Multi-User MIMO Communication

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Performance analysis of Multiple-input Multipleoutput (MIMO) Orthogonal Frequency-Division Multiplexing (OFDM) systems with carrier frequency offset and channel estimation errors is considered in this paper. Based on the analysis of the Inter-Carrier-Interference (ICI) and Inter-Antenna-Interference (IAI) due to the residual frequency offsets, the average Signal-to-Interference-and-Noise Ratio (SINR) is derived. The bit error rate of equal gain combining (EGC) and maximal ratio combining (MRC) with MIMO-OFDM is analyzed, and an infinite-series approximation for the bit error rate is derived. Simulation results illustrate the accuracy of the theoretical analysis. Multiple-input multiple-output (MIMO) technology can significantly increase the wireless system capacity . By transforming the frequency-selective MIMO channel to a set of flat-fading MIMO channels, MIMO-OFDM can achieve a high capacity at a low cost of equalization and demodulation. However, just as single-input single-output (SISO)-OFDM systems are highly sensitive to frequency offset, so too are the MIMO-OFDM systems. Many frequency offset estimators have already been developed for SISO-OFDM systems [2]- . A synchronization algorithm for MIMO-OFDM is proposed in , where identical timing offset and frequency offset are assumed to each transmit-receive antenna pair. Parameter estimation for MIMO flat-fading channels with the frequency offsets is discussed in , where the frequency offsets for different transmit and receive antennas are assumed to be different. Another channel impairment is the channel estimation error, which can impact the bit error rate of an OFDM system. Robust channel estimation for OFDM is discussed in , and the mean-square error (MSE) of channel estimation can be significantly reduced by exploiting the channel delay profile. An iterative joint frequency offset and channel estimator is proposed in , where a reliable estimation is performed based on the maximum likelihood principle by using pilots. Optimal training signal design for a frequency-selective block fading channel estimation in MIMO-OFDM is discussed in , which is based on the minimization of the MSE. The bit error rate of SISO-OFDM impaired by the frequency offset is analyzed in . In this paper, we give a generalized bit-error-rate's analysis of MIMO-OFDM, taking into consideration of both the frequency offset and channel estimation errors. We exploit

本研究探討高維投影場對黑洞陰影形狀的影響，特別聚焦於標量場修正廣義相對論後所引入的各向異性效應。我們建立等向與非等向的投影場 $\Phi$ 模型，並透過數值方式解聯立的 Einstein–$\Phi$ 方程，分析其對光子球與黑洞陰影半徑的影響。結果顯示，非等向配置會導致黑洞陰影的角度依賴性變形，赤道與極區半徑差異可達 2–3%。此偏差與事件視界望遠鏡（EHT）對 M87* 與 Sgr A* 的橢圓率觀測範圍相符。數值收斂測試確認誤差低於 1%，確保結果可信。我們主張，這類各向異性效應可作為檢驗高維修正重力理論的潛在觀測指標，並可與旋轉黑洞（Kerr）效應區分。展望未來，新一代儀器如 ngEHT 與太空 VLBI 將能更嚴格約束此類模型，為額外維度與時空基本結構的研究開啟新契機。

Recently, simultaneous wireless information and power transfer (SWIPT) emerged as the best solution for resource-constrained internet of things (IoT) networks. SWIPT ensures the provision of parallel information and power transfer in the network. Under the SWIPT model, many researchers use two well-established protocols: time switching (TS) and power splitting (PS). TS is better than PS when the signal is weak but inserts an extra delay because energy harvesting (EH) and information decoding (ID) happened two different times. However, PS protocol performs poorly in hard situations with low signal strength even if it conducts EH and ID simultaneously. Hence, this paper proposed a new model called mixed-SWIPT (MSWIPT) which combines TS and PS protocols in an intuitive manner. Further, this work proposes a multi-source EH mechanism in which the receiving node harvests energy from multiple sources which is different from single source, i.e., desired node's radio frequency (RF) signal. The multiple sources include non-participated Neighbor Node's RF signal, sink node and cochannel interference and noise. Under the routing, the node selection is formulated as maximum link capacity problems and solved through several constraints. Extensive simulations on proposed model prove the superiority in terms of EH and energy efficiency from the state-of-the-art methods.

Alamouti code is a simple space-time code that can be used for transmit diversity systems. This is a class of easily decoded space-time codes that achieve full diversity order in Rayleigh fading channels. Alamouti code exist only for certain numbers of transmit antennas and do not provide array gain like diversity techniques that exploit transmit channel information. When Channel State Information (CSI) is available at the transmitter, though, precoding the space-time codeword can be used to support different numbers of transmit antennas. The objective of the proposed work is to design a precoded STBC system to achieve better transmit diversity and shows comparison of bit error rate (BER) performance of Precoded Alamouti and Precoded OSTBC in Zero Forcing and MMSE equalization techniques. The Rayleigh fading channel is used as modulation channel.

Multiple-input multiple-output (MIMO) technology constitutes a breakthrough in the design of wireless communications systems, and is already at the core of several wireless standards. Exploiting multipath scattering, MIMO techniques deliver significant performance enhancements in terms of data transmission rate and interference reduction. This 2007 book is a detailed introduction to the analysis and design of MIMO wireless systems. Beginning with an overview of MIMO technology, the authors then examine the fundamental capacity limits of MIMO systems. Transmitter design, including precoding and space-time coding, is then treated in depth, and the book closes with two chapters devoted to receiver design. Written by a team of leading experts, the book blends theoretical analysis with physical insights, and highlights a range of key design challenges. It can be used as a textbook for advanced courses on wireless communications, and will also appeal to researchers and practitioners worki...

The International Electrotechnical Commission (IEC) develops and validates methods for assessing radio frequency electromagnetic field (RF EMF) exposure due to base stations (BS). When the assessment is performed in-situ, it is recommended to extrapolate the maximum level of exposure from measurement of stable signals, such as broadcast signal with BS of the 5 th generation (5G) of mobile communication systems (gNodeB). A comparative statistical analysis of extrapolation methods based on nominal antenna pattern (as measured in an anechoic chamber) and effective antenna pattern (as measured in scattering environment) of gNodeB is presented in this paper. This theoretical analysis shows that extrapolation with nominal antenna pattern may lead to significant overestimation of the maximum RF EMF exposure (up to 5.4 dB) in case of scattering environment or non-line-of-sight (NLOS) conditions. This overestimation is expected to be reduced by using effective antenna pattern in order to better represent the actual propagation conditions, such as those found in urban or dense urban areas. Therefore, it is recommended to perform extrapolation of the maximum exposure based on joint modeling of antenna beam pattern and representative value of the angular spread (AS) for the targeted deployment conditions. This conclusion was obtained from the observed consistence between two different approaches for determination of effective antenna gain. The first approach assumes statistical simulations with full three-dimensional (3D) channel model, especially distribution function of AS. The second approach enables simpler calculation of the effective antenna gain in scattering environment or NLOS conditions by considering only representative values from the full range of AS distribution function. The proposed simple method, if used with representative realistic values of AS, could reduce overestimation of RF EMF exposure resulting from an extrapolation factor based on nominal antenna gains of broadcast and traffic beams.

We consider efficient techniques for the design of a transceiver for a matrix channel with minimum mean square error (MMSE) decision-feedback (DF) detection when perfect channel information is available at both the transmitter and receiver. By combining the canonical property of the MMSE-DF detector and our recently developed equal-diagonal QRS decomposition of a matrix we obtain a uniform decomposition of mutual information in which each of the synthesized scalar subchannels has the same mutual information (under the assumption of error-free feedback). To assist our analysis of this uniform decomposition, we provide a new QR interpretation of the MMSE-DF receiver. This enables us to show that the natural detection order is optimal (in an SINR sense), and that for the proposed transmitter, the MMSE-DF detector is asymptotically equivalent to the maximum likelihood detector when the SNR is high. We also derive a low-complexity quadratic recursive algorithm for the characterization of all eligible S-factors in the QRS decomposition. When coupled with our QR interpretation of the MMSE-DF detector, this enables us to efficiently design the optimal transmitter and to efficiently implement the MMSE-DF receiver.

A compact planar inverted-F multi-band antenna array located on an infinite ground plane for multiple inputs multiple output (MIMO) systems is proposed in this paper. And the study of the suppression of the mutual coupling between the radiating elements of the antenna array is also presented. An identical two PIFA elements are placed uniquely without any distance to each other however; the mutual coupling reduction is achieved by maximizing the separation between them. The multi-band antenna array is designed to operate at GSM [880-960 MHz],

In this paper multi-antenna half-duplex and fullduplex relaying are compared from the perspective of achievable rates. Full-duplexing operation requires additional resources at the relay such as antennas and RF chains for self-interference cancellation. Using a practical model for the residual selfinterference, full-duplex achievable rates and degrees of freedom are computed for the cases for which the relay has the same number of antennas or the same number of RF chains as in the half-duplex case, and compared with their half-duplex counterparts. It is shown that power scaling at the relay is necessary to maximize the degrees of freedom in the full-duplex mode.

In-band full-duplex (FD) communication provides a promising alternative to half-duplex (HD) for wireless systems, due to increased spectral efficiency and capacity. In this paper, HD and FD radio implementations of two way, two hop and two way two hop communication are compared in terms of degrees of freedom (DoF) under a realistic residual self-interference (SI) model. DoF analysis is carried out for each communication scenario for HD, antenna conserved (AC) and RF chain conserved (RC) FD radio implementations. The DoF analysis indicates that for the two way channel, the achievable AC FD with imperfect SI cancellation performs strictly below HD, and RC FD DoF trade-off is superior when the SI can be sufficiently cancelled. For the two hop channel, FD is better when the relay has large number of antennas and enough SI cancellation. For the two way two hop channel, when both nodes require similar throughput, the achievable DoF pairs for FD do not outperform HD. FD still can achieve better DoF pairs than HD, provided the relay has sufficient number of antennas and SI suppression.

In-band full-duplex (FD) communication provides a promising alternative to half-duplex (HD) for wireless systems, due to increased spectral efficiency and capacity. In this paper, HD and FD radio implementations of two way, two hop and two way two hop communication are compared in terms of degrees of freedom (DoF) and achievable rate, under a realistic residual self-interference (SI) model. DoF analysis is carried out for each communication scenario, and achievable rates are computed at finite SNR levels for HD, antenna conserved (AC) and RF chain conserved (RC) FD radio implementations. The DoF analysis indicates that for the two way channel, AC FD performs strictly below HD with imperfect SI cancellation, and RC FD DoF trade-off is superior, when the SI can be sufficiently cancelled. For the two hop channel, FD is better when the relay has large number of antennas and enough SI cancellation. For the two way two hop channel, when both nodes require similar throughput, HD is generally better than FD; for asymmetric traffic, FD can achieve better rate pairs than HD, provided the relay has sufficient number of antennas and SI suppression. Computed achievable rates for each scenario indicate that DoF results also extend to finite SNR.

In this paper we devise an analytical framework for the characterization of wireless transceivers. Subsequently, we utilize the proposed methodology in order to calculate the constrained capacity of the delay-limited wireless transceivers. We demonstrate that the realistic constrained capacity may be significantly lower than the idealized unconstrained Shannon capacity. Furthermore, the constrained capacity of a delay-limited transceiver may vary significantly depending on the particular combination of application scenario and channel conditions.

Increasing data rate and high performance is the target focus of wireless communication. The multi carrier on multi-hop communication system using relay's diversity technique which is supported by a reliable coding is a system that may give high performance. This research is developing a model of multi user and two scheme of multi carrier CDMA on multi hop communication system with diversity technique which is using Alamouti codes in Rayleigh fading channel. By Alamouti research, Space Time Block Code (STBC) for MIMO system can perform high quality signal at the receiver in the Rayleigh fading channel and the noisy system. In this research, MIMO by STBC is applied to single antenna system (Distributed-STBC/DSTBC) with multi carrier CDMA on multi hop wireless communication system (relay diversity) which is able to improve the received signal performance. MC DS CDMA on multi hop wireless communication system with 2 hops is better performing than MC CDMA on multi user without Multi User Detector. To reach BER 10-3 multi hop system with MC CDMA needs more power 5 dB than MC DS CDMA at 5 users using Alamouti scheme for symbol transmission at the relay.

This paper gives an overview of the objectives and current research activities on interference avoidance in the EC funded research project ARTIST4G. It is the main objective of the ARTIST4G Work Package 1 (WP1), to build forward on the 3GPP LTE Release 8 baseline, proposing a novel fair mobile broadband technological framework in which to design innovative, practical, scalable and cost-effective interference avoidance solutions. This paper provides an overview of the fundamental classes of innovations studied in ARTIST4G Work Package 1 (WP1) and presents some performance results obtained by means of numerical simulations and test-bed measurements run in the field.

Recent Advances in Wireless Communications and Networks 60 are available at the receiver. In fading channels, some samples are severely faded, while others are less attenuated; hence, in statistics, the probability of the signal strength of all samples being simultaneously below a given level becomes small, as compared with the case without applying diversity techniques. Consequently, we can overwhelm the channel fading by imposing an appropriate selection or combination of various samples, so as to dramatically improve the signal quality. Based on signal processing domains to obtain diversity gains, diversity techniques can be classified into time, frequency and space diversity. Here, we focus on space diversity techniques where multiple antennas are deployed at the transmitter or receiver sides. One category of space diversity schemes is to combine multiple signal replicas at the receiver, which is termed as receive diversity. The other category is to use multiple antennas at the transmitter, and this kind of diversity schemes is called transmit diversity . In this section, we first present various receive diversity schemes, including selection combining, switch combining, equal-gain combining (EGC), and MRC. The well-known Alamouti's transmit diversity scheme using two transmit antennas and one receive antenna is then introduced. The generalized case using two transmit antennas and multiple receive antennas is shown as well. Subsequently, space-time block codes (STBCs) with the number of transmit antennas larger than two are presented. Finally, a maximum ratio transmission (MRT) scheme is discussed to simultaneously achieve both transmit and receive diversity gains and maximize the output signal-to-noise ratio (SNR) . In cellular systems, receive diversity techniques have been widely applied at base stations for uplink transmission to improve the signal reception quality. This is mainly because base stations can endure larger implementation size, power consumption, and cost. In general, the performance of the receive diversity not only depends on the number of antennas but also the combining methods utilized at the receiver side. According to the implementation complexity and the extent of channel state information required at the receiver, we will introduce four types of combining schemes, including selection combining, switch combining, EGC, and MRC, in the following. Selection combining is a simple receive diversity combining scheme. Consider a receiver equipped with n R receive antennas. Fig. depicts the block diagram of the selection combining scheme. The antenna branch with the largest instantaneous SNR is selected to receive signals at every symbol period. In practical, since it is difficult to measure the SNR, one can implement the selection combining scheme by accumulating and averaging the received signal power, consisting of both signal and noise power, for all antenna branches, and selecting one branch with the highest output signal power.

The growing demand of multimedia services and the growth of broadband Internet related contents lead to increasing interest to high speed communications. This is because the higher bit rate and higher quality applications must be provided via the Internet such as huge data downloading, high quality streaming videos. On the other hand, the requirement for wide bandwidth and flexibility imposes the use of efficient transmission methods that would fit well to the characteristics of wideband channels especially in wireless environment where the channel is very hostile. Combining Multi-Input Multi-output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) with Guard Interval (GI) is a highly promising method to achieving required data rate for real time application. However, in a frequency selective fading environment, equally sharing the power transmission in the space domain does not optimize the global transmission. In this publication, we propose to adapt the power allocation in the space domain (i.e. through the different transmit antennas) in function of the channel variations and optimization process based on the optimality of the global Bit Error Rate (BER). Simulation results show significant gains for several antenna configurations.

This document looks into coordinated radio resource allocation algorithms in deployments of huge number of femto-access points (FAP) by exploiting the message exchange at control-plane level through the wired ISP backhaul link. The algorithms present in this document are based on decentralized cooperative strategies supported by Game Theory. Decentralized resource allocation algorithms based on price exchange have been derived under different criteria: guaranteeing a minimum rate with the minimum power, maximizing the weighted sum-rate of the system, maximizing the opportunistic throughput when there are different source of randomness like random link failures and noise quantization or when the activity of macro-users is not known by FAPs (coordinated channel sensing or modelling the activity). Additionally, a genetic-based resource allocation is investigated, providing centralized and decentralized algorithms, to which the Game Theory solutions are challenged. In all cases, the techniques derived require modifications of the current LTE-A standard which are identified. Finally, some of those algorithms have been evaluated in a realistic corporate scenario elucidating the advantages of coordinated resource allocation techniques proposed.

In this paper, we present a fixed mmWave Multi-User Multiple-Input Multiple-Output (MIMO) system for fixed wireless access with a unique architecture. A digital MIMO system is combined with an analog multi-beam antenna array which uses a high-dimension 16x16 Butler matrix to obtain 16 orthogonal beams. A system model of this architecture is presented and used to simulate its performance comparing to the performance of common-used patch antennas. Several MIMO precoding techniques are considered and compared with basic analog beamforming. To verify these results, a prototype is built and a dedicated measurement campaign is performed. The results show that the system model is a good approximation and that the use of the multi-beam antenna array is a good alternative to patch antennas for a large number of users.

Extensive use of mobile applications throws many challenges in cellular systems like cell edge throughput, inter cell interference and spectral e�ciency. Many of these challenges have been resolved using Coordinated Multi-Point (CoMP), developed in the Third Generation Partnership Project for LTE-Advanced) to a great extent. CoMP cooperatively process signals from base sta- tions that are connected to various multiple terminals (user equipment (UEs)) at transmission and reception. This CoMP improves throughput, reduces or even removes inter-cell interference and increases spectral e�ciency in the downlink of multi-antenna coordinated multipoint systems. Many researchers addressed these issues assuming that BSs have the knowledge of the common control channels dedicated to all UEs and also about the full or partial channel state information (CSI) of all the links. From the CSI available at the BSs, multiuser interference can be managed at the BSs. To make this feasible, UEs are respo...

The field of wireless communication is growing rapidly, with new requirements for the next generation of mobile and wireless communications technology. In order to achieve the capacities needed for future wireless systems, the design and implementation of advanced communications techniques such as multiantenna systems is required. These systems are realized by computationally complex algorithms, requiring new digital hardware architectures to be developed. The development of efficient and scalable hardware building blocks for realization of multiantenna algorithms is the focus of this thesis. The first part of the thesis deals with the implementation of complex valued division. Two architectures implementing a numerically robust algorithm for computing complex valued division with standard arithmetic units are presented. The first architecture is based on a parallel computation scheme offering high throughput rate and low latency, while the second architecture is based on a resource conservative time-multiplexed computation scheme offering good throughput rate. The two implementations are compared to an implementation of a CORDIC based complex valued division. The second part of the thesis discusses implementation aspects of fundamental matrix operations found in many multiantenna algorithms. Four matrix operations were implemented; triangular matrix inversion, QR-decomposition, matrix inversion, and singular value decomposition. Matrix operations are usually implemented using large arrays of processors, which are difficult to scale and consume a lot of resources. In this thesis a method based on the data flow was applied to map the algorithms to scalable linear arrays. An even more resource conservative design based on a single processing element was also derived. All the architectures are capable of handling complex valued data necessary for the implementation of communication algorithms. In the third part of the thesis, developed building blocks are used to implement the Capon beamformer algorithm. Two architectures are presented; the first architecture is based on a linear data flow, while the second architecture utilizes the single processing element architecture. The Capon beamformer implementation is going to be used in a channel sounder to determine the direction-of-arrival of impinging signals. Therefore it was important to derive and implement flexible and scalable architectures to be able to adapt to different measuring scenarios. The linear flow architecture was implemented and tested with measured data from the channel sounder. By analyzing each block in the design, a minimum wordlength design could be derived. The fourth part of the thesis presents a design methodology for hardware implementation on FPGA. v Abstract .

In wireless communication fading of channels is a serious cause of the received degraded signals. Orthogonal transmitter diversity such as time diversity and frequency diversity is quite simple to implement and, with optimum signal combining, can take full advantage of fading multipath channels. Receive diversity techniques like maximal ratio combining (MRC) have been popular means of introducing multiple antennas into communication systems. Space-Time Block Codes (STBC) that represent transmit diversity also exhibit similar complexity and performance as MRC. In this paper, we evaluated the performance of constellation rearrangement (CoRe), when used in conjunction with STBC coding is observed to improve the bit error rate of quadrature-amplitude modulation (QAM). CoRe is the process of finding a good bit to symbol mapping for each transmitting antenna, without changing the modulation level. A number of CoRe schemes have been proposed in the literature based on uniform QAM constella...

This paper proposes a statistical-eigenmode space-division multiple-access (SE-SDMA) transmission approach for a two-user downlink system where two transmit antennas are deployed at the base station and each mobile user has only one receive antenna, assuming that only statistical channel state information (SCSI) is available at the transmitter. By maximizing a lower bound of the ergodic signal-to-leakage-and-noise ratio (SLNR), the proposed SE-SDMA approach selects two users with orthogonal principal statistical eigen-directions and then transmits to each user along the corresponding eigenmode. For this approach, we derive an exact expression of the achievable ergodic rate, and compare it with the zero-forcing beamforming (ZFBF) system exploiting instantaneous CSI. We show that SE-SDMA can achieve the maximum ergodic sum-rate of the two selected users, and provide significant user selection gains. For comparison with ZFBF, we show that the rate gap between SE-SDMA and ZFBF with perfect CSI at the transmitter (CSIT) tends to zero in highly correlated channels. Further, when ZFBF is implemented with inaccurate CSIT, the operating regions of SE-SDMA and ZFBF are investigated for different ranges of signal-to-noise ratio (SNR), instantaneous CSIT accuracy levels, and spatial correlation levels. Numerical results confirm the analytically derived conclusions, and physical insights are provided.

This paper investigates the linear precoder design for K-user interference channels of multiple-input multipleoutput (MIMO) transceivers under finite alphabet inputs. We first obtain general explicit expressions of the achievable rate for users in the MIMO interference channel systems. We study optimal transmission strategies in both low and high signal-to-noise ratio (SNR) regions. Given finite alphabet inputs, we show that a simple power allocation design achieves optimal performance at high SNR whereas the well-known interference alignment technique for Gaussian inputs only utilizes a partial interferencefree signal space for transmission and leads to a constant rate loss when applied naively to finite-alphabet inputs. Moreover, we establish necessary conditions for the linear precoder design to achieve weighted sum-rate maximization. We also present an efficient iterative algorithm for determining precoding matrices of all the users. Our numerical results demonstrate that the proposed iterative algorithm achieves considerably higher sumrate under practical QAM inputs than other known methods.

This chapter look in to the way the Inter- symbol interference (ISI) has a significant challenge in communication systems, which adversely affect the data integrity and transmission efficiency. ISI arises majorly due to scattering nature of communication channels, where symbols overlap and collide with one another, thereby resulting to errors in signal detection. This phenomenon arises to be particularly pronounced in high-speed data transmission systems in which environments with multiples of propagation in involved such as wireless communication. A myriad of equalization techniques, not limited to Zero-forcing (ZF), Minimum Mean Square Error (MMSE), and Least Mean Square (LMS) adaptive equalizers, have been developed and refined over decades to mitigate ISI. Furthermore, this literature reviews delves much in to the principles, design methodologies and the performance of these equalizers based on recent researchers.

In this paper, it is shown that it is possible to use multiple-input multiple-output (MIMO) spatial multiplexing systems in aeronautical communications over an extended range even in the presence of a strong line-of-sight (LOS) component. Results originally derived to maximize the MIMO capacity in fixed range applications dominated by a LOS component is exploited to show that a high rank channel matrix may not only be offered for a fixed distance but can be maintained over an extended range and area in a MIMO ground-to-air communication system with n T = 2 transmit antennas (ground terminal) and n R ≥ 2 receive antennas (aircraft). Numerical results are presented for an n R × n T MIMO system in a Ricean fading channel assuming communication between a ground terminal and an aircraft in the en-route domain.

The continuous evolution in wireless communication, including fifth-generation (5G), tends to allow lower latency, higher data rates, and more energy efficiency. Fifth generation(5G) technology requires a highly precise approximation of the ‘channel state information' (CSI) to utilize the advantages of ‘massive multiple input multiple output' (Ma-MIMO) systems. Ma-MIMO has raised excessive interest in the industry of 5G communication, as it can efficiently raise the capacity of the communication system and lowering the transmitting power. In Ma-MIMO, 5G ‘orthogonal frequency division multiplexing' (OFDM) systems use pilot strings to identify channel behavior by following one of the traditional methods such as ‘least squares' (LS) or ‘minimum mean square error' (MMSE) estimation. However, in case of insufficient channel parameters (i.e., low signal to noise ratio), LS gives a poor estimation and MMSE requires statistical cognition of the channel parameters and noise in advance. This paper presents various approaches of deep learning-based framework used in deep neural network (DNN) architecture designed for 5G Ma-MIMO channel estimation.

Resumo: A Caatinga, bioma predominante do semiárido nordestino, com suas peculiaridades climáticas, apresenta uma alta diversidade florística. No entanto, o desmatamento devido às atividades relacionadas ao extrativismo e agropecuária vem ganhando dimensões preocupantes, comprometendo o equilíbrio ambiental. Diante disso, destacam-se os Sistemas Agroflorestais como um instrumento para recuperação de áreas degradadas. Notadamente nos SAF's se pratica os princípios da agroecologia. Neste sentido, este trabalho, objetivou listar por meio de levantamento bibliográfico, espécies vegetais com potencias usos para implantação de SAF's na caatinga, resultando em 102 espécies vegetais, identificadas em melíferas, madeireiras, alimentícios, fibra, forrageira, oleaginosas, ornamental, medicinal, e fixação de nitrogênio.

LTE networks are commonplace nowadays; however, comparatively little is known about where (and why) they are deployed, and the demand they serve. We shed some light on these issues through large-scale, crowd-sourced measurement. Our data, collected by users of the WeFi app, spans multiple operators and multiple cities, allowing us to observe a wide variety of deployment patterns. Surprisingly, we find that LTE is frequently used to improve the coverage of network rather than the capacity thereof, and that no evidence shows that video traffic be a primary driver for its deployment. Our insights suggest that such factors as pre-existing networks and commercial policies have a deeper impact on deployment decisions than purely technical considerations.

The paper explores the recent architecture evaluations and related issues and compares NISC (No Instruction Set Computer) features to those of CISC (Complex Instruction Set Computer) and RISC (Reduced Instruction Set Computer) processors. It has been observed that the complexities with embedded systems have increased manifold and the design community has been searching a suitable method that can handle such complexities with dual aims of (i) increased efficiency and (ii) reduction in time to introduce the product in the market that increase designer productivity without sacrificing the design quality. The paper presents a review of different processors and compares the variation in their utility and design

Le travail réalisé s’inscrit dans le contexte du développement des observatoires câblés de fond de mer. Il s’agit de dimensionner des dispositifs de capteurs sous-marins opto-alimentés, afin de développer des systèmes d’observation plus flexibles Dans ce contexte, nous avons proposé et testé une extension tout-optique qui permet la transmission conjointe de la puissance et des données sur une fibre optique unique. Ce dispositif nécessite la transmission de fortes puissances optiques pour recueillir une puissance électrique suffisante pour alimenter un capteur. La présence de forte puissance optique engendre la manifestation de phénomènes optiques dont les effets et leur interaction doivent être étudiés Nous souhaitons étendre cette étude à l'opto-alimentation de capteurs dans de nouvelles configurations (multicapteurs, réseau de capteurs). Ceci nous amène à compléter notre étude expérimentale en prenant en compte ces nouvelles configurations de réseaux opto-alimentés. Les résult...

The study was aimed at optimization of the use of sandbags for erosion control. Field studies were carried out in an experimental channel excavated on the slope of Otamiri River at Federal University of Technology Owerri and in a gully site at EzinihitteMbaise, Imo state. Artificial runoff was simulated into the artificial channel by pumping water from Otamiri River. Sandbags of various patterns and heights were placed across the channel to reduce the erosive power of runoff and encourage siltation. The flow characteristics including sediment concentration and sediment accumulation rates upstream were recorded. Comparative analysis of the patterns of placement of sandbags based on hydraulic and structural considerations showed that transverse arrangement with stepped downstream face yielded better results compared to longitudinal pattern. A chart for determining the optimum location of sandbags in gullies was developed to aid design.

Efficient and reliable video communication is required to maintain highquality and uninterrupted streaming in order to minimize bandwidth usage and to tackle network variability. Scalable Video Coding (SVC) introduces efficiency for video communication by introducing a base layer and a set of enhancement layers, while Unequal Error Protection (UEP) can provide high protection to important layers while having low redundancy for less important layers/bits/frames. Moreover, scalable video transmission's efficiency can be further improved by multicasting a video to multiple recipients simultaneously over a network efficiently, where each user can adapt to network conditions. As existing surveys do not concentrate on discussing the improving efficiency and reliability of video communication by multicasting scalable video communication focusing on UEP, we review these factors individually and in combination. We first gathered 113 original research studies using qualification criteria searched using electronic libraries, leveraging an elaborative process. As per the review, video scalability has been achieved using temporal scalability, spatial scalability with spatial resolution, quality scalability using quantization steps, and slice grouping for region of interest scalability, while UEP is achieved using transceiver, packet level, bit level, and cross-layer methods. Moreover, simulcast, multiple access techniques, multi-resolution modulation, and antenna heterogeneity have shown to be the promising SVC multicasting techniques. Review analysis shows that from reviewed work, 10.3% provide H.265-based scalability, 19.2% use transceiver UEP, and 7.7% use simulcast. Finally, we conclude our review by discussing the advantages and challenges of the concept of SVC-UEP video communication and then presenting guidance to overcome them.

The study search to understand the production process of agroecological farming family in District Pains, Santa Maria, RS. Then, we sought to understand the importance of family farming as a way of valuing community in social, economic and environmental. Furthermore, we tried to meet the changes in agricultural practices District Pains, highlighting alternative farming practices and sustainable benefits to the local community. The paper presents a qualitative approach where they were used as instruments of research interviews that have been applied to social subjects involved.

High spectral efficiency and low power consumption are the most challenging requirements of 5G networks since the number of devices are increased drastically. Media-based modulation (MBM) is a promising scheme in order to achieve these requirements. In this paper, the spectral efficiency of MBM scheme in single-and multi-user networks is studied. To find the spectral efficiency, information theoretical methods are used and tight lower-and upper-bounds are derived for the achievable rate. The performance of the system is studied for both correlated and uncorrelated constellation diagrams. It is shown that the entries of the constellation diagram for the sum rate region of multiuser case are always correlated. The characteristic of covariance matrix is derived and its impact on performance assessed.

In this paper we suggest to use the ASTC (Algebraic Space Time Codes) as powerful coding technique for IEEE 802.11x OFDM standard combined with PAPR reduction scheme. ASTC with their very Algebraic-construction based on Quaternionic algebra, have a full rate, full diversity, non-vanishing constant minimum determinant for increasing spectral efficiency, uniform average transmitted energy per antenna and good shaping, readily lend themselves to high data rate situations. However, by their construction they require a nonselective flat fading channels belonging to narrow-band systems. In fact, such systems are not readily found in airs interfaces. In open air we have what are commonly called frequency-selective fading channels. As a matter of fact, it becomes extremely necessary to harness their power for wide-band systems.

Future wireless communication systems can utilize the spatial properties of the wireless channel to enhance the spectral efficiency and therefore increases its channel capacity. This can be designed by deploying multiple antennas at both the transmitter side and receiver side. The basic measure of performance is the capacity of a channel; the maximum rate of communication for which arbitrarily small error probability can be achieved. The AWGN (additive white Gaussian noise) channel introduces the notion of capacity through a heuristic argument. The AWGN channel is then used as a basic building block to check the capacity of wireless fading channels in contrast to the AWGN channel. There is no single definition of capacity for fading channels that is applicable in all situations. Several notions of capacity are developed, and together they form a systematic study of performance limits of fading channels. The various capacity measures allow us to observe clearly the various types of r...

Die vorliegende Dissertation entstand während meiner Tätigkeit als wissenschaftlicher Mitarbeiter am Institut für Hochfrequenztechnik und Elektronik (IHE) des Karlsruher Instituts für Technologie (KIT). Mein Dank geht zunächst an Herrn Prof. Wiesbeck, Leiter des Instituts zum Zeitpunkt meiner Einstellung, dessen Unterstützung mir half mich professionell zu entwickeln. Weiter geht mein Dank an Herrn Prof. Zwick, der in den letzten zwei Jahren nicht nur für eine sehr gute Betreuung gesorgt hat, sondern darüber hinaus durch seine konstruktive Kritik als Hauptreferent zum Gelingen dieser Arbeit beigetragen hat. Ebenso danke ich Herrn Prof. Christoph Mecklenbräuker, Leiter des Institus für Nachrichtentechnik und Hochfrequenztechnik der Technischen Universität Wien, für die Übernahme des Korreferats. Außerdem möchte ich mich ausdrücklich bei der Firma KATHREIN Werke KG, ihren Mitarbeitern und besonders bei Herrn Prof. Roland Gabriel für die gute Zusammenarbeit bedanken, denn sie haben den Anstoß zu meiner Dissertation gegeben. Bedanken möchte ich mich auch bei Dr. Thomas Fügen für seine Hilfe bei der Einarbeitung in die Themen Mehrantennensysteme und MIMO, den vielen wertvollen Diskussionen und insbesondere für das Korrekturlesen der Dissertation. Diese Arbeit hätte ohne seine ausführliche Kritik und Unterstützung nicht den jetzigen Stand erlangt. Desweiteren möchte ich mich bei allen Kollegen bedanken, die sich oft Zeit für Diskussionen genommen haben und die für mich durch unsere Zusammenarbeit und gemeinsame Freizeitaktivitäten zu Freunden geworden sind. Ebenso geht mein Dank an alle Studenten, die sich mit mir fachlich weiterentwickelt und so aus mir einen anderen Menschen gemacht haben. Mein herzlicher Dank geht an meine Mutter, die mir durch ihre stetige Unterstützung jeden Tag leichter fallen lässt. Und mein letzter Dank geht an Kimberly, die aus meinem Leben eine Begegnung mit der Freude gemacht hat. Karlsruhe, im Februar 2010

A triple‐band multi‐input multi‐output (MIMO) antenna is presented.The proposed antenna consists of a C‐shaped monopole antenna that provides dual‐band resonant antenna. By protruding an L‐shaped parasitic strip on the ground plane, a third band as well as enhancement of the isolation between two ports in MIMO array is achieved. The proposed antenna can cover 2.1–2.6, 3.3–4, and 5.4–6 GHz, which are allocated for WLAN and WiMAX applications. The proposed triple‐band antenna structure is used in different two‐element MIMO arrays. Simulation results show that the S11, S12, and S22 of the MIMO arrays are independent of the position of the two‐element. The results show good S‐parameters, high peak gain and radiation efficiency, and stable radiation patterns among the triple‐band coverage. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1321–1325, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26799

This article presents an antenna with compact and simple geometry and a low profile. Roger RT6002, with a 10 mm × 10 mm dimension, is utilized to engineer this work, offering a wideband and high gain. The antenna structure contains a patch of circular-shaped stubs and a circular stub and slot. These insertions are performed to improve the impedance bandwidth of the antenna. The antenna is investigated, and the results are analyzed in the commercially accessible electromagnetic (EM) software tool High Frequency Structure Simulator (HFSS). Afterwards, a two-port multipleinput-multiple-output (MIMO) antenna is engineered by orthogonalizing the second element to the first element. The antenna offers good value for mutual coupling of less than -20 dB. The decoupling structure or parasitic patch is placed between two MIMO elements for more refined mutual coupling of the proposed MIMO antenna. The resultant antenna offers mutual coupling of less than -32 dB. Moreover, other MIMO parameters like envelop correlation coefficient (ECC), mean effective gain (MEG), diversity gain (DG), and channel capacity loss (CCL) are also studied to recommend antennas for future applications. The hardware model is fabricated and tested to validate the results, which resembles software-generated results. Moreover, the comparison of outcomes and other important parameters is performed using published work. The outcome of this proposed work is performed using already published work. The outcomes and comparison make the presented design the best option for future 5G devices.

With 5G (Fifth generation) cellular communications, systems have to be able to cope with a massive increase of mobile devices and services and simultaneously improve the system's spectral efficiency, as well as dealing with high interference levels. Base Station (BS) cooperation architectures jointly with block transmission techniques, such as OFDM (Orthogonal Frequency Division Multiplexing) for the downlink and SC-FDE (Single-Carrier with Frequency-Domain Equalization) for the uplink, are proven to be suitable for broadband wireless transmission systems. In BS cooperation systems MTs (Mobile Terminals) in adjacent cells share the same physical channel allowing the reducing of the frequency reuse and improving the spectral efficiency of cellular systems. In this paper we present a set of multiuser detection techniques for the uplink transmission in clustered architectures based on the C-RAN (Centralized-Radio Access Network) concept. We consider BS cooperation systems employing a universal frequency reuse approach. Our performance results demonstrate that by employing clustered techniques for the detection procedure it is possible to reduce substantially the signal processing complexity and the side information that must be transmitted by the backhaul structure.

Pre-processing techniques employed at the transmitter side of multiple-input, multiple-output (MIMO) systems, such as the ones used by MIMO singular value decomposition (SVD) (MIMO-SVD) techniques, can lead to signals with large envelope fluctuations and high peak-to-average power ratio (PAPR). For this reason, we can have amplification difficulties and increased sensitivity to nonlinear distortion effects. In this work, we consider MIMO-SVD schemes with strong nonlinear distortion effects. It is shown that contrarily to what one could expect, the asymptotic optimum performance of the MIMO system with strong nonlinear distortion effects can be much better than the optimum performance with an ideal, linear transmitter. 1

The performance of smart antenna system greatly relies on the beam forming technique that forming the main lobe beam pattern to the desired user direction and place null in the direction of undesired interference source. This paper investigates the implementation of Minimum Variance Distortionl ess Response (MVDR) Adaptive Beam-Forming (ABF) algorithm on Rectangular Antenna Array (RAA) is discussed and analyzed. The MVDR ABF technique performance is studied in accordance with varying the number of array elements, spacing between the array element s, the number of interference sources, noise power label, and the number of snapshots. The MVDR performance is compared on the basis of output radiation pattern and SINR. Computer simulation results show that the performance of the MVDR improved as the number of elements get more. This mean MVDR strongly depends on the number of the element. 0.5λ is considered the best spacing between adjacent antenna elements, the performance degraded as t...

The characterization of the global maximum of energy efficiency (EE) problems in wireless networks is a challenging problem due to its nonconvex nature in interference channels. The aim of this work is to develop a new and general framework to achieve globally optimal power control solutions. First, the hidden monotonic structure of the most common EE maximization problems is exploited jointly with fractional programming theory to obtain globally optimal solutions with exponential complexity in the number of network links. To overcome this issue, we also propose a framework to compute suboptimal power control strategies characterized by affordable complexity. This is achieved by merging fractional programming and sequential optimization. The proposed monotonic framework is used to shed light on the ultimate performance of wireless networks in terms of EE and also to benchmark the performance of the lower-complexity framework based on sequential programming. Numerical evidence is provided to show that the sequential fractional programming achieves global optimality.

Since 2003 the number of mobile phone subscribers extraordinary increased in Iraq. All over the world there is a tremendously growing in cellular communication systems resulted in increasing the number of mobile phones and mobile base stations. This distribution of mobile base stations in dense populated areas, near schools and hospitals has raised the public concern about possible health hazards. The ministry of environment/ Iraq in 2010 has set guidelines to perform measurements of the electromagnetic fields radiated from base stations used in mobile phone networks. In this study the electromagnetic power density radiated from mobile base station (downlink) and mobile phones to base station (uplink) were measured by TEMS software. This tool simplifies the prediction and measurement of electromagnetic power density. The measurements were conducted within 300 meters from the mast of the major GSM service provider in Kirkuk city. The obtained data were analyzed for uplink and downlink. The measured values then were compared with the antenna prediction pattern and with the employed safety guidelines to ensure compliance with these limits. All the measured values were within the limits.

Spatial Data Focusing Using Direct Sequence Spread Spectrum Modulation by Michael Derrick ODHIAMBO This work proposes the implementation of Spatial Data Focusing (SDF) using spread spectrum techniques. SDF was recently proposed as a candidate alternative to classical power focusing schemes in wireless geocasting applications. Unlike power focusing approaches where radiated power is directed to a defined direction, in SDF, it is the data to be transmitted that is processed in such a manner that it can only be decoded at a predefined location. This work exploits the dual orthogonality due to classical quadrature components and orthogonal Gold spreading sequences to design the IQ and spread spectrum based spatial data focusing (DSSS-SDF-IQ) scheme. It is demonstrated that SDF attains better spatial selectivity than classical power focusing for a given antenna array size. The robustness of the proposed scheme is subsequently demonstrated by implementing it over a classical Urban Canyon 6-ray multipath channel model, where it is shown that the scheme can exhibit beamwidth as narrow as 1 • with only a 4-antenna array. In SDF, the beamwidth is defined as the area within which data can be decoded as opposed to classical half power beamwidth.

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