1. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
<May 2007>
Project: IEEE P 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],
Re: [Information for IEEE 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 ]
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
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2. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
<May 2007>
Introduction
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3. Flexibility and Options
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doc.: IEEE <doc#>
<May 2007>
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)
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4. Overview of TDMA/CSMA Hybrid
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doc.: IEEE <doc#>
<May 2007>
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
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5. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
<May 2007>
Stack Structure
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6. Field Device Stack Diagram “Current” Version
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doc.: IEEE <doc#>
<May 2007>
Field Device Stack Diagram “Current” Version
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7. Field Device Stack Diagram Recommended Changes
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doc.: IEEE <doc#>
<May 2007>
Field Device Stack Diagram Recommended Changes
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8. What’s in the Lower Data Link Layer (LDLL)?
<month year>
doc.: IEEE <doc#>
<May 2007>
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 as we wish it were
Fewer “features”
More flexibility
IEEE 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 , but not the same
Slot number used for replay protection
Not covered here
Just about “everything else” is different … and handled by the UDLL
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9. Role of LDLL & UDLL Examples
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doc.: IEEE <doc#>
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Role of LDLL & UDLL Examples
LDLL
UDLL & DLL Manager
Topology
Immediate neighborhood
“Mesh” (DLL subnet)
Time Synch
Device level Time synch mechanics
DLL subnet level Manage time propagation messages
Building block
Channel hopping slots
Superframes (Cyclic collections of slots)
Discovery
Sends and receives packets
Discovers and evaluates neighbors
Slot management
Follow a hop sequence
Manage thousands of slots cyclically
Diversity
Handled in by UDLL
Frequency, time, spatial diversity
Route Management
Measure the quality of specific links
Accumulate & report statistics and manage the network topology based on link quality information
Security
Similar to role
Interface with Security Manager
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10. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
<May 2007>
Lower DLL
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11. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
<May 2007>
DLL Structure
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12. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
<May 2007>
TDMA, CSMA, and Hybrid
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13. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
<May 2007>
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 stone See 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
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14. A Case Study WNSIA-Style Operational Superframe
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doc.: IEEE <doc#>
<May 2007>
A Case Study WNSIA-Style Operational Superframe
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15. Channel Hopping Sequences
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doc.: IEEE <doc#>
<May 2007>
Channel Hopping Sequences
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16. Channel Hopping Sequence Implementing a WiFi Coexistence Strategy
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doc.: IEEE <doc#>
<May 2007>
Channel Hopping Sequence Implementing a WiFi Coexistence Strategy
Slot-to-slot channel choices can be made to avoid consecutive channel usage within a single Wi-Fi channel
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17. doc.: IEEE 802.15-<doc#>
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doc.: IEEE <doc#>
Example: “Hop sequence 5” Interlaced with 14 other identical but offset sequences
<May 2007>
Slots within a set of coordinated hop sequences
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18. Hop pattern Optimized for retry in CSMA channel
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doc.: IEEE <doc#>
<May 2007>
Hop pattern Optimized for retry in CSMA channel
Avoid the channels “around” the CSMA channel for better frequency diversity during CSMA retries
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19. Upper DLL TDMA Baseline
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doc.: IEEE <doc#>
<May 2007>
Upper DLL TDMA Baseline
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20. Typical TDMA as viewed by a single router ~2 slots/second used
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doc.: IEEE <doc#>
<May 2007>
Typical TDMA as viewed by a single router ~2 slots/second used
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21. Example: 8 Nodes sharing a TDMA superframe
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doc.: IEEE <doc#>
<May 2007>
Example: 8 Nodes sharing a TDMA superframe
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22. Upper DLL CSMA Baseline
<month year>
doc.: IEEE <doc#>
<May 2007>
Upper DLL CSMA Baseline
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23. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
<May 2007>
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 CSMA-CA with enhancements
Channel hopping
Retry involves channel and link diversity
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24. Example of CSMA Operation
<month year>
doc.: IEEE <doc#>
<May 2007>
Example of CSMA Operation
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25. 8 Routers With interlaced CSMA Hopping Sequences
<month year>
doc.: IEEE <doc#>
<May 2007>
8 Routers With interlaced CSMA Hopping Sequences
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26. Upper DLL TDMA/CSMA Hybrid
<month year>
doc.: IEEE <doc#>
<May 2007>
Upper DLL TDMA/CSMA Hybrid
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27. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
<May 2007>
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
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28. TDMA/CSMA Hybrid with 3 CSMA Control Channels
<month year>
doc.: IEEE <doc#>
<May 2007>
TDMA/CSMA Hybrid with 3 CSMA Control Channels
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29. DLL Manager Decentralized Operation
<month year>
doc.: IEEE <doc#>
<May 2007>
DLL Manager Decentralized Operation
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30. Centralized and decentralized Slot allocation
<month year>
doc.: IEEE <doc#>
<May 2007>
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”
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31. Example of delegated slot allocation 8 routers sharing a superframe
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doc.: IEEE <doc#>
<May 2007>
Example of delegated slot allocation 8 routers sharing a superframe
Different routers have different slots allocated to them which they manage on their own
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