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DECT for Industrial Communication Systems
Dr. Andreas MüllerDirector R&DHöft & Wessel AGRotenburger Str. 2030659 HannoverGERMANYFon: +49-511-6102-345Email: [email protected]
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
21/10/2009 2
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
21/10/2009 3
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
21/10/2009 5
• Some requirements on wireless systems in industrial applications
• The benefits and drawbacks of DECT technology in this context
Presentation Outline
21/10/2009 6
• 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
21/10/2009 7
• 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
21/10/2009 8
• 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
21/10/2009 9
• 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
21/10/2009 10
• 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
21/10/2009 11
• 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
21/10/2009 12
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
21/10/2009 13
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
21/10/2009 14
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
21/10/2009 15
√ 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
21/10/2009 16
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
21/10/2009 17
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
21/10/2009 18
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
21/10/2009 19
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
21/10/2009 20
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
21/10/2009 21
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
21/10/2009 22
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
21/10/2009 23
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
21/10/2009 24
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
21/10/2009 25
• 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
21/10/2009 26
• Point-to-multipoint system
• Easy interfacing to Ethernet
• Voice and data sharing the same infrastructure