Degree Type

Dissertation

Date of Award

2018

Degree Name

Doctor of Philosophy

Department

Electrical and Computer Engineering

Major

Electrical Engineering; Computer Engineering

First Advisor

Ahmed E. Kamal

Abstract

Prospective demands of next-generation wireless networks are ambitious and will require cellular networks to support 1000 times higher data rates and 10 times lower round-trip latency. While this data deluge is a natural outcome of the increasing number of mobile devices with data hungry applications and the internet of things (IoT), the low latency demand is required by the future interactive applications such as "tactile internet", virtual and enhanced reality, and online internet gaming, etc.

Self-Organizing Network (SON) is defined as the network that has the capability to dynamically adapt changes in the network in order to optimize its performance. The need for SONs arises from the fact that in future networks, e.g., 5G networks, the number of nodes will be increasing at a rapid rate. Moreover, it is also because of the introduction of a high degree of heterogeneity and complexity, that such SONs could save significant operational expenditure. SON defines three areas: self-configuration (plug and play network elements), self-optimization (automatically optimize network parameters), and self-healing (automatically detect and mitigate failures).

Self-healing is the execution of actions that keep the network operational and/or prevent disruptive problems from arising. It is done in two steps: cell outage detection (COD) and cell outage compensation (COC). COD detects and classifies failures, while minimizing detection time. COC executes actions to mitigate the effect of the failure. Detecting cell outage in 3G and 4G was doable, but it could take up to several hours, thus resulting in salient degradation in network performance. Hence, automatic detection and compensation of failures in 5G networks is mandatory.

The motivation behind this thesis is to meet the need for increasing reliability in wireless communications networks by mitigating, reducing, or alleviating the effect of the network equipment failures. To achieve these goals, outage compensation models for wireless cellular networks are proposed and analyzed. We are presenting different ways of mitigating the failures that occur in network equipment; 1) the backhaul/fronthaul failures either in traditional or cloud-Radio Access Networks 2) the battery starved users in the network 3) Failures of BSs and using UAVs/Drones in mitigating these failures.

Firstly, a solution for the backhaul/fronthaul failures based on using a new Self-healing Radio (SHR) along with using the concept of Cognitive Radio (CR) and Software Define Networking (SDN) is proposed to mitigate the effect of backhaul/fronthaul failures in 4G/5G networks. We present a novel cell outage compensation approach using new Self-Healing Radios (SHRs) added to each cell site in the 5G network. These SHRs operate only in case of fronthaul/backhaul failure of any cell site in the network. A new software defined controller is introduced to handle the self-healing procedures. We also introduce a high level simulation study that is carried out to assess the proposed approach. The simulation results confirm the advantages of the proposed approach in terms of the degree of recovery from failures.

Secondly, we propose a promising solution for battery starved users in cellular networks. Radio Frequency (RF) Energy Harvesting (EH) holds a promising future for energizing low power mobile devices in next generation wireless networks. Harvesting from a dedicated RF energy source acquires much more energy than simply harvesting from ambient RF sources. A novel Self-healing of Users equipment by Rf Energy transfer (SURE) scheme is introduced between the network operator and battery starved users to heal and extend their battery life time by sending dedicated energy from different sources in order to be aggregated and harvested by starved users. This approach introduces the concept of Energy as a Service (EaaS) where the network operator delivers energy to battery starved users in next generation networks. A mixed integer non-linear optimization problem is formulated and solved efficiently. Simulation results prove that sufficient amounts of energy can be delivered to starved users while minimizing their uplink power requirements and guaranteeing a minimum uplink data rate.

Lastly, three frameworks of cell outage compensation frameworks for 4G/5G network supported by dynamic Drone Base-stations (DBSs) is proposed. Within the first framework, the outage compensation is done with the assistance of sky BSs and Ground BSs (GBSs). An optimization problem is formulated to jointly minimize the energy of the Drone BSs (DBSs) and GBSs involved in the healing process which accordingly will minimize the number of DBSs and determine their optimal 2D positions. Simulation results show that the proposed hybrid approach outperforms the conventional COC approach. Moreover, all users receive the minimum quality of service in addition to minimizing the UAVs’ consumed energy.

The second framework addresses the way of failure mitigation based on the type and duration of the failure. We propose a framework that uses DBSs or helikites to mitigate GBS failures. Our proposed short-term and long-term cell outage compensation framework aims to mitigate the effect of the failure of any GBS in 5G networks. Within our framework, outage compensation is done with the assistance of sky BSs. An optimization problem is formulated to jointly minimize communication power of the UAVs and maximize the minimum rates of the Users' Equipment (UEs) affected by the failure. Also, the optimal placement of the UAVs is determined. Simulation results show that the proposed framework guarantees the minimum QoS for each UE in addition to minimizing the UAVs' consumed energy.

The third and last framework utilizes a grid of DBSs to provide cellular coverage to disaster-struck regions where the terrestrial infrastructure is totally damaged due to earthquakes, floods, etc. We propose solutions for the most challenging issues facing drone networks which are limited battery energy and limited backhauling. Our proposed solution is based mainly on using three types of drones; tethered backhaul drone (providing high capacity backhauling), untethered powering drone (providing on the fly battery charging) and untethered communication drone (providing cellular connectivity). The simulation results show that we can provide unlimited cellular service to the disaster-affected region under certain conditions with a guaranteed minimum rate for each user.

Copyright Owner

Mohamed Youssef Selim

Language

en

File Format

application/pdf

File Size

194 pages

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