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Dft spreading ofdm options for 11ah phy enhancement Date: 2012-3-15
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tarix | 02.10.2018 | ölçüsü | 391,5 Kb. | | #72016 |
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DFT spreading OFDM options for 11ah PHY enhancement
Abstract This presentation proposes DFT spreading OFDM options for 11ah PHY enhancement.
TGah decided to support 2/4/8/16MHz signals based on the down clocked versions of 11ac 20/40/80/160 MHz, and an 1MHz signal based on 32FFT. TGah decided to support 2/4/8/16MHz signals based on the down clocked versions of 11ac 20/40/80/160 MHz, and an 1MHz signal based on 32FFT. - Both 2MHz and 1MHz receptions are mandatory in TGah PHY.
DFT spreading OFDM (DFTS-OFDM) is adopted for the uplink in IMT-2000 LTE, and the concept of DFTS-OFDM was presented in IEEE 802.11-11/0753r0. We propose DFTS-OFDM options for 11ah PHY enhancement for 1MHz and 2MHz signals, especially for the purpose of sensor applications in this presentation. - Advantage of DFT-spreading OFDM
- Proposal of DFT spreading OFDM option.
Why DFTS-OFDM ? Battery driven wireless terminals are used for sensor network applications Basic Requirements for the use cases of 1a/1f and 2d/2e/2f Computer simulation results on PAPR, Power spectrum after HPA and BER are shown in the following slides. - 56 points DFT spreading is assumed.
Comparison of PAPR
DFTS-OFDM achieved less ACL (adjacent channel power leakage) when output backoff is small. DFTS-OFDM is more suitable for low output backoff operation.
BER performance DFTS-OFDM achieved better BER performance, when OBO=0dB-3dB.
Transmission flow for DFTS-OFDM options (1) DFTS-OMDF options will be useful for 1MH/2MHz BPSK/QPSK signals. It is desirable not to change the basic signal design and preamble of OFDM signals. - 1MHz (32 FFT)
- 2MHz(64 FFT)
- 52 Data tones, 4 Pilot tones, 7 Guard tones, and 1 DC tone
Transmission flow for DFTS-OFDM options (2) DFT on the transmission side - 26 or 27 points DFT for 1MHz, 56 or 57 points DFT for 2MHz
IDFT and FDE on the reception side
57 DFT/IDFT is the simplest approach for DFTS-OFDM, however FFT algorithm can not be applied for DFT/IDFT implementation since 57 is not power of two. 57 DFT/IDFT is the simplest approach for DFTS-OFDM, however FFT algorithm can not be applied for DFT/IDFT implementation since 57 is not power of two. - It needs large amount of signal processing for DFT/IDFT.
56 DFT/IDFT is another simple approach for DFTS-OFDM. - 56 DFT/IDFT needs less amount of signal processing than 57 DFT/IDFT.
- DC tone is replaced with one data tone.
Though 57/56 DFT/IDFT needs large amount of signal processing, it is worth employing DFTS-OFDM for 1MHz/2MHz signals for sensor network applications where low PAPR is strongly desired. - Direct DFT/IDFT will be possible because of its low symbol rate.
- Other DFTS-OFDM based approaches can be employed based on the trade-off between PAPR and signal processing.
Do you support DFTS-OFDM based options for 11ah PHY enhancement for its advantage of low PAPR and better BER performance in non-linear HPA operation ? Do you support DFTS-OFDM based options for 11ah PHY enhancement for its advantage of low PAPR and better BER performance in non-linear HPA operation ? - Applied only for 1MHz/2MHz signals with BPSK/QPSK mode.
- Needs further considerations on other approaches based on trade-off between PAPR and signal processing.
References [1] 011-11-0753-00-00ah-dft-spread-ofdm-optimized-for-802-11ah [2] 11-11-1482-00-00ah-preamble-format-for-1-MHz [3] 11-11-1483-00-00ah-11ah-preamble-for-2MHz-and-beyond [4] 11-11-1484-06-00ah-11ah-phy-transmission-flow
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