ZigBee/IEEE 802.15.4

1. ZigBee/IEEE 802.15.4

2. Origin Of Name ZigBee • The domestic honeybee, a colonial insect, lives in a hive that contains a queen, a few male drones, and thousands of worker bees. The survival, success, and future of the colony is dependent upon continuous communication of vital information between every member of the colony. The technique that honey bees use to communicate new-found food sources to other members of the colony is referred to as the ZigBee Principle. Using this silent, but powerful communication system, whereby the bee dances in a zig-zag pattern, she is able to share information such as the location, distance, and direction of a newly discovered food source to her fellow colony members. Instinctively implementing the ZigBee Principle, bees around the world industriously sustain productive hives and foster future generations of colony members.

3. What is ZigBee • ZigBee is a Ad-hoc networking technology for LR-WPAN • Based On IEEE 802.15.4 standard that defines the PHY and Mac Layers for ZigBee. • Intended for 2.45 Ghz , 868 Mhz and 915 Mhz Band. • Low in cost ,complexity & power consumption as compared to competing technologies. • Intended to network inexpensive devices • Data rates touch 250Kbps for 2.45Ghz ,40 Kbps 915Mhz and 20Kbps for 868Mhz band.

4. Bluetooth vs. ZigBee • Bluetooth (802.15.1) and ZigBee (802.15.4) have much in common. Both are types of IEEE 802.15 "wireless personal-area networks," or WPANs. Both run in the 2.4-GHz unlicensed frequency band, and both use small form factors and low power.

5. ZigBee Alliance

6. Worlds Most Common Frequency Bands

7. Market Requirements-I • Global licence free ISM band operation • Unrestricted geographic use • RF penetration through walls & ceilings • Automatic/semi-automatic installation • Ability to add or remove devices • Possible voice support

8. Market Requirements-II • 10k-115.2kbps data throughput • 10-75m coverage range (home/garden) • Support for 32-255 nodes • Support for 4 critical devices • 4-100 co-located networks • 0.5-2 year battery life • Up to 5m/sec. (18kmph) permitted mobility • Module cost: $1.5-$2.5 in 2004/5!

9. Home/Light Commercial spaces

10. Industrial Environment • Warehouses, Fleet management, Factory, Supermarkets, Office complexes • Gas/Water/Electric meter, HVAC • Smoke, CO, H2O detector • Refrigeration case or appliance • Equipment management services & Preventative maintenance • Security services • Lighting control • Assembly line and work flow, Inventory • Materials processing systems (heat, gas flow, cooling, chemical)

11. INDUSTRIAL & COMMERCIAL Application Sectors CONSUMER ELECTRONICS monitors sensors automation control TV VCR DVD/CD remote PC & PERIPHERALS PERSONAL HEALTH CARE ZigBee LOW DATA-RATE RADIO DEVICES TOYS & GAMES HOME AUTOMATION consolesportables educational security HVAC lighting closures

12. ZigBee Market Shares

13. ZigBee General Characteristics • Data rates of 20 kbps and up to 250 kbps • Star or Peer-to-Peer network topologies • Support for Low Latency Devices • CSMA-CA Channel Access • Handshaking • Low Power Usage consumption • 3 Frequencies bands with 27 channels • Extremely low duty-cycle (<0.1%)

14. BANDCOVERAGE DATA RATECHANNELS 2.4 GHz ISM Worldwide 250 kbps 16 915 MHz ISM Americas 40 kbps 10 868 MHz Europe 20 kbps 1 ZigBee Statistics

15. 868MHz/ 915MHz PHY Channels 1-10 Channel 0 2 MHz 868.3 MHz 902 MHz 928 MHz 2.4 GHz PHY Channels 11-26 5 MHz 2.4 GHz

16. Low Power Statistics • Today’s definition: Low power: Battery operation for several years • Some figures • 1 year is 365*24 hours = 8760 hours • AAA battery capacity is about 1300mAh • AA battery capacity is about 3100mAh • Coin cell lithium CR2032 capacity is about 230mAh • Note that peak current,(internal resistance) and leakage are also issues, but not today • An average consumption of 10uA will last • AAA:15 years, AA: 35 years and CR2032: 2.6 years

17. Comparison Chart

19. Bluetooth ZigBee Comparison fo PAN networks • ZigBee Protocol was developed to serve very different applications than Bluetooth and leads to tremendous optimizations in power consumption. Some of the key protocol differentiators are: • ZigBee: • Very low duty cycle, very long primary battery life, • Static and dynamic star and mesh networks, >65,000 nodes, with low latency available, • Ability to remain quiescent for long periods without communications, • Direct Sequence Spread Spectrum allows devices to sleep without the requirement for close synchronization. • Bluetooth: • Moderate duty cycle, secondary battery lasts same as master, • Very high QoS and very low, guaranteed latency, • Quasi-static star network up to seven clients with ability to participate in more than one network, • Frequency Hopping Spread Spectrum is extremely difficult to create extended networks without large synchronization cost.

20. Network coordinator Full Function node Reduced Function node Communications flow Virtual links Basic Network Charachteristics • 65,536 network (client) nodes • Optimized for timing-critical applications • Network join time: • 30 ms (typ) • Sleeping slave changing to active: 15 ms (typ) • Active slave channel access time: 15 ms (typ)

21. ZigBee Layers

22. Typical Implementation’s

23. What are the RAM/ROM requirements for the FFD and RFD MAC ? ZigBee requires a small amount of system resources substantially simplifying the process of designing wireless communications into products while reducing time to market and product cost. While still in the definition phase, the estimated MAC size is as follows: RFD = 12KB to 16KB FFD = 16KB to 20KB.

24. Device Addressing • All devices have IEEE addresses • Short addresses can be allocated • Addressing modes: • Network + device identifier (star) • Source/destination identifier (peer-peer) • Source/destination cluster tree + device identifier (cluster tree)

25. IEEE 802.15.4 Device Definitions • Full function device (FFD) • Any topology • Network coordinator capable • Talks to any other device • Reduced function device (RFD) • Limited to star topology • Cannot become a network coordinator • Talks only to a network coordinator • Very simple implementation

26. ZigBee Network Devices

27. Star and Peer to Peer Networks

28. Cluster Tree Network

29. Network Architecture

30. Types of PAN • Non-Beacon Enabled PAN Un-slotted CSMA/CA • Beacon Enabled PAN Slotted CSMA/CA

31. A superframe is formed by the PAN coordinator to synchronize network reception and transmission. SuperFrame Structures

32. Communication Mechanisms-I

33. Communication Mechanisms-II

34. PHY/MAC Framing

35. Network Layer

36. Robustness of Architecture • CSMA/CA • Frame Acknowledgement • Data Verification

37. Overview of 802.15.4 Security • The basic features provided by the link layer security protocol are • Access Control • Message Integrity • Message Confidentiality • Replay Protection

38. Access Control and Message Integrity • Unauthorized entities should not be part of a secure network • A mechanism to detect the above scenario • Message integrity – message tampering should be detected – MAC • Requires communicating parties to share a secret

39. Confidentiality • Means of achieving – encryption • Notion of “Semantic Security” • The encryption must prevent an adversary from learning even partial information about the message • This means that encryption of the same plaintext twice should result in different cipher texts • Nonce

40. Replay Protection • Adversary eavesdrops a message from a legitimate sender and replays it after a time delay ‘x’ • Sequence numbers – increased with every packet

41. 802.15.4 Stack LLC – Logical Link Control SSCS – Service Specific Convergence Sub layer

42. 802.15.4 Protocol • Each node has • 64 – bit Node ID • 16 – bit Network ID • (A node could use 16-bit Node ID) • Two types of packets (relevant to security) • Data • ACK (Sender explicitly requests it)

43. Data and ACK packet formats

44. Where is security ? • Handled by the Media access control layer • The application controls the security required • By default – “NO Security” • Four types of packets • Beacon, Data, ACK, Control packets for MAC Layer • NO Security for ACK packets • The other packets can optionally use encryption or integrity checks

45. Security Suites • No security – NULL • AES-CTR - Encryption only, CTR Mode • AES-CBC-MAC – MAC only (options of 32bit, 64bit and 128bit MAC’s) • AES-CCM – Encryption and MAC (options of 32bit, 64bit and 128bit MAC’s) • Replay protection can be turned on or off for any of the above

46. How does it work? • Application decides the choices on the security level. (A bool value) • Access Control Lists are used to enforce these security levels (max up to 255 entries) • If security is enforced then the MAC layer looks up the ACL table for the cryptographic material for the destination

47. Cont’d • On packet reception, based on the flags the MAC layer decides how to process the packet ACL Entry Format

48. Details of Security Suites • NULL – no security, mandatory in all chips • AES-CTR (Confidentiality alone) • Break plain text into 16-byte blocks p1,…,pn • Compute cipher text ci = pi xor Ek(xi) • CTR or Nonce xi is necessary for the receiver to decrypt

49. Nonce • Is made up of • Static flags field • Sender’s address • 3 counters • 4 byte frame counter (identifies the packet) • 1 byte key counter • 2 byte block counter (numbers the 16 byte blocks in a packet)

50. More on Nonce • Frame counter controlled by the hardware radio • Sender increments it after every packet • When reaches max value no further encryptions are possible • Key counter – application’s control • Used when frame counter has reached its max value • Goal of frame and key counter is to prevent nonce reuse (in a single key’s life-time) • Use of block counter • ensure different nonce’s are used for each block • need not be transmitted