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

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [IEEE 802.15.5 WPAN Mesh Networks Summary] Date Submitted: [19 July, 2005] Source: [Jianliang Zheng, Yong Liu, Chunhui Zhu, Marcus Wong, Myung Lee] Company [Samsung] Address [Samsung Lab@CUNY, Steinman Hall, 140th St & Convent Ave, New York, NY 10031, USA] Voice:[+1-212-650-7260], FAX: [+1-212-650-8249], E-Mail:[lee@ccny.cuny.edu] Re: [Call for Proposal: IEEE P802.15-5/0071] Abstract: [This document discusses Samsung’s proposal for IEEE 802.15.5 WPAN Mesh, based on Meshed-Tree approach.] Purpose: [This proposal is provided to be adopted as a recommended practice for IEEE WPAN Mesh] 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. Zheng, Liu, Zhu, Wong, Lee

2. IEEE 802.15.5 WPAN Mesh Networks Jianliang Zheng, Yong Liu, Chunhui Zhu, Marcus Wong, Myung Lee Samsung Lab @ CUNY Zheng, Liu, Zhu, Wong, Lee

3. Objectives • To construct Mesh Networking Layer over IEEE 802.15.4 MAC and PHY • Proposed Mesh Network includes following features: • Meshed Tree Formation • Block Addressing • Routing • Key Pre-distribution * • Multicasting ** • Extensible to IEEE 802.15.3 MAC and PHY *, ** Refer to 15-05-0256-01-0005-802-15-5-mesh-networks-samsung Zheng, Liu, Zhu, Wong, Lee

4. Contents • Meshed tree approach • Centralized approach Zheng, Liu, Zhu, Wong, Lee

5. MeshedTree Zheng, Liu, Zhu, Wong, Lee

6. Outline • Adaptive Robust Tree (ART) • ART • Meshed ART (MART) • Mesh Networking • Data Forwarding • Route Discovery • Tree Route Repair • Summary Zheng, Liu, Zhu, Wong, Lee

7. ART: Initialization Phase [children#][children#]=[8][6] A [beg,end,next]=[1,16,1][beg,end,next]=[17,28,17] • Stage 1: Association [5][2] [5] B J • Stage 2: Reporting number of children [3,12,3][13,16,13] [19,28,19] C H K [1][2][1] [3][1] [1] • Stage 3: Address assignment • An ART is formed. • Additional addresses can be reserved. [5,6,5][7,10,7][11,12,11] [21,26,21][27,28,27] [15,16,15] D E G I L O [1][1] [0] [0] [1] [0] [0] [23,24,23][25,26,25] [9,10,9] F M N [0] [0] [0] Zheng, Liu, Zhu, Wong, Lee

8. ART: Normal Phase [8][6] A0 [1,16,1] • Normal data transmissions [17,28,17] [5][2] [5] B1 J17 [3,12,3][13,16,13] [19,28,19] • Example: Node C node L C3 H13 K19 [1][2][1] [3][1] [1] • Nodes are still allowed to join the network [5,6,5][7,10,7][11,12,11] [21,26,21] [15,16,15] [27,28,27] D5 E7 G11 I15 L21 O27 [1][1] [0] [0] [1] [0] [0] [23,24,23][25,26,25] [9,10,9] F9 M23 N25 [0] [0] [0] Zheng, Liu, Zhu, Wong, Lee

9. Meshed ART (MART) [8][6] [1,16,1][17,28,17] A0 • Neighbors treat each other as a child. [5][2] [5] [3,12,3][13,16,13] [19,28,19] B1 J17 [1,16,1] [17,28,17] [13,16,13] • Shorter path C H13 [1] K [15,16,15] • Elimination of SPOFs [17,28,17] …… D E G I L O F M N Zheng, Liu, Zhu, Wong, Lee

10. Start Find an optimal route in NTT? Y N Find an optimal route in ARTT? Y N Find an auxiliary route in NTT? Y N 1 2 3 4 Use the route found Use tree route 1 2 Optimal routes 3 4 Non-optimal routes Data Forwarding Zheng, Liu, Zhu, Wong, Lee

11. Route Discovery (1) A • Case 1: Source has an optimal route • No route discovery B J C H K D E G I L O • Example 1:node F nodeI(optimal non-tree route) F M N • Example 2:node J nodeM(optimal tree route) Optimal non-tree route Optimal tree route Zheng, Liu, Zhu, Wong, Lee

12. A B J C H K D E G I L O F M N Route Discovery (2) • Case 2: Source has no optimal route; but destination has. dst. • Example 1:node F nodeI • Bi-directional routes are set up dst. • Example 2:node N nodeJ • No routing entry created src. src. unicast RREQ unicast RREP existing optimal non-tree route Zheng, Liu, Zhu, Wong, Lee

13. Route Discovery (3) A • Case 3: Neither the source nor the destination has optimal route. B J C H K • Example:node I nodeO D E G I L O src. dst. F M N unicast RREQ broadcast RREQ RREP Zheng, Liu, Zhu, Wong, Lee

14. MART route RREQ RREP RCFM Tree Route Repair A • Node J broadcasts an RREQ to locate node K, with a limited TTL. • Node K fails B J C H K • All nodes below node K that have received the RREQ reply. D E G I L O • Node J selects the best path and sends an RCFM to activate it. F M N Zheng, Liu, Zhu, Wong, Lee

15. Tree Route Repair (cont.) Data Forwarding after tree route repair A [desIn,19,28,down,19] [desIn,21,26,normal,13] B J17 C H13 K [desIn,21,26,normal,21] [srcIn,21,26,normal,17] D E G I L21 O [1][1] [23,24,23][25,26,25] parent=13 F M N Zheng, Liu, Zhu, Wong, Lee

16. Summary • Adaptive address assignment • avoiding “running out of addresses” problem • Efficient tree repair • no address re-assignment • Meshed ART (MART) • shorter path • Robustness • Mesh networking (Tree routing + Non-tree routing) • optimal routes • no broadcast (even with limited TTL) if either the source or the destination has an optimal route • no flooding if there is a (non-optimal) route from the source to the destination Zheng, Liu, Zhu, Wong, Lee

17. Centralized Approach Zheng, Liu, Zhu, Wong, Lee

18. Basic Mechanisms • Tree formation • Tree addressing • Tree routing • Topology server setup • Beacon scheduling • Reactive shortcut formation • Two-address strategy • Route repair Zheng, Liu, Zhu, Wong, Lee

19. Tree Formation • The node initiating the network becomes the PAN coordinator. • In the network formation stage, all coordinators shall enable their receivers to catch beacon requests from new nodes. • No regular beaconing is allowed before the beacon scheduling is done. • New nodes perform active scan to collect beacons from their neighbors. • Every new node selects a neighbor, which has the best path quality to the PAN coordinator, as its parent. Zheng, Liu, Zhu, Wong, Lee

20. Tree Addressing Zheng, Liu, Zhu, Wong, Lee

21. Tree Routing • Node H sends a packet to node F. • As H does not have any child, it forwards the packet to its parent C. • C finds that F has an address out of its address block. So it forwards the packet to its parent A. • As F’s address falls into A’s address block, and A further finds that F’s address is between the addresses of child B and C, so A forwards the packet to B. • B forwards the packet to F. Zheng, Liu, Zhu, Wong, Lee

22. Topology Server Setup • Either the PAN coordinator or a resource sufficient node can serve as the topology server. • All other nodes can reach the topology server by using tree routing. • Each coordinator shall report its superframe parameters and link states to the topology server. • Each coordinator may periodically scan its neighbors' beacons and report significant link changes to the server. • There can be two or more topology servers acting as backup of each other. Zheng, Liu, Zhu, Wong, Lee

23. Beacon Scheduling • When receiving the neighboring information of a coordinator, the topology server assigns a contention-free beacon time-slot to the coordinator. • Every coordinator gets a beacon time slot that is not overlapped with the active periods of its two-hop neighbors. • This two-hop beacon scheduling ensures that each node can correctly capture all its neighbors’ beacons and locate their active periods. • Once a coordinator receives the beacon time assignment, it can emit regular beacons and operate in beacon-enabled mode. Zheng, Liu, Zhu, Wong, Lee

24. Reactive Shortcut Formation • An active source sends a shortcut request (SCRQ) message to the topology server. • The topology server calculates the optimal shortcut by using the Dijkstra’s algorithm. • The topology server sends a shortcut notification (SCNF) message to the destination. • The destination sends a shortcut reply (SCRP) message to the source to establish routing entries along the shortcut. • Relay nodes along the shortcut shall locate and record the active periods of their previous-hop and next-hop neighbors. Zheng, Liu, Zhu, Wong, Lee

25. Summary • Establish a self-routing tree to cover the whole network • Schedule beacon transmissions at a topology server to avoid beacon collisions • Calculate shortcuts between active source-destination pairs at a topology server to avoid flooding based route discovery • Quickly recover from link/node failures by recalculating new routes or reforming the tree Zheng, Liu, Zhu, Wong, Lee

26. Key Pre-Distribution Zheng, Liu, Zhu, Wong, Lee

27. Key Pre-Distribution 6 1 Center 2 5 4 3 Zheng, Liu, Zhu, Wong, Lee

28. 1 2 3 4 5 6 K1 K2 K3 K4 K5 K6 K7 K8 K9 K10 Zheng, Liu, Zhu, Wong, Lee

29. 5 6 Common Key Computation 1 2 3 K34=H( )= 4 =Hash(K5||K10) No other node can compute K34 ! Zheng, Liu, Zhu, Wong, Lee

30. 1 3 2 4 5 K45=H( ) K45=H( ) WMN and Key Pre-Distribution Mesh clients Need secure Connection ! Backbone Zheng, Liu, Zhu, Wong, Lee

31. 1 3 2 EK45(message) 4 5 K45=H( ) K45=H( ) WMN and Key Pre-Distribution Zheng, Liu, Zhu, Wong, Lee

32. 1 3 2 EK45(message) 4 5 K45=H( K45=H( ) ) WMN and Key Pre-Distribution Zheng, Liu, Zhu, Wong, Lee

33. Benefits of using KPDS inDistributed Key Management • Any link between nodes is secured through common key of a pair • No need for on-line servers • Simple node’s exclusion and association • Self-healing through key refresh • Robustness due to distributed solution • Simple implementation and low resources requirements Zheng, Liu, Zhu, Wong, Lee