@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 = {<p>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.</p>
},
	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}
}
@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 = {<p>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.</p>
},
	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}
}
