Sharing Transmission Opportunity period (TXOP) technique is recently defined by IEEE 802.11ac to allow simultaneous downlink transmissions. In this paper, we focus on the basis of this technique and the behavior of the access point (AP) to manage the multi-user access. We discuss the different steps required to allow simultaneous downlink transmissions. Based on simulation results, we prove that TXOP sharing technique has a significant positive impact on delay performance of different access categories (ACs).