Research Of Multi-Channel MAC Protocol Based On Real-Time Embedded Operating System In Intelligent Agricultural System

Intelligent agricultural system is intelligent system, which collects agricultural information remotely and analyses this information to make decisions. Wireless sensor network has been used more widely in intelligent agricultural system as a new type of communication technology. Usually the sensor nodes are composed of single-chip, a variety of sensors and wireless communication module. The energy, processing capacity, memory and communication ability of the sensor nodes are limited. Medium access control layer (MAC) is the key to the energy consumption of sensor nodes. This paper aims to develop the low-power multi-channel MAC protocol based on real-time embedded operating system intelligent agricultural system. The content of this paper covers the hardware design of sensor nodes, the improvement of embedded operating systems as well as the software design of multi-channel MAC protocol for the purpose of reducing the power consumption of the sensor nodes and extending the life of sensor nodes.The first part of the paper is dedicated to an introduction to the hardware design of sensor nodes. This part serves as a hardware platform of the entire system. Sensor nodes consist of core module, power module, wireless communication module, data acquisition module, and RS-232 communication module. The power consumption of the sensor node's hardware circuit occupies a great part in that of the wireless sensor networks and rationality of its design has a great impact on the life of sensor nodes. The experimental results show that the power consumption of the sensor nodes can be reduced and its life span can be extended through a rational design on the hardware.Then the author moves to an exploration into the improvement and realization of the embedded operating system. This part mainly includes porting of embedded operating system, time management and task scheduling. The time management, as the heart of the entire operating system, affects the system's response time and power consumption of the operating system. The current research chooses the time slices which are repeatedly changed according to the tasks and hardware conditions instead of the traditional fixed time slices so as to ensure the response time of the system and reduce its power consumption. Task scheduling controls the implementing sequence of each task by giving the highest priority to the task that needs an urgent implementation.Finally, the author probes into the design and realization of multi-channel MAC protocol. This part includes pseudo-random channel sequence, the neighbor table management, time synchronization, neighbor discovery and sending or receiving data. Pseudo-random channel sequence and time synchronization ensure that each node knows the work information of surrounding neighbors which are in the one hop range. Neighbor discovery makes each node know the nodes surrounding. By predicting the destination node channel, each node can communicate with each other. Every node works on the different channels at a specific moment, which decreases channel conflicts, shortens the idle listening time and thereby reducing the node power consumption.