Abstract- This paper presents a technique for Antenna beam forming in high data rate OFDM-MIMOsystems. The technique makes use of the Singular Value Decomposition (SVD) algorithm for matrix decomposition using Givens Rotation. In this paper a hardware oriented two-step diagonalization SVD scheme is derived from simple two-sided unitary transformations developed to ensure hardware and performance efficiency using CORDIC. Each unitary transformation step in the diagonalization procedure is identical in structure to permit pipelined systolic execution. The simulation results are obtained for fixed point models usingSVD algorithm. An overall architecture is created in Matlab for 4X4 Complex valued matrices elements and then simulated. The VHDL code is then written to describe the architecture of the overall design and is the synthesized using Xilinx ISE 10.1 software for virtex-4 target device.
Abstract: Problem statement: The Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) system has been receiving a great attention, as one of solutions for achieving high speed, efficient and high-quality service for the wireless communications. However, the transmitted signal still has high PAPR because of OFDM characteristics. Many methods have been proposed to solve this problem, but the most of them decrease high Peak-to-Average Power Ratio (PAPR) as well as the data rate. Approach: This proposal described a new suboptimal technique for reduction of the PAPR by combining two suitable methods for MIMOOFDMsystems. The first method was based on Boolean Particle Swarm intelligence Optimization (BPSO) applied to Partial transmit Sequence (PTS) and the second was the Space Time Bloc Coding (STBC). Result: Apply only the PTS technique and independently on each transmitted antenna, was effective to reduce PAPR, but it requires high computation complexity. Therefore, the BPSO/PTS technique provided better performance and it was been promoted as an uncomplicated way for PAPR reduction. Thanks of the BPSO/PTS algorithm; the transmitted sequence was selected with minimizing the maximum PAPR over all transmission antennas. The simulations and the BER performance demonstrated that more inertia weight and phase weighting factor obtained better PAPR reduction performance without bringing much higher complexity. Conclusion: Results show that the added BPSO/PTS method to orthogonal space time bloc coding minimizes computational complexity cost as well as the PAPR and gives best optimal PTS performance in comparison with the conventional methods.
In this paper, we design new quantization strategies that allow efficient CSI feedback for IA-precoder MIMO-OFDM- based systems. A quantized version of the CSI associated with the different links between BS and UT is fed back from the UT to the BS and sent to the other BSs through a limited-capacity backhaul network. The proposed quantization strategies have low-complexity and low-bit rates just quantizing part of the samples of either the channel frequency response (CFR) or the channel impulse response (CIR). These quantized channels are then employed by the different BSs to perform the overall IA design. Our channel quantization methods have much lower complexity than the RVQ-based techniques, since they do not require the use of large codebooks. More- over, for severely time-dispersive channels, the RVQ-based schemes require the quantization of all subchannel samples; thus, the proposed scheme is even more advantageous for these cases, with lower feedback overhead. As the iterative IA MMSE-based algorithms have some degradation in high SNR due to channel errors, a new robust iterative IA technique is also proposed and evaluated using the proposed feedback strategies, where channel quantization errors are taken into account in IA design.
The performance of the pure-analog techniques is limited by constraints on the amplitudes of phase shifters and due to the phases of the ones quantized. Therefore, analog beamforming is usually limited to single-stream transmission . These limitations are overcome by doing some signal processing at an analog level and the rest at the digital level. These architectures are called hybrid analog/digital architectures and have been addressed in [15, 16]. Precod- ing and/or combining/equalization designs for single-user systems have been addressed for fully connected hybrid architectures in [17–19]. In these architectures, each of the RF chains is connected to all receive-and-transmit antennas. In , a hybrid spatially sparse precoding/combining approach was designed for mmWave mMIMO systems. The spatial structure of mmWave channels was used to transform the single-user multistream precoding and combining scheme into a sparse reconstruction problem. In , joint turbo-like beamforming was designed to compute transmit/receiving analog beamforming coefficients; however the digital pro- cessing part was not considered. In , codebook design approaches were addressed for single-stream transmissions through an analog beamforming structure. For multiuser systems, some beamforming approaches have been proposed for fully connected hybrid architectures [20–22]. The authors of  proposed uplink receiving beamforming where they assume only single antenna user-terminals (UTs), and at both stages analog and digital ones dealt with multiuser interfer- ence. Reference  proposed for the downlink a limited feedback analog/digital two-stage precoding and combin- ing algorithm. Transmit/receiving analog beamforming are jointly computed in the first stage to maximize the power of the desired signal, and then the interference is explicitly mitigated using conventional linear zero-forcing (ZF) pre- coding in the second stage, that is, in the digital domain. An efficient hybrid iterative block space-time multiuser equalizer was proposed in . This equalizer was designed based on the iterative block decision feedback equalization (IB-DFE) principle . IB-DFE was originally proposed in . It does not need the feedback loop of the channel decoder output, and it can be considered as a low complexity turbo equalizer. IB-DFE has been extended to several scenarios, like diversity scenarios and conventional and cooperative MIMOsystems, among many others [25–30].
In this paper a UQ based quantization strategy is proposed and implemented, using a reduced amount of bits to feed back the CSIT in multi-user MIMO channels, exploiting channels’ sparsity. A comparison is also made between the commonly used RVQ strategy with the proposed P-UQ one, for sparse channels. It was shown that we can have per- formances close to the ones with perfect CSI with a relatively low number of bits to quantize an appropriate number of samples of the channel. This method requires the quantization of only the non-zero CIR taps, reducing the amount of information to be fed back. We numerically showed that is not possible to similarly reduce the overhead for the RVQ without significant degradation. Thus, this work presents a significant contribution for next generation wireless networks that needs CSIT with reduced overheads.
Abstract: Multiple-input multiple-output (MIMO) wireless technology in combination with Orthogonal Frequency Division Multiplexing (OFDM) is a promising solution for implementing efficient next-generation wireless local area networks (WLANs) and fourth-generation mobile cellular wireless systems. This paper explores the advantages of using the combined effects of MIMO and OFDM for the transmission of JPEG compressed images. The spatially correlated channel is estimated using a pilot tone transmission and a power allocation based on Lagrangian dual is utilized to improve the power efficiency system. It is assumed that the channel state information is fedback from the receiver through a low feedback path. With unequal power allocation it is possible to extent the application of MIMO-OFDM for WLANs to efficient image transmission over a spatially correlated channel. The proposed unequal power allocation gives less error compared to equal power allocation.
It would be beneficial to use the three features color, shape and texture in many applications like searching a certain disease from a database of medical images. Therefore, an efficient combination of these features into multimodal descriptors of the audio-visual content should be considered in more detail in future work. Another issue is the development of a flexible and dynamically adjustable similarity measure based on relevance feedback obtained from the end-user should be taken into account. The issue of distance measures between feature vectors also need to be considered. Euclidean distance was used in this method because of its simplicity and interpretability, but it would be valuable to evaluate other distance measures and their effect on retrieval performance.
The Miller exponent block, which is a modification over PI-P/SO shift register is used to calculate the ‘S' and 'D' values in the algorithm. The Miller controller detects the zeros in the exponent using shifting. A PRNG has been used to feed the random seed value to the RSA module for random base number. The counter counts a RSA intermediate event as clock. Miller controller serves as the master control unit of the system. The signal from the Miller controller further controls the events/states controlled by a separate RSA module controller which acts as a slave control unit.
Abstract-Impulse noises are occurred in the images during image signal acquisition and processing from one location to another location. In this paper, the optimal detector noise filtering algorithm and its efficient hardware architecture is presented. The proposedarchitecture comprises of orthogonal direction pattern generation, sorter, thresholder, local binary converter, multimodal filter and pixel converter units respectively. The local binary converter unit detects and corrects the noise pixel efficiently using a simple logic circuit. The design possesses only two line memory buffers with very low computational complexity, thereby reducing the hardware cost and appropriate for several real-time applications.
The proposed identification methods use second-order statis- tics of the signals received by an antenna array, assuming that the transmitted signals are Phase Shift Keying (PSK) modulated. These methods are based on a Parallel Factor (PARAFAC) decomposition  of a third-order tensor (three way array) composed of channel output covariances. One of the great advantages of these methods is that they allow working with weak uniqueness conditions compared with previous works [4, 6, 7, 8], that require a number of channel outputs greater than the number of Volterra filter parameters. In- deed, the proposed tensor-based algorithms provide a great flexibil- ity on the number of antennas, which is particularly important when identifying Volterra systems. Moreover, PARAFAC decomposition avoids the use of a pre-whitening step, an operation that increases the computational complexity and may degrade the channel estima- tion.
Although theoretical analysis and signal processing techni- ques for OFDM with nonlinear memoryless PAs have been widely studied in the literature –, there is a lack of works on OFDMsystems with memory PAs. Using the theoretical result developed in the present paper, we can extend some theoretical results and techniques for ICI canceling that work with polynomial PAs to the case of memory polynomial PAs. As an example of application of this result, we derive new expressions for the theoretical symbol error rate (SER) provided by an OFDM system with a memory polynomial PA, these expressions being derived directly from the polynomial PA case.
The proposedarchitecture should also be able to support the addition and removal of monitored devices during the system’s execution. For this purpose a fourth entity is responsible for constantly looking for changes in the system’s topology, managing the corresponding agents accordingly and assuring that the associative relations between them are maintained congruently. Upon detecting the plugging of a new device, the architecture should enact a self-organized response by having this entity launch a new monitoring agent to abstract the recently connected component, associating it to the correct higher-level entity in the appropriate layer of the monitoring tree. Similarly, once a device is unplugged the system is capable of detecting this occurrence, organizing itself accordingly by removing the corresponding agent from the tree.
The block diagram of the Space time Frequency (STF) coded OFDM system is shown in the above fig-3.2. The data stream is encoded by a convolution encoder, followed by an inter leaver. After symbol mapping, the tones enter the STF encoder and then forwarded to the OFDM modem of the different antennas. The OFDM modem considered at each antenna consists of M subcarriers. The M tones at each antenna are passed through inverse Fast Fourier Transform blocks (IFFT). A cyclic prefix is also added to each of the resultant signals. To avoid the inter-symbol interference, the guard time is chosen to be longer than the channel delay spread. The well chosen cyclic prefix length in the OFDM multiplexing system turns in a wideband frequency selective channel in to number of parallel independent frequency non selective channels. Finally the resulting signal is up-converted to the carrier frequency and transmitted across the mobile radio channel.
Neste contexto, novos algoritmos de identifica¸c˜ ao cega de canais s˜ ao desenvolvidos nesta tese com base em um problema de otimiza¸c˜ ao de m´ınimos quadrados de passo ´ unico (SS-LS). Os m´etodos propostos exploram plenamente a estrutura multilinear do tensor de cumulantes bem como suas simetrias e redundˆ ancias, evitando assim qualquer forma de pr´e-processamento. Com efeito, a abordagem SS-LS induz uma solu¸c˜ ao baseada em um ´ unico procedimento de mini- miza¸c˜ ao, sem etapas intermedi´ arias, contrariamente ao que ocorre na maior parte dos m´etodos existentes na literatura. Utilizando apenas os cumulantes de ordem 4 e explorando o con- ceito de Arranjo Virtual, trata-se tamb´em o problema da localiza¸c˜ ao de fontes, num contexto multiusu´ ario. Uma contribui¸c˜ ao original consiste em aumentar o n´ umero de sensores virtu- ais com base em uma decomposi¸c˜ ao particular do tensor de cumulantes, melhorando assim a resolu¸c˜ ao do arranjo, cuja estrutura ´e tipicamente obtida quando se usa estat´ısticas de ordem 6. Considera-se ainda a estima¸c˜ ao dos parˆ ametros f´ısicos de um canal de comunica¸c˜ ao MIMO com muti-percursos. Atrav´es de uma abordagem completamente cega, o canal multi-percurso ´e primeiramente tratado como um modelo convolutivo e uma nova t´ecnica ´e proposta para estimar seus coeficientes. Esta t´ecnica n˜ ao-param´etrica generaliza os m´etodos previamente propostos para os casos SISO e MIMO (sem mem´ oria). Fazendo uso de um formalismo tensorial para rep- resentar o canal de multi-percursos MIMO, seus parˆ ametros f´ısicos podem ser obtidos atrav´es de uma t´ecnica combinada de tipo ALS-MUSIC, baseada em um algoritmo de subespa¸co. Por fim, ser´ a considerado o problema da determina¸c˜ ao de ordem de canais FIR, particularmente no caso de sistemas MISO. Um procedimento completo ´e introduzido para a detec¸c˜ ao e estima¸c˜ ao de canais de comunica¸c˜ ao MISO seletivos em freq¨ uˆencia. O novo algoritmo, baseado em uma abordagem de defla¸c˜ ao, detecta sucessivamente cada fonte de sinal, determina a ordem de seu canal de transmiss˜ ao individual e estima os coeficientes associados.
This chapter begins by describing the adopted MU-MIMO downlink system model, followed by an explanation of the BD method, used to cancel CCI, and two low-complexity channel estimators commonly used in nowadays communication systems: LS and MMSE channel estimator. Additionally, it is introduced a channel estimation technique using Zadoff-Chu sequences as pilot signals. These sequences possess ideal periodic autocorrelation properties, which makes them ideal to be considered training sequences. To conclude the chapter, are presented the simulation results that allow a comparison purposes between the different channel estimation techniques. Simulations results will demonstrate how accurate the introduced channel estimation is, in function of the number of users and the number of pilots applied in estimation. BER and MSE are used as performance measurement and comparison purposes. Results are based on Monte Carlo experiments with 15 000 simulations and QPSK modulation. Both BER and MSE results are expressed in function of 𝐸 𝑏
that the algorithm was effective for the cases where the images are very highly corrupted. Yu et al. (2008) has developed an efficient procedure for removing random- valued impulse noise in images. It provided very moderate PSNR as image quality measurement parameter. Al-Araji et al. (2007) has developed impulsive noise reduction techniques based on rate of occurrence estimation. Lien et al. (2013) has proposed an efficient denoising architecture for removal of impulse noise in images. Chapter 3 propose an efficient impulse noise filtering algorithm and chapter 4 discusses the results achieved with various state of arts.
Abstract— MIMO communication is mainly use in the OFDM to improve the communication performance and capacity. DWT based MIMO-OFDM is used in this paper. Compare to the FFT based MIMO-OFDM it has lot advantages. There is no need for cyclic prefix, flexibility and optimal resolution. Ripple(Wavelet) concept has developed as a fresh scientific implement with the aim of preserve be functional in several applications such as processing of image, biomedical manufacturing, radar, physics, organize systems also message systems. The essential region of purpose of ripples in communication system: numerous accesses. A fresh modulation/multiplexing scheme consuming ripple transform remained planned for (3rd production organization project) 3GPP systems. This fresh modulation system implemented in (orthogonal frequency division multiplexing) OFDM scheme in addition to conventional based(FFT) transform blocks is replaced by wavelet transform blocks. There are many multiplicity of ripple transforms are offered, out of which four were chosen. They are Haar, Daubechies, Bi-orthogonal and reverse Bi-orthogonal transforms. Haar wavelet is best one of among all types of wavelet. The performance of DWT based MIMO-OFDM is calculated by bit error rate (BER) in various channel that is AWGN channel and Rayleigh channel. Using MATLAB-Simulation which channel is best for the DWT based MIMO-OFDM.
A MIMO-OFDM wireless communication system is a combination of MIMO and OFDM Technology. The combination of MIMO and OFDM produces a powerful technique for providing high data rates over frequency-selective fading channels. MIMO-OFDM system has been currently recognized as one of the most competitive technology for 4G mobile wireless systems. MIMO-OFDM system can compensate for the lacks of MIMOsystems and give play to the advantages of OFDM system.In this paper , the bit error rate (BER) performance using linear maximum likelihood alamouti combiner (LMLAC) decoding technique for space time frequency block codes(STFBC) MIMO-OFDM system with frequency offset (FO) is being evaluated to provide the system with low complexity and maximum diversity. The simulation results showed that the scheme has the ability to reduce ICI effectively with a low decoding complexity and maximum diversity in terms of bandwidth efficiency and also in the bit error rate (BER) performance especially at high signal to noise ratio.
Nelissen et al [NPP15] recognize that space and time partitioning is important to ensure that a runtime monitor does not affect the monitored system, either in its behaviour or by propagating faults. They propose a monitoring architecture where each event type (rather than each monitor) has their own buffer to store the events. Each buffer works on a single producer, multiple consumer fashion (each reader has a pointer to the oldest event that they have not read yet), and since the events read are never removed (the buffers are circular, so new events overwrite older ones) the access to the buffer does not need any further synchronization and a single event can be of use to multiple readers. Readers feeding the same monitor synchronize the monitor event timeline via a synchronization variable storing the timestamp of the last event read, so the readers can determine which event should be read and sent to the runtime monitor first.