On placement and efficient resource allocation of LAA/LTE-U base stations in HetNet

Abstract

LTE operation in unlicensed spectrum is considered as a promising solution to meet the increase in user data demand. Licensed Assisted Access (LAA), and duty cycled LTE-U are two options for LTE to operate in the unlicensed band for fair sharing of unlicensed spectrum with IEEE 802.11 (Wi-Fi). Due to restriction on the transmission power in the unlicensed band, LAA/LTE-U Base Stations (BSs) will get deployed mostly inside residential and office buildings to provide high data rates for indoor User Equipments (UEs). In an indoor scenario, walls and other obstacles in the communication path along with co-tier and cross-tier interferences decrease the Signal-to-Interference plus Noise Ratio (SINR) significantly which results in throughput decrease. Hence, an optimal placement of LAA BSs is essential. As the available bandwidth in the unlicensed spectrum is more compared to the licensed spectrum, an efficient resource allocation is also necessary for ensuring minimum throughput for the indoor UEs. In this paper, our goal is to find the optimal number of LAA/LTE-U BSs with minimum throughput guarantee inside the building using licensed and unlicensed bands. To do this, we formulate an optimization model (MinLAA) for LAA BSs placement which is Mixed Integer Non-Linear Programming (MINLP) problem. So, we propose a heuristic algorithm to find the minimum number of LAA/LTE-U BSs such that all the users inside the building get minimum guaranteed throughput