1. Preamble for 120MHz Date: 2010-11-10 Authors: Nov, 2010 Month Year
doc.: IEEE yy/xxxxr0
Nov, 2010
Preamble for 120MHz
Date:
Authors:
Sun Bo, ZTE Corporation
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
Nov, 2010
Abstract
In R3.1.E: The draft specification shall include support for an efficient channelization in China’s (5,725 ~ 5,850 MHz) spectrum.
802.11ac is supposed to provide very high throughput, which requires to use wideband as much as possible. Following the Chinese spectrum and the existing 11ac tone allocations, we propose ac to support the 120 MHz PHY transmission.
Preamble have been defined for 80MHz and 160MHz (see ref. [1]). To support potential 120MHz transmission, this proposal put forward some preamble designs for 120MHz transmission.
Sun Bo, ZTE Corporation
John Doe, Some Company

3. 120MHz PHY Transmission Nov, 2010
Month Year
doc.: IEEE yy/xxxxr0
Nov, 2010
120MHz PHY Transmission
Two feasible options for 120MHz PHY transmission:
Option 1: Tone allocation for 120 MHz transmissions consists of one 80 MHz tone and one 40 MHz tone allocation in frequency.
Option 2: Tone allocation for 120 MHz transmissions consists of a single120 MHz tone allocation in frequency.
To acquire more data tones and higher throughput, we prefer a single120 MHz tone allocation in frequency.
Sun Bo, ZTE Corporation
John Doe, Some Company

4. Non-VHT portion of VHT mixed format preamble (1)
Nov, 2010
Non-VHT portion of VHT mixed format preamble (1)
Cyclic shift definition
The CSD (Cyclic Shift Diversity) values for up to 4 antennas in L-STF, L-LTF, and L-SIG are the same as the CSD values for the non-HT portion of the packet defined in Table 20-8 of Std n-2009.
L-STF definition
The 20 MHz L-STF pattern in the VHT preamble is as defined in of Std n The L-STF pattern for 120 MHz VHT transmissions shall repeat the 11n 20 MHz L-STF pattern in Equation (20-8) in each of the 20 MHz subchannel, then applying the following phase rotation per 20 MHz subchannel starting from the lowest 20 MHz subchannel in frequency: [c120], where c120 is the phase rotation per 20 MHz subchannel for 120 MHz transmissions and explained in the slide 13 .
Slide 4
Sun Bo, ZTE Corporation

5. Non-VHT portion of VHT mixed format preamble (2)
Nov, 2010
Non-VHT portion of VHT mixed format preamble (2)
L-LTF definition
The 20 MHz L-LTF pattern in the VHT preamble is as defined in of Std n-2009.
The 20 MHz L-LTF pattern in the VHT preamble is as defined in of Std n The L-LTF pattern for 120 MHz VHT transmissions shall repeat the 11n 20 MHz L-LTF pattern in each of the 20 MHz subchannel, then applying the following phase rotation per 20 MHz subchannel starting from the lowest 20 MHz subchannel in frequency: [c120].
L-SIG definition
The 20 MHz L-SIG pattern in the VHT preamble is as defined in of Std n The L-SIG for 120 MHz VHT transmissions shall repeat the 11n 20 MHz L-SIG pattern in each of the 20 MHz subchannel, then applying the following phase rotation per 20 MHz subchannel starting from the lowest 20 MHz subchannel in frequency: [c120].
Slide 5
Sun Bo, ZTE Corporation

6. VHT portion of VHT mixed format preamble
Nov, 2010
VHT portion of VHT mixed format preamble
Cyclic shift definition
The CSD (Cyclic Shift Diversity) values for up to 4 antennas in VHT-SIG-A are the same as the CSD values for the non-HT portion of the packet defined in Table 20-8 of Std n The CSD (Cyclic Shift Diversity) values for more larger than 4 antennas in VHT-SIG-A are the same as the CSD values for the VHT portion of the packet defined as in [1].
VHT-SIG-A definition
The content of VHT-SIG-A is same as in [1] except to increase 1 reserved bit for 120MHz bandwidth indication (see ref. [3]).
Slide 6
Sun Bo, ZTE Corporation

7. VHT-STF of 120MHz preamble
Nov, 2010
VHT-STF of 120MHz preamble
VHT-STF definition
The 20 MHz L-STF pattern in the VHT preamble is as defined in of Std n-2009.
The frequency domain sequence used to construct the VHT-STF in 20 MHz transmission is identical to the L-STF; in 120 MHz transmission, the VHT-STF is constructed from the 20 MHz version by replicating it in each 20 MHz band, frequency shifting, and applying the following phase rotation per 20 MHz subband starting from the lowest 20 MHz subchannel in frequency: [c120] .
VHT-STF frequency sequence without rotating phase :
VHT-STF-186,186={L-STF-58，58，0，0，0，0，0，0，0，0，0，0，0，VHT-STF-122，122}
Slide 7
Sun Bo, ZTE Corporation

8. VHT portion of VHT mixed format preamble
Nov, 2010
VHT portion of VHT mixed format preamble
VHT-LTF definition
The 20 MHz L-LTF pattern in the VHT preamble is as defined in of Std n-2009.
The frequency domain sequence used to construct the VHT-LTF in 20 MHz transmission is identical to the L-LTF; 120MHZ VHT-LTF use all 11n20 tones on both 20 MHz subchannels with filling of missing tones and applying a phase rotation on each 20MHz subchannel .
Slide 8
Sun Bo, ZTE Corporation

9. VHT LTF sequence structure
Nov, 2010
VHT LTF sequence structure
Assume that the VHT-LTF sequence is constructed by
Slide 9
Sun Bo, ZTE Corporation

10. VHT LTF sequence structure
Nov, 2010
VHT LTF sequence structure
Assuming the VHT-LTF structure of previous slide, to minimize the
PAPR, we need to optimize
Missing tone values
20 MHz phase rotations, [c1 c2 c3 c4 c5 c6]
where S are 20MHz phase rotations, and interp120NullL, interp120NullR are LTF sequences for all possible missing tone values. For VHT-LTF, pilot tones are multiplied by an R value, while other tones are multiplied by a P value. P, R is defined in [2].
Missing tones
interp40NullL(3 tones), interp120ExtraL (4 tones), interp120ExtraR (4 tones) , interp40NullR(3 tones)
interp40NullL= interp40NullR=[1 -1 1], as defined in of Std n-2009.
[c1 c2 c3 c4 c5 c6] is the phase rotation pattern consisting of {1, -1, j, -j} values。
Slide 10
Sun Bo, ZTE Corporation

11. Optimal Phase rotation and VHT-LTF sequence
Nov, 2010
Optimal Phase rotation and VHT-LTF sequence
The parameters which result in the optimal VHT-LTF
Phase rotation [c1 c2 c3 c4 c5 c6] = [1 j -1 –j -1 j];
[interp120ExtraL, interp120ExtraR] = [ , ]
Phase Rotations
per 20 MHz band
PAPR (2x oversampled)
L-STF
L-LTF
VHT-LTF120
[c1 c2 c3 c4 c5 c6] = [ ]
9.87 dB
11.36 dB
10.18 dB
[c1 c2 c3 c4 c5 c6] = [1 j 1 j 1 j]
6.86 dB
8.56 dB
8.30 dB
[c1 c2 c3 c4 c5 c6] = [ j]
4.33 dB
6.12 dB
6.43 dB
[c1 c2 c3 c4 c5 c6] = [1 j -1 -j -1 j]
3.47 dB
5.5 dB
4.86 dB
Slide 11
Sun Bo, ZTE Corporation

12. Optimal VHT-LTF sequence
Nov, 2010
Optimal VHT-LTF sequence
Optimal VHT-LTF frequency sequence (excluding phase rotation per 20 MHz subchannel) is
Slide 12
Sun Bo, ZTE Corporation

13. Phase Rotation for preamble and data tones
Nov. 2010
Phase Rotation for preamble and data tones
In all elements of an 120 MHz VHT PPDU , i.e., the L-STF, L-LTF, L-SIG, VHT-SIG-A, VHT-LTFs, VHT-SIG-B and the Data, subcarrier k, where , shall be multiplied by the following function of k, prior to transmission:
Slide 13
LvKaiying, ZTE Corporation

14. Nov, 2010
References
[1] Stacey, R. et al., Specification Framework for TGac, IEEE /0992r11, May 2010.
[2] IEEE Std n-2009.
[3] 10/XXXXr0, “signal fields design for 120MHz bandwidth”.
Slide 14
Sun Bo, ZTE Corporation

15. Nov, 2010
Thank you!
Sun Bo, ZTE Corporation