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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 IEEE 802.15 WPAN Mesh Network ] Date Submitted: [15 July , 200 5] Source: [Ho-In Jeon (1), Yong-Bae Kim (2), Bum-Joo Kim (2), Jun-Seon Beck (2), Yongsik Shin (3)]

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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 IEEE 802.15 WPAN Mesh Network] Date Submitted: [15 July, 2005] Source: [Ho-In Jeon (1), Yong-Bae Kim (2), Bum-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:[ +82-31-753-2533], Voice 2:[ +82-19-9101-1394] FAX: [+82-31-753-2532], E-Mail:[jeon1394@kornet.net] Re: [This work has been supported by HNRC of IITA.] Abstract: [This document proposes an architecture for IEEE 802.15 WPAN Mesh Network.] Purpose: [Final Proposal for the IEEE802.15.5 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, Yongsik Shin, SKTelecom

  2. An Architecture for IEEE 802.15 WPAN Mesh Network 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, Yongsik Shin, SKTelecom

  3. Contents • Introduction • Issues of mesh networks • Goals of WPAN Mesh Network • A Scenario for the operation of Mesh Network • Proposed Architecture for WPAN Mesh • Superframe Structrue for Mesh Network • Efficient Real-Time Address Assignment vs. ABA • Features of the Proposed Architecture • Conclusion Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  4. 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 Issues of Mesh Networks Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  5. High speed as well as Low Speed WPAN High throughput Low latency Sensor Network Easy Network Configuration Fast and Efficient Short Address Allocations 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 Goals of WPAN Mesh Network Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  6. Assumptions for Mesh Network Operations • Devices are associated sequentially, one by one. • No initialization process exists. • The relation between parent and children are characterized by association. • Children are my neighbors. • Parent is also my neighbors. • All devices I can hear are my neighbors. • Solid blue line represents the Parent-Child relations based on associations. • Solid red line represents directly reachable nodes. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  7. A Scenario for Mesh Network Operations 4 9 1 2 6 5 2 9 1 6 PNC 3 4 8 7 • Node 1 is the first device turned on. • Node i is the ith device that was associated with the PAN • The number in the dotted circle represents the device of which the Tx range reaches. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  8. PNC Formation of the Mesh 1 1 PNC • Device 1 first scans passively first and actively next. • When it finds that there is no device that he can associate with, 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, Yongsik Shin, SKTelecom

  9. Joining of Device 2 to the Mesh 1 2 2 1 PNC • Dev. 2 hears the beacon form PNC and gets associated with it. • When associated, it gets PANID, Short Address, and other sets of information from PNC and determines when to send its beacon. • Dev. 1 and 2 listen to beacons of each other and store information about their neighbor in the Neighborhood Table. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  10. Association Relations and Beacon Tx • Every mesh device transmits beacon during the BOP (Beacon-Only Period) to save BOP usage. • Beacon scheduling needs to be applied. 2 1 PNC 3 Superframe InactivePeriod Active Period BOP CTA CAP 1 3 1 3 2 2 Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  11. Association and Direct Links Relations 4 9 1 2 6 5 2 9 1 6 PNC 3 4 8 7 Superframe InactivePeriod BOP CTA CAP 1 3 4 5 6 1 3 2 7 2 9 8 8 Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  12. Association and Direct Links Relations 2 5 9 1 6 PNC 8 4 3 7 • Blue Line: Association Relations • Red Line: Direct Communication Capable • Association Policy • New nodes are associated with the nodes which are as close to the PNC and possible • If RSSIis not high enough for reliable communications, then it can choose other node as its parent. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  13. Superframe Structure Agreement • When a beaconing device powers up, it scan for at least one superframe and shall attempt to join the existing beacon group, if any (better performance) • When two beacon devices (or two groups) observe each other, they shall “cross protect” each other’s beacon transmission (reduced complexity) Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  14. Beaconing Device Powers Up • Every mesh device has to send his beacon. • However, the end device may not be obligated to send his beacon to alleviate the possibilities of beacon conflicts. 2 5 9 1 6 PNC 8 4 3 7 Superframe InactivePeriod BOP CTA CAP 1 3 4 5 6 1 3 2 7 2 9 8 8 Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  15. Superframe for Merge of 2 PANs • When superframe sizes of the two PANs are different, the channel utilization becomes poor. • It is recommended to have aggregated beacons in the beginning of the superframe even when two PANs are merged. Intervals that cannot be used for data transmissions Superframe of PAN 1 A B C A B C D E F D E F D E F Superframe of PAN 2 Superframe of PAN 2 Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  16. Thoughts on Fully Distributed Mesh • PAN ID • This is acquired by PNC at his own will. • Without same PAN ID, no communication can be made. • PAN ID information must be delivered to every device of the PAN • Beacon Transmission Start/End Time • This information must be disseminated all over the PAN to allow new DEV to pick up his Beacon Transmission Time. • Short Address Conflicts • Not sure if there is a perfect mechanism to avoid the short address conflicts • A (reference) node may solve this problem for a special case. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  17. Short Address Allocations • Hierarchical Block addressing wastes address space. • Centralized Address allocations • May take too much time for the address allocation. • Distributed Address allocations • No guarantee way of avoiding address conflicts. • A mechanism of assigning short addresses in real-time in an efficient way that can prevent address conflict has been needed. • Combination of the two mechanisms. • Beacon Scheduling mechanism can be used for the address allocation Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  18. Adaptive Block Addressing [children#][children#]=[8][6] resv’ed: [beg,end]=[0,9000]branch1: [beg,end]=[9001,41000]branch2: [beg,end]=[41001,65000] A • Stage 1: Association • Stage 2: Children number collection [5][2] [5] B J [9001,13000][13001,33000][33001,41000] [41001,45000][45001,65000] • Stage 3: Address assignment • An adaptive tree (AT) is formed. • Additional addresses are reserved. [1][2][1] [3][1] C H K [1] [13001,17000][17001,21000][21001,29000][29001,33000] [45001,49000][49001,61000][61001,65000] [33001,37000][37001,41000] [0] [37001,41000] [0] D E G I L O [0] [1][1] [61001,65000] [1] [0] [29001,33000] [49001,53000][53001,57000][57001,61000] [17001,21000] [21001,25000][25001,29000] F M N [0] [0] [0] [25001,29000] [57001,61000] [53001,57000] Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  19. Guesses on Adaptive Block Addressing • Time for the association stage can be long. • Until association, the node cannot have his short address. • It did not solve the “running out of address” problem • Once a block is assigned to a branch, the block of the addresses is wasted until all the blocked addresses are allocated to the devices associated to that branch. • When new device is associated directly with PNC, a new block of addresses must be allocated, and this causes another waste. • Address allocation time can be long. • When a new device is associated with the node F, it does not have any address to allocate. • It has to wait until new address is assigned from the PNC Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  20. Efficient Real-Time Address Assignment PNC A [0, 1] [1, 4] [1, 2] [1, 3] D C B • Devices B, C and D hear the beacon of A (PNC) and send Association Request Command. • Since A is PNC, PNC allocates the Short addresses to devices B,C,D directly. • If other device than PNC allocates shortAddress, it is possible that same address could be allocated to different devices. • To avoid this problem, LAA (LastAddressAssigned) field has been added. • The last address assigned at this point is 4, and the PNC sends this information to other devices using his beacon payload. To let B, C, and C know about this. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  21. Efficient Real-Time Address Assignment PNC A [0, 1] Beacon Update Request Command [1, 4] [1, 2] [1, 3] D C B E [2, 5] • Now, a new device E is on. As soon as he hears the beacon of B, it requests association. • Since B knows that the last address assigned is 4, B assigns the short address 5 to E and notifies the PNC of the new value of the LAA field through BeaconUpdateCommamd. • As soon as PNC receives this information, it modifies his beacon payload and send the modified beacon. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  22. Efficient Real-Time Address Assignment PNC [0, 1] A Beacon Update Request Command [1, 4] [1, 2] [1, 3] D C B [2, 5] E F • When F associates, B assigns address 6 to F and sends the number 6 as the LAA (Last Address Assigned) to A. • Again, when A receives this command, it send his beacon after changing his beacon payload. • Because of the beacon payload, E and F knows the LAA. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  23. Efficient Real-Time Address Assignment PNC [0, 1] A Beacon Update Request Command [1, 4] [1, 2] [1, 3] D C B Beacon Update Request Command [2, 6] I H E [2, 5] F J • When J associates with F, F assigns address 7 to J and sends the number 7 as the LAA (Last Address Assigned) to B, and B sends this information to A. • Again, when A receives this command, it send his beacon after changing his beacon payload, and every device knows the LAA. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  24. Efficient Real-Time Address Assignment PNC A Beacon Update Request Command Beacon Update Request Command [1, 2] [1, 4] D C B [1, 3] [2, 5] [2, 5] I E Overlapped address assigned in real-time • A possible problem • When E and I associate, respectively, with B and D simultaneously, the same address may be assigned to tow different devices. • Solution • When this happens, the PNC sends Address Reassignment Command to the later arriving device Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  25. Efficient Real-Time Address Assignment Beacon Update Response Command PNC A [1, 2] [1, 4] D C B [1, 3] [2, 5] [2, 5] I E Overlapped address assigned in real-time Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  26. Efficient Real-Time Address Assignment PNC Address Reassign Command A [1, 4] Address Reassign Command [1, 2] D C B [1, 3] [2, 6] [2, 5] I E Address Confliction resolved. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  27. Efficient Real-Time Address Assignment PNC A Beacon Update Request Command Beacon Update Request Command Beacon Update Response Command Address Reassign Command D C B I E G Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  28. Efficient Real-Time Address Assignment PNC Beacon Update Request Command A Beacon Update Request Command D G B Beacon Update Request Command I F C E H Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  29. Efficient Real-Time Address Assignment PNC A Beacon Update Request Command Beacon Update Request Command Address Reassign D C B Beacon Update Request Command Beacon Update Request Command Beacon Update Request Command Beacon update Response command Address Reassign G H E F Beacon Update Request Command Beacon Update Request Command Beacon update Response command Beacon Update Request Command Address Reassign Address Reassign I J K Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  30. New Beacon Payload and Update Commands < LAA + Depth Info + BOPLength + BTTS > <Beacon Update Request Command> LAA: LastAddressAssigned BTTS: BeaconTxTimeSlot < Beacon update Response Command> Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  31. Features of the Proposed Addressing Scheme • Pros • Allocates short addresses in real-time. • It is a decentralized addressing scheme combined with central PNC. • “Running out of addresses” problem is completely solved. • Network diameter not necessarily fixed. • Cons • New control commands must be added: Address Request, Address Response, Beacon Update, Address Reassign • Some delays occur in the Association process • Increased data processing in the PNC • Address reuse mechanism needs to be addressed. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

  32. Conclusions and Discussions • 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, Kyung-Won University, Yongsik Shin, SKTelecom

  33. Acknowledgment • This work has been supported by HNRC of IITA. Ho-In Jeon, Kyung-Won University, Yongsik Shin, SKTelecom

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