In this paper, we propose a novel QoE optimization mechanism for Dynamic Adaptive Streaming over HTTP (DASH) in the context of wireless mobile networks. The proposed mechanism leverages recent advances in 3GPP DASH specification, which includes new features for QoE measurements and reporting. The proposed optimization mechanism has two objective functions, the first function maximizes the overall average QoE among DASH clients while the second function minimizes the negative impact of temporal video quality changes, i.e. the up and down switching between different representation during playback. The results of our simulations demonstrate that the proposed method improves the overall QoE and outperform other approaches where DASH clients only rely on local adaptation logic.