| Benefit from the rapid development of the technology of manufactures, communications and networks, wireless sensor networks (WSN) have broad application prospects in the fields of the natural environment, the transportation, the military, the health, the space exploration, the business and life. As a starting point, this paper will describe the details of the wireless sensor network nodes structure and the means of communication. And it will also introduce the characteristics such as the limited communication capability, the limited energy, the limited computing capability, the large quantities of sensors, the wide range of distributions, the dynamic network, the large-scale distributed triggers and the enormous data flow sensed. And accordingly put forward the wireless sensor network performance evaluation indicators.Subsequently this paper will introduce the protocol stack of WSN, including the physical layer, data link layer, network layer, transport layer and application layer. The emphasis is the media access control (MAC) layer in the data link layer. The concept, the network characteristics and the requirements of design are all referred to.One of the tasks of this paper is to classify the WSN MAC protocols in the different ways. According to the style of the nodes communication, they can be divided into Reservation-based and Contention-based. According to the count of the wireless channels, they can be divided into Single-channel and Multi-channel. According to the scope of the nodes communication, they can be divided into Node-based and Cluster-based. According to the protocols referred to, they can be divided into Single-layer and Cross-layer approaches. In addition, it takes the specific protocols as examples. It will describe the Reservation-based protocols such as WiseMAC, Lightweight MAC (LMAC), Distributed Energy-aware MAC (DE-MAC) and Traffic-Adaptive Medium Access (TRAMA). It will describe the Contention-based protocols such as Sensor-MAC (S-MAC), Timeout-MAC (T-MAC), Dynamic Sensor MAC (DSMAC) and Data-gathering MAC (DMAC). It will describe the representative of Cross-layer approaches, Geographic Random Forwarding (GeRaF) . It will describe the Cluster-based protocols such as a Clustering Algorithm based on Node Correlation (CANC) and a Clustering Algorithm Based on CH Selection Model. It will also describe Wakeup channel which represents the Multi-channel protocols. This paper will select OMNeT++ to simulate CSMA which represents the traditional protocols, LMAC which represents the Reservation-based protocols, T-MAC which represents the Contention-based protocols and so on. The simulation results from the states of nodes, energy consumption, packet delay and the network conflict rate will be compared and summed up. After that, such conditions as the scale of the network, topology of the nodes and the application will be modified. More data will be extracted from several simulations and be analyzed. Meanwhile this paper will introduce WSN simulation tools which were commonly used, including the Network Simulator 2 (NS-2), J-Sim, TinyOS Simulator (TOSSIM), Objective Modular Network Testbed in C++ (OMNeT++).Another major work of this paper is that three special WSN applications oriented protocols are posed. They are HMAC, AMAC and HAMCP. HMAC protocol is designed for heterogeneous WSN and HMACP for special situation. The simulations will proof the lower energy consumption and the longer survival time. AMAC protocol is designed for WSN with the aggregating nodes and it is proofed to be more efficient in radio. As to WSN with the mobile nodes, it will analyze the reason that S-Mac does not fit for the application and the solution will be put forward to improve the protocol.Finally, it will conclude the whole paper and the next research direction is special application oriented protocol and general protocol stack. It predicts that thousands of enterprises will start using technology of WSN and millions of human beings will benefit from the variety of related applications. |
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