Energy Priority Based MAC Protocol Design For Passive Internet Of Things Using Ambient Backscatter

With the large-scale deployment of the Internet of Things,spectrum resources have become increasingly scarce,and replacing batteries for a large number of nodes has gradually become a challenging task.Improper disposal of discarded batteries can easily cause environmental pollution.Passive Io T using ambient backscatter does not need to set up additional RF sources,saving valuable spectrum resources,nodes have the ability to collect energy from surrounding RF signals,get rid of the dependence on batteries,and can quickly promote the development of Io T large-scale application.Multiple nodes in the network may have data conflicts when transmitting data,and the same is true in passive Io T.The Medium Access Control(MAC)protocol allocates limited channel resources for passive Io T nodes and reduces collisions during data transmission,which is a key factor affecting network performance.Passive Io T energy harvesting rate using ambient backscatter is low,and the energy stored by nodes is an extremely valuable resource.How to reduce the collision of nodes during data transmission and reduce the energy consumption of nodes as much as possible is the key to the design of the MAC protocol.This paper proposes energy priority based passive Io T MAC protocols using ambient backscatter: EP-MAC(Energy Priority MAC)and improved EP-MAC.EP-MAC proposes the concept of collision domain.Nodes are divided into several collision domains with different transmission priorities according to their remaining energy.Nodes with more remaining energy have higher transmission priorities in the collision domain.Nodes in different collision domains reduce the probability of collision with each other through different fixed waiting periods,while nodes in the same collision domain further reduce collisions through random backoff durations.Due to the dynamic characteristics of node energy,nodes with lower transmission priorities will gradually increase their own priorities with the accumulation of energy,thereby ensuring the fairness of node data transmission.The improved EP-MAC adds the validity period of the node data as one of the decisions of the node to divide the collision domain,and optimizes the scheme of the node to divide the collision domain considering the uneven energy distribution in the network.The experimental results of the NS-3 network simulator show that compared with CSMA/CA and pure ALOHA,EP-MAC has a certain improvement in network throughput,reduce collision rate,and data delivery rate.When the number of nodes is 50,compared with CSMA/CA,EP-MAC improves the throughput by 46.1%,reduces the data collision rate by19.7%,and improves the data delivery rate by 31.5%.Besides,EP-MAC has better network energy characteristics.It provides a priority mechanism that the other two protocols do not have.The improved EP-MAC divides the collision domain more reasonably when the network energy distribution is not uniform,and has better performance than EP-MAC,and can better guarantee the node data transmission fairness when the capacity of the energy storage element of the passive Io T node is large.