1. A method for determining a transmission schedule for one or more transmissions from a first child node to a first parent node in a multi-hop wireless network, wherein each node is a child node to a corresponding parent node, each child node being configured to send one or more messages directed to a sink node via its corresponding parent node and wherein the method comprises the first parent node:listening for signals indicating scheduled timeslots for transmission between nodes in the network and, if a signal is detected, updating a record of scheduled transmissions;
receiving from the first child node a preliminary schedule specifying a timeslot for transmission of each of the one or more messages to the first parent node;
determining, based on the record of scheduled transmissions, whether the preliminary schedule includes any scheduled transmissions that would conflict with any scheduled transmissions in the record of scheduled transmissions or whether the length of the preliminary schedule can be reduced without conflicting with any other scheduled transmissions in the record of scheduled transmissions;
responsive to a determination that there would be a conflict or that the length of the preliminary schedule can be reduced without conflict:
determining an updated schedule for the first child node by determining a set of scheduled timeslots that minimizes the number of scheduled timeslots without conflicting with any of the scheduled transmissions in the record of scheduled transmissions; and
sending the updated schedule to the first child node to assign the updated schedule to the first child node.