The aim of this thesis is to investigate key issues encountered in the design of transmission schemes and receiving techniques for Ultra Wideband (UWB) communication systems. Based on different data rate applications, this work is divided into two parts, where energy efficient and robust physical layer solutions are proposed, respectively. Due to a huge bandwidth of UWB signals, a considerable amount of multipath arrivals with various path gains is resolvable at the receiver. For low data rate impulse radio UWB systems, suboptimal non-coherent detection is a simple way to effectively capture the multipath energy. Feasible techniques that increase the power efficiency and the interference robustness of non-coherent detection need to be investigated. For high data rate direct sequence UWB systems, a large number of multipath arrivals results in severe inter-/intra-symbol interference. Additionally, the system performance may also be deteriorated by ...

Ultra-wideband (UWB) communication systems use radio signals with a bandwidth in the range of some hundred MHz to several GHz. Radio channels with dense multipath propagation achieve high multipath diversity, which can be used to improve the robustness and capacity of the communication channel. Furthermore the large bandwidth allows to transmit signals with a small power spectral density such that the interference to other radio signals will be negligible, even if they lie within the same frequency band. In this work the focus is on low-complexity receiver architectures for communication systems in presence of multiple-access interference (MAI). The main objective of this thesis is to develop and to study a framework for communications for transmitted reference (TR) UWB systems and energy detection UWB systems. First, we study the hybrid matched-filter (HMF) receiver for TR UWB systems, which employs matched filters ...

This thesis puts a focus on the analysis of key aspects of low-complexity Ultra Wideband (UWB) localizations systems. It is well known that UWB allows for highly robust and accurate ranging even in multipath intensive environments. On the other hand, the huge bandwidth leads to very challenging receiver designs and so low complexity and low power consumption are not achieveable for common receiver structures. The energy detector is a promising alternative. But in contrast to high-complexity coherent receivers, their performance is strongly dependent on the system parameters of the air interface protocol. IEEE 802.15.4a is a UWB standard with high-precision localization capability (better than 1m). The standard defines many system parameters, whose impact on the ranging and localization performance is studied in the thesis. These parameters have also a significant impact on the maximum allowed transmit energy, which limits the ...

This thesis includes a collection of papers that analyze and derive the properties of Ultra Wideband (UWB) radio systems that use Time Hopping for Multiple Access and binary Pulse Position Modulation. New families and generation methods of Time Hopping codes are proposed and properties in terms of cross -correlation, SNR, error probabilities are given. Moreover, interference issues are addressed and an analysis of radio frequency interference effects to a victim UWB receiver is presented. Finally, a cell search procedure in an asynchronous wireless network based on Ultra Wide Band (UWB) radio is proposed.

In multiuser ultra-wideband (UWB) systems, a large number of multipath components (MPCs) are introduced by the channel. One of the main challenges for the receiver is to effectively suppress the interference with affordable complexity. In this thesis, we focus on the linear adaptive interference suppression algorithms for the direct-sequence ultrawideband (DS-UWB) systems in both time-domain and frequency-domain. In the time-domain, symbol by symbol transmission multiuser DS-UWB systems are considered. We first investigate a generic reduced-rank scheme based on the concept of joint and iterative optimization (JIO) that jointly optimizes a projection vector and a reduced-rank filter by using the minimum mean-squared error (MMSE) criterion. A low-complexity scheme, named Switched Approximations of Adaptive Basis Functions (SAABF), is proposed as a modification of the generic scheme, in which the complexity reduction is achieved by using a multi-branch framework to simplify the structure ...

This thesis investigates noncoherent multi-channel ultra-wideband receivers. Noncoherent ultra-wideband receivers promise low power consumption and low processing complexity as they, in contrast to coherent receiver architectures, relinquish the need of complex carrier frequency and phase recovering. Unfortunately, their peak data rate is limited by the delay spread of the multipath radio channel. Noncoherent multi-channel receivers can break this rate limit due to their capability to demodulate multi-carrier signals. Such receivers use an analog front-end to separate the received signals into their sub-channels. In this work, the modeling and optimization of realistic front-end components is addressed and their impact on the system performance of noncoherent multi-channel ultra-wideband receivers is analyzed. With a proposed generalized mathematical framework, it is shown that there exists a variety of noncoherent multi-channel receiver types with similar system performance which differ only in their front-end filters. It ...

It is well known that Ultra WideBand (UWB) transmission is inherently robust against small-scale-fading (SSF) that arises in multipath scattering environments, due to its large signal bandwidth. However, no model with a physical interpretation exists that relates the variations of received signal strength to the signal bandwidth and general channel parameters, like e.g. the average channel power delay profile. Such a model would be of relevance for e.g. system designers, who have to make tradeoffs between system aspects, like complexity and energy efficiency on one hand, and robustness against small-scale fading on the other hand. In this thesis, a model is presented that allows for such a tradeoff analysis, relating the average power delay profile parameters and signal bandwidth to the statistical properties of the SSF. Additionally, it is shown how the uncoded and coded BER of BPSK modulation can ...

In the last decades the world has experienced a massive growth in the demand for wireless services. The recent popularity of hand-held devices with data exchange capabilities over wireless networks, such as smartphones and tablets, increased the wireless data traffic even further. This trend is not expected to cease in the foreseeable future. In fact, it is expected to accelerate as everyday apparatus unrelated with data communications, such as vehicles or household devices, are foreseen to be equipped with wireless communication capabilities. Further, the next generation wireless networks should be designed such that they have increased spectral and energy efficiency, provide uniformly good service to all of the accommodated users and handle many more devices simultaneously. Massive multiple-input multiple-output (Massive MIMO) systems, also termed as large-scale MIMO, very large MIMO or full-dimension MIMO, have recently been proposed as a candidate ...

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Mobile communication networks of the third and future generations are designed to offer high-data rate services like video-telephony and data-transfer. The current Rake receiver architecture will create a shortage in available bandwidth offered to the users. This is not due to a shortage in spectrum but results from inefficient receiver architectures. Spectral efficiency can be increased considerably through multi-user detection techniques in the receiver algorithms. The present thesis investigates iterative re- ceivers for encoded CDMA transmission in the uplink. The iterative receiver is a suboptimal receiver algorithm with manageable complexity. It consists of an inter- ference mitigating multi-user detector, a bank of single-user decoders, and a channel estimator. Instead of deciding on the transmitted symbols right after the first decod- ing, the receiver feeds back tentative decision symbols to mitigate multiple-access interference in the next iteration. Similarly, soft decision symbols ...

In this thesis a modified implementation of the adaptive minimum mean squared error (MMSE) receiver for a time division code division multiple access (TD-CDMA) system for third generation mobile communications is presented. This implementation can operate with spreading sequences which span over a few symbols and in environments where more than one spreading code is allocated to a single user. Two structures which combine the presented MMSE structure and the Rake receiver are also presented in an attempt to combine the advantages of both structures. After analysing the effect on a direct sequence spread spectrum system of multiple access interference and multipath fading induced inter-chip interference, the existing techniques for multiple access interference suppression capabilities are reviewed. Special attention is paid to the adaptive MMSE receiver, which takes into account the effect of multipath fading without requiring any additional channel ...

In this thesis novel implementation approaches for standardized and non-standardized ultra wide-band (UWB) systems are presented. These implementation approaches include signal processing algorithms to achieve processing of UWB signals in transceiver front-ends and in digital back-ends. A parallelization of the transceiver in the frequency-domain has been achieved with hybrid filterbank transceivers. The standardized MB-OFDM signaling scheme allows par- allelization in the frequency domain by distributing the orthogonal multicarrier modulation onto multiple units. Furthermore, the channel’s response to wideband signals has been parallelized in the frequency domain and the effects of the parallelization have been investi- gated. Slight performance decreases are observed, where the limiting effects are truncated sidelobes and filter mismatches in analog front-ends. Measures for the performance loss have been defined. For UWB signal generation, a novel broadband signal generation approach is presented. For that purpose, multiple digital-to-analog converters ...

Code-division multiple-access (CDMA) systems with random spreading and channel uncertainty at the receiver are studied. Frequency selective single antenna, as well as, narrowband multiple antenna channels are considered. Rayleigh fading is assumed in all cases. General Bayesian approach is used to derive both iterative and non-iterative estimators whose performance is obtained in the large system limit via the replica method from statistical physics. The effect of spatial correlation on the performance of a multiple antenna CDMA system operating in a flat-fading channel is studied. Per-antenna spreading (PAS) with random signature sequences and spatial multiplexing is used at the transmitter. Non-iterative multiuser detectors (MUDs) using imperfect channel state information (CSI) are derived. Training symbol based channel estimators having mismatched a priori knowledge about the antenna correlation are considered. Both the channel estimator and the MUD are shown to admit a simple ...

In recent years, inertial sensors have undergone major developments. The quality of their measurements has improved while their cost has decreased, leading to an increase in availability. They can be found in stand-alone sensor units, so-called inertial measurement units, but are nowadays also present in for instance any modern smartphone, in Wii controllers and in virtual reality headsets. The term inertial sensor refers to the combination of accelerometers and gyroscopes. These measure the external specific force and the angular velocity, respectively. Integration of their measurements provides information about the sensor’s position and orientation. However, the position and orientation estimates obtained by simple integration suffer from drift and are therefore only accurate on a short time scale. In order to improve these estimates, we combine the inertial sensors with additional sensors and models. To combine these different sources of information, also ...

Compressed sensing (CS) is a recently introduced signal acquisition framework that goes against the traditional Nyquist sampling paradigm. CS demonstrates that a sparse, or compressible, signal can be acquired using a low rate acquisition process. Since noise is always present in practical data acquisition systems, sensing and reconstruction methods are developed assuming a Gaussian (light-tailed) model for the corrupting noise. However, when the underlying signal and/or the measurements are corrupted by impulsive noise, commonly employed linear sampling operators, coupled with Gaussian-derived reconstruction algorithms, fail to recover a close approximation of the signal. This dissertation develops robust sampling and reconstruction methods for sparse signals in the presence of impulsive noise. To achieve this objective, we make use of robust statistics theory to develop appropriate methods addressing the problem of impulsive noise in CS systems. We develop a generalized Cauchy distribution (GCD) ...