1. <January 2002>
doc.: IEEE <02/139r0>
Nov, 2008
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Resolution to comment #110,111]
Date Submitted: [Nov ]
Source: [Vered Bar]
Company: [Qualcomm]
Address: [QUALCOMM, Incorporated, 5775 Morehouse Drive, San Diego, CA 92121]
Voice: [], FAX: [],
Re: []
Abstract: [Comment resolutions.]
Purpose: [To be considered in IEEE c standard]
Notice: This document has been prepared to assist the IEEE P 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 acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P
Slide 1
Qualcomm
Chuck Brabenac, Intel Labs

2. Nov, 2008
Comment #110
sync frame is only mandated for PNC which is not providing a good enough solution for hidden nodes problem.
Commenter suggested Resolution:
add sync frame as optional for dev to allow for faster scan of PNC candidate and better interference mitigation between neighboring piconets.
Slide 2
Qualcomm

3. Current Common Mode Sync Frame Rules
Nov, 2008
Current Common Mode Sync Frame Rules
In order to promote coexistence among DEVs using different PHYs, the following MAC rules have defined.
An AV PNC-capable DEV, when operating as a PNC, shall transmit an AV beacon and a CMS sync frame in every superframe.
An HSI PNC-capable DEV, when operating as a PNC, shall transmit either an HSI beacon and a CMS sync frame in every superframe.
An AV PNC-capable DEV shall be able to receive the CMS sync frame and command frames.
An HSI PNC-capable DEV shall be able to receive the CMS sync frame and command frames.
The current c procedure does not provide adequate answer to the hidden node problem and to maintaining lasting synchronization and avoiding interference between independent networks.
Qualcomm

4. Hidden node Interference Illustration
Nov, 2008
Hidden node Interference Illustration
There is not enough link margin for the PNC1 to PNC2 link for common mode. No LOS link because of metal object blocking
When DEV1 is transmitting, the interference at DEV2 limits the SNR to 2dB, much lower than the required 10dB.
The PNC2-DEV2 link has additional 13dB link margin for ~3Gbps data rate. PNC2 is unaware of DEV1 interference, except for throughput drop due to interference.
There is over 26dB link margin for the PNC1 to PNC2 link for common mode.

5. Hidden node Interference Suggested Resolution
Nov, 2008
Hidden node Interference Suggested Resolution
In the case of c device, each device capable of sending sync frames is required to send a synchronization packet at the first time its get allocation to transmit in a superfarame, every pre-defined number of superframes for pre-define directions.
Qualcomm

6. Virtually Dependent Piconets
Nov, 2008
Virtually Dependent Piconets
The drawing illustrates “virtually dependent piconets”, which are synchronized.
By maintaining synchronization between neighbouring piconets, interference remains constant in the time domain and can be masked.
Even though PNC2 is not seeing PNC1 sync frame, so it can not create a dependent piconet, it is using DEV 1C and DEV 2C synchronization packets to synchronize to PNC1 timing and forming a virtually dependent piconet.
PNC2 schedules data transfers for devices members in its on piconet and avoid interference between the two piconets.
Slide 6
Qualcomm

7. Nov, 2008
Conclusion
DEV Sync frames increase the chance for overcoming hidden node problem.
Make sync frame optional for DEV
Device publishes sync frame transmit capability
PNC controls the sync frame distribution by setting the number of superframes between sync. Frames and defining directions, if that DEV is capable of sync frame transmission
Virtually dependent piconents enables masking of interference time allocation by neighboring piconet devices and avoiding throughput hit.
Qualcomm

8. Comment #111 Sync frame is not defined for DEV.
Nov, 2008
Comment #111
Sync frame is not defined for DEV.
Commenter suggested Resolution:
add sync frame as optional for dev and define rules for new Sync_frame_capability_IE and for Sync_frame_control IE .
Slide 8
Qualcomm

9. Suggested optional Sync. Frame Transmission function
Nov, 2008
Suggested optional Sync. Frame Transmission function
Sync frame Support:
DEV reports sync frame transmit capability during association
PNC controls the sync frame distribution by setting the number of superframes between sync. frames and defining directions using Sync_frame_frequency IE in a Announce command, if that DEV is capable of sync frame transmission
Sync frame scheduling:
If requested by the PNC, a DEV sends a sync frame at the first time its get CTA to transmit in a superframe, every pre-defined number of superframes for pre-define directions as indicated in Sync_frame_frequency IE
Qualcomm

10. Suggested Changes to D02 Capability_IE (Section 7.4.11)
Nov, 2008
Suggested Changes to D02
Capability_IE (Section )
Add a new bit assignment in DEV capabilities field
Bit 36: Sync_frame_capable
Sync_frame_frequency_IE
Add Section “Sync Frame Frequency IE”
Sync frame frequency field indicates the number of superframes between two Sync frame transmission requested by PNC
Sync frame direction bit indicates if the Sync frame transmission is omni or directional
If directional, sync frame direction is round robin of DEV available directions
Octets:1 1
Reserved
(2 bits)
Sync frame direction
Sync frame frequency
(5 bits)
Length
Element ID
Qualcomm

11. Suggested Changes to D02 (cont.)
Nov, 2008
Add new subclause 8.17 “Sync. Frame Transmission and Virtually Dependent Piconets”
“Sync. Frame Transmission is an optional function that mitigates co-channel interference due to hidden PNC node. It also provides a method to obtain synchronization among independent piconets. To use Sync. Frame Transmission, a DEV needs to report sync frame transmit capability to PNC during association procedure.
PNC controls the sync frame distribution of a DEV by setting the number of superframes between sync. frames using Sync_frame_frequency IE, as defined in , in a Announce command, if that DEV is capable of sync frame transmission.
Requested by the PNC, a DEV sends a sync frame at the first time its get CTA to transmit in a superframe, every pre-defined number of superframes for pre-define directions as indicated in Sync_frame_frequency IE.
The sync frame shall be transmitted using CMR
Device can use either data or Imp-ACK allocations for Sync. frame transmission
A scanning DEV, upon receiving a Sync. Frame, may utilize the embedded information to obtain network synchronization and mitigate interference.
Even though one PNC is not seeing the other PNC sync frame, it can use the Sync. Frames it receives from devices members of this other PNC, to synchronize to PNC timing and forming a “virtually dependent piconet”. This “virtually dependent PNC” may then schedule data transfers for devices members in its own piconet and avoid interference between the two piconets. ”
Qualcomm

12. Suggested Changes to D02 (cont.)
Nov, 2008
Suggested Changes to D02 (cont.)
Add text to Requirements for mmWave PNCs:
All DEV capable of sync frame transmission shall transmit a sync frame at the first time its get CTA to transmit in a superframe, every pre-defined number of superframes for pre-define directions as indicated in Sync_frame_frequency IE

13. Nov, 2008
Backup

14. Annex 1: example of Sync Frame exchange procedure
Nov, 2008
Annex 1: example of Sync Frame exchange procedure
CAP
CTA for
DEV1A to DEV1C
CTA for
PNC1 to DEV1C
CTA for
DEV 1A to DEV1B
Beacon
DEV1A to DEV1C
Sync Frame
SIFS
Normal data
Normal data
Sync Frame
SIFS
DEV1C to DEV1A
ACK policy set to Imp-ACK
When the first time the CTA for DEV1A to transmit to DEV1C arrives, DEV1A sends a Sync Frame with ACK policy set to Imp-ACK
DEV1C, upon receiving the Sync Frame, waits for SIFS and replies back Sync Frame to extend the possible coverage range of Sync Frame
After the Sync frame exchange, normal frame transmission carries on
Slide 14
Qualcomm