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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Block based PHY and Packet Transmission for Low Data Rate In-body WBAN Date Submitted: [16 July 2009]

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Block based PHY and Packet Transmission for Low Data Rate In-body WBAN Date Submitted: [16 July 2009] Source: [Dong-Sun Kim1, Jong-Ik Song1, Tae-Ho Hwang1, Young Hwan Kim1, Jae Gi Son1, Sang-Jin Hyun1, Ha-Joong Chung1, Chang-Won Park1, Seung-Ok Lim1, Yangmoon Yoon2, Sang Yun Lee2, Moon Young Choi2, Yongho Seok3, Seyong Choi3, Byoung-Hoon Kim3, Do Hyeon Kim4 and S.M. Ryu5] Company: [KETI1, KORPA2, LG Electronics3, Cheju National University4, Casuh5] Address: [KETI1 ; #68 Yatap-dong Bundang-gu, Seongnam-si, Gyeonggi-do 463-816, South Korea, KORPA2 ; 78 Garak-dong, Songpa-gu, Seoul, 138-803, South Korea, LG Electronics3 ; LG R&D2 Complex 533, Hogye-1dong, Dongan-Gu, Anyang-Shi, Kyungki-Do, 431-749, South Korea, Jeju National University4 ; 66, Ara-Dong, JeJu-City, JeJu-Do, 431-749, South Korea, Casuh5 ; #813 Leaders B/D, 342-1, Bundang, Seongnam, Kyeonggi, 463-828, Korea] Voice: [+82-31-789-73841, +82-31-450-19472, +82-2-2142-21623], FAX: [+82-31-789-75591, +82-31-450-40492+82-2- 2142-21993] E-Mail: [dskim@keti.re.kr1, yhseok@lge.com3,yoon001@paran.com2] Re:[] Abstract: Key requirements of the BAN standards effort, including power, cost and throughput scalability, can be addressed using a scalable block frame structure based on variable block FEC. In addition, BCH encoded 2FSK modulation scheme enable simple structure, low power consumptions and low cost transceiver implementation under in-body communication channel. Purpose: This document is intended as a proposal for addressing the requirements of the TG6 standard. Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Slide 1

  2. Contributors KETI : Korea Electronics Technology Institute KORPA : Korea Radio Promotion Agency LG Electronics Jeju National University Casuh Slide 2

  3. Contributors (Continued) KETI : Korea Electronics Technology Institute KORPA : Korea Radio Promotion Agency LG Electronics Jeju National University Casuh Slide 3

  4. Presentation Outline Applications for low data-rate in-body WBAN Topology for Implantable Devices Regulations for 400MHz MICS WBAN Channel model(CM2) Comparison of Modulations Design objective and Physical layer Functions Data Rate and Modulation for In-body Communication Proposed MAC architecture and Frame Structure Extended MAC Protocol based on proposed PHY Performance and Conclusion Emergency handling Mechanism Transmit Power Control Mechanism Coordinator Switch Mechanism Reference Slide 4

  5. Applications for Low-data-rateIn-body WBAN • Applications for Implantable BAN • Deep Brain Stimulator • Implantable Cardioverter Defibrillator • Pacemaker • Drug-Delivery Slide 5

  6. Topology for Implantable Devices D0 Wakeup D3 D2 C Data Wakeup Wakeup C D Data D1 [Indirect Transmission] [Coordinator / Device] • Maximum Number of Nodes • Under 10 Nodes in 2m (Address: 232 Nodes) • Star Topology • Indirect Transmission • Broadcast • Multi-hop Link Slide 6

  7. Regulations for 400MHz MICS • International Reference • ITU-R SA 1346, Sharing between the Meteorological Aids Service and Medical Implant Communications Systems(MICS) operating in the Mobile Service in the Frequency Band 401-406MHz • US standards • US FCC Regulations, available from www.fcc.gov : • 47CFR95.628 • FCC add adjacent spectrum(401~402 & 405~406 MHz) for MICS March 19, 2009, By report and order(FCC09-23) Slide 7

  8. WBAN Channel model(CM2) Nodes: Implant node, Body Surface node, External node Maximum output power limitation for MICS(402 ~ 405 MHz) ETSI: 25 μW ERP FCC & ITU-R: 25 μW EIRP Electrical properties of body tissues High dielectric constants, thickness, characteristic impedance High loss caused by power absorption, central frequency shift and radiation pattern destruction CM2 Model(S2): Implant to body surface PL(d)=PL0+10nⅹlog10(d/d0)+S CM2 Model(S3): Implant to external Combination of scenarios S2 and S6(or S7)

  9. Why FSK? GFSK 300 KHz -20 dBC 2FSK Power limited : Using 2FSK instead of BPSK BW limited : Using GFSK instead of 2FSK • Bandwidth & power limited system • Error probability of BPSK • Error probability of 2FSK Slide 9

  10. Why not M-ary FSK? • System configuration • CM2 400MHz Path Loss model • 10cm away from the body surface, FSPL can be added to CM2. • link budget • Carrier Frequency : 403.5MHz • BW : 300kHz • MCS • 2FSK – coherent / non-coherent • BPSK – hard decision • 4FSK – coherent / non-coherent • Noise Figure : 10dB • HW loss margin : 7dB • Thermal noise : -119.229dBm • Tx power : 25μW • Antenna Gain : 0dB • Simulation results under channel model 2 • BPSK, 2FSK, 4FSK Slide 10

  11. Modulation Index and BT • Output Spectrum (Modulation Index) • Output Spectrum (BT) • BT: 1 • BT: 0.5 • Modulation Index: 0.3 • Modulation Index: 0.2 • Performance Evaluation • Without FEC for implantable WBAN • Noise Figure (NF) = 10 dB and Modulation index is 0.3 • Band pass filter pass band: 240 kHz • RF topology: low intermediate frequency (IF) super heterodyne architecture with image reject mixers for flicker noise suppression Slide 11

  12. Why FEC? k bits or symbols Data block FEC encoding n Data Redundant k n-k Slide 12 Forward Error Correction (FEC) is a system meant to minimize the amount of digital data lost on transfer. Additional methods to diminish error-rates are ARQ, and Data Carousel, that are sometimes used together with FEC. Does not require a back-channel (as opposed to ARQ). Therefore, an excellent solution for multicast of medical information such as ECG.

  13. Channel description & System performance Performance assessment of different MCS Comparisons of BCH and RS 1) Coherent Rx and CM [2] 2) Reference: [1] – [7] Slide 13

  14. Design Objective and Proposed Physical Layer Functions For In-body WBAN • Design objective • Scalable packet size • Advantage : In highly attenuated in-body model, scalable block based transmission would be better than fixed packet based transmission. • Bitmap based data-block management • High reliability • Header : 16byte, BCH(128,120) • Data : variable block length (Max block FEC: BCH(255,247)) • Error control flow using block map based frame structure. • Power and Bandwidth efficiency modulation • Modulation and Functions Slide 14

  15. Proposed Data Rate and Modulation • 500 kbps is a minimum transmission data rate for 8bit RGB 256x256 pixel color image with 1 fps and 4:1 image compression ratio • JPEG compression ratio is typically 4:1 for CT and MR. • 32 channel ECG need minimum 192 kbps and 2 channel EMG needs 256 kbps. • Power efficient FSK Modulation • Band limited gaussian pulse shape filter • Improve spectrum efficiency at the cost of increased ISI • Cause elevated BER compared with a typical FSK • FEC for compensating the elevated BER • Extended Binary Primitive BCH Codes Slide 15

  16. Link Budget and Receiver Sensitivity * A. J. Johanson, ”Wireless communication with medical implants: Antenna and propagation,” ISSN 1402-8662,2004

  17. Proposed In-body MAC Architecture (IEEE 802.15.4) (IEEE 802.15.4) • Use IEEE 802.15.4 MAC and Extend Primitives • Primitives for Block based Error control • Extended Primitives make common MAC frame if errors exist Slide 17

  18. WBAN Concept for In-body devices

  19. MAC Channel Access • LBT (Listen before talk) • Coordinator must listen each channel (> 10ms) before transmitting • If idle channel is found by CCA, it periodically (< 10ms) transmits beacon frame to occupy the channel. • Wakeup sub-channel for implantable devices • MAC Frame Transmission • 32bit Block bitmap based transmission • Variable block size (variable FEC gain) • Acknowledgement • block retransmission, 8bit sequence number • MAC Header FEC • 1bit Flow Control • Pending frame or stop transmission • 48bit address information • 16bit BAN ID, 32bit transceiver ID Slide 19

  20. Frame Structure Slide 20

  21. Transmission Mechanism Slide 21

  22. Flow Control Slide 22

  23. Simulation Result (1) • PER comparison of variable packet size • Variable packet sizes are not issue under CM2 Channel • Block size depend on sending data size and variable block size reduced the zero padding bit for FEC Slide 23

  24. Simulation Result (2) Performance : BCH + Retransmission > Convolution Code > without FEC Complexity : Convolution Code > BCH + Retransmission > without FEC • Transmission efficiency • The Efficiency R is given by [11] • N :block message • B : the number of bits per block • L : information bits • H : message header Slide 24

  25. Implementation Example [SoC Development Platform] [SoC Layout and P&R] • Embedded 8 bit RISC microcontroller • 64kbyte e-flash and 64kbyte SRAM • Baseband supports for GFSK, BPSK, and GMSK • Triple band RF: MICS, 900MHz, and 2.4GHz Transceiver Back Power & Debug Module Semi-liquid Phantom for muscle [Ref: 13-15] : Compound of water, powdered polyethylene, Super stuff and NaCl [Test environment using prototype SoC] Slide 25

  26. Emergency Handling Mechanism and Security Service • Motivation • Support emergency handling mechanism for medical/healthcare application • Support security service for protecting patients data • Proposed Emergency Handling Mechanisms • Transmit Power Control Mechanism • Coordinator Switch Mechanism Slide 26

  27. Motivation From technical requirement document [08/0644r9] Capability of providing fast (<1 sec) and reliable reaction in emergency situations and alarm message, which have higher priority than others, shall be provided after the network has been set up. One such requirement is to transmit an “Emergency” condition that the BAN node has detected. In medical applications this might be BAN sensor detection of heart beat stoppage, excessively low or high blood pressure or temperature, excessively low or high blood glucose level in a diabetic patient. Another example may be battery dying in the BAN device. It is OK to not to engage in power consumption saving, while this transmission is in progress. It may be desirable to increase the transmit power for this type of transmission, to get through any kind of interference. To satisfy these requirements, we propose Transmit Power Control mechanism Slide 27

  28. Motivation From technical requirement document [08/0644r9] The BAN should be able to recover from link & node failures To satisfy these requirements, we propose Coordinator Switch mechanism In emergency situation, coordinator failure is very critical Coordinator Switch mechanism is designed for quickly recover coordinator failure Slide 28

  29. Security Service Inherits from IEEE 802.15.4 All security is based on 128bit key and AES-128 block encryption method Encryption/Authentication mode CCM* CTR a counter based encryption mode CBC-MAC cipher block chaining message authentication code

  30. Transmit Power Control Mechanism As stated in technical requirement document, we already made some consensus on the following transmit power control mechanism It may be desirable to increase the transmit power for this type of transmission, to get through any kind of interference.[08/0644r9] Problem definitions Reliable reaction in emergency situations and alarm message Fast reaction in emergency situations and alarm message Proposed transmit power control mechanism Asymmetric transmit power control mechanism Preemptive channel access mechanism Slide 30

  31. Transmit Power Control Mechanism Asymmetric transmit power control mechanism Coordinator specifies Max Transmit Power set for emergency frame and non-emergency frame Emergency Max Transmit Power Non-emergency Max Transmit Power In non-emergency situation, Coordinator sets Emergency Max Transmit Power and Non-emergency Max Transmit Power to the same value In Emergency situation, Coordinator increases Emergency Max Transmit Power and decreases Non-emergency Max Transmit Power More reliable transmission of emergency frame is possible Slide 31

  32. Transmit Power Control Mechanism Preemptive channel access mechanism Although channel is already occupied by non-emergency frame, DEV can transmit emergency frame to Coordinator Because Coordinator can receive emergency frame by capture effect if the received power of emergency frame is more stronger than that of non-emergency frame Slide 32

  33. Transmit Power Control Mechanism Preemptive channel access mechanism Collision Multiple frames transmitted simultaneously Arrive at the same receiver Capture effect One frame can survive the collision and can be successfully received Sender2 Sender1 Receiver Emergency Non-emergency capture Slide 33

  34. Transmit Power Control Mechanism Preemptive channel access mechanism Capture can occur for emergency frame arriving after the preamble time of non-emergency frame In IEEE 802.11a, SIR threshold is around 10 dB for 6Mbps [Ref: 12] “An Experimental Study on the Capture Effect in 802.11a Networks” Slide 34

  35. Transmit Power Control Mechanism Preemptive channel access mechanism Preemptive bit in PHY header indicates that the preemptive channel access is allowed or not Emergency frame shall set Preemptive bit to 0 Non-emergency frame shall set Preemptive bit to 1 When a frame with preemptive bit set to 1 is transmitted, the emergency frame can be transmitted regardless of the channel state But, in order to avoid the collision between multiple emergency frames, each preemptive channel access may be started after some randomized delay time, <TBD> Slide 35

  36. Transmit Power Control Mechanism Preemptive channel access mechanism under limited transmit power for regulation Coordinator can dynamically enable or disable the preemptive channel access Coordinator can choose the preemptive timeout that specifies the minimum time interval between consecutive preemptive channel access Slide 36

  37. Transmit Power Control Mechanism • Preemptive channel access mechanism using instant high transmit power • Coordinator can dynamically enable or disable the preemptive channel access • Coordinator can choose the preemptive timeout that specifies the minimum time interval between consecutive preemptive channel access • Limited transmit power can cause marginal link budget: 25 μW ERP or EIRP(WBAN regulation) • Even if transmit power in emergency conditions can violate the regulation, Nothing is more important than human life • Emergency conditions shell confine fatal signals only such as arrhythmia signal Slide 37

  38. Coordinator Switch Mechanism In emergency situation, coordinator failure is very critical For handling coordinator failure, backup coordinator is necessary D0 D0 D3 D3 D2 D2 C C BC BC D1 D1 Slide 38

  39. Coordinator Switch Mechanism Coordinator capable DEV indicates its capability to Coordinator by transmitting association request frame Coordinator transmits the Coordinator Switch timeout to Coordinator capable DEV by transmitting association response frame If Coordinator capable DEV does not receive any frame from Coordinator for Coordinator Switch timeout, it regards as coordinator failure Slide 39

  40. Coordinator Switch Mechanism Before the coordinator failure, Coordinator may designate Backup Coordinator by transmitting exchanging Coordinator Switch Request and Coordinator Switch Response frames Selection algorithm of Backup Coordinator may depend on either the power type (battery-power, main-power) of Coordinator capable DEV or the priority of the Coordinator capable DEV After coordinator failure is detected, Backup Coordinator transmits Coordinator Switch Announcement information element to other DEV in the following two ways, Beacon frame includes Coordinator Switch Announcement information element Coordinator Switch Announcement frame is individually transmitted to each DEV Slide 40

  41. Coordinator Switch Mechanism After receiving Coordinator Switch Announcement, DEV re-associates with Backup Coordinator Slide 41

  42. Conclusion Transceiver with error control enabled scalable frame block decreases retransmission packet size and increases duty efficiency Use 2FSK combined with block FEC at low data rate to let simple receiver structure and implementation Two emergency handling mechanism Transmit Power Control Mechanism Coordinator Switch Mechanism Emergency handling mechanism is independent on other proposals and also can be used with other emergency handling mechanisms together This presentation introduces key scheme to be applicable to a standard of WBAN Slide 42

  43. Reference • Kamya Yekeh Yazdandoost and Ryuji Kohno, “Channel Model for Body Area Network(BAN)”, 802.15-08-0780-09-0006, April 2009 • Sukor.M, Ariffin.S, “Performance Study of Wireless Body Area Network in Medical Environment,” Second Asia International Conference on, 2008 • doc. IEEE 802.15- 08-0-00-0006 • doc. IEEE 802.15-08-0689-00-0006 • B. Sklar, “Digital Communications 2nd Edition,” Prentice Hall. / A. Goldsmith, “Wireless Communications,” stanford university. • “Reed-Solomon codes for land mobile satellite channels,” Elec. letters, 15th Aug. 1991, vol. 27. No. 17 • J.A. Heller and I.M.Jacobs,”Viterbi Decoding For Satellite and Space Communication,” IEEE Trans. Commun.Technol., vol. COM19, no.5, October 1971, Fig.7, p. 84 ⓒ1971 IEEE • FCC add adjacent spectrum(401~402 & 405~406 MHz) for MICS March 19, 2009, By report and order(FCC09-23) • FCC, Medical implant communications, January 2003, http://wireless.fcc.gov/services/ index.htm?job=service_home&id=medical_implant • Arthur W. ASTRIN, Huan-Bang LI, and Ryuji KOHNO, “Standardization for Body Area Networks,” IEICE TRANS. COMMUN., Vol.E92-B, No. 2, pp. 366-372, February 2009 • Richard A.Comroe and D.J.Costello.Jr. , “ARQ Schemes for Data Transmission in Mobile Radio Systems,”,IEEE journal on selective areas in communications, vol. sac-2, No.4, July 1984 • Jeongkeun Lee, Wonho Kim, Sung-Ju Lee, Daehyung Jo, Jiho Ryu, Taekyoung Kwon, and Yanghee Choi, “An Experimental Study on the Capture Effect in 802.11a Networks,” in Proc. ACM WinTech 2007, Montreal, Canada, Sep. 2007. • FCC and Dr. William Scanlon, Queens University of Belfast, “Body Electrical properties” • Koichi lto, katsumi furuya, Yoshinobu Okano, Lira Hamada, “Development and characteristics of a biological tissue-equivalent phantom ”, Dec. 2000 • “The Characteristics of the Phantom Material”, http://www.rapa.or.kr/korean/data/kdt01b1502sh.htm Slide 43

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