Motivated by the shared spectrum paradigm, we address the problem of implicit coordination between coexisting wireless systems that do not share a common control plane. We consider the coexistence of LTE and Wi-Fi and study mechanisms for conserving energy when the wireless channel is occupied. In a Wi-Fi only system, the network allocation vector (NAV) included in the header of IEEE 802.11 frames advertises the duration of an imminent transmission. Nearby Wi-Fi terminals decode the frame header and transition to sleep mode to conserve energy. However, when heterogeneous systems coexist (e.g., LTE and Wi-Fi), frames that belong to other systems are not decodable. This leads to continuous channel sensing even when the channel is to be occupied for a long duration. We design two implicit mechanisms to play the role of the NAV. Our mechanisms predict the duration of an imminent LTE transmission by predicting the frame's traffic class. The prediction is based on the elapsed idle slots between successive transmissions and the transmission history. We show that our methods achieve significant energy savings without stifling transmission opportunities.