Self-adjustable Active Sequence To Reduce Latency In Duty Cycled Wireless Sensor Networks

The wireless sensor networks(WSNs)have wide application prospects,which are composed of many sensor nodes with simple hardware and small size to realize the perception of the surrounding environment.In WSNs,the duty cycle mechanism is widely used by nodes to sleep and wake up periodically.However,this mechanism increases latency while saving energy consumption,posing challenges to data routing.In order to solve the above problems,this thesis proposes a Self-adjustable Active Sequence(SAC)scheme to focus on energy consumption indicators and achieve a low-latency routing scheme.The main innovations of this scheme are as follows: first of all,the SAC scheme divides the continuous wake-up time slots into multiple shorter time slots,which can effectively reduce the waiting delay.Second,SAC scheme utilizes the remaining energy to increase the duty cycle of nodes in the far sink area,reducing latency without compromising lifetime.Third,by reducing the size of the forwarding nodes set,the storage space of the routing table can be effectively reduced.It has better performance in reducing the delay and the routing table length through both theoretical analysis and experimental results.The experimental results show that the delay can be reduced by33.0% if and only if the consecutive wake-up time slots are divided into several segments.And by making full use of the energy in the far sink area to increase the duty cycle,the delay can be further reduced by 9.9%.When reducing the size of the forwarding node set,the routing table length can be further reduced by 29.0%.Further considering the unreliability of wireless transmission in WSNs,this thesis proposes an Active Sequence Modification based Opportunistic Routing(ASMOR)scheme based on wake-up sequence adjustment.While improving reliability,the delay is reduced by adjusting the wake-up sequence of nodes within the sending range of the last two hops.The innovations of this scheme are as follows: First,the ASMOR scheme combines the advantages of the duty cycle mechanism and opportunistic routing.While the duty cycle mechanism saves energy,opportunistic routing can significantly improve transmission reliability.Secondly,the ASMOR scheme avoids the repeated and invalid forwarding of data through the message confirmation mechanism.In opportunistic routing,data is sent only after the number of wake-up nodes reaches the threshold.After the node receives the data successfully,it needs to return an acknowledgment message.If the acknowledgment message is received by other nodes that are receiving the data,other nodes stop receiving data and no longer forward it.Third,the ASMOR scheme uses the message monitoring and forwarding mechanism to prepare the next two-hop nodes for data reception in advance,which reduces the waiting time for the next-hop node to continue forwarding data after receiving the connection termination request from the previous-hop node The experimental results show that ASMOR can reduce the delay of the next two-hop relay nodes,and the delay of the first-hop node is reduced by 35.0%.