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: [ISA SP100.11a Hybrid DLL Proposal] Date Submitted: [14 May 2007] Source: [Jay Werb] Company [Sensicast] Address [Massachusetts, USA] Voice:[Add telephone number], FAX: [Add FAX number], E-Mail:[jwerb07@sensicast.com] Re: [Information for IEEE 802.15 as per WNG] Abstract: [DLL proposal for ISA SP100.11a containing TDMA and CSMA properties] Purpose: [Information as to how the ISA SP100.11a WG anticipates using IEEE 802.15.4] 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. <Jay Werb>, <Sensicast>

2. Introduction <Jay Werb>, <Sensicast> 2

3. Flexibility and Options The ISA-SP100.11a DLL is designed to be flexible Trade-offs are made by system designers They know more about their applications than we do Default settings will control the scope of validation & testing… … but systems won’t be limited to those defaults Default settings may be overridden by System Manager DLL supports a hierarchy of 5 device classes Backbone Routers (continuously powered) Dedicated Field Routers (continuously powered) Instruments with routing capability (battery powered) Instruments without routing capability (smaller batteries) Very low cost sensors (tiny batteries, CSMA only) <Jay Werb>, <Sensicast> 3

4. Overview of TDMA/CSMA Hybrid Features added to a baseline TDMA structure CSMA periods Fast network discovery using control channels Immediate next-hop propagation of unscheduled commands and alarms Support low end CSMA-only field devices Slot length is configurable to allow for Longer guard times (longer slots) Tighter implementations (shorter slots) Duocast (serial acknowledgement from two devices) CSMA at start of slot (prioritized access to shared slots) Flexible options for hybrid centralized/decentralized operation System Manager can delegate slot allocation to Routers System Manager can allow Routers to create their own superframes & routes <Jay Werb>, <Sensicast> 4

5. Stack Structure <Jay Werb>, <Sensicast> 5

6. Field Device Stack Diagram“Current” Version <Jay Werb>, <Sensicast> 6

7. Field Device Stack Diagram Recommended Changes <Jay Werb>, <Sensicast> 7

8. What’s in the Lower Data Link Layer (LDLL)? Lower Data Link Layer (LDLL) A continuous sequence of channel hopping slots One slot per hop for “TDMA” Slower hopping sequence (~10-25 slots per hop) for “CSMA” May be combined for “Hybrid TDMA/CSMA” The LDLL is IEEE 802.15.4 as we wish it were Fewer “features” More flexibility IEEE 802.15.4 MAC not discussed here Treated as a pass-through to the PHY Designed to work with existing standard 15.4 MACs In silicon or otherwise “unchangeable” LDLL security similar to IEEE 802.15.4, but not the same Slot number used for replay protection Not covered here Just about “everything else” is different … and handled by the UDLL <Jay Werb>, <Sensicast>

9. Role of LDLL & UDLL Examples <Jay Werb>, <Sensicast> 9

10. LowerDLL <Jay Werb>, <Sensicast> 10

11. DLL Structure <Jay Werb>, <Sensicast> 11

12. TDMA, CSMA, and Hybrid <Jay Werb>, <Sensicast>

13. Types of Superframes TDMA only Channel-hopping slots of equal length CSMA only Collect ~10-25 slots on same channel Each collection treated as a single CSMA period Slow channel hopping Hybrid TDMA/CSMA TDMA slots followed by CSMA period This TDMA/CSMA ordering is not written in stoneSee Case Study (next slide) TDMA and CSMA have independent channel hopping patterns TDMA follows an underlying sequence of one hop per slot CSMA follows a slower sequence <Jay Werb>, <Sensicast>

14. A Case StudyWNSIA-Style Operational Superframe <Jay Werb>, <Sensicast> 14

15. Channel Hopping Sequences <Jay Werb>, <Sensicast> 15

16. Channel Hopping SequenceImplementing a WiFi Coexistence Strategy Slot-to-slot channel choices can be made to avoid consecutive channel usage within a single Wi-Fi channel <Jay Werb>, <Sensicast> 16

17. Example: “Hop sequence 5” Interlaced with 14 other identical but offset sequences Slots within a set of coordinated hop sequences <Jay Werb>, <Sensicast> 17

18. Hop patternOptimized for retry in CSMA channel Avoid the channels “around” the CSMA channel for better frequency diversity during CSMA retries <Jay Werb>, <Sensicast> 18

19. Upper DLL TDMA Baseline <Jay Werb>, <Sensicast> 19

20. Typical TDMA as viewed by a single router~2 slots/second used <Jay Werb>, <Sensicast> 20

21. Example: 8 Nodes sharing a TDMA superframe <Jay Werb>, <Sensicast> 21

22. Upper DLL CSMA Baseline <Jay Werb>, <Sensicast> 22

23. CSMA CSMA is fully supported by SP100.11a Typically combined with TDMA (next section) Typically hosted by “continuously powered” routers If you have power available, you might as well provide some level of services when you are not committed to other communications Battery-powered routers may briefly enable CSMA on startup Facilitate network formation CSMA provides key advantages Fast neighbor discovery Immediate transmission of unscheduled commands and alarms Support low-end field devices (tiny batteries, CSMA only) Similar to 802.15.4 CSMA-CA with enhancements Channel hopping Retry involves channel and link diversity <Jay Werb>, <Sensicast> 23

24. Example of CSMA Operation <Jay Werb>, <Sensicast> 24

25. 8 Routers With interlaced CSMA Hopping Sequences <Jay Werb>, <Sensicast> 25

26. Upper DLLTDMA/CSMA Hybrid <Jay Werb>, <Sensicast> 26

27. TDMA/CSMA Hybrid TDMA/CSMA Hybrid is a fully-supported mode of operation Scheduled messages in TDMA slots Retries and unscheduled messages in CSMA periods CSMA periods used for subnet discovery Intended for continuously powered routers Since they have the power, they might as well run their receivers whenever possible Battery powered routers may briefly enable CSMA during network formation TDMA slots provide Predictable performance Managed bandwidth Reduced contention for CSMA bandwidth CSMA periods enable Fast network discovery using control channels (next slide) Immediate transmission of unscheduled commands and alarms Support for low-end CSMA-only field devices <Jay Werb>, <Sensicast> 27

28. TDMA/CSMA Hybridwith 3 CSMA Control Channels <Jay Werb>, <Sensicast> 28

29. DLL ManagerDecentralized Operation <Jay Werb>, <Sensicast> 29

30. Centralized and decentralized Slot allocation Flexible range of centralized/decentralized options Centralized:Network Brain allocates and manages all slots in the network Decentralized: Network Brain authorizes Routers to create and manage superframes Hybrid: Network Brain may delegate slot allocation to capable Routers Resource-limited routers need not support decentralized options Delegated slot allocation: The basics Superframes created by Network Brain Blocks of slots within superframes are delegated to routers Router autonomously allocates delegated slots to its neighbors Mechanics of delegation is standardized Router’s use of slots is opportunity for “value add” <Jay Werb>, <Sensicast> 30

31. Example of delegated slot allocation 8 routers sharing a superframe Different routers have different slots allocated to them which they manage on their own <Jay Werb>, <Sensicast> 31