1. May 2006
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [An Analysis of Based Mesh Network Architecture]
Date Submitted: [18 May, 2006]
Source: [Ho-In Jeon (1), Yong-Bae Kim (2), Beom-Joo Kim (2), Jun-Seon Beck (2), Yeonsoo Kim (3)]
Company: [Dept. Electronic Engineering, Kyung-Won University (KWU) (1), LeiiTech Inc. (2)
Advanced Technology Lab., KT (3)]
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.]
Abstract: [This document proposes an Analysis of Based Mesh Network Architecture.]
Purpose: [Final Proposal for 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 Yeonsoo Kim (Advanced Technology Lab., KT)

2. An Analysis of 802.15.4-Based Mesh Network Architecture
May 2006
An Analysis of Based Mesh Network Architecture
Ho-In Jeon (1) and Yeonsoo Kim (2)
(1) Kyung-Won University, HNRC of IITA,
Republic of Korea, and
(2) Advanced Technology Lab., KT
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

3. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
May 2006
Contents
Introduction
Issues of Mesh Networks
Goals of WPAN Mesh Network
Operating Principles of Mesh Network
Superframe Structrue for Mesh Network
Beacon Scheduling – Fundamentals with BOP Concept
Analysis of BOP and CAP Durations
Conclusion
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)
<author>, <company>

4. Issues of Mesh Networks
<month year>
doc.: IEEE <doc#>
May 2006
Issues of Mesh Networks
Beacon Scheduling for Collision Avoidance
Reduction of Power Consumption with Beacon Network
Non-beacon-Enabled Network cannot provide a power-efficient operational mode
Beacon Aggregation for throughput enhancement in the case of two or more PANs merging.
Efficient Real-Time Short Address Allocation Algorithms
Savings of Address Spaces
Routing Algorithm: Proactive or Reactive
Power-Efficient Operation Mode
Support of Time-Critical or Delay-Sensitive Applications
Adoption of RTS/CTS or resource Reservation for Data Transmission
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)
<author>, <company>

5. Goals of WPAN Mesh Network
<month year>
doc.: IEEE <doc#>
May 2006
Goals of WPAN Mesh Network
High speed as well as Low Speed WPAN
High throughput
Low latency
Sensor Network
Easy Network Configuration
Fast and Efficient Short Address Allocations
Possible Usage of Control Channel with single/multiple transceiver/radio solutions
Centralized/Decentralized Beacon Scheduling and/or Aggregation for Spatial Frequency Reuse
Data services
Isochronous
Asynchronous
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)
<author>, <company>

6. Operating Principles of Mesh Networks
May 2006
Operating Principles of Mesh Networks
Devices are associated sequentially, one by one.
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.
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.
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

7. Beacon Scheduling - Fundamentals
May 2006
Beacon Scheduling - Fundamentals
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 PNC 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
PNC
BOP
CAP 3 1 2 3 1
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

8. Beacon Payload Info. for Beacon Scheduling
May 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 Yeonsoo Kim (Advanced Technology Lab., KT)

9. May 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 Yeonsoo Kim (Advanced Technology Lab., KT)

10. Beacon Scheduling May 2006 Node 1 Neighbor Nodes 2,3 Neighbor's x
Depth
Beacon Time Slots
to Avoid
My BTTS 1
Node 2
Neighbor
1,3
Neighbor's x
Depth 1
Beacon Time Slots
to Avoid
My BTTS 2
Node 3
Neighbor
1,2
Neighbor's x
Depth 1
Beacon Time Slots
to Avoid
My BTTS 3 2 1
PNC 3
BOP
CAP 1 2 3
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

11. Beacon Scheduling May 2006 Node 8 Neighbor Nodes 5,6,7,10 Neighbor's
2,3,4,9
Depth 3
Beacon Time Slots
to Avoid
1,2,3,4,5,6,7
My BTTS 8
Node 9
Neighbor Nodes
1,2,3,4,5,6
Neighbor's
7,8
Depth 1
Beacon Time Slots
to Avoid
1,2,3,4,
5,6,7,8
My BTTS 9
Node 10
Neighbor Nodes 8
Neighbor's
5,6,7
Depth 4
Beacon Time Slots
to Avoid
1,5,6,7,8
My BTTS 2 2 5 9 1 6
PNC 8 4 10 3 7
BOP
CAP 1 2 3 4 5 6 7 8 9 10
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

12. Beacon Scheduling May 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 1 2 3 4 5 6 7 8 9 13 10 12 14 15 11 16 17
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

13. Beacon Scheduling Performed
May 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 4 6 8
PNC 4 10 3 7 8 3 7
BOP
CAP 1 2 3 4 5 6 7 8 9 13 18 10 12 14 15 11 20 16 19 17
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

14. An Analysis of BOP and CAP Durations
May 2006
An Analysis of BOP and CAP Durations
The beacon scheduling allows 20 nodes to be located in one PAN with the topology shown by using only 11 BTTS’s.
It may be important to analyze the efficiency of the Mesh Network architecture with BOP concepts.
The analysis is based upon the ratio of the CAP duration to Superframe Duration compared with legacy 15.4 devices.
The efficiency can be improved by adopting adaptive BOP duration, or increasing the transmission rate.
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

15. Neighbor Table in Beacon Payload
May 2006
Beacon Payload Format
Octets : 2 1 4 2
variable
Frame
Control
Sequence
Number
Addressing
Fields
Superframe
Specification
Neighbor Table in Beacon Payload
FCS
MHR
MAC payload
MFR 2 1 8
Depth
My BTTS
(BeaconTxTimeSlot)
Neighbor’s BTTS
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

16. Time Interval for Sending One Beacon
May 2006
Time Interval for Sending One Beacon
The length of Beacon payload for beacon scheduling requires 11 Bytes (88 Bits)
The length of beacon frame without beacon payload is 11 Bytes
The length of PPDU header is 6 Bytes.
The total transmission time of the beacon for beacon scheduling is 28 Bytes which require 28 x 8 x 4 usec = 896 usec.
RX-to-Tx turnaround time requires at least 12 symbols (= 192 usec)
Therefore, the time length for the PAN to allow one beacon to be transmitted in the BOP becomes 1,088 usec (= usec).
In order to cover 1,088 usec, we need 4 aUnitBackoffPeriods (=1,280 usec), which is the minimum time interval for sending 1 beacon in the case that 64 beacons are allowed in the BOP.
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

17. 802.15.4 Superframe Structure and Timing
May 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 Yeonsoo Kim (Advanced Technology Lab., KT)

18. Superframe Timing with SO = 3 and BO = 4
May 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 Yeonsoo Kim (Advanced Technology Lab., KT)

19. Superframe Timing with SO = 4 and BO = 5
May 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 Yeonsoo Kim (Advanced Technology Lab., KT)

20. Superframe Timing with SO = 4 and BO = 5
May 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 Yeonsoo Kim (Advanced Technology Lab., KT)

21. Superframe Timing with SO = 4 and BO = 5
May 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 Yeonsoo Kim (Advanced Technology Lab., KT)

22. Observations on Beacon Scheduling Concept
May 2006
Observations on Beacon Scheduling Concept
The BOP duration with 64 beacons was msec, which can be considered to inefficient.
Legacy 15.4 device spends at least 3 aUnitBackoffPeriod which is msec.
The efficiency of the legacy device for the data transmission with SO = 4 and BO = 5 is 99.6%.
The efficiency of the mesh device with beacon scheduling for the data transmission with SO = 4 and BO = 5 is 66.7%.
One solution for improving the efficiency is to reduce the number of BTTS.
Other solution is to increase the transmission rate.
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

23. Conclusions and Discussions
May 2006
Mesh network requires a lot of problems to be solved
Beacon conflicts and Data Conflicts
Short Address allocations
Hidden and Exposed Node Problems
Delay-Sensitive Applications
Power-Saving Mechanism
Proposed a solution of avoiding beacon conflict by
Beacon scheduling
Proposed a solution of efficient address assignment
Address allocated in real-time by using LAA field.
Solved “Running out of address space” problem.
Proposed an architecture for WPAN Mesh which reflects the real service scenarios.
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)

24. May 2006
Acknowledgment
This work has been supported by Advanced Technology Lab. of KT.
Ho-In Jeon (KWU) and Yeonsoo Kim (Advanced Technology Lab., KT)