Presenting a routing method for wireless sensor networks with the aim of increasing the lifetime of the network

Dissertation for Master's Degree in Computer Science

Software Orientation

Abstract

The increasing use of wireless sensor networks in human life shows the great importance of this technology. Energy limitation in the constituent elements of wireless sensor networks, which are sensor nodes, has always been considered as the most important challenge facing this technology, and for this reason, most of the research conducted in the field of wireless sensor networks has been devoted to the issue of energy. Considering that the way of choosing routes to send information in wireless sensor networks has a significant effect on the energy consumption of the network, in this research, an attempt has been made to provide a solution in the field of routing with the aim of increasing the lifetime of the network. In this method, taking into account the energy consumption history of the sensor nodes, the number of neighbors of the sensor sending data, and the distance from the source to the destination of sending data (one step), a solution has been presented that can have a great effect on increasing the life of the circuit. Simulation and comparison with famous and successful methods of routing in wireless sensor networks show the merit of the proposed method.  

Key words: wireless sensor networks, routing, PSO algorithm, network lifetime, energy limitation

Chapter 1

Introduction

1 Introduction

Wireless sensor networks consist of a number of sensor nodes, and usually the size of these nodes is small and they are cheap. All these nodes have the ability to receive information from their surroundings, they can also send or receive data received from the environment to the sensor nodes located in their neighborhood. In this type of networks, the radius of data transmission is limited, and nodes are also limited in terms of information processing and storage. Due to the limited energy of the nodes, most of the routing methods in this type of networks have been proposed with the aim of increasing the lifetime of the network. In this research, a new routing algorithm is introduced, the most important goal of which is to increase the life of the network.

In most applications of wireless sensor networks, the way nodes are placed in the physical environment is random and does not have a specific and predetermined plan. After being placed in the environment, the nodes automatically form the network structure and for a limited period receive information from the surrounding environment and transfer it to the main station. The energy required to receive information from the environment and send information to other sensors is provided by the batteries embedded in the sensors. Therefore, the energy of these nodes is limited and in most applications, after the battery energy is exhausted, it is very difficult and usually impossible to recharge or replace it.

Different applications of sensor networks have led to the production of many sensor nodes that are very different in terms of architecture, size, energy consumption and node coverage radius. Table 1-1 shows some of these sensor nodes and their applications [1].

1-1 The necessity of the routing protocol problem and challenges

Energy limitation has always been the most important challenge facing wireless sensor networks. Considering that a large part of the network energy is spent on sending the information obtained from the environment to the main station, using a suitable routing method can greatly increase the lifetime of the network. Providing a routing protocol for wireless sensor networks faces challenges that arise from the limitations of these networks. Also, these networks are limited in many network resources. For example: communication bandwidth [1], processor unit, storage unit and energy [2,3]. The most important challenges facing the design of routing protocols are [4,5,6]:

1-1-1 Limited energy capacity

Considering that sensor nodes take the necessary energy from batteries, therefore they have a limited capacity. When the energy of the node is less than a threshold value, that node will not be able to continue its activity and this will have a great negative impact on the network. Therefore, the energy limitation is the biggest challenge for providing a routing protocol. 1-1-2 Node Location Coordinates Another challenge in providing a routing protocol is node location management. A large number of routing protocols assume that each sensor is equipped with a global positioning system [2] or use positioning algorithms to find the location of the node [5].

1-1-3 Limitation of hardware resources

In addition to energy, sensor nodes are also limited in terms of storage and processing. Sensor nodes cannot perform complex and long calculations, and this is a challenge for software development in wireless sensor networks. Therefore, to provide a routing algorithm, in addition to energy, hardware limitations should also be considered.

1-1-4 large number of nodes and random location in the environment

Wireless sensor networks are completely dependent on the network application. In most applications, a large number of nodes are randomly placed in the physical environment, which has a significant impact on the efficiency of routing algorithms. 1-1-5 network characteristics (uncertainty of the physical environment) In wireless sensor networks, sensor nodes are placed in a dynamic and unreliable environment. The topology of the network is constantly changing, and these changes are caused by factors such as the end of node energy, physical damage to the node, or disconnection between nodes. A suitable routing protocol should be properly aligned with topology changes. 1-1-6 Data Redundancy Because there is a high data redundancy in wireless sensor networks and the same information may be obtained from different nodes, data consensus techniques can be used in some nodes. Data consensus can greatly reduce the number of information packets that are transmitted to the main station in the network, and therefore has a positive effect on the lifetime of the network. 1-1-7 Diversity of applications of wireless sensor networks Considering that these networks have different applications, it cannot be claimed that a routing protocol is optimal for all applications. Some applications, such as industrial processes or military industries, require fast response and low latency. Other applications, such as temperature and light measurement, are less sensitive, and in them, the lifetime of the network is a higher priority. Considering that in most applications, it is not cost-effective to implement a real wireless sensor network in order to test the performance of a routing protocol, that is why simulation software is used. In these simulators, the network of routing algorithms can be simulated according to its application in the real environment. In the fifth chapter, a number of simulation software for wireless sensor networks have been reviewed. 1-2 Characteristics of wireless sensor networks Energy limitation makes most of the routing protocols provided in other wireless networks not suitable for wireless sensor networks. For example, the flood transmission that is used in computer networks has a high cost for wireless sensor networks and significantly reduces the lifetime of the network [7]. Of course, to implement flood transmission in wireless sensor networks, an alternative method is used, which is known as the rumor method [8]. In this method, when a node wants to send data to another node, it randomly selects a small number of its neighbors, but in the flooding method, all neighbors are selected. Wireless sensor networks have characteristics that distinguish them from other networks such as MANET [3] and mobile phone systems [4]. Some of these features that have been considered in this research are:

High density of nodes in the environment: usually, wireless sensor networks have a higher density than other networks, and therefore the magnetic waves in the environment of these types of networks are more. Running out of energy cannot be recharged or replaced.

Limitation of data storage, processing and transmission: compared to other networks, sensor nodes have little storage space and are very limited in terms of the amount of calculations and also the length of the distance they send data.

Automatic network formation: in this type of network, when a node is placed in the environment, it automatically communicates with the surrounding environment and other neighboring nodes.