The problem of information-theoretic optimal resource allocation for the synchronous single-cell CDMA Gaussian multiple access channel is investigated. Several different cases are analyzed including: optimal sequence allocation without power control, optimal sequence allocation with optimal power control and optimal sequence allocation without power control with equal single user capacities. In order to simplify the mathematical description of the multiple access capacity region, a Cholesky decomposition characterization is introduced and utilized to find the optimal sequence allocation for equal single user capacities. The case of randomly chosen spreading sequences in a large system model, i.e. when number of users and processing gain increase without bounds while maintaining their ratio fixed, is also analyzed. Using this model, the performance of a conventional decision feedback receiver in flat fading channels is analyzed. A sequence allocation scheme that uses two sets of orthogonal users that can be decoded with a very simple decision feedback receiver is analyzed. It is shown that the spectral efficiency of this scheme is very close to the maximal possible. Finally, the issue of imperfect channel state information available at the receiver is discussed and the spectral efficiency loss compared to the perfect channel state information case is evaluated for the optimal multiuser receiver. / Graduate

In the design of the third generation of multi-media wireless networks, we are primarily concerned with the greatly varying information source rates, the quality requirements of various traffic types, the characteristics of the wireless environment, as well as the complexity and cost. Code Division Multiple Access (CDMA) cellular system is one of the most important candidates for supporting the future universal communications services. The objective of this research is to improve the capacity and the quality of service (QOS), as well as to reduce the complexity of cellular CDMA with integrated services, through improving or optimizing the design of system level operations. To facilitate the system performance and capacity evaluation, the multi-cell multi-user interference is analyzed through a new approach. The area averaged probability density function (PDF) of interference power from one active user is evaluated. The Gamma distribution is proposed for modelling the area averaged PDF of the interference power. An efficient method for evaluating system performance is developed. Differing from the Gaussian approximation, this method is very effective and accurate for both a large number and a small number of users. In this research, differing from the distance membership determination, the statistical effect of handoff is considered. The effects of soft handoff operation on multi-cell multi-user interference are analyzed. Membership statistics which are determined by soft handoff are investigated. A simple binomial model is proposed for modelling the distribution of the number of users belonging to a base station. Considering the call arrival statistics, user membership statistics and a finite number of channels available at a base station, we evaluate the call blocking/dropping rate. The minimum number of channels required at a base-station, which ensures a specified quality of service at a given capacity requirement, is determined. System capacity is further evaluated considering both outage probability limited by interference and call blocking/dropping rate limited by finite number of channels. A pilot assisted channel allocation method is proposed to minimize the number of channels required at a base station. Based on the analysis of a CDMA cellular system with a single traffic type, the design issues in developing a multi-media wireless networks are further discussed. The capacity of a CDMA cellular system with high quality requirements and mixed stream and packet types of traffic is assessed. The impact of the choice of a line rate (bit transmission rate through channel) on the system capacity is investigated. It is also shown that the power allocated to different types of traffic can be optimized to achieve maximum capacity. The optimum power allocation suggests that the power assignments to different traffic types are mainly determined by their quality requirements. / Graduate

Orientador: Leonardo de Souza Mendes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T09:20:09Z (GMT). No. of bitstreams: 1 Inocencio_AnaCarolinaGondim_M.pdf: 3226003 bytes, checksum: 6f0c024fb30ddcc6324cf74855f034f9 (MD5) Previous issue date: 2004 / Resumo: Este projeto de pesquisa desenvolveu um modelo de simulação sobre o ambiente Hydragyrum, baseado no padrão CDMA 2000. Para isto foi necessário estudar este padrão e os protocolos necessários para se desenvolver um modelo de rede, onde o comportamento deste padrão pudesse ser verificado. Foram criados cenários de simulação que possibilitassem a coleta de resultados, bem como que permitisse comprovar a validade do modelo desenvolvido. Ao longo das implementações realizadas, foi possível verificar como deve ser conduzido o estudo de alguma tecnologia, ou mesmo um padrão, para que deste possam ser abstraídas variáveis relevantes aos resultados que se pretende alcançar. Os resultados obtidos foram apresentados em forma de gráfico e demonstraram como o modelo se comporta. Para isto foram analisadas variações do atraso, throughput, atraso e taxa de perda. O modelo implementado servirá como base para futuros projetos de simulação que objetivem o desenvolvimento de modelos baseados em um ambiente sem fio / Abstract: In this research project it was developed a simulation model to the Hydragyrum environment, based on the standard CDMA 2000. For the development, it was necessary to study the standard and the protocols necessary to develop a network model, where the behavior of the standard could be verified. Simulation scenarios have been created to make possible the collection of results to prove the validity of the developed model. Along the implementations that were carried out, it was possible to verify how the study of some technology must be conducted so that one could abstract relevant variables from the results that one intends to obtain. The results were presented in graphical form and they demonstrate what is the model/behaviour. This was achieved throught the analysis of delay variations, throught, end-to-end delay out pecket loss ratio. The implemented model can be bases for future simulations that aim the development of models based on a wireless environment / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

In the past, the design of PC algorithms for CDMA systems has remained at the physical layer to compensate for slow and fast channel impairments (known as fast PC and slow PC). The TDMA/FDMA manages inter-cell interference at the beginning of the radio planning process. In SS technology, real time adaptive PC and power management algorithms would need to work coherently to ensure reliable multi-media services, and the need for this real-time hybrid structure of PC and power management has only been shown recently. The emphasis in this dissertation is therefore on the design of a QoS-based PC structure in W-CDMA applications, the ultimate goal being to evaluate the new QoS-based PC structure by means of a Monte Carlo computer simulation; a multi-user, multimedia W-CDMA simulation package. Before the design of the QoS-based PC structure, this dissertation examines and proposes a new power-sensitive model that addresses factors affecting the W-CDMA system capacity. Consequently, PC problems are put into a framework for various optimization criteria. Finally the design of a QoS-based PC structure by means of Monte Carlo computer simulation is described and evaluate. The first problem is closely related to the fact that W-CDMA is a design of a power management network architecture. The power management can co-exist in every layer of operation with different specific time scale and optimization objectives. The solution to this problem is therefore to introduce a general and mathematically tractable power-sensitive model to identify factors that influence the capacity of W-CDMA cellular systems and then articulate the general power sensitive model to form a PC framework aimed at finding a common systematic treatment for different schools of thought on PC algorithms. This dissertation proves the benefits of layered PC operation for guaranteed QoS transmission and also shows that this research coincides with and extend the literature on PC management by categorizing PC algorithms according to various optimization objectives and time scales. The second problem is to evaluate the new QoS-based PC structure in a channel coded and RAKE combining uplink UMTSIUTRA cellular environment using the Monte Carlo simulation package. The UMTS radio channel models are described in terms of frequency-selective Rayleigh fading: Indoor-Office, Outdoor and Pedestrian and Vehicular environments. The package is simulated in Matlab. The influence of the number of multipath components, of Doppler Spread, the number of received antenna, the coding scheme and multi-access interference are discussed in the dissertation. The performance evaluation criteria for utility-based PC structures are Bit-Error-Rate (BER) performance (robustness), outage performance (tracking ability) and rate of convergence. The first test shows that the new proposed unbalanced step-size closed-loop FPC schemes can provide better SINR tracking ability and better BER performance than conventional balanced step-size PC schemes. The unbalanced FPCs have better PC error distribution in all scenarios. The second test shows that the proposed BER-prediction distributed OPC schemes can provide better BER tracking ability. This scheme converges iteratively to an optimal SINR level under current network settings with no excessive interference to other active users. / Dissertation (M Eng (Electronics))--University of Pretoria, 2006. / Electrical, Electronic and Computer Engineering / Unrestricted

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Parallel interference cancellation for DS-CDMA has been shown to suffer from biased amplitude estimates if a matched-filter estimator is used. The bias magnitude is proportional to the number of interfering users. For heavy system loads, the bias has been shown to adversely effect the accuracy of the interference cancellation process, thereby impairing BER after cancellation. Empirical simulation work has demonstrated that weighting down interference estimates can improve BER performance. This thesis substantiates these BER improvements by modelling and analyzing a soft interference cancellation technique which mitigates the effects of the bias by minimizing BER after cancellation in a bit-synchronous parallel interference cancellation CDMA receiver. We analyze system decision metrics with down-scaled interference estimates and determine both the mean and variance of the biased decision statistics. From these two metric moments, system BER is evaluated, and the optimal interference scaling function which minimizes BER is derived. We demonstrate BER performance enhancements by simulating this soft interference cancellation technique in systems under perfect power control and in the near-far situation. We further discuss the applicability of the results to asynchronous systems. / Master of Science

This thesis proposes a multistage RAKE receiver for use at the base station of a Code Division Multiple Access (CDMA) cellular communications system. This receiver combines the interference rejection capability of multiuser receivers with the robust performance of a RAKE receiver in the presence of multipath interference. Unlike previous multiuser receiver designs, this multistage RAKE receiver requires no a priori information about the time-vary multipath radio channel. The thesis presents a mathematical description of the multistage receiver, and a software simulation of the receiver performance. A wide range of channel models are considered which include the effects of Gaussian noise, multipath propagation, imperfect power control and multiple access interference for the reverse link CDMA channel. Under a wide range of conditions, the multistage RAKE receiver is able to support two to three times as many users as a conventional single stage RAKE receiver. The receiver is also shown to be robust to the near-far problem. / Master of Science

It is desirable to develop a universal digital receiver which is capable of operating with many different wireless communication systems. Time Dependent Adaptive Filter (TDAF) Processing represents an effective approach for CDMA interference rejection. This technique is especially appropriate at the mobile receiver where there is little prior knowledge of the spreading codes of the other users. This thesis presents enhanced forms of the Time Dependent Adaptive Filter (TDAF), which is an optimal periodically time-varying adaptive filter. It is able to fully exploit the cyclostationarity and spectral correlation in certain DS-SS signals. It is shown how multiple AVM service providers can exist in adjacent channels within the ISM band. It is demonstrated that using the realistic channel models the TDAF can provide substantial improvement in interference rejection over the conventional correlation receiver. Computationally efficient TDAF structures have been also proposed to handle the case of different code repeat intervals for different systems. Results of CDMA overlay system simulation have shown that TDAF processing can achieve tremendous gain in narrowband interference rejection compared to notch/matched filter processing. An input signal which has 45 dB narrowband interference-to-signal power ratio (J/S), the SIR of the TDAF processed output signal can be 20 dB, a 65 dB improvement. The use of TDAF processing and a spectral shaping filter can minimize the impact of adjacent channel interference. Even in an environment which has a 30 dB adjacent channel J/S, the SIR at output is demonstrate to be a 50 dB improvement. System performance shows little degradation by adjacent channel and narrowband interference. / Master of Science

Our society is undergoing a wireless revolution in which there is a rapidly increasing demand for personal communication services (PCS). Several alternate technologies have been proposed to meet this demand, including a 1.25 MHz CDMA system. It is important to provide system designers with tools to accurately predict system performance. Analytical techniques are useful for providing general information on system performance, but may not fully capture the complexities of the mobile radio channel needed to accurately predict the performance of complex system designs. This thesis presents a novel simulation technique in which a CDMA system is modeled by software, but the channel impulse response model is derived from actual measurements. This thesis describes a bit error simulation tool for a 1.25 MHz bandwidth CDMA system. The simulator incorporates measurement-based channel impulse response data with the simulated CDMA system. Bit error rate for COMA is simulated under a variety of actual channel conditions, including heavy urban, urban, suburban and rural environments. Simulation results for both 915 MHz and 1920 MHz are presented. Vertical and circular antenna polarization are compared. In the simulation, a RAKE receiver is implemented, the advantage of this RAKE receiver implementation is demonstrated by comparison to a single correlation receiver. Results for outage probability are also presented. / Master of Science