Authors: Joaquim Azevedo, Filipe Santos, Maurcio Rodrigues, and
Lus Aguiar Form : IET Wireless Sensor Systems Speaker: Hao-Wei Lu
sleeping zigbee networks at the application layer
Abstract 3 ZigBee/IEEE 802.15.4 is one of the most used
standards for low-power applications. However, full function
devices (FFD) must be always active to route data in a mesh
network. The objective of this work is to implement a sleeping
technique at the application layer that enables sleep mode for all
nodes of a ZigBee network
Slide 4
Abstract (Cont.) 4 A large network is organised into smaller
groups to reduce latency and packet collisions. The active interval
of each node is dynamically adapted to the network operation to
optimise the energy consumption. The results demonstrated energy
savings of about 95% for networks containing up to 20 nodes per
group and wake up periods longer than 2 min.
Slide 5
Introduction 5 Wireless sensor networks (WSNs) are being used
in several different areas, such as environmental monitoring,
industrial systems, buildings and infrastructure monitoring,
precision agriculture and so on. Enabling sensor nodes to enter
sleep mode has been considered one of the most effective solutions
to reduce energy consumption and extend the lifetime of a WSN.
Slide 6
Introduction (Cont.) 6 Several sleep/wakeup schemes have been
proposed to enhance the performance of the sensor nodes.
Sensor-medium access control (S-MAC) is a well- known protocol used
to improve energy efficiency by ordering all network devices to
sleep in a periodic manner. timeout-MAC (T-MAC) is similar to S-MAC
but saves more energy by introducing an adaptive duty cycle.
Slide 7
Introduction (Cont.) 7 The proposed technique not only provides
data collection but also allows data transfer between different
nodes. Furthermore, it is provided the sleep mode to all nodes of a
ZigBee mesh network and protection against message losses.
Slide 8
Synchronisation 8 The ZigBee protocol does not provide
synchronisation in mesh topologies. Therefore the development of an
appropriate sleeping technique at the application layer also
requires a synchronisation routine implemented in this layer.
Slide 9
Synchronisation (Cont.) 9 The collision avoidance method used
in the ZigBee is the carrier sense multiple access with collision
avoidance (CSMA/CA). These networks suffer from packet losses even
with the existence of this mechanism.
Slide 10
Synchronisation (Cont.) 10
Slide 11
Synchronisation (Cont.) 11
Slide 12
Synchronisation (Cont.) 12 The synchronisation mechanism
implemented at the application layer produces a rough approximation
of the notion of time at each node. However, this approximation may
alleviate the competition between nodes to obtain access to the
channel.
Slide 13
Synchronised sleeping technique 13 SST scheme The basic idea of
the proposed synchronised sleeping technique (SST) is to provide
the sleep mode to all nodes of a ZigBee network, which includes
FFDs. SST allows FFDs to sleep during network idle periods, which
provides energy savings.
Slide 14
14
Slide 15
Synchronised sleeping technique(Cont.) 15 Message recovery In a
ZigBee network message losses are common even with the existence of
the MAC CSMA/CA algorithm. However, robustness against message
losses may be required for some nodes. The technique also considers
this issue by recovering lost messages
Conclusion 26 A technique is proposed to enable all nodes in a
ZigBee network to enter sleep mode. Compared with other techniques,
the latency is lower and data transfer between nodes inside a group
is allowed. Comparing the energy consumption for a network with and
without the SST technique, energy savings for networks with at
least 10% of routers were achieved.
