Authors: Judy Chu Dr. Jinhong Yuan UNSW

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Performance Analysis and code design for
distributed space-time trellis codes
Authors Judy Chu Dr. Jinhong Yuan (UNSW)
Dr. Yonghui Li (USYD)
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Performance Analysis and code design for
distributed space-time trellis codes

• Introduction
• System Model
• Performance Analysis
• Slow Fading Channels
• Quasi-slow Fading Channels
• Code Design and Simulation Results
• Conclusions

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Performance Analysis and code design for
distributed space-time trellis codes
Introduction

• Not practical to equip small communication
  device with multiple antennas
• Two or more nodes cooperate with each other, by
  sharing with each others antenna
• To provide cooperative diversity gain
• To provide higher data rate, or power saving

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Performance Analysis and code design for
distributed space-time trellis codes
System Model
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Performance Analysis and code design for
distributed space-time trellis codes
Basic Operation

• Single antenna at each node
• Cooperation is based on time-division system
• During 1st half of frame, source broadcasts
  encoded signal
• During 2nd half of frame, source transmits
  another encoded signal to destination Relay
  detects the signal from source, then transmits to
  the destination for the source
• Destination makes decision based on the signals
  received from both source and relay

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Performance Analysis and code design for
distributed space-time trellis codes
Some notations
Frame length
Time slots
Distributed Space-time codeword
Channel fading coefficients
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Performance Analysis and code design for
distributed space-time trellis codes
Receiver
Receive signal vector
Decision Metric
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Performance Analysis and code design for
distributed space-time trellis codes
Modified System Model
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Performance Analysis and code design for
distributed space-time trellis codes
Equivalent Link Model

• Performance of Source-Relay-Destination Link

• SNR of this equivalent link

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Performance Analysis and code design for
distributed space-time trellis codes
Modified Decision Metric
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Performance Analysis and code design for
distributed space-time trellis codes
Performance Analysis
Conditional PEP
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Performance Analysis and code design for
distributed space-time trellis codes
Performance Analysis --- Slow fading channel
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Performance Analysis and code design for
distributed space-time trellis codes
Code Design Criteria

• Maximize the transmit diversity advantage over
  all pairs of distinct codewords

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Performance Analysis and code design for
distributed space-time trellis codes
Simulation Result
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Performance Analysis and code design for
distributed space-time trellis codes
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Performance Analysis and code design for
distributed space-time trellis codes
Performance Analysis Quasi-Slow Fading Channel

• Channel coefficients remains the same over the
  entire first or second half of the frame, but
  change from the first L time slots to the second
  L time slots of one frame

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Performance Analysis and code design for
distributed space-time trellis codes
Code Design Criteria
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Performance Analysis and code design for
distributed space-time trellis codes
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Performance Analysis and code design for
distributed space-time trellis codes
Simulation Result
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Performance Analysis and code design for
distributed space-time trellis codes
Conclusion

• By adopting the equivalent two-hop link, we take
  into account the detection errors at relay, which
  is more practical
• Average PEPs are derived for the single relay
  system on slow and quasi-slow fading channels
• Space-time trellis codes are generated
  accordingly

Challenges

• How to design the distributed space-time trellis
  code if the relay decodes the received signal?
• Multiple antennas at source and relay?

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Performance Analysis and code design for
distributed space-time trellis codes
Thank you !