588 research outputs found

    Spektralno-efikasna zelena bežična komunikacija pomoću kognitivnog UWB signalnog modela

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    This paper focuses on spectral lines suppression for non-coherent impulse-radio ultra-wideband (IR-UWB) signals in the presence of pulse attenuation and timing jitter. Particular attention is devoted to severely unbalanced (i.e. non-uniform distributed) data sources where a unified spectral analysis is considered for both uncorrelated and correlated M-ary biorthogonal data-stream scenarios. Indeed, the specific novelty insights of this paper are as follows: i) Proposal of a new spectral-efficient signal model as a modified version of transmitted-reference (TR) approach, where each transmitted symbol is represented by a preamble Data-based Statistical Reference (DSR) followed by a set of transmitted data pulses and within this context, the preamble signal is designed to eliminate spectral lines via an adaptive monitoring of data-stream statistics as the optimal spectral policy; ii) Performance analysis in order to derive optimal signal parameters; iii) Evaluation of the system capabilities over different predefined operational modes.Ovaj rad se fokusira na prigušenje spektralnih linija kod ne-koherentnih radio-impulsnih ultra-širokopojasnih (IR-UWB) signala prilikom slabljenja pulsa i vremenskog podrhtavanja. Posebna pažnja je pridana značajno neuravnoteženim (npr. ne-unifornmno distribuiranim) izvorima podataka gdje je jedinstvena spektralna analiza razmatrana za nekorelirane i korelirane M-arne biortogonalne scenarije prijenosa podataka. Novine predstavljene u ovom radu su: i) Novi spektralno-efikasni signalni model koji je modificirana verzija pristupa prijenosom-reference (TR), gdje se svaki preneseni simbol prikazuje pomoću preambule definirane statistikom reference podataka (DSR) koju slijedi skup prenesenih podatkovnih pulseva, te je u tom kontekstu preambula signala dizajnirana kako bi se eliminirale spektralne linije pomoću optimalnog spektralnog kriterija definiranog adaptivnim praćenjem statistike poslanih podataka; ii) Analiza performansi kako bi se dobili optimalni parametri signala i iii) Evaluacija sposobnosti sustava prilikom rada u različitim predefiniranim stanjima

    Radio over fibre distribution systems for ultra-wide band and millimetre wave applications

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    Short range wireless technology such as ultra-wideband (UWB) and 60 GHz millimetre wave (mm-wave) play a key role for wireless connectivity in indoor home, office environment or large enclosed public areas. UWB has been allocated at the frequency band 3.1-10.6 GHz with an emission power below -41.3 dBm. Mm-wave signals around 60 GHz have also attracted much attention to support high-speed data for short range wireless applications. The wide bandwidth and high allowable transmit power at 60 GHz enable multi-Gbps wireless transmission over typical indoor distances. Radio-over-fibre (RoF) systems are used to extend the propagation distance of both UWB and mm-wave signals over hundred of meters inside a building. UWB or mm-wave signals over fibre can be generated first at the central office before being distributed to the remote access points through optical fibre. In this work, we investigate two new techniques to generate and distribute UWB signals. These techniques are based on generating Gaussian pulse position modulation (PPM) using a gain switched laser (GSL). The simulation and experimental results have been carried out to show the suitability of employing gain switching in UWB over fibre systems (UWBoF) to develop a reliable, simple, and low cost technique for distributing UWB pulses. The second part of this work proposes two configurations for optical mm-wave generation and transmission of 3 Gbps downstream data based on GSL. We investigate the distribution of these two methods over fibre with wireless link, and demonstrate the system simplicity and cost efficiency for mm-wave over fibre systems. Both configurations are simulated to verify our obtained results and show system performance at higher bit rates. In the third part, we generate phase modulated mm-waves by using an external injection of a modulated light source into GSL. The performance of this system is experimentally investigated and simulated for different fiber links

    Transceiver design and system optimization for ultra-wideband communications

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    This dissertation investigates the potential promises and proposes possible solutions to the challenges of designing transceivers and optimizing system parameters in ultra-wideband (UWB) systems. The goal is to provide guidelines for UWB transceiver implementations under constraints by regulation, existing interference, and channel estimation. New UWB pulse shapes are invented that satisfy the Federal Communications Commission spectral mask. Parameters are designed to possibly implement the proposed pulses. A link budget is quantified based on an accurate frequency-dependent path loss calculation to account for variations across the ultra-wide bandwidth of the signal. Achievable information rates are quantified as a function of transmission distance over additive white Gaussian noise and multipath channels under specific UWB constraints: limited power spectral density, specific modulation formats, and a highly dispersive channel. The effect of self-interference (SI) and inter-symbol interference (ISI) on channel capacity is determined, and modulation formats that mitigate against this effect is identified. Spreading gains of familiar UWB signaling formats are evaluated, and UWB signals are proved to be spread spectrum. Conditions are formulated for trading coding gain with spreading gain with only a small impact on performance. Numerical results are examined to demonstrate that over a frequency-selective channel, the spreading gain may be beneficial in reducing the SI and ISI resulting in higher information rates. A reduced-rank adaptive filtering technique is applied to the problem of interference suppression and optimum combining in UWB communications. The reduced-rank combining method, in particular the eigencanceler, is proposed and compared with a minimum mean square error Rake receiver. Simulation results are evaluated to show that the performance of the proposed method is superior to the minimum mean square error when the correlation matrix is estimated from limited data. Impact of channel estimation on UWB system performance is investigated when path delays and path amplitudes are jointly estimated. Cramér-Rao bound (CRB) expressions for the variance of path delay and amplitude estimates are formulated using maximum likelihood estimation. Using the errors obtained from the CRB, the effective signal-to-noise ratio for UWB Rake receivers employing maximum ratio combining (MRC) is devised in the presence of channel path delay and amplitude errors. An exact expression of the bit error rate (BER) for UWB Rake receivers with MRC is derived with imperfect estimates of channel path delays and amplitudes. Further, this analysis is applied to design optimal transceiver parameters. The BER is used as part of a binary symmetric channel and the achievable information rates are evaluated. The optimum power allocation and number of symbols allocated to the pilot are developed with respect to maximizing the information rate. The optimal signal bandwidth to be used for UWB communications is determined in the presence of imperfect channel state information. The number of multipath components to be collected by Rake receivers is designed to optimize performance with non-ideal channel estimation

    Communication Subsystems for Emerging Wireless Technologies

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    The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels

    Realization Limits of Impulse-Radio UWB Indoor Localization Systems

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    In this work, the realization limits of an impulse-based Ultra-Wideband (UWB) localization system for indoor applications have been thoroughly investigated and verified by measurements. The analysis spans from the position calculation algorithms, through hardware realization and modeling, up to the localization experiments conducted in realistic scenarios. The main focus was put on identification and characterization of limiting factors as well as developing methods to overcome them

    Performance of Bit Error Rate and Power Spectral Density of Ultra Wideband with Time Hopping Sequences.

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    This thesis focuses on several modulation methods for an ultra wideband (UWB) signal. These methods are pulse position modulation (PPM), binary phase shift keying (BPSK), on/off key shifting (OOK), and pulse amplitude modulation (PAM). In addition, time hopping is considered for these modulation schemes, where the capacity per time frame of time hopping PPM is studied using different spreading ratios. This thesis proves that with the addition of time hopping to all types of modulated UWB signals, the performance of power spectral density improves in all aspects, despite the increase of data per time frame. Note that despite the increase of data per frame, the bit error rate remains the same as standard non-time hopping UWB modulated signals

    DSP algorithm and system design for UWB communication systems

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    Master'sMASTER OF ENGINEERIN
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