Data Predicted Wakeup Based Duty Cycle MAC for Wireless Sensor Networks Presented By: Muhammad Mostafa Monowar Networking Lab Kyung Hee University. Authors: Muhammad Mostafa Monowar, Kyung Hee University. Md. Obaidur Rahman, Kyung Hee University. Choong Seon Hong, Kyung Hee University. Cho Jin Woong, Lee, Korea Electronics Technology Institute Hyun Seok,, Korea Electronics Technology Institute

Presentation Outline  Problem Statement  Contributions  Preliminaries  Design of DPW-MAC  Simulation  Conclusion

Problem Statement  Various periodic applications of Wireless Sensor Network i.e. structural health monitoring, environmental monitoring, etc. requires the meeting of certain QoS (i.e. delay) under severe resource constraints.  Considering energy as a pioneer resource, several duty cycle MAC have been proposed for WSN.  The design of an energy efficient MAC faces several challenges:  Balancing between delay and energy.  Requires high medium utilization.

Contributions  We propose Data Predicted Wake-up based duty cycle MAC (DPW- MAC) exploiting the periodicity of data with the aim of maintaining lower delay and high medium utilization along with duty cycle.  Handling of multiple packets at a time to propagate as much data packets from the upstream senders at each hop in a single cycle reducing end-to-end delay.  Performed simulation using ns-2 to measure the effectiveness of our approach.

Preliminaries Assumptions:  We consider periodic applications in which nodes generate data at a fixed interval.  For applications with multiple sources and one sink, the data delivery paths from source to sink are in a tree structure.  Sensor nodes are fixed without mobility and that a route to the sink is fairly durable, so that a data gathering tree remains stable for a reasonable length of time.  All nodes transmit to their data to single path (i.e. each node can have only one parent).  The sink will inform the starting time of data generation and data generation interval.

Preliminaries Definitions: RxOP (Reception Opportunity): The maximum duration the receiver is allowed to receive packets from the upstream senders is termed as Reception Opportunity (RxOP). The RxOP value is a system parameter; TxOP (Transmission Opportunity): The maximum duration that a sending node is allowed to transmit packets is known as Transmission Opportunity (TxOP). The value is selected dynamically.

Design of DPW-MAC Data Gathering Tree  Initially, all the nodes in the network will remain active for a particular period.  Each source node in the network starts data generation at t 0, which is determined by the sink.  The source nodes generate data periodically at every t p seconds.  Every non leaf nodes send beacon to its immediate upstream nodes at t 0.  All the nodes who received beacon from their downstream nodes will adjust their clock with respect to the clock of the downstream nodes.

Design of DPW-MAC   Every sender is aware its receiver’s RxOP limit. During the back off period, if the sender’s waiting time exceeds receiver’s RxOP limit it will postpone the transmission and queue the packet.  If a sender fails to transmit a packet for long waiting time it calculates the CW value for the next cycle as- CW now = CW prev /2 i Where i is the number of missing transmission within receiver’s RxOP limit and CW now >=Cw min  Every node contains a counter (RxOP counter) which decrements its value by one after every slot based on the default RxOP value. Every RxOP has its corresponding id.  As we are considering periodic application, a number of reception opportunities form a cycle in which every RxOP has differences in sender’s id.  The cycle is determined by the maximum data generation interval among the source nodes.  It takes n number of RxOP cycles to accurately measure the number of the senders in each opportunity if any misses for wireless error or large medium access delay.

Design of DPW-MAC  For ith RxOP if receiver receives any packet during the n number of cycles it determines the starting time for that RxOP as its wake up time.  After n RxOP cycles each receiving node will determine its energy conserving wake up time as follows: o = - o If < = RxOP then the node continues listening and receive data for jth RxOP and determine its wake up time at (j+n)th RxOP which has the data. o If >=, then will be selected as the next wake up time. o Else, after the ith RxOP limit and performing the send operation the node will sleep for min sleep interval and then wakes up at the next closest period when RxOP limit counter value is reinitialized. o After receiving the beacon the downstream node can determine its next wake up time as – Set = start time of jth RxOP.  The receiver will notify the upstream nodes regarding the number of active senders in the particular RxOP through the beacon packet. Then, an upstream node i ca lculates its TxOP as-

Simulation  Simulation Environment Simulation tool: ns sensors are randomly deployed in 100x100 m ­ 2 sensor field The transmission range of the sensors is 30 m. Figure: Data Generation Interval vs Delay

Simulation Figure: Data Generation Interval vs Energy

Conclusion  In this paper, we have presented a delay and energy efficient MAC for wireless sensor network for periodic applications.  The data prediction based wake-up approach shows optimal delay gain and also energy efficiency in different traffic load.

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