@conference {
	title = {Improving Smartphone Battery Life Utilizing Device-to-device Cooperative Relays Underlaying LTE Networks},
	author = {Ta, Tuan., Baras, John S., Zhu, Chenxi.},
	year = {2014},
	month = {06/2014},
	abstract = {The utility of smartphones has been limited to a great extent by their short battery life. In this work, we propose a new approach to prolonging smartphone battery life. We introduce the notions of valueless and valued battery, as being the available battery when the user does or does not have access to a power source, respectively. We propose a cooperative system where users with high battery level help carry the traffic of users with low battery level. Our scheme helps increase the amount of valued battery in the network, thus it reduces the chance of users running out of battery early. Our system can be realized in the form of a proximity service (ProSe) which utilizes a device-to-device (D2D) communication architecture underlaying LTE. We show through simulations that our system reduces the probability of cellular users running out of battery before their target usage time (probability of outage). Our simulator source code is made available to the public.},
	address = {Sydney, Australia},
	booktitle = {Proceedings of the IEEE ICC 2014 - Wireless Communications Symposium,},
	pages = {pp. 5264-5268}
}
@conference {
	title = {Coordinated Scheduling and Power Control for Downlink Cross-tier Interference Mitigation in Heterogeneous Cellular Networks},
	author = {Sung, Doo-hyun., Baras, John S., Zhu, Chenxi.},
	year = {2013},
	month = {12/2013},
	abstract = {In heterogeneous cellular networks, the deployment~of low-powered picocells provides user offloading and capacity~enhancement. The expansion of a picocell{\textquoteright}s coverage by adding~a positive bias for cell association can maximize these effects.~Under this circumstance, downlink cross-tier interference from~a macro base station to pico mobile stations in the expanded~picocell range deteriorates those pico mobile stations{\textquoteright} performance~significantly. In this paper, a coordinated scheduling~and power control algorithm is proposed, whereby the macro~base station reduces its transmission power for those victim~pico mobile stations in the expanded picocell range only on a~set of resource blocks to minimize performance degradation at~the macro base station. First, the transmission power level is~calculated based on the mobile stations{\textquoteright} channel condition and
QoS requirements. Then, a set of resource blocks is determined~by solving a binary integer programming to minimize the sum~of transmission power reduction subject to victim pico mobile~stations{\textquoteright} QoS constraints. To reduce computational complexity,~we utilize a heuristic algorithm, i.e., max-min greedy method,~to solve the problem. Through system level simulations, we~show that average and 5\%-ile throughputs of victim pico mobile~stations are significantly improved.},
	address = {Atlanta, Georgia},
	booktitle = {IEEE Globecom 2013},
	pages = {pp. 3914-3918}
}
