US: Location applications reduce battery life in a smartphone or tablet. To address this issue, a team led by principal researcher Jie Liu at Microsoft Research is using a concept for location services that involves offloading some of the data and calculations to consume far less power. They have offloaded some of the work to the cloud. Their GPS system collects only a few milliseconds of information from satellites. The information is combined with information from public, online databases to calculate the device”s past locations.
“We built an experimental platform using WWVB [the station used by radio-controlled clocks in North America to synchronize themselves] time synchronization and a GPS front end,” according to the team. “On this platform, sensing a GPS location takes more than three orders of magnitude less energy than GPS on mobile phones,” the team stated.
The researchers moved to offload some of the work to the cloud, naming their platform, CLEO (Cultivating the Long tail in Environmental Observations). “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.”
They said that by 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. They presented their research in Toronto at the ACM Conference on Embedded Networked Sensor Systems (SenSys).
Their paper was titled “Energy Efﬁcient GPS Sensing with Cloud Ofﬂoading,” by Jie Liu, Bodhi Priyantha, Ted Hart, Heitor Ramos, Antonio A.F. Loureiro, and Qiang Wang. Their study was awarded Best Paper at the conference. They said the reference platform consists of a GPS receiver (Maxim MAX2769), a microcontroller (TI MCUMSP430F5338), a WWVB receiver module for time synchronization, and a serial ﬂash chip for storage and glue logic. In addition, the platform has a solar cell, a thin-ﬁlm Micro-Energy cell battery, and a Hi-Jack inspired audio communication port. An 8Mbit ﬂash enables storing up to 1000 GPS sample points. “The goal of the design is to demonstrate the low energy consumption per GPS sample.”