1. Cyclic Shift Values for Legacy Portion
Month Year
doc.: IEEE yy/xxxxr0
Sept 2010
Cyclic Shift Values for Legacy Portion
Date:
Authors:
Leonardo Lanante Jr./Kyushu Institute of Technology
John Doe, Some Company

2. Outline Introduction Simulation Results Summary Proposed CSD Values
Sept 2010
Outline
Introduction
Simulation Results
Summary
Proposed CSD Values
Strawpolls
Leonardo Lanante Jr./Kyushu Institute of Technology

3. Month Year
doc.: IEEE yy/xxxxr0
Sept 2010
Introduction
Last July 2010 TGac meeting, it was agreed that the CSD for the　non-VHT portion of 11ac be constrained to within 200ns for any number of antennas [1].
When the number of antennas is less than or equal to 4, 11ac uses the 11n legacy CSD values.
This presentation is a proposal for CSD values when the number of antennas is more than 4.
Leonardo Lanante Jr./Kyushu Institute of Technology
John Doe, Some Company

4. Month Year
doc.: IEEE yy/xxxxr0
Sept 2010
Methodology
CSD is a simple way to avoid unintentional beamforming that causes large variations in receive power.
For NTx<5, 11n values were used for 11ac
For NTx=5, the 11n values can be naturally extended to [0 -50ns -100ns -150ns -200ns]
To obtain CSD values for NTx=[6, 7, 8], we performed a linear full search from all possible sequences with 25ns resolution
1Tx
2Tx
3Tx
4Tx 1 2
-200ns 3
-100ns 4
-50ns
-150ns
Leonardo Lanante Jr./Kyushu Institute of Technology
John Doe, Some Company

5. Cost Function Definition
Month Year
doc.: IEEE yy/xxxxr0
Sept 2010
Cost Function Definition
99%
The smaller R is, the lesser variation in the computed L-STF Power. 1% R
R= Fluctuation of computed L-STF Power [2]
Leonardo Lanante Jr./Kyushu Institute of Technology
John Doe, Some Company

6. Month Year
doc.: IEEE yy/xxxxr0
Sept 2010
Full Search Method
For NTx=[6, 7, 8], we search for CSD sequence with least R
The CSD value search used a resolution of 25ns
All CSD values are distinct per antenna
The values are obtained from the base sequence
CSD_MAIN= [ ].
Note: Corresponding CSD values are in ns and negative)
Procedure to pick a CSD_SEQ for NTx=6,7,8
CSD_SEQ = [ … ]
The rest of NTx-1 elements come from the non-zero values of CSD_MAIN. One combination of NTx-1 elements can be permuted to produce a set of CSD_SEQs
The first element is always zero
Leonardo Lanante Jr./Kyushu Institute of Technology
John Doe, Some Company

7. Example: CSD_SEQs for NTx=6
Month Year
doc.: IEEE yy/xxxxr0
Sept 2010
Example: CSD_SEQs for NTx=6
CSD_MAIN= [ ]
[ ] [ ]
Total of 120 distinct permutations
[ ]
Combination Set 1
[ ]
[ ] [ ]
Total of 120 distinct permutations
[ ]
Each combination set has distinct elements
Combination Set 2
[ ]
Leonardo Lanante Jr./Kyushu Institute of Technology
John Doe, Some Company

8. Example: CSD_SEQs for NTx=6
Month Year
doc.: IEEE yy/xxxxr0
Sept 2010
Example: CSD_SEQs for NTx=6
[ ] [ ]
Total of 120 distinct permutations
[ ]
Combination Set 55
[ ]
[ ]
Total of 120 distinct permutations
[ ]
Combination Set 56
[ ]
# Combination Sets =
# Permutations = (NTx-1)!
Total Possible Sequences = # Combination Sets x # Permutations
Leonardo Lanante Jr./Kyushu Institute of Technology
John Doe, Some Company

9. Simulation Results for NTx=6
Month Year
doc.: IEEE yy/xxxxr0
Simulation Results for NTx=6
Sept 2010
Effect of Permutation ( Combination Sets Superimposed)
Average per color
Channel B
Channel D
RminB
RminD
Red – Combinations sets with maximum of 125 (1 set)
Blue – Combinations sets with maximum of 150 (5 sets)
Green – Combinations sets with maximum of 200 (35 sets) Lower Ave. Fluctuation
RminB = CSD_SEQ with minimum R in Channel Model B RminD = CSD_SEQ with minimum R in Channel Model D
Leonardo Lanante Jr./Kyushu Institute of Technology
John Doe, Some Company

10. Simulation Results for NTx=7
Month Year
doc.: IEEE yy/xxxxr0
Simulation Results for NTx=7
Sept 2010
Effect of Permutation (Combination Sets Superimposed)
Average per color
Channel B
Channel D
RminB
RminD
Red – Combinations sets with maximum of 150 (1 sets )
Blue – Combinations sets with maximum of 175 (6 sets)
Green – Combinations sets with maximum of 200 (21 sets) Lower Ave. Fluctuation
RminB = CSD_SEQ with minimum R in Channel Model B RminD = CSD_SEQ with minimum R in Channel Model D
Leonardo Lanante Jr./Kyushu Institute of Technology
John Doe, Some Company

11. Simulation Results for NTx=8
Month Year
doc.: IEEE yy/xxxxr0
Simulation Results for NTx=8
Sept 2010
Effect of Permutation (Combination Sets Superimposed)
Average per color
Channel B
Channel D
RminB
RminD
Blue – Combinations sets with maximum of 175 (1 set)
Green – Combinations sets with maximum of 200 (7 sets) Lower Ave. Fluctuation
RminB = CSD_SEQ with minimum R in Channel Model B RminD = CSD_SEQ with minimum R in Channel Model D
Leonardo Lanante Jr./Kyushu Institute of Technology
John Doe, Some Company

12. Sept 2010
Observations
In general, relative performance of any CSD_SEQ compared to another depends on the channel model (i.e. Channel B or D)
Absolutely optimal CSD_SEQ also changes depending on the channel model
Better overall performance can be obtained if CSD_SEQ is exactly within 200ns (i.e. it belongs in a combination set that includes the element 200).
Based on this observations, we are proposing the following CSD values …
Leonardo Lanante Jr./Kyushu Institute of Technology

13. Proposed CSD Values for non-VHT Portion
Month Year
doc.: IEEE yy/xxxxr0
Sept 2010
Proposed CSD Values for non-VHT Portion
Number of TX chains
Cyclic Shift for TX chain 1 (ns)
Cyclic Shift for TX chain 2 (ns)
Cyclic Shift for TX chain 3 (ns)
Cyclic Shift for TX chain 4 (ns)
Cyclic Shift for TX chain 5 (ns)
Cyclic Shift for TX chain 6 (ns)
Cyclic Shift for TX chain 7 (ns)
Cyclic Shift for TX chain 8 (ns) 1 2
-200 3
-100 4
-50
-150 5 6
-25 7
-75 8
-125
Leonardo Lanante Jr./Kyushu Institute of Technology
John Doe, Some Company

14. Sept 2010
Strawpoll #1
Do you support using the CSD values of [0 -50ns -100ns -150ns -200ns], natural extension from 11n CSD, for five transmit antennas in the non-VHT portion of 11ac mixed mode packet and updating the specification framework accordingly?
Yes No
Abstain
Leonardo Lanante Jr./Kyushu Institute of Technology

15. Sept 2010
Strawpoll #2
Do you support using the CSD values, simple linear incremental values including -200ns, in slide 13 for 6, 7, and 8 antennas in the non-VHT portion of 11ac mixed mode packet and updating the specification framework accordingly ?
Yes No
Abstain
Leonardo Lanante Jr./Kyushu Institute of Technology

16. Sept 2010
References
[1] – Yung-Szu Tu et. al, Cyclic Shift For More Than 4 Antennas in Non-VHT Portion. doc.: /0916r0
[2]- Aoki et. al, Preamble Structure for MIMO-OFDM WLAN Systems Based on IEEE A, PIMRC 2006
Leonardo Lanante Jr./Kyushu Institute of Technology