The Design And Implementation Of Fairness/Efficiency Oriented Protocol In MAC Layer For WSN

With the development of wireless communication technology, people’s demand for wireless sensor networks is growing. How to make the nodes fairly share the channel in order to extend network life and to promote the efficiency of network becomes a question which must be soluted. Therefore, the design and implementation of fairness and efficiency oriented MAC layer protocol has realistic meaning.The energy of WSN nodes is so limited. How to make the nodes relatively share the channel fairly in order to extend network life becomes one of the first consideration factors in wireless communication network. On the other hand, improving the channel utilization rate and reducing delay also becomes one of the factors which to be considered for WSN. On the above two factors, it is necessary to make deeply and detailed research and analyze IEEE802.15.4MAC layer protocol.First, in order to solute the questions mentioned above, based on the analysis of advantage and disadvantage of the current GTS mechanisms, this paper puts forward a priority-based fairness and efficiency oriented MAC layer algorithm and reduces the conflicting probability among nodes by sub-area competition and slotted scheduling. Secondly, this paper puts forward three feature parameters which measure the fairness index of the network and divides all the nodes into three priorities. Based on the theoretical modeling analysis, this paper improves the superframe structure in IEEE802.15.4, designs the frame structure and implements the improved algorithm. At last, the experiments prove the validity of the algorithm through fairness index and channel utilization. Combined with routing protocols and network topology structure, this paper analyzes the effects on the network layer by modifying the MAC layer algorithm.The results show that the study effectively solves the unfairness phenomenon which is produced by CSMA/CA mechanism and reduces the max backoff times and cache occupancy rate, which balances the distribution of network energy and increases the channel utilization ratio to extend the network life. At the same time, improved MAC layer protocol increases the effective paths number and changes the routing hop number. Therefore, it proves the algorithm which proposed in this paper is correct and effective respectively from MAC layer and network layer.