Green Wireless Networking Using Concurrent Cooperative Transmissions and Energy Scavenging Smart Antenna Research Laboratory Aravind Kailas (aravindk@ieee.org) School of Electrical and Computer Engineering Some Applications of Cooperative Networking Structural Health Monitoring Problem Statement: Solve energy problem in wireless networks Preserve cycle-life of the rechargeable batteries Extending base station coverage MAC-free aerial data gathering Concurrent Cooperative Transmissions Fraction of energy saved (FES) in a single broadcast Factors of life extension (FLE) during multiple broadcasts Each cycle is an OLA with transmission threshold (OLA-T) broadcast OLA1 2.78 Strip Strip-shaped networks 0.64 Minimum Node Degree Diversity and array gain No contention Node mobility Disc FES 1.47 FLE Disc-shaped networks 0.32 1 10 100 1 10 100 Node Degree # Alternating Sets Alternating OLA with transmission threshold (A-OLA-T) with 2 alternating sets Y. W. Hong and A. Scaglione, “Energy-Efficient Broadcasting with Cooperative Transmissions in Wireless Sensor Networks,” IEEE Trans. Wireless Commun., vol. 5, no. 10, pp. 2844-55, Oct. 2006. Energy Scavenging Using a Hybrid Energy Storage System First-order approximation of SC energy mechanisms S1 S2 A A Energy cost of 3562 or N bits Orange area represents the radiated energy (100nJ/bit) Load Supercapacitor (SC) Energy Harvesting Unit Solar C R Ih R C 570mW Dark blue area represents the circuit energy (300nJ/bit) Energy pulse from car Harvester Rechargeable Battery SC 1 residual energy B B 1.425mJ Leakage ignored here; how many bits can be transmitted if leakage is included? Harvesting-aware algorithm using HESS extends battery life by 400% Cooperative transmissions and energy harvesting SC + - VH(t) RL S1(t)=1 RSC Rleak C S1(t)=0 S2(t)=1 S2(t)=0 S3(t)=1 S3(t)=0 570mW Energy pulse from car Main idea: combine SC energy on multiple nodes, if necessary, to make a cost-free transmission SC 2 residual energy Load leakage 1.425mJ SC Energy SC Energy SC Energy Not enough on one node 2.5 3.5 Harvester Rechargeable Battery Clearly, with regards to SC2 energy, you “use it or lose it”. CT would enable the data rate to be increased due to array and diversity gain User cooperation1 for nodes with only SCs increases throughput by a factor of ~7 relative to non-cooperative schemes J. W. Jung and M. A. Ingram, “Residual-energy-activated cooperative transmission (REACT) to avoid the energy hole,” IEEE International Conference on Communications (ICC) Workshop on Cooperative and Cognitive Mobile Networks (CoCoNet3), June 2010, accepted.