A NetworkAware MAC and Routing Protocol for Effective Load Balancing in Ad Hoc Wireless Networks wit

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A Network-Aware MAC and Routing Protocol for
Effective Load Balancing in Ad Hoc Wireless
Networks with Directional AntennaSiuli Roy,
Dola Saha, Somprakash Bandyopadhyay, Tetsuro
Ueda, Shinsuke Tanaka, MobiHoc 2003

• Anand Mohanrangan
• EE 360 Presentation
• May 12th, 2004

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Background

• Routing in Ad Hoc Networks is a well studied
  problem
• Most routing protocols designed independent of
  the physical layer (assume omnidirectional
  antennas)
• Considerable research into Energy saving protocols

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Directional Antennas

• Make use of directional antennas to reduce
  interference and increase capacity
• Mostly done at the MAC layer, not as many
  directional routing protocols proposed
• This paper represents some of the work done in
  this field

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Issues to consider in Ad Hoc Routing

• Some of the issues include -
• Power Consumed
• Control overhead
• End-to-end delay
• Route stability (and concurrently, frequency of
  route update under mobility and node failure)
• Scalability
• Load Balancing

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Zone-disjoint Transmission

• Route Coupling 2 routes are close enough to
  interfere with each other
• Route Coupling occurs if routes S1, N1, N2, D1
  and S2, N3, N4, D2 are taken
• Routes are node disjoint
• Zone disjoint achieve load balancing and
  reduces congestion/end-to-end delay

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System Description

• Electronically Steerable Passive Array Radiator
  (ESPAR) antenna
• RF Beamforming with 1 center element surrounded
  by 4-6 parasitic elements in a circle
• Random way-point mobility model in 2-d space
• 45 degree antenna beamwidth

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Network Awareness

• Neighborhood Link-State Table (NLSTn)
• Contains info. on neighbors and their direction
• Neighborhood Active Node List (NANLn)
• Communication activity status of neighbors
• Active Node List (ANLn)
• Perception of node n about communications
  activities in the entire network
• Global Link-State Table (GLSTn)
• Contains network topology information as
  perceived by node n at that instant of time

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Formation of ANL/GLST

• Both contain Recency Term - Ri
• Broadcast periodically to all nodes in network
• Periodicity determines control overhead
• Accuracy vs congestion
• Fisheye approach

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MAC Protocol ( Location Tracking)

• Receiver-oriented, Rotational Sector Based
  Directional MAC (using RTS/CTS with Directional
  NAV)
• If signal sensed above threshold ? perform 360o
  sweep to obtain location information
• To enable sweep, each control packet transmitted
  with preceding tone (200us)
• Omnidirectional RTS/CTS for benefit of
  neighboring nodes ANL/GLST

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Routing Protocol Table Driven

• Used to achieve Load balancing through Maximally
  Zone Disjoint Shortest Path
• Use ANL to find route with lowest route
  correlation factor, ?
• ?ni(P) (?n?P ( ActGni a(ni ? nj) (t) ) is a
  measure of the route coupling
• where ACTna (t) Gna(t) n ANL(t) are the Active
  Directional Neighbors of node n at transmission
  zonen (a)

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Example

• Initial Route ?
• S-X-Y-Z-D
• Route not viable due to mobility in D, route
  updated by Y
• If next-hop not reachable by same antenna
  pattern, then perform route discovery as
  previously described

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Performance Evaluation - Overhead

• For TGLST 5 sec, TANL 1 sec, medium occupied
  only 1.18 of time
• Simulation done with 30 static nodes and static
  routes

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Performance Comparisons with DSRStatic nodes
(CBR traffic, 1024 B packets)

• 5 times higher throughput
• 3.5 times less end-to-end delay
• Far fewer packet drops
• (data obtained from 20 static snap-shots)

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Performance Degradation due to MobilityLow-mobili
ty (5m/sec, 200 packets/sec)

• Higher frequency of control packets leading to
  more overhead
• Slight degradation due excess control traffic

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Performance of DSR with Directional Antenna (and
directional MAC) not in paper

• DSR
• Heavy Load
• Medium Load
• Light Load
• DSR w/ Directional Antenna etc
• Heavy Load
• Medium Load
• Light Load

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Conclusions - Advantages

• Performance gains obtained using directional
  antennas with suitable MAC (and routing)
  protocols
• Energy conservation due to beamforming
• Load balancing reduces drain on nodes on
  popular routes
• Can reduce hop count by trading energy
  conservation for greater distance

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Conclusions - Disadvantages

• Extra processing / System complexity
• In high-mobility environment, control overhead to
  maintain routing tables can be very expensive
• Harder to scale to 3-d terrain model
• Need to incorporate sleep times