Doc.: IEEE 802.11-06/1711r0 Submission November 2006 Matthew Fischer (Broadcom)Slide 1 Serial...
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Transcript of Doc.: IEEE 802.11-06/1711r0 Submission November 2006 Matthew Fischer (Broadcom)Slide 1 Serial...
November 2006
Matthew Fischer (Broadcom)
Slide 1
doc.: IEEE 802.11-06/1711r0
Submission
Serial CTS-to-SELF (CTS2SELF) Proposal:20/40 MHz Coexistence in 2.4 GHz
Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11.
Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair <[email protected]> as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at <[email protected]>.
Date: 2006-12-11Authors:
Name Company Address Phone email
Matthew Fischer Broadcom [email protected]
Vinko Erceg
Jason Trachewsky
Broadcom
Broadcom
November 2006
Matthew Fischer (Broadcom)
Slide 2
doc.: IEEE 802.11-06/1711r0
Submission
Introduction
• For legacy devices to properly defer in 2.4 GHz spectrum in the presence of 40 MHz transmissions, two CTS-to-Self (CTS2SELF) transmissions can be employed by the 40 MHz devices.
• First transmission is on the primary channel followed by the second one on on the secondary channel after verifying that the secondary channel is idle.
• This solution solves the legacy deferral 20-40MHz coexistence issue without adding additional modes such as Duplicate CCK/DSSS transmission or mandating 25 MHz channel separation between primary and secondary channel.
November 2006
Matthew Fischer (Broadcom)
Slide 3
doc.: IEEE 802.11-06/1711r0
Submission
Serial CTS2SELF Principle
• The sequence of 20 MHz transmissions is performed as two CTS2SELF frame transmissions, the first of which is transmitted on the primary channel.
• Examination of the CCA condition on the secondary channel follows.
• If the secondary channel CCA indicates an IDLE channel for a period of PIFS time following the end of the transmission of the primary channel CTS2SELF transmission, then the 40 MHz device can send a second CTS2SELF frame on the secondary channel.
• These two transmissions serve to inform 20 MHz devices of the pending occupancy of 40 MHz spectrum. This is accomplished by providing, a duration of time that conveys to the 20 MHz only device, the amount of time that it must remain idle in order to allow the subsequent 40 MHz transmissions to proceed uninterrupted.
November 2006
Matthew Fischer (Broadcom)
Slide 4
doc.: IEEE 802.11-06/1711r0
Submission
Serial CTS2SELF Principle
• CTS2SELF may be sent using OFDM modulation in which case time-on-the-air is significantly shorter.
• CCK/DSSS modulation may be used on the secondary channel if the legacy device is 1 or 2 channel away.
November 2006
Matthew Fischer (Broadcom)
Slide 5
doc.: IEEE 802.11-06/1711r0
Submission
Serial CTS2SELF example 1
• A 40 MHz device’s 802.11 MAC function gains medium access and sends a pair of CTS2SELF frames in sequence, then follows those transmissions with a sequence of 40 MHz transmissions and receptions
• PIFS value depends on format of CTS2SELF, using 20 + 10 usec for DSSS/CCK format and 18 + 9 usec for ERP-OFDM format
C2
C2 = 20 MHz CTS2SELF frame transmission
= 40 MHz transmissions and/or receptions and/or idle gaps
CTS2SELF-receiving devices do not initiate transmissions during this time, but they may send response transmissions
Time reserved by Duration/ID field of CTS2SELF for 40 MHz transmissions
Secondary 20 MHz channel
Primary 20 MHz channel
C2
40 MHz device checks condition of secondary channel before transmitting
IFS
PIFS
PIFS time value based on format of CTS2SELF frame
Extent of Duration/ID NAV protection from the CTS2SELF frame
November 2006
Matthew Fischer (Broadcom)
Slide 6
doc.: IEEE 802.11-06/1711r0
Submission
Serial CTS2SELF example 2
• After transmitting the first CTS2SELF, the 40 MHz device finds that the secondary channel is BUSY, and therefore, decides to send only 20 MHz transmissions on the primary 20 MHz channel. The second CTS2SELF transmission is aborted.
C2
C2 = 20 MHz CTS2SELF frame transmission
= 20 MHz transmissions and/or receptions and/or idle gaps in the primary 20 MHz channel
CTS2SELF-receiving devices do not initiate transmissions during this time, but they may send response transmissions
Time reserved by Duration/ID field of CTS2SELF for 40 MHz transmissions
Secondary 20 MHz channel
Primary 20 MHz channel
40 MHz device checks condition of secondary channel before transmitting, and it is found to be BUSY
PIFS
PIFS time value based on format of CTS2SELF frame
Extent of Duration/ID NAV protection from the CTS2SELF frame
Unrelated activity
November 2006
Matthew Fischer (Broadcom)
Slide 7
doc.: IEEE 802.11-06/1711r0
Submission
Serial CTS2SELF example 3
• The 40 MHz device finds that the secondary channel is BUSY, and decides to delay the transmission of the second CTS2SELF frame
• Not efficient, but does avoid collisions
C2
C2 = 20 MHz CTS2SELF frame transmission
= 40 MHz transmissions and/or receptions and/or idle gaps
CTS2SELF-receiving devices do not initiate transmissions during this time, but they may send response transmissions
Time reserved by Duration/ID field of CTS2SELF for 40 MHz transmissions
Secondary 20 MHz channel
Primary 20 MHz channel
C2
40 MHz device checks condition of secondary channel before transmitting, and it is found to be BUSY
IFS
PIFS
PIFS time value based on format of CTS2SELF frame
Extent of Duration/ID NAV protection from the CTS2SELF frame
Unrelated activity
November 2006
Matthew Fischer (Broadcom)
Slide 8
doc.: IEEE 802.11-06/1711r0
Submission
Duplicate CKK/DSSS Disadvantages
• 1999-802.11b standard is not being followed because of the 20 MHz separation between the two CCK/DSSS channels. The standard recommendation is 25 MHz.
• It was not shown that the Duplicate CCK/DSSS mode actually works with legacy devices. It was not shown that the legacy devices will be OK with 20 MHz ACI and potential aliasing due to the 802.11b devices internal sampling at 11 MHz.
• Duplicate CCK/DSSS adds yet another mode to the standard that has to specified, discussed, implemented and tested while there were many LB84 comments to remove some of the modes.