  Recent advances in intelligent sensors, microelectronics and integrated
circuit, system-on-chip design and low power wireless communication introduced
the development of miniaturised and autonomous sensor nodes. These tiny sensor
nodes can be deployed to develop a proactive Body Sensor Network (BSN). The
rapid advancement in ultra low-power RF (radio frequency) technology enables
invasive and non-invasive devices to communicate with a remote station. This
communication revolutionizes healthcare system by enabling long term health
monitoring of a patient and providing real time feedback to the medical
experts. In this paper, we present In-body and On-body communication networks
with a special focus on the methodologies of wireless communication between
implanted medical devices with external monitoring equipment and recent
technological growth in both areas. We also discuss open issues and challenges
in a BSN.
