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Ph.D. Thesis Defense June 2005 - MIT Media Lab · PDF fileIntelligent Antenna Sharing in Cooperative Diversity Wireless Networks Ph.D. Thesis Defense June 2005 Aggelos Bletsas...

Feb 06, 2018

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  • Intelligent Antenna Sharing in Cooperative Diversity WirelessNetworks

    Ph.D. Thesis DefenseJune 2005

    Aggelos Bletsas

    [email protected]

    Viral Communications Group, MIT Media Laboratory

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 1/50

  • Thesis Committee

    Andy Lippman,Principal Research Scientist, MIT Media Lab.

    Joe Paradiso,Associate Professor, MIT Media Lab.

    Moe Win,Associate Professor, MIT LIDS.

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 2/50

  • Motivation and Inspirations

    You are (probably) here because you have all experienced:

    bad reception...

    battery problems...

    no connectivity during large gatherings (4th of July problem!)...

    Could we fix all the above problems?

    Inspirations:

    Gupta and Kumar IT 2000 result: local communication helps...

    Multiple Antennas at each radio help...

    Could we merge the two above? More users ?= better wireless communication?

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 3/50

  • Motivation and Inspirations

    You are (probably) here because you have all experienced:

    bad reception...

    battery problems...

    no connectivity during large gatherings (4th of July problem!)...

    Could we fix all the above problems?

    Inspirations:

    Gupta and Kumar IT 2000 result: local communication helps...

    Multiple Antennas at each radio help...

    Could we merge the two above? More users ?= better wireless communication?

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 3/50

  • Motivation and Inspirations

    You are (probably) here because you have all experienced:

    bad reception...

    battery problems...

    no connectivity during large gatherings (4th of July problem!)...

    Could we fix all the above problems?

    Inspirations:

    Gupta and Kumar IT 2000 result: local communication helps...

    Multiple Antennas at each radio help...

    Could we merge the two above? More users ?= better wireless communication?

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 3/50

  • Additional Problem Constraint: Low Complexity and Implementation

    SourceRelay

    Relay

    Destination

    In general, multi-antenna systems increase:

    reliability (diversity gain).

    spectral efficiency bps/Hz (multiplexing gain)

    Explore multiple antennas in the Relay channel, via cooperative relays.

    IMPLEMENTATION TODAY, with existing RF-front ends.

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 4/50

  • Additional Problem Constraint: Low Complexity and Implementation

    SourceRelay

    Relay

    Destination

    In general, multi-antenna systems increase:

    reliability (diversity gain).

    spectral efficiency bps/Hz (multiplexing gain)

    Explore multiple antennas in the Relay channel, via cooperative relays.

    IMPLEMENTATION TODAY, with existing RF-front ends.

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 4/50

  • Main Difficulties

    best path @ kT

    best path @ (k+1)T

    Direct Relayed

    |as,i|2 |ai,d|2

    Source Destination

    |as,j|2 |aj,d|2

    Information is not a priori known at the relays.

    Number of participating antennas is unknown.

    Number of useful participating antennas is unknown.

    Coordination and Group formation ought to be distributed, not "genie-aided".

    MIMO ST-coding 6= coding for the Relay channel.

    Radio transceiver complexity.

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 5/50

  • Main Difficulties

    best path @ kT

    best path @ (k+1)T

    Direct Relayed

    |as,i|2 |ai,d|2

    Source Destination

    |as,j|2 |aj,d|2

    Information is not a priori known at the relays.

    Number of participating antennas is unknown.

    Number of useful participating antennas is unknown.

    Coordination and Group formation ought to be distributed, not "genie-aided".

    MIMO ST-coding 6= coding for the Relay channel.

    Radio transceiver complexity.

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 5/50

  • Main Difficulties

    best path @ kT

    best path @ (k+1)T

    Direct Relayed

    |as,i|2 |ai,d|2

    Source Destination

    |as,j|2 |aj,d|2

    Information is not a priori known at the relays.

    Number of participating antennas is unknown.

    Number of useful participating antennas is unknown.

    Coordination and Group formation ought to be distributed, not "genie-aided".

    MIMO ST-coding 6= coding for the Relay channel.

    Radio transceiver complexity.

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 5/50

  • Main Difficulties

    best path @ kT

    best path @ (k+1)T

    Direct Relayed

    |as,i|2 |ai,d|2

    Source Destination

    |as,j|2 |aj,d|2

    Information is not a priori known at the relays.

    Number of participating antennas is unknown.

    Number of useful participating antennas is unknown.

    Coordination and Group formation ought to be distributed, not "genie-aided".

    MIMO ST-coding 6= coding for the Relay channel.

    Radio transceiver complexity.

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 5/50

  • Main Difficulties

    best path @ kT

    best path @ (k+1)T

    Direct Relayed

    |as,i|2 |ai,d|2

    Source Destination

    |as,j|2 |aj,d|2

    Information is not a priori known at the relays.

    Number of participating antennas is unknown.

    Number of useful participating antennas is unknown.

    Coordination and Group formation ought to be distributed, not "genie-aided".

    MIMO ST-coding 6= coding for the Relay channel.

    Radio transceiver complexity.

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 5/50

  • Main Difficulties

    best path @ kT

    best path @ (k+1)T

    Direct Relayed

    |as,i|2 |ai,d|2

    Source Destination

    |as,j|2 |aj,d|2

    Information is not a priori known at the relays.

    Number of participating antennas is unknown.

    Number of useful participating antennas is unknown.

    Coordination and Group formation ought to be distributed, not "genie-aided".

    MIMO ST-coding 6= coding for the Relay channel.

    Radio transceiver complexity.

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 5/50

  • Outline

    Assumptions and Background

    Approach

    Performance

    Implementation Example

    Relevant Technologies

    Conclusion

    Acknowledgements

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 6/50

  • Assumptions and System Model

    Inline with prior art in the field:

    Half-duplex radios.

    Simple RF-front ends:

    Half-duplex radios.

    No rate adaptation (no CSI at the source).

    No phased arrays (No beamforming).

    yd = asd xs + nd.

    Neighboring interfering streams: noise.

    (Mostly) Rayleigh fading. E[|asd|2] = 1/dv

    Slow Fading (most difficult communication problem).

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 7/50

  • Assumptions and System Model

    Inline with prior art in the field:

    Half-duplex radios.

    Simple RF-front ends:

    Half-duplex radios.

    No rate adaptation (no CSI at the source).

    No phased arrays (No beamforming).

    yd = asd xs + nd.

    Neighboring interfering streams: noise.

    (Mostly) Rayleigh fading. E[|asd|2] = 1/dv

    Slow Fading (most difficult communication problem).

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 7/50

  • Approaches

    Non-cooperative communication.

    Cooperative Repetition.

    Simultaneous transmissions(Space-Time Coding).

    Our Approach.

    Proactive single relay selection.

    Instantaneous channel conditions(instead of average).

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 8/50

  • Approaches

    Non-cooperative communication.

    Cooperative Repetition.

    Simultaneous transmissions(Space-Time Coding).

    Our Approach.

    Proactive single relay selection.

    Instantaneous channel conditions(instead of average).

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 8/50

  • Approaches

    Non-cooperative communication.

    Cooperative Repetition.

    Simultaneous transmissions(Space-Time Coding).

    Our Approach.

    Proactive single relay selection.

    Instantaneous channel conditions(instead of average).

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 8/50

  • Approaches

    Non-cooperative communication.

    Cooperative Repetition.

    Simultaneous transmissions(Space-Time Coding).

    Our Approach.

    Proactive single relay selection.

    Instantaneous channel conditions(instead of average).

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 8/50

  • Outline

    Assumptions and Background

    Approach

    Performance

    Implementation Example

    Relevant Technologies

    Conclusion

    Acknowledgements

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 9/50

  • Wireless Channel Observations

    v = 3.98

    Distance d

    Receiver cares about signal strength (not distance).

    Selection based on distance or average SNR... is suboptimal.

    Instantaneous channel conditions matter!

    [email protected], Ph.D. Thesis Defense, MIT June 2005. p. 10/50

  • Wireless Channel Observations

    v = 3.98

    Distance d

    Receiver cares about signal strength (not distance).

    Selection based on distance or average SNR... is suboptimal.

    I

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