In this work, we examine the IO characteristics of two smartphone platforms: Android and Tizen. We compare how the two platforms differ in using the filesystem, using the database, and accessing the storage. We collected the IOs from select seven different apps that are commonly available on both platforms. By analyzing the collected the IOs on both platforms, a dominant fraction of writes are 4 KB synchronous. On Android and Tizen, respectively, 65% and 45% of all write IO counts 4 KB; 47% and 75% of all writes accesses are SQLite related files such as database, rollback journal, WAL (Write Ahead Log), and etc.; 81% and 86% of all IOs are random accesses; and 90% and 52% of all writes counts are synchronous IO mode. According to our IO analysis, Android IO stack is more sophisticated then Tizen one: (i) disables a time updates, (ii) adopts journal asynchronous commit, and (iii) adopts fdatasync( ) in SQLite.

As the number of mobile phone users are increasing, the importance of understanding its I/O behavior is also increasing. In this paper, after analyzing the basic I/O behavior of fourteen popular smartphone workloads, we chose three applications for deeper analysis. The three applications, Contacts, Web Browser, and Camera, are not only the heaviest I/O generator on Android and Tizen, but also the ones with the highest End-to-End Write Amplification, which is the ratio between the actual volume of data written to the storage and the volume of data user or application intended to create; Contacts Manager, for example, has 1.7 × 105and 3.9 × 104on Android and Tizen, respectively. We observed that although background applications, such as spell checker and auto-input-completion are not essential part of using aforementioned applications, but they the critical root of generating heavy I/O overhead on Android devices. We also find that applications keep records of numerous auxiliary information on many different databases and a lot of index tables to enhance the user experience; but some of them are merely a duplicate of same information. The fact that each insert in a table creates ripples of side-effect on index tables and on other related tables, the I/Os are easily amplified and causes heavy overhead on the storage system.

A self-contained direction sensing radio frequency identification (RFID) reader is developed employing a dual-directional antenna for automated target acquisition and docking of a mobile robot in indoor environments. The dual-directional antenna estimates the direction of arrival (DOA) of signals from a transponder by using the ratio of the received signal strengths between two adjacent antennas. This enables the robot to continuously monitor the changes in transponder directions and ensures reliable docking guidance to the target transponder. One of the technical challenges associated with this RFID direction finding is to sustain the accuracy of the estimated DOA that varies according to environmental conditions. It is often the case that the robot loses its way to the target in a cluttered environment. To cope with this problem, the direction correction algorithm is proposed to triangulate the location of the transponder with the most recent three DOA estimates. Theoretical simulation results verify the reliability of the proposed algorithm that quantifies the potential error in the DOA estimation. Using the algorithm, we validate mobile robot docking to an RFID transponder in an office environment occupied by obstacles.

Automated target acquisition and docking is key to enabling various applications of autonomous mobile robots in indoor environments. For the purpose, many researches have been devoted to the development of location sensing techniques employing the latest in RFID or GPS. However, it has not yet become possible to attain high accuracy in those techniques, particularly in cluttered or dynamically changing environments. In this paper, we propose a novel location sensing RFID reader equipped with a dual directional antenna that communicates with controllable RF transponders. The dual directional antenna estimates the direction of arrival (DOA) of signals from various transponders by using the ratio of the received strength between two antennas. This enables the robot to continuously monitor the changes in the ratio and find its way to the target transponder. To verify the validity of the proposed system in real environments populated with unknown obstacles, we perform detailed experiments using simulations and hardware implementations. Specifically, the target acquisition and docking guidance are demonstrated in a multiple transponder environment under various circumstances.