Research On Energy-efficient And Low-latency MAC Protocol Of Wireless Body Sensor Network

Wireless body sensor networks(WBSNs)are mainly used to monitor human health.Media Access Control(MAC)protocols play an indispensable role in ensuring proper function of WBSNs.However,the proposed MAC protocols still have large energy consumption and latency.In order to reduce energy consumption of sensor nodes and latency of data transmission,we propose two MAC protocols for WBSNs,which are respectively applied to higher traffic WBSNs and smaller traffic WBSNs.The main contents are summarized in the following:1)An energy-efficient and emergency-aware MAC(EEEA-MAC)protocol is presented for higher traffic WBSNs.In order to reduce energy consumption and reduce latency of emergency data,EEEA-MAC proposes that source nodes adopt CSMA/CA mode while relay nodes adopt hybrid CSMA/CA-TDMA mode to send data.Moreover,superframe structure is designed in EEEA-MAC,which has three variations with the number of nodes with emergency data.EEEA-MAC proposes that the source nodes use CSMA/CA instead of hybrid CSMA/CA-TDMA,so that emergency data can be sent in a competitive way in time.At the same time,with CSMA/CA,nodes can compete to send data autonomously,avoiding the transmission of many beacons with TDMA,which can reduce energy consumption.Unlike existing methods,EEEA-MAC uses sense mechanism during contention free period.Before transmitting data,a node will sense whether there is urgent data to decide whether to send its own data,so that emergency data can preempt slot of other nodes,which can handle urgent data in time.Simulation results show that,on the basis of two-hop network,EEEA-MAC exhibits greater logical advantages comparing to IEEE 802.15.4 and IEEE 802.15.6 in terms of energy consumption and latency.2)A MAC protocol based on priority gradient to increase the number of slots is proposed for smaller traffic WBSNs.Firstly,this method divides the priorities of nodes into four levels according to the data type and the current health parameters of nodes.Secondly,it increases the number of slots according to the priority gradient and determines the candidate slot scheme,and then the candidate slot scheme with the biggest utility is selected as the sub-optimal slot allocation scheme according to the utility formula.Finally,it determines the order in which each node transmits each data according to the priority and the sub-optimal slot allocation scheme of nodes.This method ensures that the complexity of slot allocation is reduced and the delay of data transmission is shortened under the premise of fair slot allocation.Simulation results prove that this method has logical validity in terms of the total utility of nodes and the latency of data transmission.