Everyone seems to insist on installing cameras everywhere in their homes these days, which seems incongruous with the ongoing privacy crisis – but it's a post for another time. Today, we are talking about allowing these cameras to send high definition video signals wirelessly without killing their small batteries. A new technique makes video broadcasting more efficient by 99%, which can make the batteries completely useless.
Cameras found in smart homes or wearables need to transmit HD video, but it takes a lot of power to process that video, and then transmit encrypted data over Wi-Fi. Small devices leave little room for batteries , and they will need to be recharged frequently if they are constantly being broadcast. Who has time for that?
The idea behind this new system, created by a team at the University of Washington led by prolific researcher Shyam Gollakota, is not fundamentally different from some others that currently exist. Low flow devices, such as a digital thermometer or motion detector, may be called backscattering to send a low power signal consisting of a few bytes.
Backscattering is a means of sending a signal that requires very little power, because what actually transmits power is not the device that transmits the data . A signal is sent from a source, for example a router or a telephone, and another antenna essentially reflects this signal, but modifies it. By flashing it, you can indicate 1's and 0's, for example.
The UW system attaches the camera output directly to the output of the antenna, so that the brightness of a pixel is directly correlated to the length of the reflected signal. A short pulse means a dark pixel, a longer one is lighter and the longer one indicates a blank.
Intelligent handling of video data by the team has reduced the number of impulses needed to send a full video image, sharing some data between pixels at the same time. a "zigzag" sweep (from left to right, then from right to left) model. To get the color, each pixel must successively receive its color channels, but this can also be optimized.
The assembly and rendering of the video perform at the reception, for example on a phone or monitor, where the current is more abundant.
In the end, an HD color signal at 60FPS may have less Watt power, and a more modest but nevertheless very useful signal – say 720p at 10FPS – can be sent for less than 80 microwatts. This is a huge reduction in energy consumption, mainly achieved by eliminating the entire analog-to-digital converter and on-chip compression. At these levels, you can basically pull all the power you need directly out of the air.
They set up a demonstration device with ready-to-use components, but without custom chips, they will not reach these
microwatt power levels; again, the technique works as described. The prototype helped them determine what type of sensor and chip package would be needed in a dedicated device.
Of course, it would be a bad idea to explode video images in the ether without any compression; Fortunately, the way data is encoded and transmitted can easily be changed to be meaningless to an observer. Essentially, you would simply add a known interference signal from both devices before transmission, and the receiver could subtract it.
Video is the first app the team thinks of, but there's no reason why its efficient, fast backscatter transmission technique can not be used for non-video data .
The technology is already licensed to Jeeva Wireless, a start-up founded by researchers from UW (including Gollakota) who is already working on marketing another low-power wireless device. You can read the details of the new system in their paper, presented last week at the Symposium on Designing and Implementing Networked Systems.