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Pilot Sequence design up to 8 Spatial Streams

Pilot Sequence design up to 8 Spatial Streams. Authors:. Date: 2010-07-13. Abstract. We discuss some of the pilot design principles for 11ac and propose use a single pilot mother matrix in which all pilots for each bandwidth and spatial stream get its pilot sequence values.

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Pilot Sequence design up to 8 Spatial Streams

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  1. Pilot Sequence design up to 8 Spatial Streams Authors: Date: 2010-07-13 Daewon Lee, LG Electronics

  2. Abstract We discuss some of the pilot design principles for 11ac and propose use a single pilot mother matrix in which all pilots for each bandwidth and spatial stream get its pilot sequence values Daewon Lee, LG Electronics

  3. Pilot Sequence Design • Design Target • Pilot sequences must be defined up to 8 spatial streams • Pilot sequence also must be defined for 80 MHz • Design principles • Performance difference between different pilot sequences is not expected to be large • Rather than defining a pilot sequence for each instance (number of spatial streams & bandwidth size) define a large sequence matrix for all spatial streams and bandwidth may be preferable Daewon Lee, LG Electronics

  4. Discussion (1/2) • performance in various scenarios • It will be important to consider tracking performance in various scenarios • orthogonal pilot sequence across spatial streams may give robust performance in case of correlated Tx antenna configurations • some studies [1] show that having orthogonal pilot design may be more robust for highly correlated channels • pilot tracking functionality • Orthogonal pilots do not necessary mean pilot tracking functionality is mandated to gather pilots over multiple OFDM symbols for processing Daewon Lee, LG Electronics

  5. Discussion (2/2) • Complexity for supporting orthogonal pilot design • 11n pilots has been design to be orthogonal between spatial streams (note that not all pilot tones in 40MHz are time domain orthogonal) • if orthogonal pilot tone tracking is implemented for 11n then same functionality can be re-utilized in 11ac • no mandate of separate phase tracking per spatial stream • may not be needed if single LO is used at Tx/Rx • no additional complexity for phase tracking is expected • PAPR of pilot sequence • PAPR increase due to certain ‘bad’ pilot sequences design is expected to be marginal because OFDM data tones will effect the PAPR the most • some PAPR analysis for pilot in VHT data portion is shown in the Annex Daewon Lee, LG Electronics

  6. Pilot Sequence for 20 MHz • 20 MHz Pilot Sequence Positions • 11n Pilot Sequence • Proposed 11ac Pilot Sequence -21 -7 7 21 Subcarrier index : pilot subcarrier : data subcarrier Daewon Lee, LG Electronics

  7. Pilot Sequence for 40 MHz • 40 MHz Pilot Sequence Positions • 11n Pilot Sequence • Proposed 11ac Pilot Sequence : pilot subcarrier : data subcarrier Subcarrier index -53 -25 -11 11 25 53 Daewon Lee, LG Electronics

  8. Pilot Sequence for 80 MHz • 80 MHz Pilot Sequence Positions • Proposed 11ac Pilot Sequence : pilot subcarrier : data subcarrier Subcarrier index -103 -75 -39 -11 11 39 75 103 Daewon Lee, LG Electronics

  9. Proposed pilot sequence mother matrix • Pilot Sequence mother matrix Daewon Lee, LG Electronics

  10. Summary • We give one candidate proposal for the pilot sequences for data portion of the VHT PLCP preamble • We propose to further consider different pilot sequence for each spatial streams • We propose to further consider orthogonal pilot sequence design to make pilot tracking more robust against various deployment scenarios Daewon Lee, LG Electronics

  11. Reference • [1] Aoki, T.; Sandell, M.; , "Analysis of pilots for residual frequency offset estimation in MIMO OFDM systems," Wireless Communications, IEEE Transactions on , vol.8, no.3, pp.1128-1132, March 2009. Daewon Lee, LG Electronics

  12. Annex Daewon Lee, LG Electronics

  13. Annex. PAPR analysis of proposed pilot sequence (1/3) • Data PAPR analysis as reference • 20 MHz BW with proposed pilot sequence • Different CDF curves represent CDF of each spatial stream Daewon Lee, LG Electronics

  14. Annex. PAPR analysis of proposed pilot sequence (2/3) • 40 MHz BW with proposed pilot sequence & PAPR reduction γ sequence [ +1 +j ] used • Different CDF curves represent CDF of each spatial stream Daewon Lee, LG Electronics

  15. Annex. PAPR analysis of proposed pilot sequence (3/3) • 80 MHz BW with proposed pilot sequence & PAPR reduction γ sequence [ +1 +j +1 +j ] used • Different CDF curves represent CDF of each spatial stream Daewon Lee, LG Electronics

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