doc.: ieee 802.11-10/0231r3 submission march 2010 john r. barr, jrbarr, ltd. & nictslide 1...
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doc.: IEEE 802.11-10/0231r3
Submission
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 1
Efficient Methods for Coexistence with Other 60GHz Systems
Date: 2010-03-16
Authors:
doc.: IEEE 802.11-10/0231r3
Submission
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 2
Abstract
Overview of coexistence requirements for 802.11ad and suggestions for efficient methods for satisfying those requirements.
doc.: IEEE 802.11-10/0231r3
Submission
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 3
Outline
• Coexistence Requirements
• Assumptions
• Scanning for Existence of other 60GHz Systems
• Beacons to Prevent Interference by IEEE 802.15.3c Systems
• Straw Poll Questions
doc.: IEEE 802.11-10/0231r3
Submission
March 2010
John R. Barr, JRBarr, Ltd. & NiCT
TGad Coexistence Requirements
• From the TGad PAR:– It is in the best interest of users and the industry to strive for a
level of coexistence between wireless systems. VHT will investigate coexistence with other systems in the 60 GHz band.• One approach will be to investigate a common PHY between VHT
and 802.15.3c, and adopt if feasible.
• Another approach is a common coexistence mechanism that may be used by other 60 GHz systems
• From TGad Functional Requirements:– [Req08] The system is required to support mechanisms that enable
coexistence with other systems in the band including IEEE 802.15.3c systems.
Slide 4
doc.: IEEE 802.11-10/0231r3
Submission
Evaluation Criteria• 42.3 Coexistence for FR Section 2.3 (Req08)
– Proposers shall describe mechanisms by which coexistence of an 802.11ad AP and other 60 GHz systems and standards in the band is covered by the proposal. This should include coexistence with IEEE 802.15.3c. Those mechanisms may include energy detection, preamble detection or the use of some universal mode to communicate between the 802.11ad AP and the devices of the other 60GHz systems and standards. Once an interferer is detected, the 802.11ad AP should avoid interference through the use of beamforming, use of alternate available channel or other means to coexist. If the 802.11ad AP and the devices of the other 60GHz systems and standards operate co-channel, the performance of the coexistence mechanism can be measured by the effective throughput of the device in the presence of the interferer operating within the band.
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 5
doc.: IEEE 802.11-10/0231r3
Submission
60 GHz Coexistence Assumptions• TGad will use same channel frequencies as 802.15.3c,
ECMA-387, and WirelessHD; and avoid using a channel that is “occupied”.
• 802.15.3c systems using a channel will broadcast superframe beacons/sync frames using CMS (Common Mode Signaling) at least once every 66 mS identifying the piconet and when channel will be used during each superframe.
• 802.15.3c, ECMA-387, and WirelessHD devices transmit without LBT in a variety of modulation modes when CTA (Channel Time Allocation) designated for their use. (TDMA MAC)
• Other systems may use beamforming or other methods to limit interference from other 60GHz devices.
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 6
doc.: IEEE 802.11-10/0231r3
Submission
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 7
Scanning for Existence of Other 60 GHz Systems
• Prior to establishing a new BSS in one of the available 60 GHz channels, the initiator of the action (e.g., AP) needs to determine whether other 60 GHz systems are currently operating on any of the channels and which channel is best suited for handling a new BSS.
• Existing specifications for other 60 GHz systems all include the concept of a beacon transmitted at a consistent rate to inform devices of the existence of that 60 GHz system. (802.15.3c, ECMA-387, & WirelessHD).
• Detecting these beacons or significant energy in the channel is an indicator of the channel being occupied.
doc.: IEEE 802.11-10/0231r3
Submission
ECMA-387 Beacons
• Regular beacon period with beacons from all devices using the channel.
• Three types of devices that all use same signal frequency (1.728 Gsps) and symbol duration (0.5787 ns).
• Maximum superframe length is 16 mS.
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 8
doc.: IEEE 802.11-10/0231r3
Submission
IEEE 802.15.3c Beacons
• Beacon or sync frame sent by piconet controller once per superframe.
• Maximum superframe length is 66 mS.
• Common Mode Signaling (CMS) used for beacon or sync frame.
• CMS has a chip rate of 1760 Mchip/s and a chip duration of 0.568 ns.
• Sync frames may be sent by other devices in the piconet to inform other devices of channel activity.
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 9
doc.: IEEE 802.11-10/0231r3
Submission
WirelessHD Beacons
• Current version of WirelessHD was established prior to finalization of IEEE 802.15.3c.
• The AV OFDM mode defined in IEEE 802.15.3c was submitted by SiBEAM.
• At some point, the WirelessHD specifications may be updated to conform to the IEEE 802.15.3c standard.
• If future WirelessHD specifications conform to the IEEE 802.15.3c standard, they will transmit and detect CMS sync frames to enable coexistence with other 60 GHz systems.
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 10
doc.: IEEE 802.11-10/0231r3
Submission
IEEE 802.15.3c Coexistence Model
• Developed to handle multiple PHY modes with an efficient mechanism for coexistence in the multi-channel 60GHz spectrum.
• Approved by sponsor ballot with a broad cross section of IEEE 802 members.
• Primary component for consideration by TGad is transmission/reception of beacons/sync frames using CMS.– Beacon/sync frame will be sent at least once every 66 mS
– Beacons/sync frames sent by other 60 GHz systems will be received during channel scan periods and will prevent establishment of another piconet in the same channel.
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 11
doc.: IEEE 802.11-10/0231r3
Submission
Recommended Text
• Add sub clause to 11.9.7 (or other appropriate clause) regarding 60 GHz DFS:– Before a 60GHz STA starts a BSS in one of the 60GHz channels it
shall perform a “60GHz scan operation” of the channel. If the “60GHz scan operation” indicates the channel is occupied, an alternate channel should be used for the BSS. If no 60GHz channel is free of other systems, the 60GHz STA may select a channel and enable other methods of coexistence. “60GHz scan operation” is currently TBD.
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 12
doc.: IEEE 802.11-10/0231r3
Submission
Protection from other 60GHz Systems
• Other 60GHz systems may also be attempting to utilized one or more of the available 60GHz channels, and some of these systems will avoid using a 60GHz channel occupied by another 60GHz system.
• However, there must be some indication provided by an 802.11 60GHz BSS that the channel is being used that can be detected by the other 60GHz system.
• Sync frames sent using CMS as defined in IEEE 802.15.3c is an accepted method:– All conforming IEEE 802.15.3c systems will avoid channels with
a CMS sync frame
– Future WirelessHD systems may also recognize CMS sync frames and avoid those channels
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 13
doc.: IEEE 802.11-10/0231r3
Submission
IEEE 802.15.3c CMS Sync Frame
• CMS defined in clause 12.1.12 of IEEE 802.15.3c-2009– 1760 Mchips/s modulated with π/2 BPSK/precoded (G)MSK as
specified in 12.2.2.5.1.
– A sync frame for 802.11 60GHz systems could be a predefined sequence of symbols that would notify 802.15.3c systems that the channel is occupied and not available for use by other systems.
• An 802.11 60GHz CMS sync frame would need to be generated by the owner of a 60GHz BSS on a regular basis for detection by other 60GHz systems during channel scanning periods.
• Adoption of this portion of the IEEE 802.15.3c coexistence policy would drive similar adoption by other 60GHz systems.
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 14
doc.: IEEE 802.11-10/0231r3
Submission
IEEE 802.15.3c Sync Frame Overhead
• Sync Frame Consists of: (references to IEEE 802.15.3c)– Preamble – 944 octet fixed sequence as defined in 12.1.12.4
– CMS PHY Header – 5 octet fixed values as defined in 12.1.12.6
– MAC Header – 10+2(HCS) octet fixed values as defined in 7.2
– MAC Frame Body: Defined in 7.3.6• Syncronization Parameters – 4 octet fixed values
• CTA – 4 octet fixed values
– FCS: 32-bit CRC equivalent to ANSI X3.66-1979 (See 7.2.7.6 in IEEE 802.15.3-2003)
– RS Parity – 16 octets fixed
• Total Octets = 944+(32*64)=2,992 (about 3 μS)
• Sync Frame Overhead for 66mS repetition is 0.0045%
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 15
doc.: IEEE 802.11-10/0231r3
Submission
Recommended Text• Add a clause to section 11 regarding 60GHz coexistence
methods:– The 60GHz AP shall protect the BSS from other 60GHz systems
by transmitting CMS sync frames according to the dot11SyncFramePeriod parameter of the STA.
– STAs in an IBSS shall protect the BSS from other 60GHz systems by transmitting CMS sync frames according to the dot11SyncFramePeriod parameter of the STA and following the rules for beacon generation in an IBSS (11.1.2.2).
• Add a clause to section 7.2.3 defining the 60GHz Sync Frame format:– Similar to clause 7.3.6 with only one CTA block field hard coded
to cover the entire superframe duration. Can also include clauses defining exact symbol sequence required for fixed sync frame definition.
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 16
doc.: IEEE 802.11-10/0231r3
Submission
Conclusion
• Adding 60GHz channel scanning and sync frame generation will provide for simple coexistence methods that should eventually be adopted by all other 60GHz systems.
• Use of pre-coded symbol sequences reduces impact on MAC/PHY implementation of 1760 Mchips/s single carrier PHY mode for coexistence.
• Completely satisfies TGad PAR requirements for coexistence.
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 17
doc.: IEEE 802.11-10/0231r3
Submission
Straw Poll Questions
• Do you support inclusion of the technique,– pre-BSS establishment channel scanning for 60GHz BSS
as described in 10/0231r3 in the TGad draft amendment?
• Do you support inclusion of the technique,– CMS sync frame transmission for 60GHz APs
as described in 10/0231r3 in the TGad draft amendment?
• Do you support inclusion of the technique,– CMS sync frame transmission for IBSS STAs
as described in 10/0231r3 in the TGad draft amendment?
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 18
doc.: IEEE 802.11-10/0231r3
Submission
March 2010
John R. Barr, JRBarr, Ltd. & NiCTSlide 19
References• 11-09-0296-16-00ad-evaluation-methodology.doc
• 11-09-0228-05-00ad-functional-requirements.doc
• 11-08-0806-07-0vht-60-ghz-par-nescom-form-plus-5cs.doc
• 11-09-0568-00-00ad-response-to-802-15-3c.ppt
• 11-09-0370-02-00ad-common-mode-signaling-cms-for-intersystem-coexistence-enhancement.ppt
• 11-09-0372-01-00ad-tg3c-dev-sync-frame-transmission-for-adjacent-piconet-coexistence.ppt
• 11-09-0797-02-00ad-topology-considerations-on-contention-based-directional-mac-simulation.ppt
• 11-09-0960-00-00ad-wirelesshd-coexistence.ppt
• IEEE Std 802.15.3c™-2009
• ECMA-387