DECT for Industrial Communication Systems

Dr. Andreas MüllerDirector R&DHöft & Wessel AGRotenburger Str. 2030659 HannoverGERMANYFon: +49-511-6102-345Email: am@hoeft-wessel.de

ETSI Wireless Factory Starter Group20-21 October 2009ETSI, Sophia Antipolis, France

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

At a glance

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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

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

Business model

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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

skeye.pad XSLskeye.integralskeye.allegro skeye.integral UHFskeye.dart skeye.allegro LS

Product portfolio

4

almex.station almex.express almex.compact almex.optima

almex.optima cl

metric.aura metric.accent

12 years history in DECT based data communication

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• Some requirements on wireless systems in industrial applications

• The benefits and drawbacks of DECT technology in this context

Presentation Outline

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• The CLDPS extension of DECT

- Motivation

- Basic concepts

- Features

• Highly reliable transmission

• Well-defined (and short enough!) end-to-end delay

• Sufficient data throughput

Some requirements from industry

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• Suited for bus architectures (1 master, n slaves)

• Easy interfacing to Ethernet

• Voice and data sharing the same infrastructure

• Highly reliable transmission

√ Exclusive frequency band

√ Designed for coexistence

√ Good immunity against multipath

• Well-defined (and short enough!) response time

Benefits and drawbacks of DECT technology

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• 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

• Suited for bus architectures (1 master, n slaves)

√ DECT has a similar architecture (1 FT, n PT)

• Easy interfacing to Ethernet

- No standardized interworking

Benefits and drawbacks of DECT technology

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• Voice and data sharing the same infrastructure

√ DECT is the predominant cordless telephony system

• To overcome the drawbacks of connection oriented DECT

without losing its benefits

• Packet data service

√ no connection setup needed

CLDPS – ConnectionLess DECT Packet Service

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• More flexibility in using the DECT multiplex frame

√ Higher data throughput

√ More active endpoints

• Fully interoperable with conventional DECT

• Ethernet interworking added

• 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

CLDPS – System Architecture

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• Communication always involves the FT

FT

PT

PT

PT

PT

CLDPS – slot formats

0 2 4 6 8 10 12 14 16 18 20 22

DECT Frame: 10ms

Full Slot416,7µs

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Double Slot

Long Slot694,4µs

833,3µs

CLDPS – System Architecture

clDL

clDL O-SAP clDL Px-SAPs

clDL P1-SAP

ETH IWU

clDL

clDL O-SAP clDL Px-SAPs

clDL P1-SAP

ETH IWU

FTFTPT

OclDL messages

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DECT PHY

clMAC

clDL

D-SAP

clMAC O-SAP clMAC P-SAP

DECT PHY

clMAC

clDL

D-SAP

clMAC O-SAP clMAC P-SAP

other PTs

OclMAC messages

OclDL messages

CLDPS – System Architecture

OclDL messagesSegmentation

clDL O-SAPclDL Px-SAPs clDL P1-SAP

clDL

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OclMAC messagesArbitration

DECT D-SAP

clMAC O-SAPclMAC P-SAP

clMAC

• Extension of DECT MAC Layer

• Using Connectionless Bearer frame structures of DECT

• Defining new connectionless procedures

√ for avoiding collisions

CLDPS – clMAC Layer

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√ for avoiding collisions

√ for improving coexistence with other DECT systems

√ for providing fast and reliable media access

CLDPS – Basic Ideas: Compatible Time/Frequency Multiplexing

Sl 0 Sl 2 Sl 4 Sl 6 Sl 8 Sl 10 Sl 12 Sl 14 Sl 16 Sl 18 Sl 20 Sl 22F 0F 1 Down UpF 2F 3 Down UpF 4 Down UpF 5F 6F 7F 8F 9 Down Down Up Up

DECT

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Sl 0 Sl 2 Sl 4 Sl 6 Sl 8 Sl 10 Sl 12 Sl 14 Sl 16 Sl 18 Sl 20 Sl 22F 0F 1 Up/Dn Up/DnF 2F 3 Up/Dn Up/DnF 4 Up/Dn Up/DnF 5F 6F 7F 8F 9 Up/Dn Up/Dn Up/Dn Up/Dn

CLDPS

CLDPS – Basic Ideas: Multiplex controlled by FT

Sl 0 Sl 2 Sl 4 Sl 6 Sl 8 Sl 10 Sl 12 Sl 14 Sl 16 Sl 18 Sl 20 Sl 22F 0F 1 UFT UPTF 2F 3 UFT UPTF 4 MPT MPTF 5F 6F 7F 8F 9 UPT BC UFT UFT

Frame k

Sl 0 Sl 2 Sl 4 Sl 6 Sl 8 Sl 10 Sl 12 Sl 14 Sl 16 Sl 18 Sl 20 Sl 22F 0

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F 0F 1 UFT UFTF 2F 3 UFT UPTF 4 MPT MPTF 5F 6F 7F 8F 9 UPT BC MFT UPT

Frame k+1

Slot Modes

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

• Extension of DECT Dummy Bearer (A-field same as Dummy Bearer)

• B-field contains Arbitration information for the next following frame:

CLDPS – Beacon

Bit/

Byte

7 6 5 4 3 2 1 0

1 BC Slot RfChn BC

2 MPT Slot RfChn MPT

3 Cry 0 Mode 0 RfChn 0

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4 PtAddr 0

... ...

19 Cry 8 Mode 8 RfChn 8

20 PtAddr 8

21

OclMAC / Padding...

38

39 FCS high

40 FCS low

CLDPS – organisation messages: OclMAC blocks

Bit/

Byte

7 6 5 4 3 2 1 0

1 BType BLen

2

OclMAC payload...

BLen+1

BType Channel Direction FT -> PT Direction PT -> FT

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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

CLDPS – FT transmit procedure

clMAC_PchnSend_REQ

TX request clMAC-P chn

clDL clMAC clMAC clDL

PT FT

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clMAC_PchnData_REQ

clMAC_PchnSend_CFM

update PDU, if necessary

clMAC_PchnData_IND

Multicast oder Unicast FT Slot

RXclMAC-P chn

Beacon

Arbitration

CLDPS – PT transmit procedure

clDL clMAC clMAC clDL

PT FT

clMAC_PchnSend_REQ

TX request clMAC-P chn

RTS Procedure

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BeaconArbitration

clMAC_PchnData_REQ

clMAC_PchnSend_CFM

update PDU,if necessary

clMAC_PchnData_IND

Unicast PT Slot

RXclMAC-P chn

• 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%

CLDPS – RTS Procedure

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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

• 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

CLDPS – clDL-P1 Channel

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PHeader SDU data FCS SDU data FCS

PHeader SDU data FCS SDU data FCS SDU data FCS SDU data FCS

PHeader SDU data FCS SDU data FCS SDU data FCS SDU data FCS SDU data FCS

Full Slot

Long Slot

Double Slot

B-fieldA-field

CLDPS – clDL-P1 channel: A-field format

Bit/

Byte

7 6 5 4 3 2 1 0

1 ESC (101) PFlag RTS/CTS

2 PtAddr

3 PxType (001) Last NWKProt

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3 PxType (001) Last NWKProt

4 First TSeqNum

5 CellCnt LenF NAKcnt

6 Last RSeqNum

• 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

CLDPS – Data rate considerations

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• Due to deterministic multiplexing channel capacity can be fully used

even when shared among many PTs

• CLDPS is a useful extension of DECT

• Compatibility to existing DECT systems

• High data rate, low latency

Conclusion

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• Point-to-multipoint system

• Easy interfacing to Ethernet

• Voice and data sharing the same infrastructure