Many emerging mobile services leverage sensors available on N900 to acquire information regarding the physical world. While the sensors themselves can be quite low-power, sensor use by N900 has proven to be a key bottleneck in the device energy efficiency due to a centralized and ad hoc system support.
We have design and developed *Reflex*, a framework that manages sensor use with programming and operating abstractions called channels for sensor data processing. Reflex provides three mechanisms. 1) It uses a runtime called channel manager to execute channels on behalf of applications and therefore eliminates frequent process context switches. 2) It allows multiple applications share a channel and therefore minimizes redundancy in sensor data processing. 3) It can delegate channel execution to programmable sensors and therefore relieves the system from high-duty cycle activities.
To demonstrate the idea of Reflex, we also build a programmable sensor prototype called *Orbit*. Orbit is a very power-efficient sensor which equips with one MSP430 processor, two accelerometers, and Bluetooth module (optional). Orbit works under the dictation of Reflex, and executes channels on behalf of N900.
Our measurement of Reflex prototypes based on N810 and N900 shows that Reflex can extend the battery life by up to three times. Therefore, Reflex has made a large amount of sensor applications that were power-hungry now become possible and practical to everyday use.
Based on Reflex, we propose a personal physical activity monitor application. The Orbit sensor collects user's acceleration data and recognizes user's activity in one's daily life. Such activity information can be widely shared among applications on N900, like health diagnosis or social network applications. It is worth noting that only through the magic of Reflex, the activity monitor becomes possible: with the current N900 sensor framework it drains the battery in half a day, while with Reflex it can work for up to 3 days.
Here is a guide on how to develop channels for Reflex. [PDF]
We are releasing part of Reflex Code under GPL.
svn co https://ricereflex.svn.sourceforge.net/svnroot/ricereflex/trunk Reflex
Rice gradute students Felix and Ahmad, working with Prof. Lin Zhong. We are part of Rice ECG Group.