CSEUTA CSE 5346 THE ABC OF ABC

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CSE_at_UTACSE 5346
THE ABC OF ABC

• Ants for Load Balancing in Telecommunications
  Networks
• Abhishek A. Hemrajani

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Ants in Nature

• Individual ants are behaviorally very
  unsophisticated insects.
• Acting collectively , ants manage to perform a
  variety of complicated tasks, with great
  reliability and consistency.
• Tasks like regulating nest temperature within
  limits, forming bridges, sorting brood and food
  items, egg care, finding shortest routes from
  nest to food etc. can be performed by ants when
  acting collectively.

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Changing their environment

• The physical characteristics may be changed as a
  result of carrying out some actions such as
  digging a hole, depositing mud etc.
• The environment is changed by depositing
  something which makes no direct contribution to
  the task, but is used solely to influence
  subsequent behavior.

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Pheromones

• Ants drop pheromones as they walk by stopping and
  touching their gaster to the ground.
• Strength of the trail they lay is a function of
  the rate at which they make deposits and the
  amount per deposit
• Since pheromones evaporate, strength of trail is
  function of original strength and time.

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Strong pheromone trail symbolize shorter and
effective path

• Path Selection

• Blocking Problem
• Shortcut Problem

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ABC (Ant-Based Control) for Network Management

• Reasons for Congestion
• Total call volume at any time is unusually
  high.
• Some particular location is suddenly the origin
  or destination of an unusually large volume of
  calls.

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Load Balancing

• Construction of call - routing schemes which
  successfully distribute changing load over system
  and minimize lost calls.
• Centralized Control
• Decentralized Control

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Disadvantages of centralized control

• Communication and Processing Overheads.
• Scale Badly.
• Failure of Central control leads to failure of
  entire network.

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Pheromone Tables instead of Routing Tables.

• Every node has a pheromone table for every
  possible destination in network and each table
  has entry for every neighbor.
• Pheromone laying is presented by updating
  probabilities.
• Ants are launched with random destination and
  they move according to entries is pheromone
  tables.

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Updating Probabilities

• Increase probability
• (pold ?p)/(1 ?p)
• Decrease probability
• P pold /(1 ?p)

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General Framework for ABC system

• Ants are launched with random destination on
  every part of the system.
• Ants walk randomly according to the probabilities
  in pheromone tables for their particular
  destination.
• Ants update the probabilities in the pheromone
  tables for the parts of the system they were
  launched from. They increase this probability in
  favor of the part hey just came from.
• The increase of these probabilities is a
  decreasing function of the age of the ant and of
  the probability already there. ?p 0.08/age
  0.005.
• The ants get delayed on parts of the system that
  are congested.

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References

• 1) Ants for load balancing in telecommunications
  networks
• ---Ruud Schoonderwoerd, Owen Holland, Janet
  Bruten and Leon Rothkrantz.
• 2) Ant-Based Network Control System
• ---David Legge, Peter Baxendale.

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CSE_at_UTAThank You