UC Irvine

ABSTRACT OF THE THESIS

Traffic offloading in HetNet using power biasing considering different path loss exponent

By

Jyotica Yadav

Master of Science in Electrical Engineering

University of California, Irvine, 2019

Professor Ender Ayanoglu, Chair

With the advent of new cellular technology, the number of users is expected to grow at a drastic rate that comes with the cost of an increase in data traffic. Therefore, to provide enough capacity for all the users, node density must be increased. One way to achieve that is through cell splitting but that would lead to higher chances of intercell interference along with incurring higher costs of installing high power macro nodes. Another way to attain a higher network capacity is to overlay a network of small low power nodes over an existing network thereby creating a heterogeneous network, i.e., HetNet [1]. In HetNet, the user is made available with more than one type of base station differing in the transmit power level and physical size. But, even with multiple options at hand, the user terminal always tends to associate itself to the macro base station i.e., the station with the highest transmit power. The reason is, that associativity is based on the received signal strength values i.e., RSS values, therefore, irrespective of the distance between the user and the station, the user will always have a preference towards macro station over low tier stations. Because of the above-mentioned claim, the overall reason behind shifting towards low tier station nullifies, therefore, it is essential to offload the data traffic from the macro tier. Some of the techniques to offload data traffic are offloading via power control, offloading via femtocell deployment and offloading via biasing, out of which, the latter is of concern to the thesis [2]. The research so far focuses on the stationary user and its connectivity to a base station. With user velocity in the picture, comes the concept of handover and its associated delays. Handover delays in dense networks lower the effect of an overall increase in network capacity as it includes the transmission of control signals rather than effective data transmission thereby raising the overhead over the network. Few handover skipping schemes have been proposed to avoid frequent handovers whose underlying assumption is same path loss exponents for all the tiers and unbiased power levels [3]. In this thesis, the effect of different path loss exponents and biased power levels has been investigated and the effect on coverage probability has been studied. In the end, the simulation results obtained are compared with the work done by other researchers so far.