1. Effective Training Sequence for 802.11n
David Tung
Ralink Technology

2. Trade-offs of Training Sequence
Backward compatibility
Backward compatible with a is required by Functional Requirement. (IEEE r9)
A lesson from g.
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.

3. Objective of this Presentation
Present an effective training sequence that wouldn’t scarify other criteria.

4. The Proposed Training Sequence

5. The Proposed Training Sequence (cont.)
SPa, LPa and SIGa are a 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 r1 )
SIGn is a TBD signal field for n.
Save up to 16ms. (IEEE r1.)

6. 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.

7. The Short Preamble Sequences (cont.)

8. The Short Preamble Sequences (cont.)

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