1	Energy Consumption in Ad-Hoc Routing Protocols: Comparing DSR, AODV, and Tora Yasser Gadallah and Thomas Kunz Carleton University http://kunz-pc.sce.carleton.ca/ tkunz@sce.carleton.ca
2	Motivation Mobile Devices constrained by many things, one of them being battery Sending and receiving messages is one of the more power-expensive operations Data packets Control packets of routing protocol Wireless Interfaces also consumer substantial amount of power while idle, but putting them into the low-power “sleep” mode has to be done carefully Goal: study power consumption of popular MANET routing protocols to understand their energy behaviour, and to draw lessons for the design of more efficient routing protocols
3	Energy Metrics What is an “energy-efficient” routing protocol? Possible Metrics: Minimize energy consumed/packet, Maximize time to network partition, Minimize variance in node energy levels, Minimize cost/packet, and Minimize maximum node cost. We used: average overall amount of consumed energy Note: if minimizing energy consumption was only goal, a trivial optimal solution exists: drop all packets J Therefore, need to also consider packet delivery ratio
4	Energy Model Assumption: only wireless interface consumes energy (i.e., internal processing of messages etc. is “free”) NS2 has (simplistic) energy model: “The energy model in a node has a initial value which is the level of energy the node has at the beginning of the simulation. This is known as initialEnergy. It also has a given energy usage for every packet it transmits and receives. These are called txPower and rxPower” Default IDLE energy consumption is zero, send/receive costs independent of packet size, unicast/broadcast, etc.
5	Energy Model Re-implement energy model to correspond to published measurements of actual IEEE 802.11 interface: Consumed energy per packet = m * (packet size) + b m and b are empirical constants that are based on whether the packet is being sent, received, promiscuously handled or discarded. They also depend on the operation type (unicast vs. broadcast). Idle power: 0.8 Watts
6	Routing Protocols and Simulation Environment Routing Protocols: AODV: on-demand protocol with traditional routing tables DSR: source routing, route caches, nodes (optionally) listen promiscuously to learn information to update cache TORA: link reversal algorithm, maintains enough info so that link failure not necessarily results in new route discovery, more complex control messages Simulation Environment: “the usual” NS2, 50 nodes, 1500 x 300 m, initial power: 1000 Joules CBR sources, 5 packets/s, 512 byte packets, 12 senders Random waypoint model, 20 m/s max speed, variable pause time 600 seconds simulation length, 4 different movement patterns per scenario
7	Analytical and Simulation Results Functional Comparison Results protocol analysis: predict that AODV and DSR should perform similarly, with TORA being worse Simulation Results: not quite that (at first sight)
8	Simulation Results (cont) Problem: TORA delivers far fewer packets (i.e., saves energy by not delivering them often enough at the destination!), based on the simulation conditions that we used
9	Simulation Results: Energy Balance
10	Simulation Results: Idle Energy Consumption Matters
11	Conclusions and Future Work Conclusions: AODV consumes slightly less energy than DSR at comparable packet delivery ratio DSR seems to have slightly more balanced energy consumption between nodes (based on the difference (max - min) of nodal energy consumption) Idle energy is about half of total energy consumed Future Work: Design protocol that is energy-efficient and fair (i.e., balanced) – work under way Compare to other published energy efficient routing protocols such as SPAN, etc.