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Beamforming in Wireless Sensor Networks

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... Symposium on Information Theory (ISIT 2005), Adelaide, Australia, September 2005. ... Basic idea: use a cluster of nodes to emulate elements of a phased array ... – PowerPoint PPT presentation

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Title: Beamforming in Wireless Sensor Networks


1
Beamforming in Wireless Sensor Networks
  • Omar Bakr
  • ombakr_at_cs.berkeley.edu

R. Mudumbai, J. Hespanha, U. Madhow, Scalable
Feedback Control for Distributed Beamforming in
Sensor Networks, Proc. 2005 IEEE International
Symposium on Information Theory (ISIT 2005),
Adelaide, Australia, September 2005.
2
Advantages of Beamforming
  • More coverage for less power
  • Less interference gt improved capacity
  • Basic idea use a cluster of nodes to emulate
    elements of a phased array
  • Challenges relative locations of the different
    nodes are unknown and clocks are not synchronized
  • Beamforming has to be done in a distributed and
    scalable fashion

3
Beamforming Scenario
Sender
Beamformers
Receiver
4
Randomized Beamforming Algorithm
  • Each node needs to apply the proper phase shift
    to the signal in order to maximize the signal in
    strength in a particular direction
  • How to choose the right phase delay? Use feedback
  • Each node independently adjusts its phase delay
    by ? or -? with equal probability at each time
    slot
  • If an SNR improvement is detected, then the new
    delays are used otherwise revert to the previous
    delays

5
Performance Evaluation (100 nodes)
6
Weaknesses of this approach
  • Works well only when the channel is time
    invariant
  • May not converge if the channel varies at high
    rates
  • Requires a noiseless feedback channel
  • Not clear what beam pattern gets produced with
    the random weight assignment
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