ZigBee Overview Modified from -Adams 2003: -http://www.zigbee.org/resources/documents/Adams- Heile_SensorsExpo_AnaheimSept03_V1_000.ppt -Adams 2004: -http://www.zigbee.org/resources/documents/IWAS_presenta tion_Mar04_Designing_with_802154_and_zigbee.ppt -Karayanis (2003) -“Emerging Wireless Standards, Understanding the Role of IEEE 802.15.4 & ZigBee™ in AMR & Submetering,” AMRA 2003 International Symposium. Copyright 2002 The ZigBee Alliance, Inc. Low Data Rate Wireless Evolution First Stage Second Stage Third Stage ……… 2002 2003 2004 2005 2006 2007 2008 2009+ Proprietary Dominates Proprietary Fades Standards Dominate IEEE 802.15.4 Emerges ZigBee Emerges IEEE 1451.5 Emerges System Integrator Focus Semiconductor Focus OEM Focus Leading Edge OEMs Early Adopter OEMs Wireless Ubiquitous $.1 - $1B Industry $1 - $10B Industry $10 - $100B+ Industry $1,000 - $100 Unit Cost $100 - $10 Unit Cost $10 - $1 Unit Cost Mapping Your Future: From Data to Value AMRA 2003 International Symposium Wireless Networking Standards Market Name GPRS/GSM Wi-Fi™ Bluetooth™ ZigBee™ Standard 1xRTT/CDM 802.11b 802.15.1 802.15.4 A Wide Area Web, Cable Application Monitoring Voice & Email, Replaceme Focus & Control Data Video nt System 4KB - 16MB+ 1MB+ 250KB+ Resources 32KB Battery Life 100 - 1-7 .5 - 5 1-7 (days) 1,000+ 255 / Network Size 1 32 7 65,000 Bandwidth 64 - 128+ 11,000+ 720 20 - 250 (KB/s) Transmission Range 1,000+ 1 - 100 1 - 10+ 1 - 100+ (meters) Mapping Your Future: From Data to Value Cost, Reliability, Success Speed, Reach,AMRA 2003 International Symposium Convenienc Power, Metrics Quality Flexibility Mission Statement To enable reliable, cost-effective, low- power, wirelessly networked, monitoring and control products based on an open global standard. Copyright 2002 The ZigBee Alliance, Inc. The ZigBee Alliance Solution • Targeted at home and building automation and controls, consumer electronics, PC peripherals, medical monitoring, and toys • Industry standard through application profiles running over IEEE 802.15.4 radios • Primary drivers are simplicity, long battery life, networking capabilities, reliability, and cost • Alliance provides interoperability and certification testing Copyright 2002 The ZigBee Alliance, Inc. IEEE 802.15.4 & ZigBee In Context Application Customer API – “the software” Security – Network, Security & 32- / 64- / 128-bit encryption ZigBee Alliance Application layers Network – Brand management Star / Mesh / Cluster-Tree MAC IEEE 802.15.4 IEEE – “the hardware” PHY 802.15.4 868MHz / 915MHz / 2.4GHz – Physical & Media Access Control layers Silicon Stack App Mapping Your Future: From Data to Value AMRA 2003 International Symposium History Proposals Proposal ZigBee Alliance Initial MRD RSI/TRD v0.2 to IEEE formed ZigBee IEEE 802.15.4 PAR Reviews Stand. Proposals Complete 1998 1999 2000 2001 2002 Copyright 2002 The ZigBee Alliance, Inc. Working Groups • Architecture • Application Framework • Network • Security • Interoperability • Marketing Copyright 2002 The ZigBee Alliance, Inc. The Wireless Market TEXT GRAPHICS INTERNET HI-FI STREAMING DIGITAL MULTI-CHANNEL AUDIO VIDEO VIDEO VIDEO LONG LAN > 802.11b < RANGE 802.11a/HL2 & 802.11g Bluetooth 2 ZigBee PAN SHORT Bluetooth1 LOW < DATA RATE > HIGH Copyright 2002 The ZigBee Alliance, Inc. Applications security HVAC TV AMR VCR lighting control DVD/CD access control BUILDING CONSUMER remote AUTOMATION ELECTRONICS patient monitoring ZigBee mouse Wireless Control that keyboard fitness Simply Works PC & joystick PERSONAL monitoring HEALTH CARE PERIPHERALS security asset mgt RESIDENTIAL/ HVAC process control LIGHT lighting control environmental INDUSTRIAL COMMERCIAL CONTROL CONTROL access control energy mgt lawn & garden irrigation Copyright 2002 The ZigBee Alliance, Inc. Development of the Standard • ZigBee Alliance – 50+ companies: semiconductor mfrs, IP providers, OEMs, etc. APPLICATION Customer – Defining upper layers of protocol stack: from network to ZIGBEE STACK application, including ZigBee application profiles Alliance SILICON IEEE – First profiles published mid 802.15.4 2003 • IEEE 802.15.4 Working Group – Defining lower layers of protocol stack: MAC and PHY scheduled for release in April Copyright 2002 The ZigBee Alliance, Inc. Frequencies and Data Rates BAND COVERAGE DATA RATE # OF CHANNEL(S) 2.4 GHz ISM Worldwide 250 kbps 16 868 MHz Europe 20 kbps 1 915 MHz ISM Americas 40 kbps 10 Copyright 2002 The ZigBee Alliance, Inc. Stack Reference Model End developer applications, designed using application profiles ZA1 ZA2 … ZAn IA1 IAn Application interface designed using API UDP general profile Topology management, MAC IP management, routing, discovery ZigBee NWK protocol, security management 802.2 LLC MAC (SSCS) Channel access, PAN maintenance, reliable data transport IEEE 802.15.4 MAC (CPS) Transmission & reception on the IEEE 802.15.4 PHY physical radio channel Copyright 2002 The ZigBee Alliance, Inc. Protocol Stack Features • Microcontroller utilized • Full protocol stack <32 k APPLICATIONS Customer APPLICATION INTERFACE • Simple node-only SECURITY stack ~4k ZigBee NETWORK LAYER • Coordinators Star/Cluster/Mesh Alliance require extra RAM MAC LAYER IEEE MAC LAYER – Node device database PHY LAYER 802.15.4 2.4 GHz 915MHz 868 MHz – Transaction table Application ZigBee Stack Silicon – Pairing table Copyright 2002 The ZigBee Alliance, Inc. ZigBee and Bluetooth Optimized for different applications • ZigBee • Bluetooth – Smaller packets over – Larger packets over small large network network – Mostly Static – Ad-hoc networks networks with many, – File transfer infrequently used – Screen graphics, pictures, devices hands-free audio, Mobile – Home automation, phones, headsets, PDAs, toys, remote controls, etc. etc. Copyright 2002 The ZigBee Alliance, Inc. ZigBee and Bluetooth Address Different Needs • Bluetooth is a cable replacement for items like Phones, Laptop Computers, Headsets • Bluetooth expects regular charging – Target is to use <10% of host power Copyright 2002 The ZigBee Alliance, Inc. ZigBee and Bluetooth Address Different Needs • ZigBee is better for devices Where the battery is ‘rarely’ replaced – Targets are : • Tiny fraction of host power • New opportunities where wireless not yet used Copyright 2002 The ZigBee Alliance, Inc. ZigBee and Bluetooth Air interface ZigBee Bluetooth • DSSS- 11 chips/ • FHSS symbol • 1 M Symbol / second • 62.5 K symbols/s • Peak Information Rate • 4 Bits/ symbol ~720 Kbit / second • Peak Information Rate ~128 Kbit/second Copyright 2002 The ZigBee Alliance, Inc. ZigBee and Bluetooth User Interface Group Call Cordless Intercom Headset vMessage Application Networking vCard vNote vCal Dial-up Fax Service Application Interface Discovery Telephony OBEX Protocol Voice Control Network Layer Protocol RFCOMM (Serial Port) L2CAP Data Link Layer Host Control Interface MAC Layer Link Manager MAC Layer Link Controller Baseband PHY Layer RF ZigBee Bluetooth Silicon Application Silicon Applications Stack Stack Zigbee Bluetooth Protocol Stack Comparison Copyright 2002 The ZigBee Alliance, Inc. ZigBee and Bluetooth Timing Considerations ZigBee: • Network join time = 30ms typically • Sleeping slave changing to active = 15ms typically • Active slave channel access time = 15ms typically Bluetooth: • Network join time = >3s • Sleeping slave changing to active = 3s typically • Active slave channel access time = 2ms typically ZigBee protocol is optimized for timing critical applications Copyright 2002 The ZigBee Alliance, Inc. ZigBee and Bluetooth Bluetooth ZigBee AIR INTERFACE FHSS DSSS PROTOCOL STACK 250 kb 28 kb BATTERY rechargeable non-rechargeable DEVICES/NETWORK 8 255 LINK RATE 1 Mbps 250 kbps RANGE ~10 meters (w/o pa) ~30 meters Comparison Overview Copyright 2002 The ZigBee Alliance, Inc. An Application Example Battery Life & Latency in a Light Switch • Wireless Light switch – – Easy for Builders to Install • A Bluetooth Implementation would either : – keep a counter running so that it could predict which hop frequency the light would have reached or – use the inquiry procedure to find the light each time the switch was operated. Copyright 2002 The ZigBee Alliance, Inc. Light switch using Bluetooth • Option 1: use counter to predict hop frequency reached by light – The two devices must stay within 60 us (~1/10 of a hop) – With 30ppm crystals, devices need to communicate once a second to track each other's clocks. – Assume this could be improved by a factor of 100 then devices would need to communicate once every 100 seconds to maintain synchronization. – => 900 communications / day with no information transfer + perhaps 4 communications on demand – 99.5% Battery Power wasted Copyright 2002 The ZigBee Alliance, Inc. Light switch using Bluetooth • Option 2: Inquiry procedure to locate light each time switch is operated – Bluetooth 1.1 = up to 10 seconds typical – Bluetooth 1.2 = several seconds even if optimized – Unacceptable latency Copyright 2002 The ZigBee Alliance, Inc. Light switch using ZigBee • With DSSS interface, only need to perform CSMA before transmitting – Only 200 µs of latency – Highly efficient use of battery power ZigBee offers longer battery life and lower latency than a Bluetooth equivalent. Copyright 2002 The ZigBee Alliance, Inc. ZigBee and Bluetooth Conclusion • ZigBee targets applications not addressable by Bluetooth or any other wireless standard • ZigBee and Bluetooth complement for a broader solution Copyright 2002 The ZigBee Alliance, Inc. Agenda • What are IEEE 802.15.4 and ZigBee? – IEEE802.15.4 – Packet Radio made simple – ZigBee and the ZigBee Alliance • Sensors and ZigBee, a natural pairing – What’s Important • Reliability and Robustness • Cost, Size and Extreme Battery Life – How it compares to other protocols • Available Silicon and Platforms – Motorola’s 802.15.4/ZigBee Platform Combo • Summary / Q&A Copyright 2002 The ZigBee Alliance, Inc. IEEE 802.15.4 Standard Copyright 2002 The ZigBee Alliance, Inc. IEEE 802.15.4 Basics • 802.15.4 is a simple packet data protocol for lightweight wireless networks – Channel Access is via Carrier Sense Multiple Access with collision avoidance and optional time slotting – Message acknowledgement and an optional beacon structure – Multi-level security – Three bands, 27 channels specified • 2.4 GHz: 16 channels, 250 kbps • 868.3 MHz : 1 channel, 20 kbps • 902-928 MHz: 10 channels, 40 kbps – Works well for • Long battery life, selectable latency for controllers, sensors, remote monitoring and portable electronics – Configured for maximum battery life, has the potential to last as long as the shelf life of most batteries Copyright 2002 The ZigBee Alliance, Inc. IEEE 802.15.4 standard • Includes layers up to and including Link Layer Control – LLC is standardized in 802.1 • Supports multiple network topologies including Star, Cluster Tree and Mesh • Features of the MAC: Association/dissociation, ACK, ZigBee Application Framework frame delivery, channel access Networking App Layer (NWK) mechanism, frame validation, guaranteed time slot management, Data Link Controller (DLC) beacon management, channel scan IEEE 802.15.4 LLC IEEE 802.2 LLC, Type I • Low complexity: 26 primitives IEEE 802.15.4 MAC versus 131 primitives for IEEE 802.15.4 IEEE 802.15.4 802.15.1 (Bluetooth) 868/915 MHz PHY 2400 MHz PHY Copyright 2002 The ZigBee Alliance, Inc. IEEE 802.15.4 MAC Overview • Employs 64-bit IEEE & 16-bit short addresses – Ultimate network size can reach 264 nodes (more than we’ll probably need…) – Using local addressing, simple networks of more than 65,000 (2^16) nodes can be configured, with reduced address overhead • Three devices specified – Network Coordinator – Full Function Device (FFD) – Reduced Function Device (RFD) • Simple frame structure • Reliable delivery of data • Association/disassociation • AES-128 security • CSMA-CA channel access • Optional superframe structure with beacons • GTS mechanism Copyright 2002 The ZigBee Alliance, Inc. IEEE 802.15.4 Device Types • Three device types – Network Coordinator • Maintains overall network knowledge; most sophisticated of the three types; most memory and computing power – Full Function Device • Carries full 802.15.4 functionality and all features specified by the standard • Additional memory, computing power make it ideal for a network router function • Could also be used in network edge devices (where the network touches the real world) – Reduced Function Device • Carriers limited (as specified by the standard) functionality to control cost and complexity • General usage will be in network edge devices • All of these devices can be no more complicated than the transceiver, a simple 8-bit MCU and a pair of AAA batteries! Copyright 2002 The ZigBee Alliance, Inc. Data Frame format • One of two most basic and important structures in 15.4 • Provides up to 104 byte data payload capacity • Data sequence numbering to ensure that all packets are tracked • Robust frame structure improves reception in difficult conditions • Frame Check Sequence (FCS) ensures that packets received are without error Copyright 2002 The ZigBee Alliance, Inc. Acknowledgement Frame Format • The other most important structure for 15.4 • Provides active feedback from receiver to sender that packet was received without error • Short packet that takes advantage of standards- specified “quiet time” immediately after data packet transmission Copyright 2002 The ZigBee Alliance, Inc. MAC Command Frame format • Mechanism for remote control/configuration of client nodes • Allows a centralized network manager to configure individual clients no matter how large the network Copyright 2002 The ZigBee Alliance, Inc. Beacon Frame format • Beacons add a new level of functionality to a network • Client devices can wake up only when a beacon is to be broadcast, listen for their address, and if not heard, return to sleep • Beacons are important for mesh and cluster tree networks to keep all of the nodes synchronized without requiring nodes to consume precious battery energy listening for long periods of time Copyright 2002 The ZigBee Alliance, Inc. MAC Options • Two channel access mechanisms – Non-beacon network • Standard ALOHA CSMA-CA communications • Positive acknowledgement for successfully received packets – Beacon-enabled network • Superframe structure – For dedicated bandwidth and low latency – Set up by network coordinator to transmit beacons at predetermined intervals » 15ms to 252sec (15.38ms*2n where 0 n 14) » 16 equal-width time slots between beacons » Channel access in each time slot is contention free – Three security levels specified • None • Access control lists • Symmetric key employing AES-128 Copyright 2002 The ZigBee Alliance, Inc. ISM Band Interference and Coexistence • Potential for interference exists in every ISM band, not just 2.4GHz • IEEE 802.11 and 802.15.2 committees are addressing coexistence issues • ZigBee/802.15.4 Protocol is very robust – Clear channel checking before transmission – Backoff and retry if no acknowledgement received – Duty cycle of a ZigBee-compliant device is usually extremely low – It’s the “cockroach that survives the nuclear war” • Waits for an opening in otherwise busy RF spectrum • Waits for acknowledgements to verify packet reception at other end Copyright 2002 The ZigBee Alliance, Inc. PHY Performance 802.15.4 has excellent performance in low SNR environments Copyright 2002 The ZigBee Alliance, Inc. IEEE1451.5 Sensor Group Wireless Criteria • A survey was conducted mid-2002 on the characteristics of a wireless sensor network most important to its users • In order of importance, these characteristics are 1. Data Reliability 2. Battery Life 3. Cost 4. Transmission Range 5. Data Rate 6. Data Latency 7. Physical Size 8. Data Security • How would you modify these requirements, if at all? Copyright 2002 The ZigBee Alliance, Inc. Reliability and Robustness throughout the stacks of IEEE 802.15.4 and ZigBee Copyright 2002 The ZigBee Alliance, Inc. Reliability • Consistently perform a given task to the desired result despite all changes of environmental behavior • Without fail • A necessary ingredient of trust • “When the sensor measures its environment; the controller always knows that same value” Copyright 2002 The ZigBee Alliance, Inc. 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. Copyright 2002 The ZigBee Alliance, Inc. Reliability • Each of these degradations and disruptions can be mitigated by various mechanisms within the ISO layers; but not all mechanisms are compatible with all other mechanisms or may negatively impact critical performance attributes • The system must be optimized for the best performance in a realistic environment Copyright 2002 The ZigBee Alliance, Inc. 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. Copyright 2002 The ZigBee Alliance, Inc. Reliability Interferer Router Multipath XX Sleeping Node Network Coordinator Hidden Node Copyright 2002 The ZigBee Alliance, Inc. Reliability • IEEE 802.15.4 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. Copyright 2002 The ZigBee Alliance, Inc. Reliability ISO Layers: • PHY: Direct Sequence with Frequency Agility (DS/FA) • MAC: ARQ, Coordinator buffering • Network: Mesh Network (redundant routing) • Application Support Layer: Security Copyright 2002 The ZigBee Alliance, Inc. 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. Copyright 2002 The ZigBee Alliance, Inc. IEEE 802 Direct Sequence IEEE 11 11b 15.4 15.4 802. (900) (2.4) Chips/ 11 11 15 32 Symbol • As can be seen from above, IEEE802.15.4/ZigBee has more processing gain (chips/symbol) than its predecessors Copyright 2002 The ZigBee Alliance, Inc. Direct Sequence and Frequency Agility Interferer Desired Signal Over the Air After DS correlation 2.4 GHz PHY Channels 11-26 5 MHz 2.4 GHz 2.4835 GHz Copyright 2002 The ZigBee Alliance, Inc. Reliability MAC: • ARQ (acknowledgement request) is where a successful transmission is verified by replying with an acknowledge (ACK). If the ACK is not received the transmission is sent again • Coordinator buffering is where the network coordinator buffers messages for sleeping nodes until they wake again Copyright 2002 The ZigBee Alliance, Inc. Reliability Network: • Mesh Networking: allows various paths of routing data to the destination device. In this way if a device in the primary route is not able to pass the data, a different valid route is formed, transparent to the user. Copyright 2002 The ZigBee Alliance, Inc. Reliability: Mesh Networking ZigBee Coordinator (FFD) ZigBee Router (FFD) ZigBee End Device (RFD or FFD) Mesh Link Star Link Copyright 2002 The ZigBee Alliance, Inc. Reliability Application Support Sub-layer(APS): • Security: supports reliability by keeping other devices from corrupting communications. • The APS configures the security emplaced in the MAC layer and also adds some of its own. Copyright 2002 The ZigBee Alliance, Inc. 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. Copyright 2002 The ZigBee Alliance, Inc. 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. Copyright 2002 The ZigBee Alliance, Inc. 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. Copyright 2002 The ZigBee Alliance, Inc. Robustness The 802.11 Working Group couldn’t agree upon which of the following PHYs was the best: FH, IR, or DS. So all three were standardized and left to the market to decide. Of the three PHYs; DS was the clear market winner. DS provided sufficient robustness with higher overall performance. Copyright 2002 The ZigBee Alliance, Inc. Robustness • Excess robustness does not achieve higher performance, rather it typically costs performance Copyright 2002 The ZigBee Alliance, Inc. Conclusion • IEEE 802.15.4/ZigBee have addressed reliability throughout the ISO stack with proven mechanisms to minimize the uncertainty of the wireless medium Copyright 2002 The ZigBee Alliance, Inc. Examples Copyright 2002 The ZigBee Alliance, Inc. Transceiver Comparisons • Instantaneous Power Consumption – 15.4 Transceivers are “similar” to Bluetooth Transceivers • 802.15.4 – OQPSK with shaping – Max data rate 250kbps over the air – 2Mchips/s over the air Direct Sequence Spread Spectrum (62.5ksps*32 spread) – -90 dBm sensitivity – 40ppm xtal • Bluetooth – FSK – Max data rate 720kbps over the air – 1Msps over the air Frequency Hop Spread Spectrum (79 channels @ 1600 hps) – -85dBm sensitivity – 20ppm xtal • Instantaneous power consumption will be similar for the raw transceivers without protocol • Bluetooth’s frequency hop makes it extremely difficult to create extended networks without large synchronization cost Copyright 2002 The ZigBee Alliance, Inc. Protocol Makes the Difference • 15.4 Protocol was developed for very different reasons than Bluetooth – 802.15.4 • Very low duty cycle, very long primary battery life applications • Static and dynamic star and mesh network structures with potentially a very large number (>>65534) of client units, low latency available but not necessary • Ability to remain quiescent for long periods of time without communicating to the network – Bluetooth • Moderate duty cycle, secondary battery operation where battery lasts about the same as master unit • Wire replacement for consumer devices that need moderate data rates with very high QoS and very low, guaranteed latency • Quasi-static star network structure with up to 7 clients (and ability to participate in more than one network simultaneously) • Generally used in applications where either power is cycled (headsets, cellphones) or mains-powered (printers, car kits) • Protocol differences can lead to tremendous optimizations in power consumption Copyright 2002 The ZigBee Alliance, Inc. Applications • Industrial Control/Monitoring Space – Asset Management • Basic identification – Device ID, Device PN/SN, Device source/destination, etc. • Asset “health” – Temperature, humidity, shock, fuel levels, etc. – Nearly any parameter can be monitored given an appropriate sensor – Asset Tracking • Location tracking through two-way communication – Simplest form is communication/identification when passes a checkpoint » Same as other RFID tagging systems – More sophisticated “what other devices can it hear/communicate with?” – Other options include ranging (time of flight) and SNR measurement » Has the potential for very precise location measurement – The wireless network uses protocol gateways to move command/monitor data between the end devices and the network data management center Copyright 2002 The ZigBee Alliance, Inc. Product Examples Warehouses, Fleet management, Factory, Energy, diagnostics, e-Business Supermarkets, Office complexes services • Gas/Water/Electric meter, HVAC • Gateway or Field Service links to • Smoke, CO, H2O detector sensors & equipment • Refrigeration case or appliance – Monitored to suggest PM, product updates, • Equipment management services & PM status changes • Security services • Nodes link to PC for database storage – PC Modem calls retailer, Service Provider, or • Lighting control Corp headquarters • Assembly line and work flow, Inventory – Corp headquarters remotely monitors assets, • Materials processing systems (heat, gas flow, billing, energy management cooling, chemical) Field Service or mobile worker Temp. Database Sensor Gateway Security Sensor Back End Mfg Flow Telephone Server Cable line Materials HVAC Corp handling Service Office Retailer Copyright 2002 The ZigBee Alliance, Inc. Provider Home & Diagnostics Examples SOHO • Mobile clients link to PC for database Retailer Dealer storage Service – PC links to peripherals, interactive toys Provider – PC Modem calls retailer, SOHO, Service Provider Customers • Gateway links to security system, temperature sensor, AC system, Back End entertainment, health. Server Server • Gateway links to field sales/service PC & Telephone Gateway(s) peripherals Entertainment Cable line Temp. Field Sensor Service Body monitor AC or Security heat Sensor Pump Data Communication Two way White goods Copyright 2002 The ZigBee Alliance, Inc. HID Scenario: Wireless Keyboard • Scenario Parameters – Battery-operated keyboard • Part of a device group including a mouse or trackball, sketchpad, other human input devices • Each device has a unique ID • Device set includes a USB to wireless interface dongle – Dongle powered continuously from computer • Keyboard does not have ON/OFF switch • Power modes – Keyboard normally in lowest power mode – Upon first keystroke, wakes up and stays in a “more aware” state until 5 seconds of inactivity have passes, then transitions back to lowest power mode Copyright 2002 The ZigBee Alliance, Inc. Keyboard Usage • Typing Rates – 10, 25, 50, 75 and 100 words per minute • Typing Pattern – Theoretical: Type continuously until battery is depleted • Measures total number of hours based upon available battery energy Copyright 2002 The ZigBee Alliance, Inc. Wireless Keyboard Using 802.15.4 • 802.15.4 Operation Parameters • Star network • Non-beacon mode (CSMA-CA) • USB Dongle is a PAN Coordinator Full Functional Device (FFD) • Keyboard is a Reduced Function Device (RFD) • Power Modes – Quiescent Mode used for lowest power state » First keystroke latency is approx 25ms – Idle mode used for “more aware” state » Keystroke latency 8-12 ms latency Copyright 2002 The ZigBee Alliance, Inc. Wireless Keyboard Using 802.15.4 • 802.15.4 Chipset Parameters • Motorola 802.15.4 Transceiver and HCS08 MCU • Battery operating voltage 2.0 – 3.6 V – All required regulation internal to ICs – Nearly all available energy usable with end of life voltage at 2.0 volts Copyright 2002 The ZigBee Alliance, Inc. Wireless Keyboard Using Bluetooth • Bluetooth Operation Parameters • Piconet network • USB Dongle is piconet Master • Keyboard is a piconet Slave • Power Modes – Park mode used for lowest power state » 1.28 second park interval » First keystroke latency is 1.28s – Sniff mode used for “more aware” state » 15ms sniff interval » 15ms latency Copyright 2002 The ZigBee Alliance, Inc. Wireless Keyboard Using Bluetooth • Bluetooth Chipset Parameters • CSR BlueCore 2 –External + Flash + Regulator • Battery Operating Voltage 2.7 – 3.6 Vdc – Requires external regulator for best performance – Only 19 to 30 percent of available battery life usable with 2.7V cutoff voltage • Power Consumption (estimated) – Park Mode @ 1.28 s interval: 0.05mA avg – Sniff Mode @ 15ms interval: 8mA avg – NOTE: I do not assume a deep sleep mode since wake up time of 4 to 30 seconds seems unacceptable Copyright 2002 The ZigBee Alliance, Inc. BT vs. 15.4 Keyboard Comparison Bad Hunt n’ Peck 802.15.4: Approx 38 days BT: Approximately 5 operating days By the way, WirelessUSB looks much like BT Copyright 2002 The ZigBee Alliance, Inc. Medical Sensor Scenario Assumptions • Environment – Battery-operated sensor body-worn with either body-worn or facility-mounted coordinator – Sensor • Running 100% of time • Intelligent enough to output a digital waveform that at a minimum signals a detected heart beat • For the course of this study, assume that only the leading edge of this pulse contains information (I.e., heartbeat event occurred) • Power consumption is 10uA (WAG; immaterial to wireless connection but will consume wireless connection's battery) – Network Coordinator • Provides a regular RF beacon to which the sensor synchronizes • Expect to hear from the sensor during communications windows relative to beacon interval • Power Source – Battery-operated if body-worn cellphone or other network access device – Mains-powered if part of a hospital infrastructure Copyright 2002 The ZigBee Alliance, Inc. 802.15.4/ZigBee Operation Mode • 802.15.4/ZigBee Mode – Network environment using Guaranteed Time Slot (GTS) – Network beacons occurring either every • 960ms or 61.44s (closest values to 1 and 60 s) • Guaranteed time slot occurs at some predetermined point in the beacon interval • Sensor has two ongoing processes – Heartbeat time logging – Transmit heartrate and other information (8 bytes total) • Instantaneous heartrate (1/timeinterval between last two pulses,1ms precision) • Running average heartrate (1/time interval between last twenty pulses, 1ms precision) • Sensor average temperature (0.1C precision) • Sensor average battery state (0.1V precision) heartbeat GTS Beacon time Copyright 2002 The ZigBee Alliance, Inc. Medical Sensor Scenario • Low Power, Low Latency – RF XCVR IC is essentially off (leakage currents predominating) in normal state – MCU is capable of responding immediately to an interrupt • MCU onboard 32kHz time clock is running • Heartbeat sensor is capable of generating an interrupt signal for MCU • System is in a multisensor environment where all sensors are assigned guaranteed timeslots (GTS) for communications • Scenario 1 – Beacon interval is 960ms (15ms*2^6) • Scenario 2 – Beacon interval is 61.44s (15ms*2^12) • Assume that retries are not necessary due to GTS – Reasonable if we assume RF environment is well-controlled Copyright 2002 The ZigBee Alliance, Inc. General Schematic Vcc Vcc 3Vdc 802.15.4 SPI SPI 4 XCVR MCU IRQ/ INT IRQ RESET OSC1 OSC2 Plus about 10-12 small value 16.000MHz capacitors, resistors excluding any 32.768kHz special components for heartbeat sensor) Heartbeat Sensor Copyright 2002 The ZigBee Alliance, Inc. Sensor Battery Type • Lithium coin primary battery – Tadiran Lithium type TL-2186 • http://www.tadiran.com/pdf/tl-2186.pdf – 400 mAh nominal capacity (0.5mA constant to 2.0V) – 3.6V BOL, 2.0V EOL Copyright 2002 The ZigBee Alliance, Inc. Two Processes • Process 1 – Each heartbeat forces the MCU to respond to the sensor interrupt – From MCU interrupt to completion of processing • Approximately 980 microseconds • Approximately 3E-8 mAh consumed per heartbeat • Process 2 – Each 960ms or 61.44s the system synchronizes to network and transmits the information – From MCU beacon wakeup to completion of transmission • Approximately 56ms (varies depending on beacon interval and assigned guaranteed time slot) • Approximately 3E-4 mAh consumed per transmission event • Constant Idle Currents – 10 microamp sensor – Leakage currents in RF XCVR IC and MCU oscillator/Time base reference (~ microamps) Copyright 2002 The ZigBee Alliance, Inc. 802.15.4/ZigBee vs Bluetooth Li-Coin Cell Battery Life (Beacon Interval vs Heartrate vs Days) 900 At beacon interval ~60s, 15.4/ZigBee battery life 800 approx 750 days 700 600 802.15.4/ZigBee superior at all beacon intervals 60 500 greater than 0.246s 72 Days 86 400 104 At beacon interval ~1s, Bluetooth 33 days 124 300 15.4/ZigBee battery life (park mode @ 1.28s) 149 nearly 136 days 179 200 BT@72bps 100 0 0.015 0.031 0.062 0.123 0.246 0.492 0.984 1.969 3.937 7.875 15.749 31.498 62.996 125.993 251.986 Beacon Interval (sec) Copyright 2002 The ZigBee Alliance, Inc. Conclusion • Bluetooth and 802.15.4 transceiver physical characteristics are very similar • Protocols are substantially different and designed for different purposes • 802.15.4 designed for low to very low duty cycle static and dynamic environments with many active nodes • Bluetooth designed for high QoS, variety of duty cycles, moderate data rates in fairly static simple networks with limited active nodes • Bluetooth costs and system performance are in line with 3rd and 4th generation products hitting market while 1st generation 15.4 products will be appearing only late this year Copyright 2002 The ZigBee Alliance, Inc. More Information • ZigBee Alliance web site – http://www.ZigBee.org • IEEE 802.15.4 web site – http://www.ieee802.org/15/pub/TG4.html • Articles – “Meet the ZigBee Standard”, Sensors Mag June 2003 http://www.sensorsmag.com/articles/0603/14/ – “ZigBee Vital in Industrial Applications”, EETimes, 29 July 2003 http://www.eetimes.com/story/OEG20030727S0002 Copyright 2002 The ZigBee Alliance, Inc. Motorola 802.15.4/ZigBee™ Platform for Low Data Rate Wireless Jon Adams Director, Architecture and Systems Motorola American Association of Wireless and Railroads Broadband Automatic Equipment Identification Conference Systems Group Pittsburgh, PA 17 June jta @ Copyright 2002 The ZigBee Alliance, Inc. System Simplicity and Flexibility Motorola RF Packet Radio Motorola 8-Bit MCU Copyright 2002 The ZigBee Alliance, Inc. Motorola 802.15.4 / ZigBee™ solution • Features – 2.4 GHz Band, -90 dBm RX sensitivity at 1% PER • IEEE spec is –85 dBm – Power supply 2.0-3.6 V w/ on-chip regulator, logic interface 1.7 to 3.3 • Runs off a single Li or 2 alkaline cells – Complete RF transceiver data modem – antenna in, fully packetized data out – Data and control interface via standard SPI at 4 to 8 MHz – 802.15.4 MAC – A large number of Motorola’s substantial line of HC08 MCUs will interoperate with the data modem chip • Often 802.15.4 functionality can be added to existing systems simply by including the modem chip and reprogramming an existing MCU that may already be in the application – HC08 RAM/FLASH configurations from 384B/4kB to 2kB/60kB depending upon application SW needs Copyright 2002 The ZigBee Alliance, Inc. Motorola’s RF Data Modem Transceiver (1) • Designed for the IEEE 802.15.4 and ZigBee™ standards – Operates in the 2.4 GHz ISM band available worldwide – Cost effective CMOS design – Low external components, no T/R switch required – On-chip low noise amplifier – 0dBm (1.0 mW) PA, step adjustable to –30dBm – Integrated VCO, no external components – Full spread-spectrum encoding and decoding compatible with 802.15.4 – RX sensitivity of –90 dBm at 1% PER, better than specification – Engineered to support 250 kBit/s O-QPSK data in 5.0 MHz channels, per the IEEE 802.15.4 specification – No line-of-sight limitations as with infrared (IR) Copyright 2002 The ZigBee Alliance, Inc. Motorola’s RF Data Modem Transceiver (2) • Designed to run DIRECTLY off two alkaline AA or AAA cells, or one Lithium cell – 2.0 to 3.6 V with on-chip voltage regulator – Can use the full capacity of the battery (to end of life ~1.0V per cell) • Buffered transmit and receive data packets for simplified use with low-end microcontrollers • SPI data and control interface, operates up to 8MHz • Designed to support peer to peer and star topologies • On-board timers to support optional Superframe/Guaranteed Time Slots for low latency transfer • Will support optional Zigbee™ Network layer software • Application-configurable power-saving modes that take best advantage of battery operation – RX/TX > Idle > Doze > Hibernate > Off Copyright 2002 The ZigBee Alliance, Inc. Scalability to Address Specific Needs 802.15.4 is a guest in existing microcontrollers 802.15.4 PHY Compliant Transceiver Application- RF Transceiver IC specific interfaces Zigbee NWK SPI Application RF Receiver Digital 15.4 FFD MAC Processing System Complexity and Cost RF Transmitter >32kB FLASH 8-Bit Microcontroller RF Transceiver IC Application SPI Zigbee NWK RF Receiver Digital 15.4 RFD MAC RF Transmitter Processing 32kB FLASH 8-Bit Microcontroller RF Transceiver IC Application SPI RF Receiver Digital 15.4 RFD MAC RF Transmitter Processing 12kB FLASH 8-Bit Microcontroller RF Transceiver IC SPI Application RF Receiver Digital Direct SPI Calls RF Transmitter Processing 3kB FLASH (min) 8-Bit Microcontroller Copyright 2002 The ZigBee Alliance, Inc. Motorola’s 802.15.4 Platform Advantages • Total System Solution – Single source for platform solution • Integrated Circuits, Reference Designs, Modules, Stack Software, Development Systems • Key technology enhancements provide for a superior solution – Adjacent channel rejection • Improvements in noisy environment – High Sensitivity Radio Solution • 5 dBm beyond spec – longer range – Extended Temperature Operating Range • -40°C to +85°C for industrial and automotive applications – Operating voltage range optimized for alkaline or lithium primary cells • 2.0 Vdc to 3.6 Vdc, disposable – Adjustable TX Output power • Improved coexistence for short range applications, improved battery life • IEEE and ZigBee™ Alliance membership – Technology and standards driver – Early access to new technology Copyright 2002 The ZigBee Alliance, Inc. Home/Light Commercial Spaces Copyright 2002 The ZigBee Alliance, Inc. Industrial/Commercial Spaces Energy, diagnostics, e-Business • Warehouses, Fleet management, services Factory, Supermarkets, Office • Gateway or Field Service links to complexes sensors & equipment – Monitored to suggest PM, product updates, • Gas/Water/Electric meter, HVAC status changes • Smoke, CO, H2O detector • Nodes link to PC for database storage • Refrigeration case or appliance – PC Modem calls retailer, Service Provider, or Corp headquarters • Equipment management services & – Corp headquarters remotely monitors assets, Preventative maintenance billing, energy management • Security services • Lighting control • Assembly line and work flow, Field Service Inventory or mobile worker • Materials processing systems (heat, gas flow, cooling, chemical) Temp. Database Sensor Gateway Security Sensor Back End Mfg Flow Telephone Server Cable line Materials HVAC Corp handling Service Office Retailer Copyright 2002 The ZigBee Alliance, Inc. Provider Peel-n’-Stick Security Sensors • Battery Operation – 2 AA Alkaline or 1 Li-AA cell • 802.15.4/ZigBee Mode – Non-beacon network environment Vcc SPI 4 SPI Vcc 3Vdc • Sensor process 802.15.4 XCVR CLK OSC1 MCU – RC Oscillator waking up IRQ MCU and doing network check-in at some interval Security 16.000MHz • Many security systems Sensor have between ~10 second and ~15 minute requirement – On a sensor event, device immediately awakens and reports in to network Copyright 2002 The ZigBee Alliance, Inc. Security Sensor Timing Battery-Powered Mains-Powered Sensor Router Interval timer expires: Wake Up 256µs CCAx2 192µs RX>TX ~650µs TX RX 192µs TX>RX RX>TX Check-in only ~350µs ACK TX ACK RX ~1640µs OPT: Pending ON Event and Get Data ~2300µs ~650µs RX Data TX Data Set Interval timer Sleep Copyright 2002 The ZigBee Alliance, Inc. 802.15.4 Security Sensor Any check-in interval exceeding ~14 sec allows sensor to surpass alkaline battery shelf life Only at 15-min interval does BT reach battery shelf life Copyright 2002 The ZigBee Alliance, Inc. Body-Worn Medical Sensors • Heartbeat Sensor – Battery-operated using heartbeat CR2032 Li-Coin cell GTS • 802.15.4/ZigBee Mode Beacon – Network environment using Guaranteed Time Slot time (GTS) – Network beacons occurring either every • 960ms or 61.44s (closest values to 1 and 60 s) Vcc Vcc • Sensor has two ongoing 3Vdc SPI SPI 802.15.4 processes 4 MCU XCVR IRQ/ INT – Heartbeat time logging RESET OSC1 OSC2 IRQ – Transmit heartrate and other information (8 bytes Heartbeat total) 16.000MHz 32.768kHz Sensor • Instantaneous and average heart rate • Body temperature and battery voltage Copyright 2002 The ZigBee Alliance, Inc. Tracking Global Shipments Securely 1 • High value consumer electronics shipment from Singapore to Chicago (sea leg) – Container loaded with high-value electronics in Singapore, container’s transponder reads all the traditionally RFID- tagged material inside the container – Loaded on ship at harbor, crane/ship communicates with container’s transponder confirming loading, contents and security and providing it information on ship’s network – As ship proceeds across Pacific, environmental and security data regularly collected from container’s transponder, ensuring the safety of the contents and providing ability for shipper/contents owner to proactively respond to container malfunction/security breach – Offloading at Long Beach, container transponder communicates with crane to validate contents/point of origin/container security and provides it information on train’s network Copyright 2002 The ZigBee Alliance, Inc. Tracking Global Shipments Securely 2 • High value consumer electronics shipment from Singapore to Chicago (rail leg) – Transloaded onto COFC train at Los Angeles harbor, crane verifies contents, container ID and car number location match to train manifest and provides it information on train’s network – Conveying flatcar establishes link with loaded container, communicates “loaded” status forward to locomotive computer – Train leaves for Chicago; along way, locomotive continues to request and receive regular updates from container and relay entire train status to Ops • Railroad provides the just-in-time information via internet to the shipper/receiver – Train arrives Chicago, container offloaded at yard, crane communicates with container and verifies contents, source, and security and provides it information on truck’s network Copyright 2002 The ZigBee Alliance, Inc. Tracking Global Shipments Securely 3 • High value consumer electronics shipment from Singapore to Chicago (road leg) – Road tractor/trailer combo moving container to final destination has transponder that communicates with container, and verifies contents, source, destination, and security – Container arrives at destination (big box retail store distribution) where employees verify for the final time the contents, source, destination and container security before signing off on delivery • Shipment protected at all times on journey • Mishandling, smuggling, homeland security issues all contained with this simple yet very sophisticated system Copyright 2002 The ZigBee Alliance, Inc. What security issues are there and how will they be solved? • Security and data integrity – Key benefits of the ZigBee technology – ZigBee leverages the security model of the IEEE 802.15.4 RF standard • Extends this capability with robust encryption options • Can be tailored to the specific needs of the networked device Copyright 2002 The ZigBee Alliance, Inc. How is ZigBee related to IEEE 802.15.4? • ZigBee takes full advantage of – A powerful physical radio specified by IEEE 802.15.4 • ZigBee adds – Logical network and application software • ZigBee is based on the IEEE 802.15.4 RF standard, and the Alliance is working closely with the IEEE to ensure an integrated and complete solution for the market Copyright 2002 The ZigBee Alliance, Inc. Non-Beacon vs Beacon Modes • Non-Beacon Mode – A simple, traditional multiple access system used in simple peer and near-peer networks – Think of it like a two-way radio network, where each client is autonomous and can initiate a conversation at will, but could interfere with others unintentionally – However, the recipient may not hear the call or the channel might already be in use • Beacon Mode – A very powerful mechanism for controlling power consumption in extended networks like cluster tree or mesh – Allows all clients in a local piece of the network the ability to know when to communicate with each other – Here, the two-way radio network has a central dispatcher who manages the channel and arranges the calls • As you’ll see, the primary value will be in system power consumption Copyright 2002 The ZigBee Alliance, Inc. Example of Non-Beacon Network • Commercial or home security – Client units (intrusion sensors, motion detectors, glass break detectors, standing water sensors, loud sound detectors, etc) • Sleep 99.999% of the time • Wake up on a regular yet random basis to announce their continued presence in the network (“12 o’clock and all’s well”) • When an event occurs, the sensor wakes up instantly and transmits the alert (“Somebody’s on the front porch”) – The ZigBee Coordinator, mains powered, has its receiver on all the time and so can wait to hear from each of these stations • Since ZigBee Coordinator has “infinite” source of power it can allow clients to sleep for unlimited periods of time to allow them to save power Copyright 2002 The ZigBee Alliance, Inc. Example of Beacon Network • Now make the ZigBee Coordinator battery-operated also – All units in system are now battery-operated – Client registration to the network • Client unit when first powered up listens for the ZigBee Coordinator’s network beacon (interval between 0.015 and 252 seconds) • Register with the coordinator and look for any messages directed to it • Return to sleep, awaking on a schedule specified by the ZigBee Coordinator • Once client communications are completed, ZigBee coordinator also returns to sleep – This timing requirement potentially impacts the cost of the timing circuit in each end device – Longer intervals of sleep mean that the timer must be more accurate or – Turn on earlier to make sure that the beacon is heard, increasing receiver power consumption, or – Improve the quality of the timing oscillator circuit (increase cost) or – Control the maximum period of time between beacons to not exceed 252 seconds, keeping oscillator circuit costs low Copyright 2002 The ZigBee Alliance, Inc.
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