Browsing by Subject "Telecommunications"

Now showing 1 - 6 of 6
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    Open Access
    Architecture of a cognitive non-line-of-sight backhaul for 5G outdoor urban small cells
    (2017) Malila, Bessie; Falowo, Olabisi E; Ventura, Neco
    Densely deployed small cell networks will address the growing demand for broadband mobile connectivity, by increasing access network capacity and coverage. However, most potential small cell base station (SCBS) locations do not have existing telecommunication infrastructure. Providing backhaul connectivity to core networks is therefore a challenge. Millimeter wave (mmW) technologies operated at 30-90GHz are currently being considered to provide low-cost, flexible, high-capacity and reliable backhaul solutions using existing roof-mounted backhaul aggregation sites. Using intelligent mmW radio devices and massive multiple-input multiple-output (MIMO), for enabling point-to-multipoint (PtMP) operation, is considered in this research. The core aim of this research is to develop an architecture of an intelligent non-line-sight (NLOS) small cell backhaul (SCB) system based on mmW and massive MIMO technologies, and supporting intelligent algorithms to facilitate reliable NLOS street-to-rooftop NLOS SCB connectivity. In the proposed architecture, diffraction points are used as signal anchor points between backhaul radio devices. In the new architecture the integration of these technologies is considered. This involves the design of efficient artificial intelligence algorithms to enable backhaul radio devices to autonomously select suitable NLOS propagation paths, find an optimal number of links that meet the backhaul performance requirements and determine an optimal number of diffractions points capable of covering predetermined SCB locations. Throughout the thesis, a number of algorithms are developed and simulated using the MATLAB application. This thesis mainly investigates three key issues: First, a novel intelligent NLOS SCB architecture, termed the cognitive NLOS SCB (CNSCB) system is proposed to enable street-to-rooftop NLOS connectivity using predetermined diffraction points located on roof edges. Second, an algorithm to enable the autonomous creation of multiple-paths, evaluate the performance of each link and determine an optimal number of possible paths per backhaul link is developed. Third, an algorithm to determine the optimal number of diffraction points that can cover an identified SCBS location is also developed. Also, another investigated issue related to the operation of the proposed architecture is its energy efficiency, and its performance is compared to that of a point-to-point (PtP) architecture. The proposed solutions were examined using analytical models, simulations and experimental work to determine the strength of the street-to-rooftop backhaul links and their ability to meet current and future SCB requirements. The results obtained showed that reliable multiple NLOS links can be achieved using device intelligence to guide radio signals along the propagation path. Furthermore, the PtMP architecture is found to be more energy efficient than the PtP architecture. The proposed architecture and algorithms offer a novel backhaul solution for outdoor urban small cells. Finally, this research shows that traditional techniques of addressing the demand for connectivity, which consisted of improving or evolving existing solutions, may nolonger be applicable in emerging communication technologies. There is therefore need to consider new ways of solving the emerging challenges.
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    Open Access
    Essays on telecommunications demand and regulatory policies
    (2017) Mothobi, Onkokame; Grzybowski, Lukasz; Black, Anthony
    This thesis employs models of homogenous and differentiated products to empirically investigate the demand for mobile phone services in Sub-Saharan African countries. The thesis consists of a short introductory chapter, three self-contained empirical chapters, and a summary chapter. In Chapter 2, we use survey data conducted in 2011 in eleven countries in Sub-Saharan African to analyze how the availability of physical infrastructure influences the adoption of mobile phones and usage of mobile services. The availability of physical service infrastructure is approximated by data on night-time light intensity in the areas in which survey respondents reside. After controlling for a number of individual and household characteristics including disposable income, we find that adoption of mobile phones is higher in areas with better physical infrastructure. However, in the group of mobile phone adopters, the use of mobile phones for mobile financial transactions is negatively influenced by the level of infrastructure. Mobile phone users who live in areas with poor infrastructure are more likely to rely on mobile phones to make financial transactions than individuals living in areas with better infrastructure. On the other hand, the use of mobile phones to access services such as email, skype, social media networks and Internet browsing is not dependent on the availability of physical infrastructure. Our results support the notion that mobile phones improve the livelihoods of individuals residing in remote areas by providing them with access to financial services which are otherwise not available physically. Chapter 3 examines the effect of mobile number portability (MNP) on own- and cross-price elasticities. Using quarterly data for 28 mobile operators in seven Sub-Saharan Africa countries between 2010Q4 to 2014Q4 to estimate a differentiated products demand model, we find that MNP increased own-price elasticities of demand in countries that have implemented the facility. This increase in price elasticities may be a result of a reduction in switching costs between operators. On average, the introduction of MNP increases own-price elasticities by 0.47 in absolute value. We compare the level of price elasticities before and after the implementation of MNP in Ghana and Kenya, which implemented this policy in the time period of our study. Our results suggest that in Ghana, MNP increased own-price elasticities by an average of 0.35 in absolute terms from an average value across firms and over time of -0.74. In Kenya, the introduction of MNP increased own-price elasticities by an average of 0.21 in absolute terms from a lower average value across firms and over time of -0.39. However, we find that in Kenya and Ghana the average own-price elasticities remained small even after the implementation of MNP relative to other countries without MNP in place. Thus, our results suggest that MNP is not the ultimate solution for increasing competitiveness within the mobile industry. While in Chapter 3 we use a product differentiated model of demand, in Chapter 4 we make assumptions that allow us to use a homogenous model of demand to examine the effect of regulatory policies on mobile retail prices. Using aggregated quarterly data for eight African countries for the period 2010:Q4 to 2014:Q4, we estimate structural demand and supply equations. We find that mobile termination rates (MTR) have a significant positive impact on mobile retail prices. A decline in average MTR of 10% decreases average mobile retail prices by 2.5%. On the other hand, MNP has an insignificant effect on price and subscriptions in selected African countries. This may be due to inadequate implementation of MNP, which subsequently lead to low demand for porting numbers. The average market conduct in the mobile telecommunications industry for selected African countries can be approximated by Cournot Nash equilibrium. In Chapter 4 we find price elasticities that are closer to 1 in absolute terms. The price elasticity, however, is estimated at an average of -0.27 for Sub-Saharan Africa countries in Chapter 4. We attribute this inconsistency to the different assumptions made in each chapter.
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    Open Access
    Evaluating the effectiveness of Cooperative/Coordinated Multipoint (CoMP) LTE feature in uplink and downlink transmissions
    (2017) Charangwa, Mark; Dlodlo, Mqhele E
    Shannon demonstrated that the channel capacity depends of the ratio of the received signal power to interference plus noise power (SINR). Inter-cell interference caused by neighbouring base stations (BSs) has been identified as one of the most severe problem towards the deployment of LTE technology as it can significantly deteriorate the performance of cellside User Equipment (UE). However, because of regulatory and radiation restrictions as well as operational costs, signal power may only be increased only up to a certain limit to reduce the interference. The other common radio propagation impairment is multipath. Multipath refers to a scenario where multiple copies of a signal propagate to a receiver using different paths. The paths can be created due to signal reflection, scattering and diffraction. As will be discussed later the effects of multipath contribute little to intercell interference because multipath characteristics such as delay spread are compensated for using cyclic prefixes. In this work, we will limit our scope to interference as it has been identified as the main cause of performance degradation for cell edge users due to the full frequency reuse technique used in LTE. To mitigate interference 3GPP devised options of increasing the capacity in LTEAdvanced Release 12 which include the use of spectral aggregation, employing Multiple Input and Multiple Output (MIMO) Antenna techniques, deploying more base stations and micro and femto cells, increasing the degree of sectorisation and Coordinated Multipoint (CoMP). We are primarily interested in evaluating performance improvements introduced when uplink (UL) and downlink (DL) coordinated/cooperative multipoint (CoMP) is enabled in LTE Advanced Release 12 as a way of reducing interference among sites. The CoMP option of reducing interference does not require deployment of new equipment compared to the other options mentioned above hence network deployment costs are minimal. CoMP in theory is known to reduce interference especially for cell edge users and therefore improves network fairness. With CoMP, multiple points coordinate with each other such that transmission of signals to and from other points do not incur serious interference or the interference can even be exploited as a meaningful signal. In September 2011 work on specifications for CoMP support was started in 3GPP LTEAdvanced as one of the core features in LTE-Advanced Release 11 to improve cell edge user throughput as well as the average network throughput. We set to do field measurements in the evaluation of the effectiveness of CoMP in LTE. 3GPP LTE Release 12 was used and cell edge users' performance was the focus. The network operates in 2330 - 2350 MHz band (Channel 40). From the field measurements, it was demonstrated that the CoMP (Scenario 2) feature indeed effective in improving service quality/user experience/fairness for cell edge users. CoMP inherently improves network capacity. A seven (7) percent throughput was noticed.
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    Open Access
    IP addressing, transition and security in 5G networks
    (2018) Bartocho, Evans Kiptoo; Mwangama, Joyce
    The number of devices on the Internet is always increasing and there is need for reliable IP addressing. 5G network will be built on two main technologies; SDN and NFV which will make it elastic and agile compared to its predecessors. Elasticity will ensure that additional devices can always be added to the network. IPv4 addresses are already depleted and cannot support the expansion of the Internet to ensure the realization of future networks. IPv6 addressing has been proposed to support 5G networking because of the sufficient number of addresses that the protocol provides. However, IPv4 addressing will still be used concurrently with IPv6 addressing in networks until they become fully IPv6 based. The structure of IPv4 header is different from IPv6 header hence the two protocols are incompatible. There is need for seamless intercommunication between devices running IPv4 and IPv6 in future networks. Three technologies namely; Dual Stack, Tunneling and Translation have been proposed to ensure that there is smooth transition from IPv4 to IPv6 protocol. This dissertation demonstrates Tunneling of IPv6 over IPv4. Also, this research work reviews network security threats of past networks that are likely to be experienced in 5G networks. To counter them, reliable IP security strategies used in current networks are proposed for use in next generation networks. This dissertation evaluates and analyzes IPv4, IPv6 network and Tunneling models in an SDN network environment. The performance of an IPv4 only network is compared to the IPv6 only network. Also, devices addressed with both protocols are connected. The results obtained illustrate that IPv4 and IPv6 devices can effectively communicate in a 5G network environment. In addition, a tunnel is used to run IPv6 protocol over an IPv4 network. The devices on both ends of the tunnel could communicate with each other effectively.
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    Orthogonal Frequency Division Multiplexing Modelling
    (2021) Katsiru, Noah Kudakwashe; Winberg, Simon
    This work is motivated by the need to understand the performance of Orthogonal Frequency Division Multiplexing (OFDM) and Filterbank Multicarrier (FBMC). Multicarrier techniques are widely being considered for the development of the telecommunication systems such as the Long Term Evolution (LTE) networks, 5th Generation (5G) and beyond. One of the modulation strategies for upcoming 5G mobile communication technologies is FBMC. When compared to OFDM, which is utilised in Fourth Generation (4G) mobile communications technology, it employs multicarrier techniques that are immune to fading produced by transmission of more than one route at a time and also resistant to intersymbol interference. OFDM is one of the popular and highly recommended modulation schemes for LTE applications. OFDM is used for communications and is found in modern digital communication systems (e.g. WiFi, 4G, etc.). OFDM transmits streams of data in many orthogonal sub-carrier frequencies at varying data rates. These carriers do not interfere with each other and thus mitigate inter-symbol interference (ISI) and inter-carrier-interference (ICI). The simulation of an OFDM modulation technique, as well as the performance of OFDM in contrast to an FBMC modulation scheme in terms of delivering the same quantities of data, will be investigated using an ideal communication channel and replicated in a multipath fading channel. Using OFDM modulation techniques, a multipath channel was investigated for realistic simulations. In MATLAB, a picture was used as the input signal to identify the OFDM modulation method with the lowest bit error rate (BER). Quadrature amplitude modulation (QAM) was examined using 16QAM, 32QAM and 64QAM, Binary phase shift keying (BPSK), eight phase shift keying (8PSK), quadrature phase shift keying (QPSK), 16QAM, 32QAM and 64QAM OFDM modulation techniques were used. Channel noise is modelled by adding a white Gaussian noise (AWGN). The channel noise variance decreases with an increase in signal to noise ratio (SNR). 10dB SNR and 20dB SNR inputs were used in the simulations to obtain the BER of the recovered image. QPSK modulation scheme in a multipath fading system produced bit error rates which are higher than BER produced in BPSK modulation scheme. 8PSK modulation scheme produced a higher BER compared to BER of BPSK modulation scheme at the same input SNR. As the modulation order increased the BER increased. 64QAM has the highest BER. Frequency and Phase offsets resulted in symbol error rates increasing as the channel impairments increased in FBMC. The spectral efficiency of OFDM is higher than FBMC spectral efficiency at low burst durations. High burst duration results in FBMC spectral efficiency getting higher than OFDM spectral efficiency. Mild impairments rarely caused symbol recovery errors, but the harsh impairments caused multiple symbol errors. To reduce and eliminate the effects of multipath fading, the least squares channel estimation method is used.
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    Open Access
    SDN based security solutions for multi-tenancy NFV
    (2017) Lejaha, Retselisitsoe; Mwangama, Joyce Bertha
    The Internet continues to expand drastically as a result of explosion of mobile devices, content, server virtualization, and advancement of cloud services. This increase has significantly changed traffic patterns within the enterprise data centres. Therefore, advanced technologies are needed to improve traditional network deployments to enable them to handle the changing network patterns. Software defined networks (SDN) and network function virtualisation (NFV) are innovative technologies that enable network flexibility, increase network and service agility, and support service-driven virtual networks using concepts of virtualisation and softwarisation. Collaboration of these two concepts enable cloud operator to offer network-as-a-service (NaaS) to multiple tenants in a data-centre deployment. Despite the benefits brought by these technologies, they also bring along security challenges that need to be addressed and managed to ensure successful deployment and encourage faster adoption in industry. This dissertation proposes security solution based on tenant isolation, network access control (NAC) and network reconfiguration that can be implemented in NFV multi-tenant deployment to guarantee privacy and security of tenant functions. The evaluation of the proof-of-concept framework proves that SDN based tenant isolation solution provides a high level of isolation in a multi-tenant NFV cloud. It also shows that the proposed network reconfiguration greatly reduces chances of an attacker correctly identifying location and IP addresses of tenant functions within the cloud environment. Because of resource limitation, the proposed NAC solution was not evaluated. The efficiency of this solution for multitenancy NFV has been added as part of future work.