DECT for Industrial Communication Systems Dr. Andreas Müller Director R&D Höft & Wessel AG Rotenburger Str. 20 30659 Hannover GERMANY Fon: +49-511-6102-345 Email: [email protected]

ETSI Wireless Factory Starter Group 20-21 October 2009 ETSI, Sophia Antipolis, France

At a glance German IT hardware and software specialist Headquarters

Hanover, Germany

Hardware

Mobile terminals, ticketing systems, check-in and checkout terminals, point-of-sale systems, data communication modules, parking ticket machines and parking space systems

Software

System und application software, including complex back-office und telematics solutions

Business units (sectors)

Almex (Public Transport), Metric (Parking), Skeye (Retail & Logistics)

Regions

Europe and USA

Foundation

1978, listed on the stock exchange since 1998

Turnover

EUR 98.1 million

Operating result before depreciation / amortisation

EUR 9.6 million (EBITDA)

Employees

502

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Business model Costumer focus

Customized products based on open IT platforms Turn-key solutions Project oriented business approach with industry customers Direct sales and account management Skilful maintenance team

Research & Development

Hardware and software competence, system and application level 170 highly qualified engineers and IT specialists

Internationalisation

Focus on Europe and USA Branch offices in UK, Italy, US

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Product portfolio

skeye.dart

skeye.allegro

skeye.allegro LS

skeye.integral

skeye.pad XSL

skeye.integral UHF

almex.optima cl

almex.station

almex.express

almex.compact

almex.optima

metric.accent

metric.aura

4

12 years history in DECT based data communication

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Presentation Outline

• Some requirements on wireless systems in industrial applications • The benefits and drawbacks of DECT technology in this context • The CLDPS extension of DECT -

Motivation

-

Basic concepts

-

Features

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Some requirements from industry

• Highly reliable transmission • Well-defined (and short enough!) end-to-end delay • Sufficient data throughput • Suited for bus architectures (1 master, n slaves) • Easy interfacing to Ethernet • Voice and data sharing the same infrastructure

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Benefits and drawbacks of DECT technology

• Highly reliable transmission √ Exclusive frequency band √ Designed for coexistence √ Good immunity against multipath • Well-defined (and short enough!) response time √ Time-division multiplex - Long connection setup times (>50 ms) • Sufficient data throughput √ System data rate 10 Mbit/s - Connection data rate only 32 kbit/s

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Benefits and drawbacks of DECT technology

• Suited for bus architectures (1 master, n slaves) √ DECT has a similar architecture (1 FT, n PT) • Easy interfacing to Ethernet - No standardized interworking • Voice and data sharing the same infrastructure √ DECT is the predominant cordless telephony system

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CLDPS – ConnectionLess DECT Packet Service

• To overcome the drawbacks of connection oriented DECT without losing its benefits • Packet data service √ no connection setup needed • More flexibility in using the DECT multiplex frame √ Higher data throughput √ More active endpoints • Fully interoperable with conventional DECT • Ethernet interworking added

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CLDPS – System Architecture • Cell-based system • Each cell has 1 FT (Fixed Termination) and up to 255 PTs (Portable Terminations) • The FT fulfils cell management functions • A PT is identified by a PtAddr (8 bits) which is dynamically assigned when it enters a cell • Communication always involves the FT

PT PT FT PT

PT 21/10/2009

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CLDPS – slot formats DECT Frame: 10ms 0

Full Slot

Long Slot

Double Slot

2

4

6

8

10 12 14 16 18 20 22

416,7µs

694,4µs

833,3µs

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CLDPS – System Architecture

PT

FT

ETH IWU

ETH IWU clDL P1-SAP

clDL O-SAP

clDL P1-SAP

clDL Px-SAPs

clDL clMAC O-SAP

clDL O-SAP

clDL

OclDL messages clMAC P-SAP

clMAC

clDL Px-SAPs

clMAC O-SAP

OclMAC messages

D-SAP

clMAC P-SAP

clMAC D-SAP

DECT PHY

DECT PHY other PTs

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CLDPS – System Architecture

clDL Px-SAPs

clDL P1-SAP

clDL O-SAP

Segmentation

OclDL messages

clDL clMAC O-SAP

clMAC P-SAP

OclMAC messages

Arbitration

clMAC DECT D-SAP

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CLDPS – clMAC Layer

• Extension of DECT MAC Layer • Using Connectionless Bearer frame structures of DECT • Defining new connectionless procedures √ for avoiding collisions √ for improving coexistence with other DECT systems √ for providing fast and reliable media access

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CLDPS – Basic Ideas: Compatible Time/Frequency Multiplexing Sl 0 F F F F F F F F F F

0 1 2 3 4 5 6 7 8 9

F F F F F F F F F F

0 1 2 3 4 5 6 7 8 9

Sl 2

Sl 4

Sl 6

Sl 8

Sl 10

Down

Sl 12

Sl 14

Sl 16

Sl 18

Sl 22

Up Down

DECT

Up

Down

Up

Down Down

Sl 0

Sl 20

Sl 2

Sl 4

Sl 6

Sl 8

Sl 10

Up/Dn

Sl 12

Sl 14

Sl 16

Sl 18

Up

Up

Sl 20

Sl 22

CLDPS

Up/Dn Up/Dn

Up/Dn

Up/Dn

Up/Dn

Up/Dn Up/Dn

Up/Dn Up/Dn

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CLDPS – Basic Ideas: Multiplex controlled by FT Sl 0 F F F F F F F F F F

0 1 2 3 4 5 6 7 8 9

F F F F F F F F F F

0 1 2 3 4 5 6 7 8 9

Sl 2

Sl 4

Sl 6

Sl 8

Sl 10

UFT

Sl 12

Sl 14

Sl 18

Sl 20

Sl 22

UPT UFT

UPT

MPT

Sl 0

Sl 16

Sl 2

Frame k

MPT

Sl 4

Sl 6

UPT

BC

Sl 8

Sl 10

UFT

Sl 12

Sl 14

Sl 16

Sl 18

UFT

UFT

Sl 20

Sl 22

UFT UFT

Frame k+1

UPT

MPT

MPT

UPT

BC

MFT

UPT

Slot Modes Beacon (BC), Unicast PT (UPT), Unicast FT (UFT), Multicast PT (MPT), Multicast FT (MFT)

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CLDPS – Beacon • Extension of DECT Dummy Bearer (A-field same as Dummy Bearer) • B-field contains Arbitration information for the next following frame: Bit/ Byte

7

6

5

4

3

2

1

1

BC Slot

RfChn BC

2

MPT Slot

RfChn MPT

3

Cry 0

Mode 0

RfChn 0

4

PtAddr 0

...

...

19 20

Cry 8

0

Mode 8

RfChn 8 PtAddr 8

21 ...

OclMAC / Padding

38 39

FCS high

40

FCS low

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CLDPS – organisation messages: OclMAC blocks Bit/ Byte

7

6

1

5

4

3

BType

2

1

0

BLen

2 OclMAC payload

... BLen +1

BType

Channel

Direction FT -> PT

Direction PT -> FT

0000

OclMAC message

Static system information / end marker

0001

Dynamic system info

RFU

0010

CTS Indication

RFU

0011

Registration CFM

Registration REQ

0100 – 0110

RFU

RFU

0111

OclDL message

clDL-P1 ACK

1000 – 1011

clDL O-SAP

Transparent (defined by higher layers)

1100 1111

RFU

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CLDPS – FT transmit procedure

PT clDL

FT clMAC

clMAC

clDL

clMAC_PchnSend_REQ

TX request clMAC-P chn

Arbitration Beacon clMAC_PchnSend_CFM

clMAC_PchnData_REQ

update PDU, if necessary

Multicast oder Unicast FT Slot clMAC_PchnData_IND RX clMAC-P chn

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CLDPS – PT transmit procedure

PT clDL TX request clMAC-P chn

FT clMAC

clMAC

clDL

clMAC_PchnSend_REQ RTS Procedure

Beacon

Arbitration

clMAC_PchnSend_CFM update PDU, if necessary

clMAC_PchnData_REQ Unicast PT Slot clMAC_PchnData_IND RX clMAC-P chn

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CLDPS – RTS Procedure • MPT slots are accessed through CSMA-CA • Collision avoidance technique assures low residual collision probability • There is a price to pay: 30ms access latency to MPT channel (no load condition) • Load scenario: 100 PTs each transmitting randomly 1 MPT slot per second. Channel occupancy: 50% Collision probability without CSMA-CA: 39,1% Residual collision probability: 2,8% Average access latency: 42 ms • When the number of PTs in a cell is small, the FT can help reduce channel access latency by active polling of PTs • When the higher layer protocol is initiated from FT side (typical for bus protocols), then there is no latency in channel access

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CLDPS – clDL-P1 Channel

• SDU is segmented into cells of 18 bytes payload + 2 bytes FCS • A-field is used to carry PDU header • B-field is used to carry cells

Full Slot

PHeader

SDU data

FCS

SDU data

FCS

Long Slot

PHeader

SDU data

FCS

SDU data

FCS

SDU data

FCS

SDU data

FCS

Double Slot

PHeader

SDU data

FCS

SDU data

FCS

SDU data

FCS

SDU data

FCS

A-field

SDU data

B-field

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FCS

CLDPS – clDL-P1 channel: A-field format

Bit/ Byte

7

6

1

5

ESC (101)

2 3 4

3

PFlag

2

1

0

RTS/CTS

PtAddr PxType (001) First

5 6

4

NWKProt TSeqNum

CellCnt Last

Last

LenF

NAKcnt

RSeqNum

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CLDPS – Data rate considerations

• Maximum data rate 648 kbit/s with double slots in unidirectional traffic • Maximum data rate 460 kbit/s with long slots and 57,6 kbit/s return channel • Due to deterministic multiplexing channel capacity can be fully used even when shared among many PTs

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Conclusion

• CLDPS is a useful extension of DECT • Compatibility to existing DECT systems • High data rate, low latency • Point-to-multipoint system • Easy interfacing to Ethernet • Voice and data sharing the same infrastructure

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