@conference {
	title = {Utility-based Almost Blank Subframe Optimization in Heterogeneous Cellular Networks},
	author = {Sung, Doo-hyun., Baras, John S.},
	year = {2014},
	month = {12/2014},
	abstract = {Heterogeneous cellular networks are expected to provide capacity enhancement and user offloading with cell range expansion. Under this circumstance, downlink cross-tier interference from macro base stations to pico mobile stations especially in the expanded range is a challenging problem. To mitigated this problem, the use of almost blank subframes (ABSs)has been proposed in 3GPP LTE-A systems. The issues are how many ABSs are configured, and how pico base stations schedule their pico mobile stations to configured ABSs. In this paper,we study the optimal number of ABSs along with pico mobile station scheduling in ABSs by formulating a utility maximization problem with constraints of minimum required data rate of picomobile stations in the expanded range. To solve the optimization problem, we first propose an algorithm for each pico base station to schedule pico mobile stations onto ABSs and non-ABSs, in away that if their local utility is maximized for a given number of ABSs, then the optimal number of ABSs is obtained by maximizing the network-wide utility. Through simulations, we demonstrated that the proposed scheme not only can improve the network-wide utility, can also provide fairness among mobile stations.},
	address = {Austin, Texas},
	booktitle = {IEEE Globecom 2014 - Wireless Communication Symposium},
	pages = {pp. 4132-4137}
}
@conference {
	title = {Load Balancing with Almost Blank Subframe Control in Heterogeneous Cellular Networks},
	author = {Sung, Doo-hyun., Baras, John S.},
	year = {2014},
	month = {12/2014},
	abstract = {In heterogeneous cellular networks, the network capacity can be significantly enhanced via user offloading between macro-- and Pico-tier. Due to the strong cross-tier interference from macrocells to picocells in co-channel deployment, the user offloading needs to be jointly optimized with macrocells{\textquoteright} transmit power nulling, i.e., almost blank subframes (ABSs) in 3GPP LTEAsystems. In this paper, we discuss the network-wide utility maximization problem where the cell association and the number of ABSs are jointly optimized. Due to the NP-hardness of the formulated problem, an online heuristic algorithm is proposed where (i) user load is re-distributed based on users{\textquoteright} expected data rate by handover for the current number of ABSs, and (ii)the current number of ABSs is changed (increased or decreased)by estimating the possible users to be offload based on users{\textquoteright} expected data rate by handover and ABS change in a gradient descent manner. Through simulations, we demonstrate that the proposed algorithm not only improves the average data rate of users, but also achieves better fairness among users.},
	address = {Austin, Texas},
	booktitle = {IEEE Globecom 2014 - Wireless Communication Symposium},
	pages = {pp. 4125-4131}
}
