1. An Energy Efficient Hierarchical Heterogeneous Wireless Sensor Network
16/04/2017
An Energy Efficient Hierarchical Heterogeneous Wireless Sensor Network
Isameldin M. Suliman
Centre for Wireless Communications
P.O. Box 4500, University of Oulu,
Finland

2. Overview Introduction Energy Efficiency in Wireless Sensor Networks
The Proposed Model
Advantages and Features
Problem formulation
Zoned Wireless Sensor Network
Conclusions
Directions for future work

3. Introduction
Future communication networks are expected to be heterogeneous consisting of different wireless technologies
These wireless technologies can be used in building wireless sensor networks
The development of these network technologies and due to the limited energy supply of sensors have prompted sensor researchers to consider alternatives that minimize energy consumption in sensor networks
The objective of this paper is propose a heterogeneous wireless sensor network and to develop a game theoretic approach for energy efficiency in the wireless sensor network

4. Energy Efficiency in Wireless Sensor Network
Energy efficiency is an important issue for wireless sensor networks since nodes in the network must rely on their batteries
The power constraints must be met in order to allow sensor networks to operate without disruption for extended periods of time
Designing energy efficiency algorithms in wireless sensor network is very challenging due to:
Multihopping
Sensor nodes are highly resource-constrained in terms of communication bandwidth and battery power

5. The Proposed Model (1)
The proposed model consider a wireless sensor network divided into number of clusters
Each cluster consists of a cluster master/
relaying node and sensor nodes that are randomly spread throughout the cluster
The network uses two type of nodes; type 1 nodes equipped with single wireless interface (Bluetooth); and type two nodes equipped with multiple network interfaces (Bluetooth and WLAN)
The energy-efficient model tries to enable the rotation of activity (relaying sensor data to a sink) among sensor nodes and to avoid the use of nodes with little remaining lifetime

6. The Proposed Model (2)
The energy efficient model aims to distribute the relaying activity among sensor nodes to achieve certain level of network equilibrium and to ensure that all relaying nodes run out of power at about the same time
Relaying nodes haves two responsibilities: relaying data for their own clusters as well as cooperating with each other to relay the wireless sensor network data
The hierarchical nature of the network eliminates the need for a dedicated route/routing table information from cluster nodes to the sink
A relaying node collects its own cluster data, aggregates, and periodically transmit the data to the sink
When the relaying node battery level falls below a threshold, the relaying node can withdraw from the list of relaying nodes and announce that move to other relaying nodes. It can then rejects data forwarding requests
However, traffic connection is not blocked, as other relaying node can be used

7. Advantages and Features
Nodes in the cluster don't need to do any routing processing since they use the cluster relaying node for sending their data to
Nodes in each cluster are isolated from frequent topology changes due to relaying nodes failure
The cluster relaying node can aggregate data received from the cluster sensors/slaves and remove all duplicate information
To further minimize energy consumptions, cluster nodes don't need to include source and destination information in data packet headers

8. Problem formulation (1)
Consider a wireless sensor network model that
has n relaying nodes indexed by i = 1,...,n
Each relaying node ni has a battery power pi,
consumes an amount ci >= 0 for its cluster
operation, and spent an amount ri >= 0 for
relaying network data
Therefore the relaying node power
supply pi = ci + ri
The figure illustrates the equilibrium of power consumption (division of power between cluster operation and relaying network data)
Vector c = (c1, c2,...,cn) is the vector of clusters’ power consumption for all relaying nodes and vector r = (r1, r2,...,rn) is the vector of relaying power for all relaying nodes.
The total relaying power provided by the relaying nodes is the sum

9. Problem Formulation (2)
We assume that relaying nodes are rational, i.e. their power allocation is strictly determined by their self interest
Each relaying node ni has utility function of the form ,
where is the relaying power contributed by other relaying nodes
Relaying nodes try to maximize their utilities ,
such that ci + ri = pi and ci, ri >= 0
We can see that each relaying node is choosing not only his relaying power contribution, but also the equilibrium level of the relaying power R allocated by all relaying nodes
Depending on its power constraints, a relaying node can decide to make zero contribution i.e. ri = 0, in which case he can choose R = R _1

10. Zoned Wireless Sensor Network
The sensor network has been divided into four zones/levels
The zones are concentric circles around the sink
The inner zone is the area immediately surrounding the sink. Relays in this zone are the most used ones
The outer zones will naturally have a smaller power consumption (as they don’t do any data relaying apart from their own cluster data)

11. A game theoretic approach to model energy constraints is explained
Conclusions
An Energy Efficient Hierarchical Heterogeneous Wireless Sensor Network has been proposed
A game theoretic approach to model energy constraints is explained
The model defines two type of nodes ; type 1 nodes equipped with single wireless interface (Bluetooth); and type two nodes equipped with multiple network interfaces (Bluetooth and WLAN)
The wireless sensor network has been divided into multiple zones to provide the ability to fairly distribute the power expenditure among relaying nodes

12. Directions for future work
Enhancing the problem statement/formulation and finding a solution to the problem
Provide some numerical examples
Compare the results with some previous results