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Increased Network Throughput with Channel Width Related CCA and Rules

Increased Network Throughput with Channel Width Related CCA and Rules. Date: 2014-07-14. Authors:. Background and Objectives. James Wang et. al., MediaTek.

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Increased Network Throughput with Channel Width Related CCA and Rules

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  1. Increased Network Throughput with Channel Width Related CCA and Rules Date: 2014-07-14 Authors: James Wang et. al., MediaTek

  2. Background and Objectives James Wang et. al., MediaTek Raising CCA levels has been shown to increase spatial re-use which leads to significant increase in the network throughput in dense deployment scenarios (ref. 1-10). However, raising CCA levels leads to high collisions This contribution investigates method to alleviate the above issues when raising the CCA levels, thereby increasing the network throughpu This presentation focuses on inter-BSS traffic. (Method of distinguishing inter-BSS traffic and inter-BSS traffic is not included)

  3. High Channel Width Transmission • Higher channel width transmission causes less interference in dense deployment environment • TX spectral density is lower Same power, different data rates • Higher channel width transmission is more bandwidth/power efficient • Reduced guard tones (higher number of subcarriers) • Lower rate codes are more powerful James Wang et. al., MediaTek

  4. 11ac EDCA TXOP and Channel Access 11ac obtains an EDCA TXOP is based solely on activity of the primary channel (busy or idle conditions) The primary channel is BUSY, if one of the conditions listed in Table 22-27 is met James Wang et. al., MediaTek

  5. 11ac EDCA TXOP and Channel Access • Transmit channel width determination is based on the secondary channel CCA during an interval (PIFS) immediately preceding the start of TXOP. • Secondary channel CCA levels James Wang et. al., MediaTek

  6. Channel Width Considerations Transmit Spectral Density STA2 STA1 6 dB 20 MHz 9 dB AP2 40 MHz 80 MHz 20MHz PPDU 160 MHz AP1 20M radius 80 or 160MHz PPDU • Signal propagation range is determined by the TX spectral density (power/Hz) and the channel propagation loss • Same transmit power, wider TX channel widths  lower TX spectral density  shorter range • The baseline (primary channel) CCA levels are based on equal spectral density for all RX channel widths • CCA_Level/channel width (in unit of 20MHz) = -82 dBm for 20, 40, 80, 160 MHz • However, the TX spectral density is not the same for all TX channel widths • TX_PWR/20M > TX_PWR/40M > TX_PWR/80M > TX_PWR/160M • Narrower TX ch. width transmission interferes (defers) a wider ch. width transmission • The likelihood of the wider ch. width transmission is reduced James Wang et. al., MediaTek

  7. Proposed Enhanced Channel Access for Wider TX Channel Width Transmission -1 • As shown, if AP1 intends to transmit a 80MHz PPDU, it can ignore the 20MHz PPDU by STA1 at -82 dBm. The CCA level for 20MHz PPDU can be raised by 6 dB (from -82 dBm to -76 dBm). • This illustration is only for inter-BSS transmission (STA1, STA2, STA3 are OBSS) STA1 STA2 STA3 20M @-76dBm 20M @-82dBm 80M @-76dBm AP1 Intended channel width=80M • Based the CCA Level on the intended TX channel width(s) • Wider intended TX channel width, higher CCA levels James Wang et. al., MediaTek

  8. Proposed Enhanced Channel Access for Wider TX Channel Width Transmission - 2 • As shown AP1 reduces TX power of 20M, 40MHz PPDUs such that it has the same spectral density as 80MHz PPDU (intended TX BW=80MHz) 20M PPDU 20M PPDU (reduced power) Reduce the transmit power of 20M and 40M PPDUs such that it has the same power spectral density as 80MHz PPDU used Transmit Spectral Density 40M PPDU (reduced power) 20 MHz 80M PPDU 40 MHz AP1 Intended channel width=80M 80 MHz 80 MHz 40 MHz 20 MHz 80 MHz • If AP gain channel access for wider channel width transmission with higher CCA level, it should transmit the signal at the same power spectral density as the intended TX channel width James Wang et. al., MediaTek

  9. Primary CCA Levels for Different TX Channel Widths • Proposed that CCA busy level shall be based on the transmit channel width instead of receive channel width • For intended 20 MHz transmission channel width, • CCA for primary 20MHz: -82 dBm • Max tx spectral density = tx power/20MHz • For intended 40 MHz transmission channel width, • CCA for primary 20MHz: -8279dBm • CCA for 40MHz: -79 dBm • Max tx spectral density=tx power/40MHz • For intended 80MHz transmission channel width, • CCA for primary 20MHz: -8276dBm • CCA for primary 40MHz: -7976dBm • CCA for 80MHz: -76dBm • Max tx spectral density = tx power/80MHz • For intended 160MHz (80MHz+80MHz) transmission channel width, • CCA for primary 20MHz: -8273dBm • CCA for primary 40MHz: -7973dBm • CCA for primary 80MHz: -7973dBm • CCA for 160MHz: -73dBm • Max tx spectral density = tx power/160MHz • Note 1: We only recommend adjusting relative CCA levels based on TX channel widths. We are open to proposals adjusting absolute CCA levels. • Note 2: For multiple intended TX channel widths, transmitter can run multiple EDCA queues. James Wang et. al., MediaTek

  10. Example EDCA Channel Access Transmission Rules • In the example, the intended transmit channel width is 80MHz. It is assumed that the device has a transmit power spectral density for the 80MHz transmission is PD80M(=TX Power/80MHz) and the corresponding CCA level (Slide 7) for 80MHz transmit channel width. • Proposed Modified EDCA Channel Access in a VHT BSS for intended Transmit channel width of 80MHz: If a STA is permitted to begin a TXOP (as defined in 9.19.2.3 (Obtaining an EDCA TXOP)) and the STA has at least one MSDU pending for transmission for the AC of the permitted TXOP, the STA shall perform exactly one of the following steps: • Transmit a 160 MHz or 80+80 MHz mask PPDU if the secondary channel, the secondary 40 MHz channel and the secondary 80 MHz channel were idle during an interval of PIFS immediately preceding the start of the TXOP • Transmit an 80 MHz mask PPDU at a power spectral density = PD80Mon the primary 80 MHz channel if both the secondary channel and the secondary 40 MHz channel were idle during an interval of PIFS immediately preceding the start of the TXOP • Transmit a 40 MHz mask PPDU at a power spectral density ≤ PD80Mon the primary 40 MHz channel if the secondary channel was idle during an interval of PIFS immediately preceding the start of the TXOP • Transmit a 20 MHz mask PPDU at a power spectral density ≤ PD80Mon the primary 20 MHz channel • Restart the channel access attempt by invoking the backoff procedure as specified in 9.19.2 (HCF contention-based channel access (EDCA)) as though the medium is busy on the primary channel as indicated by either physical or virtual CS and the backoff timer has a value of 0 James Wang et. al., MediaTek

  11. Transmission based on 80MHz Intended TX Channel Width 160MHz Illustration of a device run EDCA transmission based on 80MHz intended TX channel width CCA levels (6 dB above current CCA level for 20MHz) James Wang et. al., MediaTek

  12. Conclusions and Future Works • Current CCA levelsandtransmissionrules • lower likelihood of high channel width transmission (deferred inappropriately due to out-of-range narrower channel width transmission) • Significant network throughput increase can be accomplished in a dense deployment scenarios due to • Higher CCA levels (based on the intended transmission channel width) increase the likelihood of wide channel width transmission • Wider channel width transmission is more bandwidth/power efficiency due to more powerful low rate code and less guard tones • Simulation results will be provided in Part 2 of this contribution James Wang et. al., MediaTek

  13. References Ron Porat, Broadcom, 11-14-0082-00 Improved Spatial Reuse Feasibility - Part I Jinjing Jiang, Marvell, 11-14-0372-00 System level simulations on increased spatial reuse Graham Smith, DSP Group, 11-14-1290-01 Dynamic Sensitivity Control for HEW Graham Smith, DSP Group, 11-14,0294-02 Dynamic Sensitivity Control Channel Selection and Legacy Sharing Imad Jamil, Orange, 11-14-0523-00-00ax Mac Simulation Results for DSC and TPC Graham Smith, DSP Group, 11-14-0328-02 Dense Apartment Complex Throughput Calculations Graham Smith, DSP Group, 11-14-0045-02 E-Education Analysis Graham Smith, DSP Group, 11-14-0058-01 Pico Cell Use Case Analysis Graham Smith, DSP Group, 11-13-1489-05 Airport Capacity Analysis Graham Smith, DSP Group, 11-13-1487-02 Apartment Capacity - DSC and Channel Selection James Wang et al, Mediatek

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