Networking issues in medical implant communication

IEEE 802.15 working group established a new task group, body area network (TG-BAN), to develop short range wireless technology in and around human body recently. This paper investigates networking issues in implant communications at 2.4 GHz frequency band. The object is better understanding of medical implant networks and how and where to start TGBAN work. We applied IEEE 802.15.4b and 802.15.4a-chirp spread spectrum (CSS) for implant communications. We derived a path loss model in the layered body and found two unique issues: clear channel assessment (CCA) of implant devices, interference from neighbor piconet in adjacent channel, and multihop long distance communication. All of them can be attributed to the rapid attenuation of electromagnetic wave through lossy tissue, which is about 30 dB more than the free space propagation. The carrier sense multiple access mechanism and transmit mask of 802.15.4b cannot be directly adopted. The modulation of 802.15.4a-CSS is robust to the interference from adjacent channel. A time division based MAC protocol should be considered by TG-BAN. Instead of routing among implant devices, a simple two-hop protocol which uses a body surface forwarder was presented and verified for long distance implant communications.