The wireless communication industry has seen a tremendous growth in the last few decades. The ever increasing demand to stay connected at home, work, and on the move, with voice and data applications, has continued the need for more sophisticated end-user devices. A typical smart communication device these days consists of a radio system that can access a mixture of mobile cellular services (GSM, UMTS, etc), indoor wireless broadband services (WLAN-802.11b/g/n), short range and low energy personal communications (Bluetooth), positioning and navigation systems (GPS), etc. A smart device capable of meeting all these requirements has to be highly flexible and should be able to reconfigure radio transmitters and receivers as and when required. Further, the radio modules used in these devices should be extremely small so that the device itself is portable. In addition, the device should also be economical ...

iq imbalance CFO OFDM MIMO adaptive equalization rf impairments dirty rf front-end non-idealities broadband communication systems

This Dissertation addresses the signal acquisition problem using antenna arrays in the general framework of Global Navigation Satellite Systems (GNSS) receivers. GNSSs provide the necessary infrastructures for a myriad of applications and services that demand a robust and accurate positioning service. GNSS ranging signals are received with very low signal-to-noise ratio. Despite that the GNSS CDMA modulation offers limited protection against Radio Frequency Interferences (RFI), an interference that exceeds the processing gain can easily degrade receivers' performance or even deny completely the GNSS service. A growing concern of this problem has appeared in recent times. A single-antenna receiver can make use of time and frequency diversity to mitigate interferences, even though the performance of these techniques is compromised in the presence of wideband interferences. Antenna arrays receivers can benefit from spatial-domain processing, and thus mitigate the effects of interfering signals. ...

GNSS detection theory signal acquisition array signal processing GPS galileo interference protection signal quantization satellite positioning software defined receivers fpga systems software processors real-time signal processing rf front-end

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 ...

OFDM digital signal processing channel modeling

With the advent of spectrally efficient wireless communication systems employing modulation schemes with varying amplitude of the communication signal, linearisation techniques for nonlinear microwave power amplifiers have gained significant interest. The availability of fast and cheap digital processing technology makes digital pre-distortion an attractive candidate as a means for power amplifier linearisation since it promises high power efficiency and fleexibility. Digital pre-distortion is further in line with the current efforts towards software defined radio systems, where a principal aim is to substitute costly and inflexible analogue circuitry with cheap and reprogrammable digital circuitry. Microwave power amplifiers are most efficient in terms of delivered microwave output power vs. supplied power if driven near the saturation point. In this operational mode, the amplifier behaves as a nonlinear device, which introduces undesired distortions in the information bear- ing microwave signal. These nonlinear distortions ...

distortion microwave power amplifiers

In this thesis we examine the autonomous oscillator model for synthesis of speech signals. The contributions comprise an analysis of realizations and training methods for the nonlinear function used in the oscillator model, the combination of the oscillator model with inverse filtering, both significantly increasing the number of `successfully' re-synthesized speech signals, and the introduction of a new technique suitable for the re-generation of the noise-like signal component in speech signals. Nonlinear function models are compared in a one-dimensional modeling task regarding their presupposition for adequate re-synthesis of speech signals, in particular considering stability. The considerations also comprise the structure of the nonlinear functions, with the aspect of the possible interpolation between models for different speech sounds. Both regarding stability of the oscillator and the premiss of a nonlinear function structure that may be pre-defined, RBF networks are found a ...

speech synthesis nonlinear signal processing oscillator model bayesian learning

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.

ultra wideband uwb transmission uwb multiple access time hopping uwb interference cell search

This thesis reports on an investigation of various system architectures and receiver structures for cellular communications systems which discriminate users by direct sequence code division multiple access (DSCDMA). Attention is focussed on the downlink of such a spread spectrum system and the influence of a number of design parameters is considered. The objective of the thesis is to investigate signal processing techniques which may be employed either at the receiver, or throughout the system to improve the overall capacity. The principles of spread spectrum communication are first outlined, including a discussion of the relative merits of spreading sequence sets, and a description of various signal processing techniques which are to be applied to the multi-user environment. The measure of system performance is introduced, and the conventional DS-CDMA system is analysed theoretically and through simulation to provide a reference performance level. ...

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 ...

ultra-wide band systems interference mitigation reduced-rank techniques adaptive signal processing.

This work considers behavior modeling of analog to digital converters with applications in the radio frequency range, including the field of telecommunication as well as test and measurement instrumentation, where the conversion from analog to digital signals often is a bottleneck in performance. The models are intended to post-process output data from the converter and thereby improve the performance of the digital signal. By building a model of practical converters and the way in which they deviate from ideal, imperfections can be corrected using post-correction methods. Behavior modeling implies generation of a suitable stimulus, capturing the output data, and characterizing a model. The demands on the test setup are high for converters in the radio frequency range. The test-bed used in this thesis is composed of commercial state-of-the-art instruments and components designed for signal conditioning and signal capture. Further, in ...

ADC analog to digital converters signal processing

Digital subscriber line (DSL) technology is one of the fastest growing broadband internet access media. Whereas asymmetric DSL (ADSL) already offers data rates of a few megabits per second, next-generation ADSL2+ and VDSL promise even higher bit rates to support so-called triple play (high-quality video, voice and high-speed data). The use of a large bandwidth over the phone line (up to 12 MHz for VDSL) induces impairments, such as severe channel distortion, echo, narrow-band radiofrequency interference (RFI) and crosstalk from other DSL systems. DSL communication makes use of so-called discrete multitone (DMT) modulation, supplemented with advanced digital signal processing algorithms, to tackle these impairments and serve a maximum number of customers. In this thesis, we focus on channel equalization and RFI mitigation algorithms that outperform existing algorithms in terms of bit rate. DMT equalization is typically done by means of ...

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 ...

UWB transmitted reference turbo equalization non-linear modeling uwb channel fading statistics

This dissertation deals with the design of satellite-based navigation receivers. The term Global Navigation Satellite Systems (GNSS) refers to those navigation systems based on a constellation of satellites, which emit ranging signals useful for positioning. Although the american GPS is probably the most popular, the european contribution (Galileo) will be operative soon. Other global and regional systems exist, all with the same objective: aid user's positioning. Initially, the thesis provides the state-of-the-art in GNSS: navigation signals structure and receiver architecture. The design of a GNSS receiver consists of a number of functional blocks. From the antenna to the fi nal position calculation, the design poses challenges in many research areas. Although the Radio Frequency chain of the receiver is commented in the thesis, the main objective of the dissertation is on the signal processing algorithms applied after signal digitation. These ...

navigation systems GNSS GPS galileo multipath mitigation tracking direct position estimation bayesian filtering kalman filter particle filtering rao-blackwellization cramer-rao bounds positioning bounds signal processing array signal processing statistics multivariate optimization

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 ...

Air traffic control (ATC) voice radio communication between aircraft pilots and controllers is subject to technical and functional constraints owing to the legacy radio system currently in use worldwide. This thesis investigates the embedding of digital side information, so called watermarks, into speech signals. Applied to the ATC voice radio, a watermarking system could overcome existing limitations, and ultimately increase safety, security and efficiency in ATC. In contrast to conventional watermarking methods, this field of application allows embedding of the data in perceptually irrelevant signal components. We show that the resulting theoretical watermark capacity far exceeds the capacity of conventional watermarking channels. Based on this finding, we present a general purpose blind speech watermarking algorithm that embeds watermark data in the phase of non-voiced speech segments by replacing the excitation signal of an autoregressive signal representation. Our implementation embeds the ...

information hiding digital watermarking speech watermarking legacy system enhancement watermark capacity watermark synchronization air traffic control voice radio analog radio channel

The next generation communication devices are foreseen to not only support a large variety of applications, ranging from speech, audio and video graphics but also be able to maintain connection with many other devices (rather than a single base station) in di®erent changing environments. The aim of the dissertation is to analyze digital modulation and coding techniques for wireless communication systems in realistic transmission scenarios. Furthermore, an important objective of the dissertation is to explore the degrees of freedom that can make the wire- less communication systems overall more adaptive, thereby, resulting in systems that either consume less power for a given performance or o®er more perfor- mance for a given amount of average energy than conventional systems. The techniques/algorithms analyzed in the dissertation are versatile and suitable for both narrowband as well as wideband wireless communication systems for indoor ...