In-Service BER Based Estimation of OFDM PAPR and CFO-induced Peak Phase Deviation

High Peak-to-Average Power Ratio (PAPR) of the transmitted OFDM signal is a well-known major drawback of the Orthogonal Frequency-Division Multiplexing (OFDM), so the High-Power Amplifier (HPA) is therefore necessary to operate in its linear region, i.e. with large back-off between the operating input power and its saturation region, so introducing not only in-band distortion, but also the adjacent channel interference. Specifically with the Long-Term Evolution (LTE) systems downlink, some sort of PAPR reduction, such as e.g. clipping, must be utilized. Considering that in many practical situations, determining PAPR demands complex test equipment, such as e.g. Vector Signal Analyzer (VSA), which might not be available, in this paper, we develop a simple Bit-Error-Rate (BER) based model for the (residual) PAPR estimation, by applying link abstraction, i.e. considering the easy measurable BER degradation due to HPA non-linearity, as if it were the consequence of the according level of additive white Gaussian noise (AWGN) abstracting the HPA distortion, while considering high Signal-to-Noise Ratio (SNR) and long enough cyclic prefix (CP), thus neglecting (real) additive noise and time dispersion (i.e. multipath fading). Moreover, the out-of-service BER testing, which requires network operator to interrupt its revenue-generating traffic, can be substituted by in-service BER estimation from in-phase and quadrature-phase eye diagram closures, measured on live traffic, by means of a simple oscilloscope. The analytical model is verified by the appropriate Monte-Carlo simulations

The Experimental Design of Radio-over-Fibre System for 4G Long Term Evolution

The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is the potential key to meet the exponentially increasing demand of the mobile end users. The entire LTE network architecture and signal processing is carried out at the enhanced NodeB (eNB) level, hence the increased complexity and cost. Therefore, it is not efficient to deploy eNB for the purpose of extending the network coverage. As a solution, deployment of relay node (RN), with radio-over-fibre (RoF) acting as the interface between eNB and RN is proposed. Due to the high path loss and multipath fading, wireless interface would not be the ideal channel between eNB and RN. A detailed investigation is carried out by comparing the Rayleigh multipath fading channel with the optical fibre channel, where the latter achieved a ~31 dB of signal-to-noise ratio (SNR) gain. The distributed feedback laser (DFB) is selected as the direct modulated laser (DML) source, where the modulation method introduces a positive frequency chirp (PFC). The existing mathematical expression does not precisely explain on how the rate equations contribute to PFC. Therefore, an expression for PFC is proposed and derived from the carrier and photon densities of the rate equations. Focusing on theoretical development of DML based RoF system, a varying fast Fourier transform (FFT) scheme is introduced into LTE-Advanced (LTE-A) technology as an alternative design to the carrier aggregation. A range of FFT sizes are investigated with different levels of optical launch power (OLP), the optimum OLP has been defined to be within the range of ~-6 to 0 dBm, which is known as the intermixing region. It is found that FFT size-128 provides improved average system efficiency of ~54% and ~65% in comparison to FFT size-64 and FFT size-128, respectively, within the intermixing region. While fixing FFT size to 128, the investigation is diverted to the optimisation of optical modulators. The author revealed that the performance of dual electrode-Mach Zehnder modulator (DE-MZM) is superior to both DML scheme and single electrode (SE)-MZM, where DE-MZM achieved a transmission span of 88 km and 71 km for 16-quadrature amplitude modulation (QAM) and 64-QAM, respectively. At the initial experimental link design and optimisation stage, an optimum modulation region (OMR) is proposed at the optical modulation index (OMI) of 0.38, which resulted in an average error vector magnitude (EVM) of ~1.01% for a 10 km span. The EVM of ~1.01% is further improved by introducing the optimum OLP region at –2 dBm, where the observed average EVM trimmed to ~0.96%. There is no deviation found in the intermixing region by transmitting the LTE signal through a varying transmission span of 10 to 60 km, additionally, it was also revealed that the LTE RoF nonlinear threshold falls above the OLP of 6 dBm. The proposed system was further developed to accommodate 2×2 multiple-input and multiple-output (MIMO) transmission by utilising analogue frequency division multiplexing (FDM) technique. The studies procured that the resulting output quality of signal at 2 GHz and 2.6 GHz is almost identical with a twofold gain in the peak data rate and no occurrence of intermodulation (IMD). In order to emulate the complete LTE RoF solution, an experimental design of full duplex frequency division duplex (FDD) system with dense wavelength division multiplexing (DWDM) architecture is proposed. It is found that channel spacing of 50 MHz between the downlink (DL) and uplink (UL) introduces severe IMD distortion, where an adjacent channel leakage ratio (ACLR) penalty of 14.10 dB is observed. Finally, a novel nonlinear compensation technique utilising a direct modulation based frequency dithering (DMFD) scheme is proposed. The LTE RoF system average SNR gain observed at OLP of 10 dBm for the 50 km transmission span is ~5.97 dB. External modulation based frequency dithering (EMFD) exhibits ~3 dB of average SNR gain over DMFD method

Performance Analyses of Different MIMO Modes In LTE Release 8 Networks

The multi-antenna techniques are the one of the key features in 3GPP LTE specifications. Thus, the understanding of different transmission modes behaviour, available in LTE, is very important for high quality and cost efficient LTE network deployment. Besides, the lack of available practical studies of this topic makes the problem even more attractive. This master thesis work is focused on measurement based performance analyses of different special multiplexing (SM) modes available in LTE Release 8 networks using the same LTE base stations as used in this study. Field measurements have been carried out in different propagation environments. In analyses, user application throughput and MIMO utilization have been studied to demonstrate the efficiency of each mode. The measurement results are different than the theoretical and simulation based studies. The results clearly show that the open-loop-dynamic SM is the best choice, independent of the environment, for SNR > -2 to -5 dB and can provide up to 3 Mbps or 11.7% advantage over closed loop SM. The open loop static SM is as good as open loop dynamic SM only for very good, SNR > 10 to 15 dB, channel conditions. And, for the bad channel conditions, SNR 15 dB, which means, that there is a significant interference between parallel data streams. The bad performance of the closed loop is associated with low CQI reports for codeword 1 as the UE reduces the SNR for codeword 1 to mitigate the interference between parallel data streams. The results can be generalized only for the studied equipment hardware, software and parameters as the other vendors can have slightly different implementation of some parts of LTE. But any way, the results show that knowledge of the different SM modes behaviour can help to increase the quality of the network

Physical Layer Techniques for High Frequency Wireline Broadband Systems

This thesis collects contributions to wireline and wireless communication systems with an emphasis on multiuser and multicarrier physical layer technology. To deliver increased capacity, modern wireline access systems such as G.fast extend the signal bandwidth up from tens to hundreds of MHz. This ambitious development revealed a number of unforeseen hurdles such as the impact of impedance changes in various forms. Impedance changes have a strong effect on the performance of multi-user crosstalk mitigation techniques such as vectoring. The first part of the thesis presents papers covering the identification of one of these problems, a model describing why it occurs and a method to mitigate its effects, improving line stability for G.fast systems.A second part of the thesis deals with the effects of temperature changes on wireline channels. When a vectored (MIMO) wireline system is initialized, channel estimates need to be obtained. This thesis presents contributions on the feasibility of re-using channel coefficients to speed up the vectoring startup procedures, even after the correct coefficients have changed, e.g., due to temperature changes. We also present extensive measurement results showing the effects of temperature changes on copper channels using a temperature chamber and British cables. The last part of the thesis presents three papers on the convergence of physical layer technologies, more specifically the deployment of OFDM-based radio systems using twisted pairs in different ways. In one proposed scenario, the idea of using the access copper lines to deploy small cells inside users' homes is explored. The feasibility of the concept, the design of radio-heads and a practical scheme for crosstalk mitigation are presented in three contributions

Characterization and Modelling of Scattered Wireless Channel at 60 GHZ in an Underground Mine Gallery

RÉSUMÉ Depuis plus d’une décennie, les applications du système de communication sans fil sont exigeantes et augmentent rapidement pour fournir des services multimédias au public. De nos jours, la recherche se concentre sur la conception de communication sans fil à haute vitesse (i.e., 1 Gbps) en particulier dans des zones denses telles que des salles de conférence, des centres commerciaux,des stades et des lieux d’événements publics ouverts. Des réseaux locaux sans fil (WLAN) et des réseaux cellulaires utilisent des hauts potentiels pour réussir les haut débit de données en utilisant différentes technologies de pointe telles que la coexistence entre l’évaluation à long terme non autorisé (LTE-U) et les canaux Wi-Fi. En outre, la faisabilité d’utiliser le spectre à haute fréquence (i.e,> 6 GHz), une couche physique à 60 GHz pour les réseaux denses sont mis en évidence lorsque des liens de communication à courte distance (par exemple, <10 m) sont nécessaires aussi bien dans WLAN (i.e, WiGig) et le réseau cellulaire (i.e, 5G petite cellule). Cependant, les applications à 60 GHz se dirigent vers la communication sans fil souterraine pour une meilleure géolocalisation, les applications haute définition (HD) de streaming vidéo dans une galerie plus grande longueur (i.e,> 100 m) en raison de sa capacité de formation de faisceau et de plus grande capacité. Pour aider le concepteur du système, il est nécessaire de connaître les informations de propagation du canal sans fil diffusé puisque le plancher de la galerie, le plafond et le mur ont différentes rugosités (i.e.,> 5 mm). Cette thèse présente les résultats de la caractérisation du canal sans fil et la modélisation statistique à 60 GHz d’une mine souterraine à CANMET ayant des galeries dont la profondeur varie entre 40 m et 70 m. Depuis plus d’une décennie, les applications du système de communication sans fil sont exigeantes et augmentent rapidement pour fournir des services multimédias au public. Les résultats montrent que l’écart angulaire de la propagation par trajets multiples est inversement proportionnel à la distance entre l’émetteur et le récepteur. Un phénomène de dispersion solide est également observé dans le canal en observant l’angle de propagation des différents trajets. Des polarisations horizontales (H) et verticales (V) ont été utilisées puisque les diagrammes de rayonnement sont différents et peuvent fournir des comportements de dispersion temporelle différents. Les résultats montrent que l’antenne à polarisation verticale fournit un plus grand nombre de trajets multiples par rapport à polarisation horizontale et une valeur plus élevée de moyenne quadratique (RMS) par rapport à une horizontale. Par ailleurs, les mesures du coefficient de réflexion ont été effectuées pour étudier l’effet de dispersion de la surface rugueuse. Étant donné qu’aucun effet de regroupement sur le canal multitrajets n’a été observé, une approche de modélisation statistique a été considérée en tenant compte des différents trajets parcourus et leur amplitude. Par insertion des paramètres de hauteur de la surface de mesure, les modèles de diffusion connus ont également été analysées pour permettre la mise en oeuvre d’une approche de modélisation du canal dispersif.----------ABSTRACT More than a decade, there is a surge in demand and development of wireless communication system applications to deliver multimedia services. Nowadays the research is focused on the design of high speed (i.e., 1 Gbps) wireless system particularly in dense areas such as conference room, shopping mall, stadium and open public events. Wireless local area network (WLAN) and cellular network are making high potential approaches to fulfill high data rate by using different advanced technologies such as coexistence between Long Term Evaluation Unlicensed (LTE-U) and Wi-Fi Wireless channels. Moreover, the feasibility to use high-frequency spectrum (i.e., > 6 GHz), a physical layer research at 60 GHz for dense networks are highlighted where short-distance communication links (i.e., 100 m) due to its beamforming capability and higher capacity. To assist the system designer, it is necessary to know the scattered wireless channel propagation information since the gallery floor, ceiling and walls consist of the different magnitude of the roughness (i.e., > 5 mm). This thesis presents the results of wireless channel characterization and statistical modeling at 60 GHz where the measurements were carried out in CANMET underground mine (40 m and 70 m gallery depths). Several measurements were conducted with different antenna configurations and polarizations. Results show that angular and temporal dispersion are proportional to the mine gallery dimensions. Results also show that the angular spread of the multipath is inversely proportional to the transmitter receiver separation distance. A strong scattering phenomenon is also observed in the channel by observing multipath angle of arrivals. The use of Horizontal (H) and vertical (V) polarizations were performed due to its different radiation pattern can provide a different temporal dispersion behavior. The results show that a vertically polarized antenna provides a lower value of path loss exponent and a higher value of root mean square (RMS) delay spread compared to a horizontal one. Since no clustering effect was observed, a statistical modeling approach with the multipath arrivals and amplitudes was considered. In addition, the reflection coefficient measurements were conducted to investigate the scattering effect from the rough surface. By inserting measured surface height parameters, the known scattering models were also analyzed to have an idea to implement a modeling approach of the scattered channel

NB-IoT via non terrestrial networks

Massive Internet of Things is expected to play a crucial role in Beyond 5G (B5G) wireless communication systems, offering seamless connectivity among heterogeneous devices without human intervention. However, the exponential proliferation of smart devices and IoT networks, relying solely on terrestrial networks, may not fully meet the demanding IoT requirements in terms of bandwidth and connectivity, especially in areas where terrestrial infrastructures are not economically viable. To unleash the full potential of 5G and B5G networks and enable seamless connectivity everywhere, the 3GPP envisions the integration of Non-Terrestrial Networks (NTNs) into the terrestrial ones starting from Release 17. However, this integration process requires modifications to the 5G standard to ensure reliable communications despite typical satellite channel impairments. In this framework, this thesis aims at proposing techniques at the Physical and Medium Access Control layers that require minimal adaptations in the current NB-IoT standard via NTN. Thus, firstly the satellite impairments are evaluated and, then, a detailed link budget analysis is provided. Following, analyses at the link and the system levels are conducted. In the former case, a novel algorithm leveraging time-frequency analysis is proposed to detect orthogonal preambles and estimate the signals’ arrival time. Besides, the effects of collisions on the detection probability and Bit Error Rate are investigated and Non-Orthogonal Multiple Access approaches are proposed in the random access and data phases. The system analysis evaluates the performance of random access in case of congestion. Various access parameters are tested in different satellite scenarios, and the performance is measured in terms of access probability and time required to complete the procedure. Finally, a heuristic algorithm is proposed to jointly design the access and data phases, determining the number of satellite passages, the Random Access Periodicity, and the number of uplink repetitions that maximize the system's spectral efficiency