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Introduction

The advent of Machine-to-Machine (M2M) communication opened a whole world of possibilities in the Home Automation scenario. Earlier to the adaption of M2M, routine tasks like sensing the room temperature, monitoring the water level in the tank, monitoring the moisture content in the soil were performed independently with the use of sensors nodes and actuators. Now, with the possibility of a sensor node communicating with other sensor node, all of these routine tasks can be performed in a coordinating manner where the result of one can benefit the operation of the other. This coordination is made possible by equipping each of the sensor nodes with wireless transmission and reception capabilities so that the information is forwarded to the intended destination. Now, with information forwarding in the picture, sensor nodes, in addition to monitoring, also have to take care in forwarding information such that it reaches the intended destination. This additional task comes at a cost of additional energy consumption.

Since the sensor nodes are usually considered to be energy constrained, any task that increases the energy consumption is something to be taken care of. To address this issue of rise in energy consumption due to packet forwarding, we propose a routing protocol that selects relatively energy rich sensor nodes for packet forwarding over energy scarce sensor nodes. Energy rich and energy scarce sensor nodes are classified based on their power supply.

Following are the categorization of sensor nodes depending on power supply.

1. The nodes whose power supply come from the mains are called Fixed nodes and given highest priority for forwarding packets. As the power supply for these nodes can be considered to be continuous, there is abundant energy and hence can take active part in routing packets to the destination. In a Home Automation scenario, consider the nodes like smart lights which can sense the ambient light in the atmosphere and get turned ON when dark. Nodes like these are usually connected to the main supply and hence considered to be energy abundant.

2. The nodes with rechargeable power supply are called User nodes and are given medium priority in packet forwarding. With these nodes, even if the power supply is not as abundant as the mains, we can ensure longevity through recharging. In a Home Automation scenario, we consider the smart wearables worn by people in the house to be User nodes. These have rechargeable batteries and are always in motion inside the house. Including these in packet forwarding might help in a better reachability throughout the house. These are termed as User nodes because of the fact that it is worn by the users of Home Automation deployment.

3. The nodes which draw power from a battery are called Battery nodes and are given least priority in packet forwarding. In a Home Automation scenario these can be moisture sensors attached to plants, temperature sensors deployed in the store house or a water level indicator placed inside a water tank. These nodes operate just with the battery power. Involvement of Battery nodes in forwarding packet drains the battery soon and reduces longevity of the sensor nodes. Thus, they are given least priority while involving in packet forwarding.

The remainder of the report describes the Wireless Sensor Network design and explains the ‘Power Supply Prioritized Routing Protocol’ developed using the classification of nodes described above.

Application

Home Automation is one of the widespread use cases of the ‘Internet of Things’. Sensor nodes are distributed throughout the house for monitoring and control purposes. Keeping in mind the energy constraints of sensor nodes and the diversity of their power supply, this project aims at the implementation of a Power Supply Prioritized Routing Protocol for a Home Automation scenario. We consider a scenario where a number of sensor nodes are distributed throughout the house with each sensor node sensing or controlling a specific parameter. The monitoring and status information from all the nodes is intended to reach the Coordinator node at regular intervals. Coordinator node is where all the data is collected and displayed. The proposed routing protocol ensures that the path taken to reach the coordinator is selected such that the nodes with higher priority power supplies (like mains, rechargeable batteries) are utilized more so that the sensing nodes merely running on battery can conserve energy by not involving in packet forwarding.

As mentioned in the Introduction section, nodes are categorized into three categories namely Fixed nodes, User nodes and Battery nodes, based on their power supply. Coordinator node is the central node that collects data from all the nodes. Coordinator node is the destination for status and monitoring information generated from all the nodes.

Coordinator sends out broadcasts at regular intervals. Keeping this broadcast as reference, all other nodes populate their routing table with a power supply prioritized route to reach the Coordinator. If the Coordinator couldn’t be reached by a node directly, the Fixed node is used for packet forwarding to reach the Coordinator. If any of the Fixed node isn’t reachable then the node goes for a User node to forward its packet. Finally, a failure to reach both Fixed and User node will cause a special routing request to which battery nodes will respond and forward the packet. This way, Battery nodes are prioritized the least for packet forwarding hence conserving battery power and ensuring the longevity of operation.