A Comprehensive Study of ZigBee. Presented by Dr. K F Tsang Citycom Technology Ltd. Tel:

Transcription

1 A Comprehensive Study of ZigBee Presented by Dr. K F Tsang Citycom Technology Ltd. Tel: ee330015@cityu.edu.hk 1 1

2 Outline Introduction of ZigBee Market analysis Characteristics of ZigBee Reliability and Robustness of ZigBee Potential Application of ZigBee Product certification Conclusion 2 2

3 Part I: Basics of ZigBee 3 3

4 Introduction of ZigBee 4 4

5 What is ZigBee? Introduction Standard for short distance wireless communication Developing on IEEE standard ZigBee Alliance response to promote ZigBee 5 5

6 Membership Classes Promoters founding members of ZigBee, who form the Board of Directors. There are currently 5 promoters + 1 chairperson Participants members who generally wish to make technical contributions and/or serve on the Technical Group committees. These members have early access to specifications, and they may also chair working group subcommittees. They are in a position to help shape the ZigBee technology for industrial applications and the connected home. 6 6

7 Promoters ZigBee Alliance Participants And more each month 7 7

8 History Proposals Initial MRD RSI/TRD v0.2 Proposal to IEEE ZigBee Alliance formed ZigBee PAR Proposals IEEE Reviews Stand. Complete 8 8

9 The 802 Wireless Space WWAN IEEE Range WMAN WLAN WPAN ZigBee Bluetooth IEEE WiMax IEEE WiFi a c Data Rate (Mbps) 9 9

10 Stack Reference Model End developer applications, designed using application profiles ZA1 ZA2 ZAn IA1 IAn Application interface designed using general profile API UDP Topology management, MAC management, routing, discovery protocol, security management Channel access, PAN maintenance, reliable data transport Transmission & reception on the physical radio channel ZigBee NWK IEEE MAC (CPS) IEEE PHY IP LLC MAC (SSCS) 10 10

11 Protocol Stack Features Microcontroller utilized Full protocol stack <32 k Simple node-only stack ~4k Coordinators require extra RAM Node device database Transaction table Pairing table APPLICATIONS APPLICATION INTERFACE SECURITY NETWORK LAYER Star/Cluster/Mesh MAC LAYER MAC LAYER PHY LAYER 2.4 GHz 915MHz 868 MHz Application ZigBee Stack Customer IEEE ZigBee Alliance Silicon 11 11

12 Market analysis 12 12

13 Characteristic of ZigBee IEEE and ZigBee 13 13

14 The ZigBee Platform Public Application Profile Certified Product ZigBee Stack IEEE Compliant Platform 14 14

15 The ZigBee Platform Private Application Profile ZigBee Stack IEEE Compliant Platform 15 15

16 Basic Radio Characteristics ZigBee technology relies upon IEEE , which has excellent performance in low SNR environments 16 16

17 Basic Network Characteristics 65,536 network (client) nodes Optimized for timing-critical applications and power management Time to Join Network: <30ms Sleeping to active: <15ms Channel access time: <15ms Full Mesh Networking Support Network coordinator Full Function node Reduced Function node Communications flow Virtual links 17 17

18 ZigBee Network Topologies Mesh Star Cluster Tree PAN coordinator Full Function Device Reduced Function Device 18 18

19 Cluster Tree Networks Cluster tree networks enable a peerpeer network to be formed with a minimum of routing overhead CH1 CH2 CH4 8 DD/CH CH CH Parent Child CH6 Links indicate familial relationship, not communications capability 19 19

20 Cluster Tree Networks Employ multi-hop routing Can be very large: 255 clusters of 254 nodes each = 64,770 nodes May span physically large areas Suitable for latency-tolerant applications 20 20

21 ZigBee Device Types ZigBee Coordinator (ZC) One and only one required for each ZB network. Initiates network formation. Acts as PAN coordinator (FFD). May act as router once network is formed. ZigBee Router (ZR) Optional network component. May associate with ZC or with previously associated ZR. Acts as coordinator (FFD). Participates in multihop routing of messages. ZigBee End Device (ZED) Optional network component. Shall not allow association. Shall not participate in routing

22 Network Structure 22 22

23 Network Structure 23 23

24 Network Structure 24 24

25 Reliability and Robustness of ZigBee 25 25

26 Reliability Consistently performing a given task to the desired result despite all changes of environmental behavior Without failure A necessary ingredient of trust When the sensor measures its environment; the controller always measures the same value 26 26

27 Reliability The wireless medium is not a protected environment like the wired medium, but rather, it is fraught with degradations, disruptions, and pitfalls such as dispersion, multipath, interference, frequency dependent fading, sleeping nodes, hidden nodes, and security issues

28 Reliability In addition to the previous disruptions there is the case of sending messages to devices that are not receiving, e.g. they re in the sleep mode. When this happens the message needs to be buffered by another device that is able to send the message when the sleeping device wakes up

29 Reliability IEEE has built upon the successes of previous IEEE 802 standards by selecting those mechanisms proven to ensure good reliability without seriously degrading system and device performance

30 ISO Layers: Reliability PHY: Direct Sequence with Frequency Agility (DS/FA) MAC: ARQ, Coordinator buffering Network: Mesh Network (redundant routing) Application Support Layer: Security 30 30

31 Reliability PHY Layers: Direct sequence: allows the radio to reject multipath and interference by use of a special chip sequence. The more chips per symbol, the higher its ability to reject multipath and interference. Frequency Agility: ability to change frequencies to avoid interference from a known interferer or other signal source

32 IEEE 802 Direct Sequence IEEE b 15.4 (900) 15.4 (2.4) Chips/S ymbol As can be seen from above, IEEE /ZigBee has more processing gain (chips/symbol) than its predecessors 32 32

33 Direct Sequence and Frequency Agility Interferer Desired Signal Over the Air After DS correlation 2.4 GHz PHY Channels MHz 2.4 GHz GHz 33 33

34 Robustness Let s define robustness as the ability to tolerate significant degrading phenomena in the physical medium Multipath and interference are probably the most significant degradations to the channel model

35 Robustness Frequency hopping is a method that allows the radio to periodically change channels to over time minimize the effect of a bad channel. While this technique is very effective in some circumstances it creates other problems such as latency, network uncertainty for sleeping nodes, loss of the product bandwidth x time, etc

36 Robustness Direct Sequence with Frequency Agility (DS/FA) combines the best features of DS and FH without most of the problems caused by frequency hopping because frequency changes aren t necessary most of the time, rather they re appropriate only on an exception basis

37 Robustness Excess robustness does not achieve higher performance, rather it typically costs performance 37 37

38 Potential Applications 38 38

39 Applications 39 39

40 Home Network of Future Marketing 40 40

41 Part II Certification 41 41

42 ZigBee Alliance Goals Achieving interoperability of end products, where appropriate, is a key goal of the ZigBee Alliance. The Alliance is developing a Certification program as a means of ensuring such interoperability

43 ZigBee Certified Products An end product may be certified for either Interoperability with other ZigBee end products; or Operating within a closed system but able to coexist with other ZigBee products

44 Application Profiles Application Profiles define compatible sets of devices for specific market areas. The ZigBee Alliance s Application Framework Working Group (AFG) is defining and standardizing Application Profiles for many application segments. Profile Task Groups within AFG are charged with the profile definition and standardization task for specific application segments

45 Who Certifies? The ZigBee Alliance has appointed two independent test service providers to conduct certification testing. These companies are National Technical Systems (NTS) and TUV Rheinland. The ZigBee Alliance provides administrative support, and issues Certifications upon successful test program completion at either NTS or TUV

46 Finding Out More The Alliance is member driven. This is also true for the testing and certification aspects. Join the ZigBee Alliance. Get the existing test plans. Help expand and improve upon them by participating in the ZigBee Qualification Working Group

47 Contact Dr. K F Tsang Citycom Technology Ltd. Tel: ee330015@cityu.edu.hk 47 47

48 The END 48 48