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Estimação de canais MIMO variantes no tempo usando filtros de Kalman; Time-varying MIMO channel estimation using Kalman filters

Murilo Bellezoni Loiola
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 18/05/2009 PT
Relevância na Pesquisa
56.47%
Neste trabalho utilizamos filtros de Kalman para estimar canais de comunicação sem fio variantes no tempo em sistemas com múltiplas entradas e múltiplas saídas. Primeiramente, propusemos um estimador ótimo (no sentido de minimização do erro quadrático médio de estimação) para rastrear canais planos em sistemas utilizando códigos espaço-temporais ortogonais por blocos. Graças à ortogonalidade destes códigos, foi possível simplificar as equações do filtro de Kalman. Mostramos que as estimativas fornecidas pelo estimador proposto correspondem a somas ponderadas de estimativas instantâneas de máxima verossimilhança do canal. Ainda para este sistema, propusemos um filtro de Kalman em estado estacionário para modulações de módulo constante. O filtro em estado estacionário tem desempenho semelhante ao do filtro de Kalman ótimo, embora necessite apenas de uma fração dos cálculos envolvidos. Em seguida, propusemos um receptor baseado no filtro de Kalman estendido para realizar conjuntamente as tarefas de estimação de canais seletivos em freqüência e detecção de sinais em sistemas com múltiplas entradas, múltiplas saídas (MIMO, do inglês multiple-input, multiple-output) e multiplexação espacial. Por fim...

Um estudo sobre a abordagem de estimação e detecção conjuntas em sistemas MIMO submetidos a canais sem-fio seletivos em frequência e variantes no tempo; A study about the approach for joint channel estimation and data detection in MIMO wireless systems subjected to frequency selective and time-varying wireless channels

Raquel Guerreiro Machado
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 31/05/2010 PT
Relevância na Pesquisa
56.47%
Na prática, quando um sistema faz uso de altas taxas de transmissão, os símbolos transmitidos são sujeitos a interferência inter-simbólica (ISI). Além disso, se existe movimento relativo entre o transmissor e receptor, tal movimentação provoca mudança no perfil do canal ao longo do tempo. Portanto, para que seja possível a implementação de sistemas sem-fio modernos que usem múltiplas antenas de transmissão e/ou recepção, é essencial que sejam desenvolvidos métodos que lidem com tais condições. Nesse contexto, este trabalho estuda a utilização da abordagem de estimação dos coeficientes de um canal MIMO com interferência inter-simbólica e variante no tempo e detecção de símbolos de forma conjunta. Com base na modelagem da dinâmica temporal dos coeficientes do canal e dos símbolos transmitidos, um vetor de estados é definido contendo ambas informações levando a uma não-linearidade na equação de observação do sistema proposto. Uma solução analítica para o problema de filtragem não-linear é então apresentada, bem como dois algoritmos que propõem soluções sub-ótimas. Por fim, simulações numéricas comprovam a superioridade da abordagem conjunta e mostram os desempenho dos dois algoritmos propostos para a solução do problema de estimação e detecção conjuntas em sistemas MIMO submetidos a canais sem-fio seletivos em frequência e variantes no tempo; In practice...

Um estudo sobre a robustez de técnicas de processamento de sinais em sistemas MIMO; A study regarding robustness of signal processing techniques in MIMO systems

Glauco Cesar Crystal Pereira Simões
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 17/06/2011 PT
Relevância na Pesquisa
56.35%
Sistemas de comunicação sem fio com múltiplas antenas atingem altas taxas de transmissão de dados e boa robustez ao desvanecimento do canal de comunicação quando os sinais que trafegam pelo sistema são processados conjuntamente em sua transmissão e/ou em sua recepção. Em geral, as técnicas de detecção de sinais assumem o conhecimento perfeito do canal de comunicações, tanto no transmissor, quanto no receptor do sistema, uma hipótese que nem sempre é válida. Neste sentido, é importante analisar o desempenho do sistema frente a erros de estimação do canal de comunicações. Neste trabalho, esta análise é feita através da comparação do cálculo da probabilidade de erro de símbolos com as taxas de erro de símbolos obtidas através de simulação computacional para o detector zero-forcing, assumindo a utilização dos critérios de detecção linear e através da aplicação da técnica de cancelamento sucessivo de interferências; Multiple antenna wireless communication systems achieve high data transmission rates and good robustness to channel fading when signals traveling through the system are jointly processed in their transmitters and/ or receivers. In general, signal detection techniques assume perfect knowledge of the channel state information...

Minimum Codebook Size to achieve Maximal Diversity Order for RVQ based MIMO Systems

Castanheira, Daniel; Silva, Adão; Gameiro, Atílio
Fonte: Institute of Electrical and Electronics Engineers (IEEE) Publicador: Institute of Electrical and Electronics Engineers (IEEE)
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.25%
Multiple antenna systems provide both capacity and diversity gains relatively to single antenna based networks. These gains rely heavily on the availability of channel state information. In this manuscript we assume that the receiver has accurate channel information, which is quantized and fed back to the transmitter. Sufficient conditions for the feedback rate are provided that guarantee no loss of diversity due to channel quantization. Considering a K × M MIMO system, we show that to achieve a diversity of D = M – K + 1 which is the maximum allowable, a feedback channel with rate of log2(1 + D) bits per channel use is enough.

An FPGA Based Rapid Prototyping Platform for MIMO Systems

Murphy, Patrick; Lou, Feifei; Sabharwal, Ashutosh; Frantz, Patrick; Murphy, Patrick; Lou, Feifei; Sabharwal, Ashutosh; Frantz, Patrick
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Conference paper
ENG
Relevância na Pesquisa
56.42%
Conference Paper; There exists a seemingly limitless demand for wireless communications systems capable of higher datarates with lower power consumption. While the demand for improvement in these systems seems limitless, the spectrum allocated for providing such services is undeniably restricted. There is a great deal of research directed at solving the problem of providing more wireless communications capabilities without any increase in allocated spectrum. One significant result of this research has been the development of algorithms targeted at transmitters and receivers equipped with multiple antennas, often described as multiple-input multiple-output (MIMO) systems. We describe in this paper a FPGA-based platform designed to explore MIMO algorithms and architectures in real hardware. This system utilizes Xilinx?s System Generator for DSP, a Simulink blockset designed to allow both PC-based simulation and FPGA implementation of DSP designs. MIMO algorithms implemented in System Generator are targeted to FPGA systems connected to 2.4 GHz spread spectrum radios. These radios are interconnected via a pair of Spirent RF channel emulators and can realize a variety of transmitter and receiver configurations. The use of FPGAs as baseband processors allows a great deal of flexibility in implementing designs while maintaining the capability to measure the resource utilization and power consumption of real hardware. Such measurements play a crucial role in evaluating the suitability of algorithms for deployment in real-world systems.

Reduced Complexity Soft MMSE MIMO Detector Architecture

Amiri, Kiarash; Dick, Chris; Rao, Raghu; Cavallaro, Joseph R.
Fonte: Wireless Innovation Forum, Inc. Publicador: Wireless Innovation Forum, Inc.
Tipo: Conference paper
ENG
Relevância na Pesquisa
56.32%
Computing the soft LLR values in MMSE receivers of MIMO systems requires a very large complexity. In this paper, we propose a reduced complexity soft MMSE detector for MIMO systems. We use different complexity reductions techniques and propose an architecture based on the new reduced-complexity method. We also compare the complexity and show more than 2x complexity reduction using this method. We present complexity/performance tradeoffs to demonstrate the efficacy of our techniques. More importantly, these techniques give the receivers the flexibility to choose how accurately they perform the detection based on the available resources.

Novel Sort-Free Detector with Modified Real-Valued Decomposition (M-RVD) Ordering in MIMO Systems

Amiri, Kiarash; Dick, Chris; Rao, Raghu; Cavallaro, Joseph R.
Fonte: IEEE Publicador: IEEE
Tipo: Conference paper
ENG
Relevância na Pesquisa
66.4%
K-best MIMO detection technique is the prominent method of simplifying the detection complexity in MIMO systems while maintaining BER performance comparable with the optimum maximum-likelihood (ML) detection technique. However, sorting the candidate nodes in the tree search of the conventional K-best detection can take a significant number of cycles which would reduce the achievable data rate of the detector. In order to reduce this delay, and keep high performance at the same time, we propose using a novel sort-free based MIMO detector which avoids the demanding sorting step. Moreover, this detector utilizes a novel modified real-valued decomposition (M-RVD) ordering that, when compared to the conventional real valued decomposition scheme, can improve the BER performance at no extra computational cost. We show that our proposed detector can outperform the conventional K-best detector with a smaller combination of computation and latency requirements.

Implementation Trade-Offs For Linear Detection In Large-Scale MIMO Systems

Yin, Bei; Wu, Michael; Studer, Christoph; Cavallaro, Joseph R.; Dick, Chris
Fonte: IEEE Publicador: IEEE
Tipo: Conference paper
ENG
Relevância na Pesquisa
56.32%
In this paper, we analyze the VLSI implementation tradeoffs for linear data detection in the uplink of large-scale multiple-input multiple-output (MIMO) wireless systems. Specifically, we analyze the error incurred by using the suboptimal, low-complexity matrix inverse proposed in Wu et al., 2013, ISCAS, and compare its performance and complexity to an exact matrix inversion algorithm. We propose a Cholesky-based reference architecture for exact matrix inversion and show corresponding implementation results on an Virtex-7 FPGA. Using this reference design, we perform a performance/complexity trade-off comparison with an FPGA implementation for the proposed approximate matrix inversion, which reveals that the inversion circuit of choice is determined by the antenna configuration (base-station antennas vs. number of users) of large-scale MIMO systems.

On the MIMO Capacity for Distributed System under Composite Rayleigh/Rician Fading and Shadowing

Gonz??lez-Aurioles, Santiago; Padilla, Jos?? Luis; Padilla, Pablo; Valenzuela Vald??s, Juan F.; Gonz??lez-Macias, Juan C.
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.37%
Wireless channels are commonly affected by short-term fading and long-term fading (shadowing). The shadowing effects must be taken into account also when mobility is present in the wireless scenario. Using a composite fading model, the total channel capacity can be studied for a scenario with short-term Rayleigh fading along with shadowing. This work provides quantitative results for these kinds of scenarios with Rayleigh fading and shadowing, considering also multiple-input and multiple-output systems, which have not been previously reported. In addition, the channel capacity has been studied in depth in its relation with the shadowing level, signal to noise ratio, and the number of elements in the multiple-input and multiple-output system. Moreover, the channel performance with shadowing has been compared to the one without it. Furthermore, Rician model with shadowing is studied and its results are reported. In addition, correlated and experimental results are provided. It is identified that the distributed MIMO systems can benefit from shadowing in Rician channels. This advantage has not been reported previously. This type of fading is proposed for massive MIMO by others and our results open the door to emulate massive MIMO on a reverberation chamber.

Bit and power loading for MIMO systems with statistical channel knowledge at the transmitter

Li, Hong
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Tese de Doutorado Formato: application/pdf
ENG
Relevância na Pesquisa
56.52%
In MIMO (multiple input-multiple output) communication, the adaptation of the modulation and coding at the transmitter side according to the channel characteristics allows reducing the transmission power and/or enhancing the data rates. However, it is not always feasible to have instantaneous knowledge of the channel at the transmitter. This Thesis focuses on the case that the receiver has (perfect) instantaneous Channel State Information (CSIR) but the transmitter has only access to its distribution (CDIT). This is a practical case that applies, particularly, to situations where the channel varies rapidly. Under CDIT, the input cannot be adapted to the instantaneous state of the channel and thus SVD (singular value decomposition) cannot be used to diagonalize the channel. Achieving capacity requires a complex Gaussian input vector with a covariance that depends on the channel distribution. In practice, however, discrete constellations are used instead of Gaussian signals. Determining the optimum signalling strategy with discrete constellations is difficult in general, and thus a pragmatic approach is using the spatial signalling directions indicated by the capacityachieving covariance. Several classical practical bit and power loading algorithms are available for parallel-channel settings. To guarantee the quality of service...

Antenna solutions for MIMO systems using parasitic elements

Corisco Beltrán, María del Carmen; Dones Luengo, Javier
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: info:eu-repo/semantics/bachelorThesis; info:eu-repo/semantics/masterThesis Formato: application/pdf; application/pdf; application/pdf; text/plain
ENG
Relevância na Pesquisa
66.42%
In the last years, Multiple Input Multiple Output (MIMO) systems have become the cornerstone of the future of Wireless communications. The performance of these systems in terms of channel capacity has meant that transmission rates that were impossible some years ago can be real nowadays. Unfortunately, MIMO systems have a characteristic that can mean a problem in the Wireless and mobile market, in where the eagerness to minimize the size of the devices is one of the mainly objectives. This non-desirable characteristic is the difficulty when compacting multiple active antennas (and, hence, their corresponding radiofrequency chains) in a handset terminal. Therefore, the idea of finding other alternatives that could emulate the behaviour of having multiple antennas represents a quite attractive and wide research area. The use of parasitic elements seems to be the most effective alternative when designing compact antennas for MIMO systems. In fact, the inclusion of these elements around an active antenna allows us to orient the beam towards different directions, what can be a quite interesting approach to have multiple antennas. Therefore, the idea is simple: just having one active element and a set of parasitics surrounding it, we can orient the beam towards different directions in order to maximize the channel capacity with a small impact on the features and with clear advantages in terms of compacting and cost. In this sense...

Performance of MIMO systems in measured indoor channels with transmitter noise

Castro-Castro, Paula-María; González-Coma, José P.; García-Naya, José A.; Castedo, Luis
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.45%
This study analyzes the impact of transmitter noise on the performance of multiple-input multiple-output (MIMO) systems with linear and nonlinear receivers and precoders. We show that the performance of MIMO linear and decision-feedback receivers is not significantly influenced by the presence of transmitter noise, which does not hold true in the case of MIMO systems with precoding. Nevertheless, we also show that this degradation can be greatly alleviated when the transmitter noise is considered in the MIMO precoder design. A MIMO testbed developed at the University of A Coruña has been employed for experimentally evaluating how much the transmitter noise impacts the system performance. Both the transmitter noise and the receiver noise covariance matrices have been estimated from a set of 260 indoor MIMO channel realizations. The impact of transmitter noise has been assessed in this realistic scenario.

Statistical Properties of a Parametric Channel Model for Multiple Antenna Systems

Durrani, Salman; Bialkowski, Marek E; Latif, Saba
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Relevância na Pesquisa
56.29%
Parametric channel models for Multiple Input Multiple Output (MIMO) systems have received much attention in recent years. This paper investigates the statistical properties of a parametric channel model for MIMO systems in an urban macro-cell environment.

Directional random scattering MIMO channels: Entropy analysis and capacity optimization

Sadeghi, Parastoo; Abhayapala, Thushara; Kennedy, Rodney
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Relevância na Pesquisa
56.32%
In this paper, we study the effect of directional random scattering on the capacity of multiple-input multiple-output (MIMO) systems. First, we use the spatial decomposition of the MIMO channel matrix to analyze the randomness (entropy) of directional sca

Spatial precoder design for space-time coded MIMO systems: based on fixed parameters of MIMO channels

Lamahewa, Tharaka; Kennedy, Rodney; Abhayapala, Thushara; Nguyen, Van K
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.39%
In realistic channel environments the performance of space-time coded multiple-input multiple output (MIMO) systems is significantly reduced due to non-ideal antenna placement and non-isotropic scattering. In this paper, by exploiting the spatial dimensio

Large Deviation Delay Analysis of Queue-Aware Multi-user MIMO Systems with Multi-timescale Mobile-Driven Feedback

Chen, Junting; Lau, Vincent K. N.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.25%
Multi-user multi-input-multi-output (MU-MIMO) systems transmit data to multiple users simultaneously using the spatial degrees of freedom with user feedback channel state information (CSI). Most of the existing literatures on the reduced feedback user scheduling focus on the throughput performance and the user queueing delay is usually ignored. As the delay is very important for real-time applications, a low feedback queue-aware user scheduling algorithm is desired for the MU-MIMO system. This paper proposed a two-stage queue-aware user scheduling algorithm, which consists of a queue-aware mobile-driven feedback filtering stage and a SINR-based user scheduling stage, where the feedback filtering policy is obtained from the solution of an optimization problem. We evaluate the queueing performance of the proposed scheduling algorithm by using the sample path large deviation analysis. We show that the large deviation decay rate for the proposed algorithm is much larger than that of the CSI-only user scheduling algorithm. The numerical results also demonstrate that the proposed algorithm performs much better than the CSI-only algorithm requiring only a small amount of feedback.

Delay-aware BS Discontinuous Transmission Control and User Scheduling for Energy Harvesting Downlink Coordinated MIMO Systems

Cui, Ying; Lau, Vincent K. N.; Wu, Yueping
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/04/2012
Relevância na Pesquisa
56.28%
In this paper, we propose a two-timescale delay-optimal base station Discontinuous Transmission (BS-DTX) control and user scheduling for downlink coordinated MIMO systems with energy harvesting capability. To reduce the complexity and signaling overhead in practical systems, the BS-DTX control is adaptive to both the energy state information (ESI) and the data queue state information (QSI) over a longer timescale. The user scheduling is adaptive to the ESI, the QSI and the channel state information (CSI) over a shorter timescale. We show that the two-timescale delay-optimal control problem can be modeled as an infinite horizon average cost Partially Observed Markov Decision Problem (POMDP), which is well-known to be a difficult problem in general. By using sample-path analysis and exploiting specific problem structure, we first obtain some structural results on the optimal control policy and derive an equivalent Bellman equation with reduced state space. To reduce the complexity and facilitate distributed implementation, we obtain a delay-aware distributed solution with the BS-DTX control at the BS controller (BSC) and the user scheduling at each cluster manager (CM) using approximate dynamic programming and distributed stochastic learning. We show that the proposed distributed two-timescale algorithm converges almost surely. Furthermore...

Resource management for multi-user MIMO systems

Wang, Qi
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Relevância na Pesquisa
66.6%
Cimini, Leonard J., Jr.; Greenstein, Larry J.; Multiple-input multiple-output (MIMO) can be used to achieve substantial throughput and reliability via spatial multiplexing and diversity. It can also be used to allow multi-user (MU) scenarios, thereby further boosting throughputs. However, the interference caused by multiple users sharing the spatial channel might greatly degrade potential gains promised by MU-MIMO. In this dissertation, we mainly investigate two MU-MIMO systems, namely downlink channels and interference channels, and propose transmission strategies to benefit MU systems by efficiently utilizing available resources. First, we investigate downlink MU-MIMO channels and consider the impairments from imperfect channel state information (CSI). In MU-MIMO systems, perfect CSI is essential to eliminate the interference; otherwise, residual interference due to CSI errors can severely degrade the performance. Closed-form expressions are derived for achievable rates of such systems with imperfect CSI, caused by quantization and delay. We compare the performance of single-user (SU) and MU transmission and provide guidelines to determine which mode should be activated for a particular environment. For MIMO links with limited feedback...

Progressive linear precoder optimization for MIMO packet retransmissions exploiting channel covariance information

Sun, H; SHi, Z; Zhao, C.; Manton, Jonathan; Ding, Z.
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.4%
This work investigates the design of linear precoders for ARQ packet retransmissions in Multi-Input Multi-Output (MIMO) systems. We consider transmitter precoder design based on partial MIMO channel information in the form of their covariance feedback. Our objective is to maximize the ergodic mutual information provided by multiple (re)transmissions of a packet subject to transmission power constraint. We propose a set of near-optimal successive linear ARQ precoders for flat fading MIMO channels. This progressive linear ARQ precoder combines the appropriate power loading and the reverse-order pairing of singular values in the current retransmission with previous transmissions. This reverse-order pairing is a special feature unique to our sequential ARQ precoding approach with demonstrated performance gains.

Channel modelling for MIMO systems; Modelos de canal para sistemas MIMO

Mota, Susana de Jesus
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
66.6%
Systems equipped with multiple antennas at the transmitter and at the receiver, known as MIMO (Multiple Input Multiple Output) systems, offer higher capacities, allowing an efficient exploitation of the available spectrum and/or the employment of more demanding applications. It is well known that the radio channel is characterized by multipath propagation, a phenomenon deemed problematic and whose mitigation has been achieved through techniques such as diversity, beamforming or adaptive antennas. By exploring conveniently the spatial domain MIMO systems turn the characteristics of the multipath channel into an advantage and allow creating multiple parallel and independent virtual channels. However, the achievable benefits are constrained by the propagation channel’s characteristics, which may not always be ideal. This work focuses on the characterization of the MIMO radio channel. It begins with the presentation of the fundamental results from information theory that triggered the interest on these systems, including the discussion of some of their potential benefits and a review of the existing channel models for MIMO systems. The characterization of the MIMO channel developed in this work is based on experimental measurements of the double-directional channel. The measurement system is based on a vector network analyzer and a two-dimensional positioning platform...