Wireless Body Area Networks WiserBAN Smart miniature low-power wireless microsystem for Body Area Networks www.wiserban.eu
Wireless Body Area Networks (WBANs) WBAN: Collection of nodes placed on, or inside, the human body (but not limited to). Nodes have sensing and/or actuating and communication capabilities. Applications: Medical: monitoring vital parameters, hearing aids, cardiac implant, etc. Sport/Fitness: rehabilitation, motion capture, monitoring parameters; Entertainment: consumer electronics (audio/video streaming, interactive gaming), personal item tracking.
Wireless Body Area Networks (WBANs) Application Requirements: Requirements may be very different depending on the application
Standard IEEE 802.15.6 IEEE 802.15 Task Group 6 (November 2007): Define the Physical (PHY) and Medium Access Control (MAC) Layers for short range, low complexity, low cost, ultra-low power and high reliable wireless communication in, on or around the human body. High level application requirements 7
Standard IEEE 802.15.6 Riccardo Cavallari DEI, Università di Bologna Physical (PHY) Layer 3 different PHY Japan North America Australia Europe New Zeland Japan WorldWide 5 50 402 405 863 870 950 958 420 450 902 928 2360 2400 2483.5 3100 10600 HBC MICS WMTS ISM ISM UWB f [MHz] Modulation @ 2.45GHz Packet Component Modulation Symbol Rate (ksps) Spreading Factor (S) Narrowband Information Data Rate (kbps) PSDU π/2-dbpsk 600 4 121.4 PSDU π/2-dbpsk 600 2 242.9 PSDU π/2-dbpsk 600 1 485.7 PSDU π/4-dqpsk 600 1 971.4 N of Channel @ 2.45GHz: 79 Channel of 1MHz Bandwidth Min Tx Power: -10 dbm EIRP Receiver Sensitivity @ 2.45GHz: Frequency Band (MHz) 2400 2483.5 Information Data Rate (kbps) Minimum Sensitivity (dbm) 121.4 92 242.9 90 485.7 87 971.4 83 5
Standard IEEE 802.15.6 MAC Access Modes / 1 1. Beacon Mode with superframe: beacons at the beginning of each superframe to establish a common time base for time referenced allocations; Random Access Phases Contention between nodes: allocations are non-recurring time intervals valid per instance of access. EAP (Exclusive Access Phase): for high priority traffic. RAP (Random Access Phase): for regular traffic. CSMA/CA Access Method: Backoff counter (BC) in the interval [0-CW], BC is decremented by one, for each successive idle CSMA time slot; When BC=0, the node obtains a contended allocation during which the TX occurs. Slotted Aloha Access Method: Contention Probability (CP) properly set; z =random in the interval [0-1]; If z CP the node obtains a contended allocation in the current Aloha slot, during which the TX occurs. 13
Standard IEEE 802.15.6 MAC Access Modes / 2 Riccardo Cavallari DEI, Università di Bologna 2. Non-Beacon Mode with superframes: no beacons but superframe and allocation slots are established because the channel access involves time referencing. Only MAP. 3. Non-Beacon Mode without superframes: no beacons; superframe and allocation slots are not established because the allocation involves no time referencing. Unscheduled Access Method: A hub may provide unscheduled reoccuring polled or posted allocations, nodes may use CSMA/CA to obtain a contended allocation. 7
WiserBAN Project WiserBAN EU Project: realizes a miniaturized and ultra-low power RF microsystem, for medical and multimedia applications. T 4.3 T 4.2 T 4.1
WiserBAN after three years: SiP First chips are coming out First functional 2D-SiP for implantable devices. Left: 2D-SiP after assembly and Right: 2D-SiP after embedding. The final size of the 2D-SiP is 4.2mmx4.3mmx0.77mm.
WiserBAN after three years: SiP 3D SiP. From bottom down: SoC, piezo and antenna modules 2D-SiP on characterization board 3D SIP close-up
WiserBAN after three years: Antennas Photographs of the first L-antenna prototypes Radiation pattern of the L-antenna near human head New design of the micro SD antenna Directivity pattern for the smartphone scenario
WiserBAN after two years: Antennas Passive micro-sd antenna for WBAN remote control node Active frequency agile dipole antenna for ITE hearing aid Loop antenna integrated in cochlea implant
WiserBAN after three years: Radio
WiserBAN Project WiserBAN EU Project: aim is to develop a BAN protocol architecture that: Provides optimized power consumption while providing support for identified application requirements Supports coexistence and as much as possible cooperation and compliance with other BAN/PAN protocol architectures.
MAC protocol: Architecture
MAC protocol: Superframe mode Synchronous MAC High traffic applications 802.15.6 CSMA/CA 802.15.4 CSMA/CA 802.15.6 Slotted ALOHA Beacon POLL (Indicators) RELAYING CFP (TDMA) CAP (CSMA/CA or Slotted ALOHA) ACK Inactive (Sleep) Beacon
MAC protocol: LPL mode Asynchronous MAC Low traffic, low energy applications TX ON T 1 IDLE P P P P A C K Data Frame A C K = TX t RX ON = RX Active Sleep P A C K Data Frame A C K IDLE T on T w T data t
MAC protocol: Implementation (*) This transitionimplies the channel selection procedure throughenergy detection. (**) This transitionimplies the Passive/Active scan procedure. FULL FUNCTION DEVICE REDUCED FUNCTION DEVICE LOW POWERDEVICE mac_init(mac_extended_address_t address) INITIALIZED MLME_RESET_REQUEST COORDINATOR MLME_TDMA_START_REQUEST (*) READY MLME_RESET_REQUEST All states MLME_SYNC_REQUEST (**) MLME_TDMA_START_REQUEST SYNCHRONIZATION MLME_SYNC_REQUEST MLME_BEACON_NOTIFY_INDICATION LPL SYNCHRONIZED MLME_SYNC_LOSS_INDICATION SYNCHRONIZATION LOST MLME_LPL_START_REQUEST All statesbut INITIALIZED MLME_ASSOCIATE_CONFIRM MLME_DISASSOCIATE_CONFIRM ASSOCIATED MLME_SYNC_LOSS_INDICATION
Experimental Setup Implementation and tests of the superframe CAP portion 3 end devices + 1 coordinator Right Ear Left Ear B e a c o n 802.15.6 CSMA/CA 802.15.4 CSMA/CA Slotted Aloha Inactive B e a c o n Remote Control Right Hip T CAP =60 ms t Superframe (SF), 75 ms RC 3 2 1 `
Performance Evaluation Metrics Average packet delay Packet lost rate Energy consumption
Experimental Results Impact of Radio Channel
PL R CSMA/CA Body shadowing: PLR Measurement Results: PLR for each link 0.14 Packet Loss Rate 0.12 link 1: right ear link 2: left ear link 3: heart Right Ear Left Ear link 4: left hip 0.1 average Heart 0.08 Left Hip 0.06 Remote Control 0.04 0.02 0 0 10 20 30 40 50 60 70 80 90 100 Payload size [Byte]
Experimental Results Comparing the Different Protocols
Protocol Comparison: Average Delay
Protocol Comparison: PLR
Experimental Results Low-Power-Listening MAC
Low-Power-Listening MAC Star topology composed of 1,2 or 3 EDs and one Coordinator. RC 3 2 C 1 ` ED 1 ED 3 Traffic: ED 2
MAC protocol: LPL mode Asynchronous MAC Low traffic, low energy applications TX ON T 1 IDLE P P P P A C K Data Frame A C K = TX t RX ON = RX Active Sleep P A C K Data Frame A C K IDLE T on T w T data t
Average energy consumed per packet [mj/packe LPL: Energy Consumption 0.5 0.4 0.3 0.2 Transmitter Receiver RX, 20 Bytes RX, 60 Bytes RX, 100 Bytes TX, 20 Bytes TX, 60 Bytes TX, 100 Bytes 0.1 50 75 100 T w [ms]
Average packet delay [ms] LPL: Average Delay 60 50 40 100 Bytes 60 Bytes 20 Bytes 50 75 100 T w [ms]
Throughput [kbit/s] LPL: Throughput 400 300 Ideal MAC LPL peer-to-peer LPL Star 2 TX LPL Star 3 TX 200 100 0 50 100 150 200 250 300 350 400 Offered load [kbit/s]
Wireless Sensor Networks Chiara Buratti www.chiaraburatti.org c.buratti@unibo.it