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The IEEE 802.15.4 (Low Rate Wireless Personal Area Network) Standard Lance Hester Ken Cornett Florida Communication Research Lab Motorola Labs May 20, 2002 IEEE 802.15.4 Standard IEEE What? IEEE 802 LAN/MAN Standards Committee … … … 802.1 802.11 Higher Layer … Wireless Local … LAN Protocols Area Network Working Group Working Group TG1 WPAN/Bluetooth Task Group TG2 Coexistence Task Group 802.15 Wireless Personal Area Network Working Group TG3 WPAN High Rate Task Group … 802.17 Resilient Packet Ring Working Group TG4 WPAN Low Rate Task Group Formed in November, 2000 Florida Communication Research Lab 20 May 2002 2 IEEE 802.15.4- What it is: An WPAN standard optimized for low (0.01115.2 kb/s) data throughput applications with simple QoS requirements Lower power, lower cost than other WPANs (e.g., Bluetooth) Capable of multiple network types (star, cluster tree, etc.) Using ZigBee Consortium for marketing and compliance (like WECA/Wi-Fi/802.11b) Florida Communication Research Lab What it is not: A WLAN A Bluetooth™ replacement (e.g., no isochronous voice capability) Optimized for multimedia, TCP/IP, or other high data rate applications A system, network, or application set 20 May 2002 3 802.15.4 Physical Layers 2.4 GHz: 250 kb/s raw data rate, 1 Mc/s chip rate Chips: O-QPSK with half-sine shaping (a.k.a. MSK) Data: 16-ary orthogonal modulation 16 channels; 5 MHz channel separation -85 dBm sensitivity @ 1% PER (20 byte packets) Variable length payload size dependent upon addressing 868 (915- U.S.) MHz: 20 (40) kb/s raw data rate, 300 (600) kc/s chip rate Chips: BPSK with raised-cosine shaping Data: differential BPSK 1 (10) channels; 2 MHz channel separation @ 915 MHz -92 dBm sensitivity @ 1 % PER (20 byte packets) Florida Communication Research Lab 20 May 2002 4 802.15.4 Physical Characteristics Transmission Range ~ 10 meters indoors; ~ 30 meters outdoors @ Tx-Power = - 3 dBm (0.5 mW) Maximum regulated transmit power levels Frequency Band Geographical Region Max. conductive power/ Radiated field limit Regulatory Document 2.4 GHz Japan 10 dBm (10 mW) ARIB STD-T66 Europe (except Spain and France) 20 dBm (100 mW) EIRP or 10 dBm (10 mW) /MHz peak power density ETS 300- 328 USA 30 dBm (1000 mW) 47 CFR 15.247 902-928 MHz USA 30 dBm (1000 mW) 47 CFR 15.247 868 MHz Europe 14 dBm (25 mW) ETS 300-220 Power Consumption < 100 A Expected duty cycle of 1% and low power operation (under 0 dBm [1mW]) Power Supply AA battery Lifetime approx. 1 year Florida Communication Research Lab 20 May 2002 5 802.15.4 Physical Characteristics Bi-directional communication supported Uni-directional communication not supported All messages are acknowledged DSSS modulation mitigates multipath interference “1000 ns” chip length >> 30 ns propagation delay Florida Communication Research Lab 20 May 2002 6 Chip Set information Yes! There is IC development for the 802.15.4 Florida Communication Research Lab 20 May 2002 7 802.15.4 Medium Access Control (MAC) Features Extremely flexible support: Star, cluster tree, other network topologies, with optional network beacon Slotted Access CSMA-CA Superframe period switchable from 15 ms to > 4 minutes Trade power consumption, message latency, and throughput Optional guaranteed time slots in superframe Application flexibility Low-latency applications (e.g., mice, wireless gaming) Low duty cycle: Can be < 0.1% Low power consumption Good coexistence with other services Florida Communication Research Lab 20 May 2002 8 802.15.4 MAC Super Frame Structure Beacon Contention Access Period Contention Free Period GTS 1 Beacon GTS 2 Super Frame Duration Network Beacon Contention Period Allocated slot Transmitted by nodes. Contains network information, super frame structure, and notification of pending messages Access by any node using CSMA-CA Reserved for nodes requiring guaranteed bandwidth Florida Communication Research Lab 20 May 2002 9 Node Types Supported Distribution node Controls the network topology at that node Master/coordinator or mediation device Stores routing information Talks to other distribution and slave nodes Slave node Cannot control the network Very simple implementation Does not store routing information Talks only to a distribution node Florida Communication Research Lab 20 May 2002 10 Related technology Network Scalability Low latency intensive High 802.3 - ‘Wired Ethernet’ Fixed Intended for high power apps Cost Fixed & Wireless 802.11b - ‘Wi-Fi’ Moderate Bluetooth 802.15.4 M2M Low 100 102 104 106 Area (meters2) To complex for lowrate low-power apps Florida Communication Research Lab Data Rate (Mbps) 100 802.11x 802.3 802.15.3 802.11a 10 1 4G 802.11b Transitions from Wired to Wireless “Bluetooth” 802.15.1 Evolution Path with Sustaining Innovation 3G 2.5G 0.1 PSTN 1G 1980 802.15.4 2G 1990 Variable w/ Duty Cycle 2000 2010 20 May 2002 11 How Does 802.15.4 Match Up? Surveyed Wireless Sensor IEEE 802.15.4 Provisions Wants Low data rates Data rates 115.2 kb/s Usage of unlicensed frequency ISM band operation Long battery life Low duty cycle operation Low power consumption Low cost devices Standard for ultra low cost and low complex devices Architecture which adapts to accommodate various node types Platform for various networking schemes and supports multiple node types (e.g. distribution and slave nodes) Market acceptance Member of well known 802 family Florida Communication Research Lab 20 May 2002 12