1. Green Wireless Networking Using Concurrent Cooperative Transmissions and Energy Scavenging
Smart Antenna
Research Laboratory
Aravind Kailas
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
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 , Oct
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.