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Preamble Design aspects for 11ac

Preamble Design aspects for 11ac. Date: 2010-03-17. Authors:. Outlines. General PLCP frame format design Overall preamble structure Considerations for VHT-SIG design Consideration for VHT-LTF design. General PLCP frame format design issues. Preamble Modes to be considered VHT-Mixed Mode

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Preamble Design aspects for 11ac

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  1. Preamble Design aspects for 11ac Date: 2010-03-17 Authors:

  2. Outlines • General PLCP frame format design • Overall preamble structure • Considerations for VHT-SIG design • Consideration for VHT-LTF design

  3. General PLCP frame format design issues • Preamble Modes to be considered • VHT-Mixed Mode • VHT-Green Field Mode • Whether or not to support this features is under study • If needed, optimized sounding PLCP transmission can be one of examples • Common PLCP frame format for both SU/MU-MIMO • Overall PLCP frame designed and optimized for MU-MIMO • Consider SU-MIMO a subset of MU-MIMO operation • Whether VHT-SIGB is needed for SU-MIMO or not under study

  4. General PLCP frame format design (1/2) • VHT-SIG design aspects • Common VHT-SIG including common information for all STAs • STA specific VHT-SIG including user specific information • Separate field for STA specific parameters could be beneficial for incorporating potential technologies (e.g. power save features, etc) and related parameters • VHT-LTF design aspects • Two options (Overlapping VHT-LTF and non-overlapping VHT-LTF) could be useful depending on the receiver implementation and the environment (e.g. scatter-rich environments and Null-space deficient environments)

  5. General PLCP frame format design Option 3 (2/2) • General PLCP frame format design for MU-MIMO

  6. MU-MIMO support for Heterogeneous Devices users (1/3) • MU-MIMO may be able to support simultaneous multi-link peer-to-peer transmission for throughput enhancement • Various heterogeneous devices in a typical networked home scenarios (e.g. DTV, PC and handheld) • Each device may have different capabilities (e.g. supported channel bandwidth, MCS, FEC, etc) • It may be not typical to support MU-MIMO with all same CB capability 20MHz MU-MIMO 80MHz MU-MIMO AP 40MHz MU-MIMO

  7. MU-MIMO support for Heterogeneous Devices users (2/3) • Frequency • STA 1 with 40MHz CB capability • STA 2 • STA 2 with 80MHz CB capability • STA 1 • Time • User • 40MHz CB indication from AP of STA 1 and STA 2 • For STA1 and STA2, receive 40MHz data packet from CB indication in VHT-SIG

  8. MU-MIMO support for Heterogeneous Devices users (3/3) • Frequency • STA 1 with 20MHz CB capability • STA 2 • STA 2 with 80MHz CB capability • STA 1 • Time • User • 40MHz CB indication from AP to STA 1 and STA 2 • For STA2 with more than 40MHz CB capability, receive 40MHz data packet • For STA1 with less than 40MHz CB capability, receive 20MHz data packet through the rule ignoring CB indication in VHT-SIG • 2 bit length of CB indication in common VHT-SIG is enough to support up to 80MHz CB

  9. VHT-SIG parameter design guides and consideration 1/4 • []* : note that the necessity of supporting the particular field is under study

  10. VHT-SIG parameter design guides and consideration 2/4 • []* : note that the necessity of supporting the particular field is under study

  11. VHT-SIG parameter design guides and consideration 3/4 • N: number of MU-MIMO user • Expected summation may be increased depending on additional features for 11ac

  12. VHT-SIG parameter design guides and consideration 4/4 • STA-common fields do not necessary need to be positioned in VHT-SIGA • STA-specific fields do not necessary need to be positioned in VHT-SIGB • Extremely premature to make decisions on how to optimize signaling for SIGA and SIGB • Some fields may be obvious • Further investigation needed for other fields • Bandwidth indication, Group ID, information for power save features, etc

  13. Channel Estimation for PLCP frame • LTF for 20MHz channel bandwidth of Legacy transmission • 48 data number per OFDM symbol with L-LTF • 24 bits based on BPSK1/2 for L-SIG • LTF for 20MHz channel bandwidth of VHT transmission • 52 data number per OFDM symbol with VHT-LTF • 26 bits based on (Rotated BPSK1/2) for VHT-SIGB

  14. MU-MIMO VHT-LTF design aspects (1/3) • Non-zero element unitary transformation matrix for LTF • In case total number of Spatial Stream at AP side is larger than 4 • 8 LTF transmissions • Each STA tries to calculate channel estimation for its spatial stream by using all 8 LTF transmissions • Potential Issues • High PHY PLCP header overhead compared with SU-MIMO

  15. MU-MIMO VHT-LTF design aspects (2/3) • Unitary transformation matrix with Zero elements for LTF • LTF is transmitted in LTF sets as if each STA is in SU-MIMO • When a LTF set for a STA is transmitted, Zero is transmitted in other spatial streams • Each STA is only required to estimate channel for its receiving SS • Each STA may try to estimate channel for other SS to enhance performance

  16. MU-MIMO VHT-LTF design aspects (3/3) • In case MU-MIMO precoding so that interference between STAs is minimal • Practical implementation impairments will effect amount of interference suppression for each STA, but stable link conditions (MU-MIMO favorable environments) will allow sufficient nulling of interference • Transmitted energy from other spatial streams will not contribute much to channel estimation enhancement • LTF transformation matrix size of 4x4 and 8x8 will be needed for SU-MIMO operation • LTF channel estimation algorithm does not change between SU-MIMO and MU-MIMO • Allows shorter LTF transmission time, thus save PHY overhead due to MU-MIMO for typical STA pairing cases (STAs with 2 Rx, and up to 2 SS receive capability)

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