Juan Francisco Redondo

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Ad hoc networks design and performance issues
Juan Francisco Redondo Antón
Masters Thesis HUT, Networking Laboratory
Supervisor Professor Jorma Virtamo
Espoo, May the 28th 2002
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Contents

1. Ad hoc networks features and applications
2. Capacity bounds and parameters involved
3. Medium Access Control
4. Routing
5. Simulations
6. Power control management
7. Quality of Service
8. Conclusions / Future work

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AHNs features and applications
Why Ad Hoc Networks (AHNs) ?
What are they useful for ?

• Conferences and meetings
• Home environment communications
• Emergency search and rescue
• Battlefield
• Sensors networks with different purposes
• (militar, environmental, traffic
• sensor networks)

• Fast installation
• Dynamic topology
• Flexibility
• Connectivity
• Mobility
• Cost
• Spectrum reuse possibility

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Capacity of AHNs
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Capacity of AHNs
Bounds on Capacity of Ad Hoc Networks

• Capacity of wireless networks
• 2 models of interference
• 2 hypotheses for the network random and
  arbitrary networks

• Physical model
• Protocol model

Random network
Arbitrary network
Reasons??
Protocol model of interference

• An experimental scaling law for ad hoc networks

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Capacity of AHNs
Parameters affecting capacity in AHNs Traffic
Pattern

• MAC protocols
• Locality of traffic pattern
• 52 uses a power law distribution of the
  distances to the destinations to show that
• - Random traffic pattern is the worst possible
• - if ? lt -2, Cn remains aprox. constant if large
  enough networks
• Effects of relaying m pure relaying nodes
  increase capacity like
• Multipacket reception (MPR)
• - 60 indicates that the use of MPR improves
  the coefficient of the asymptotic scaling law of
  AHNs.
• - The contribution of MPR is better with high
  connectivity
• - Multipacket transmission (MPT) can also be
  used
• - Some MAC protocols uses MPR RCT, MQSR

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Capacity of AHNs
Parameters affecting capacity in AHNs Location
and mobility
Grossglauser and Tse work 58 uses mobility to
offer multiuser diversity for the relaying of
packets in AHNs

• It is an attempt to facilitate local
  transmissions
• with high probability
• Independent movements can attain average
• long-term constant source-destination throughput
• - Only useful for asynchronous applications

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Capacity of AHNs
Parameters affecting capacity in AHNs Range of
transmission

• Need of a common range due to the
• necessity of bidirectional links for ACKs
• and handshake.
• Connectivity and throughput tradeoffs
• - Value of the area and the spatial reuse
• - Maximum number of simultaneous
  transmission-receptions

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Capacity of AHNs
Parameters affecting capacity in AHNs Range of
transmission

• Theoretical critical power
• Practical implementations
• COMPOW a modular solution
• An algorithm based on graph
• calculation

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MAC in AHNs
The Medium Access Control Layer in Ad Hoc Networks

• Constraints of wireless medium
• Transmission technologies infrared, microwave,
  spread spectrum
• Properties of MAC protocols for AHNs
• Proposals
• General for Wireless Networks
• IEEE 802.11
• HiperLAN
• Bluetooth
• Specific for Ad Hoc Networks
• CSMA
• MACA
• SEEDEX

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Routing in AHNs

• Expected properties
• Decentralized execution
• Loop free
• Adaptable to topology changes
• Flexible with traffic patterns
• Scalable
• Bandwidth efficient
• Power conservative
• Network security
• Quality of service support

• Metrics
• End-to-end data throughput
• Delay
• Route acquisition time
• Percentage out-of-order delivery
• Efficiency
• Other metrics

• On-demand vs. Table-driven
• AODV / DSR DSDV
• Hybrid schemes as ZRP seems to be the solution
  for scalability
• Protocols designed for high mobility DREAM,
  LAR, B-Protocol

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Simulations of connectivity
Connectivity and range of transmission

• Our goal is estimating the probability of having
  a fully connected network
• as a function of the transmission range

Probability of fully connected network
Range of transmission
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Power control in AHNs
A power-conservative design affects every network
layer

• PHY Quality of reception
• Design of HW in wireless
  interfaces
• Logical Link Control (LLC) accommodating
  error control schemes to
• Application Layer SW implementation

• Traffic requirements
• Channel conditions

• MAC
• IEEE 802.11 allows nodes to sleep temporally
  through synchronization processes
• DBTMA-Enhanced uses a busy tones channel to
  manage power control
• PCMA extents the handshake procedure to
  incorporate power-control information
• PAMAS avoids overhearing of the channel to save
  power

• Power-aware routing
• Energy as a metric is the crux of the matter
• Solutions
• GAF uses geographic information to make the
  nodes coordinate themselves
• to sleep in turns depending on
  design parameters
• SPAN creates a backbone of nodes that
  guarantees routing operation while other nodes
  sleep
• LEAR looks for balanced energy consumption
  among nodes

• Energy/packet
• Cost/packet
• Time to network partition

• Variance in node power levels
• Cost/node

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Quality of Service in AHNs
An ad hoc oriented view of QoS includes

• QoS models defines which are the goals
• IntServ / RSVP
• DiffServ
• FQMM, a QoS model for AHNs
• QoS signaling reserves resources
• dRSVP adaptive adjustment of the QoS level
• INSIGNIA in-band signaling for AHNs
• QoS routing finds the QoS routes
• CEDAR
• Ticket-based routing
• QoS Medium Access Control must
• to complete this framework

• Support reliable unicast communication
• Provide resource reservation

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Conclusions / Future work

• AHNs are the suitable solution for certain
  contexts
• Capacity is the restraining factor, especially
  with high number of nodes
• Separate analysis of factors impacting capacity
  provides ideas to increase it
• The range of transmission is a critical
  parameter and has multi-layer influence
• MAC problem is open
• Classic routing protocols are mature
• Power control is essential
• QoS is an awkward challenge

• Integration of network layers

Other questions

• Security
• Addressing
• Commercially available?
• Sharing resources