Wearable Antennas for Body-Centric Wireless Networks

Communications on the human body is a relatively unexplored commodity for the personal and mobile communications community. Up to now mobile phone technologies have allowed the user to talk anytime anywhere. But in the developed world this market is becoming saturated and so much has been invested into providing third generation phones with multimedia services. Cameras and low capacity MP3 players are now standard. What does the future hold? The big vision is of people wearing a multitude of sensors, processors, data storage for health or occupational or entertainment reasons and all of these being connected either by wireless or by wires in special clothing. These units may even be inside the body to provide medical solutions such as automatic drug metering and bladder control etc. The well known mobile phone with Bluetooth headset is an example of a wireless on-body link. The famous white iPod headset is perhaps an example of a wired system that needs to be replaced by wireless. Apple, the makers of the iPod, and Nike have recently agreed to collaborate on specially designed footwear that would allow the wearer to use their iPod to monitor time, calories burned and pace, and which uses a wireless communication link, between the iPod and the shoe. These examples show the way that technology is moving in the mass market. In addition, for some time now both the military and the special services, such as firefighters, have been using on-body systems to support their users in various hazardous environments and the use of wireless to remove or reduce the wiring harness is important. What is needed to make the big vision happen? Manufacturers will always simply use existing systems for new applications. The use of Bluetooth for the mobile phone headset is an example of this. It is a wireless system developed for another use, namely connection of peripherals to computers. But to optimise the operation, that is to improve the reliability and reduce battery consumption, requires a deeper understanding of both the radiowave propagation channel on the body and how to design the antennas. In a previous EPSRC grant the University of Birmingham and Queen Mary University of London, began this pioneering work of understanding the radio channel and identifying the factors important in antenna design. Much has been uncovered via extensive measurements of the way in which the channel and hence the received signal fades when the body moves have been made and the underlying statistics determined. However the research programme has only been working at the Bluetooth frequency, 2.45GHz, and mainly been characterising narrowband channels, but not the kinds of data rates needed in communications of live video. The proposed research is necessary to move the position forward to include more work on the design of optimised antennas both for this frequency and for others. For example, the best radiation pattern will be determined using statistical methods for a range of body types and body postures, and various frequencies, including much higher ones than examined so far. For example, operation at 40 or 60GHz would give the possibility of very high data rates and also very low interference between body networks close to each other, but will suffer from fading problems. Antenna diversity is a well known technique for fading reduction. Its use on the body will be investigated at various frequencies. The release of the spectrum from 3 to 10 GHz by the FCC has made ultra wideband systems a real possibility and its high capacity potential, low power and good anti-fading properties make it ideal for future on-body systems. However all of the antennas so far made are too big for realistic on-body use. Design of small wearable types will be investigated. Finally antennas for on body communications throw up immense challenges for computational methods and improved techniques will be investigated to support the whole research programme.