1. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
1 September 2008
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Enhancements enabling Standby Coordinator]
Date Submitted: [1 Sept 2008]
Source: [Ryoji Ono] Company [Mitsubishi Electric Corp.]
[Hirohito Nishiyama] Company [Mitsubishi Electric Corp.]
[Tatsuji Munaka] Company [Mitsubishi Electric Corp.]
Address [5-1-1 Ofuna, Kamakura, Kanagawa, Japan]
Voice:[ ]
}.MitsubishiElectric.co.jp]
Re: [IEEE e group]
Abstract: Failure of coordinator is critical in IEEE network systems. Redundant system design should be available for manufacturing systems. We propose MAC enhancements enabling the failover to the standby coordinator in case of the failure of the coordinator.
Purpose: To propose enhancements for IEEE MAC protocol.
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
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka
<author>, <company>

2. Enhancements enabling Standby Coordinator
<month year>
doc.: IEEE <doc#>
1 September 2008
Enhancements enabling Standby Coordinator
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka
Mitsubishi Electric Corp.
1 Sep. 2008
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka
<author>, <company>

3. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
1 September 2008
Contents
Motivation and Goals
Overview of Proposed System
Issues
Proposed Super Frame Structure
Dual Beacon Scheme
Proposed Beacon Frame Structure
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka
<author>, <company>

4. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
1 September 2008
Motivation and Goals
Scalability, reliability, and latency are challenging issues in wireless deployment in manufacturing systems.
Failure of coordinator is critical in IEEE network systems. Redundant system design should be available for manufacturing systems.
There are two ways to achieve redundancy of coordinator; (a) Wired connected standby coordinator -> out-of-scope (b) Wireless standby coordinator
IEEE beacon mode fails to satisfy requirements for (b).
Beacons from two coordinators may collide.
No mean to resolve collision.
We propose a MAC that:
Enables failover to the standby coordinator within 1-2 superframe(s).
Avoids collision of the current and the standby coordinators.
Supplies way to negotiate to select coordinator.
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka
<author>, <company>

5. Proposed System – Overview (1)
<month year>
doc.: IEEE <doc#>
1 September 2008
Proposed System – Overview (1)
Network topology is star-topology.
There is one (current) coordinator, one standby coordinator and zero or more other devices (RFD, FFD).
coordinator and standby coordinator have different addresses.
Standby coordinator may take over the role of coordinator in case of failure of the current coordinator.
Standby coordinator sends a sub-beacon, an additional beacon frame to enable standby function, just after the (main) beacon.
When the standby coordinator detects a failure on the current coordinator, it utilizes the sub-beacon to trigger negotiation to select the coordinator for the next superframe.
Failure detection will be performed in the upper layers and is out-of-scope of this standard.
Selection can be carried out in ECFP (Extended CFP).
Negotiation (selection) will be performed in the upper layers and is out-of-scope of this standard.
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka
<author>, <company>

6. Proposed System – Overview (2)
<month year>
doc.: IEEE <doc#>
1 September 2008
Proposed System – Overview (2)
Coordinator-A
Coordinator-B
Coordinator-A
Coordinator-B A B A B
Coordinator
Beacon
Standby Coordinator
Sub-beacon
Devices (FFD or RFD)
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka
<author>, <company>

7. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
1 September 2008
Issues
When the standby coordinator tries to detect a failure of the coordinator by monitoring transmissions, it may incorrectly recognize a failure on the following conditions.
1) Transmission failure between the coordinator and the standby coordinator.
2) Failure of the standby coordinator, especially on its Rx.
If we assume the standby coordinator simply takes over the coordinator function, both the coordinators may send the beacon frames in the same time on the above conditions.
Our proposal;
adds timeslots to be used for negotiation to select a coordinator.
It ensures that the standby coordinator takes over the coordinator function only in case of actual failure.
adds sub-beacon sent by the standby coordinator.
It avoids collision of beacon from the current/standby coordinators.
It supplies GTS information for the negotiation timeslots.
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka
<author>, <company>

8. Proposed Super Frame Structure (1)
<month year>
doc.: IEEE <doc#>
1 September 2008
Proposed Super Frame Structure (1)
Dual beacons for current and standby coordinators.
ECFP to enable negotiation by upper layer protocol.
Super Frame
Super Frame
CAP
CFP
ECFP
CAP
CFP
ECFP Ba Bb Ba Bb
time
Beacons
from Coordinator-A
Beacons
from Coordinator-B
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka
<author>, <company>

9. Proposed Super Frame Structure (2)
1 September 2008
Proposed Super Frame Structure (2)
Superframe consists of fixed-size time slots and has several parts
Ba : Beacon frame for Coordinator-A
Bb : Beacon frame for Coordinator-B
(Current) coordinator sends main beacon frame.
Standby coordinator sends sub-beacon frame.
CAP：
CFP :
ECFP : Extended CFP used for negotiation to select coordinator.
Don't care on this proposal.
(can be compatible with IEEE Std )
CAP
CFP
ECFP Ba Bb
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka

10. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
1 September 2008
Dual Beacon Scheme
Two coordinators are statically allocated to one of two beacons (Ba, Bb).
Two types of beacon frames are defined – main beacon and sub-beacon.
Main beacon: Sent by (current) coordinator. Supplies GTS information for CFP and ECFP.
Sub-beacon: Sent by standby coordinator. Only supplies GTS information for ECFP.
Any other devices in the network use GTS information in sub-beacon in case that they fail to receive main beacon.
This enables the network to negotiate for coordinator switching on the failure of the coordinator.
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka
<author>, <company>

11. Usage Scenario – Normal Case
1 September 2008
Usage Scenario – Normal Case
Coordinator-A continues to be
the coordinator in the next superframe.
superframe
ECFP
ECFP
ECFP Ba Bb Ba Bb Ba Bb
Coordinator-A
no failure detected Ba Bb Ba Bb Ba Bb
Coordinator-B
Coordinator-B doesn’t
indicate coordinator’s failure.
No negotiation
No negotiation
No negotiation Ba Bb Ba Bb Ba Bb
Device Ba Bb Ba Bb Ba Bb
Device
Devices receive main beacon.
: main beacon
: sub beacon
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka

12. Usage Scenario – Coordinator Failure
1 September 2008
Usage Scenario – Coordinator Failure
superframe
Main beacon is not sent.
ECFP
ECFP
ECFP Ba Bb
Coordinator-A
Coordinator-B becomes
the coordinator in the next superframe.
Coordinator-B detects that
Coordinator-A is failed. Ba Bb Bb Bb
Coordinator-B
Coordinator-B indicates
coordinator’s failure.
No negotiation
Negotiation
No negotiation Ba Bb Bb Bb
Device Ba Bb Bb Bb
Device
Devices DON’T receive main beacon.
: main beacon
: sub beacon
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka

13. Usage Scenario – Incorrect Failure Detection
1 September 2008
Usage Scenario – Incorrect Failure Detection
Coordinator-A continues to be
the coordinator in the next superframe.
superframe
ECFP
ECFP
ECFP Ba Bb Ba Bb Ba Bb
Coordinator-A
Coordinator-B BELIEVES
that Coordinator-A is failed. Ba Bb Bb Bb
Coordinator-B
Coordinator-B indicates
coordinator’s failure.
No negotiation
Negotiation
Negotiation Ba Bb Ba Bb Ba Bb
Device Ba Bb Bb Bb
Device
Devices MAY or MAY NOT
receive main beacon.
: main beacon
: sub beacon
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka

14. Without negotiation ... 1 September 2008 superframe Ba Bb Ba Bb
Coordinator-A
Coordinator-B BELIEVES
that Coordinator-A is failed. Ba Bb Bb
Coordinator-B
Coordinator-B sends
main beacon.
Conflicts may happen in GTS. Ba Bb Ba Bb
Device
GTS information can be different. Ba Bb Bb
Device
Devices MAY or MAY NOT receive beacons.
: main beacon
: sub beacon
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka

15. Proposed Beacon Frame Format
1 September 2008
Proposed Beacon Frame Format
Coordinator Failure Detection: only applied for Sub-beacon.
GTS fields, Beacon Payload:
(main) contains information for both CFP and ECFP.
(sub) contains information only for ECFP.
MAC Frame Format
Octets: 2 1
4 or 10
0,5,6,10 or 14 2 k m n
0 or 1 2
Frame
Control
Sequence
Number
Addressing
fields
Auxiliary
Security
Header
Super frame
Specification
GTS
fields
Pending
address
fields
Beacon
Payload
Coordinator
Failure
Detection
FCS
Coordinator Failure Detection Field
Frame Control Field
Bits:
0-2 3 4 5 6
7-9
10-11
12-13
14-15
Bits:
1-7
Frame
Type
Security
Enabled
Frame
Pending
Ack
Request
PAN ID
Compression
Reserved
Dest.
Addressing
Mode
Frame
Version
Source
Addressing
Mode
Failure
Detection
Reserved
000:(Main)Beacon
001:Data
010:Acknowledgment
011:MAC command
100:Sub Beacon
:Reserved
0:Normal Status
1:Coordinator Failure Detection
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka

16. 1 September 2008
Thanks!
Ryoji Ono, Hirohito Nishiyama, Tatsuji Munaka