Typical case analysis of wireless sensor networks for environmental monitoring

1. Project Overview

1.1 Introduction

This paper introduces an environmental monitoring system based on wireless sensor networks. The system mainly includes the detection of temperature, humidity, light, precipitation, wind speed, dust, wireless transmission and reception of signals, and analysis and processing of signals.

The system monitors the environment within a certain range in Xinjiang through wireless sensor nodes. Multiple wireless sensor nodes use wireless routing nodes and base stations to form a wireless sensor network, which uploads data to the host computer of the central monitoring system for data analysis and display, thus realizing real-time monitoring of the specific environment and making reasonable allocation of resources in a timely manner.

1.2 Project Background/Motivation for Topic Selection

Xinjiang has a temperate continental climate. The winter is long and cold, the summer is short and hot, and the seasons change dramatically in spring and autumn. The annual average temperature is 10℃ in southern Xinjiang, 5-7℃ in the Junggar Basin in northern Xinjiang, and 2.5-5.0℃ in Altai and Tacheng. The average temperature in southern Xinjiang in January is 10-12℃ higher than that in northern Xinjiang, and 2-3℃ higher in July. The daily temperature difference can reach an average of 12-15℃, and the maximum can reach 20-30℃. The relative humidity in summer and the absolute humidity in winter in Xinjiang are not high, forming the characteristics of dry hot summer and dry cold winter. The average annual precipitation in the whole region is 145 mm, which is only 23% of the national average annual precipitation of 630 mm, while the evaporation is about 200 mm, less than 100 mm in southern Xinjiang. The snowfall in northern Xinjiang and mountainous areas accounts for about 1/3 of the annual precipitation.

Xinjiang has many strong winds, with winds stronger in northern Xinjiang than in southern Xinjiang, stronger in the Gobi Desert than in mountainous areas, and stronger in the basin edge than in the basin hinterland. Strong winds (i.e. winds of level 8 or higher) are the main agricultural meteorological disasters in Xinjiang. The northwest of northern Xinjiang, eastern Xinjiang, and eastern southern Xinjiang are high-value areas for strong winds. The number of days with sandstorms in the Tarim Basin is generally more than 30 days, while in some areas of northern Xinjiang and eastern Xinjiang it is less than 20 days. In recent years, dust weather has occurred more frequently in southern Xinjiang than in the past.

Xinjiang has abundant sunshine, with the total annual solar radiation ranging from 542.10 to 646.35 joules per square centimeter, second only to the Qinghai-Tibet Plateau.

In general, Xinjiang's natural ecological environment has the following characteristics: a vast territory but a small oasis area; arid climate and large temperature changes; abundant total water resources but uneven distribution in time and space; a large land area but a small forest area; poor soil quality and desertification; and sufficient salinity, which occupies an important position in the country. The above natural ecological environment characteristics determine that once Xinjiang is polluted and destroyed during development and construction, it will have irreversible and permanent consequences. Therefore, in human economic activities, we must respect the laws of nature and pay attention to the basic characteristics of Xinjiang's natural ecological environment.

From the above overview, we know that in the actual production and life process, it is difficult and necessary to conduct a certain degree of environmental testing in Xinjiang. The use of wireless networks ensures the real-time and effectiveness of data transmission, which has certain positive significance for life and production activities.

2.1 Functional requirements

The nodes designed with mega128 chip can not only monitor the temperature, humidity, light, precipitation, wind speed, and dust data in real time, but also upload the collected data to the EVK1105 host embedded with the tinyos operating system through the routing node via the cc1000 wireless protocol. The EVK1105 host simply processes and analyzes the signal. On the one hand, it can intuitively display the collected data on the LCD screen. On the other hand, if necessary, the data will be fed back to the host computer in real time, and the host computer will make more detailed judgments and then take positive measures.

Figure 1 Functional implementation

2.2 Performance requirements

 1. The data collection nodes and routing nodes composed of mega128 can realize data collection, routing search and wireless transmission functions

 2. The tinyos operating system embedded in the host implemented by EVK1105 needs to process and analyze the received data and display it on the LCD screen in real time and provide feedback to the upper computer.

3. Both data acquisition nodes and routing nodes should meet the following requirements: low power consumption, fast networking, fast and accurate data acquisition, and good validity and security of real-time transmitted data.

3. Solution Design

3.1 System Function Implementation Principle

Figure 2 System hardware structure diagram

3.1.1 Data Transmission:

Using mega128 as a data collection node and routing node will achieve the following functions

Figure 3 Data collection and transmission

3.1.2: Data transmission network:

The more representative MAC protocols include TMAC, SMA, CWiseMAC, BMAC, DMAC, etc. Routing protocols include Gossiping, SPIN protocol, LEACH protocol, TEEN protocol, etc. We choose ordinary RF chips and can customize the communication protocol. Considering performance, cost, and power consumption, RFM's TR1000 and Chipcon's CC1000 are ideal choices. These two chips have their own strengths. TR1000 has lower power consumption, CC1000 has higher sensitivity and longer transmission distance. Common wireless chips include Nordic's nRF905, nRF2401 and other series chips, but because of their high power consumption, low receiving sensitivity, and greater development difficulty, they are rarely used in actual wireless sensor networks.

Figure 4 Data transmission diagram

3.1.3: Data analysis and processing:

TinyOS is an open source operating system developed by UC Berkeley, designed for embedded wireless sensor networks. The component-based architecture of the operating system enables rapid updates, which in turn reduces the code size limited by the memory of the sensor network. [page]

3.2 Hardware platform selection and resource allocation

3.2.1 Use mega128 microcontroller to implement routing and acquisition node modules.

3.2.2 Use EVK1105 as the node processing host in this project.

3.3 System Software Architecture

Figure 5 System software architecture

3.4 System Software Process

             Data acquisition node software flow chart Host software flow chart

M is the specified number of tests; N is the number of executions

              Wireless Data Transmission Power Management

3.5 Expected Results of the System

It can simultaneously monitor the temperature, humidity, light, precipitation, wind speed, and dust in a certain area in real time, and can realize fast networking, low-power data measurement and data analysis and processing.