Intelligent Antenna Sharing in Wireless Networks

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• Intelligent Antenna Sharing in Wireless Networks
• Aggelos Bletsas
• aggelos_at_media.mit.edu
• Viral Communications Group
• MIT Media Lab - Fall 2004

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• Wireless Broadcast (it makes it hard it makes
  it challenging)

Direct Multi-hop
Cooperative (100 years old) (35 years
old) (today)

• Wireless Broadcast Advantage

• Antenna Sharing exploits observation of a common
  property across different users (antennas) in
  space
• Property data, time, location
• Our contribution distributed and adaptive
  cooperative algorithms, applicable in practice

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• Closer is not always better Goud Jr et. al
  2004 fading is not always harmful (MIMO
  results)

• Instantaneous wireless channel conditions matter
  (not only average)

• Algorithms should adapt to wireless propagation
  instantaneously (within channel coherence time)
  - no need for topology estimation

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• Diversity (including repetition)wasteful, does
  not scale

• Cooperative diversitycomplex space-time
  codingreceiver hardware might be non linear
  (superposition does not apply)

• Opportunistic Relayingpick best relay
• (best relay best end-2-end path)no
  communication among relays needed(distributed,
  real time solution)

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Method of distributed timers opportunistic
relaying Mapping channel conditions to time!
Harmonic mean

• Exploiting RTS/CTS packets of MAC and
  reciprocitybest path relay that expires first

• Collision probability depends on ? (user
  defined)

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Outage vs SNR

• Performance increases with number of relays

• Need for less transmission power (less
  interference scalability)

SEP vs SNR
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Picking best relay leads to higher capacity
compared to picking a set of relays, for
fixed total transmission power!
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Implementation of opportunistic relaying using
low cost, embedded radios
Rx/display
Tx
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Antenna sharing for cooperative time keeping
End-2-End Error
Diameter of network

• Distributed Synchronization server free,
  scalable

• Scalable larger network, better performance

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Antenna sharing for cooperative position
estimation

• Estimate your location relatively to neighbors
  with good signal paths (high SNR measurements).

• Prior art found in protein structure
  determination(molecular distance geometry
  problem)

• More on this in separate lecture

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Intelligent Antenna Sharing in Wireless Networks

• Practical, Adaptive to the environment
  Algorithms.
• Distributed Algorithms. No need for network
  topology knowledge.
• Algorithm could be implemented to non-linear
  receivers.
• See Around Corners ability
• Antenna Sharing is extended to efficient network
  timing/positioning.