  Lifetime of motes in wireless sensor networks can be enlarged by decreasing
the energy spent for communication. Approaches like time slotted channel
hopping pursue this goal by performing frame exchanges according to a
predefined schedule, which helps reducing the duty cycle. Unfortunately,
whenever the receiving radio interface is active but nobody in the network is
transmitting, idle listening occurs. If the traffic pattern is known in
advance, as in the relevant case of periodic sensing, proactive reduction of
idle listening (PRIL) noticeably lowers energy waste by disabling receivers
when no frames are expected for them. Optimal PRIL operation demands that, at
any time, the transmitter and receiver sides of a link have a coherent view of
its state (either enabled or disabled). However, this is not ensured in the
presence of acknowledgment frame losses. This paper presents and analyzes some
strategies to cope with such events. An extensive experimental campaign has
been carried out through discrete event simulation to determine what
consequences above errors may have from both a functional and performance
viewpoint. Results show that, although no strategy is optimal in all
circumstances, different solutions can be profitably adopted depending on the
specific operating conditions.
