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:[ludwig.winkel@siemens.com]

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

L. Winkel, M. Bahr, Siemens AGSlide 23

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