Maximum Battery Life Routing to Support Ubiquitous Mobile Computing In Wireless Ad Hoc Networks

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Maximum Battery Life Routing to Support
Ubiquitous Mobile ComputingIn Wireless Ad Hoc
Networks

• C.-K. Toh
• IEEE Communication Magazine 01

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Introduction

• Three object of this paper
• Present the characteristic of an ad hoc wireless
  network
• Highlight the desirable properties of ad hoc
  routing protocol
• Examine, propose, and compare different
  power-efficient ad hoc routing schemes

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Characteristics of Ad Hoc Mobile Wireless Networks

• Main characteristics
• Dynamic topology
• Bandwidth constraints and variable link capacity
• Energy constrained node
• Multi-hop communications
• Limited security
• To support ad hoc mobile communication under the
  influence of the above factors
• Determining/detecting changing network topology
• Maintaining network topology/connectivity
• Scheduling of packet transmission and channel
  assignment
• Routing

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Determination of Network Topology

• Determining and monitoring the dynamics of
  network topology over time
• Strong connectivity is ensured
• Two approach in providing ad hoc network
  connectivity
• Flat-routed network architecture
• All nodes are equal
• Peer-to-peer
• Hierachical network architecture
• At least one node in each lower layer is
  designated to serve as a gateway or coordinator
  to higher layers

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Maintaining Network Topology/Connectivity

• Topology changes frequently due to
• Break down of a mobile host
• Failure of connected link
• Ad Hoc routing protocol must be dynamically
  update the status of link reconfigure itself
• Centralized
• Vulnerable
• Too much time and effort
• Distributed
• Reliable and robust operation

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Transmission Scheduling Channel Assignment

• New radio transmission
• Affect an existing communication link through
  signal interference
• Efficient packet scheduling channel assignment
  is needed
• Ensure efficient use of the limited available
  bandwidth

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Packet Routing

• High rate of topology changes
• Routing protocol should propagate topology
  changes
• Routing protocol compute new routes
• Existing routing protocol
• Table-driven
• On-demand
• Hybrid

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Desired Properties of Ad Hoc Routing Protocols
(Cont)

• Distributed Implementation
• Efficient utilization of bandwidth
• Reduction of control overhead
• Efficient utilization of battery capacity
• Decreasing of nodes degrade network performance
• Protocol should consider power consumption
• Optimization of metrics
• Different metric for different routing design
  goal
• Maximum end-to-end throughput
• Minimum end-to-end delay
• Shortest path/minimum hop
• Minimum total energy
• Load balancing
• Minimum overhead
• Adaptability to the changing topology
• Association stability
• Route relaying load

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Desired Properties of Ad Hoc Routing Protocols
(Cont)

• Fast route convergence
• Because of dynamic topology changes, routing
  protocol should provide a new and stable route as
  soon as possible
• Freedom from loops
• Looping of packets cause overhead of bandwidth
  and power consumption
• Unidirectional link support
• Presence of different radio capacities, and
  signal interference make unidirectional link

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Power-Efficient Ad Hoc Mobile Networks (Cont)

• Efficient utilization of battery power
• Power of mobile hosts consist of
• Communication related power
• Processing power
• Transceiver power
• Non-communication related power
• Each protocol layer are coupled
• Power conservation scheme for each layer
• Physical layer and wireless device
• DPM and DVS in the wireless device
• Adjust transmission power in physical layer
• Lower transmission power save power
• Higher transmission power prolong an existing
  link against interference

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Power-Efficient Ad Hoc Mobile Networks (Cont)

• Data link layer
• Effective retransmission scheme
• More error than wired network
• Retransmission increase power consumption and
  interference
• Sleep mode operation
• Overhearing
• Network layer
• To maximize the life time of mobile hosts
• Routing as a viewpoint of power constraints

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Minimum Total Transmission Power Routing (Cont)

• Minimum transmission power is dependent on
• Interference noise
• Distance between hosts
• Desired BER (bit error rate)
• Total transmission power for route l, Pl
• From above desired route k obtained from
• Solved by Dijkstra or Bellman-Ford algorithm
  Problems
• More nodes involves in routing
• Unstable routing path
• Increase end-to-end delay

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Minimum Total Transmission Power Routing

• To overcome problem, transceiver power were
  considered as a cost metric and distributed
  Bellman-Ford algorithm was used.
• At node ni
• Subsequently, Computes its power cost by using
  follow equation
• Helps find routes with fewer hops

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Minimum Battery Cost routing (Cont)

• Minimum Total Transmission Power Routing has a
  critical disadvantage
• A special node will be exhausted quickly, if a
  minimum total transmission power is obtained via
  that node in many routes.
• Remaining battery capacity of each host is a more
  accurate metric to maximize the life time of each
  host
• Possible battery cost function
• Route with the maximum remaining battery capacity
• Battery cost Rj for route I, consisting of D
  nodes

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Minimum Battery Cost Routing

• A route containing nodes with little remaining
  battery capacity may still be selected
• In the above example, the Route 1 will be
  selected

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Min-Max Battery Cost Routing

• To make sure no node will be used, battery cost
  Rj is redefined as
• Desired route i can be obtained following
  equation
• A closer examination
• No guarantee about minimum transmission power
• It can consume more power to transmit

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Conditional Max-Min Battery Capacity routing
(Cont)

• Maximize life time and use battery in fair manner
  simultaneously
• It is not possible previous routing protocols
• Basic idea
• all nodes in some possible route has
• Sufficient remaining battery capacity
• Route with minimum transmission power routing
• Low battery capacity
• Route including node with the lowest battery
  capacity should be avoided

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Conditional Max-Min Battery Capacity Routing

• Define
• Battery capacity for route j at time t
• A all possible routes at time t which
  satisfying
• Q all possible routes at time t
• Algorithms

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Performance of Different Routing Algorithms
considering Power Efficiency

• Structure of simulator
• Power consumption computation
• Communication-related
• P ? of traffic
• Non-communication-related
• P is fixed
• The ratio of above two

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Simulation Result

• Expiration time

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Simulation Result

• Expiration time according to ?

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Simulation Result

• Average battery life and standard deviation of
  the expiration time of all hosts

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Simulation Result

• Average route length

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Conclusion

• Minimum battery cost, min-max battery cost
• Prevent nodes from being unwisely overused
• Extend the time until the first node die
• Take longer hopes, reduces the life time of most
  nodes
• Conditional min-max battery cost
• At enough power
• Choose shortest path
• At below defined power
• Routes going through these nodes will be avoided
• By adjusting ?
• Maximize the time when the first node down
• Maximize the life time of most nodes