  The paper presents two mechanisms for designing an on-demand, reliable and
efficient collection protocol for Wireless Sensor Networks. The former is the
Bidirectional Link Quality Estimation, which allows nodes to easily and quickly
compute the quality of a link between a pair of nodes. The latter, Hierarchical
Range Sectoring, organizes sensors in different sectors based on their location
within the network. Based on this organization, nodes from each sector are
coordinated to transmit in specific periods of time to reduce the hidden
terminal problem. To evaluate these two mechanisms, a protocol called HBCP
(Hierarchical-Based Collection Protocol), that implements both mechanisms, has
been implemented in TinyOS 2.1, and evaluated in a testbed using TelosB motes.
The results show that the HBCP protocol is able to achieve a very high
reliability, especially in large networks and in scenarios with bottlenecks.
