CLEO can perform continuous GPS sensing for a year and a half efficiently enough to be sustained by just two AA batteries. In a typical mobile phone, Liu says, continuous GPS sensing would burn through the device’s battery in roughly six hours. (In practice, data from Wi-Fi base stations and cellular towers contribute to location information in mobile phones so GPS doesn’t always do all the heavy lifting.)
Microsoft’s Liu believes that low-power GPS systems on mobile phones could make continuous location logging feasible, which could make the device smarter. You could, for example, opt into a service that contributes to a database of noise pollution levels in your city. Or, if your smartphone kept a record of your driving habits, you might receive tailored directions or search results based on your usual walking or driving directions.
Location is a fundamental service for mobile computing. Typical GPS receivers, although widely available, consume too much energy to be useful for many applications. Observing that in many sensing scenarios, the location information can be post-processed when the data is uploaded to a server, we design a Cloud-Offloaded GPS (CO-GPS) solution that allows a sensing device to aggressively duty-cycle its GPS receiver and log just enough raw GPS signal for postprocessing. Leveraging publicly available information such as GNSS satellite ephemeris and an Earth elevation database, a cloud service can derive good quality GPS locations from a few milliseconds of raw data. Using our design of a portable sensing device platform called CLEO, we evaluate the accuracy and efficiency of the solution. Compared to more than 30 seconds of heavy signal processing on standalone GPS receivers, we can achieve three orders of magnitude lower energy consumption per location tagging.