| A new epoch,in which micro computing technologies are widely applied in people's economic and social life,has begun with the appearance of ubiquitous computing theory. As a part of ubiquitous computing technology, the Wireless Sensor Network (WSN),which combines with micro electrical machine, communication networks and sensor technologies,can be deployed in any region to monitor the specific objects and send back the acquired data to end-user through the method of multiple hops transmission based on the cooperation of WSN nodes and the data aggregation of the sink node. As a bridge between the physical world and human beings, WSN enhances our capabilities of knowing the world around us.The main characters of WSN are application-oriented and data-centered. The most significant task of WSN is that it should transmit the data of emergent events and user-interested information from monitoring regions timely and reliably to the sink node with pre-defined accuracy. It is required for the WSN nodes to support and cognize packets with priorities, meanwhile the nodes should provide corresponding quality of service for these packets. The protocols,designed for traditional computer network,could not be implemented directly on the WSN due to the communication methods,hardware restrictions and other factors. Based on the existing protocols and the guidelines of transmission protocol design for WSN, a new transmission protocol, Priority First Hierarchical Collection Transmission Protocol (PFHCTP), which provides different service qualities according to priorities carried by the packets, is proposed in this paper. The PFHCTP is composed of three individual modules, which are link quality evaluation (LQE) module, routine management (RM) module and packets transmission schedule (PTS) module. In order to meet the requirements of quick adjustment to the dynamical changes of WSN, PFHCTP shares information among different modules. LQE module is responsible for evaluating the qualities of the links between the local node and its neighbor nodes by using the statistical information of beacons from neighbor nodes and the cache occupation of local node. RM module mainly maintains multiple effective routes to the sink node in route pool based on the route information from neighbor nodes. While PTS module mainly has two functions, one, which is based on the congestion of local area acquired from the cache occupancy and payload of channel, is to inform the lower-level nodes to slow down the frequency of sending packets or transmit the packets by using other route. The other one is to determine the sequence of packets transmission by using priorities carried by packets to ensure that the high priority packets could reach the sink node timely and reliably.The main works of this paper are listed as follow:①Based on the guidelines and methods of transmission protocol design for WSN, the principles of protocols used now are researched deeply, and the advantages and disadvantages of these protocols are well analyzed.②Focusing on the disadvantages of existing protocols, PFHCTP is designed based on the standard WSN protocol stack by using the thought of cross-layer.③The PFHCTP is implemented on TinyOS platform by using nesC, and it could run well through debugging.④The comparison of performance of PFHCTP with another existing protocol, which is carried by the TinyOS, is accomplished on the TOSSIM which is also provided by TinyOS.The results of simulation tests proved that PFHCTP could cognize and support packets with priorities. And, it guarantees the packets of high priority applications to obtain advantages in the transmission delay at some extents. Consequently, it meets the pre-defined goal. PFHCTP, which supports multiple packets of different priorities, accelerates the WSN's application to reach a new stage, in which WSN could run multiple tasks to accomplish kinds of different functionalities simultaneously. It could play an important role in the process of further applications in the Internet of Things as well. |
PDF Full Text Request