The paper presents simulation study of communication system consisting of mobile nodes during crisis situation scenario. Nodes' network interfaces support IEEE 802.11ac standard in ad-hoc mode, while devices operate under control of Google Inc. Android operating system. Overview of current Wi-Fi techniques was described, with an indication of further standard evolution. Limitations of current Wi-Fi ad-hoc mode implementation in Android were addressed, with emphasis on ongoing research projects on overcoming specific restrictions: Wi-Fi Peer-to-Peer extension and multi-hop transmission. Evaluation of network efficiency with Voice over IP service activity during an emergency scenario was performed in simulation environment. Lack of cellular connectivity, external power access and no access to special communication equipment during rescue operation were assumed. Obtained results show insignificant impact of service realization on network resources utilization, low maximum end-to-end packet delivery delay and jitter values during continuous telephone conversations. Thus, described assessment shows a high degree of IEEE 802.11ac ad-hoc network applicability in scope of basic voice communication service realization in case of absence of usually ubiquitous cellular infrastructure, with use of typical communication equipment.