About the sleep timing of nodes in wireless sensor networks

Dissertation for Master's degree (M.Sc)

Abstract:

A sensor network consists of a large number of sensor nodes that are widely distributed in an environment and gather information from the environment. Since the nodes are powered by batteries, an important issue that is considered in sensor networks is energy consumption. One of the methods that are very common in these networks to reduce energy consumption is to sleep the nodes in There are times when their workload is lower. Putting each part of the sensor node to sleep will have a different effect on energy consumption.

The most energy consumption is in the transmitter part, which is controlled by MAC protocols. S-MAC is one of the famous MACs designed specifically for sensor networks. In this MAC nodes save energy through sleep and activity cycles. They have energy. One of the widely used and data-oriented methods in these networks is the directed propagation method.

In this dissertation, a protocol derived from the MAC protocol will be presented, which is specific for directed propagation routing in sensor networks. This protocol has implemented the energy saving features that exist in S-MAC and is able to adapt to the network load in different conditions.

In the application layer, energy consumption can be reduced by using the settings that are made in the activity of this layer. If the node has the possibility to control the activity of the sensor unit, it is possible to reduce the energy consumption by scheduling the activity of this unit and putting it to sleep in the conditions that the application allows. Since the number of nodes used in the network It is usually higher than the number of nodes required to provide coverage on the network, so some of these nodes can be put to sleep and the monitoring work done periodically. Here, a dynamic and probabilistic method to provide K-layer coverage required by the application on an intruder in the network is presented. This method is able to achieve very high savings and at the same time provide the required coverage. which they have nurtured for years, to put into practice.

Sensor networks are a technology that allows us to monitor a wide physical space accurately and imperceptibly.

A sensor network consists of a large number of sensor nodes that are widely distributed in an environment and collect information from the environment. The location of sensor nodes is not necessarily predetermined and clear. Such a feature makes it possible to leave them in dangerous or inaccessible places

On the other hand, this means that the protocols and algorithms of sensor networks must have self-organizing capabilities. Another unique feature of sensor networks is the ability to cooperate and coordinate between sensor nodes. Each sensor node has a processor on its board, and instead of sending all the raw data to the center or to a node that is responsible for processing and concluding information, it first performs a series of basic and simple processing on the information it has obtained, and then sends the semi-processed data.

Although each sensor alone has little ability, the combination of hundreds of small sensors offers new possibilities. In fact, the power of wireless sensor networks is in the ability to use a large number of small nodes that are able to organize themselves and be used in many cases such as simultaneous routing, monitoring of environmental conditions, monitoring the health of structures or equipment of a system. Each of the nodes is equipped with a number of sensors (such as sound, temperature, infrared, vibration, radiation or any other sensors), a microprocessor, a radio receiver/transmitter and a power supply. The nodes of this network can be installed on the ground, in the air, underwater, on the human body, or on vehicles. The sensor nodes, with the help of each other, try to collect environmental information and transfer them to a center called a sink. 1-1 Introduction of wireless sensor networks Today, the discussion of remote control and monitoring systems is one of the most challenging topics in the field of electronics and computer science.Therefore, research is always looking for a solution to meet specific conditions and expected expectations. Under the conditions of the same quality, the lower the cost-effectiveness ratio, the higher the popularity of the method.

Recent advances in the field of smart sensor systems, wireless telecommunications, and digital electronics allow the construction of small, low-power, and low-cost sensor nodes that can communicate wirelessly. also have According to the different performance of the sensor networks, each node can be formed from various components according to the defined functions, but in general, each node is formed as a general component, which means: central processing unit, radio transmitter and receiver, power source that can be combined through solar cell batteries, energy source of the system. provide a number of sensors that collect the desired data, such as external storage if needed, GPS locator and other components that can be included in each node depending on the different applications. Generally, a wireless sensor network includes a large number of these nodes, whose data is considered collectively to measure a parameter, that is, all the collected information of a parameter in a node of The network, which is usually called the base station [1], is processed and the actual value of that parameter is estimated relatively accurately. In these networks, the failure of a network node has almost no effect on the estimated value.

In wireless sensor networks, a large number of sensor nodes are located inside the desired location or very close to it for measuring the desired parameter. The location of these nodes is not designed in advance. This problem helps in the simple placement of sensors in the network, but instead, the protocols used for these networks must be self-adjusting or self-organizing. Due to the fact that these sensors have a processor inside, in order to reduce the volume of data transmission, these sensors only send the required data after processing the primary data. Wireless sensor networks are similar to mobile adhoc networks (MANET) in many ways, but the protocols used for adhoc networks are not suitable for wireless sensor networks. In adhoc networks, the main issue for designing protocols is quality of service [2] (Qos), while in wireless sensor networks, the main limitation for designing protocols is the limited energy of sensors. In fact, protocols that minimize the power consumption of sensors are more important for wireless sensor networks.

There are many protocols, techniques and concepts of traditional wireless networks such as cellular networks, ad hoc networks and Bluetooth, which are applicable and are currently used in wireless sensor networks, but the differences cause the need for new protocols and techniques.

In general, the main differences between wireless sensor networks and adhoc networks are It is as follows:

The number of network nodes in wireless sensor networks is much more than adhoc networks.

Sensors in wireless sensor networks are compactly placed.

Sensors in wireless sensor networks are more prone to failure.

The coordination of wireless sensor networks is constantly changing.

In most wireless sensor networks, communication is broadcast. For adhoc networks, communication is point-to-point. Sensors are limited in size, power, computing power, and memory. The difference between sensor networks and other networks is in the nature of data. The axis [3] and also the resources of radio and processing are very limited in them, so that the proposed methods for data transmission in other networks and even networks that have a similar structure to sensor networks (such as ad hoc networks) cannot be used in these networks.

Techniques and methods used in such networks are highly dependent on the nature of the network application, network structure, atmospheric and environmental conditions, and limitations. Effective factors are network performance parameters and cost.

The main goal of all the efforts to provide solutions is to have a system of simple, easy and low-cost control systems, which can finally respond to the needs of our customers in the face of limitations (broadband, energy, environmental interference, feeding, etc.). ) To provide slow standing and general conditions according to the request and desire (transmission of large volume of information with rich content, high durability and longevity, low cost, etc.)