8 research outputs found
Planning for Small Cells in a Cellular Network
In this thesis, we analyze the effect of deploying small cells on the performance of a
network comprising several macro cells. We identify potential locations for low-power base-stations based on the coverage patterns of the macro cells and propose three schemes for placing the small cells. We show that by judiciously installing just two small cells for every macro base-station at these locations and allocating separate resources to all the small cells on a global level, we can increase the performance of the network significantly (~ 45%). An added benefit of our schemes is that we can switch o the macro base-stations at night (when the number of active users is low) and significantly reduce their operation cost.4 month
Interference Management Based on RT/nRT Traffic Classification for FFR-Aided Small Cell/Macrocell Heterogeneous Networks
Cellular networks are constantly lagging in terms of the bandwidth needed to
support the growing high data rate demands. The system needs to efficiently
allocate its frequency spectrum such that the spectrum utilization can be
maximized while ensuring the quality of service (QoS) level. Owing to the
coexistence of different types of traffic (e.g., real-time (RT) and
non-real-time (nRT)) and different types of networks (e.g., small cell and
macrocell), ensuring the QoS level for different types of users becomes a
challenging issue in wireless networks. Fractional frequency reuse (FFR) is an
effective approach for increasing spectrum utilization and reducing
interference effects in orthogonal frequency division multiple access networks.
In this paper, we propose a new FFR scheme in which bandwidth allocation is
based on RT/nRT traffic classification. We consider the coexistence of small
cells and macrocells. After applying FFR technique in macrocells, the remaining
frequency bands are efficiently allocated among the small cells overlaid by a
macrocell. In our proposed scheme, total frequency-band allocations for
different macrocells are decided on the basis of the traffic intensity. The
transmitted power levels for different frequency bands are controlled based on
the level of interference from a nearby frequency band. Frequency bands with a
lower level of interference are assigned to the RT traffic to ensure a higher
QoS level for the RT traffic. RT traffic calls in macrocell networks are also
given a higher priority compared with nRT traffic calls to ensure the low
call-blocking rate. Performance analyses show significant improvement under the
proposed scheme compared with conventional FFR schemes
Spectrum- and Energy-Efficient Radio Resource Allocation for Wireless Communications
Wireless communications has been evolved significantly over the last decade. During this period, higher quality of service (QoS) requirements have been proposed to support various services. In addition, due to the increasing number of wireless devices and transmission, the energy consumption of the wireless networks becomes a burden. Therefore, the energy efficiency is considered as important as spectrum efficiency for future wireless communications networks, and spectrum and energy efficiency have become essential research topics in wireless communications. Moreover, due to the exploding of number mobile devices, the limited radio resources have become more and more scarce. With large numbers of users and various QoS requirements, a lot of wireless communications networks and techniques have emerged and how to effectively manage the limited radio resources become much more important.
In this dissertation, we focus our research on spectrum- and energy-efficient resource allocation schemes in wireless communication networks. Recently, heterogeneous networks (HetNets) have been proposed and studied to improve the spectrum efficiency. In a two-tier heterogeneous network, small base stations reuse the same spectrum with macro base stations in order to support more transmission over the limited frequency bands. We design a cascaded precoding scheme considering both interference cancellation and power allocation for the two-tier heterogeneous network. Besides heterogeneous networks, as the fast development of intelligent transportation, we study the spectrum- and energy-efficient resource allocation in vehicular communication networks. The intelligent transportation and vehicular communications both have drawn much attention and are faced special wireless environment, which includes Doppler effects and severe uncertainties in channel estimation. A novel designed spectrum efficiency scheme is studied and verified. With consideration of energy efficiency, the device-to-device (D2D) enabled wireless network is an effective network structure to increase the usage of spectrum. From a device\u27s perspective, we design an energy-efficient resource allocation scheme in D2D communication networks. To improve the energy efficiency of wireless communication networks, energy harvesting technique is a powerful way. Recently, the simultaneous wireless information and power transfer (SWIPT) has been proposed as a promising energy harvesting method for wireless communication networks, based on which we derive an energy-efficient resource allocation scheme for SWIPT cooperative networks, which considers both the power and relay allocation.
In addition to the schemes derivation for spectrum- and energy-efficient resource allocation, simulation results and the proofs of the proposed propositions are provided for the completeness of this dissertation
Geometric frequency reuse for irregular cellular networks
PhD ThesisThis thesis uniquely addresses challenges of bandwidth management in
cellular networks. The need for enhanced frequency assignment strategies
in Long term evolution (LTE) systems arises due to the limiting
e ects of intercell interference (ICI). In this study, the realistic scenario
of irregular network coverage patterns is considered, and in addition,
Heterogeneous cellular networks (HetNets). Firstly, extensive analysis
using simulations is presented for static frequency reuse (FR) techniques
in irregular Homogeneous (single-tier) cellular networks. Investigation
was carried out over several network positional and deployment layouts.
Second, a model is developed for irregular networks by de ning frameworks
for their location parameters and relationships, FR bandwidth and
power assignment, and the probability of interference in partitioned FR
schemes. A novel Geometric FR (GeoFRe) algorithm is then proposed
for single-tier networks with random BS placements. Third, an optimization
framework based on user fairness is proposed and implemented
for single-tier networks based on the concept of virtual UEs in di erent
BS regions. Finally, a framework for HetNets is presented where macro
and small BS deployments have imperfect coverage grid patterns. Performance
analysis is then carried out for two implementations of the Soft
FR (SFR) algorithm. Results from this research provide detailed analysis
on impact of BS irregularity on UE performance under FR schemes, a
simpli ed framework for modelling irregular macro BS, an improved FR
model, accurate computations for the area of irregular network coverage
patterns for intelligent bandwidth assignment, an optimization framework
to improve user fairness (and edge UE performance) in single-tier
networks and an FR model with performance analysis for irregular Het-
Nets.National Information Technology Development Agency (NITDA) and
Federal University of Technology Minna, both in Nigeria for o ering me
scholarship and support