other cooperative small cells still cover its track and consecutively transmit the high traffic to the high-speed user. Moreover, the new small cell is added into the cooperative small cell group based on the high-speed user track. However, there are many issues that need to be solved to realize this idea, such as how to organize a dynamic cooperative cell group and how to decrease the overhead of sharing data in the cooperative small cell group.