Focusing on LTE physical layer (PHY) and its channels, we investigate the resilience of an LTE network against jamming attacks. We conduct tests on an operational LTE network. Although LTE PHY jamming attacks have been studied, studies have not investigated the jamming attacks on a commercial LTE network. We examine the system performance of LTE PHY under two types of jamming attacks. Detailed measurement results are presented based on performance metrics of LTE networks. Finally, several counter measures against such jamming attacks are suggested.