-1/16- Maximum Battery Life Routing to Support Ubiquitous Mobile Computing in Wireless Ad Hoc Networks C.-K. Toh, Georgia Institute of Technology IEEE Communication Magazine June 2001 Presented by Dukhyun Chang

-2/16- Contents Introduction Characteristics of Ad Hoc Mobile Wireless Networks Desired Properties of Ad Hoc Routing Protocols Power-Efficient Ad Hoc Routing Performance Conclusion

-3/16- Introduction Ad hoc mobile network – An autonomous system consisting of mobile hosts – Infrastructureless networks – Most of the ad hoc mobile devices today operate on batteries – Forming topology depending on the node’s geographical positions Transceiver coverage patterns Transmission power levels Co-channel interference levels

-4/16- Characteristics of Ad Hoc Mobile Networks Main characteristics – Dynamic topology – Bandwidth constraints and variable link capacity – Energy constrained nodes – Multi-hop communications – Limited security

-5/16- Characteristics of Ad Hoc Mobile Networks Functions of ad hoc routing protocols – Determination of network topology Node level connectivity –Surrounding environment, neighboring nodes Network level connectivity –Flat-routed network architecture –Hierarchical network architecture – Maintaining network connectivity Need a fully distributed algorithm – Transmission scheduling and channel assignment Consider interference problems – Packet routing Table-driven, On-demand, Hybrid

-6/16- Desired Properties of Ad Hoc Routing Protocols Distributed implementation, efficient utilization of bandwidth and battery capacity, fast rout convergence, etc. Efficient utilization of battery capacity is most important Conventional metrics – Maximum end-to-end throughput – Minimum end-to-end delay – Shortest path/minimum hop Metrics for ad hoc networks – Minimum total power – Load balancing – Minimum overhead – Adaptability to the changing topology – Association stability – Route relaying nodes

-7/16- Power-Efficient Ad Hoc Routing Power consumption models – Communication-related power Processing power Transceiver power – Non-communication-related power Minimizing total power is a important purpose – Minimum total transmission power routing (MTPR) – Minimum Battery Cost Routing (MBCR) – Min-Max Battery Cost Routing (MMBCR) – Conditional Max-Min Battery Capacity Routing (CMMBCR)

-8/16- Minimum Total Transmission Power Routing (MTPR) MTPR P(n i,n j ) : transmission power between host n j and n i N 0 : source N D : destination A : all possible routes Doesn’t give the minimum number of hops The algorithm for selecting fewer hop routes P transceiver : the power used when receiving data

-9/16- Minimum Battery Cost Routing (MBCR) C i t : battery capacity of a host n i at time t The remaining battery capacity of each host is a more accurate metric to describe the life time of each host To find the maximum remaining battery capacity, we select route I that has the minimum battery cost. If all nodes have similar battery capacity, this metric will select a shorter- hop route

-10/16- Minimum Battery Cost Routing (MBCR) Only consider the summation of values of battery cost; therefore can overuse any single node

-11/16- Min-Max Battery Cost Routing (MMBCR) The power of each host is being used more fairly in this scheme than previous schemes. No guarantee of minimum total transmission power path under all circumstances Consume more power to transmit ; reduce the lifetime of all nodes

-12/16- Conditional Max-Min Battery Capacity Routing (CMMBCR) Γ : threshold Using previous scheme, maximize the life time of each node and use the battery fairly can’t be achieve simultaneously Use battery capacity instead of cost function Choose route with minimum total transmission power among routes that have nodes with sufficient remaining battery capacity

-13/16- Performance Confined space of 100m x 100m Each mobile host has a wireless cell size of 25 m radius At the start of each simulation time slot, each node chooses randomly a new direction and moves a distance equal to the product of its speed and the length of a time slot It move at a speed of 2 m/s

-14/16- Performance

-15/16- Performance Average host lifetime vs. increasing g standard deviation of lifetime of all nodes vs. g.

-16/16- Conclusion Battery power capacity, transmission power consumption, stability of routes, and so on should be considered The two goals: to use each node fairly and extend their lifetimes are not compatible CMMBCR scheme chooses a shortest path if all nodes in all possible routes have sufficient battery capacity Can maximize the time when the first node powers down or the lifetime of most nodes in the networks