All wireless receivers have some degree of nonlinearity that can negatively impact performance. Two major effects from this nonlinearity are power compression, which leads to amplitude and phase distortions in the received signal, and desensitization caused by a high powered interfering signal at an adjacent channel. As the RF spectrum becomes more crowded, the interference caused by these adjacent signals will become a more significant problem for receiver design. Therefore, having bit and symbol error rate expressions that take the receiver nonlinearity into account will allow for determining the linearity requirements of a receiver. This thesis examines the modeling of the probability density functions of M-PAM and M-QAM signals through an AWGN channel taking into account the impact of receiver nonlinearity. A change of variables technique is used to provide a relationship between the pdf of these signals with a linear receiver and the pdf with a nonlinear receiver. Additionally, theoretical bit and symbol error rates are derived from the pdf expressions. Finally, this approach is extended by deriving pdf and error rate expressions for these signals when nearby blocking signals cause desensitization of the signal of interest. Matlab simulation shows that the derived expressions for a nonlinear receiver have the same accuracy as the accepted expressions for linear receivers. / Master of Science / All wireless receivers have some amount of nonlinearity that can distort a received signal and impact performance. For amplitude modulated signals, the power compression caused by the nonlinear receiver will cause distortions in the amplitude and phase of the received signal. Additionally, a high powered interfering signal at a close frequency can decrease the gain and distort the received signal. This thesis examines how the probability density of an amplitude modulated signal with a nonlinear receiver can be modeled for both of these situations. These theoretical probability density functions are used to derive theoretical error rate expressions for the signals both with and without the adjacent channel interference. Simulations in Matlab show that the accuracy of these derived expressions is similar to the accuracies of the linear receiver expressions. These derived expressions will be able to remove the need for time consuming simulation when designing receivers for wireless systems.

This thesis describes the use of a multi-amplitude minimum shift keying (MAMSK) signal in various types of wireless communication system. A MAMSK signal is a bandwidth efficient modulation scheme obtained by superimposing ℳ minimum shift keying (MSK) signals with unequal amplitudes. The overall phase of a MAMSK signal is controlled by the phase of the largest component MSK signal which allows the use of a low-complexity differential detector. A closed form expression for the average bit error rate (BER) for coherent detection of an MAMSK in AWGN is derived and is shown to achieve the same BER as that of square constellation quadrature amplitude modulation (QAM) with the same average transmit power. We describe the design and implementation of a STBC-based MIMO radio system in conjunction with MAMSK modulation. The proposed system provides high capacity data transmission by carrying information not only in the phases but also in the amplitude. Despite using a simple MAMSK differential receiver the system achieves performance within 1 dB of coherent detection. The existing MSK modems in conjunction with STBC could easily be modified to construct the proposed system. The MAMSK modulation scheme is extended to a multiuser relaying network where two nodes cooperate in a half-duplex environment to achieve diversity gain. The cooperative scheme is based on superposition modulation using a decode-and-forward (DF) strategy. In the proposed scheme, each node simultaneously transmits its own and the relayed signals by superimposing one on the other. A MAMSK signal is an excellent choice for this type of cooperative communication due its being obtained by a superposition technique. The proposed system exploits the overall phase of a MAMSK signal which allows differential detection and as a result it provides the lowest decoding complexity and memory requirements among the existing superposition based cooperation schemes. The performance of the system is evaluated by simulation, where it is shown that the MAMSK cooperative system outperforms a conventional DF scheme in terms of both power and bandwidth efficiency.

There is a growing demand for the high quality TV programs such as High Definition TV (HDTV). The CATV network is often a suitable solution to address this demand using a CATV modem delivering high data rate digital signals in a cost effective manner, thereby, utilizing a complex digital modulation scheme is inevitable. Exploiting complex modulation schemes, entails a more sophisticated modulator and distribution system with much tighter tolerances. However, there are always distortions introduced to the modulated signal in the modulator degrading signal quality.<p> In this research, the effect of distortions introduced by the RF band pass filter in the modulator will be considered which cause degradations on the quality of the output Quadrature Amplitude Modulated (QAM) signal. Since the RF filter's amplitude/group delay distortions are not symmetrical in the frequency domain, once translated into the base band they have a complex effect on the QAM signal. Using Matlab, the degradation effects of these distortions on the QAM signal such as Bit Error Rate (BER) is investigated.<p> In order to compensate for the effects of the RF filter distortions, two different methods are proposed. In the first method, a complex base band compensation filter is placed after the pulse shaping filter (SRRC). The coefficients of this complex filter are determined using an optimization algorithm developed during this research. The second approach, uses a pre-equalizer in the form of a Feed Forward FIR structure placed before the pulse shaping filter (SRRC). The coefficients of this pre-equalizer are determined using the equalization algorithm employed in a test receiver, with its tap weights generating the inverse response of the RF filter. The compensation of RF filter distortions in base band, in turn, improves the QAM signal parameters such as Modulation Error Ratio (MER). Finally, the MER of the modulated QAM signal before and after the base band compensation is compared between the two methods, showing a significant enhancement in the RF modulator performance.

There is a growing demand for the high quality TV programs such as High Definition TV (HDTV). The CATV network is often a suitable solution to address this demand using a CATV modem delivering high data rate digital signals in a cost effective manner, thereby, utilizing a complex digital modulation scheme is inevitable. Exploiting complex modulation schemes, entails a more sophisticated modulator and distribution system with much tighter tolerances. However, there are always distortions introduced to the modulated signal in the modulator degrading signal quality.<p> In this research, the effect of distortions introduced by the RF band pass filter in the modulator will be considered which cause degradations on the quality of the output Quadrature Amplitude Modulated (QAM) signal. Since the RF filter's amplitude/group delay distortions are not symmetrical in the frequency domain, once translated into the base band they have a complex effect on the QAM signal. Using Matlab, the degradation effects of these distortions on the QAM signal such as Bit Error Rate (BER) is investigated.<p> In order to compensate for the effects of the RF filter distortions, two different methods are proposed. In the first method, a complex base band compensation filter is placed after the pulse shaping filter (SRRC). The coefficients of this complex filter are determined using an optimization algorithm developed during this research. The second approach, uses a pre-equalizer in the form of a Feed Forward FIR structure placed before the pulse shaping filter (SRRC). The coefficients of this pre-equalizer are determined using the equalization algorithm employed in a test receiver, with its tap weights generating the inverse response of the RF filter. The compensation of RF filter distortions in base band, in turn, improves the QAM signal parameters such as Modulation Error Ratio (MER). Finally, the MER of the modulated QAM signal before and after the base band compensation is compared between the two methods, showing a significant enhancement in the RF modulator performance.

Στα πλαίσια της διπλωματικής εργασίας μελετήθηκε μια κατηγορία αλγορίθμων διόρθωσης λαθών που προκύπτουν κατά τη μετάδοση δεδομένων μέσα από ένα ασύρματο τηλεπικοινωνιακό κανάλι. Η μετάδοση των δεδομένων έγινε χρησιμοποιώντας τις διαμορφώσεις BPSK, QPSK, 16 – QAM και 64 – QAM. Η μελέτη επικεντρώθηκε στην περίπτωση της συνελικτικής κωδικοποίησης δεδομένων. Για την υλοποίηση του αποκωδικοποιητή (decoder) μελετήθηκαν συγκριτικά οι αλγόριθμοι Viterbi και SOVA καθώς και οι αντίστοιχες αρχιτεκτονικές υλοποίησης τους σε υλικό, ως προς την πολυπλοκότητα, την κατανάλωση και την ταχύτητά τους για συγκεκριμένη ικανότητα διόρθωσης λαθών που μετράται ως μείωση του BER. Επίσης, μελετήθηκαν τέσσερεις διαφορετικοί τρόποι αποδιαμόρφωσης και αποκωδικοποίησης των δεδομένων για διαμορφώσεις QAM βασισμένοι στον αλγόριθμο Viterbi. Η μεθοδολογία της διπλωματικής περιέλαβε την υλοποίηση ενός πλήρους μοντέλου τηλεπικοινωνιακού συστήματος με μη ιδανικό κανάλι, AWGN, στο οποίο προστέθηκαν μηχανισμοί διόρθωσης λάθους. Η μελέτη έλαβε υπόψη τον κβαντισμό στο δέκτη στην αναπαράσταση δεδομένων καθώς και στα ενδιάμεσα αποτελέσματα. Αξιολογήθηκαν τρόποι κβαντισμού συναρτήσει παραμέτρων του καναλιού, και εντοπίστηκαν τα ελάχιστα αναγκαία μήκη λέξης για την υλοποίηση των αλγορίθμων του δέκτη, λαμβάνοντας υπόψη το trade-off μεταξύ απόδοσης και κόστους υλοποίησης σε υλικό. Με τη χρήση bit-true εξομοιώσεων μελετήθηκαν τρόποι ελαχιστοποίησης της δυναμικής περιοχής που απαιτείται για την αναπαράσταση των ενδιάμεσων μετρικών. Σε κάθε περίπτωση αναλύθηκε η απόδοση των αλγορίθμων με βάση το ποσοστό των λαθών στο δέκτη (BER) ενώ συνεκτιμήθηκε η πολυπλοκότητα της αντίστοιχης υλοποίησης VLSI. / This thesis focuses on a class of algorithms for the correction of errors due of the transmission of data through a wireless telecommunications channel. The modulations employed are BPSK, QPSK, 16-QAM and 64-QAM. The study focuses on convolutional coding. The performance of solutions based on Viterbi and SOVA algorithms are comparatively studied, as well as the corresponding hardware architectures, in terms of the complexity, consumption and speed, while specifications are set in terms of error correction capability, measured in BER. Also, four different ways of combined demodulation and decoding of QAM data are studied based on the Viterbi algorithm. The methodology assumed in this thesis includes the realization of a complete telecommunications system model assuming an additive white gaussian noise channel, AWGN, in which mechanisms of error correction are added. The study takes into consideration the quantization effects in the receiver and in all the intermediary operations of algorithms. It has been found that the ideal quantizer for the receiver is related to channel parameters. In addition the shortest necessary word lengths were identified taking into consideration trade off between output and hardware realization cost. By means of bit-true simulations, ways of minimization of dynamic region, required for the representation intermediary metrics were studied. In every case the performance of algorithms is analyzed in terms of BER, as well as computational cost and impact on VLSI realization.

Les formats de modulation avancés, codant l'information sur la phase, la polarisation ou plusieurs niveaux d'amplitude de la lumière reçoivent aujourd'hui un intérêt croissant. En effet, ceux-ci permettent d'atteindre une meilleure efficacité spectrale et par conséquent des débits plus élevés. Ces caractéristiques sont actuellement très recherchées dans les télécommunications pour répondre à la demande constante d'augmentation de capacité des transmissions optiques fibrées. L'essentiel du travail effectué porte sur la génération de tels signaux dans des sources photoniques monolithiques sur InP faisant appel à un concept nouveau de commutation de phases optiques préfixées avec des modulateurs électro-absorbants. Une comparaison de notre technologie intégrée avec la technologie actuelle de génération de formats de modulation avancés démontre des possibilités nouvelles de réduction de taille, de diminution de consommation énergétique et d'évolution en vitesse de modulation jusqu'à 56 GBauds. Suite à la validation, par simulations, d'architectures de transmetteurs spécifiques pour la génération de formats de modulation avancés, nous réalisons en salle blanche les circuits photoniques intégrés d'étude. Les caractérisations statiques confirment le fonctionnement de toutes les fonctions intégrées des circuits et soulignent l'efficacité de la filière technologique. Pour une première démonstration de fonctionnalité nous choisissons un transmetteur BPSK capable de générer une modulation de phase à 12,4 GB. Ce résultat démontre la plus petite source intégrée BPSK à l'heure actuelle. Un autre circuit capable de générer des formats de modulation plus complexes est aussi caractérisé

In order to meet the ever-growing demand for mobile data, a number of different technologies have been adopted by the fourth generation standardization bodies. These include multiple access schemes such as spatial division multiple access (SDMA), and efficient modulation techniques such as orthogonal frequency division multiplexing (OFDM)-based modulation. The specific objectives of this theses are to develop an effective feedback method for interference management in smart antenna SDMA systems and to design an efficient OFDM-based modulation technique, where an additional dimension is added to the conventional two-dimensional modulation techniques such as quadrature amplitude modulation (QAM). In SDMA time division duplex (TDD) systems, where channel reciprocity is maintained, uplink (UL) channel sounding method is considered as one of the most promising feedback methods due to its bandwidth and delay efficiency. Conventional channel sounding (CCS) only conveys the channel state information (CSI) of each active user to the base station (BS). Due to the limitation in system performance because of co-channel interference (CCI) from adjacent cells in interference-limited scenarios, CSI is only a suboptimal metric for multiuser spatial multiplexing optimization. The first major contribution of this theses is a novel interference feedback method proposed to provide the BS with implicit knowledge about the interference level received by each mobile station (MS). More specifically, it is proposed to weight the conventional channel sounding pilots by the level of the experienced interference at the user’s side. Interference-weighted channel sounding (IWCS) acts as a spectrally efficient feedback technique that provides the BS with implicit knowledge about CCI experienced by each MS, and significantly improves the downlink (DL) sum capacity for both greedy and fair scheduling policies. For the sake of completeness, a novel procedure is developed to make the IWCS pilots usable for UL optimization. It is proposed to divide the optimization metric obtained from the IWCS pilots by the interference experienced at the BS’s antennas. The resultant new metric, the channel gain divided by the multiplication of DL and UL interference, provides link-protection awareness and is used to optimize both UL and DL. Using maximum capacity scheduling criterion, the link-protection aware metric results in a gain in the median system sum capacity of 26.7% and 12.5% in DL and UL respectively compared to the case when conventional channel sounding techniques are used. Moreover, heuristic algorithm has been proposed in order to facilitate a practical optimization and to reduce the computational complexity. The second major contribution of this theses is an innovative transmission approach, referred to as subcarrier-index modulation (SIM), which is proposed to be integrated with OFDM. The key idea of SIM is to employ the subcarrier-index to convey information to the receiver. Furthermore, a closed-form analytical bit error ratio (BER) of SIM OFDM in Rayleigh channel is derived. Simulation results show BER performance gain of 4 dB over 4-QAM OFDM for both coded and uncoded data without power saving policy. Alternatively, power saving policy maintains an average gain of 1 dB while only using half OFDM symbol transmit power.

Approved for public release; distribution is unlimited. / Trellis-Coded Modulation (TCM) is employed with quadrature amplitude modulation (QAM) to provide error correction coding with no expense in bandwidth. There are two common implementations of TCM, namely pragmatic TCM and Ungerboeck TCM. Both schemes employ Viterbi algorithms for decoding but have different code construction. This thesis investigates and compares the performance of pragmatic TCM and Ungerboeck TCM by implementing the Viterbi decoding algorithm for both schemes with 16-QAM and 64-QAM. Both pragmatic and Ungerboeck TCM with six memory elements are considered. Simulations were carried out for both pragmatic and Ungerboeck TCM to evaluate their respective performance. The simulations were done using Matlab software, and an additive white Gaussian noise channel was assumed. The objective was to ascertain that pragmatic TCM, with its reduced-complexity decoding, is more suitable to adaptive modulation than Ungerboeck TCM. / Civilian

Ordinary digital receivers use analog mixers and conventional analog-to-digital converters. Thisthesis explores the possibility to build a receiver using an Intel Stratix 10 TX FPGA to sample asignal directly at its RF frequency. By band-limiting the RF signal, the transceivers can be used asPWM based analog-to-digital converters and sample the RF signals as a bit-stream. Filters andmixers could then be implemented in the FPGA to downconvert the RF signal to a complex digitalbaseband signal. This method was proven to work in theory but had drawbacks. The samplingmethod added a lot of distortion and the bandwidth was limited. The receiver could not beimplemented on the FPGA since the only connected transceivers could not be configured to receiveanalog signals. The other type of transceiver could probably be used but would have requiredanother model of the board where these were connected.

<p>In this thesis, a MISO wireless communication system having even transmitter antennas and a single receiver antenna is considered, where neither the transmitter nor the receiver knows channel state information. Particularly when the number of transmitter antennas is two, a novel concept called a uniquely factorable constellation pair (UFCP) is first proposed for the systematic design of a noncoherent full diversity collaborative unitary space-time block code by normalizing two Alamouti codes. It is proved that such a unitary UFCP code assures the unique identification of both channel coefficients and transmitted signals in a noise-free case as well as full diversity for the noncoherent maximum likelihood (ML) receiver in a noise case. To further improve error performance, an optimal unitary UFCP code is designed by appropriately and uniquely factorizing a pair of energy-efficient cross quadrature amplitude modulation (QAM) constellations to maximize the coding gain subject to a transmission bit rate constraint. After a deep investigation of the fractional coding gain function, a technical approach developed in this thesis to maximizing the coding gain is to carefully design an energy scale to compress the first three largest energy points in the corner of the QAM constellations in the denominator of the objective as well as carefully design a constellation triple forming two UFCPs, with one collaborating with the other two so as to make the accumulated minimum Euclidean distance along the two transmitter antennas in the numerator of the objective as large as possible and at the same time, to avoid as many corner points of the QAM constellations with the largest energy as possible to achieve the minimum of the numerator. In other words, the optimal coding gain is attained by intelligent constellations collaboration and efficient energy compression. Another contribution of this thesis is to generalize the design for the two transmitter antennas into that of the noncoherent system with any even number of transmitter antennas. Using the Alamouti coding scheme and the Toeplitz matrix structure, a novel noncoherent nonunitary space-time block code, which is called an Alamoutibased Toeplitz space-time block code, is proposed. By the fundamentals of Galois theory and algebraic number theory, two important properties on the two Alamouti codes generated from a pair of coprime phase shift keying (PSK) constellations, i.e., the uniqueness of factorization itself and the shift-invariant uniqueness of factorization, are first revealed and rigorously proved. Then, it is further shown that it is these two kinds of the unique factorizations that enable the unique blind identification of both the channel coefficients and the transmitted signals by only processing two block received signals as well as noncoherent full diversity with a generalized likelihood ratio test (GLRT) receiver. In addition, a full diversity unitary code design is also proposed by simply applying the QR decomposition to the full diversity nonunitary Alamoutibased Toeplitz space-time block code. Computer simulations demonstrate that error performance of both optimal unitary UFCP code and Alamouti-based Toeplitz code presented in this thesis outperform those of the differential code and the SNR-efficient training code, which is the best code in current literatures for the system.</p> / Master of Applied Science (MASc)