Components and Network Architecture for Galvanic Coupled Cyber Physical Body Network

1. Galvanic Coupled Cyber-Physical Body Sensor Network MeenupriyaSwaminathan & Kaushik R. Chowdhury {meenu, krc} @ece.neu.edu Future Research Challenges The Promise of Implanted Sensors Traffic to/from node A Access Point Implementation of Physical Layer Traffic to/from node B • Future health-care relies on autonomous sensing of physiological signals and controlled drug delivery • Need for implanted Cyber – Physical Body Sensor Network (CP-BN) that can wirelessly communicate with an external control point Traffic to/from node C Objective: Establishing reliable & energy efficient CP-BN physical layer Extra-body Network Skin Fat Muscle Channel Capacity Topology Data Transfer Access Point • Outcome: • Fewer Relays • Energy saving • Higher data-rate Optimizing Node Placement Coupler • Building transmitter and receiver circuits with suitable modulation schemes that maximizes transfer rate • Studying the impact of realistic noise figures on capacity RF Transceiver Signal Processing Memory Ground RF Link Data Aggregation Node A Controller Controller Human Body Coupler Signal Processing Implant GC Link Establishing path from node to controller Guiding signal through body Ground Data Retrieval Relays Relay Proactive care & increased longevity Remote diagnosis & care Coupler Signal Processing Memory Lower health care cost GC Link Ground Physical Protocol Sensor/Actuator Node B Coupler Link Quality Analysis Signal Processing Sensor Coupler Intra-body Network Ground Signal Processing Implant Ground Why Galvanic Coupled CP-BN Storage & Fault Detection CSMA & BES RF Link Data Transfer Rate Adaptation, Scaling Node C • CP-BN Implanted node • Existing RF based BNs • not suitable for human tissues containing water • consume more power • does not propagate inside body tissues • Galvanic coupled CP-BN • mimics body’s natural signalling (low • frequency signals) • low interference as energy is confined • within body • consumes two orders of magnitude less energy … On Surface node Channel Model GC Link, Topology, Modulation Multiplexing, Synchronization Channel Access & Topology control Data Aggregation Relay Self Adaptation Synchronization Controller RF Queuing Data Retrieval Relay to Controller GC Link Protocol Design at Network Layer Galvanic Coupling Node to Relay GC Link 10-6 10-5 10-4 10-3 (J) • The spatio-temporal distribution should be analyzed and leveraged for multiple channel access Eg. TDMA • The network should distinguish critical situations from normal deviations based on correlations derived from routine activities Eg. High heart rate from heavy activity vs emergency RF Link Components and Network Architecture for Galvanic Coupled Cyber Physical Body Network Signal Propagation Through Human Tissue – Our Models CP-BN Test-bed How Galvanic Coupling Works • CP-BN operation and performance needs to be • Evaluated by building test-beds using • Human phantoms • Animal experiments • Clinical trials • Injects low power electrical signal to the tissues • Weak secondary currents carry data to receiver • Signal propagates radially across multiple tissues • & suffer losses We constructed a 2-port equivalent circuit model & FEM based ANSYS HFSS simulation suite of human arm using electrical properties of tissues [1]. Acknowledgement Support: U.S. National Science Foundation (Grant No. CNS-1136027). Thanks to our collaborators GunarSchirner, Northeastern University and Ferran Cabrera, UniversitatPolit`ecnica de Catalunya, Barcelona, Spain. • obtained an estimate for observed noise and achievable data rates • identified optimal transmission frequency and electrode placements • under varying tissue dimensions • skin to muscle & intra-muscle links showed lower loss than on-skin links References [1] ICNIRP (International Commission on Non-Ionizing Radiation Protection). 1998. Guidelines for limiting exposure to time-varying electric, magnetic, & electromagnetic fields (up to 300 GHz). [2] M Swaminathan, FS Cabrera, G Schirner, and K R Chowdhury, Characterization and Signal Propagation Studies for Wireless Galvanic Coupled Body Sensors, IEEE Journal on Selected Areas in Communications, under review. Galvanic Coupling on Skin (a) Front View (b) Cross Section Channel gain for on skin GC-links Electrical and Computer Engineering Department, Northeastern University, Boston, MA 02115 USA.