This thesis aims at proposing all the possible enhancements for the Multi-Resolution Frequency-Domain ParFlow (MR-FDPF) model. As a deterministic radio propagation model, the MR-FDPF model possesses the property of a high level of accuracy, but it also suffers from some common limitations of deterministic models. For instance, realistic radio channels are not deterministic but a kind of random processes due to, e.g. moving people or moving objects, thus they can not be completely described by a purely deterministic model. In this thesis, a semi-deterministic model is proposed based on the deterministic MR-FDPF model which introduces a stochastic part to take into account the randomness of realistic radio channels. The deterministic part of the semi-deterministic model is the mean path loss, and the stochastic part comes from the shadow fading and the small scale fading. Besides, many radio propagation simulators provide only the mean power predictions. However, only mean power is not enough to fully describe the behavior of radio channels. It has been shown that fading has also an important impact on the radio system performance. Thus, a fine radio propagation simulator should also be able to provide the fading information, and then an accurate Bit Error Rate (BER) prediction can be achieved. In this thesis, the fading information is extracted based on the MR-FDPF model and then a realistic BER is predicted. Finally, the realistic prediction of the BER allows the implementation of the adaptive modulation scheme. This has been done in the thesis for three systems, the Single-Input Single-Output (SISO) systems, the Maximum Ratio Combining (MRC) diversity systems and the wideband Orthogonal Frequency-Division Multiplexing (OFDM) systems.

Cooperative relaying is a promising diversity achieving technique to provide reliable transmission, high throughput and extensive coverage for wireless networks in a variety of applications. Two-way relaying is a spectrally efficient protocol, providing one solution to overcome the half-duplex loss in one-way relay channels. Moreover, incorporating the multiple-input-multiple-output (MIMO) technology can further improve the spectral efficiency and diversity gain. A lot of related work has been performed on the two-way relay network (TWRN), but most of them assume perfect channel state information (CSI). In a realistic scenario, however, the channel is estimated and the estimation error exists. So in this thesis, we explicitly take into account the CSI error, and investigate its impact on the performance of amplify-and-forward (AF) TWRN where either multiple distributed single-antenna relays or a single multiple-antenna relay station is exploited. For the distributed relay network, we consider imperfect self-interference cancellation at both sources that exchange information with the help of multiple relays, and maximal ratio combining (MRC) is then applied to improve the decision statistics under imperfect signal detection. The system performance degradation in terms of outage probability and average bit-error rate (BER) are analyzed, as well as their asymptotic trend. To further improve the spectral efficiency while maintain the spatial diversity, we utilize the maximum minimum (Max-Min) relay selection (RS), and examine the impact of imperfect CSI on this single RS scheme. To mitigate the negative effect of imperfect CSI, we resort to adaptive power allocation (PA) by minimizing either the outage probability or the average BER, which can be cast as a Geometric Programming (GP) problem. Numerical results verify the correctness of our analysis and show that the adaptive PA scheme outperforms the equal PA scheme under the aggregated effect of imperfect CSI. When employing a single MIMO relay, the problem of robust MIMO relay design has been dealt with by considering the fact that only imperfect CSI is available. We design the MIMO relay based upon the CSI estimates, where the estimation errors are included to attain the robust design under the worst-case philosophy. The optimization problem corresponding to the robust MIMO relay design is shown to be nonconvex. This motivates the pursuit of semidefinite relaxation (SDR) coupled with the randomization technique to obtain computationally efficient high-quality approximate solutions. Numerical simulations compare the proposed MIMO relay with the existing nonrobust method, and therefore validate its robustness against the channel uncertainty. / Graduate

Hydrocarbon exploration, global navigation satellite systems, computed tomography, and aircraft avionics are just a few examples of applications that require system operation at an ambient temperature, pressure, or radiation level outside the range covered by military specifications. The electronics employed in these applications are known as "extreme environment electronics." On account of the increased cost resulting from both process modifications and the use of exotic substrate materials, only a handful of semiconductor foundries have specialized in the production of extreme environment electronics. Protection of these electronic systems in an extreme environment may be attained by encapsulating sensitive circuits in a controlled environment, which provides isolation from the hostile ambient, often at a significant cost and performance penalty. In a significant departure from this traditional approach, system designers have begun to use commercial off-the-shelf technology platforms with built in mitigation techniques for extreme environment applications. Such an approach simultaneously leverages the state of the art in technology performance with significant savings in project cost. Silicon-germanium is one such commercial technology platform that demonstrates potential for deployment into extreme environment applications as a result of its excellent performance at cryogenic temperatures, remarkable tolerance to radiation-induced degradation, and monolithic integration with silicon-based manufacturing. In this dissertation the radiation response of silicon-germanium technology is investigated, and novel transistor-level layout-based techniques are implemented to improve the radiation tolerance of HBT digital logic.

To support video communication over mobile environments has been one of the objectives of many engineers of telecommunication networks and it has become a basic requirement of a third generation of mobile communication systems. This dissertation explores the possibility of optimizing the utilization of shared scarce radio channels for live video transmission over a GSM (Global System for Mobile telecommunications) network and realizing error resilient video communication in unfavorable channel conditions, especially in mobile radio channels. The main contribution describes the adoption of a SEC (Second Error Correction) approach using ECC (Error Correction Coding) based on a Punctured Convolutional Coding scheme, to cope with residual errors at the application layer and enhance the error resilience of a compressed video bitstream. The approach is developed further for improved performance in different circumstances, with some additional enhancements involving Intra Frame Relay and Interleaving, and the combination of the approach with Packetization. Simulation results of applying the various techniques to test video sequences Akiyo and Salesman are presented and analyzed for performance comparisons with conventional video coding standard. The proposed approach shows consistent improvements under these conditions. For instance, to cope with random residual errors, the simulation results show that when the residual BER (Bit Error Rate) reaches 10-4, the video output reconstructed from a video bitstream protected using the standard resynchronization approach is of unacceptable quality, while the proposed scheme can deliver a video output which is absolutely error free in a more efficient way. When the residual BER reaches 10-3, the standard approach fails to deliver a recognizable video output, while the SEC scheme can still correct all the residual errors with modest bit rate increase. In bursty residual error conditions, the proposed scheme also outperforms the resynchronization approach. Future works to extend the scope and applicability of the research are suggested in the last chapter of the thesis.

Over the last few years, wireless cellular communications has experienced rapid growth in the demand for provision of high data rate wireless multimedia services. This fact motivates the need to find ways to improve the spectrum efficiency of wireless communication systems. Smart or adaptive antennas have emerged as a promising technology to enhance the spectrum efficiency of present and future wireless communications systems by exploiting the spatial domain. The aim of this thesis is to investigate smart antenna applications for Direct Sequence Code Division Multiple Access (DS-CDMA) systems. CDMA is chosen as the platform for this thesis work since it has been adopted as the air-interface technology by the Third Generation (3G) wireless communication systems. The main role of smart antennas is to mitigate Multiple Access Interference (MAI) by beamforming (i.e. spatial filtering) operation. Therefore, irrespective of a particular wireless communication system, it is important to consider whether a chosen array configuration will enable optimal performance. In this thesis an initial assessment is carried out considering linear and circular array of dipoles, that can be part of a base station antenna system. A unified and systematic approach is proposed to analyse and compare the interference rejection capabilities of the two array configurations in terms of the Signal to Interference Ratio (SIR) at the array output. The theoretical framework is then extended to include the effect of mutual coupling, which is modelled using both analytical and simulation methods. Results show that when the performance is averaged over all angles of arrival and mutual coupling is negligible, linear arrays show similar performance as circular arrays. Thus in the remaining part of this thesis, only linear arrays are considered. In order to properly evaluate the performance of smart antenna systems, a realistic channel model is required that takes into account both temporal and spatial propagation characteristics of the wireless channel. In this regard, a novel parameterized physical channel model is proposed in this thesis. The new model incorporates parameters such as user mobility, azimuth angle of arrival, angle spread and Doppler frequency, which have critical influence on the performance of smart antennas. A mathematical formulation of the channel model is presented and the proposed model is implemented in software using Matlab. The statistics of the simulated channels are analysed and compared with theory to confirm that the proposed model can accurately simulate Rayleigh and Rician fading characteristics. To assist system planners in the design and deployment of smart antennas, it is important to develop robust analytical tools to assess the impact of smart antennas on cellular systems. In this thesis an analytical model is presented for evaluating the Bit Error Rate (BER) of a DS-CDMA system employing an array antenna operating in Rayleigh and Rician fading environments. The DS-CDMA system is assumed to employ noncoherent M-ary orthogonal modulation, which is relevant to IS-95 CDMA and cdma2000. Using the analytical model, an expression of the Signal to Interference plus Noise Ratio (SINR) at the output of the smart antenna receiver is derived, which allows the BER to be evaluated using a closed-form expression. The proposed model is shown to provide good agreement with the (computationally intensive) Monte Carlo simulation results and can be used to rapidly calculate the system performance for suburban and urban fading environments. In addition to MAI, the performance of CDMA systems is limited by fast fading. In this context, a hybrid scheme of beamforming and diversity called Hierarchical Beamforming (HBF) is investigated in this thesis to jointly combat MAI and fading. The main idea behind HBF is to divide the antenna elements into widely separated groups to form subbeamforming arrays. The performance of a hierarchical beamforming receiver, applied to an IS-95 CDMA system, is compared with smart antenna (conventional beamforming) receiver and the effect of varying the system and channel parameters is studied. The simulation results show that the performance of hierarchical beamforming is sensitive to the operating conditions, especially the value of the azimuth angle spread. The work presented in this thesis has been published in part in several journals and refereed conference papers, which reflects the originality and significance of the thesis contributions.

Over the last few years, wireless cellular communications has experienced rapid growth in the demand for provision of high data rate wireless multimedia services. This fact motivates the need to find ways to improve the spectrum efficiency of wireless communication systems. Smart or adaptive antennas have emerged as a promising technology to enhance the spectrum efficiency of present and future wireless communications systems by exploiting the spatial domain. The aim of this thesis is to investigate smart antenna applications for Direct Sequence Code Division Multiple Access (DS-CDMA) systems. CDMA is chosen as the platform for this thesis work since it has been adopted as the air-interface technology by the Third Generation (3G) wireless communication systems. The main role of smart antennas is to mitigate Multiple Access Interference (MAI) by beamforming (i.e. spatial filtering) operation. Therefore, irrespective of a particular wireless communication system, it is important to consider whether a chosen array configuration will enable optimal performance. In this thesis an initial assessment is carried out considering linear and circular array of dipoles, that can be part of a base station antenna system. A unified and systematic approach is proposed to analyse and compare the interference rejection capabilities of the two array configurations in terms of the Signal to Interference Ratio (SIR) at the array output. The theoretical framework is then extended to include the effect of mutual coupling, which is modelled using both analytical and simulation methods. Results show that when the performance is averaged over all angles of arrival and mutual coupling is negligible, linear arrays show similar performance as circular arrays. Thus in the remaining part of this thesis, only linear arrays are considered. In order to properly evaluate the performance of smart antenna systems, a realistic channel model is required that takes into account both temporal and spatial propagation characteristics of the wireless channel. In this regard, a novel parameterized physical channel model is proposed in this thesis. The new model incorporates parameters such as user mobility, azimuth angle of arrival, angle spread and Doppler frequency, which have critical influence on the performance of smart antennas. A mathematical formulation of the channel model is presented and the proposed model is implemented in software using Matlab. The statistics of the simulated channels are analysed and compared with theory to confirm that the proposed model can accurately simulate Rayleigh and Rician fading characteristics. To assist system planners in the design and deployment of smart antennas, it is important to develop robust analytical tools to assess the impact of smart antennas on cellular systems. In this thesis an analytical model is presented for evaluating the Bit Error Rate (BER) of a DS-CDMA system employing an array antenna operating in Rayleigh and Rician fading environments. The DS-CDMA system is assumed to employ noncoherent M-ary orthogonal modulation, which is relevant to IS-95 CDMA and cdma2000. Using the analytical model, an expression of the Signal to Interference plus Noise Ratio (SINR) at the output of the smart antenna receiver is derived, which allows the BER to be evaluated using a closed-form expression. The proposed model is shown to provide good agreement with the (computationally intensive) Monte Carlo simulation results and can be used to rapidly calculate the system performance for suburban and urban fading environments. In addition to MAI, the performance of CDMA systems is limited by fast fading. In this context, a hybrid scheme of beamforming and diversity called Hierarchical Beamforming (HBF) is investigated in this thesis to jointly combat MAI and fading. The main idea behind HBF is to divide the antenna elements into widely separated groups to form subbeamforming arrays. The performance of a hierarchical beamforming receiver, applied to an IS-95 CDMA system, is compared with smart antenna (conventional beamforming) receiver and the effect of varying the system and channel parameters is studied. The simulation results show that the performance of hierarchical beamforming is sensitive to the operating conditions, especially the value of the azimuth angle spread. The work presented in this thesis has been published in part in several journals and refereed conference papers, which reflects the originality and significance of the thesis contributions.

Made available in DSpace on 2016-04-18T21:39:47Z (GMT). No. of bitstreams: 4 Erik Aceiro Antonio1.pdf: 1548083 bytes, checksum: 089690da04ba664ec23f802cb3975826 (MD5) Erik Aceiro Antonio2.pdf: 1618157 bytes, checksum: efefcd4d6d658d457615e8757d4175d8 (MD5) Erik Aceiro Antonio3.pdf: 2722615 bytes, checksum: a3f70f5fd3c8b07408a62f1d5a6cfbc2 (MD5) Erik Aceiro Antonio4.pdf: 1214557 bytes, checksum: 8bf6858d70baeb72941ce7c5cc104437 (MD5) Previous issue date: 2008-06-30 / The advent of the Internet and the development of Information and Communication Technologies (ICT s)generated new spaces for communication and collaboration between groups of people in geographically distinct regions. The association of Web technology with instrument automation and control by computer has made possible the development of the so called Remote Laboratories or WebLabs - distributed environments that allow to access and control experiments remotely through a network or the Internet in real time and with the sensation of presence. In this work, a WebLab was developed for the study and caracterization of a WDM (Wave Division Multiplexing) system, aiming to support and complement activities in faceto-face and distance courses on Optical Communications. Drivers and graphic user interfaces (GUI s) were developed with the software LabVIEW for control and data acquisition of instruments used in a remote experiment to measure the basic features of a WDM system. An application was also developed with the software VPI for the numerical simulation of Bit Error Rate (BER) measurements. This work is part of the activities related to the participation of the Mackenzie Photonics Laboratory in the KyaTera Project of FAPESP s TIDIA Program. / O advento da Internet e o desenvolvimento das Tecnologias da Informação e Comunicação (TIC s) geraram novos espaços para a comunicação e colaboração entre grupos de pessoas localizadas em regiões geograficamente distintas. A associação da tecnologiaWeb com a automação e controle de instrumentos por computador tornou possível o desenvolvimento dos chamados Laboratórios Remotos ou WebLabs - ambientes distribuídos que permitem o acesso e controle remoto de experimentos através de uma rede de comunicação ou da Internet em tempo real e com sensação de presença. Neste trabalho, foi desenvolvido um WebLab para estudo e caracterização de um sistema WDM (Wave Division Multiplexing), destinado a apoiar e complementar atividades em cursos de Comunicações Ópticas presenciais e a distância. Foram desenvolvidos drivers e interfaces gráficas de usuário (GUI s) com o software LabVIEW para o controle e aquisição de dados dos instrumentos utilizados em um experimento remoto de medida das características básicas de um sistema WDM. Também foi desenvolvido um aplicativo com o software VPI que permite simular a medida da Taxa de Erro de Bit (BER) do sistema. Este trabalho é parte das atividades relacionadas à participação do Laboratório de Fotônica Mackenzie no Projeto KyaTera do Programa TIDIA da FAPESP.

Ce travail vise la modélisation au niveau système, en langage SystemC-AMS, et la simulation d'un émetteur-récepteur au standard Bluetooth Low Energy (BLE). L'objectif est d'analyser la relation entre les performances, en termes de BER et la consommation d'énergie du transceiver. Le temps de simulation d’un tel système, à partir de cas d’étude (use case) réaliste, est un facteur clé pour le développement d’une telle plateforme. De plus, afin d’obtenir des résultats de simulation le plus précis possible, les modèles « haut niveau » doivent être raffinés à partir de modèles plus bas niveau où de mesure. L'approche dite Meet-in-the-Middle, associée à la méthode de modélisation équivalente en Bande Base (BBE, BaseBand Equivalent), a été choisie pour atteindre les deux conditions requises, à savoir temps de simulation « faible » et précision des résultats. Une simulation globale d'un système de BLE est obtenue en intégrant le modèle de l'émetteur-récepteur dans une plateforme existante développée en SystemC-TLM. La simulation est basée sur un système de communication de deux dispositifs BLE, en utilisant différents scénarios (différents cas d'utilisation de BLE). Dans un premier temps nous avons modélisé et validé chaque bloc d’un transceiver BT. Devant le temps de simulation prohibitif, les blocs RF sont réécrits en utilisant la méthodologie BB, puis raffinés afin de prendre en compte les non-linéarités qui vont impacter le couple consommation, BER. Chaque circuit (chaque modèle) est vérifié séparément, puis une première simulation système (point à point entre un émetteur et un récepteur) est effectuée / This work aims at system-level modelling a defined transceiver for Bluetooth Low energy (BLE) system using SystemC-AMS. The goal is to analyze the relationship between the transceiver performance and the accurate energy consumption. This requires the transceiver model contains system-level simulation speed and the low-level design block power consumption and other RF specifications. The Meet-in-the-Middle approach and the Baseband Equivalent method are chosen to achieve the two requirements above. A global simulation of a complete BLE system is achieved by integrating the transceiver model into a SystemC-TLM described BLE system model which contains the higher-than-PHY levels. The simulation is based on a two BLE devices communication system and is run with different BLE use cases. The transceiver Bit-Error-Rate and the energy estimation are obtained at the end of the simulation. First, we modelled and validated each block of a BT transceiver. In front of the prohibitive simulation time, the RF blocks are rewritten by using the BBE methodology, and then refined in order to take into account the non-linearities, which are going to impact the couple consumption, BER. Each circuit (each model) is separately verified, and then a first BLE system simulation (point-to-point between a transmitter and a receiver) has been executed. Finally, the BER is finally estimated. This platform fulfills our expectations, the simulation time is suitable and the results have been validated with the circuit measurement offered by Riviera Waves Company. Finally, two versions of the same transceiver architecture are modelled, simulated and compared

Explosive growth in wireless technology caused by development in digital and RF circuit fabrications put some serious challenges on wireless system designers and link budget planning. Low transmit power, system coverage and capacity, high data rates, spatial diversity and quality of services (QOS) are the key factors in future wireless communication system that made it attractive. Dual-hop relaying is the promising underlying technique for future wireless communication to address such dilemmas. Based on dual-hop relaying this thesis addresses two scenarios. In the first case the system model employs dual-hop amplify and forward (AF) multiple input multiple output (MIMO) relay channels with transmit and receive antenna selection over independent Rayleigh fading channels where source and destination contain multiple antennas and communicate with each other with help of single antenna relay. It is assumed that the source and destination has perfect knowledge of channel state information (CSI). Our analysis shows that full spatial diversity order can be achieved with minimum number of antennas at source and destination i.e. min{N_s N_d }. In the second case the performance analysis of dual-hop amplify and forward (AF) multiple relay cooperative diversity network with best relay selection schemes over Rayleigh fading channels is investigated where the source and destination communicate with each other through direct and indirect links. Only the performance of best relay is investigated which participates in the transmission alone. The relay node that achieves highest SNR at the destination is selected as a best relay. Once again our analysis shows that full diversity order can be achieved with single relay with fewer resources compare to the regular cooperative diversity system. / Muhammad Adeel Islam 0046 700 412 343

Code Division Multiple Access (CDMA) is the technology used in all third generation cellular communications networks, and it is a promising candidate for the definition of fourth generation standards. The wireless mobile channel is usually frequency-selective causing interference among the users in one CDMA cell. Multiuser Transmission (MUT) algorithms for the downlink can increase the number of supportable users per cell, or decrease the necessary transmit power to guarantee a certain quality-of-service. Transmitter-based algorithms exploiting the channel knowledge in the transmitter are also motivated by information theoretic results like the Writing-on-Dirty-Paper theorem. The signal-to-noise ratio (SNR) is a reasonable performance criterion for noise-dominated scenarios. Using linear filters in the transmitter and the receiver, the SNR can be maximized with the proposed Eigenprecoder. Using multiple transmit and receive antennas, the performance can be significantly improved. The Generalized Selection Combining (GSC) MIMO Eigenprecoder concept enables reduced complexity transceivers. Methods eliminating the interference completely or minimizing the mean squared error exist for both the transmitter and the receiver. The maximum likelihood sequence detector in the receiver minimizes the bit error rate (BER), but it has no direct transmitter counterpart. The proposed Minimum Bit Error Rate Multiuser Transmission (TxMinBer) minimizes the BER at the detectors by transmit signal processing. This nonlinear approach uses the knowledge of the transmit data symbols and the wireless channel to calculate a transmit signal optimizing the BER with a transmit power constraint by nonlinear optimization methods like sequential quadratic programming (SQP). The performance of linear and nonlinear MUT algorithms with linear receivers is compared at the example of the TD-SCDMA standard. The interference problem can be solved with all MUT algorithms, but the TxMinBer approach requires less transmit power to support a certain number of users. The high computational complexity of MUT algorithms is also an important issue for their practical real-time application. The exploitation of structural properties of the system matrix reduces the complexity of the linear MUT mthods significantly. Several efficient methods to invert the ystem matrix are shown and compared. Proposals to reduce the omplexity of the Minimum Bit Error Rate Multiuser Transmission mehod are made, including a method avoiding the constraint by pase-only optimization. The complexity of the nonlinear methods i still some magnitudes higher than that of the linear MUT lgorithms, but further research on this topic and the increasing processing power of integrated circuits will eventually allow to exploit their better performance. / Der codegeteilte Mehrfachzugriff (CDMA) wird bei allen zellularen Mobilfunksystemen der dritten Generation verwendet und ist ein aussichtsreicher Kandidat für zukünftige Technologien. Die Netzkapazität, also die Anzahl der Nutzer je Funkzelle, ist durch auftretende Interferenzen zwischen den Nutzern begrenzt. Für die Aufwärtsstrecke von den mobilen Endgeräten zur Basisstation können die Interferenzen durch Verfahren der Mehrnutzerdetektion im Empfänger verringert werden. Für die Abwärtsstrecke, die höhere Datenraten bei Multimedia-Anwendungen transportiert, kann das Sendesignal im Sender so vorverzerrt werden, dass der Einfluß der Interferenzen minimiert wird. Die informationstheoretische Motivation liefert dazu das Writing-on-Dirty-Paper Theorem. Das Signal-zu-Rausch-Verhältnis ist ein geeignetes Kriterium für die Performanz in rauschdominierten Szenarien. Mit Sende- und Empfangsfiltern kann das SNR durch den vorgeschlagenen Eigenprecoder maximiert werden. Durch den Einsatz von Mehrfachantennen im Sender und Empfänger kann die Performanz signifikant erhöht werden. Mit dem Generalized Selection MIMO Eigenprecoder können Transceiver mit reduzierter Komplexität ermöglicht werden. Sowohl für den Empfänger als auch für den Sender existieren Methoden, die Interferenzen vollständig zu eliminieren, oder den mittleren quadratischen Fehler zu minimieren. Der Maximum-Likelihood-Empfänger minimiert die Bitfehlerwahrscheinlichkeit (BER), hat jedoch kein entsprechendes Gegenstück im Sender. Die in dieser Arbeit vorgeschlagene Minimum Bit Error Rate Multiuser Transmission (TxMinBer) minimiert die BER am Detektor durch Sendesignalverarbeitung. Dieses nichtlineare Verfahren nutzt die Kenntnis der Datensymbole und des Mobilfunkkanals, um ein Sendesignal zu generieren, dass die BER unter Berücksichtigung einer Sendeleistungsnebenbedingung minimiert. Dabei werden nichtlineare Optimierungsverfahren wie Sequentielle Quadratische Programmierung (SQP) verwendet. Die Performanz linearer und nichtlinearer MUT-Verfahren MUT-Algorithmen mit linearen Empfängern wird am Beispiel des TD-SCDMA-Standards verglichen. Das Problem der Interferenzen kann mit allen untersuchten Verfahren gelöst werden, die TxMinBer-Methode benötigt jedoch die geringste Sendeleistung, um eine bestimmt Anzahl von Nutzern zu unterstützen. Die hohe Rechenkomplexität der MUT-Algorithmen ist ein wichtiges Problem bei der Implementierung in Real-Zeit-Systemen. Durch die Ausnutzung von Struktureigenschaften der Systemmatrizen kann die Komplexität der linearen MUT-Verfahren signifikant reduziert werden. Verschiedene Verfahren zur Invertierung der Systemmatrizen werden aufgezeigt und verglichen. Es werden Vorschläge gemacht, die Komplexität der Minimum Bit Error Rate Multiuser Transmission zu reduzieren, u.a. durch Vermeidung der Sendeleistungsnebenbedingung durch eine Beschränkung der Optimierung auf die Phasen des Sendesignalvektors. Die Komplexität der nichtlinearen Methoden ist um einige Größenordungen höher als die der linearen Verfahren. Weitere Forschungsanstrengungen an diesem Thema sowie die wachsende Rechenleistung von integrierten Halbleitern werden künftig die Ausnutzung der besseren Leistungsfähigkeit der nichtlinearen MUT-Verfahren erlauben.