1. 80MHz Tone Allocation Date: 2010-03-17 Authors: Month Year Month Year
doc.: IEEE yy/xxxxr0
doc.: IEEE yy/xxxxr0
80MHz Tone Allocation
Date:
Authors:
Slide 1
Sudhir Srinivasa et al.
Page 1
John Doe, Some Company
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
Introduction
Functional requirements as per the spec framework document [1]:
R3.1.A (Channelization): The draft specification shall include support for 80 MHz PHY transmission.
Possible preambles for 80MHz OFDM have been discussed in [2, 3].
This presentation will focus on a possible data and pilot tone mapping for 80MHz VHT data.
Sudhir Srinivasa et al.
John Doe, Some Company

3. Month Year
doc.: IEEE yy/xxxxr0
Tone Allocation
Legacy preamble portion (LLTF/LSIG) needs to be repeated across each of the 20MHz sub-bands
(6+5) guard tones in each 20MHz legacy portion, therefore (6+5) guard tones in 80MHz.
Spectrum mask and filter design will have to conform to (6+5) guard tones anyway
Propose to use (6 + 5) guard tones, 3 DC tones in 80MHz
-128
127
122 2 -2
-122
121 Data/Pilot Tones
6 Guard Tones
5 Guard Tones
3 DC Tones
Freq
Subcarrier Index
Sudhir Srinivasa et al.
John Doe, Some Company

4. Location of pilot subcarriers
Month Year
doc.: IEEE yy/xxxxr0
Location of pilot subcarriers
The n spec mandates that
LSIG of 20MHz packets have pilots at {±7, ±21} and
Repetition of the LSIG sequence across 80MHz
LSIG in an 80MHz 11ac packet will have pilots at location pairs belonging to {±11, ±25, ±39, ±53, ±75, ±89, ±103, ±117}.
Not desirable to change pilot positions between the legacy (11a/n) and VHT parts of the packet.
Some implementers may average pilots across and legacy preamble (SIG fields) and VHT data.
For simple receiver design, better to pick 80MHz pilots among these 16 tones.
Sudhir Srinivasa et al.
John Doe, Some Company

5. Number of pilot subcarriers
Month Year
doc.: IEEE yy/xxxxr0
Number of pilot subcarriers
Simulations show that the performance gap between using 8 and 10 pilots is small. (See backup slides)
Reducing the number of pilots to 6, however, results in a ~1dB loss in performance in some scenarios (See backup slides)
We propose that 11ac packets use 8 pilots during 80MHz VHT-DATA portion.
Can be chosen such that they are maximally separated, with indices {±103, ±75, ±39, ±11}
Sudhir Srinivasa et al.
John Doe, Some Company

6. Month Year
doc.: IEEE yy/xxxxr0
References
IEEE /0992r3, R. Stacey et al., Proposed Specification Framework for TGac
IEEE /0070r1, H. Zhang et al., ac Preamble
IEEE r0, Y. Tu et. Al., Proposed TGac Preamble
Sudhir Srinivasa et al.
John Doe, Some Company

7. Simulation Results 1 Month Year doc.: IEEE 802.11-yy/xxxxr0
Sudhir Srinivasa et al.
John Doe, Some Company

8. Simulation Results 2 Month Year doc.: IEEE 802.11-yy/xxxxr0
Sudhir Srinivasa et al.
John Doe, Some Company