Design And Implementation Of An Adaptive MAC Based On Battery Discharge Characteristic In Wireless Sensor Network

Wireless sensor network is a novel technology for acquiring and processing information, which is made by the convergence of wireless communication, distributed computation, embedded system and micro-electro-mechanism technologies. As the key parts of the WSN design are distinguished from the traditional wireless network, lots of designing principles came forth. Wireless sensor network protocols of various levels have not been standardized. Most research of WSN protocol is focused on WSN application, energy consumption, traffic affording, and network connectedness and so on.The dissertation mainly researches on the wireless sensor network MAC protocol based on the characteristic of primary battery discharging. Firstly we present an analysis for recent studies on WSN and then give a classification of the challenges and guide lines for MAC protocol design. Current MAC design for wireless sensor network can be classified into three categories: contention-based protocols, fixed protocols and hybrid protocols. Among the MAC protocols, every one is to allocate the shared wireless channels among sensor nodes as fairly as possible with energy consumption saving. But every protocol has drawbacks at the same time.Secondly, the study in primary battery helps us better understand the electrochemistry principium. Alkaline zinc-manganese battery exhibits a specific quality and attributes on pulsed discharge. A pulsed discharge allows charge recovery during the idle periods. We derive the improvement to battery lifetime that results from pulsed current discharge which can be introduced to the MAC protocol design.Based on the simplicity and robustness of CSMA and the collision-free advantage of TDMA, the dissertation proposes BA-MAC, a novel hybrid MAC protocol of TDMA and CSMA, which is particularly based on the characteristic of battery discharge BA-MAC succeeds to the staggered wakeup schedule from D-MAC, an adaptive energy-efficient and low-latency MAC for data gathering. According to the analysis and investigation of battery discharging, BA-MAC utilizes this data gathering tree structure to achieve both energy efficiency and low packet delivery latency. BA-MAC staggers the active/sleep schedule of nodes in the data gathering tree in term of the battery discharging behavior. This allows most nodes in the wireless sensor network owing the sum of active period approaching the lifetime of battery maintenance. Unsymmetrical time synchronization is employed to solve the problem when parent nodes and children nodes communicate with each other but they may not awake at the same time, that causing idle listening or packet error. Self-reacting adjustment on the super frame and active period is proposed to command nodes on the multihop path to remain active longer when the traffic is heavy.We have implemented BA-MAC on a hardware platform of wireless sensor network, which is developed by our group. Our experiment results have shown that BA-MAC can be applied in wireless sensor network. In addition, it has proved BA-MAC has good performance on throughput, latency and fairness which could satisfy practical requirements.