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80MHz Tone Allocation

80MHz Tone Allocation. Date: 2010-05-17. Authors:. Slide 1. 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.

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80MHz Tone Allocation

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  1. 80MHz Tone Allocation Date: 2010-05-17 Authors: Slide 1 Sudhir Srinivasa et al.

  2. 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.

  3. 6 Guard Tones 121 Data/Pilot Tones 3 DC Tones 121 Data/Pilot Tones 5 Guard Tones Freq -122 Subcarrier Index -2 2 -128 122 127 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 Sudhir Srinivasa et al.

  4. Location of pilot subcarriers • The 802.11n 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.

  5. 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.

  6. References • IEEE802.11-09/0992r3, R. Stacey et al., Proposed Specification Framework for TGac • IEEE802.11-10/0070r1, H. Zhang et al., 802.11ac Preamble • IEEE802.11-10-0130r0, Y. Tu et. Al., Proposed TGac Preamble Sudhir Srinivasa et al.

  7. Simulation Results 1 Sudhir Srinivasa et al.

  8. Simulation Results 2 Sudhir Srinivasa et al.

  9. Strawpolls Sudhir Srinivasa et al.

  10. Strawpoll #1: • Do you support to add to the specification frame work document (IEEE 802.11-09/0992r9) • 3.x Data Formats • 3.x.2 OFDM Modulation:  The draft specification shall have 3 DC tones at (0, ±1) in 80MHz VHT data field. • Yes • No • Abstain Sudhir Srinivasa et al.

  11. Strawpoll #2: • Do you support to add to the specification frame work document (IEEE 802.11-09/0992r9) • 3.x Data Formats • 3.x.2 OFDM Modulation:  The draft specification shall have 5 null tones at the upper tone edges (tone indices 123, 124, 125, 126, 127) and 6 null tones at the lower tone edges (tone indices -128, -127, -126, -125, -124, -123) of the 80MHz VHT data. • Yes • No • Abstain Sudhir Srinivasa et al.

  12. Strawpoll #3: • Do you support to add to the specification frame work document (IEEE 802.11-09/0992r9) • 3.x Data Formats • 3.x.1 Pilot Subcarriers:  The draft specification shall have 8 pilot tones, with the positions {±103, ±75, ±39, ±11}, for 80MHz VHT data. • Yes • No • Abstain Sudhir Srinivasa et al.

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