ABSTRACT
Femtocells are overlayed on existing Macrocells to form Macro-Femto heterogeneous network (HetNet), to reduce cost of mounting expensive macrocell nodes, improve cellular network capacity and throughput performance. However, HetNet has a major problem of cross-tier and co-tier interference, which hinders its optimal performance, especially when the network capacity expands. With emergence of 5G technologies, interference would become more consequential. Therefore, curbing the effect of this interference is indispensable to sustain larger and efficient HetNet. In this work power control technique was explored to reduce the impact of interference in both Downlink and  Uplink  scenarios  of 5G non-stand-alone (NSA) architecture of Macro-Femto HetNet. An enhanced active power control (EAPC) technique, was developed by hybridizing extended attenuation factor path loss model, Active Power Control (APC), and Power Control 1 (PC1) techniques. Attenuation factor model was extended by adding floor factor to capture both floor attenuation and wall factor, and used same in computing femtocell path loss. The EAPC technique also made use of a different step power value of 0.5 dB for adjusting it’s transmit power in order to maximize power and reduce interference. The hybridization when compared with APC and PC1 respectively yielded: 65% and 37% higher Home User Equipment (HUE) throughput; 37% and 21% higher Macro User Equipment (MUE) throughput; 41% and 63% higher throughput of femtocell node (Hen-gNB); 69% and 25% higher throughput of macrocell node (en- gNB). EAPC average power consumption compared to APC and PC1 respectively saved: 65% and 40% HUE battery energy; 38% and 42% MUE battery energy; 54% and 22% Hen-gNB energy. EAPC saved 21% en-gNB energy when compared to APC, but was limited by 8% when compared with PC1.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background to the Study
The cellular communication network is a wireless system where users are clustered into cells and served by nodes. The number of mobile users served by macrocell node is increasing every day, with most of the subscribers located at homes and offices (indoor environment). This indoor mobile user has traffic that comprised of 30% voice and 70% data (Priya and Seema, 2017; Aneeqa, et al., 2017; Onu et al., 2018; Dawar et al., 2021). Indoor propagation path loss is characterized by wall penetration loss, floor attenuation factor, and distance between an indoor node and user equipment. In a homogeneous macrocell network, the cost of mounting several macro nodes to meet up with subscriber’s need for high throughput and large coverage is a challenge. This necessitates the deployment of low-power and less expensive nodes to increase the throughput and capacity of the existing macrocell network, at the expense of increase interference.
Interference signals are undesired signals picked by a neighboring receiver, which is a common wireless communication network problem. This interference degrades the performance of the cellular network in terms of drop calls, latency, and poor quality of service; mostly in a partially dedicated channel or co-channel deployment (Priya and Seema 2017). Therefore, there is a need for a thorough study on interference within and between network tiers, in order to develop an efficient interference mitigation technique.
The fifth generation (5G) Ultra-Dense Network (UDN) have a target of increase coverage, throughput, and spectrum efficiency, to accommodate huge subscribers (Agiwal et al., 2016; Asif et al., 2019; Dawar et al., 2021). This can be achieved by deploying more nodes in a given area, using a large number of small nodes (Farah et al., 2016; Mythili and Mahendran, 2017; Achonu et al., 2020). Femtocell node is the smallest cell node that has high data rate, low latency, easy installation, low energy consumption, better coverage, security, and less packet loss. Researchers asserted that the use of this low- power femtocell on an existing macrocell network to form a heterogeneous network (HetNet) will accomplish the target of wider coverage, high efficiency, and enhanced throughput in the cellular network. (Onu et al., 2018; Amandeep et al., 2019; Hassan and Gao, 2019; Haroon et al., 2021). However, the expanding installation of femtocells on the existing macrocell network comes with an interference problem. This interference is attributed to the random installation of femtocell nodes by users, and the contention for the same licensed spectrum by both femtocells and macrocells users.
1.2 Statement of the Research Problem
The high demand for voice, data, and video streaming services by an ever-increasing mobile user’s mostly located in an indoor environment is alarming (Heli et al., 2015; Tuan, et al., 2017). This is more pronounced with the increase in virtual meetings, telemedicine, smart agriculture, smart city, smart homes, and cloud computing. Ericsson’s mobility report, as presented in Sajjad et al. (2018), indicated that in 2021, there will be nine billion mobile broadband subscriptions, out of which seven billion will use mobile data. Their report also pointed out, that smartphone data will increase by 20% and video traffic will increase by 25%. As the demands increase with the advent of 5G Ultra-Dense Network, the cell coverage, network capacity and throughput of homogeneous network will reduce, resulting into poor indoor network services.
According to literatures, the overlay of femtocell on existing macrocell netwok is said to be one of the promising technique that would provide the needed solution to the poor indoor network service, increased network coverage and capacity (Heli et al., 2015; Xu and Qui, 2018). However, femtocell node being a plug and play node, that used license frequency band, and is installed by subscribers without taking into cognizance its cell coverage or other nearby cells, have high chances of cell overlap, that causes an increase in interference. This interference is the main technical problem attributed with Macro-Femto HetNet (Al-omari et al., 2016; Farah et al., 2016; Feng, et al., 2018; Mohammad et al., 2019).
Researchers have postulated different power control techniques for curbing the interference problem with successes, even though there is still room for improvement. This research seeks to study interference in Macro-Femto HetNet and developed an enhanced power control technique from existing power control techniques; to contribute in solving the interference problem in Macro-Femto HetNet.
1.3 Aim and Objectives of the Research
The research aims at developing an Enhanced Active Power Control (EAPC) technique for interference mitigation in 5G Non-Stand-Alone (NSA) architecture of Macro-Femto cellular communication networks. To achieve this, the following objectives were set:
i. Hybridization of attenuation factor model, active power control technique and power control 1 techniques to develop an enhanced active power control (EAPC) technique.
ii. Simulate EAPC technique in Macro-Femto cellular communication network using MATLAB.
iii. To evaluate the performance of the EAPC technique and compare it with that of existing power control techniques, in terms of throughput and power consumption.
1.4 Scope of the Study
The research work centred on developing an enhanced active power control technique, for mitigating co-tier and cross-tier interference in 5G NSA of Macro-Femto HetNet. The research system architecture, parameters, and assumptions would guide the MATLAB simulation of the Macro-Femto HetNet. The performance of the EAPC technique would be compared with that of PC1 and APC technique in terms of throughput and transmit power consumption.
1.5 Justification for the Study
Interference is a major problem in wireless communication networks which reduced network throughput and increase drop calls.
The work of Hassan and Gao (2019) proposed an active power control technique for mitigating interference in Macro-Femto communication networks, which reduced interference in the network, gave high throughput and low node power consumption when benchmarked; but more need to be done to improve on the existing technique. Their network scenario considered static user equipment (UE) and cross-tier interference only; it did not considered co-tier interference and attenuation due to floor. Therefore there is a need to enhanced active power control technique, consider co-tier and cross-tier interference, attenuation due to floor factor, and mobile UEs to capture a realistic network scenario, further reduce power consumption and increase network throughput in 5G Macro-Femto communication networks.
1.6 Thesis Outline
The remaining part of the thesis is organized as follows. Chapter two review 5G non- stand-alone architecture, femtocell network, femtocell access mode, Macro-Femto HetNet, network interference in Macro-Femto HetNet, mathematical models for Macro- Femto HetNet, and also related works of literature on interference mitigation using power control technique. Chapter three presents the research system model, and methodology. Chapter four presents and discusses the MATLAB simulation results in sections. And chapter five states the conclusion and recommendations of the research.
This material content is developed to serve as a GUIDE for students to conduct academic research
DEVELOPMENT OF AN ENHANCED ACTIVE POWER CONTROL TECHNIQUE FOR INTERFERENCE MITIGATION IN MACRO- FEMTO CELLULAR NETWORKS
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