Adaptive Medium Access Control In Wireless Sensor Networks

Easy installation and maintenance,less cabling costs,and mobility support motivate the ex-tensive use of Wireless Sensor Networks(WSNs)for industrial and factory automation,distributed control systems,automotive systems,military defense,environment monitoring,and many other applications.Also,with rapid developments of Internet of Things and Cyber Physical System,which are mainly derived from WSNs,WSNs has been considered as one of the 21 most important technologies for the 21st century.Medium access control(MAC)layer protocol plays a fundamental role in supporting the high.performance of WSNs.This thesis focus on the design and optimization of traffic adaptation MAC protocols in WSNs.The contributions of this thesis are summarized as follows:1.Existing low-power MAC protocols only provide low throughput because of the fixed low duty-cycle.This often leads.to poor performance when dealing with time constrained burst traffic.We propose a new hybrid CSMA/TDMA MAC protocol,called Queue-MAC,that dynamically adapts the duty-cycle according to the current network traffic.The queue length of nodes is used as the network traffic indicator.When the traffic increases,the active C-SMA period is accordingly extended by adding dynamic TDMA slots,allowing thus to ef-ficiently handle burst traffic under real-time constraints.This protocol is implemented on the STM32W108 SOC chips.Through extensive experimental measurements,we showed that our queue length aware hybrid CSMA/TDMA MAC protocol largely outperforms the compared protocols.2.For enhancing the limited throughput in low duty-cycle multi-hop wireless sensor network-s,we proposed iQueue-MAC,a duty-cycle CSMA/TDMA hybrid MAC which can rapidly adapt to variable/burst traffic and maintain high energy efficiency.In light traffic condition,iQueue-MAC uses low duty-cycled CSMA mechanism to deal with scattered transmissions.When traffic increases,iQueue-MAC implicitly utilizes the queue length information to al-locate transmission slots to intensive senders.Since the slot allocation is triggered at the first sight of queueing existence,iQueue-MAC mitigates packet buffering and reduces the pack-et delay.Meanwhile,iQueue-MAC can run in both single and multi-channel modes.We implemented iQueue-MAC on SIM32W108 chips and conducted extensive experiments to evaluate its performance.The results showed that iQueue-MAC outperforms existing WSNs MAC protocols in terms of traffic adaptability and hence throughput.3.For enhancing the limited spectrum utilization in cognitive wireless sensor networks(C-WSN),we proposed a simple and efficient distributed protocol called ACCA for congestion regulation for CSMA-based C-WSN.By the protocol,when the primary channel is nearly saturated due to high traffic demands,secondary devices leave the primary channel and join some secondary channels,based on their own estimation of the congestion level.In the case of light traffic condition in the primary channel,a rejoining procedure is conducted to insert more.secondary devices to fully utilize the primary channel.The proposed congestion regulation protocol is implemented on STM32W108 chips that offer IEEE 802.15.4 standard communications for WSN.Extensive experimental evaluation results show that the proposed protocol can substantially improve the channel utilization,while demanding low signaling overhead even in non-stationary wireless environments.4.For optimizing the spectrum utilization of cognitive wireless sensor networks,we proposed a protocol of light complexity for congestion regulation in cognitive WSNs.This proto-col improves the channel utilization while ensuring predetermined performance for primary devices.Such a protocol dynamically changes the congestion level based on variations of non-stationary wireless environment as well as traffic demands of the devices,and keeps the optimal number of devices that leads to optimal use of the channel without sacrificing delay requirements of primary devices.The proposed protocol is implemented on STM32W108 chips that offer IEEE 802.15.4 standard communications.Experimental results confirm sub-stantial performance enhancement compared to the original standard,while imposing almost no signaling overhead.