Physical Layer Network Coding for M-QAM MIMO Systems

The aim of this thesis is to design, implement and assess a practical Physical Layer Network Coding (PNC) scheme in multi-user massive Multiple-Input Multiple-Output (MIMO) systems utilizing M-ary Quadrature Amplitude Modulation (M-QAM). PNC is a new technology that is gradually becoming one of the most sought after, as it has the potential to increase network capacity, whilst ensuring that the spectrum is also efficiently used. One of the design goals is to ascertain if combining PNC and massive MIMO is even possible. In accomplishing this goal in a multi-user cellular system with a centralized base station relaying bi-directional communication of M-QAM symbols among user equipment (UEs), a formulation of PNC mapping scheme as a function of clusters of sum and difference (SD) of transmitted symbols from the antennas of the UE pairs is pursued. The simulation results reveal that the proposed PNC scheme achieves twice the spectral efficiency in massive MIMO, without altering the latter's underlying framework and without any degradation in the bit-error-rate (BER). Having established the feasibility of combining PNC and massive MIMO, an evaluation of the proposed scheme against jamming attack is carried out and the simulation results reveal the resilience of the scheme against a barraging jamming noise signal, yet with an increase in spectral efficiency (SE). In addition, extension of the proposed PNC scheme together with Index modulation (IM), a physical layer technique that increases energy efficiency (EE) by utilizing fewer resources to transmit, is designed, implemented and evaluated. The simulation results reveal that combining PNC and IM creates a good balance between EE and SE

The Effect of Ownership Structures on Audit Fees of Listed Firms in Ghana

Research aims: The study examined the effect of ownership structures on audit fees of listed firms in Ghana. The study used four indicators to measure ownership structure: managerial ownership, foreign ownership, government ownership, and substantial (block) ownership.Design/Methodology/Approach: The study sampled 21 listed non-financial firms over ten years, covering the period 2010 to 2019. The study also relied on secondary data extracted from the financial statement of these listed firms. Data were analyzed using descriptive statistics, correlation analysis, and panel regression analysis.Research findings: The study results showed a positive and significant association between foreign ownership and audit fees in Ghana. The study further found a positive and significant relationship between block ownership and audit fees. The results, however, uncovered an insignificant association between government ownership and audit fees. Furthermore, the study reported a positive coefficient between block ownership and audit fees, and the relationship was statistically significant.Theoretical contribution/Originality: The study is among very few studies that have examined ownership structures such as foreign ownership, managerial ownership, government ownership, and block ownership on audit fees in a developing country context and Ghana.Practitioner/Policy implication: This study found that the higher agency conflict through ownership structures will give rise to the higher audit fees paid to external auditors, which managers and auditors should consider in future assignments.Research limitation/implication: The study is limited by geographical area (Ghana), and as such future studies can conduct cross-country analysis of ownership structures on audit fees

Performance Analysis of Physical Layer Network Coding in Massive MIMO Systems with M-QAM Modulations

In this paper, we develop a practical approach for deploying Physical Layer Network Coding (PNC) in multi-user M-Ary Quadrature Amplitude Modulation (M-QAM) Massive Multiple-Input Multiple-Output (MIMO) systems. We formulate a PNC mapping scheme as a function of clusters of estimated summation and difference (SD) of the transmitted symbols from user pairs. Utilizing existing linear detection schemes, such as Zero Forcing (ZF) and Minimum Mean Square Error (MMSE), a cluster of SD symbols are detected using an SD linearly transformed channel matrix. Furthermore, utilizing Maximum a Posteriori (MAP) soft decoding, the SD symbols are mapped to the PNC symbols, leveraging on the PNC symbol that maximizes the likelihood function. For each variant of M-QAM, we derive and simplify a specialization of the generalized PNC mapping function. The error performance results, through simulation, reveal that the proposed PNC scheme achieves twice the spectral efficiency in Massive MIMO, without changing the latter's underlying framework and without any degradation in the bit-error-rate (BER). In fact, our investigation has proved that the BER of the proposed Massive MIMO and PNC is slightly better than that of the conventional Massive MIMO. The feasibility of deploying our proposed PNC scheme in Massive MIMO systems paves way for NC applications to be realized in cellular systems

The Resilience of Massive MIMO PNC to Jamming Attacks in Vehicular Networks

In this article, we investigate the resilience of Massive MIMO Physical Layer Network Coding (PNC) to jamming attack in both sub-6 GHz and millimeter-Wave (mmWave) systems in vehicular networks. Massive MIMO generally is resilient to jamming attacks, and we investigate the impact that PNC has on this resilience, if combined with Massive MIMO. The combination of Massive MIMO and PNC has shown a significant improvement in the bit error rate (BER) in our previous investigation. The corresponding framework is analysed against a barraging attack from a jammer, where the jamming channel is not known to the base station (BS), and the jammer can use any number of transmit antennas. Over Rayleigh channel, our simulation results reveal that Massive MIMO PNC performs better in the lower signal-to-noise ratio (SNR) regions to jamming attacks and this is achieved at twice the spectral efficiency. A similar performance is observed over mmWave channel

A Novel Joint Index Modulation and Physical Layer Network Coding Mechanism for Beyond 5G

In beyond 5G communications, besides energy efficiency (EE) and spectral efficiency (SE), latency and reliability, which are among the main metrics that extreme ultrareliable low-latency communications (URLLC) applications must fulfil. Although new techniques are sought after to meet the crunching requirements of URLLC, combining existing physicallayer techniques have become compelling, attractive and cost saving approach in achieving the same goal. In this paper, we describe a novel mechanism in combining Physical Layer Network Coding (PNC) and Index Modulation (IM) to achieving a balance between SE and EE for URLLC applications beyond 5G. PNC has the potential to increase SE because it leverages on interference from many transmissions occurring at the same time. Although fewer resources are required for IM, the capacity gain is the same as if all transmission resources are used, and as a result, both EE and SE can increase simultaneously. Our simulation results show the feasibility of combining these two key physical-layer techniques, affirming the complementary role this approach will play in meeting the performance KPIs of URLLC, beyond 5G

User Selection for NOMA based MIMO with Physical Layer Network Coding in Internet of Things Applications

Non-orthogonal multiple access (NOMA) based multiple-input multiple-output (MIMO), which has the potential to provide both massive connectivity and high spectrum efficiency, is considered as one of the efficient techniques for sixth generation (6G) wireless systems. In massive Internet of Things (IoT) networks, user-set selection is crucial for enhancing the overall performance of NOMA based systems when compared with orthogonal multiple access (OMA) techniques. In this paper, we propose a user-set selection algorithm for IoT uplink transmission to improve the sum data rate of the NOMA based MIMO systems. In order to exchange data between the selected IoT pairs, we propose to employ wireless physical layer network coding (PNC) to further improve the spectral efficiency and reduce the delay to fulfill the requirements of future IoT applications. Performance evaluations are provided based on both sum data rate and bit error rate for the proposed NOMA based MIMO with PNC in the considered massive IoT scenarios

The influence of the COVID-19 pandemic on audit fees and audit report timeliness of listed firms in Ghana

AbstractThe objective of the study is to examine the effect of the COVID-19 pandemic on audit fees and delays in the release of audit reports among the publicly listed entities in Ghana. The study sampled 35 listed firms over 5 years from 2017 to 2021 by extracting data from the annual report of the firms. The study relied on a panel regression model to estimate the extent to which COVID-19 predicts changes in audit fees and audit report timeliness among listed firms in Ghana. The analysis of the results revealed a positive coefficient between COVID-19 pandemic and audit fees and the positive coefficient was also statistically significant. The study also found a positive and statistically significant association between the COVID-19 pandemic and audit report timeliness which suggest that the pandemic resulted in the delay in the release of audit report among listed entities in Ghana. The combined effect of the two key findings is that the COVID-19 pandemic had a significant influence on audit quality among listed firms in Ghana. The result has significant policy implications especially from the perspective of the Institute of Chartered Accountants Ghana in terms of drawing auditors’ attention to the increased audit risk brought about as a result of the COVID-19 pandemic and the need to compensate for that with the high-quality audit

Point prevalence of asymptomatic Plasmodium infection and the comparison of microscopy, rapid diagnostic test and nested PCR for the diagnosis of asymptomatic malaria among children under 5 years in Ghana.

BackgroundPlasmodium infection among children is a serious public health problem. Asymptomatic malaria infection among humans serves as a significant reservoir for transmitting Plasmodium to uninfected Anopheles mosquitoes, fueling malaria endemicity and asymptomatic malaria may progress to clinical malaria. Therefore, prompt and accurate diagnosis of malaria infection is crucial for the management and control of malaria, especially in endemic areas. This study assessed the point prevalence of asymptomatic malaria infection and evaluated the performance of malaria Rapid Diagnostic Tests (RDT), light microscopy and nested PCR (nPCR) for the diagnosis of asymptomatic malaria infection in a paediatric population in the Atwima Nwabiagya North district, Ghana.MethodsThis cross-sectional study enrolled 500 asymptomatic children aged ≤ 5 years. After consent was obtained from a parent, blood samples were collected from each participant to assess for Plasmodium infection based on histidine rich protein-2 (pfHRP-2)-based malaria RDT, light microscopy and nPCR.ResultsThe point prevalence of asymptomatic malaria by microscopy, RDT, and nPCR were 116/500 (23.2%), 156/500 (31.2%), and 184/500 (36.8%), respectively. Using nPCR as the reference, RDT presented with a perfect sensitivity (100.0%), specificity (100.0%), accuracy (100.0%), and reliability (100.0%) in detecting asymptomatic P. falciparum infection. Likewise, microscopy presented with an excellent specificity and high accuracy in detecting both P. falciparum (100.0%; 85.6%) and P. malariae (100.0%; 100.0%). However, the sensitivity (56.4%) and reliability (56.4%) of microscopy was low for both P. falciparum.ConclusionThe findings of this study indicate a high point prevalence of asymptomatic Plasmodium infection among children in Atwima Nwabiagya North district, Ghana. In the absence of the more sensitive PCR, pfHRP-2-based malaria RDT provides substantial diagnostic sensitivity, specificity, accuracy and reliability and is superior to microscopy