Detection techniques for alternate-relaying cooperative communications systems

Cooperative technology constitutes a breakthrough in the design of wireless communication systems. This is due to its relatively simple implementation and its significant performance gains in terms of link reliability, system capacity, and transmission range. In cooperative communications, multiple terminals in a network cooperate by relaying each other’s information, forming a virtual antenna array, and, thus realizing spatial diversity in a distributed fashion. It is not surprising that cooperative communications have become a strong candidate for many wireless applications, such as cellular networks, wireless local area network, mobile ad-hoc networks, and wireless sensor networks. However, cooperative technology is not without challenges. A major problem in this technology is the reduction in spectral efficiency, which results from the half-duplex constraint at the relays and orthogonal relay transmission. This has spurred researchers to investigate cooperative strategies to recover the spectral efficiency loss. Such strategies can be classified into three main categories. One category supposes that each source transmits a ’superimposed’ signal, which consists of its own data and relaying information. This superposition can be performed in code or in modulation domain. Obviously, if the relay does not have its own data, a full-rate transmission can not be achieved. The second category is to employ adaptive modulation techniques where the spectral efficiency is improved by changing modulation size with fixed symbol rate. However, the transmitter needs to know the channel signal-to-noise (SNR) such that the best suitable modulation is chosen and the receiver must be informed on the used modulation in order to decode the information. This leads to an increased overhead in the system as compared with a fixed modulation system, and will increase the complexity of the receiver too. The third one utilizes two-relay, which alternatively transmit and receive. A key feature of this category is that the source continues to transmit data, while the two relays take turns in receiving and transmitting the data from the source. Due to the simultaneous transmission of the data streams through both direct and one of relay channels, harmful interference occurs at the relays and destination. The interference occurred at the relays and destination represents a drawback in this case, though. According to our best knowledge, no previous research was done to develop the optimal detectors for alternate-relaying cooperative (ARC) systems. Further, all the previous works for ARC systems have in common that they do not exploit any properties of the underlying error correcting codes. It is therefore necessary to propose optimal detection techniques for uncoded and coded two-relay systems. This motivated us to do this research. In this thesis, we proposed optimal and suboptimal detectors to mitigate the influence of the interference signal for the uncoded and coded decode-and-forward (DF) ARC systems

Autonomous Navigation for an Unmanned Aerial Vehicle by the Decomposition Coordination Method

This paper introduces a new approach for solving the navigation  problem  of Unmanned Aerial  Vehicles (UAV) by studying its rotational and  translational dynamics and  then solving the nonlinear model by the Decomposition  Coordination method. The objective is to reach a destination goal by the mean of  an autonomous  computed   optimal path calculated   through optimal control sequence. Solving such complex systems often requires a great  amount of computation. However, the approach considered herein is based on  the Decomposition Coordination principle, which allows the nonlinearity to be treated at  a local level, thus offering a  low computing time. The stability of the method is discussed with sufficient conditions for convergence. A numerical application is given in consolidation  the theoretical results

A Reactive Path Planning Approach for a Four-wheel Robot by the Decomposition Coordination Method

In this paper, we discuss the problem of safe navi- gation by solving a non-linear model for a four-wheel robot while avoiding the upcoming obstacles that may cross its path using the Decomposition Coordination Method (DC). The method consists of first, choosing a non-linear system with the associated objective functions to optimize. Then we carry on the resolution of the model using the Decomposition Coordination Method,  which allows the non-linearity of the model to be handled locally and ensures coordination through the use of the Lagrange multipliers. An obstacle-avoidance algorithm is presented thus offering a collision-free solution. A numerical application is given to concert the efficiency of the method employed herein along with the simulation results

Dual formulations for optimizing Dec-POMDP controllers

Decentralized POMDP is an expressive model for multi-agent planning. Finite-state controllers (FSCs)---often used to represent policies for infinite-horizon problems---offer a compact, simple-to-execute policy representation. We exploit novel connections between optimizing decentralized FSCs and the dual linear program for MDPs. Consequently, we describe a dual mixed integer linear program (MIP) for optimizing deterministic FSCs. We exploit the Dec-POMDP structure to devise a compact MIP and formulate constraints that result in policies executable in partially-observable decentralized settings. We show analytically that the dual formulation can also be exploited within the expectation maximization (EM) framework to optimize stochastic FSCs. The resulting EM algorithm can be implemented by solving a sequence of linear programs, without requiring expensive message-passing over the Dec-POMDP DBN. We also present an efficient technique for policy improvement based on a weighted entropy measure. Compared with state-of-the-art FSC methods, our approach offers over an order-of-magnitude speedup, while producing similar or better solutions

Value of Atrial Fibrillation Prophylaxis after Coronary Artery Bypass Graft Surgery

Background: Heart surgery patients who develop acute and new-onset AF (postoperative atrial fibrillation, POAF) are among the most common postoperative complications, affecting around 35 percent of those who undergo the procedure. Objective: To assess the effectiveness of amiodarone in prophylaxis of AF post coronary artery bypass surgery (CABG). Patients and Methods: Our work represents a randomized clinical trial, which was carried out at National Heart Institute and Zagazig University from the period of August 2020 to June 2021. 68 patients, admitted for CABG and had high risk score according to POAF score, were included in our study. Results: Regarding mean left ventricular ejection fraction (LVEF), in group I was 47.52±5.85 while in group II it was 49.85±6.25. There was a statistically non-significant difference between the groups with a P value of 0.414. Mean Intensive Care Unit (ICU) period was 4.42±1.35 in group I, and group II was 2.73±0.95. The difference between the groups was statistically significantly shorter among group II (prophylaxis group) (P <0.01). Regarding development of POAF, in group I, the incidence of POAF was 85.3% while in group II, it was 38.2%. Difference among the two studied groups was statistically significantly lower in the group II (prophylaxis group). Conclusion: A prophylactic amiodarone strategy dramatically decreased incidence of POAF risk. All previous estimations of POAF risk reduction using prophylactic amiodarone were found to be accurate. Amiodarone was more effective in preventing postoperative atrial fibrillation with no serious side effects and it decreased postoperative ICU stay

Synthesis and antitumor activity of novel pyrazolo[1,5-a]pyrimidine derivatives

A novel series of pyrazolo[1,5-a]pyrimidine-3-carbonitriles substituted with 7-amino, 7-substituted amino and 5-substituted amino groups was synthesized. Some of the newly synthesized compounds were tested in vitro on human colon tumor cell line (HCT116). Compound 14a displayed the highest activity among the tested compounds with IC50 that equals to 0.0020 μM

Dual-band multiple-element MIMO antenna system for next-generation smartphones

This work presents a cost-effective multiple-element multiple-input multiple-output (MIMO) antenna system for next-generation smartphones. The proposed antenna system is developed on a 0.8 mm thin FR-4 substrate with a relative permittivity of 4.4, which consists of one main board and two sideboards. The dimensions of the main board and the two side boards are 150 × 75 mm2 and 150 × 6 mm2, respectively. The radiating elements are printed on the sideboards to provide space for other radio frequency (RF) components to be embedded on the main board. The proposed antenna resonates at two distinct allotted 5G bands, i.e., 3.5 GHz and 5.4 GHz, with impedance bandwidths of 200 MHz and 700 MHz, respectively. The isolation between the antenna elements is noted to be >18 dB and >12 dB for the 3.5 GHz and 5.4 GHz frequency bands. In addition, the proposed MIMO antenna provides pattern and spatial diversity characteristics in both bands with good gain and efficiency. Furthermore, the MIMO parameters such as envelope correlation coefficient (ECC), mean effective gain (MEG), and channel capacity (CC) are calculated, and it is observed that the MIMO antenna offers good diversity performance for the bands of interest. A prototype is fabricated and measured to verify the numerical data. The simulated results were discovered to be in excellent agreement with the measured results. It is also observed that the proposed MIMO antenna system holds promising features, and can be utilized for future generations of smartphones.Princess Nourah bint Abdulrahman Universit