Effective Training Sequence for 802.11n

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Effective Training Sequence for 802.11n

• David Tung
• Ralink Technology
• dtung_at_ralinktech.com

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Trade-offs of Training Sequence

• Backward compatibility
• Backward compatible with 802.11a is required by
  Functional Requirement. (IEEE 802.11-03-813r9)
• A lesson from 802.11g.
• Effectiveness
• Low overhead for the same functional
  requirements.
• Performance
• AGC, frequency offset est., symbol alignment,
  channel est.
• When it comes to MIMO, we are talking about few
  tens dB improvement.

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Objective of this Presentation

• Present an effective training sequence that
  wouldnt scarify other criteria.

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The Proposed Training Sequence
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The Proposed Training Sequence (cont.)

• SPa, LPa and SIGa are 802.11a training sequence.
  (802.11a backward compatible)
• SPn1, SPn2, SPn3
• Polarity inversion of some SPa tones.
• The same auto-correlation sequences as SPa.
• Low cross-correlations between SPn1, SPn2, SPn3
  and SPa. (good for MIMO AGC, IEEE 802.11-04-02r1
  )
• SIGn is a TBD signal field for 802.11n.
• Save up to 16ms. (IEEE 802.11-04-46r1.)

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The Short Preamble Sequences

• Codeword representation 0 means the same
  polarity, 1 means the opposite polarity.
• Power of one sequence divided by maximum power of
  (circular) cross-correlation is 8.57dB.
• PAPR are 3.36dB, 6.02dB, 5.51dB and 6.48dB for
  SPa, SPn1, SPn2 and SPn3 respectively.

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The Short Preamble Sequences(cont.)
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The Short Preamble Sequences(cont.)
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Conclusion

• We present an effective training sequence that
  supports 802.11a backward compatibility and
  achieves better performance for MIMO AGC training.