Effects of Channel Estimation and Implementation on the Performance of MIMO Wireless Systems

Bit-rate and quality of service demands of new wireless communication standards are pushing signal theory and algorithm implementation to their limits. One of the main strategies which are being used to achieve the demanded rates is the multiple input-multiple output (MIMO) technique, which employs multiple antennas, both at transmission and reception. This PhD dissertation concentrates on the analysis of the effects of channel estimation, specially complex due to the number of parameters to estimate, on the performance of MIMO detectors, focusing on both practical and theoretical aspects. The practical analysis has been addressed by designing and developing a real-time wireless MIMO communication platform. A whole 2 X 2 system has been implemented which has allowed to evaluate the eects of a real hardware implementation on the performance of the MIMO receiver. A zero-forcing (ZF) detector and a sphere decoder (SD) ...

Mendicute, Mikel — University of Mondragon


Design and Evaluation of OFDM Radio Interfaces for High Mobility Communications

In the last two decades, multicarrier modulations have emerged as a low complexity solution to combat the effects of the multipath in wireless communications. Among them, Orthogonal Frequency Division Multiplexing (OFDM) is possibly the most studied modulation scheme, and has also been widely adopted as the foundation of industry standards such as WiMAX or LTE. However, OFDM is sensitive to time-selective channels, which are featured in mobility scenarios, due to the appearance of Inter-Carrier Interference (ICI). Implementation of hardware equipment for the end user is usually implemented in dedicated chips, but in research environments, more flexible solutions are preferred. One popular approach is the so-called Software Defined Radio (SDR), where the signal processing algorithms are implemented in reconfigurable hardware such as Digital Signal Processors (DSPs) and Field Programmable Gate Arrays (FPGAs). The aim of this work is two-fold. On the ...

Suárez Casal, Pedro — University of A Coruña


Assessment and Real Time Implementation of Wireless Communications Systems and Applications in Transportation Systems

The fourth and fifth generation wireless communication systems (4G and 5G) use a physical layer (PHY) based on multicarrier modulations for data transmission using high bandwidth. This type of modulations has shown to provide high spectral efficiency while allowing low complexity radio channel equalization. These systems use OFDMA as a mechanism for distributing the available radio resources among different users. This allocation is done by assigning a subset of subcarriers to each user in a given instant of time. This provides great flexibility to the system that allows it to adapt to both the quality of service requirements of users and the radio channel state. The media access layer (MAC) of these systems is in charge of configuring the multiple OFDMA PHY layer parameters, in addition to managing the data flows of each user, transforming the higher layer packets into ...

Carro Lagoa, Ángel — University of A Coruña


Testbed-based Evaluation of Mobile Communication Systems

The ever increasing demand for mobility calls for new mobile communication systems that deal more efficiently with the very limited bandwidth available. While such systems do exist and work well in computer simulations, little is known about their performance under real world conditions. Little is also known about how to best determine and compare the throughput performance of such wireless communication schemes in specific, realistic outdoor scenarios. The range of effective answers spans from performing numerical simulations to building prototypes. In recent years we have determined that a cost, time, and manpower efficient ---as well as effective--- method is that of carrying out quasi-realtime testbed measurements. In this approach, all possible transmit data is generated off-line in Matlab, but only the required data is then transmitted over a wireless channel which is altered by moving the receive antennas. The for ...

Caban, Sebastian — Vienna University of Technology


Analog Joint Source Channel Coding for Wireless Communications

In 1948, the Shannon’s work titled ”A mathematical theory of communication” completely revolutionized the way to understand the problem of the reliable communications. He showed that any communications system is able to transmit with an arbitrarily low error probability as long as the transmission rate is kept below a certain limit. The separation between the source and channel coding was also shown as the optimal strategy to achieve the theoretical limits. Those ideas inspire the development of a whole digital communication theory focused on building more and more sophisticated coding schemes. It leads to most of communication systems were designed according to a digital approach and the separation principle from that moment, whereas other alternatives were set aside. However, in the last years, communication systems based on a jointly optimization of the source and channel encoder has aroused the interest ...

Fresnedo Arias, Óscar — University of A Coruña


Waveform Advancements and Synchronization Techniques for Generalized Frequency Division Multiplexing

To enable a new level of connectivity among machines as well as between people and machines, future wireless applications will demand higher requirements on data rates, response time, and reliability from the communication system. This will lead to a different system design, comprising a wide range of deployment scenarios. One important aspect is the evolution of physical layer (PHY), specifically the waveform modulation. The novel generalized frequency division multiplexing (GFDM) technique is a prominent proposal for a flexible block filtered multicarrier modulation. This thesis introduces an advanced GFDM concept that enables the emulation of other prominent waveform candidates in scenarios where they perform best. Hence, a unique modulation framework is presented that is capable of addressing a wide range of scenarios and to upgrade the PHY for 5G networks. In particular, for a subset of system parameters of the modulation ...

Gaspar, Ivan — Technische Universität Dresden


Design and Exploration of Radio Frequency Identification Systems by Rapid Prototyping

In this thesis I describe the setup and design of a flexible rapid prototyping platform for RFID systems to provide an experimental verification environment for RFID systems, that allows their real-time exploration in distinct measurement setups. Furthermore, I use this system to test the feasibility of novel signal processing algorithms for RFID reader receivers, which promise a performance increase to state-of-the-art-receivers. Three different scenarios are considered: 1. In the first scenario, a single tag communicates with a single receive antenna reader. The performance of the optimal maximum likelihood sequence decoder is identified, and losses due to channel estimation and synchronisation are discussed. Due to the wide deviation from the nominal data rate in the uplink communication, especially synchronisation shows to be a critical issue. 2. In the second scenario, the single tag communicates with a multiple receive antenna RFID reader. ...

Angerer, Christoph — Vienna University of Technology


OFDM Air-Interface Design for Multimedia Communications

The aim of this dissertation is the investigation of the key issues encountered in the development of wideband radio air-interfaces. Orthogonal frequency-division multiplexing (OFDM) is considered as the enabling technology for transmitting data at extremely high rates over time-dispersive radio channels. OFDM is a transmission scheme, which splits up the data stream, sending the data symbols simultaneously at a drastically reduced symbol rate over a set of parallel sub-carriers. The first part of this thesis deals with the modeling of the time-dispersive and frequency-selective radio channel, utilizing second order Gaussian stochastic processes. A novel channel measurement technique is developed, in which the RMS delay spread of the channel is estimated from the level-crossing rate of the frequency-selective channel transfer function. This method enables the empirical channel characterization utilizing simplified non-coherent measurements of the received power versus frequency. Air-interface and multiple ...

Witrisal, Klaus — Delft University of Technology


Testbed Design for Wireless Communications Systems Assessment

Since Marconi succeeded in carrying out the first wireless transmission in 1894, experimental research has been always linked with wireless communications. Today, most wireless communications research relies only on computer simulations. Although computer simulations are necessary and recommendable for wireless systems evaluation, they only reflect the simulation environment rather than the actual scenarios in which wireless systems operate. Consequently, it is desirable to assess wireless communications systems in real-world scenarios while, at the same time, keeping the required effort within reasonable terms. Among the different strategies suitable for undertaking such assessment, the testbed approach constitutes a simple and flexible enough solution based on the software-defined radio concept in which only the fundamental operations (usually the transmission and the acquisition) are carried out in real- time, while the remaining tasks are implemented off-line in high-level programming languages (e.g. MATLAB) and using ...

Garcia Naya, Jose Antonio — Universidade da Coruna


Advanced Signal Processing Concepts for Multi-Dimensional Communication Systems

The widespread use of mobile internet and smart applications has led to an explosive growth in mobile data traffic. With the rise of smart homes, smart buildings, and smart cities, this demand is ever growing since future communication systems will require the integration of multiple networks serving diverse sectors, domains and applications, such as multimedia, virtual or augmented reality, machine-to-machine (M2M) communication / the Internet of things (IoT), automotive applications, and many more. Therefore, in the future, the communication systems will not only be required to provide Gbps wireless connectivity but also fulfill other requirements such as low latency and massive machine type connectivity while ensuring the quality of service. Without significant technological advances to increase the system capacity, the existing telecommunications infrastructure will be unable to support these multi-dimensional requirements. This poses an important demand for suitable waveforms with ...

Cheema, Sher Ali — Technische Universität Ilmenau


Space-Time Block Coding for Multiple Antenna Systems

The demand for mobile communication systems with high data rates has dramatically increased in recent years. New methods are necessary in order to satisfy this huge communications demand, exploiting the limited resources such as bandwidth and power as efficient as possible. MIMO systems with multiple an- tenna elements at both link ends are an efficient solution for future wireless communications systems as they provide high data rates by exploiting the spatial domain under the constraints of limited bandwidth and transmit power. Space-Time Block Coding (STBC) is a MIMO transmit strategy which exploits transmit diversity and high reliability. STBCs can be divided into two main classes, namely, Orthogonal Space-Time Block Codes (OSTBCs) and Non-Orthogonal Space-Time Block Codes (NOSTBCs). The Quasi-Orthogonal Space-Time Block Codes (QSTBCs) belong to class of NOSTBCs and have been an intensive area of research. The OSTBCs achieve full ...

Badic, B. — Vienna University of Technology


Study and optimization of multi-antenna systems associated with multicarrier modulations

Since several years, multi-antenna systems are foreseen as a potential solution for increasing the throughput of future wireless communication systems. The aim of this thesis is to study and to improve the transmitter and receiver's techniques of these MIMO (Multiple Input Multiple Output) systems in the context of a multi-carrier transmission. On the one hand, the OFDM (Orthogonal Frequency Division Multiplex) modulation, which transform a frequency selective channel into multiple non frequency selective channels, is particularly well adapted to the conception of MIMO receivers with low complexity. On the other hand, two techniques allowing to improve the exploitation of frequential and/or temporal diversities are associated with OFDM, namely linear precoding (LP-OFDM) and CDMA in a MC-CDMA (Multicarrier Code division Multiplex Access) scheme. We have associated LP-OFDM and MC-CDMA with two MIMO techniques which require no channel state information at the ...

LE NIR, Vincent — INSA de Rennes


Measurement-based Performance Evaluation of WiMAX and HSDPA

In this work, a realistic physical layer performance evaluation of High Speed Downlink Packet Access (HSDPA) as well as IEEE 802.16-2004, commonly referred to as Worldwide Inter-operability for Microwave Access (WiMAX), is provided. The performance evaluation is carried out in two measurement campaigns that took place in an alpine and an urban environment. Both, WiMAX and HSDPA use adaptive modulation and coding to adapt the channel coding rate and the size of the symbol alphabet to the current channel conditions. Additionally, both systems allow for multiple transmit and multiple receive antennas to increase the spectral efficiency and the reliability of the transmission. While WiMAX utilizes multiple transmit antennas by simple Alamouti space-time coding, HSDPA implements a closed-loop system with channel adaptive spatial precoding. The necessary, quantized channel information is fed back from the user equipment to the base station. The ...

Mehlfuehrer, Christian — Vienna University of Technology


Phase readout for satellite interferometry

This thesis describes the development of digital phase readout systems, so-called phasemeters, required for performing precise length measurements in and between satellites with laser interferometry at frequencies below 1 Hz. These technologies have been studied in the scope of the planned space-borne gravitational wave detector LISA (Laser Interferometer Space Antenna), and of future satellite geodesy missions such as GRACE (Gravity Recovery and Climate Experiment) Follow-On. The studies presented here were conducted between 2010 and 2013 at the Albert Einstein Institute in Hannover, Germany. The first part of this thesis provides a comprehensive overview of the basic concepts of inter-satellite interferometry. The analogue and digital parts of the phase measurement chain are described, with a focus on the design elements that are critical for achieving urad/sqrt(Hz) performance levels under the extreme conditions of the inter-satellite link. Digital signal simulations, as well ...

Gerberding, Oliver — Max Planck Institute for Gravitational Physics and Leibniz Universität Hannover


Massive MIMO: Fundamentals and System Designs

The last ten years have seen a massive growth in the number of connected wireless devices. Billions of devices are connected and managed by wireless networks. At the same time, each device needs a high throughput to support applications such as voice, real-time video, movies, and games. Demands for wireless throughput and the number of wireless devices will always increase. In addition, there is a growing concern about energy consumption of wireless communication systems. Thus, future wireless systems have to satisfy three main requirements: i) having a high throughput; ii) simultaneously serving many users; and iii) having less energy consumption. Massive multiple-input-multiple-output (MIMO) technology, where a base station (BS) equipped with very large number of antennas (collocated or distributed) serves many users in the same time-frequency resource, can meet the above requirements, and hence, it is a promising candidate technology ...

Ngo, Quoc Hien — Linköping University

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