1. May 2006
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [A Solution to Exposed Node Problem in Mesh Networks]
Date Submitted: [18 May, 2006]
Source: [Ho-In Jeon (1), Yong-Bae Kim (2), Beom-Joo Kim (2), Jun-Seon Beck (2), Yongsik Shin (3)]
Company: [Dept. Electronic Engineering, Kyung-Won University (KWU) (1), LeiiTech Inc. (2)
SKTelecom (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 a Solution to Exposed Node Problem in Mesh Networks.]
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, Kyung-Won University

2. A Solution to Exposed Node Problem in Mesh Networks
May 2006
A Solution to Exposed Node Problem in Mesh Networks
Ho-In Jeon (1), and Yongsik Shin (2)
(1) Kyung-Won University, HNRC of IITA
Republic of Korea, and
(2) SKtelecom
Ho-In Jeon, Kyung-Won University

3. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
May 2006
Contents
Introduction
Issues of mesh networks
Hidden Node Problems
Exposed Node Problems
A Solution to the Exposed Node Problems by Neighbor Table
Conclusion
Ho-In Jeon, Kyung-Won University
<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
Routing Algorithm: Proactive or Reactive
Power-Efficient Operation Mode
Support of Time-Critical or Delay-Sensitive Applications
Adoption of RTS/CTS for Solving Hidden Node Problem
Exposed Node Problems and Their Solutions
Ho-In Jeon, Kyung-Won University
<author>, <company>

5. Association and Direct Link Relations
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May 2006
Association and Direct Link Relations B E A C D
Blue Line: Association Relations
Red Line: Direct Communication Range
Ho-In Jeon, Kyung-Won University
<author>, <company>

6. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Hidden Node Problem
May 2006
Data Transfer A B C
Hidden node problems are solved by adopting RTS/CTS mechanisms.
IEEE Network does not support RTS/CTS under the assumption that the data frame are short enough to cause a serious problem.
Ho-In Jeon, Kyung-Won University
<author>, <company>

7. doc.: IEEE 802.15-<doc#>
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doc.: IEEE <doc#>
May 2006
Exposed Node Problem
Data Transfer D A B C
When node B send data to node A, C cannot send his data to node D, because they adopted CSMA/CA.
The truth is that the node C can still send his data to D at the same time when the node B send the data to node A.
Ho-In Jeon, Kyung-Won University
<author>, <company>

8. Exposed Node Problem - Visualized
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May 2006
Exposed Node Problem - Visualized
Data Transfer D A B C
Superframe
BOP
CAP
Inactive Period B A B C D
Transfer B  A A B C C A B C D A B C
Ho-In Jeon, Kyung-Won University
<author>, <company>

9. Exposed Node Problem - Visualized
<month year>
doc.: IEEE <doc#>
Exposed Node Problem - Visualized
May 2006
Data Transfer D A B C
Superframe
BOP
CAP
Inactive Period B A B C D
Transfer B  A A B C
Cannot be used C A B C D
Transfer C  D A B C
Ho-In Jeon, Kyung-Won University
<author>, <company>

10. Solution by Using Neighbor Table
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doc.: IEEE <doc#>
May 2006
Solution by Using Neighbor Table
Data Transfer D A B C
B’s Neighbor Table
C’s Neighbor Table
Address B
Neighbor’s Address
A, C
Data Transfer Destination A
Address C
Neighbor’s Address
B, D
Data Transfer Destination D
Superframe
BOP
CAP
Inactive Period B A B C D
Transfer B  A A B C C A B C D
Transfer C  D A B C
Ho-In Jeon, Kyung-Won University
<author>, <company>

11. Conclusions and Discussions
May 2006
The operating principles of the Mesh Network has been addresses.
Hidden node problems are solved by the adoption of RTS/CTS mechanism.
Exposed node problem can be solved by using neighbor tables of each node.
The prepared sender has to get the information of the destination node from the receiving signal.
The efficiency can not be as good as 100%, in theory.
Ho-In Jeon, Kyung-Won University

12. Acknowledgment This work has been supported by HNRC of IITA. May 2006
Ho-In Jeon, Kyung-Won University