Transcript 11-14/0880
July 2014 doc.: IEEE 802.11-14/0880r1
Increased Network Throughput with Channel Width Related CCA and Rules
Date:
2014-07-14 Authors:
Name
James Wang
Affiliations Address Phone email
Jianhan Liu [email protected]
Thomas Pare MediaTek 2860 Junction Ave., San Jose, CA 95134 USA +1-408-526 1899-88109 [email protected]
James Yee Chingwa Yu Alvin Hsu Submission Slide 1 [email protected]
James Wang et. al., MediaTek
July 2014 doc.: IEEE 802.11-14/0880r1
Background and Objectives
• • • •
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)
Submission 2 James Wang et. al., MediaTek
July 2014 doc.: IEEE 802.11-14/0880r1
High Channel Width Transmission
• •
Higher channel width transmission is more bandwidth/power efficient
– Reduced guard tones (higher number of subcarriers) – Lower rate codes are more powerful
Higher channel width Data Rate vs Sensitivity for Different MCS/Channel Widths, 1SS transmission causes less
800 40MHz 700
interference in dense deployment environment
• TX spectral density is lower 20MHz 80MHz 160MHz 600 500 400 300 200 Same power, 100 -85 -80 -75 -70 -65 -60 -50 data rates
11ac MCS Minimum Sensitivity (dBm) and Data Rates,
0 -45 Submission 3 James Wang et. al., MediaTek
July 2014 doc.: IEEE 802.11-14/0880r1
• •
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
Submission 4 James Wang et. al., MediaTek
July 2014 doc.: IEEE 802.11-14/0880r1
• •
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
2 nd Channel
Any signal within the secondary 20 MHz channel Any signal within the secondary 40 MHz channel Any signal within the secondary 80 MHz 80 MHz non-HT duplicate or VHT PPDU 40 MHz non-HT duplicate, HT_MF, HT_GF or VHT PPDU 20 MHz NON_HT, HT_MF, HT_GF or VHT PPDU
CCA Level
≥-62 dBm ≥-59 dBm ≥-56 dBm ≥-69 dBm ≥-72 dBm ≥-72dBm Submission 5 James Wang et. al., MediaTek
Jan 2014 doc.: IEEE 802.11-14/0880r1
• • • • •
Channel Width Considerations
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
Transmit Spectral Density STA2 STA1 AP2
20MHz PPDU
AP1 20 MHz 40 MHz 6 dB 80 MHz 9 dB 160 MHz 20M radius
80 or 160MHz PPDU
Slide 6 Submission James Wang et. al., MediaTek
July 2014 doc.: IEEE 802.11-14/0880r1
Proposed Enhanced Channel Access for Wider TX Channel Width Transmission -1
•
Based the CCA Level on the intended TX channel width(s)
– Wider intended TX channel width, higher CCA levels •
As shown, if AP1 intends to transmit a 80MHz PPDU, it can ignore the 20MHz PPDU by STA1 dB (from -82 dBm to -76 dBm).
STA1
at -82 dBm. The CCA level for 20MHz PPDU can be raised by 6
20M @-82dBm •
This illustration is only for inter BSS transmission (STA1, STA2, STA3 are OBSS)
Submission 7 STA2 20M @-76dBm STA3 80M @-76dBm AP1 Intended channel width=80M James Wang et. al., MediaTek
July 2014 doc.: IEEE 802.11-14/0880r1
Proposed Enhanced Channel Access for Wider TX Channel Width Transmission - 2
•
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
•
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 Transmit Spectral Density Reduce the transmit power of 20M and 40M PPDUs such that it has the same power spectral density as 80MHz PPDU used 20M PPDU (reduced power) 20 MHz 80 MHz 40 MHz 80 MHz 40M PPDU (reduced power) 80M PPDU 20 MHz 40 MHz 80 MHz AP1 Intended channel width=80M Submission 8 James Wang et. al., MediaTek
July 2014 doc.: IEEE 802.11-14/0880r1
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: -8279 dBm – CCA for 40MHz: -79 dBm – Max tx spectral density=tx power/40MHz
For intended 80MHz transmission channel width,
– CCA for primary 20MHz: -8276 dBm – CCA for primary 40MHz: -7976 dBm – CCA for 80MHz: -76dBm – Max tx spectral density = tx power/80MHz
For intended 160MHz (80MHz+80MHz) transmission channel width,
– CCA for primary 20MHz: -8273 dBm – CCA for primary 40MHz: -7973 dBm – – – 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.
Submission 9 James Wang et. al., MediaTek
July 2014 doc.: IEEE 802.11-14/0880r1
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 PD 80M (=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:
a) b) c) d) e) 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 = PD 80M on 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 ≤ PD preceding the start of the TXOP 80M on the primary 40 MHz channel if the secondary channel was idle during an interval of PIFS immediately Transmit a 20 MHz mask PPDU at a power spectral density ≤ PD 80M on 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 Submission 10 James Wang et. al., MediaTek
2020/4/29 doc.: IEEE 802.11-14/0880r1 Transmission based on 80MHz Intended TX Channel Width
• Illustration of a device run EDCA transmission based on 80MHz intended TX channel width CCA levels (6 dB above current CCA level for 20MHz)
Data Rate vs Sensitivity for Different Channel Widths
400 350 40MHz 20MHz 80MHz 300 2nd 40 Busy 250 200 150 2nd 20 Busy 100 50 -85 -82 -79 -76 -73 -70 -67 -64 -61
Minimum Sensitivity (dBm)
-58 -55 -52 -49 0 -46 Submission 11 160MHz James Wang et. al., MediaTek
July 2014 doc.: IEEE 802.11-14/0880r1
Conclusions and Future Works
• • •
Current CCA levels and transmission rules
– 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
Submission 12 James Wang et. al., MediaTek
July 2014 doc.: IEEE 802.11-14/0880r1
References
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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
Submission Slide 13 James Wang et al, Mediatek