@article {15, title = {Cuffless Differential Blood Pressure Estimation Using Smart Phones}, journal = {IEEE Transactions on Biomedical Engineering}, volume = {60}, year = {2013}, pages = {1080 - 1089}, abstract = {

Smart phones today have become increasingly popular with the general public for their diverse functionalities such as navigation, social networking, and multimedia facilities. These phones are equipped with high-end processors, high-resolution cameras, and built-in sensors such as accelerometer, orientation-sensor, and light-sensor. According to comScore survey, 26.2\% of U.S. adults use smart phones in their daily lives. Motivated by this statistic and the diverse capability of smart phones, we focus on utilizing them for biomedical applications. We present a new application of the smart phone with its built-in camera and microphone replacing the traditional stethoscope and cuff-based measurement technique, to quantify vital signs such as heart rate and blood pressure. We propose two differential blood pressure estimating techniques using the heartbeat and pulse data. The first method uses two smart phones whereas the second method replaces one of the phones with a customized external microphone. We estimate the systolic and diastolic pressure in the two techniques by computing the pulse pressure and the stroke volume from the data recorded. By comparing the estimated blood pressure values with those measured using a commercial blood pressure meter, we obtained encouraging results of 95{\textendash}100\% accuracy.

}, keywords = {Blood pressure, cuffless, Estimation, finger pulse, Heart, Microphones, mobile camera, Mobile communication, mobile phone, Synchronization, Valves, vascular transit time}, doi = {10.1109/TBME.2012.2211078}, author = {Chandrasekaran, Vikram and Ram Dantu and Jonnada, Srikanth and Thiyagaraja, Shanti and Subbu, Kalyan} } @article {25, title = {LocateMe: Magnetic-fields-based Indoor Localization Using Smartphones}, journal = {ACM Trans. Intell. Syst. Technol.}, volume = {4}, year = {2013}, pages = {73:1{\textendash}73:27}, abstract = {

Fine-grained localization is extremely important to accurately locate a user indoors. Although innovative solutions have already been proposed, there is no solution that is universally accepted, easily implemented, user centric, and, most importantly, works in the absence of GSM coverage or WiFi availability. The advent of sensor rich smartphones has paved a way to develop a solution that can cater to these requirements.

By employing a smartphone{\textquoteright}s built-in magnetic field sensor, magnetic signatures were collected inside buildings. These signatures displayed a uniqueness in their patterns due to the presence of different kinds of pillars, doors, elevators, etc., that consist of ferromagnetic materials like steel or iron. We theoretically analyze the cause of this uniqueness and then present an indoor localization solution by classifying signatures based on their patterns. However, to account for user walking speed variations so as to provide an application usable to a variety of users, we follow a dynamic time-warping-based approach that is known to work on similar signals irrespective of their variations in the time axis.

Our approach resulted in localization distances of approximately 2m--6m with accuracies between 80--100\% implying that it is sufficient to walk short distances across hallways to be located by the smartphone. The implementation of the application on different smartphones yielded response times of less than five secs, thereby validating the feasibility of our approach and making it a viable solution.

}, keywords = {Indoor localization, Magnetic fields, smartphones, ubiquitous}, issn = {2157-6904}, doi = {10.1145/2508037.2508054}, url = {http://doi.acm.org/10.1145/2508037.2508054}, author = {Subbu, Kalyan and Gozick, Brandon and Ram Dantu} } @article {82, title = {Socio-technical Aspects of Remote Media Control for a NG9-1-1 System}, journal = {Multimedia Tools Appl.}, volume = {62}, year = {2013}, pages = {733{\textendash}759}, abstract = {

9-1-1 emergency calls mostly involve distress situations that cause people to panic while trying to answer questions or follow instructions given by a dispatcher. To obtain precious information with the least user intervention and reduced stress on the user, there is a need for the dispatcher to have a better control and understanding of the condition or situation at the other end. The increasing growth of smartphones embedded with camera, speaker phone, GPS, microphone and various other sensors, extends their usage from merely making calls to life saving gadgets during critical situations. By integrating these sensor rich smartphones and the rapidly growing VoIP technology, we propose a VoIP based Next Generation 9-1-1 (NG9-1-1) system for remote media control. Specifically, we use Session Initiation Protocol (SIP) in the implementation of the system using a mobile and a PC client. The proposed system on the mobile client accounted for less than 25\% of CPU utilization even with video transmission. The average network utilization was about 10 and 72 kbps for audio and video, respectively. With these encouraging results, we believe the proposed remote media control system will facilitate information acquisition and decision making in emergency situations.

}, keywords = {Image transmission, Media control, NG9-1-1, PSAP, Remote, SIP, Voice quality, VoIP}, issn = {1380-7501}, doi = {10.1007/s11042-011-0875-1}, url = {http://dx.doi.org/10.1007/s11042-011-0875-1}, author = {Chandrasekaran, Vikram and Ram Dantu and Subbu, Kalyan} } @conference {21, title = {Evaluation of gyroscope-embedded mobile phones}, booktitle = {Systems, Man, and Cybernetics (SMC), 2011 IEEE International Conference on}, year = {2011}, address = {Anchorage, AK}, abstract = {

Many mobile phone applications such as pedometers and navigation systems rely on orientation sensors that most smartphones are now equipped with. Unfortunately, these sensors rely on measured accelerometer and magnetic field data to determine the orientation. Thus, accelerations upon the phone which arise from everyday use alter orientation information. Similarly, external magnetic interferences from indoor/urban settings affect the heading calculation, resulting in inaccurate directional information. The inability to determine the orientation during everyday use inhibits many potential mobile applications development. In this work, we exploit the newly built-in gyroscope in the Nexus S smartphone to address the interference problems associated with the orientation sensor. We first perform drift error analysis and apply this to gyroscope calculations. We test simple as well as complex rotations seen in walking applications. We lastly test the gyroscope{\textquoteright}s resistance to described interferences. Experiments show angular calculations with percent error no larger than 6\% from actual rotated values. Further, we are able to determine the phone{\textquoteright}s orientation at any time, in magnetically-interfered areas, with the phone accelerating. With this accurate information we can virtually orient the phone to better use mobile-acquired data. This shows that the presence of a gyroscope in smartphones will certainly aid in numerous applications.

}, keywords = {Acceleration, Accelerometer, Accelerometers, Angular rotation, Gyroscope, Gyroscopes, Magnetic sensors, Mobile communication, Mobile handsets, mobile phone, Orientation sensor}, isbn = {978-1-4577-0652-3}, doi = {10.1109/ICSMC.2011.6083905}, author = {Barthold, Christopher and Subbu, Kalyan and Ram Dantu} } @conference {36, title = {Indoor localization through dynamic time warping}, booktitle = {2011 IEEE International Conference on Systems, Man, and Cybernetics}, year = {2011}, month = {10/2011}, address = {Anchorage, AK}, abstract = {

Identifying and locating oneself in different hallways of high rise buildings forms the classic indoor localization problem. GPS does not work indoors and WiFi may not be omnipresent. This paper presents a novel approach to ambient magnetic fields based indoor localization. We present a system that classifies magnetic signatures using dynamic time warping. Specifically, by aligning similar magnetic signatures that differ in magnitude or time, we classify the signatures and infer the location irrepective of the person and his/her mode of commuting. A Nexus One smartphone was employed, utilizing its builtin magnetic field sensor to create a user friendly localization application solely on the phone. By using a variety of subjects including sighted, blindfolded and people using wheelchairs to handle the human speed variation problem, we evaluated the system across 26 and 15 hallways of two different buildings and obtained accuracies of 92.6\%, and 91.1\% respectively. With these encouraging results, we believe our proposed solution is user independent and caters to a wide range of hallways.

}, keywords = {Accuracy, Buildings, Databases, Human, Humans, Legged locomotion, Localization, Magnetometers, mobile phones, sensors, Wheelchairs}, doi = {10.1109/ICSMC.2011.6083906}, author = {Subbu, Kalyan and Gozick, Brandon and Ram Dantu} } @article {9, title = {Magnetic Maps for Indoor Navigation}, journal = {IEEE Transactions on Instrumentation and Measurement}, volume = {60}, year = {2011}, pages = {3883 - 3891}, abstract = {

Magnetic field fluctuations and anomalies inside buildings tend to have a great effect on the compass, which is one of the simplest navigation devices. Alternative navigation requires landmark identification, so those landmarks can be used as guideposts in assisting individuals. By employing a mobile phone with built\_in magnetometer, an extensive data set of 2000 measurements was collected. Using these fields, we identify landmarks and guideposts and create magnetic maps for multiple corridors of a floor in a building. Different phones are used at different sensitivity rates, which effectively portray similar results. Magnetic signatures are used for identifying locations and rooms and are independent of the person, the phone, and the sensitivity of the sensor being used. Magnetic field behavior is demonstrated and compared with theoretical distributions of these fields. The developed magnetic maps can complement existing visual maps for location tracking and navigation of autonomous robots indoors. These maps are particularly useful during limited visual feedback in poor lighting conditions. Moreover, building designers could include this landmark and guidepost information when developing the architecture of a building, which could in turn help people or robots navigate during disasters and emergency evacuations.

}, keywords = {Buildings, Magnetic field measurement, Magnetic field measurements, Magnetic fields, Magnetometers, Mobile handsets, mobile phones, Navigation, sensors, Uncertainty}, doi = {10.1109/TIM.2011.2147690}, author = {Gozick, Brandon and Subbu, Kalyan and Ram Dantu and Maeshiro, Tomyo} } @conference {69, title = {iKnow Where You Are}, booktitle = {Proceedings of the 2009 International Conference on Computational Science and Engineering - Volume 04}, year = {2009}, publisher = {IEEE Computer Society}, organization = {IEEE Computer Society}, address = {Washington, DC, USA}, isbn = {978-0-7695-3823-5}, doi = {10.1109/CSE.2009.55}, url = {http://dx.doi.org/10.1109/CSE.2009.55}, author = {Subbu, Kalyan and Xu, Ning and Ram Dantu} }