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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [An Architecture for Mesh Networks and Some Related Issues ] Date Submitted: [15 July , 200 5] Source: [Ho-In Jeon (1), Sung-Hoon Jeong (2)]

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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [An Architecture for Mesh Networksand Some Related Issues] Date Submitted: [15 July, 2005] Source: [Ho-In Jeon (1), Sung-Hoon Jeong (2)] Company: [Dept. Electronic Engineering, Kyung-Won University(KWU) (1), LeiiTech Inc. (2)] Address: [San 65, Bok-Jung-Dong, Sung-Nam-Shi, Kyung-Gi-Do, Republic of Korea] Voice:[ +82-31-753-2533], FAX: [+82-31-753-2532], E-Mail:[jeon1394@kornet.net] Re: [This work has been supported partly by HNRC of IITA and partly by TTA] Abstract: [This document proposes an architecture for the IEEE 802.15.5 mesh networks and some issues that need to be resolved for various applications.] Purpose: [Final Proposal for the IEEE802.15.4a standard] Notice: This document has been prepared to assist the IEEE P802.15. 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 P802.15. Ho-In Jeon, Kyung-Won University

  2. An Architecture for Mesh Networks and Some Related Issues Ho-In Jeon Kyung-Won University, HNRC, TTA Republic of Korea Ho-In Jeon, Kyung-Won University

  3. Contents • Introduction • Definition of mesh networks • Issues of mesh networks • Beacon Scheduling • Short Address Allocation • RTS/CTS for Collision Avoidance • Routing • Power-Saving Operation Mode • Unsupervised Beacon Scheduling • Address Allocation • Conclusion Ho-In Jeon, Kyung-Won University

  4. Definition of Mesh Network • A mesh network is a PAN that employs one of two connection arrangements, full mesh topology or partial mesh topology. • In the full mesh topology, each node is connected directly to each of the others. • In the partial mesh topology, some nodes are connected to all the others, but some of the nodes are connected only to those other nodes with which they exchange the most data. Ho-In Jeon, Kyung-Won University

  5. Mesh Networking Topologies Cluster Tree Mesh STAR PAN Coordinator Coordinator End Device Ho-In Jeon, Kyung-Won University

  6. The IEEE 802.15 Task group 5 is chartered to determine the necessary mechanisms that must be present in the PHY and MAC layers of WPANs to enable mesh networking. A mesh network is a PAN that employs one of two connection arrangements, full mesh topology or partial mesh topology. In the full mesh topology, each node is connected directly to each of the others. In the partial mesh topology, some nodes are connected to all the others, but some of the nodes are connected only to those other nodes with which they exchange the most data. Overview of IEEE 802.15.5 Ho-In Jeon, Kyung-Won University

  7. Capabilities of Mesh Networks • Extension of network coverage without increasing transmit power or receive sensitivity • Enhanced reliability via route redundancy • Easier network configuration • Better device battery life due to fewer retransmissions Ho-In Jeon, Kyung-Won University

  8. Hidden nodes Devices are unaware of current neighbors receiving data. Collisions of Beacon and Data. Mutual Interference Causing Beacon and Data Conflict. Exposed nodes Devices are unaware of their position relative to receiver. Concurrent transmission in same time period possible but unused. Inefficient spatial frequency reuse. Limitations of Mesh networks Ho-In Jeon, Kyung-Won University

  9. Beacon Scheduling for Collision Avoidance Reduction of Power Consumption with Beacon Network Non-beacon-Enabled Network cannot provide a power-efficient operational mode Short Address Allocation Algorithms Savings of Address Spaces Adoption of RTS/CTS for Data Transmission Deterioration of Data Throughput Overall Delay Exposed Node Problem Routing: Proactive or Reactive Power-Efficient Operation Mode Support of Time-Critical or Delay-Sensitive Applications Issues of Mesh Networks Ho-In Jeon, Kyung-Won University

  10. Mesh Mesh Mesh PC Mesh Example 1: Home Network Gas Meter Washer UtilityRoom Room #3 VPhone Gas Oven PDA Room #2 Bath- room DTV Refrig. DTV PC Microwave Oven Oven Kitchen STB DCam. : IEEE1394 or UWB Connectivity : IEEE802.11x, 15.3, ZigBee/15.4, 15.5 Mesh Door Phone Living Room VPhone ZigBee/15.4 802.11a/g/n/e, IEEE802.15.3 MeshPNC DTV Meter Reader PVR Room #1 Power Meter PC DCam. Room #4 DTV VDSLMODEM PDA DAM Water Meter PVR Printer Phone Jack HS/MMRG Phone Jack AP or PNC PDA DCam. Cable, Satellite, Terrestrial Internet FTTH DSLAM ONU Ho-In Jeon, Kyung-Won University

  11. Mesh Example 2: Environment Management N-2 N-1 4 N 1 3 5 2 10 Km • A scenario in which the device 1 wishes to send its sensed data to device N which is located 10 Km apart. • Assumptions • The RF range of each device is assumed to be 20m. • Multihop topology has been used for the propagation of data • Each device is assumed to use beacon to save power consumption. • Device 2 listens to the beacon transmitted by device 1 and decides to associate with it. Device 2 determines its beacon tramitting time slot. • Device 1 is 40m apart from device 2 which implies that device 3 cannot listen to device 1. Ho-In Jeon, Kyung-Won University

  12. A Scenario for the Operation of Mesh Network 4 9 6 5 2 9 1 PNC 6 4 8 3 7 • Issues to be resolved • Association andReassociation Procedure • Beacon Scheduling • Short Address Allocations • Creation and Update ofNeighborhood Table Ho-In Jeon, Kyung-Won University

  13. PNC Formation of the Mesh 1 • Device 1 first scans passively and actively, and found that there is no device that he can associate. • So, it becomes the PNC. • Once a device becomes a PNC, it starts to transmit its beacon at the beginning of the superframe. Ho-In Jeon, Kyung-Won University

  14. Joining of Device 2 to the Mesh 2 1 • Dev. 2 hears the beacon form PNC and gets associated with it. • When associated, it gets PANID, Short Address, and other informations and determines when to send its beacon. • Dev. 1 and 2 listen to beacons of each other and store information about their neighbir in the Neighborhood Table. Inactive Period Active Period Beacon-Only Period CAP 1 2 Ho-In Jeon, Kyung-Won University

  15. Neighborhood Table for Mesh Node 1 • Neighborhood Table is created based on the beacon that it listens • PANID, Short Address, RSSI, PNC, Depth Information, Device Information, and so on. • The Device information of PNC is0, and the device located in the 1 hop apart from the PNC has the device information of 2. Ho-In Jeon, Kyung-Won University

  16. Joining of New Node 3 2 1 3 • Device 3 is associated with PNC after it listens to the beacons transmitted from both PNC and Dev. 2. • The PNC assigns the PANID andShort address to Dev. 3. • Then Dev. 3 determines when to send its beacon. Active Period Beacon-Only Period CAP 1 2 3 Ho-In Jeon, Kyung-Won University

  17. Neighbor Table for Mesh Node 3 • Dev. 3 stores information about its neighborhoods in the Neighborhood Table. • Dev. 1 also updates its Neighborhood Table based on the beacon information that it hears. Ho-In Jeon, Kyung-Won University

  18. Joining of New Dev. 5 outside the Range 2 1 5 4 3 • Dev. 5 can listen to beacons of only Dev. 2, 3, and 4 since it is outside the RF range of Dev. 1. • Dev. 5 decides to associate with Dev. 2 because the beacon of Dev. 2 is the first one that it hears. • Beacon transmission time of Dev. 5 is determined by itself in the way to avoid the beacon conflict. Ho-In Jeon, Kyung-Won University

  19. Beacon Scheduling for Node 5 Inactive Period Active Period Beacon-Only Period CAP 1 2 3 4 5 • Dev. 2 allocates the BeaconTxOffsetTime to Dev. 5 and send the BOP update command because Dev. 1 does not know whether Dev. 2 has allocated a BeaconTxOffseTime to Dev. 5 • When Dev. 1 receives BOP update command, it increments his BeaconTxOffsetTime register by 1. Ho-In Jeon, Kyung-Won University

  20. Beacon Payload for the Mesh Formation • On receipt of BOP update command, every device increments his BeaconTxOffsetTime information in its register. • BeaconTxOffsetTime information is always transmitted in the beacon payload to update the neighborhood table. < BeaconTxOffsetTime > Ho-In Jeon, Kyung-Won University

  21. New Joining of Node 6 4 6 5 2 1 6 4 3 Ho-In Jeon, Kyung-Won University

  22. Beacon Scheduling of Node 6 4 6 5 2 1 6 4 3 Inactive Period Active Period Beacon-Only Period CAP 1 2 3 4 5 6 Ho-In Jeon, Kyung-Won University

  23. New Joining of Node 9 9 5 2 9 1 6 4 8 3 7 • Dev. 9 can listen to the beacon of Dev. 1 and is associated with it. • Even though Dev. 9 cannot listen to Dev. 8, Dev. 8 is included in the neighborhood table of Dev. 9, because it is in the range of Dev. 8. Ho-In Jeon, Kyung-Won University

  24. Neighborhood Table of Node 9 Ho-In Jeon, Kyung-Won University

  25. Occurrences of Beacon Conflicts in Tree Beacon-Only Period A R B C Beacon-Only Period A F R B E An Example of Beacon Conflicts for Tree Topology Ho-In Jeon, Kyung-Won University

  26. Beacon-Only Period A R B C Beacon Conflicts and Avoidance in Tree UpdatedBeaconTxOffsetTime • BOP update command Beacon-Only Period A E R B C F BeaconTxOffsetTime can be selected based upon the updated BeaconTxOffsetTime Ho-In Jeon, Kyung-Won University

  27. Unsupervised Beacon Scheduling PAN 2 PAN 1 3 2 1 • Two PANs cannot listen to the other, such that they can never be associated. • Then the Dev. 3 will never be associated when there beacon conflicts keep happening. Ho-In Jeon, Kyung-Won University

  28. The Solution for Unsupervised Beacon • Discovery Request • Discovery Request 1 2 3 • Discovery Response • Discovery Response • Discovery request • Discovery response Ho-In Jeon, Kyung-Won University

  29. The Solution for Unsupervised Beacon • When Dev. 3 cannot listen to any beacon for a given predetermined period of time, it sends, after CSMA/CA, Discovery Request command. • Dev. 1 that received Discovery request command performs a random number generation for its new BeaconTxOffset Time where he knows empty. Ho-In Jeon, Kyung-Won University

  30. The Solution for Unsupervised Beacon < BOP update command > <Beacon realignment request command> <Beacon slot empty request command> < Command frame identifier > Ho-In Jeon, Kyung-Won University

  31. Address Allocations • Block addressing wastes address space • Centralized Address allocations • May take too much time for the address allocation. • Distributed Address allocations • Beacon Scheduling mechanism can be used for the address allocation Ho-In Jeon, Kyung-Won University

  32. Conclusions • Mesh network causes a lot of problems • Beacon conflicts • Data Conflicts • Address allocations • Hidden node problems • Delay-Sensitive Applications • Power-saving mechanism • Proposed some architectural solutions • Beacon scheduling • Address allocation, if not quite in detail: next time Ho-In Jeon, Kyung-Won University

  33. Acknowledgment • This work has been supported partly by HNRC of IITA and partly by TTA. Ho-In Jeon, Kyung-Won University

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