wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

4-12 Industrial Communication Systems
4.5.6 Sensor Protocols for Information via Negotiation
Sensor protocols for information via negotiation [HKB99] are a family of protocols used to efficiently
distribute information in a WSN. Conventional data dissemination approaches such as flooding and
gossiping waste valuable communication and energy resources by sending redundant information
throughout the network. SPIN use data negotiation and resource-adaptive algorithms. Nodes running
SPIN assign a high-level name to their data, called meta-data, and perform meta-data negotiations
before any data is transmitted; therefore, there is no redundant data sent through the network. SPIN has
access to the current energy level of the node and adapts the protocol it is running based on the remaining
energy. The SPIN family protocols use three types of messages: when a SPIN node has some new
data, it sends an advanced (ADV) message containing metadata to its neighbors. When a SPIN node
wishes to receive the data, it sends an REQ message, and then there are DATA messages that are messages
with a metadata header.
The SPIN family of protocols is made up of different protocols, SPIN-1, and SPIN-2; they incorporate
negotiation before transmitting data in order to ensure that only useful information will be transferred,
SPIN-BC (for broadcast channels), SPIN-PP (designed for point-to-point communications), SPIN-EC
(with low energy threshold), and SPIN-RL.
4.5.7 Low Energy Adaptive Clustering Hierarchy
LEACH [HChB00] is a cluster-based protocol, which includes distributed cluster information. This protocol
randomly selects a few sensor nodes as cluster heads (CHs) and rotates this role to evenly distribute
the energy load among the sensors in the network. Figure 4.6 shows firstly a typical network based on
clusters, and secondly how a WSN is applied.
LEACH has two phases, the setup phase and the steady state phase. In the setup phase, the clusters
are organized and CHs are selected. In the steady state phase, the actual data transfer to the base station
(BS) takes place. The duration of the steady state phase is longer than the duration of the setup
phase in order to minimize overhead. All elected CHs broadcast an advertisement message to the rest
of the nodes in the network that they are the new CHs, and the rest of nodes decide to which they
want to belong to and inform the appropriate CHs. This decision is based on the signal strength of
the advertisement.
During the steady state phase, the sensor nodes can begin sensing and transmitting data to the CHs.
The CH node, after receiving all the data, aggregates it before sending it to the BS. Each cluster communicates
using different code division multiple access (CDMA) codes to reduce interference from nodes
belonging to other clusters.
C1
Cluster head
Regular node
Gateway
C1
Cluster head
Sensor node
Base station
C2
C2
C3
C3
FIGURE 4.6
Example of a typical network based on clusters and application in a sensor network.
© 2011 by Taylor and Francis Group, LLC