Improving performance of LBT-enabled NB devices

 
Improving performance of LBT-enabled NB devices
 
Date:
 2024-03-12
 
March 2024
 
Ratnesh Kumbhkar, Intel
 
Slide 1
 
Authors:
 
Abstract
 
This submission explores the potential for performance improvement for
narrowband signals, such as Bluetooth, when using Listen-Before-Talk
(LBT) as the channel access mechanism.
 
Slide 2
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
Introduction
 
Bluetooth is planning to enable operation in the 5 and 6GHz bands. [1]
Listen-Before-Talk (LBT) has been suggested as a channel access
mechanism for Bluetooth in these bands. [2][3]
Wi-Fi channelization is typically well-defined within these spectrum bands.
This established channelization offers Bluetooth devices a unique
opportunity to improve their performance while using LBT.
 
Slide 3
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
Channelization
 
Slide 4
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
2MHz
Uses both UNII-3
and UNII-4
Uses both UNII-2c
and UNII-3
 
Slide 5
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
Bluetooth
:
LE 2M PHY
Gaming audio: 2 earbuds
1 earbud contains mic
1 earbud has inertial measurement unit
(IMU) sensor
Tx power: 14 dBm
ISO interval = 7.5ms
Max latency = 15ms (2×ISO)
Number of subevents, NSE = 2
1 main TX + 3 retry opportunities
Total 4 attempts
If packet is not transmitted in 4
attempts, packet is flushed, and it
results in a glitch
Number of channels = 62
Total hopping BW = 124MHz
Bi-directional traffic
 
Simulation parameters
 
*Wi-Fi traffic load = 60% all further slides
 
Wi-Fi
:
Tx power: 20 dBm at AP/STA
Single stream
One directional traffic
Traffic load: 60%
TXOP duration ≈ 5ms
Bandwidth = 80MHz
RTS →CTS →A-MPDU →BA
Transmission starts at time=3s
 
Channel model
:
AWGN channel with a breakpoint at 5 m
pathloss = 40.05 + 20log10(f/2.4) + 20log10(min(d, b)) + (d > b) * (35log10(d/b))
where d = distance, b = breakpoint = 5 m
 
Channelization
 
Slide 6
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
2MHz
Uses both UNII-3
and UNII-4
Uses both UNII-2c
and UNII-3
 
Bluetooth LE transmission with LBT
 
Slide 7
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
NSE = 2, Number of subevents in a connection interval
FT = 2, Flush timeout: Number of connection interval after which packet is discarded
Total 4 attempts to send the packet
 
LBT with uniform frequency hopping
 
Slide 8
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
Significant number of glitches observed
in Bluetooth audio due to transmission
deferral to Wi-Fi.
 
Impact of Bluetooth interference
Latency for Wi-Fi 2 increases.
No significant impact on Wi-Fi 1 and Wi-Fi 3. The latency
seen in the figure is due to mutual deferral.
 
Baseline performance for Wi-Fi 2
without any interference
 
Wi-Fi transmissions
start at 3s mark
 
Prioritization of non-overlapping channel
 
In the final attempt to send the packet, the
device hops to one of the non-overlapping
channels (i.e., channels 1-5 and 56-62).
 
Why not prioritize these channels from the
first attempt? –
These channels become congested very quickly
by the BT devices. Not scalable.
Keeps the opportunity open for the overlapped
channels to be used.
 
Slide 9
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
LBT with channel prioritization
 
Slide 10
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
Bluetooth glitches can be significantly reduced with minimal
impact on Wi-Fi latency compared to regular LBT.
 
Wi-Fi latency results remain
almost same with and without
channel prioritization.
 
Suffix “-pri” indicates use of
prioritized channel by Bluetooth.
 
UNII-5 in FCC
 
In the FCC regulatory domain, the 5925 MHz to 5945 MHz spectrum,
which is not utilized by Wi-Fi in the UNII-5, could potentially be available
for Bluetooth use.
By applying the insights gained from our simulations, it could be beneficial
to implement a similar channel prioritization strategy in the UNII-5 band
as well.
 
Slide 11
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
Summary
 
By giving priority to any non-overlapping channels that may be available in
the UNII-3 band (or UNII-5 in FCC) during the final attempts of a
Bluetooth packet transmission, the number of glitches can be significantly
minimized without causing any significant impact on Wi-Fi latency
compared to regular LBT.
 
Slide 12
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
References
 
1.
https://www.bluetooth.com/specifications/specifications-in-development/
2.
11-24-0007-00-coex-proposal-for-bluetooth-and-wi-fi-coexistence-in-5-and-6ghz
3.
11-24-0122-00-coex-bluetooth-isochronous-audio-with-lbt
 
Slide 13
 
Ratnesh Kumbhkar, Intel
 
March 2024
 
BACKUP
 
 
March 2024
 
Ratnesh Kumbhkar, Intel
 
Slide 14
 
Baseline Wi-Fi performance
 
Slide 15
 
Ratnesh Kumbhkar, Intel
 
March 2024
Slide Note

doc.: IEEE 802.11-24/0521r0

March 2024

Ratnesh Kumbhkar, Intel

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This submission delves into optimizing the performance of narrowband signals like Bluetooth by utilizing Listen-Before-Talk (LBT) for channel access in the 5 and 6 GHz frequency bands. The study explores the potential advantages for Bluetooth devices in improving efficiency and reliability through LBT implementation alongside Wi-Fi channelization in these spectrum ranges.

  • Bluetooth
  • Performance Improvement
  • LBT
  • Channel Access
  • Wi-Fi

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  1. March 2024 doc.: IEEE 802.11-24/0521r0 Improving performance of LBT-enabled NB devices Date: 2024-03-12 Authors: Name Ratnesh Kumbhkar Affiliations Intel Corporation Address Santa Clara, USA Phone email ratnesh.kumbhkar@intel.com Submission Slide 1 Ratnesh Kumbhkar, Intel

  2. March 2024 doc.: IEEE 802.11-24/0521r0 Abstract This submission explores the potential for performance improvement for narrowband signals, such as Bluetooth, when using Listen-Before-Talk (LBT) as the channel access mechanism. Submission Slide 2 Ratnesh Kumbhkar, Intel

  3. March 2024 doc.: IEEE 802.11-24/0521r0 Introduction Bluetooth is planning to enable operation in the 5 and 6GHz bands. [1] Listen-Before-Talk (LBT) has been suggested as a channel access mechanism for Bluetooth in these bands. [2][3] Wi-Fi channelization is typically well-defined within these spectrum bands. This established channelization offers Bluetooth devices a unique opportunity to improve their performance while using LBT. Submission Slide 3 Ratnesh Kumbhkar, Intel

  4. March 2024 doc.: IEEE 802.11-24/0521r0 Channelization Uses both UNII-2c and UNII-3 Uses both UNII-3 and UNII-4 Wi-Fi channels completely within UNII-3 CH 149 to CH 165 CH 144 CH 169 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 1 2 3 4 5 6 7 8 9 10 UNII-3, 5725-5850 MHz 2MHz Submission Slide 4 Ratnesh Kumbhkar, Intel

  5. March 2024 doc.: IEEE 802.11-24/0521r0 Simulation parameters Wi-Fi: Bluetooth: Tx power: 20 dBm at AP/STA Single stream One directional traffic Traffic load: 60% TXOP duration 5ms Bandwidth = 80MHz RTS CTS A-MPDU BA Transmission starts at time=3s LE 2M PHY Gaming audio: 2 earbuds 1 earbud contains mic 1 earbud has inertial measurement unit (IMU) sensor Tx power: 14 dBm ISO interval = 7.5ms Max latency = 15ms (2 ISO) Number of subevents, NSE = 2 1 main TX + 3 retry opportunities Total 4 attempts If packet is not transmitted in 4 attempts, packet is flushed, and it results in a glitch Number of channels = 62 Total hopping BW = 124MHz Bi-directional traffic *Wi-Fi traffic load = 60% all further slides 20 MHz 80 MHz Wi-Fi3 Wi-Fi1 Wi-Fi2 Channel model: AWGN channel with a breakpoint at 5 m pathloss = 40.05 + 20log10(f/2.4) + 20log10(min(d, b)) + (d > b) * (35log10(d/b)) where d = distance, b = breakpoint = 5 m 5835 5735 5815 5850 5726 Bluetooth BW = 124 MHz Submission Slide 5 Ratnesh Kumbhkar, Intel

  6. March 2024 doc.: IEEE 802.11-24/0521r0 Channelization Uses both UNII-2c and UNII-3 Uses both UNII-3 and UNII-4 Wi-Fi 2 Wi-Fi 1 and Wi-Fi 3 CH 144 CH 155, 80MHz CH 165, 20MHz CH 169 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 1 2 3 4 5 6 7 8 9 10 UNII-3, 5725-5850 MHz 2MHz Submission Slide 6 Ratnesh Kumbhkar, Intel

  7. March 2024 doc.: IEEE 802.11-24/0521r0 Bluetooth LE transmission with LBT CCA 360 s 360 s 360 s 360 s Central P-1 172 s 172 s P-2 360 s 360 s Retrying transmission f1 f2 f3 f4 Idle period 3.946ms Connection interval = 7.5ms NSE = 2, Number of subevents in a connection interval FT = 2, Flush timeout: Number of connection interval after which packet is discarded Total 4 attempts to send the packet Submission Slide 7 Ratnesh Kumbhkar, Intel

  8. March 2024 doc.: IEEE 802.11-24/0521r0 LBT with uniform frequency hopping Baseline performance for Wi-Fi 2 without any interference Wi-Fi transmissions start at 3s mark Impact of Bluetooth interference Latency for Wi-Fi 2 increases. No significant impact on Wi-Fi 1 and Wi-Fi 3. The latency seen in the figure is due to mutual deferral. Significant number of glitches observed in Bluetooth audio due to transmission deferral to Wi-Fi. Submission Slide 8 Ratnesh Kumbhkar, Intel

  9. March 2024 doc.: IEEE 802.11-24/0521r0 Prioritization of non-overlapping channel In the final attempt to send the packet, the device hops to one of the non-overlapping channels (i.e., channels 1-5 and 56-62). Why not prioritize these channels from the first attempt? These channels become congested very quickly by the BT devices. Not scalable. Keeps the opportunity open for the overlapped channels to be used. Submission Slide 9 Ratnesh Kumbhkar, Intel

  10. March 2024 doc.: IEEE 802.11-24/0521r0 LBT with channel prioritization Wi-Fi latency results remain almost same with and without channel prioritization. Suffix -pri indicates use of prioritized channel by Bluetooth. Bluetooth glitches can be significantly reduced with minimal impact on Wi-Fi latency compared to regular LBT. Submission Slide 10 Ratnesh Kumbhkar, Intel

  11. March 2024 doc.: IEEE 802.11-24/0521r0 UNII-5 in FCC In the FCC regulatory domain, the 5925 MHz to 5945 MHz spectrum, which is not utilized by Wi-Fi in the UNII-5, could potentially be available for Bluetooth use. By applying the insights gained from our simulations, it could be beneficial to implement a similar channel prioritization strategy in the UNII-5 band as well. Submission Slide 11 Ratnesh Kumbhkar, Intel

  12. March 2024 doc.: IEEE 802.11-24/0521r0 Summary By giving priority to any non-overlapping channels that may be available in the UNII-3 band (or UNII-5 in FCC) during the final attempts of a Bluetooth packet transmission, the number of glitches can be significantly minimized without causing any significant impact on Wi-Fi latency compared to regular LBT. Submission Slide 12 Ratnesh Kumbhkar, Intel

  13. March 2024 doc.: IEEE 802.11-24/0521r0 References 1. 2. 3. https://www.bluetooth.com/specifications/specifications-in-development/ 11-24-0007-00-coex-proposal-for-bluetooth-and-wi-fi-coexistence-in-5-and-6ghz 11-24-0122-00-coex-bluetooth-isochronous-audio-with-lbt Submission Slide 13 Ratnesh Kumbhkar, Intel

  14. March 2024 doc.: IEEE 802.11-24/0521r0 BACKUP Submission Slide 14 Ratnesh Kumbhkar, Intel

  15. March 2024 doc.: IEEE 802.11-24/0521r0 Baseline Wi-Fi performance Submission Slide 15 Ratnesh Kumbhkar, Intel

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