Research Of Cross Layer Optimization Technology On Wireless Sensor Networks And Its Application

The cross layer design is one of the hot research issues in the field of communication network for the past few years. The traditional separate layer design method did really a good job in cable networks. However in wireless communication it has a great deal of limitations. For instance the multi hop route algorithm in network layer has little considerations of the impact from the physical and media access control layer; adequate utilization to the limited wireless and power resources are not able to be implemented by the separate layer stack.There is a simple network structure of wireless sensor network. If the whole system can be seen as an integral structure with the cross layer method, the performance of sensor network can be improved. Cross layer design builds an effective tunnel which helps the info exchange between low layer and high one. The upper layer will take actions to optimize the system performance by what it receives from the low layer. The separate layer design certainly will not be denied by the cross layer method but improved in the way of info management and sharing offered by cross layer method. The limited resources can be allocated in a more effective way in order to upgrade the network performance.The cross layer optimization technology is originated from cross layer design. This kind of tech adds a cross layer module into the traditional separate layer stack, which largely improves the communication ability between different network levels. The EZMAC/EZHOP stack has been brought out by Silicon Laboratory in 2010 which is simply a MAC protocol. Cross layer optimization to EZMAC is presented in this paper such as the integration of competition and TDMA, one system two baud rate, auto frequency selection, packet filter and channel error counter. This optimization helps a lot to smooth info transferring tunnel and provide reference to upper layer stack. Experiments have been made to demonstrate the priority of cross layer consideration.Time synchronization is one of the vital support technologies in sensor network. This paper describes a typical time synchronization algorithm based on cross layer consideration and presents the cause, crystal deviation, to the asynchronous phenomenon in sensor network. The crystal deviation has been corrected by the cross-layer MAC protocol. The experiment which is implemented by the oscilloscope demonstrates the practicability of this algorithm.The application to cross layer optimization is carried out in the wireless grain monitoring system. The hardware platform with Si1001 wireless MCU is designed and the cross-layer EZMAC protocol is explanted into all kinds of nodes in the network. Lots of trouble issues have been solved during the development process. Finally the wireless grain monitoring system has been deployed in a grain depot which belongs to the central government.In this paper, research efforts have been devoted to cross layer optimization technology, and a real WSN project based on this tech has been implemented. EZMAC protocol and time synchronization algorithm which are improved by this technology are introduced too. The implementation of hardware and software in wireless grain monitoring system illustrates the priority of cross layer optimization in wireless sensor network.