Thèses sur le sujet « Partial CSIT »

Avec la progression de l'utilisation des smartphones, les modèles de systèmes ont rapidement évolué pour répondre aux besoins croissants en terme de capacité dans les réseaux sans fil. En effet, les progrès technologiques ont été considérables, depuis les communications point à point mono-utilisateur et mono-antenne jusqu'aux réseaux cellulaires multi-cellules et multi-antennes. Depuis la 3G, la technologie MIMO (multiple-input multiple-output) pour les communications sans fil est désormais intégrée aux normes de la large bande sans fil. L'ajout de plusieurs antennes, tant du côté de l'émetteur que du côté du récepteur, permet le multiplexage spatial (c'est-à-dire l'envoi simultané de plusieurs flux de données), qui permet d'augmenter les débits de données, et l'exploitation de la diversité spatiale, améliorant considérablement la qualité des liaisons. MIMO Multi-Utilisateurs (MU) a été un sujet bien étudié dans le domaine des communications sans fil en raison du grand potentiel qu'il offre pour améliorer le débit du système. Par conséquent, différents critères de conception pour les communications MIMO MU ont été étudiés dans la littérature. La plupart des conceptions de liaisons descendantes prennent en compte les problèmes d'optimisation de la capacité totale de tous les utilisateurs. D'autre part, la principale limitation des communications sans fil modernes est l'interférence (intracellulaire et intercellulaire) due à la réutilisation des fréquences. Ainsi, dans un scénario MIMO MU, lors de l'optimisation de l'efficacité globale, l'allocation de puissance se concentre sur les bons canaux, c'est-à-dire que les utilisateurs soumis à une forte interférence (e.g., les utilisateurs en bordure de cellule) sont délaissés. Il en résulte une répartition inéquitable de puissance entre les utilisateurs. Pour pallier ce problème, différentes notions d'équité sont introduites, comme l'équité max-min, l'équité pondérée ou l'équité proportionnelle. Dans cette thèse, nous nous concentrons sur l'équité max-min pondérée. En particulier, nous étudions le problème de l'équilibrage du débit pondéré par utilisateur dans un système MIMO multi-cellules MU. Nous abordons ce dernier dans le cadre d'une formulation conjointe du problème de beamforming et d'allocation de puissance, visant à satisfaire l'exigence d'équité. Dans la première partie, nous considérons la connaissance parfaite du canal pour résoudre le problème. Dans ce cas, nous maximisons le débit minimum pondéré via i) la dualité liaison montante/descendante et ii) la dualité Lagrangienne. Dans la deuxième partie, nous considérons la connaissance partielle du canal. Nous optimisons le problème d'équilibrage de débit ergodique via i) l'erreur quadratique moyenne pondérée (EQM) en exploitant la relation débit - EQM, et ii) deux approximations du débit estimé comme le débit de signal et de puissance d'interférence estimés (ESIP) au niveau du flux et du signal reçu. Par ailleurs, nous proposons une stratégie d'efficacité énergétique au moyen des approches d'équilibrage des débits proposées
With the rise in smartphone usage, the system models have rapidly evolved to meet ever-growing needs for capacity in wireless networks. Indeed, there have been large advances in technology, from single-user single-antenna point-to-point communications to multi-cell multi-antenna cellular networks. In fact, multiple-input multiple-output (MIMO) technology for wireless communications is now incorporated into wireless broadband standards since 3G. Adding multiple antennas at both the transmitter and the receiver sides enables spatial multiplexing (i.e. sending multiple data streams simultaneously), which allows to increase data rates, and spatial diversity exploitation, which allows to greatly improve link quality. The multi-user MIMO downlink (so-called Broadcast Channel (BC)) has been a well investigated subject in wireless communications because of the high potential it offers in improving the system throughput. Therefore, different design criteria for multi-user MIMO communication have been investigated in the literature. Most of the downlink designs consider optimization problems w.r.t. the sum-capacity of all users. On the other hand, the major bottleneck of modern wireless communication is the interference (intracell and intercell) due to frequency reuse. Thus, in a multi-user MIMO scenario, when optimizing the overall efficiency, the power allocation is focused on the good channels, i.e., users that are subject to strong interference (e.g. cell-edge users) are neglected. The result is an unfair distribution of rate among users. In order to avoid this effect, different fairness notions have been introduced, like max-min fairness, weighted fairness, or proportional fairness. In this thesis, we focus on the weighted max-min fairness. In particular, we study the (weighted) user rate balancing problem in a multi-cell multi-user MIMO system. We address this problem by joint beamforming and power allocation optimization, aiming to satisfy the fairness requirements. In the first part, we consider perfect knowledge of the channel to solve the problem. Therein, we maximize the minimum (weighted) rate via i) weighted user Mean Square Error (MSE) uplink/downlink duality and ii) Lagrangian duality. In the second part, we consider partial knowledge of the channel. We optimize the ergodic rate balancing problem via i) weighted expected MSE by exploiting the rate – MSE relation, and ii) two approximations of the expected rate as the Expected Signal and Interference Power (ESIP) rate at the stream level and the received signal level. Furthermore, we study the transmit power minimization problem with fixed user-rate targets and provide a strategy exploiting the proposed rate balancing approaches

In this paper, we analyze the four-node relay wiretap channel, where the relay performs amplify-and-forward. There is no direct link between transmitter and receiver available. The transmitter has multiple antennas, which assist in securing the transmission over both phases. In case of full channel state information (CSI), the transmitter can apply information leakage neutralization in order to prevent the eavesdropper from obtaining any information about the signal sent. This gets more challenging, if the transmitter has only an outdated estimate of the channel from the relay to the eavesdropper. For this case, we optimize the worst case secrecy rate by choosing intelligently the beamforming vectors and the power allocation at the transmitter and the relay.

Thesis (Ph. D.) -- University of Maryland, College Park, 2008.
Thesis research directed by: Dept. of Electrical and Computer Engineering . Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

This thesis investigates a decode-and-forward two-hop relaying system consisting of one source, one relay and one destination, in which orthogonal frequency division multiplexing is used. The relay forwards the message received from the source on a subset of available subcarriers in the second time slot. Firstly, a subcarrier pairing and selection algorithm is proposed, assuming that perfect channel state information (CSI) is available at all nodes, then, power is allocated to both the source and relay stations under individual power constraints in order to maximize the capacity. Secondly, subcarrier selection and pairing, and power allocation (PA) under partial CSI assumption along with individual power constraints are addressed. The result is a novel distributed algorithm with low complexity maximizing the expected value of capacity at the source and relay nodes. Finally, the simulation results show that selective relaying combined with subcarrier pairing and PA improves the system capacity to a considerable extent in both perfect and partial CSI cases.

This thesis explores a recently developed concentrated solar thermal (CST) central receiver technology, known as the solid particle receiver (SPR). Calculations of long and near term thermo-economic competitiveness for promising potential applications were preformed, for the first time within the Australian context. With these results, the most suitable SPR technology configurations and technical developments, required to reach the commercial potential, were identified. An innovative simulation tool which included a variety of different thermodynamic and economic models, was developed to compute the annual performance of solar SPR systems. This simulation tool was then applied to design and to optimise CST SPR tower systems based on hourly simulations utilising meteorological data, the NREL Solar Position Algorithm, solar field efficiency matrices generated by DLR software HFLCAL, as well as a mathematical SPR model for calculating receiver efficiency. The SPR model was calibrated using results from DLR receiver prototype tests. To allow economic assessment of the entire SPR system, a financial model was implemented within the tool and detailed CST component costs were generated. The optimisation process utilised in the CST tower system design is more detailed than typical for a research project, since it adds a new degree of freedom when optimising the receiver and solar field. By decoupling the connection between solar field and receiver, the energy delivered from the solar field relative to the design receiver power becomes an additional optimisation variable. Applications of SPR systems for electricity production and industrial process heat generation have been identified for the Australian market. Promising heat supply uses of SPR technology examined in this thesis were: thermal enhanced oil recovery, preheating scrap metal during steel production, and solar augmentation of coal-fired steam power stations. Before this project, there were no detailed investigations on utilising SPR based CST power plants in Australia. This thesis has identified several potential applications, the required sub-components and system integration methods which should be further developed for commercialisation of this solar technology in the Australian market.

High-power microwave, HPM, systems can be used as non-lethal weapons with the ability to destroy or disturb electronics, by damaging internal circuits and inducing high currents. Today microwave sources are being developed with peak powers exceeding 1 GW, one of these devices is the vircator, a narrowband source which is unique to the HPM community. In order to understand and develop microwave sources like the vircator it is necessary to have computer models, as simulations gives an invaluable understanding of the mechanisms involved during operation, saving time and development costs.                                                                  This thesis presents the results from a theoretical analysis and a simulation study using a well known electromagnetic particle-in-cell code, Computer Simulation Technology Particle Studio. The results are then compared to measured data from a HPM system, the Bofors HPM Blackout. The results show that CST PS can be used to design and study the coaxial vircator with good results.

In this thesis a search for electron type neutrino-electron scattering cross-section and Weinberg Angle measurements were performed at KS Nuclear Power Station with 200 kg CsI(Tl) scintillating crystal detector located at a distance of 28 m from the 2.9 GW reactor core giving total flux of 6:52X10^12 cm^-2s^-1 in average at the experimental site. New analysis techniques and background suppression methods were developed. In the region of 3-8 MeV a measurement of SM cross section of (1:235+-0.577) XR_SM and Weinberg Angle of 0:264 +-0.075 which is quite consistent with the SM value of 0.23120(15)were obtained. These are the best results with wold wide level sensitivities at untested low energy region by using reactor anti-neutrinos.

碩士
國立臺灣大學
電信工程學研究所
105
In a previous work [1], multi-user beamforming design problem has been studied for frequency-division duplex (FDD) massive MIMO systems that uses only partial downlink (DL) channel state information at transmitter (CSIT), which requires very little overhead for CSI acquisition, under a total power constraint, where the partial CSIT is in the form of DL angles of departure(AoDs) and the amplitudes of the strongest paths of each user equipment(UE). In this thesis, we consider the problem under an additional per-antenna power constraints (PAPCs) criterion, which makes the problem more practical especially when cost on power amplifiers (PAs) is of concerns. And New relaxation techniques are developed toward the goal to solve the new problem with PAPC. On the whole, not only the feasibility of FDD massive MIMO systems is greatly enhanced but low-cost antenna elements are required. Simulation results show the effectiveness of the proposed method and verify that the PAPCs only cause a very slight performance decrease compared to total power constraints. Afterwards, we analyze the beamforming designs of this and previous work, and the feasibility of the optimization problem solving the beamformers. Due to the lack of full CSIT, base station (BS) has to excessively limit and narrow the feasible set of potential candidate of beamformers that might have stronger equivalent channel gains. So we found that beamforming designs with PAPCs fail if no surplus of spatial degrees of freedom exists. Hence, we also introduce the correlation between uplink (UL) and DL channel. The BS can obtain the conditional probability density function of the magnitude of the DL path gains given the magnitude of UL path gains. A beamforming design with statistical CSI is considered to relax the constraints on the interference to release the feasible set of candidate beamformers from overly strict limits.

碩士
國立臺灣大學
電信工程學研究所
106
Large-scale antenna (LSA) holds a huge potential for the next-generation communication systems. However, the acquisition of full channel state information at transmitter (CSIT) becomes a big challenge when the scale of antenna arrays gets larger. Furthermore, conventional fully digital beamforming (FDB) requires a dedicated radio frequency (RF) chain for each antenna, which leads to high cost and critical power consumption in LSA. In this thesis, a hybrid beamforming (HB) design method in frequency-division duplex (FDD) LSA systems with partial CSIT condition is proposed. By exploiting the FDD channel reciprocity, partial CSIT can be acquired effectively. To avoid any user equipment (UE) experiencing poor quality of service (QoS), the fairness constraint is considered. Simulation results show that the proposed HB design can achieve nearly the same performance compare to that of the optimal FDB and less number of RF chain is needed. Meanwhile, the QoS is maintained for each UE.

碩士
國立臺灣大學
電信工程學研究所
104
In this thesis, we consider an effective acquisition mechanism of partial channel state information at the transmitter (CSIT) for frequency-division du- plex (FDD) massive MIMO systems, based on this phenomenon, we propose downlink beamforming methods. The partial CSIT is in the form of down- link angles of departure (AoDs) and the amplitudes of the strongest paths of each UE. By exploiting the reciprocity between downlink AoDs and uplink angles of arrival (AoAs), the partial CSIT can be acquired through down- link training and uplink feedback effectively. Therefore, the feasibility of FDD massive MIMO systems is greatly enhanced. However, in millimeter wave (mmWave) communication, due to the high cost and power consump- tion of high-bandwidth RF chains. Thus, in beamforming proposed methods, we not only propose the conventional fully-digital beamforming but also hy- brid beamforming. The proposed beamforming methods enable the BS to perform DL transmissions to multiple UEs simultaneously. Simulation re- sults demonstrate the superiority of the proposed methods compared to other methods in the sense of fairness and achievable sum rate in conventional fully- digital beamforming. In addition, in hybrid beamforming, we only use a few of RF chains that the proposed method can realize the conventional fully- digital beamforming.

碩士
國立臺灣大學
電信工程學研究所
100
In this thesis we consider the secure transmission over the fast fading multiple antenna Gaussian broadcast channel with confidential messages (FMGBC-CM), where a multiple-antenna transmitter sends independent confidential messages to two users with informa-tion theoretic secrecy and only the statistics of the receivers’ channel state information are known at the transmitter. We first use the same marginal property of the FMGBC-CM to classify the non-trivial cases, i.e., both the two users have nonzero rates. We then derive the achievable rate region for the FMGBC-CM by solving the channel input covariance matrices and the inflation factor. Due to the complicated rate region formulae, we also resort to low SNR analysis to investigate the characteristics of the channel. Finally, the numerical examples show that under the information-theoretic secrecy requirement both users can achieve positive rates simultaneously.

碩士
國立清華大學
電機工程學系所
106
In this work, we consider a heterogeneous cellular network (HCN) with a macrocell and multiple femtocells. In each femtocell, the femto base station (FBS) serves a femto user (FU), which is capable of simultaneous wireless information and power transfer (SWIPT) energy harvesting (EH) in a power splitting manner. All FBSs suppress their interference to macro users (MUs) via a interference power constraint. In such a HCN, we aim to maximize the energy efficiency (EE) of all femtocells via the joint design of beamforming and power splitting ratios under partial channel state information (CSI) - imperfect CSI and channel distribution information (CDI) at FBSs. For the imperfect CSI case, we consider the robust beamforming design that maximizes the worst-case EE for all femtocells under the quality-of-service (QoS) constraints and EH constraints. For the CDI case, we consider the problem of maximizing EE under rate outage constraints. The non-convex objective functions and constraints make the problem difficult to solve. To resolve this issue, We proposed successive convex approximation (SCA) algorithms (EE-SCA-1 for the imperfect CSI case and EE-SCA-2 for the CDI case) that provide high-quality approximate solutions. Simulations demonstrated that our proposed EE-SCA-1 and EE-SCA-2 achieve near-optimal performance for both the imperfect CSI and CDI cases. Furthermore, for the imperfect CSI case, our EE-SCA-1 improved EE by as much as 23.1% and 267.6% over the zero-forcing (ZF) scheme and a power minimization scheme. For the CDI case, our EE-SCA-2 improved EE by as much as 116.7% and 21.1% over the ZF scheme and a rate maximization scheme. It indicates that careful design of energy efficient beamforming scheme is essential for the next-generation wireless communication systems.

碩士
國立中山大學
通訊工程研究所
102
In recent years, wireless communication has been developed quickly, and the mobile network has proceeded to the fourth generation communication systems. The subscriber’s handheld devices are going to have higher quality services and faster transmission throughput. In the fourth generation partnership project, coordinated multi-point (CoMP) transmission technique has been proposed to enhance the signal quality of the Long-Term Evolution-Advanced (LTE-A) systems. Through coordination among multiple cells, e-NodeBs (eNBs) adjust corresponding transmit beamforming vectors in order to reduce co-channel interference as well as improve transmission throughput of users located at cell edge. Downlink coordinated multi-point transmission techniques can be classified into the joint processing (CoMP-JP) and coordinated beamforming (CoMP-CB). On the other hand, as the development of semiconductor, mobile devices become more powerful and are usually equipped with high quality panel, which consumes battery power faster. However, progress on the battery is not as faster as electronic devices. Thus, the technique of wireless energy transfer (WET) has been proposed to harvest energy and provides longer lifetime for the user’s devices. In the thesis, we consider a CoMP system where users need to receive information and harvest energy simultaneously. We focus on the design of beamforming vector to meet the requirement of energy harvesting and information detection. Taking implementation complexity into consideration, we propose a downlink CoMP-CB scheme where each user can operate under either energy-harvesting mode or energy-detection mode. By optimizing the beamforming vectors and selecting operation modes for users, the proposed scheme aims to maximize the harvested energy, subject to guaranteeing sum-rate constraints for those users in information-detection mode. Finally, we also consider the case of partial CSI, and design the beamforming scheme accordingly, in order to deal with the situation that perfect CSI is not available.

In preparation for the large backgrounds expected to be present in the Belle II detector from the SuperKEKB e+e- collider, the radiation hardness of several large (5 x 5 x 30 cm3) thallium doped cesium iodide (CsI(Tl)) scintillation crystals are studied. The crystal samples studied consist of 2 spare crystals from the Belle experiment using PIN diode readout and 7 spare crystals from the BaBar experiment using photomultiplier tube readout. The radiation hardness of the scintillation properties of the CsI(Tl) crystals was studied at accumulated 1 MeV photon doses of 2, 10 and 35 Gy. At each dose, the longitudinal uniformity of the crystals light yield, scintillation decay times, time resolution and energy resolution was measured. As the Belle II collaboration is considering an upgrade to pure CsI crystals if CsI(Tl) does not satisfy radiation hardness requirements, the scintillation properties of a pure CsI scintillation crystal were also measured and compared to the CsI(Tl) crystal measurements. In addition to experimental work, Monte Carlo simulations using GEANT4 were written to compare ideal pure CsI and CsI(Tl) crystals and to study the effects of radiation damage on the performance of the Belle II electromagnetic calorimeter.
Graduate

This dissertation investigates CsI(Tl) pulse shape discrimination (PSD) as a novel experimental technique to improve challenging areas of particle identification at high energy $e^+ e^-$ colliders using CsI(Tl) calorimeters. In this work CsI(Tl) PSD is implemented and studied at the Belle II experiment operating at the SuperKEKB $e^+ e^-$ collider, representing the first application of CsI(Tl) PSD at a $B$ factory experiment. Results are presented from Belle II as well as a testbeam completed at the TRIUMF proton and neutron irradiation facility. From the analysis of the testbeam data, energy deposits from highly ionizing particles are shown to produce a CsI(Tl) scintillation component with decay time of $630\pm10$ ns, referred to as the hadron scintillation component, and not present in energy deposits from electromagnetic showers or minimum ionizing particles. By measuring the fraction of hadron scintillation emission relative to the total scintillation emission, a new method for CsI(Tl) pulse shape characterization is developed and implemented at the Belle II experiment's electromagnetic calorimeter, constructed from 8736 CsI(Tl) crystals. A theoretical model is formulated to allow for simulations of the particle dependent CsI(Tl) scintillation response. This model is incorporated into GEANT4 simulations of the testbeam apparatus and the Belle II detector, allowing for accurate simulations of the observed particle dependent scintillation response of CsI(Tl). With $e^\pm$, $\mu^\pm$, $\pi^\pm$, $K^\pm$ and $p/\bar{p}$ control samples selected from Belle II collision data the performance of this new simulation technique is evaluated. In addition the performance of hadronic interaction modelling by GEANT4 particle interactions in matter simulation libraries is studied and using PSD potential sources of data vs. simulation disagreement are identified. A PSD-based multivariate classifier trained for $K_L^0$ vs. photon identification is also presented. With $K_L^0$ and photon control samples selected from Belle II collision data, pulse shape discrimination is shown to allow for high efficiency $K_L^0$ identification with low photon backgrounds as well as improved $\pi^0$ identification compared to shower-shape based methods.
Graduate