Computer Communications 155 (2020) 48–57 Contents lists available at ScienceDirect Computer Communications journal homepage: www.elsevier.com/locate/comcom SIR analysis for non-uniform HetNets with joint decoupled association and interference management Ziaul Haq Abbas a , Muhammad Sajid Haroon b,∗ , Ghulam Abbas c , Fazal Muhammad d a Faculty of Electrical Engineering, GIK Institute of Engineering Sciences and Technology, Topi 23640, Pakistan b Telecommunications and Networking (TeleCoN) Research Lab, GIK Institute of Engineering Sciences and Technology, Topi 23640, Pakistan c Faculty of Computer Sciences and Engineering, GIK Institute of Engineering Sciences and Technology, Topi 23640, Pakistan d City University of Science and Information Technology, Peshawar, Pakistan ARTICLE INFO Keywords: Coverage probability Fractional power control Heterogeneous cellular networks Poisson point process Poisson hole process Reverse frequency allocation ABSTRACT In heterogeneous cellular networks (HetNets), fractional power control (FPC) is used in uplink (UL) transmis- sion to improve signal-to-interference ratio (SIR) by compensating path loss. However, employing FPC results in a significant co-channel UL interference (UL-I) as a result of increased users’ transmit power. Moreover, macro base station (MBS) edge users make the situation exacerbate by transmitting with even higher power to compensate path loss and, thus, render FPC highly unsuitable in HetNets. In this paper, we aim to decrease severe UL-I and, thus, leverage FPC in HetNets. Hence, we propose non-uniform HetNets (NUHs) where small base stations (SBSs)’ deployment near MBS is avoided by using Poisson hole process (PHP). NUHs provide: (i) improved coverage due to coverage-oriented SBS distribution, and (ii) lower MBS-interference (MBS-I) as the SBSs are only deployed in coverage edge area of MBS. In conjunction with NUH, we employ decoupled association (DeCA), in contrast to coupled association (CA), to improve UL SIR. NUH along with DeCA provide lower UL-I and MBS-I due to reduced interference and improved UL SIR. Additionally, to efficiently utilize the radio resources, we employ reverse frequency allocation (RFA) to mitigate inter-cells-interference (ICI). We compare CA with DeCA in different network scenarios. Results indicate that the employment of DeCA leads to improved UL coverage, as compared with CA, due to effective mitigation of UL-I, MBS-I, and ICI. Moreover, the results indicate significant improvement in UL coverage for the SIR threshold values greater than 0 dB. Furthermore, the results show that a higher value of FPC compensation factor improves the coverage performance. 1. Introduction 1.1. Motivation In heterogeneous cellular networks (HetNets), coverage probability, spectrum efficiency, and throughput are significantly increased by de- ploying ultra-dense small base stations (SBSs) in the coverage area of macro base station (MBS), unlike homogeneous networks [1,2]. The employment of orthogonal frequency division multiple access (OFDMA) ensures negligible intra-cell interference in HetNets. However, MBS- interference (MBS-I) and inter-cell interference (ICI) significantly affect uplink (UL) coverage in HetNets [3]. In HetNets, fractional power control (FPC) is used for UL transmis- sion to compensate shadowing and path loss effects [4]. Path loss is the function of distance between base station (BS) and user, whereas shadowing is caused by obstacles between the user and BS that absorb power. Both shadowing and path loss lead to variations in received ∗ Corresponding author. E-mail addresses: ziaul.h.abbas@giki.edu.pk (Z.H. Abbas), sajid.haroon@giki.edu.pk (M.S. Haroon), abbasg@giki.edu.pk (G. Abbas), fazal.muhammad@cusit.edu.pk (F. Muhammad). signal power over distance and are referred to as large-scale fading. FPC creates severe co-channel UL interference (UL-I) because: (i) all other users with variable UL transmit power (UTP) act as interferers for the reference user (), and (ii) FPC leads to high UTP by edge users and, hence, higher interference [3,4]. In uniform HetNets (UHs), users, MBSs and SBSs are distributed uniformly via independent homogeneous Poisson point processes (IH- PPPs). SBSs located near MBS receive severe MBS-I and, thus, reduce network performance [5]. In non-uniform HetNets (NUHs), MBSs and users follow IHPPP while SBSs are deployed only in MBS edge coverage area using Poisson hole process (PHP). NUH leads to lower MBS-I and, consequently, improves network coverage performance [6,7]. Furthermore, in HetNets, coupled association (CA) strategy is fol- lowed where a user is served by a BS both in UL and downlink (DL) while using maximum received power (MRP) averaged over a longer duration of time [8]. CA is commonly followed when the distance https://doi.org/10.1016/j.comcom.2020.03.015 Received 22 August 2019; Received in revised form 17 February 2020; Accepted 10 March 2020 Available online 14 March 2020 0140-3664/© 2020 Elsevier B.V. All rights reserved.