Research On Key Transmission Technologies In Low Duty-cycled Wireless Sensor Networks

Information perception,data collection and processing are the foundation for connecting the cyber world,physical world,and human society,and they are helping promote the development of future computer networks.With the development of Internet of Things(IoT)technology which has been widely applied in various fields of economy and society and with the change of internet access and energy supply,low power wireless sensor networks(WSNs),which combine information perception,data collection and processing,will appear in every aspect of social life and are bound to play a more and more important role in the coming “industry 4.0” era.However,there still has many challenges for low power WSNs applying in practical applications: accessing shared wireless channel in low power mode for data transmission is grossly inefficient under bursty traffic loads;it is difficult to coordiante the harnessing of transmission opportunities and saving the resource of shared channel and energy;it is hard to resove the contradiction between low dimensional link measurement and the demand for multi-dimensional link state in making transmission decision;lack of practical way to guarantee both reliablity and efficiency for adjusting individual sensor nodes through remote control,and so on.To address these concerns,this thesis focuses on feasible and practical theories and methods to achieve high-efficient and reliable data tranamission protocols,model multi-dimentional link properties for making appropriate transmission decision,and propose a ready-to-use protocol for effectively adjusting individual nodes under varisou network environment.The overall purpose of this thesis is to solve the efficiency problem in low power WSNs,making it more permeable to all aspects of social life with the rapid development of IoT.In summary,the major results and core contributions are as follows:(1)Collision avoidance for channel access.By exploring the temporal diversity of multiple quickly replied acknowledgements(ACK),a receiver can instantly recognize potential senders and then subsequently polls individual senders one by one.Since the period of one ACK transmission is very short,the overhead of coordination process is low.The proposed scheme does not need any auxiliary control overhead in distinguishing potential senders.It fundamentally solve the data collision problem in low power WSNs.Evaluation results demonstrate that it can effectively avoid data collision and mitigate influence of hidden terminal problem.Based on this scheme,it is feasible to guarantee energy efficiency and network reliability for various WSN applications with bursty traffic.(2)Duplicate detectable opportunistic forwarding.A duplicate-detectable opportunistic forwarding(DOF)protocol is proposed for low-duty-cycled wireless sensor networks to exploit potential forwarding opportunities and suppress duplicate transmission.Instead of direct data transmission,in DOF,a sender sends a probe and asks the potential forwarders to acknowledge the probe respectively in different time slots.By utilizing the temporal diversity of multiple acknowledgements,the sender detects the quantity and differentiates the priority of all potential forwarders.The sender then forwards its data in the deterministic way to avoid multiple forwarders hearing the same packets.With the light-weight mechanism to suppress duplicates,DOF can dapt to various traffic loads in duty-cycled sensor networks and enhances the system performance with respect to both network yield and energy efficiency.(3)Data retransmission.This dissertation proposes a practical and general supporting layer(Rxlayer)for data retransmission.By using conditional probability models,Rxlayer captures the temporal and spatial link properties without inducing noticeable overhead.According to Rxlayer,data forwarding protocol could assess the success rate of the next transmission over the currently used link.And once the currently used link is seriously corroded,sender will retransmit data over a back-up link that temporally has the highest delivery probability for a while rather than has the best statistical-based link quality.Experimental results show that RxLayer can improve data delivery reliability and energy efficiency in various scenarios compared with the state-of-the-art retransmission strategy.(4)Remote control.This dissertation proposes TeleAdjusting to remotely control any individual node in a duty-cycled network.TeleAdjusting develops a coding scheme for addressing on the cost-optimal reverse routing tree.In the address-coding of each node,all its upstream relay nodes are implicitly encoded.Then through a distributed prefix-matching process between the local address-coding and the destination addresscoding,a packet used for remote control is forwarded along a cost-optimal path.Moreover,TeleAdjusting incorporates opportunistic forwarding into the addressing process,so as to improve the network performance in terms of reliability and energy efficiency.TeleAdjusting is implemented in TinyOS and evaluated in an inddor testbed.The results demonstrate that compared with the state-of-the-art approaches,TeleAdjusting can provide high performance of remote control,which is as reliable as network-wide flooding and much more efficient than the remote control through a pre-determined path.