The paradigm of the mobile ecosystem is rapidly changing, especially since the uction of smart devices. New important players are emerging, and the scope of the mobile ecosystem is expanding and encroaching on the technological boundaries of other IT ecosystems. However, our understanding of the mobile ecosystem has been limited given the few existing studies. Therefore, in this paper, we empirically examine the network structure of a mobile ecosystem by measuring the technology knowledge flows between firms based on a patent citation analysis of the mobile industry. We found that platform providers are emerging as the center of the knowledge flow activity in the ecosystem. By introducing a new network index, the Network Concentration Index, which measures a firm's knowledge concentration ratio toward subsectors, we also found that each platform provider shows distinctive changing patterns in their technology knowledge network and that each is forming its own sub-network with increased influence on affiliated firms.