1. July 2006
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [BOP Location Considerations and Beacon Scheduling for Backward Compatibility to Legacy IEEE Devices]
Date Submitted: [20 July, 2006]
Source: [Ho-In Jeon (1) and Yongsik Shin (2)]
Company: [Dept. Electronic Engineering, Kyung-Won University (KWU) and HNTC of IITA (1), SKtelecom (2)]
Address: [San 65, Bok-Jung-Dong, Sung-Nam-Shi, Kyung-Gi-Do, Republic of Korea]
Voice 1: [ ], Voice 2:[ ] FAX: [ ],
Re: [This work has been supported by HNRC of IITA, Korea.]
Abstract: [This document proposes a routing algorithm for efficient real-time network address allocation mechanisms based on LAA concept in a Mesh Network.]
Purpose: [Technical Contributions on the IEEE 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
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

2. July 2006
BOP Location Considerations and Beacon Scheduling for Backward Compatibility to Legacy IEEE Devices
Ho-In Jeon (1), and Yongsik Shin (2)
(1) Kyung-Won University, HNRC of IITA
Republic of Korea, and
(2) SKtelecom
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

3. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
July 2006
Contents
Issues of Mesh Networks
A Mesh Network Architecture
Beacon Scheduling Fundamentals with BOP Concept
Position Change of BOP for the supportability of Legacy Devices
Efficiency Analysis in Data Communication
Conclusion
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)
<author>, <company>

4. Issues of Mesh Networks
<month year>
doc.: IEEE <doc#>
July 2006
Issues of Mesh Networks
Multiple Beacons in One Superframe
Beacon Scheduling for Beacon Collision Avoidance
Efficient Real-Time Short Address Allocation Algorithms
Routing Algorithm: Proactive or Reactive
Power-Efficient Operation Mode
Support of Time-Critical or Delay-Sensitive Applications
Resource Reservation for Data Transmission
Hidden Node and Exposed Node Problems
Mobility Support for Intra- and Inter-PAN
Backward Compatibility to Legacy IEEE Devices
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)
<author>, <company>

5. Operating Principles of Mesh Networks
July 2006
Operating Principles of Mesh Networks
The first device becomes MPC after passive and active scan.
Devices are associated to the MPC sequentially, one by one.
When an association request is granted by multiple nodes, the new node decides to associate with the node which has lower depth.
When depth information is the same, he decides to associate with the node which transmits his beacon earlier than others.
The relation between parent and children are characterized by association request and response.
My parent and children are my neighbors.
All devices I can hear are my neighbors. 2 1 5
MPC 4 3 6
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

6. Multiple Beacons in One Superframe
July 2006
Multiple Beacons in One Superframe
BOP (Beacon-Only
Period)
Beacon
Deep Sleep
CAP
CFP
Deep Sleep
Superframe
#m-1 #m
#m+1
Beacons
Deep Sleep
Deep Sleep
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

7. A Mesh Architecture and Beacon Scheduling
July 2006
A Mesh Architecture and Beacon Scheduling
Every node sends his beacon with beacon payload containing its depth information, its Beacon Transmission Time Slot (BTTS), and BTTS’s occupied by his neighbors and neighbor’s neighbors.
The first beacon slot can be used only by the MPC for the protection of PAN’s basic information.
Solid blue line represents the Parent-Child relations based on associations, while red line represents directly reachable.
Every mesh device shall transmit his beacon during the BOP (Beacon-Only Period) at the BTTS scheduled in a distributed manner. 2 1
MPC
BOP
CAP 3 1 2 3 1
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

8. Beacon Payload Info. for Beacon Scheduling
July 2006
Beacon Payload Info. for Beacon Scheduling
When a node sends his beacon with beacon payload shown below, the receiver nodes can obtain the information of the BTTS occupied by its neighbors and its neighbor’s neighbors.
The beacon scheduling is performed by choosing the smallest time slot of the BOP slots which avoids the time slots occupied by neighbors and its neighbor’s neighbors.
Name
Value
My Depth
Integer (16 bits)
My BTTS (BeaconTxTimeSlot)
Integer (8 bits)
Neighbors’ BTTS
Integer (64 bits, bit map)
<Information contained in the beacon payload>
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

9. July 2006
Beacon Scheduling 14 16 17 12 18 13 11 15 19 2 5 9 20 1
PNC 6 8 10 4 3 7
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

10. Beacon Scheduling Deep Sleep July 2006 Node 17 Neighbor Nodes
11,13,14,16
Neighbor's
2,5,9,12
Depth 3
Beacon Time Slots
to Avoid
1,2,3,4,
5,7,9,10
My BTTS 6 14 16 17 12 13 11 15 2 5 9 1 6
PNC 8 4 10 3 7
BOP
CAP
CFP
Deep Sleep
BOP 1 2 3 4 5 6 7 8 9 13 1 2 10 12 14 15 11 10 16 17 16
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

11. Beacon Scheduling Performed!
July 2006
Beacon Scheduling Performed! 4 14 2 6 16 3 17 12 18 11 13 7 10 11 3 6 15 19 2 5 2 9 10 5 1 9 20 1 6 2
MPC 4 6 8 4 10 3 7 8 3 7
BOP
CAP
CFP
Deep Sleep
BOP 1 2 3 4 5 6 7 8 9 13 18 1 2 10 12 14 15 11 20 10 16 19 17 16
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

12. Concerns about Beacon Scheduling
July 2006
Concerns about Beacon Scheduling
Efficiency in data communications
The size of the BOP (Beacon-Only Period) may become too large as the mesh network grows having many nodes, and thus the efficiency in data communication can be very low.
Power consumption may be too much.
Backward compatibility to legacy IEEE devices
Legacy IEEE devices listen his parent’s beacon and perform the CSMA/CA immediately.
During the BOP, the legacy IEEE devices may hear many other beacons which will not confuse it.
It will wait until BOP end in order to send his data.
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

13. Efficiency in Data Communication
July 2006
Efficiency in Data Communication
The efficiency of the data communications is defined as the ratio of the period where actual data can be effectively transferred to the Superframe Duration. (See )
The legacy IEEE device has efficiency of 99.6%.
Mesh network with 64 beacons transmitted without beacon scheduling algorithm having SO = 3 and BO = 4 provides 33.3%.
Mesh network with 64 beacons transmitted without beacon scheduling algorithm having SO = 4 and BO = 5 provides 66.7%.
Mesh network with 32 beacons transmitted without beacon scheduling algorithm having SO = 4 and BO = 5 provides 87.5%.
Mesh network with 16 beacons transmitted without beacon scheduling algorithm having SO = 4 and BO = 5 provides 93.75%.
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

14. 802.15.4 Superframe Structure and Timing
July 2006
Superframe Structure and Timing
Efficiency = 99.6%
Beacon
Beacon
CAP
CFP
GTS #1
GTS #2
Inactive 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2
SlotD (Slot Duration)
SlotD = aBaseSlotDuration × 2SO [symbols] = 60 × 2SO [symbols] = 0.96 × 2SO [msec]
SD (Superframe Duration)
SD = aBaseSuperframeDuration * 2SO [symbols] = 960 * 2SO [symbols] = * 2SO [msec]
BI (Beacon Interval) = aBaseSuperframeDuration * 2BO [symbols] = 960 * 2BO [symbols] = * 2BO [msec]
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

15. Superframe Timing with SO = 3 and BO = 4
July 2006
Superframe Timing with SO = 3 and BO = 4
BOP
Efficiency = 33.3% when BTTS = 64
aUnitBackoffPeriod = 320 usec B1 B2 B3
……….
B64
Inactive B1
CAP
0.192[msec]: Rx-Tx Turnaround Time
0.896[msec]
1.280[msec]
Duration of BOP with 64 Beacons
= x 64 = [msec]
Duration of CAP with 64 Beacons
= = [msec]
SD (Superframe Duration) = aBaseSuperframeDuration * 2SO [symbols] = * 2SO [msec] = [msec]
BI (Beacon Interval) = aBaseSuperframeDuration * 2BO [symbols] = 960 * 2BO [symbols] = * 2BO [msec] = [msec]
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

16. Superframe Timing with SO = 4 and BO = 5
July 2006
Superframe Timing with SO = 4 and BO = 5
BOP
Efficiency = 66.7% when BTTS = 64
aUnitBackoffPeriod = 320 usec B1 B2 B3
……….
B64
Inactive B1
CAP
0.192[msec]: Rx-Tx Turnaround Time
0.896[msec]
1.280[msec]
Duration of BOP with 64 Beacons
= x 64 = [msec]
Duration of CAP with 64 Beacons
= = [msec]
SD (Superframe Duration) = aBaseSuperframeDuration * 2SO [symbols] = * 2SO [msec] = [msec]
BI (Beacon Interval) = aBaseSuperframeDuration * 2BO [symbols] = 960 * 2BO [symbols] = * 2BO [msec] = [msec]
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

17. Superframe Timing with SO = 4 and BO = 5
July 2006
Superframe Timing with SO = 4 and BO = 5
BOP
Efficiency = 87.5% when BTTS = 32
aUnitBackoffPeriod = 320 usec B1 B2 B3
……….
B32
Inactive B1
CAP
0.192[msec]: Rx-Tx Turnaround Time
0.768[msec]
0.960[msec]
Duration of BOP with 64 Beacons
= x 32 = [msec]
Duration of CAP with 64 Beacons
= – = [msec]
SD (Superframe Duration) = aBaseSuperframeDuration * 2SO [symbols] = * 2SO [msec] = [msec]
BI (Beacon Interval) = aBaseSuperframeDuration * 2BO [symbols] = 960 * 2BO [symbols] = * 2BO [msec] = [msec]
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

18. Superframe Timing with SO = 4 and BO = 5
July 2006
Superframe Timing with SO = 4 and BO = 5
BOP
Efficiency = 93.75% when BTTS = 16
aUnitBackoffPeriod = 320 usec B1 B2 B3
……….
B16
Inactive B1
CAP
0.192[msec]: Rx-Tx Turnaround Time
0.704[msec]
0.960[msec]
Duration of BOP with 64 Beacons
= x 16 = [msec]
Duration of CAP with 64 Beacons
= – = [msec]
SD (Superframe Duration) = aBaseSuperframeDuration * 2SO [symbols] = * 2SO [msec] = [msec]
BI (Beacon Interval) = aBaseSuperframeDuration * 2BO [symbols] = 960 * 2BO [symbols] = * 2BO [msec] = [msec]
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

19. Backward Compatibility to Legacy Device
July 2006
Backward Compatibility to Legacy Device
We can move all the beacons except MPC’s at the end of the inactive period, forming new BOP and its location.
The node 2 sends his beacon at the beginning of BST in the inactive period.
The same beacon scheduling algorithm is applied to the rest of the devices.
Each device has to wait for about one superframe period until it can send his beacon to his children.
The legacy device turned on in the POS area works just like regular environment in the star topology.
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

20. Beacon Scheduling Performed!
July 2006
Beacon Scheduling Performed! 4 14 2 6 16 3 17 12 18 11 13 7 10 11 3 6 15 19 2 5 2 9 10 5 1 9 20 1 6 2
MPC 4 6 8 4 10 3 7 8 3 7
BOP
CAP
CFP
Deep Sleep
BOP 1 2 3 4 5 6 7 8 9 13 18 1 2 10 12 14 15 11 20 10 16 19 17 16
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

21. BOP Position Change for Legacy Devices
July 2006
BOP Position Change for Legacy Devices
BOP
CAP
CFP
Deep Sleep
BOP 1 2 3 4 5 6 7 8 9 13 18 1 2 10 12 14 15 11 20 10 16 19 17 16
BST (BOP Start Time)
Deep Sleep
Superframe
Deep Sleep for Legacy Device
BOP
CAP
CFP
Deep Sleep for Mesh Device
BOP 9 13 1 2 3 4 5 6 7 8 9 13 18 1 10 12 14 15 11 20 16 19 17
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

22. Beacon Scheduling for Legacy Devices
July 2006
Beacon Scheduling for Legacy Devices 14 16
Node 17
Neighbor Nodes
11,13,14,16
Neighbor's
2,5,9,12
Depth 3
Beacon Time Slots
to Avoid
1,2,3,4,
5,7,9,10
My BTTS 6 17 12 13 11 15 2 5 9 1 6
MPC 8 4 10 3 7
BST (BOP Start Time)
Deep Sleep
Superframe
Deep Sleep for Legacy Device
BOP
CAP
CFP
Deep Sleep for Mesh Device
BOP 9 13 1 2 3 4 5 6 7 8 9 13 1 10 12 14 15 11 16 17
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

23. Beacon Scheduling for Legacy Devices
July 2006
Beacon Scheduling for Legacy Devices 4 14 2 6 16 3 17 12 18 11 13 7 10 3 6 15 11 19 2 5 2 9 10 5 1 9 20 1 6 2
MPC 4 6 8 10 4 3 7 8 3 7
BST (BOP Start Time)
Deep Sleep
Superframe
Deep Sleep for Legacy Device
BOP
CAP
CFP
Deep Sleep for Mesh Device
BOP 9 13 1 2 3 4 5 6 7 8 9 13 18 1 10 12 14 15 11 20 16 19 17
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

24. New Legacy Device in the POS of MPC
July 2006
New Legacy Device in the POS of MPC 14 16 17 12 18 13 15 L1 11 19 L2 2 5 9 20 1
MPC 6 8 10 4 3 7
BST (BOP Start Time)
Deep Sleep
Superframe
Deep Sleep for Legacy Device
BOP
CAP
CFP
Deep Sleep for Mesh Device
BOP 9 13 1 2 3 4 5 6 7 8 9 13 18 1 10 12 14 15 11 20 16 19 17
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

25. Observations Legacy devices can join in the mesh network.
July 2006
Observations
Legacy devices can join in the mesh network.
The new position of BOP is in the inactive period.
The legacy device will not be interfered by other beacons except its MPC beacon because it is in the deep sleep mode.
The optimum size of the BOP which is adaptive in terms of the size of the network may be very important from the power consumption point of view.
They have to wake up to be able to listen to the beacon during the BOP located in the inactive period.
The efficiency in the data communication becomes as good as that of original network.
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

26. New Legacy Devices in the POS of Routers
July 2006
New Legacy Devices in the POS of Routers 14 16 17 12 18 13 15 L1 11 19 L3 L4 2 L2 5 9 20 1
MPC 6 8 10 4 3 7
BST (BOP Start Time)
Deep Sleep
Superframe
Deep Sleep for Legacy Device
BOP
CAP
CFP
Deep Sleep for Mesh Device
BOP 9 13 1 2 3 4 5 6 7 8 9 13 18 1 10 12 14 15 11 20 16 19 17
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

27. Legacy Devices in the POS of Routers
July 2006
Legacy Devices in the POS of Routers
Legacy devices will scan passively and actively, listen to the first beacon and be associated with this device.
He will follow his parent’s beacon information only.
No other beacons will affect his behavior.
So, the star topology around the legacy device’s parent will maintain anyway.
The overall functionality will be the same as the original behavior of the legacy devices.
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

28. Conclusions Addressed some issues of Mesh Networks
July 2006
Conclusions
Addressed some issues of Mesh Networks
Defined a new Mesh Network Architecture
Introduced Beacon Scheduling fundamentals with BOP concept
Proposed the position change of BOP for the supportability of Legacy IEEE Devices
Legacy device in the POS of MPC
Legacy device in the POS of mesh routers
Provided the efficiency analysis in Data Communication
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

29. Acknowledgment This work has been supported by HNRC of IITA. July 2006
Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)