(Image Credit: UC San Diego Jacobs School of Engineering)

Most current wearable devices use Bluetooth to communicate, but this can be wasteful due to a how difficult it is for the signal to pass through a user's body. This causes an effect called "path loss" whereby a signal is weakened on the way to its destination, as well as causing security worries due to the distance the signal travels around the user being susceptible to eavesdropping. 

A team led by Professor Patrick Mercier of the university's Department of Electrical and Computer Engineering has discovered a clever way to use the body itself as the medium for data transmission. 

Patrick Mercier, a professor in the Department of Electrical and Computer Engineering at UC San Diego, said: "In the future, people are going to be wearing more electronics, such as smart watches, fitness trackers and health monitors. All of these devices will need to communicate information with each other. Currently, these devices transmit information using Bluetooth radios, which use a lot of power to communicate. We’re trying to find new ways to communicate information around the human body that use much less power." 

Mercier and his team use magnetic fields to accomplish their groundbreaking feat; which shows path loss over ten million times lower than what is seen in tests with Bluetooth. The current prototype is based on two coils placed on the body which creates a magnetic field between them in a similar way to NFC technology. 

“This technique, to our knowledge, achieves the lowest path losses out of any wireless human body communication system that’s been demonstrated so far. This technique will allow us to build much lower power wearable devices,” said Mercier. 

The obvious use case for such technology is to enable health sensors from multiple parts of the body to communicate with one another. Current data transmission rate for the system is 1 Mbps – which sounds low – but is more than what's needed for dedicated sensors. 

Despite recent standards increasing the power-efficiency of Bluetooth, it will always have to work harder when it comes to wearable devices because of how the human body tends to absorb the electrical and magnetic waves broadcast through most wireless technologies. 

Jiwoong Park, a Ph.D student in Mercier’s Energy-Efficient Microsystems Lab, said: "A problem with wearable devices like smart watches is that they have short operating times because they are limited to using small batteries. With this magnetic field human body communication system, we hope to significantly reduce power consumption as well as how frequently users need to recharge their devices." 

It's not all great news, there is a slight limitation in that devices must be circular in order for the coils of insulated copper wire to create a path from one part to another using the body. A subsequent benefit is that signals which radiate away from the wearer's body soon dissipate which almost guarantees it cannot be intercepted. 

Wearable technology requires a new wireless standard which can increase battery life whilst reducing security risks, and this could be what fills that gap. 

Do you think magnetic fields offer the next step for wearable communication? Let us know in the comments.

 

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