doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 1 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [An Architecture for Mesh Networks and 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:[ ], FAX: [ ], Re: [This work has been supported partly by HNRC of IITA and partly by TTA] Abstract:[This document proposes an architecture for the IEEE mesh networks and some issues that need to be resolved for various applications.] Purpose:[Final Proposal for the IEEE a 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

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 2 An Architecture for Mesh Networks and Some Related Issues Ho-In Jeon Kyung-Won University, HNRC, TTA Republic of Korea

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 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

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 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.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 5 Mesh Networking Topologies STAR Cluster Tree Mesh PAN CoordinatorCoordinatorEnd Device

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 6 Overview of IEEE The IEEE 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.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 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

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 8 Limitations of Mesh networks 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.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 9 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 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

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 10 Mesh Example 1: Home Network DCam. PVR VPhone DTV DAM HS/ MMRG Internet FTTH DTV PVR VPhone Refrig. DCam. PC DTV STB PDA Living Room Room #1 Room #3 Room #2 Kitchen Door Phone Water Meter Gas Meter ZigBee/ a/g/n/e, IEEE Oven Cable, Satellite, Terrestrial PC AP or PNC : IEEE802.11x, 15.3, ZigBee/15.4, 15.5 Mesh PDA DCam. Printer PC PDA Room #4 DTV Power Meter Reader Phone Jack Gas Oven Microwave Oven DSLAM Phone Jack Bath- room Utility Room Washer Mesh PNC ONU VDSL MODEM Mesh : IEEE1394 or UWB Connectivity

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 11 Mesh Example 2: Environment Management N-2 N N-1 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.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 12 A Scenario for the Operation of Mesh Network Issues to be resolved –Association and Reassociation Procedure –Beacon Scheduling –Short Address Allocations –Creation and Update of Neighborhood Table PNC

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 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.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 14 Joining of Device 2 to the Mesh Beacon-Only Period Active Period 1 Inactive Period CAP 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.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 15 Neighborhood Table for Mesh Node 1 Device ID2 ……… PANID1 ……… Mesh neighbor address 0x0002 ……… RSSI(dBm)-49 ……… BeaconTx- OffsetTime 2X maxBeaonLength Device Information1 ……… 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 is 0, and the device located in the 1 hop apart from the PNC has the device information of 2.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide Beacon-Only Period Active Period 1 CAP 2 3 Joining of New Node 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 and Short address to Dev. 3. Then Dev. 3 determines when to send its beacon.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 17 Device ID12 …… PANID11 …… Mesh Neighbor Address 0x00010x0002 …… RSSI(dBm) …… BeaconTx- OffsetTime 1X maxBeaconLength 2 X maxBeaconLength Device Info01 …… 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.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide Joining of New Dev. 5 outside the Range 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.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 19 Beacon-Only Period Active Period 1 Inactive Period CAP Beacon Scheduling for Node 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.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 20 Octet:214/102Var. 2 Frame Control Sequence number Addressing Fields Superframe Specification GTS Field Pending Address field Beacon Payload FCS MHRMAC payloadMFR 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.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 21 New Joining of Node

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 22 Beacon Scheduling of Node 6 Beacon-Only Period Active Period 1 Inactive Period CAP

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide New Joining of Node 9 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. 9

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 24 Device ID PANID Neighbor address 0x0010x0020x0030x0040x0050x0060x0070x008 RSSI(dBm) … BeaconTx OffsetTime 1X Max Beacon Length 2X Max Beacon Length 3X Max Beacon Length 4X Max Beacon Length 5X Max Beacon Length 6X Max Beacon Length 7X Max Beacon Length 8X Max Beacon Length Device information 01 …1…112222…2… Neighborhood Table of Node 9

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 25 Beacon-Only Period R A BC R A BE F An Example of Beacon Conflicts for Tree Topology Occurrences of Beacon Conflicts in Tree

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 26 Beacon-Only Period R A BC R A BC E F 1.BOP update command Updated BeaconTxOffsetTime BeaconTxOffsetTime can be selected based upon the updated BeaconTxOffsetTime Beacon Conflicts and Avoidance in Tree

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide Unsupervised Beacon Scheduling 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. PAN 1 PAN 2

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 28 The Solution for Unsupervised Beacon octets: 71 MHR fields Command frame identifier Discovery Request 1.Discovery Response 1.Discovery request 1.Discovery response octets: 721 MHR fields Short address Command Frame Identifier

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 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.

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 30 octets: 71 MHR fields Command frame identifier Command Identifier Command name 0 x 01Association request 0 x 02Association response 0 x 03Disassociation notification 0 x 04Data request 0 x 05PAN ID conflict notification 0 x 06Orphan notification 0 x 07Beacon request 0 x 08Coordinator realignment 0 x 09GTS request 0 x 10BOP update command 0 x 11Discovery request 0 x 12Discovery response 0 x 13Beacon realignment request 0 x 14Beacon slot empty request octets: 71 MHR fields Command frame identifier octets: 71 MHR fields Command frame identifier The Solution for Unsupervised Beacon

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 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

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 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

doc.: IEEE Submission July 2005 Ho-In Jeon, Kyung-Won University Slide 33 Acknowledgment This work has been supported partly by HNRC of IITA and partly by TTA.