This study proposes a simple cross layer design between physical and medium access layers for power conservation based on transmission power control. The carrier sense multiple access with collision avoidance (CSMA/CA) mechanism of IEEE 802.11 wireless local area network (WLAN) standard is integrated with the power control algorithm. In this method, the exchange of RTS/CTS.control signals is used to piggyback the necessary information to enable the transmitting nodes to discover the required minimum amount of power that is needed to transmit data packets. This simulation is implemented using Global Mobile Information Systems Simulator (GloMoSim) and its performance studied using on-demand routing protocols such as Dynamic source routing (DSR). Around 7% power conservation is obtained with DSR routing protocol.