Abstract: A method of operating an end node to communicate with a central node, the method comprising: wirelessly receiving, a beacon signal periodically-transmitted from the central node; each beacon signal denoting the start of a single frame; each frame being organized to include a downlink (DL) phase which precedes an uplink (UL) phase; and a payload of the beacon signal including an offset which represents a starting time of the UL phase. The method further comprises: generating a message; selecting, unbeknownst to the central node, at least one UL logical-channel, respectively; and wirelessly transmitting, during the UL phase, at least a portion of the message from the end node over the selected at least one UL logical-channel according to a slotted ALOHA technique.

Abstract: A method (of operating a central node to acknowledge received messages) includes: receiving multiple data messages from multiple instances of a message-sourceable end node, respectively, each end-node-instance having an at least substantially unique identification (“ID”); and sending a dense acknowledgement message (“dense ACK”) acknowledging receipt of the data messages but not explicitly identifying any of the IDs of the corresponding end-node-instances. And a method (of operating a given instance of the end node to infer a delivery-condition at the central node of a data message sent by the given instance) including: sending a given data message including the substantially unique ID; receiving a dense ACK including a payload indicating receipt of multiple data messages but not explicitly identifying IDs of the given end-node-instance nor of other end-node-instances corresponding to the received messages, respectively; and inferring the delivery-condition based on a manipulated payload of the dense ACK.