MIMO channel modelling and simulation for cellular and mobile-to-mobile

Recently, mobile-to-mobile (M2M) communications have received much attention due to several emerging applications, such as wireless mobile ad hoc networks, relay-based cellular networks, and dedicated short range communications (DSRC) for intelligent transportation systems (e.g., IEEE 802.11p standard). Different from conventional fixed-to-mobile (F2M) cellular systems, in M2M systems both the transmitter (Tx) and receiver (Rx) are in motion and often equipped with low elevation antennas. Multiple-input-multiple-output (MIMO) technologies, employing multiple antennas at both the Tx and Rx, have widely been adopted for the third generation (3G) and beyond-3G (B3G) F2M cellular systems due to their potential benefits of improving coverage, link reliability, and overall system capacity. More recently, MIMO has been receiving more and more attention for M2M systems as well. Reliable knowledge of the propagation channel obtained from channel measurements and corresponding channel models serve as the enabling foundation for the design and analysis of MIMO F2M and M2M systems. Furthermore, the development of accurate MIMO F2M and M2M channel simulation models plays a major role in the practical simulation and performance evaluation of these systems. These form the primary motivation behind our research on MIMO channel modelling and simulation for F2M cellular and M2M communication systems. In this thesis, we first propose a new wideband theoretical multiple-ring based MIMO regular-shaped geometry-based stochastic model (RS-GBSM) for non-isotropic scattering F2M macro-cell scenarios and then derive a generic space-time-frequency (STF) correlation function (CF). The proposed theoretical reference wideband model can be reduced to a narrowband one-ring model, a new closed-form STF CF of which is derived as well. Narrowband and wideband sum-of-sinusoids (SoS) simulation models are then developed, demonstrating a good agreement with the corresponding reference models in terms of correlation functions. Secondly, based on a well-known narrowband two-ring single-input single-output (SISO) M2M channel reference model, we propose new deterministic and stochastic SoS simulation models for non-isotropic scattering environments. The proposed deterministic simulator is the first SISO M2M deterministic simulator with good performance, while the proposed stochastic simulator outperforms the existing one in terms of fitting the desired statistical properties of the corresponding reference model. Thirdly, a new adaptive narrowband MIMO M2M RS-GBSM is proposed for nonisotropic scattering environments. To the best of our knowledge, the proposed M2M model is the first RS-GBSM that has the ability to study the impact of the vehicular traffic density on channel statistics. From the proposed theoretical reference model, we comprehensively investigate some important M2M channel statistics including the STF CF, space-Doppler-frequency power spectral density, envelope level crossing rate, and average fade duration. A close agreement between some channel statistics obtained from the proposed reference model and measurement data is observed, confirming the utility of our model. Finally, we extend the above narrowband model to a new wideband MIMO M2M RSGBSM with respect to the frequency-selectivity. The proposed wideband reference model is validated by observing a good match between some statistical properties of the theoretical model and available measurement data. From the wideband reference model, we further design new wideband deterministic and stochastic SoS simulation models. The proposed wideband simulators can be easily reduced to narrowband ones. The utilities of the newly derived narrowband and wideband simulation models are validated by comparing their statistical properties with those of the corresponding reference models. The proposed channel reference models and simulators are expected to be useful for the design, testing, and performance evaluation of future MIMO cellular and M2M communication systems.Scottish Funding Counci

Antennas and Propagation

This Special Issue gathers topics of utmost interest in the field of antennas and propagation, such as: new directions and challenges in antenna design and propagation; innovative antenna technologies for space applications; metamaterial, metasurface and other periodic structures; antennas for 5G; electromagnetic field measurements and remote sensing applications

Design of indoor communication infrastructure for ultra-high capacity next generation wireless services

The proliferation of data hungry wireless devices, such as smart phones and intelligent sensing networks, is pushing modern wireless networks to their limits. A significant shortfall in the ability of networks to meet demand for data is imminent. This thesis addresses this problem through examining the design of distributed antenna systems (DAS) to support next generation high speed wireless services that require high densities of access points and must support multiple-input multiple-output (MIMO) protocols. First, it is shown that fibre links in DAS can be replaced with low-cost, broadband free-space optical links, termed radio over free-space optics (RoFSO) links. RoFSO links enable the implementation of very high density DAS without the need for prohibitively expensive cabling infrastructure. A 16m RoFSO link requiring only manual alignment is experimentally demonstrated to provide a spurious-free dynamic range (SFDR) of > 100dB/Hz^2/3 over a frequency range from 300MHz- 3.1GHz. The link is measured to have an 802.11g EVM dynamic range of 36dB. This is the first such demonstration of a low-cost broadband RoFSO system. Following this, the linearity performance of RoFSO links is examined. Because of the high loss nature of RoFSO links, the directly-modulated semiconductor lasers they use are susceptible to high-order nonlinear behaviour, which abruptly limits performance at high powers. Existing measures of dynamic range, such as SFDR, assume only third-order nonlinearity and so become inaccurate in the presence of dominant high-order effects. An alternative measure of dynamic range called dynamic-distortion-free dynamic range (DDFDR) is then proposed. For two different wireless services it is observed experimentally that on average the DDFDR upper limit predicts the EVM knee point to within 1dB, while the third-order SFDR predicts it to within 6dB. This is the first detailed analysis of high-order distortion effects in lossy analogue optical links and DDFDR is the first metric able to usefully quantify such behaviour. Next, the combination of emerging MIMO wireless protocols with existing DAS is examined. It is demonstrated for the first time that for small numbers of MIMO streams (up to ~4), the capacity benefits of MIMO can be attained in existing DAS installations simply by sending the different MIMO spatial streams to spatially separated remote antenna units (RAU). This is in contrast to the prevailing paradigm of replicating each MIMO spatial stream at each RAU. Experimental results for two representative DAS layouts show that replicating spatial streams provides an increase of only ~1% in the median channel capacity over merely distributing them. This compares to a 3-4% increase of both strategies over traditional non-DAS MIMO. This result is shown to hold in the multiple user case with 20 users accessing 3 base stations. It is concluded that existing DAS installations offer negligible capacity penalty for MIMO services for small numbers of spatial streams, including in multi-user MIMO scenarios. Finally, the design of DAS to support emerging wireless protocols, such as 802.11ac, that have large numbers of MIMO streams (4-8) is considered. In such cases, capacity is best enhanced by sending multiple MIMO streams to single remote locations. This is achieved using a novel holographic mode division multiplexing (MDM) system, which sends each separate MIMO stream via a different propagation mode in a multimode fibre. Combined channel measurements over 2km of mode-multiplexed MMF and a typical indoor radio environment show in principle a 2x2 MIMO link providing capacities of 10bit/s/Hz over a bandwidth of 6GHz. Using a second experimental set-up it is shown that the system could feasibly support at least up to a 4x4 MIMO system over 2km of MMF with a condition number >15dB over a bandwidth of 3GHz, indicating a high degree of separability of the channels. Finally, it is shown experimentally that when a fibre contains sharp bends (radius between 20mm and 7.2mm) the first 6 mode-groups used for multiplexing exhibit no additional power loss or cross-coupling compared with unbent fibre, although mode-groups 7, 8 and 9 are more severely affected. This indicates that at least 6x6 multiplexing is possible in standard installations with tight fibre bends.For their financial support, I would like to thank the Rutherford Foundation of the Royal Society of New Zealand, the Cambridge Commonwealth Trust and the EPSRC

Compact adaptive planar antenna arrays for robust satellite navigation systems

In den zurückliegenden zwei Jahrzehnten ist die Abhängigkeit der Industriegesellschaft von satellitengestützten Ortungssystemen, Navigationsdiensten und Zeitsignalen dramatisch gewachsen. Darauf aufbauende moderne Anwendungen reichen von hochgenauen Ortungsgeräten bis zu intelligenten Transportsystemen und von der Synchronisation mobiler Netzwerke zu Wetter- und Klimabeobachtung. Dies setzt neue höhere Standards in der Robustheit, Genauigkeit, Verfügbarkeit und Verlässlichkeit moderner Navigationsempfänger voraus. Möglich werden diese Verbesserungen aktuell mit der Einführung von Multiantennensystemen in den Navigationsgeräten. Jedoch wird die Nutzung dieses Ansatzes durch die größeren Abmessungen der Antennenarrays erschwert, weil standardmäßig der Elementabstand zu einer halben Freiraumwellenlänge gewählt wird, was im L Band ca. 10 cm bedeutet. In dieser Arbeit werden kompakte Antennenarrays für Navigationsempfänger mit geringerem Elementabstand vorgeschlagen, die eine Miniaturisierung der Empfängerabmessungen erlauben. Diese kompakten Arrays werden in ihrer Leistungsfähigkeit jedoch durch die negativen Effekte der Verkopplung zwischen den Einzelelementen beeinträchtigt. Für die Beurteilung der Empfängerleistungsfähigkeit existieren verschiedene Qualitätsparameter für Analyse und Entwurf der planaren Arrays. Damit werden z. B. Diversity Freiheitsgrade, Qualität der Richtungsschätzung, Polarisationsreinheit und die wechselseitigen Kopplungen gemessen und eine Entwurfsumgebung wird vorgestellt, in der das optimale kompakte Antennenarray für den jeweiligen Einsatzzweck ausgewählt und konfiguriert werden kann. Dieser Prozess wird durch eine Analyse des Rauschens und seiner Korrelationseigenschaften für den gesamten Empfänger begleitet. Darüber hinaus wird ein analytisches Modell des effektiven carrier-to-interference-plus-noise ratio abgeleitet, um die Leistungsfähigkeit der Navigationsempfänger in Szenarien mit Störsignalen zu untersuchen. Schließlich werden diese Betrachtungen durch den Aufbau eines kompletten Satellitennavigationsempfängers ergänzt, um mit ihm den Nachweis der Funktionsfähigkeit und der stabilen Funktion des entworfenen Systems mit kompaktem Array unter Störereinfluss bei Laborbedingungen und in den reale Außeneinsatz zu erbringen.Over the past two decades, humankind's reliance on global navigation satellite systems for precise positioning, navigation and timing services has grown remarkably. Such advanced applications vary from highly accurate surveying to intelligent transport systems, and from mobile network timing synchronization to weather and climate monitoring. This envisages new and higher standards of robustness, accuracy, coverage and integrity in modern navigation receivers. Recently, this has been accomplished with the incorporation of the multi-element navigation antenna receiver. However, the industrialization of this approach is limited due to the large antenna array size, hindered by the inter-element separation of half of the free-space wavelength, i.e. ≈ 10 cm at L band 1-2 GHz. In this thesis, compact navigation antenna arrays with smaller inter-element separations are proposed for the miniaturization of the overall size. However, these arrays become afflicted with the adverse effects of mutual coupling. Therefore, various figures-of-merit for the analysis and design of a compact planar navigation antenna array, such as performance diversity degrees-of-freedom, directional finding capabilities, and polarization purity, including mutual coupling effects, have been presented. This provides a general framework for the selection and configuration of the optimum compact navigation antenna array. In order to mitigate the mutual coupling, integration of the decoupling and matching network into customized compact navigation antenna array designs is performed. This is fostered by the correlated noise characterization of the complete receiver. Furthermore, an analytical model of the equivalent carrier-to-interference-plus-noise ratio is derived to investigate the navigation performance in interference scenarios. In the end, this is complemented by the implementation of the complete navigation receiver for verification and robustness validation of the derived compact antenna array concepts in indoor and outdoor interference scenarios