ISO/IEC , CSD, IEEE a. Embedded Systems Lab. Dept. of CSE, PNU

Transcription

1 ISO/IEC , Embedded Systems Lab. Dept. of CSE, PNU

2 Schedule 주제 일정 Chapter 2. Transmission fundamentals 1/29 Chapter 6. Signal encoding techniques 2/5 ISO/IEC , 2/8 Wireless Sensor Network 2/19 RFID (Radio Identification) 2/22 2

3 Contents Introduction ISO/IEC CSD Physical layer Data Link layer Tag collection and arbitration CSD system Encryption CSD requirement IEEE a Physical layer MAC sub-layer Summary Reference 3

4 Introduction Three standards ISO/IEC CSD IEEE a ISO/IEC CSD 433MHz wireless communication Container security IEEE a WPAN Revision IEEE

5 ISO/IEC Features 433Mhz band used Active RF tag RFID system defined by ISO/IEC Identify tag in range Read data / Write data Selection by group or address Handling of multiple tags in the field of view Error detection RFID equipment Interrogator Tag 5

6 Physical layer Typical characteristics Characteristic Carrier frequency Modulation type Frequency deviation Modulation rate Value MHz FSK +/- 50KHz 27.7KHz Wake up signal Figure 1. ISO/IEC characteristic Transmitted by the interrogator Minimum 2.4s, maximum 4.8s All tags within communication range shall enter into Ready state 6

7 Data link layer Packet format Preamble Data byte Final logic low Figure 2. ISO/IEC packet format Preamble 60 μs period twenty pulse 30 μs high, 30 μs low Final synchronization pulse Tag to interrogator 42 μs high, 54 μs low Interrogator to tag 54 μs high, 54 μs low Figure 3. ISO/IEC preamble 7

8 Data link layer (cont d) Data byte format Manchester code 8 data bit, 1 stop bit 36 μs period, total 324 μs period CRC bytes Calculated as a 16bit value Initialized 0x0000 All data bytes according to CCITT polynomial Excluding preamble Appended to the data as two bytes Packet end period Final period 36 μs of continuous logic low Figure 4. ISO/IEC data byte 8

9 Tag collection & arbitration Figure 5. ISO/IEC collection sequence and timing 9

10 Tag collection & arbitration (cont d) Tag arbitration mechanism Allocate tag reply transmissions into time slot Within a time window, Listen Period (LP) LP are contained within Collection Period (CP) WP CP(1) CP(2) CP(p) SP(p) LP(p) AP(p) TS(p,1) TS(p,2) TS(p, Dp) AP(p,1) AP(p,2) AP(p, Dp) Figure 6. ISO/IEC anti collision scheme timing diagram 10

11 Tag collection & arbitration (cont d) Tag arbitration mechanism (cont d) Begins when interrogator transmit a collection command Tag selects at random a slot in which it will reply Set slot size Set the maximum number of slots Select a time lost TS(n) in which to reply in range of 1 to D Transmit its reply when it has waited for TS(n) * (Slot Size 1) Slot size = tag reply packet length + 2 ms Number of slots = (Window Size * 57.3 ms ) / slot size When the LP is finished, interrogator transmit a Sleep command If further data is be read from the tag, transmit Read Universal Data Block command During CP, interrogator senses that how many collisions occurred If too many, increase window size else decrease window size 11

12 CSD CSD (Conveyance Security Device) Security device which set up in container CSD standardization document CSD Requirement Document CSD-to-CSD Reader Interface Control Document CSD-to-DCP Interface Control Document SHHR Requirement Document DCP Requirement Document 12

13 CSD system Purpose Monitor for intrusion through the cargo loading doors Support shipping security from POA (Point of Arming) ITP (Intermediate Transit Points) TTP (Trip Termination Point) System component CSD SHHR CSD Reader Fixed Reader SHHR (Secured Hand-Held Reader) DCP (Data Consolidation Point) RF IP DCP Fixed Reader Figure 7. CSD system component 13

14 CSD system (cont d) CSD Purpose Monitor the security stats of the container door Functions Fixed Reader Compose IEEE b star topology with CSD reader Creates an event log of all relevant events Encryption / Decryption (AES128, HMAC-SHA256) After arming, save all data If deactivated state, don t save Functions Compose IEEE b star topology with CSD Communicate DCP via TCP/IP 14

15 CSD system (cont d) SHHR DCP Hand-held device Used by DHS authorized security agent Agent can unlimitedly access CSD data CSD command Data Consolidation Point Functions Exist web server Retain CSD information Management encryption key Communicate CSD Reader(Fixed, SHHR) via TCP/IP AES128, HMAC-SHA256 encryption/decryption 15

16 CSD system (cont d) Figure 8. CSD system data flow 16

17 Encryption Encryption key Vendor provides to DHS DHS mange keys at DCP SHHR download keys form DCP Each CSD have an unique encryption key Figure 9. CSD system encryption 17

18 CSD requirement Functional requirement CSD perform various functions upon valid commands Status sensing requirements CSD shall report the door status as either open or closed CSD shall monitor at least at a rate of 1 sample per second Power requirements CSD power source shall have sufficient power for the duration of a trip Figure 10. CSD state transition diagram 18

19 IEEE a IEEE Framework for low data rate communications systems Typically sensor network ZigBee IEEE a Revision IEEE New options for physical layer Higher data rate Accurate ranging capability New Physical layer features on MAC 19

20 Physical layer Based on two different technologies UWB (Ultra Wide Band) Chirp signals UWB signal a uses three frequency bands Sub-GHz band, low band in 3-5 GHz range high band in 6-10 GHz range Compliant device must support channel 0, 3, 9 for sub-ghz Characterized by bandwidth of about 500MHz Ranging with an accuracy in the order of 1 meter Figure 11. Channelization scheme in IEEE a 20

21 Physical layer (cont d) UWB physical layer Data bits are mapped on PPM (Pulse Position Modulation) Devices compliant to the standard PAM (Pulse Amplitude Modulation) Optional PPM vs. PPM & PAM UWB physical layer can achieve 0.1 Mb/s and 26 Mb/s Chirp signal Advantage of working in the 2.4 GHz ISM band 14 channels spaced of 5 MHz Frequency range between 2410 and 2486 MHz Can achieve at most 1 Mb/s 21

22 MAC sub-layer Inherits IEEE strategy ALOHA Beacon-enabled Only when the PAN has a star topology Non-beacon-enabled Suited for PANs adopting the peer-to-peer topology But can be adopted in a start network Adopting a Time Hopping scheme Different delay on each burst in a packet Thus further reducing the probability of packet loss due to collisions CSMA-CA kept as options UWB - Address high-density, high-traffic scenarios Enable the use of the Chirp physical layer 22

23 Summary ISO/IEC CSD 433Mhz band used Tag arbitration mechanism CSD system IEEE a UWB, Chirp ALOHA 23

24 References Papers Luca De Nardis and Maria-Gabriella Di Benedetto, Overview of the IEEE /4a standards for low data rate Wireless Personal Data Networks, WPNC, Hannover, Germany, 2007, pp Manual ISO/IEC FDIS , 2006 CONVEYANCE SECURITY DEVICE(CSD) REQUIREMENTS BASELINE VERSION 1.2, 2007 IEEE P a/D7, 2007 Websites er7_%ec%b5%9c%ec%a2%85.pdf 24