Design implementation of low power MAC protocol for wireless body area network

DESIGN AND IMPLEMENTATION OF LOW POWER MAC PROTOCOL FOR WIRELESS BODY AREA NETWORK PAN RUI (Bachelor of Engineering (Hons.), National University of Singapore, Singapore) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2014 This page intentionally left blank Declaration I hereby declare that this thesis is my original work and it has been written by me in its entirety I have duly acknowledged all the sources of information which have been used in the thesis This thesis has also not been submitted for any degree in any university previously PAN RUI 13TH AUG 2014 iii This page intentionally left blank Design and Implementation of Low Power MAC Protocol for Wireless Body Area Network by Pan Rui Submitted to the Department of Electrical and Computer Engineering on 13th Aug 2014, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Abstract A wireless body area network (WBAN) is a network consists of wearable wireless computing devices Advances in low power integrated circuits make it possible to mount miniaturized sensor nodes on the human body to form such a network for collecting one’s physiological data, such as vital sign, movements etc In a WBAN system, a sensor node should not interfere users’ daily activities, and should be battery-powered to work for days or even months for a single charge This requires the sensor nodes to be in small size and consume low power In this dissertation, the hardware implementation and the medium access control (MAC) protocol design for WBAN systems are explored In the first part of this dissertation, a WBAN system with a real-time scalable network controller IC for multi-patient wireless vital sign monitoring is demonstrated The controller chip incorporates a light-weight TDMA MAC protocol assuming an ideal channel conditions between sensor nodes and a hub The system is scalable to accommodate multi-node and different applications such as ECG, blood pressure, or temperature, while achieving sufficient quality-of-service (QoS) for these applications A low-complexity silent node association process, which does not require special frame exchange, allows new nodes to join the network in real-time without intervening in normal network operation This makes the system suitable for network environments such as that in a hospital ward, in which vital monitoring of existing patients should not be interrupted by newly admitted patients A proprietary network controller IC is realized in 65nm CMOS technology, which consists of the light-weight TDMA MAC layer and a 2.4 GHz OOK RF transceiver Measured at an effective throughput of 18 kbps, the proposed system achieves a packet delivery rate (PDR) of > 99.9% The proposed system serves as a baseline design such that future systems can be built upon it Besides the effort in hardware design, the MAC protocol also plays an important v role An efficient MAC protocol design can ensure the application QoS and improve the energy efficiency of the sensor nodes The second part of this dissertation focuses on the MAC protocol design for a WBAN system When designing such a MAC protocol, a unique characteristic that affects the application QoS is the varying on-body communication channel conditions It makes the transmission between a sensor node and a body-worn coordinator vulnerable to poor channel conditions caused by body shadowing One possible solution to this is the use of relays where direct transmission to the hub is not possible The two-hop relay mechanism proposed in IEEE 802.15.6 standard can be divided into three processes, namely channel assessment, relaying node election and data relaying However as these three processes are initiated at different time intervals, simulations suggest that channel conditions actually vary between processes, which leads to data relaying failure In order to reduce the possibility of data relaying failure, a relay mechanism with predefined relaying nodes are introduced and evaluated against the relay mechanism proposed in IEEE 802.15.6 standard A predefined relaying node will be active during the data relaying process even if it is not elected Simulations show that the proposed relay mechanism is able to achieve 50% reduction in data relaying failure rate, which in turn improves the packet delivery rate The proposed relay mechanism is evaluated in a superframe structure Simulation shows that with the presence of the predefined relaying node, the network lifetime is extended by 8% To further improve the packet delivery rate, direct transmission in the relaying process is supported, and a dynamic scheduling algorithm is proposed to optimize slot allocation in the superframe for all nodes The proposed relay protocol achieves 21% improvements in network lifetime and 14% improvements in PDR with decreasing transmission powers from -10 dBm to -15 dBm Acknowledgments I would like to sincerely express my gratitude to my supervisors, Prof Xu Yong Ping and Dr Jaya Shankar Pathmasuntharam, for their patience, guidance, encouragement, continuous supporting and understanding I am also thankful to my labmates Chua Dingjuan, Zhao Wenfeng, Ng Kian Ann, Li Yongfu, Zhao Jianming, and Wu Tong, for all the technical discussions and encouragements throughout the years Special thanks to Chua Dingjuan and Zhao Wenfeng, for precious ideas on papers and testings, especially Chua Dingjuan, without whom this dissertation would not have been possible I would also like to thank MediaTek Singapore for the sponsorship of the chip fabrication Last but not the least, I would like to thank my family, especially my wife, for sharing the ups and downs throughout the years vii This page intentionally left blank Contents Abstract v Acknowledgements vii Contents ix List of Figures xiii List of Tables xv Introduction 1.1 Background of Wireless Body Area Network 1.2 Problem Statement 1.3 Research Objectives and Contributions 1.3.1 Research Objectives 1.3.2 Research Contributions 1.4 Organization of the Dissertation Literature Review 2.1 Background 2.1.1 Quality of Service 2.1.2 The Varying On-Body Channel Conditions 2.2 Review of Existing Works on Implementation of WBAN Systems 2.3 Review of Existing Works on Relay Protocols to Mitigate the Effects of the Varying On-Body Channel Conditions 2.4 Conclusion A Real-Time Scalable Network Controller IC for Multi-Patient Wireless Vital Sign Monitoring 3.1 Real-Time Scalable Light-Weight TDMA MAC Protocol ix 1 6 11 11 11 14 17 18 21 23 24 3.1.1 MAC Frames 25 3.1.1.1 MAC Header 26 3.1.1.2 MAC Payload 27 3.1.1.3 Cyclic Redundancy Check 28 3.1.2 MAC Functions 30 3.1.2.1 Silent node association 30 3.1.2.2 Monitoring process 31 3.1.2.3 Time Synchronization 33 3.2 System Design & Implementation 33 3.2.1 Network Controller IC 38 3.3 System Measurement 40 3.3.1 Measurement Setup 40 3.3.2 Measurement & QoS Analysis 41 3.4 Conclusion 45 OR-BAN: An Opportunistic Relay Protocol with Dynamic Scheduling in Wireless Body Area Network 47 4.1 Review of IEEE 802.15.6 Relay Mechanism 48 4.1.1 Simulation Setup 50 4.1.2 Simulation Result & Discussion 54 4.2 OR-BAN: An Opportunistic Relay Protocol with Dynamic Scheduling in Wireless Body Area Network 58 4.2.1 MAC Frames 59 4.2.1.1 MAC Header 62 4.2.1.2 MAC Payload 63 4.2.1.3 Cyclic Redundancy Check 64 4.2.2 MAC Functions 64 4.2.3 Dynamic Scheduling in the Normal Period 67 4.2.4 Evaluation of Proposed Relay Protocol 67 4.3 Conclusion 79 Conclusion and Future Works 81 5.1 Conclusion 81 5.2 Future Works 83 List of Publications 85 Energy Capacity (Joules)* Tx Power (Joules) Network Lifetime (days) 2.72 2.60 130 18720 3.44 3.12 3.09 144 3.00 4.52 4.15 4.95 5.01 11.98 9.29 21.95 Node Node Node Node Node (Joules) 78 Hub (Joules) (Joules) (Joules) (Joules) 53.26 2.75 2.28 2.99 48.14 3.10 2.49 43.68 4.03 53.03 8.81 *The hub and nodes are powered by 2x AA batteries each Predefined Relaying Node Dynamic Scheduling Direct Tx in the Relaying Period -10 Enabled Enabled Enabled 18720 -12 Enabled Enabled Enabled 158 18720 -15 Enabled Enabled Enabled 130 18720 -20 Enabled Enabled Enabled (dBm) CHAPTER OR-BAN: An Opportunistic Relay Protocol with Dynamic Scheduling in Wireless Body Area Network Table 4.5: Energy consumption at different transmission powers with initial schedule CHAPTER OR-BAN: An Opportunistic Relay Protocol with Dynamic Scheduling in Wireless Body Area Network 4.3 Conclusion In this chapter, we showed that the relay mechanism proposed by IEEE 802.15.6 standard can be improved by activating a predefined relaying node with about 50% reduction in the DRFR, which leads to improvements in the PDR The proposed relay mechanism is then evaluated in a superframe structure with a dynamic scheduling algorithm proposed for periodic applications The algorithm is based on the packet delivery rate of each node Simulation shows that as transmission power drops, the average packet delivery rate for each node drops, but it can still be maintained above about 90% with transmission powers of -10 dBm, -12 dBm, and -15 dBm However, with a transmission power of -20 dBm, the packet delivery rate of all nodes drops below 80% except that of the node 2, which is caused by excessive data relaying failures Therefore, excessive energies are wasted on idling listening for the hub and all nodes, which leads to shortened network lifetime Besides, each node gains different improvements on the data relaying failure rate and packet delivery rate with certain transmission power 79 This page intentionally left blank Chapter Conclusion and Future Works 5.1 Conclusion In a WBAN system, the sensor nodes need to be of small footprint and consume low power such that user’s daily activity is not interfered, and long term usage for months or even years is possible This requires the designers to consider various aspects when designing such a system This dissertation explores the design issues in two aspects, i.e hardware implementation and MAC protocol design that addresses the varying on-body channel conditions caused by human motion, which has been proven to have great impact on application QoS and energy efficiency The first part of the dissertation demonstrated a WBAN system with a real-time scalable network controller IC for multi-patient wireless vital sign monitoring In the proposed system, star network topology is adopted A customized light-weight time division multiple access (TDMA) media access control (MAC) protocol is implemented, based on which a programmable base station centrally controls the network and application parameters, including beacon interval for network synchronization, transmission slot duration and sampling frequency for different applications This implies that the system is scalable to accommodate 81 CHAPTER Conclusion and Future Works multi-node and different applications such as ECG, blood pressure, or temperature, while achieving sufficient quality-of-service (QoS) for these applications A low-complexity silent node association process, which does not require special frame exchange, allows new nodes to join the network in real-time without intervening in normal network operation This makes the system suitable for network environments such as that in a hospital ward, in which vital monitoring of existing patients should not be interrupted by newly admitted patients To enhance the communication reliability, ACK-retry mechanism is adopted, and the (21,16) Hamming algorithm and Manchester coding are implemented for error correction and channel coding, respectively A proprietary network controller IC measured 0.5 mm by mm with a supply voltage of 1.2V is realized in 65nm CMOS technology, which consists of the light-weight TDMA MAC layer and a 2.4 GHz OOK RF transceiver Measured at an effective throughput of 18 kbps, the proposed system achieves a PDR of > 99.9% The second part of this dissertation describes an opportunistic relay protocol by considering the varying on-body channel conditions, which is a unique characteristic in WBAN It affects not only the application QoS, but also the system energy efficiency as extra energy needs to be expended to compensate the effects of the varying channel conditions One possible solution to this issue is the use of relays In IEEE 802.15.6 standard-alike relay mechanisms, there are three processes, namely channel assessment, relaying node election and data relaying The problem of this approach is that these three processes are initiated at different time intervals, in which channel conditions may vary from one process to another Therefore, the elected relaying node may experience poor channel conditions to the hub or the relayed node during data relaying, which leads to data relaying failures In order to reduce the possibility of data relaying failure, a relay mechanism with predefined relaying nodes are introduced A predefined relaying node will be active during the data 82 CHAPTER Conclusion and Future Works relaying process even if it is not elected Simulations show that the proposed relay mechanism is able to achieve 50% reduction in data relaying failure rate, which in turn improves the packet delivery rate The proposed relay mechanism is evaluated in a superframe structure Simulation shows that with the presence of the predefined relaying node, the network lifetime is extended by 8% To further improve the PDR, direct transmission in the relaying process is supported, and a dynamic scheduling algorithm is proposed to optimize slot allocation in the superframe for all nodes The proposed relay protocol achieves 21% improvements in network lifetime and 14% improvements in PDR with decreasing transmission powers from -10 dBm to -15 dBm 5.2 Future Works To further examine the proposed relay protocol, on-body testing needs to be performed with the protocol implemented in a programmable platform, such as a FPGA development board A more sophisticated node association process needs to be proposed and implemented, for which CSMA/CA can be adopted The (21,16) Hamming algorithm shall be replaced by BCH coding to further enhance the communication reliability, which is recommended by IEEE 802.15.6 standard And a more energy efficient clock and data recovery mechanism should be adopted to further reduce system energy consumption With all this, an improved version of a sensor node design can be realized with a system-on-chip (SoC) platform to provide a single chip solution for periodic applications, such as vital sign and motion monitoring Other aspects in the MAC layer design should also be explored, such as the coexistence of different WBAN systems sharing the same frequency band 83 This page intentionally left blank List of Publications [1] R Pan, D Chua, J S Pathmasuntharam and Y P Xu, ”A Wireless Body Area Network Based Cableless ECG Acquisition System”, Accepted as conference paper to Conference of the IEEE Engineering in Medicine and Biology Society 2014 [2] R Pan, D Chua, J S Pathmasuntharam and Y P Xu, ”An Opportunistic Relay Protocol with Dynamic Scheduling in Wireless Body Area Network”, Journal submitted to IEEE Sensors Journal [3] R Pan, D Chua, J S Pathmasuntharam and Y P Xu, ”A Real-Time Scalable Network Controller IC for Multi-Patient Wireless Vital Signs Monitoring”, Journal submitted to TCAS-II and under revision [4] D Chua, R Pan and Y P Xu, ”A 1-Mbps 433.92-MHz ISM Transmitter with SAR-TDC Frequency Calibration”, Journal recommended for resubmission to TCAS-I and under revision [5] D Chua, R Pan and Y P Xu, ”A 2.4-GHz 0.2-nJ/bit Super-Regenerative Receiver with Automatic Quench Alignment”, Journal submitted to TCAS-II 85 This page intentionally left blank Bibliography [1] “IEEE Standard for Local and metropolitan area networks - Part 15.6: Wireless Body Area Networks,” IEEE Std 802.15.6-2012, pp 1–271, Feb 2012 [2] “IEEE Standard for Local and metropolitan area networks–Part 15.4: Low-Rate Wireless Personal Area Networks (LR-WPANs),” IEEE Std 802.15.4-2011 (Revision of IEEE Std 802.15.4-2006), pp 1–314, Sept 2011 [3] C Li, H.-B Li, and R Kohno, “Performance Evaluation of IEEE 802.15.4 for Wireless Body Area Network (WBAN),” in IEEE International Conference on Communications Workshops (ICC Workshops), June 2009, pp 1–5 [4] Bluetooth SIG (Hrsg.): Specification of the Bluetooth System: Covered Core Package version:4.1 [Online] Available: https://www.bluetooth.org/DocMan/ handlers/DownloadDoc.ashx?doc id=282159 [5] Samsung Gear Technical Specifications [Online] Available: http: //www.samsung.com/us/mobile/wearable-tech/SM-R3800GNAXAR [6] Pebble Smartwatch Technical Specifications [Online] Available: https: //getpebble.com/discover [7] Cookoo Watch Technical Specifications [Online] Available: http://www cookoowatch.com/Product Specification.html [8] Martian Watch Technical Specifications [Online] Available: http://www martianwatches.com/products/tech-specs/ [9] E Mackensen, M Lai, and T Wendt, “Performance analysis of an Bluetooth 87 BIBLIOGRAPHY Low Energy sensor system,” in 2012 IEEE 1st International Symposium on Wireless Systems (IDAACS-SWS), Sept 2012, pp 62–66 [10] C Gomez, J Oller, and J Paradells, “Overview and Evaluation of Bluetooth Low Energy: An Emerging Low-Power Wireless Technology,” Sensors, vol 12, no 9, pp 11 734–11 753, 2012 [11] M Patel and J Wang, “Applications, challenges, and prospective in emerging body area networking technologies,” IEEE Wireless Communications, vol 17, no 1, pp 80–88, February 2010 [12] S Obayashi and J Zander, “A body-shadowing model for indoor radio communication environments,” IEEE Transactions on Antennas and Propagation, vol 46, no 6, pp 920–927, Jun 1998 [13] S Cotton, A McKernan, A Ali, and W Scanlon, “An experimental study on the impact of human body shadowing in off-body communications channels at 2.45 GHz,” in Proceedings of the 5th European Conference on Antennas and Propagation (EUCAP), April 2011, pp 3133–3137 [14] M Kim and J.-i Takada, “Experimental investigation and modeling of shadow fading by human movement on body surface propagation channel,” in IEEE Antennas and Propagation Society International Symposium, 2009 APSURSI ’09., June 2009, pp 1–4 [15] S Cotton, “A Statistical Model for Shadowed Body-Centric Communications Channels: Theory and Validation,” IEEE Transactions on Antennas and Propagation, vol 62, no 3, pp 1416–1424, March 2014 [16] Y Ge, J W Kwan, J Pathmasuntharam, Z Di, T S P See, W Ni, C W Kim, T M Chiam, and M Ma, “Performance benchmarking for wireless body area networks at 2.4 GHz,” in 2011 IEEE 22nd International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), Sept 2011, pp 2249–2253 88 BIBLIOGRAPHY [17] F Di Franco, C Tachtatzis, B Graham, M Bykowski, D Tracey, N Timmons, and J Morrison, “The effect of body shape and gender on wireless Body Area Network on-body channels,” in 2010 IEEE Middle East Conference on Antennas and Propagation (MECAP), Oct 2010, pp 1–3 [18] M Quwaider, J Rao, and S Biswas, “Body-posture-based dynamic link power control in wearable sensor networks,” IEEE Communications Magazine, vol 48, no 7, pp 134–142, July 2010 [19] B Otal, L Alonso, and C Verikoukis, “Highly reliable energy-saving mac for wireless body sensor networks in healthcare systems,” IEEE Journal on Selected Areas in Communications, vol 27, no 4, pp 553–565, May 2009 [20] H Chebbo, S Abedi, T A Lamahewa, D Smith, D Miniutti, and L Hanlen, “Reliable Body Area Networks using relays: Restricted Tree Topology,” in 2012 International Conference on Computing, Networking and Communications (ICNC), Jan 2012, pp 82–88 [21] Channel Model for Body Area Network (BAN) [Online] Available: https: //mentor.ieee.org/802.15/dcn/08/15-08-0780-09-0006-tg6-channel-model.pdf [22] Castalia: Wireless Sensor Network Simulator [Online] Available: https: //castalia.forge.nicta.com.au/index.php/en/ [23] NICTA homepage [Online] Available: http://www.nicta.com.au/ [24] A Boulis, Y Tselishchev, L Libman, D Smith, and L Hanlen, “Impact of Wireless Channel Temporal Variation on MAC Design for Body Area Networks,” ACM Trans Embed Comput Syst., vol 11, no S2, pp 51:1–51:18, Aug 2012 [Online] Available: http://doi.acm.org/10.1145/2331147.2331161 [25] A Burns, B Greene, M McGrath, T O’Shea, B Kuris, S Ayer, F Stroiescu, and V Cionca, “SHIMMERTM - A Wireless Sensor Platform for Noninvasive Biomedical Research,” IEEE Sensors Journal, vol 10, no 9, pp 1527–1534, Sept 2010 89 BIBLIOGRAPHY [26] L Mo, S Liu, R Gao, D John, J Staudenmayer, and P Freedson, “Wireless Design of a Multisensor System for Physical Activity Monitoring,” IEEE Transactions on Biomedical Engineering, vol 59, no 11, pp 3230–3237, Nov 2012 [27] A.-W Wong, D McDonagh, G Kathiresan, O Omeni, O El-Jamaly, T.-K Chan, P Paddan, and A Burdett, “A 1V, Micropower System-on-Chip for Vital-Sign Monitoring in Wireless Body Sensor Networks,” in IEEE International Solid-State Circuits Conference, 2008 ISSCC 2008 Digest of Technical Papers., Feb 2008, pp 138–602 [28] J Cheng, L Xia, C Ma, Y Lian, X Xu, C Yue, Z Hong, and P Chiang, “A near-threshold, multi-node, wireless body area sensor network powered by RF energy harvesting,” in IEEE Custom Integrated Circuits Conference (CICC), Sept 2012, pp 1–4 [29] Y Zhang, F Zhang, Y Shakhsheer, J Silver, A Klinefelter, M Nagaraju, J Boley, J Pandey, A Shrivastava, E Carlson, A Wood, B Calhoun, and B Otis, “A Batteryless 19 µW MICS/ISM-Band Energy Harvesting Body Sensor Node SoC for ExG Applications,” IEEE Journal of Solid-State Circuits, vol 48, no 1, pp 199–213, Jan 2013 [30] R D’Errico, R Rosini, and M Maman, “A Performance Evaluation of Cooperative Schemes for On-Body Area Networks Based on Measured Time-Variant Channels,” in 2011 IEEE International Conference on Communications (ICC), June 2011, pp 1–5 [31] H Feng, B Liu, Z Yan, C Zhang, and C W Chen, “Prediction-based dynamic relay transmission scheme for Wireless Body Area Networks,” in 2013 IEEE 24th International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), Sept 2013, pp 2539–2544 [32] M Maman and L Ouvry, “BATMAC: An adaptive TDMA MAC for body area 90 BIBLIOGRAPHY networks performed with a space-time dependent channel model,” in 2011 5th International Symposium on Medical Information Communication Technology (ISMICT), March 2011, pp 1–5 [33] F Di Franco, C Tachtatzis, B Graham, M Bykowski, D Tracey, N Timmons, and J Morrison, “The effect of body shape and gender on wireless Body Area Network on-body channels,” in 2010 IEEE Middle East Conference on Antennas and Propagation (MECAP), Oct 2010, pp 1–3 [34] D Lewis, “802.15.6 Call for Applications - Response Summary,” , Tech Rep., 2008 [Online] Available: http://https//mentor.ieee.org/802.15/file/08/15-080407-00-0006-tg6-applications-summary.doc [35] B Zhen, M Patel, S Lee, E Won, Technical Requirements Document,” Available: , and A Astrin, Tech Rep., “TG6 2008 [Online] https://mentor.ieee.org/802.15/dcn/08/15-08-0644-09-0006-tg6- technical-requirements-document.doc [36] National University Hospital, Singapore [Online] Available: http://www.nuh.com.sg/patients-and-visitors/patients-and-visitorsguide/choice-of-accomodation/ward-types.html [37] Cyclic redundancy check [Online] Available: http://en.wikipedia.org/wiki/ Cyclic redundancy check [38] V Jindal Design of Hamming Code Using Verilog HDL [Online] Available: http://varunjindalblog.files.wordpress.com/2010/07/efy-hammingcode.pdf [39] J G Proakis, Digital Communications, 4th ed New York: McGraw-Hill, 2001 [40] O Omeni, A Wong, A Burdett, and C Toumazou, “Energy Efficient Medium Access Protocol for Wireless Medical Body Area Sensor Networks,” IEEE Transactions on Biomedical Circuits and Systems, vol 2, no 4, pp 251–259, Dec 2008 91 BIBLIOGRAPHY [41] N Desai, J Yoo, and A Chandrakasan, “A scalable 2.9mW 1Mb/s eTextiles body area network transceiver with remotely powered sensors and bi-directional data communication,” in IEEE International Solid-State Circuits Conference Digest of Technical Papers (ISSCC), Feb 2013, pp 206–207 92 ... This page intentionally left blank Design and Implementation of Low Power MAC Protocol for Wireless Body Area Network by Pan Rui Submitted to the Department of Electrical and Computer Engineering... fulfillment of the requirements for the degree of Doctor of Philosophy Abstract A wireless body area network (WBAN) is a network consists of wearable wireless computing devices Advances in low power. .. event-driven simulator for wireless sensor networks, body area networks and general networks of low- power embedded devices [22] The simulator is developed by Australia’s Information Communications