Sharif Digital Repository

To gain commercial competitive advantage in a constantly changing business environment, demand forecasting is very crucial for an organization in order to make right decisions regarding manufacturing and inventory management. The objective of this thesis is to propose a forecasting technique which is modeled by artificial neural-fuzzy networks. The effectiveness of the proposed approach to the demand forecasting issue is demonstrated using real-word data. Then we investigate a suitability of a decision-making model for airline route planning based on the so called “Game Theory”. The model is helpful to decide whether a new route is, in fact, needed. Different case studies reveal that... 

Switched Parasitic Antennas, as a kind of Smart Antennas, have several applications in Telecommunications and Radar systems. In the realm of wireless applications, these antennas provide the system with higher capacity owning to the fact that they are able to direct the main beam toward the desirable user. Moreover, they can be used to degrade the adverse effects of Multi-path. Multi-path reduction not only benefits mobile communication but applies to many applications of radar systems. These antennas, in addition, can be utilized in Direction Finding. In the case of other types of Smart Antennas, the above mentioned benefits can be achieved with high costs due to the fact that there are a... 

In this thesis, a simplified method was introduced to model the wave scattering by the metallic objects in a microcell, in order to determine the coverage pattern. First, the equivalent images method was introduced, which models the building walls effect. This method is fast, memory saving and accurate enough to estimate the scattered fields. Two-ray incidence model accuracy was investigated and confirmed in modeling the scattering from the metallic objects. This method also enhances saving in time and memory. The accuracy of single scattering assumption was investigated and confirmed in a scenario of multiple metallic scatterers. Based on this assumption, we can superimpose the scattered... 

Mars rover Curiosity is a mobile scientific laboratory which it’s mission is to assess the biological potential of the landing site and characterize the geology of the landing region. This rover communicate to a Mars orbiter named MRO satellite in the UHF band which relies the signals to the Earth stations. Also this rover communicate to the Earth stations directly in the X band. In this thesis, we determine the technical characteristics of stations and simulate Earth-Mars radio links. So we calculate :
1. determine the technical characteristics of Earth stations
2. determine the technical characteristics of satellite and Curiosity
3. Earth-Mars orbital position in the... 

In recent years due to the advances in semiconductor technology and the ability to implement small-scale manufacturing, communication at 60 GHz band receive more attention than ever has been. The use of this frequency band is not only about 7-9 GHz unlicensed broadband access provided, but getting smaller devices make it possible to use multiple antennas at the transmitter and receiver, and thus taking advantage of multiple input – multiple output systems. Antennas used in these systems should have features such as small size , low weight, high gain and bandwidth and also they should keep their high efficiency and gainat high frequency range (about a few GHz ). To achieve these features... 

Over the past few years , demand for wireless communication services have grown at a formidable rate. As such we need to find new ways to support more and more wireless users in a confined space. this means that the capacity of networks should be significantly increased to overcome formidable rate of subscribers growth. That is why the smart antennas have become very popular in communication systems. Smart antennas are a kind of adaptive antenna arrays with smart signal processing algorithms used to find direction of arrival(DOA) of the signal, and use it to calculate suitable weights to direct the antenna beam on the desired user and nulling interferences. In this thesis, DOA estimation... 

The main objective of this project is to discuss a DOA estimation system performance in a multipath environment. For this goal, first the basics of the DOA Estimation systems are discussed. Evaluation of different types of algorithms and choosing an appropriate one is an important step in this regard. Moreover the comparison of different array structures is necessary to choose the appropriate one. The major part of the project has been dedicated to discussion of multipath phenomenon as a major source of error in DOA estimation and studying the multipath mitigation algorithms to eliminate the aforementioned error. A model based on the concept of Bistatic Radar Cross Section is proposed to... 

In this thesis, some of the well-known DOA algorithms namely Bartlett, Capon, Linear prediction, Maximum Entropy, Pisarenko harmonic decomposition, Minimum norm and MUSIC are analyzed and compared with each other in the identical situations using a uniform linear array. Then based on these comparisons, the appropriate algorithm is selected. In the next step since the linear arrays can't estimate both angles of arrival (Azimuth and Elevation) simultaneously, two dimensional (2D) geometries are introduced and are also compared to each other. Then one of them (circular array) is selected for dipole antenna arrays. The performance of the selected array is evaluated using isotropic elements for... 

In the new generations of mobile communication systems, smart antennas are used to achieve higher capacities. Since these systems have the ability to form a radiation pattern where the desired signal is received with minimum distortion and inteferers are received with a significant attenuation therefore their application makes it possible to have a large signal to inteference ratio. In addition by setting the main beam direction towards the desired signal, it is conceivable to realize the the communication with a lower power. The optimal methods for angle-of-arrival estimation and beamforming in one and two dimensional structures has been studied in the literature, but the three dimensional... 

Multiple-Input Multiple-Output (MIMO) communications at millimeter-wave (mm-wave) frequencies (e.g., in the 60 GHz band) is a modern technology recently considered for various applications, such as emerging 5G services for multi-user MIMO (MU-MIMO) and high-resolution frequency-modulated continuous wave (FMCW) MIMO radars to support multi-gigabit throughputs in short-range environments via spatial multiplexing-diversity. Nevertheless, the impairments of communication channels in this frequency band, including significant propagation loss and severe blockage effect, are quite challenging to allow an efficient communication link. Hence, beamforming/beam steering can play a crucial role in 60... 

The interferometer method, as one of the most accurate schemes for wideband direction finding (DF), is used. The interferometer method has various algorithms which can be implemented depending on the required specifications. The advantages and disadvantages of these algorithms have been evaluated and the appropriate algorithm for a general practical case in view of the ambiguity resolution is proposed. The receivers’ channel phase tracking error is of significant concern in practice, in interferometric DF systems. The induced error due to channels phase tracking error is estimated. Furthermore the use of physically realizable antennas, achievement of high accuracy, minimum number of antennas... 

Novel two dimensional and three dimensional antenna array geometries for smart antenna application are introduced. MMSE beamforming algorithm, using these arrays, in presence of signal, noise and interferences is implemented. Beamforming approach is used for every type of array assuming uniform and log-normal distributions for the interference amplitudes. Equal volume cylindrical or prism type arrays with circular, hexagonal, triangular, square and star cross sections with equal number of elements are considered for comparison. Novel geometries consisting of rotated cross sections are studied as well. In each case the relative SIR’s are compared in these geometries, showing that the... 

For a manned space mission to Mars, one of the essential requirements is to have a two-way, uninterrupted communication link.Three Mars Synchronous Satellites (MSS), are proposed to ensure the telecommunication link in all locations on Mars (except its poles) at any time. At any given moment, at least two of the three satellites (MSS) is connected to the Deep Space Communication Complex (DSCC) (NASA Earth Station). But the use of MSS satellites is not adequate during the periods of solar conjunction and solar opposition. Due to the fact that the sun blocks or weakens the receiver signal, a solar orbiting satellite (SOS) is proposed to maintain the communication link at this condition....