An IEEE 802.15.4-based Wireless Sensor Network

is considered, and the relationship between the IEEE 802.15.4 topology formation mechanism and possible routing strategies at the network layer is studied. Two alternative routing schemes proposed in the fr a mework of the ZigBee Alliance are analyzed.The first is the well-known Ad-hoc On demand Distance Vector

(AODV) routing protocol, which was designed for highly dynamic application scenarios in wireless ad-hoc networks. The second is

a tree-based routing scheme based on a hierarchical structure established among nodes during the network formation phase. This latter approach, referred to as HERA (HiErarchical Routing Algorithm) in the paper, routes packets from sensors to sink based on the parent-child relationships