July 2008
L. Winkel, M. Bahr, Siemens AGSlide 1
doc.: IEEE 802.15-0503r0
Submission
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: [ Preliminary Proposal for Factory Automation ]Date Submitted: [ 15 July, 2008 ]Source: [ Ludwig Winkel, Michael Bahr ] Company [ Siemens AG ] Address [Siemensallee 74, Karlsruhe, Germany]Voice:[+49-721-595 6098], FAX: [+49-721-595 893 6098], E-Mail:[[email protected]]
Re: [response to Call for Preliminary Proposals doc 15-08/0373r1]
Abstract: [Preliminary proposal to IEEE 802.15.4e for wireless sensor/actuator networks applicable for factory automation.]
Purpose: [amending 802.15.4-2006 for matching the requirements for factory automation]
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.
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 2
doc.: IEEE 802.15-0503r0
Submission
Preliminary Proposal for Factory Automation
Ludwig Winkel (Siemens AG)
Michael Bahr (Siemens AG)
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 3
doc.: IEEE 802.15-0503r0
Submission
Overview
• Support of factory automation and process automation
• Proposal for Factory Automation– Motivation– Proposed MAC solution
• Considerations for Process Automation– Mesh Support
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 4
doc.: IEEE 802.15-0503r0
Submission
Support of Process Automation and Factory Automation
• process automation (PA) and factory automation (FA) are related but quite inde-pendent use cases with different requirements
• use of same wireless communication technology (IEEE 802.15.4) is beneficial
• configurability of IEEE 802.15.4e– common base functionality– configurable for process automation use cases– configurable for factory automation use cases
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 5
doc.: IEEE 802.15-0503r0
Submission
MAC Proposal for Factory Automation
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 6
doc.: IEEE 802.15-0503r0
Submission
Use Cases of Factory Automation
• automotive– robots– suspension tracks– portable
• machine tools– milling, turning – robot revolver
• filling• cargo
– airport logistics– post
• packaging industry• special engineering• conveyor technique
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 7
doc.: IEEE 802.15-0503r0
Submission
Requirements and Assumptions
• high determinism• high reliability• low latency:
– transmission of sensor data in 10 ms
– low round-trip time
• many sensors per gateway– might be more than 100
sensors per gateway
• assume controlled envi-ronment (factory floor)
• configuration for optimal performance
• network management and frequency planning for avoidance of co-existence issues
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 8
doc.: IEEE 802.15-0503r0
Submission
Why IEEE 802.15.4?• coexistence with IEEE 802.11 WLAN
– 3 non-overlapping channels for IEEE 802.11– 4 channels for IEEE 802.15.4
• sufficient range• worldwide acceptance• worldwide standard
North America(similar worldwide)
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 9
doc.: IEEE 802.15-0503r0
Submission
Network Topology
• star topology• gateway• devices
– sensors:unidirectional data exchange from devices to gateway
– actuators: bidirectional data exchange between devices and gateway
Device
DeviceDevice
Device
Device
Device
Device
Gateway
Device
DeviceDevice
Device
Device
Device
Device
Gateway
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 10
doc.: IEEE 802.15-0503r0
Submission
General Concept
• IEEE 802.15.4 PHY frames• Time Division Multiple Access
– Superframe with timeslots of fixed length– shared group timeslots with CSMA– addressing based on timeslot location or
short address– modified MAC frame
• no channel hopping
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 11
doc.: IEEE 802.15-0503r0
Submission
PHY Frame Format
• IEEE 802.15.4 PHY frame format
• different preamble values– differentiate IEEE 802.15.4e FA devices
from other IEEE 802.15.4 devices
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 12
doc.: IEEE 802.15-0503r0
Submission
Time Division Multiple Access
• Superframe– starts with beacon– followed by n timeslots of equal, fixed length
• Timeslots– one device per timeslot (dedicated timeslot)– determinism
• (re-)synchronization through beacon– allows sleep mode / power save of devices
time slot
time
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 13
doc.: IEEE 802.15-0503r0
Submission
Shared Group Timeslots
• more than one device per timeslot• carrier sense multiple access within shared group timeslot• 1 or more continous timeslots concatenated to a shared group
timeslot• all timeslots in single shared group timeslot network with
carrier sense multiple access• mixture between fixed, deterministic timeslots and shared group
timeslots possible
time slot
time
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 14
doc.: IEEE 802.15-0503r0
Submission
Structure of Superframe
Zeit
Beacon TN 1 TN 2 TN 3 TN nBeacon TN 1 TN 2 TN 3 TN n
Zeit
... Sn A1 ... AnBeacon RX TX S1 S2
Management Slots Sensoren Aktoren
Superframe
• existence of management timeslots configurable during setup
• number of (timeslots for) sensors and actuators configurable during setup
sensors
time
actuators
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 15
doc.: IEEE 802.15-0503r0
Submission
PreambleFrame Length
SFD
FCSData Payload
PSDU
4 1
2
1Octets:
variable
MAC Layer
PHY Layer
MAC Frame Format
• implicit addressing through slot number– omits MAC header fields
• very short PSDU increases efficiency dramatically– turnaround time / latency main criteria– every bit counts:
• data payload is very short• assume 2 byte data payload • 3 more bytes mean a 30% increase in latency!
• FCS for error recognition
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 16
doc.: IEEE 802.15-0503r0
Submission
Transmission Modes
• 3 transmission modes– Discovery– Configuration– Online
• transmission mode is signalled in beacon
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 17
doc.: IEEE 802.15-0503r0
Submission
Discovery Mode
• first step in network setup (addition of new devices)• device sends its current configuration to gateway till ACK
G ateway Sensor/Actuator
M gm t S lo t
M gm t S lo t
Beacon
Beacon
S tart D iscover M ode
Synchron ize and prepare R esponse
Fram e that conta ins the current device
configurationD iscover R esponse Fram e
Tim e
Beacon
M gm t S lo t
M gm t S lo t
Beacon
M gm t S lo t
M gm t S lo t
Beacon
M gm t S lo t
M gm t S lo t
Beacon
...
R esynchron izesAck Fram e
R eceived a D iscover
R esponse Fram e;
prepare Ack
G ateway Sensor/Actuator
M gm t S lo t
M gm t S lo t
Beacon
Beacon
S tart D iscover M ode
Synchron ize and prepare R esponse
Fram e that conta ins the current device
configurationD iscover R esponse Fram e
Tim e
Beacon
M gm t S lo t
M gm t S lo t
Beacon
M gm t S lo t
M gm t S lo t
Beacon
M gm t S lo t
Beacon
...
R esynchron izesAck Fram e
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 18
doc.: IEEE 802.15-0503r0
Submission
Configuration Mode• second step in network setup• used for re-configuration of network• gateway sends new configuration to device
G ateway Sensor/Actuator
M gm t S lot
M gm t S lot
Beacon
Beacon
Tim e
Beacon
M gm t S lot
M gm t S lot
Beacon
BeaconBeaconResynchron izes
Received a Response
Fram e; create Configura tion
Request Fram e
G ateway Sensor/Actuator
M gm t S lot
M gm t S lot
Beacon
Beacon
S tart Configura tion
M odeSynchronize and
prepare a Response Fram e that conta ins the current device
configurationResponse Fram e
Tim e
Beacon
M gm t S lot
M gm t S lot
Beacon
BeaconBeacon
...
Resynchron izesConfigura tion Request Fram e
M gm t S lot
M gm t S lot
M gm t S lot
M gm t S lot
M gm t S lot
M gm t S lot
M gm t S lot
M gm t S lot
BeaconBeaconBeaconBeacon
M gm t S lot
M gm t S lot
M gm t S lot
M gm t S lot
M gm t S lot
M gm t S lot
M gm t S lot
M gm t S lot
BeaconBeacon
Received the Configura tion Request
w ith the new configuration; prepare Ack
Resynchron izesResynchron izes
Ack
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 19
doc.: IEEE 802.15-0503r0
Submission
Configurable Parameters
• structure of superframe (management timeslots, sensor timeslots, actuator timeslots)
• number of timeslots
• duration of timeslots
• shared group timeslots
• transmission channel
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 20
doc.: IEEE 802.15-0503r0
Submission
Online Mode
• transmission of the actual data for factory automation (productivity data)
• gateway acknowledges receipt of data from sensors in beacon
• gateway signals direction of transmission for actuator timeslots in beacon– transmission with or without acknowledgement or
with block acknowledgement
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 21
doc.: IEEE 802.15-0503r0
Submission
Use of Single Channel
• avoids „unproductive“ channel switch times
• allows addressing by timeslot• better support of roaming (e.g. conveyor
belts)• very good coexistence with other
wireless networks (e.g. WLAN on different channels)
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 22
doc.: IEEE 802.15-0503r0
Submission
Considerations on Process Automation
see also 15-08/409r2
July 2008
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doc.: IEEE 802.15-0503r0
Submission
Mesh Support
• applicable for process automation• IEEE 802.15.4 header extensions for mesh
support– additional addresses (source, destination)– sequence number– TTL („transmissions to live“)
• framework for chosing path selection mechanisms– path selection protocol– link metrics
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 24
doc.: IEEE 802.15-0503r0
Submission
Frame Forwarding
• received frames for other nodes are forwarded to the next hop according to aquired forwarding information
• frame forwarding capability required, realization implementation specific
July 2008
L. Winkel, M. Bahr, Siemens AGSlide 25
doc.: IEEE 802.15-0503r0
Submission
Summary
• configurable distinction between factory automation and process automation
• propose highly efficient TDMA-based MAC scheme for factory automation– IEEE 802.15.4 PHY– very short latency through short data packets in short
dedicated timeslots of fixed length– shared group timeslots– configurability
• mesh support for process automation