1. Investigating the Energy Consumption of a Wireless Network Interface in an Ad Hoc Networking Environment Authors: Laura Marie Feeney, Martin Nilsson Swedish Institute of Computer Science Presented By: Seapahn Meguerdichian

2. Problem Statement Network interface has non-trivial energy consumption, especially as systems become more energy efficient. 1. Improve efficiency of physical device. 2. Reduce the amount of traffic? How to develop energy efficient protocols without a good understanding of the energy consumption associated with network traffic?

3. Data Sheets, OEM Specs … Not so helpful. Lucent IEEE 802.11 DSSS PC Card Characteristics SpecsMeasured 2 Mbps (Bronze) Sleep Mode Idle Mode Receive Mode Transmit Mode 9 mA -------- 280 mA 330 mA 14 mA 178 mA 200 mA 280 mA 11 Mbps (Silver) Sleep Mode Idle Mode Receive Mode Transmit Mode 10 mA -------- 180 mA 280 mA 10 mA 156 mA 190 mA 284 mA

4. Approach Make measurements and report helpful results. Packet oriented Network oriented Use numeric results as input to network simulations. Precise values are less important than developing insights that are useful for protocol development.

5. Type of Network In structured networks, base stations usually have no special energy constraints. In ad-hoc networks this is not the case In IEEE 802.11: Several data transmit rates. Modes: BSS mode: base station service set Ad hoc mode: wireless link Note: CSMA/CA protocol with optional RTS/CTS negotiation.

6. Investigation Directly measure energy consumed by a packet: send vs. receive vs. discard promiscuous mode operation broadcast vs. point-to-point traffic fixed vs. incremental transmit rate Energy consumption is sometimes treated as synonymous with bandwidth utilization. Energy is sometimes treated as an abstract “commodity”.

9. Linear Model Fixed component: channel acquisition Incremental component: packet size Energy = m * size + b Linear regression is used to test the model and find values for m and b. Model ignores backoff and retransmissions, which are best analyzed in the context of a traffic and mobility model.

15. Routing protocol evaluation Use the linear equations in conjunction with CMU Monarch ns-2 simulation environment. Repeat “classic” CMU performance evaluation. 50 nodes, 1500 X 300 m random waypoint mobility, 20 m/s (uniform) IEEE 802.11 with RTS/CTS, 2 Mbps 20 CBR streams - 4 £ 64 byte packets/s Consider DSR, DSR-np and AODV routing protocols.

17. Simulation Results Cost of receiving is non-negligible. Broadcast traffic is expensive in a relatively dense network. Incremental costs are low, relative to per-packet costs. Discarding can be cheap Promiscuous mode can be expensive.

18. Conclusions Energy consumption is not synonymous with bandwidth utilization. Idle mode energy consumption is extremely high. RTS/CTS MAC protocol consumes significant energy. Collision avoidance requirements limit the applicability of power and topology control strategies. Violating abstraction barriers can lead to new insights