any knowledge of when the receiver will be ready other than the period a sender must prefix multiple copies of a wake up message for a duration equal to or greater than the period of the receiver 39 s duty cycle preferably these wake up messages are numbered in descending order such that when the number of the wake up message reaches zero the data intended for the receiver will be transmitted upon reception of a message the receiver immediately replies to acknowledge reception of the data in a preferred implementation utilizing receiver state estimation the receiver also indicates the number of the first wake up message received the transmitter then calculates to some accuracy the time at which the receiver is in a ready state given that the ready state of the receiver occurs on a known periodic basis any future time at which the receiver will be ready can be calculated within the limits of the available time base if the time at which the receiver becomes ready can be estimated to within a time less than the period of the receiver duty cycle fewer wake up transmissions must be prefixed to future data transmissions this can save power by using fewer transmissions and can additionally reduce congestion such preferred methodologies reduce the power cost to the sender and bandwidth cost to the system when compared to a straightforward wake up radio system this method can be utilized separate from or in combination with aspects and features of wake up transceiver wu technology patented by terahop networks inc see u s pat no 7 209 771 incorporated above by reference and the patents related thereto or other known wake up technology and methodologies this method.