Characterization of Communication Mechanisms for Implantable Body Sensor Networks Focusing on Physical layer and Medium Access Control Sub-layer

The use of wireless sensor networks (WSN) in health-care has been rapidly increased in the last few years. Miniaturization of sensor nodes, in-body data communication, bio-compatibility are the main outcomes of the on-going extensive research on nano-technology, wireless communication and bio-medical engineering, respectively. Sensing of various life-critical physiological signals such as heart-rate, blood-pressure, blood-glucose level, is made possible with miniaturized implantable wireless bio-sensors. Challenging requirements of WSN in health-care applications have resulted in the advent of a specific type of WSN called Implantable body sensor network (IBSN), in which the sensor nodes are implanted either subcutaneously or by an invasive surgery into the patient’s body. These sensor nodes continuously monitor the physiological signals which is necessary for the patients with life-threatening diseases such as epilepsy. Life-critical implantable medical devices (IMD) such as pace-makers and neural stimulators, are also connected to the IBSN. A closed control loop of medical devices is envisioned through a network of IMD and biosensors using IBSN, in which the IMDs are programmed for different types of therapies through wireless channel, based on the real-time response of the patient by continuously monitoring the medical symptoms with the implantable bio-sensors. IBSN is less researched compared to the body sensor network (BSN) where the wireless communication between sensor nodes takes place on the surface of the body. Extensive research on characterizing the communication mechanisms for IBSN is needed to standardize a reliable RF communication within the human body. In order to create a reliable and energy-efficient sensor network, two main layers of the Open System Interconnection (OSI) network model is required. The physical layer which is aimed at unification of the hardware requirements in a network to enable the successful transmission of data. The medium access control (MAC) sub-layer that is aimed at controlling the access to the wireless channel, which directly affects the network performance and energy efficiency of the nodes. This master thesis focuses on characterizing the physical layer and MAC sub-layer with different configurations of IBSN by means of software simulation and hardware experimentation. Two main state-of-the-art mechanisms are focused namely Medical Implant Communication Service (MICS) band specifications in the physical layer and wake-up radio integration in the MAC sub-layer which enables globally standardized communication strategies for IBSN and ultra-low power communication with reliable network performance respectively. These mechanisms are studied and characterized for different IBSN scenarios with a bio-medical implant in this thesis work. . As a result, an optimum configuration of the physical layer and MAC sub-layer for the IBSN is found. The added-value of wake-up radio in MAC layer and the effect of MICS band configurations in physical layer and MAC layer are identified. The evaluation results will also indicate the potential drawbacks in the existing configurations at physical and MAC layers of BSN, and identify why the existing BSN mechanisms cannot be used for IBSN scenarios. Possible solutions to overcome these drawbacks are suggested for the future research work.