{"id":3530,"date":"2011-07-08T14:18:39","date_gmt":"2011-07-08T14:18:39","guid":{"rendered":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/?p=3530"},"modified":"2011-07-19T20:41:22","modified_gmt":"2011-07-19T20:41:22","slug":"using-body-coupled-communication-as-a-wireless-body-area-network-3","status":"publish","type":"post","link":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/using-body-coupled-communication-as-a-wireless-body-area-network-3\/","title":{"rendered":"Using Body Coupled Communication as a Wireless Body Area Network"},"content":{"rendered":"

To achieve comfortable form factors for wireless medical devices, battery size, and thus power consumption, must be curtailed.\u00a0 Often the largest power consumption for wireless medical devices is in storing or transmitting acquired data.\u00a0 Body area networks (BAN) can alleviate power demands by using low-power transmitters to send data \u201clocally\u201d around the body to receivers that are around areas of the body that allow for larger form factors, like the wrist or the waist.\u00a0 These receivers, which have larger power budgets, can then process and store the data or send it elsewhere using higher power transmitters.<\/p>\n

Body coupled communication (BCC) shows great potential for forming a BAN.\u00a0 Two-node BCC works by forming two capacitive links between a transmitter and a receiver, creating a circuit loop.\u00a0 One of these links is created by both the transmitter and receiver capacitively coupling to the body, effectively using the body as a low resistance channel between the respective capacitors.\u00a0 The second link is created by both the transmitter and receiver coupling to the environment, or \u201cearth ground,\u201d and using it as a return path.\u00a0 Larger BANs can be made by coupling additional nodes to both the body and the environment.<\/p>\n

A model for implantable BCC has been developed in which the electrodes couple to the body and use the body as a lossy transmission line.\u00a0 This model was tested by placing all four electrodes on the skin of a human, simulating how the electrodes would couple to body if they were implanted.\u00a0 Signals were still able to be transmitted and received.<\/p>\n

The BCC channel\u2019s attenuation varies with body position and distance between receiver and transmitter.\u00a0 Thus communication schemes that encode data with frequency or phase modulation work best.\u00a0 Both FSK and PM binary signals have been successfully sent and received using both the traditional BCC and the implantable model.<\/p>\n\n\t\t