Machines are becoming an important participant in communication networks, from industry to smart homes. Essentially, Machine-to-Machine communication (M2M), also called Machine Type Communications (MTC), refers to automated applications executing on smart devices or machines that communicate through a wired and/or wireless network with very little human intervention or none at all. This book deals with the use of IEEE 802.15.4 / ZigBee communications technology to service M2M traffic. In order to improve the performance of the network for M2M nodes, we propose improvements to the protocol which consist of small adjustments to the parameters of the protocol and should, therefore, be simple to implement in practice. Moreover, no changes would be required to allow existing IEEE 802.15.4 / ZigBee nodes to be used in improved networks.