ble two-port measurements of the multi-port so that the scat- tering parameters of the multi-port can be identified. An easy method is to connect all ports of the multi-port which are not connected with the network analyzer to a match. In this case the scattering parameters can directly be determined by the two-port measurements. But in fact, it is often not pos- sible to connect all ports to a match, for example if non- contacting measurements are performed. Furthermore the available matches might not be accurate enough, especially in the range of higher frequencies. Thus, another method which is independent of the external reflections has to be de- veloped. The following article describes different methods to evaluate a multi-port by using a two-port network ana- lyzer and unknown external reflections. Finally a very gen- eral method to evaluate any multi-port is described, which so far has proven to be successful in all cases considered.
A microwave reflectometer is an instrument to measure a complex ratio between reflected and incident waves at an input port of a uniform transmission line terminated in a Device Under Test (DUT). The conventional reflectometer is formed by a four-port network with two ports connected to a microwave source and DUT, and the remaining ports coupled to a heterodyne receiver which acts as a Complex Ratio Detector (CRT). By using the heterodyne receiver technique, the two microwave signals are converted in the linear manner to an Intermediate Frequency (IF) of hundreds of kHz where they are processed using digital means. The use of the heterodyne technique enables a very large dynamic range of 100 dB or more for this type of reflectometer. However, as the ratio of two original microwave signals has to be preserved at IF, a very advanced electronic circuitry is required to accomplish the linear conversion process. This complicated electronics leads to a large size of the conventional reflectometer and its high price tag. Many applications require compact- size and low-cost reflectometers. They can be built using N-portnetworks, with N being greater than 5, equipped only in scalar (power) detectors. This chapter describes the concept of a multi-port reflectometer which employs scalar instead of complex ratio detector to determine the complex reflection coefficient of DUT. It is shown that such a device requires a suitable calibration and mathematical transformations of the measured power at selected ports of the N-port to obtain the complex reflection coefficient of DUT. Because of this requirement, the multi-port reflectometer uses a computer to perform calibrations and measurements. The use of a computer accelerates the calibration and measurement procedure and at the same time it does not create a considerable overhead to the total cost of this measurement instrument. The challenge is to obtain a low-cost fully integrated N-port network operating over an ultra wide frequency band, which can be used to develop a fully operational reflectometer. This challenge is addressed in the present chapter. Practical configurations of this measurement instrument are described and the design of a compact fully integrated N-port network in microstrip-slot technique to build a reflectometer operating over an ultra wide microwave frequency band of 3.1 to 10.6 GHz is given.
A Crossover is a matched 4-port passive device. This device allows two signals to cross each other, ideally, with inﬁnite isolation. When the two signals are to cross each other, an air-bridge or an underpass could be used for this purpose. But, a microstrip crossover is a planar solution that is easier to fabricate and incur a reduced cost [1, 2]. This component has become very signiﬁcant considering its potential application in a Butler matrix utilized in antenna beamforming for the upcoming 5G wireless communication technologies . In view of the recent trends in multi-band components [4–6], there is a renewed interest in the analysis and design of dual-frequency crossovers [2, 3, 7, 8]. On the other hand, utilization of additional two-port network dates to 1976, when it was ﬁrst reported as a methodology to enhance bandwidth of the conventional directional coupler . Later, its application was shown in achieving dual-frequency behavior in coupler and power dividers [9, 10]. Despite many recent interesting attempts leading to realization of multiple channels and wideband crossovers [11–13], the port-extension technique could not get attention in the case of crossovers. A relatively more complex structure of a crossover is a hindrance to any such eﬀort. Therefore, this paper presents a technique leading to a much more simpliﬁed analysis of port-extended crossovers formulated in the form of a general rule. This rule is further invoked in the analysis of a new dual-frequency crossover employing a transmission-line section as a port-extension network.
In Eq. (2), concat is a connecting function. The feature is connected by different scales to a larger dimension. In Eq. (3), the feature is composed of the sum of the corre- sponding pixel of the different scale feature maps. The structures of the multi-scale separable convolutional unit are shown in Fig. 2. Figure 2a is a network unit of our method 1. Figure 2b is a network unit of our method 2. N represents the number of extended feature maps. The number of feature maps is increased by 1 × 1 pointwise convolution. From Fig. 2, multi-scale separable convolu- tions are constructed by using a 3 × 3 convolution layer and two 3 × 3 convolution layers. They are connected (Fig. 2a) or added (Fig. 2b) by different forms, which in- crease the width of the network. For smaller input datasets, we usually choose 2–3 units to construct the network. The network structure (input is 32 × 32) is described in detail (Table 1). It is composed of three parts: input layer, three network units, and two fully connected layers.
We propose to exploit the computational units available in each slice in two different ways: the standard method implements micro-operations that target multiple operations at the same time and which use data related to the same iteration of the kernel loop. However, in some cases where the operations (e.g, subtraction and multiplication) inputs depends on each other, the exploitation of the VPU unit using this first method can be limited. For instance if operation B (e.g., multiplication) input uses the results of a subtraction realized in operation A, it will not be possible to execute both operations in parallel. Thus a more advanced technique to exploit the VPU slices is to use the computational units of a same slice as a pipeline stages where the same micro-operation instruction processes different operations from multiple iterations at the same time. For instance, if an iteration inside a kernel includes two operations where operation B inputs uses operation A output, the two operations can be pipelined thanks to the computational units that can run in parallel inside the same slice. In fact, the micro-operation register can be configured in a way that it executes in parallel operation A with iteration i inputs and operation B with iteration i − 1 inputs.
Man is inquisitive in nature. It is his innate desire to modify his own ideas, proposals and designs in every field of art. The art of surgery is not exempt from this way of life in surgeon’s career. Laparoscopy has become now the cherished art of practice of surgery across the globe. Laparoscopic cholecystectomy has become affordable, beneficial and practicable by majority of surgeons. Our new generation of surgeons has taken this art to the newer horizons. Four port laparoscopic cholecystectomy is a standard technique practiced globally even now. However new and newer techniques are born every other day. There has been mushrooming of newer techniques in handling the benign gall bladder stone disease. The commonality and theme behind any innovation and technical modification has always been to reduce the number and size of ports and to alleviate the pain and give the benefit of better cosmesis to the patients . However any technique has its advantages as disadvantages too. Is fourth port really required in laparoscopic cholecystectomy was an idea that became a research question for us to work on and we concluded that it may not be mandatory and one can avoid it in many circumstances wherein three ports are enough to accomplish the job safely . Consequently we became interested in avoiding the third port at its prescribed place in the right hypochondrium and tried a new place of putting it in the concealed area. The study published in this regard was in experience of putting the third port in the umbilical ring at 8 o’clock position on the right side . However it needed a 5 mm port to be made and its subsequent scar though concealed. As we grew with our experience we felt interested in avoiding the third port and
ABSTRACT: With the next-generation wireless network moving towards smaller cells, two-hop orthogonal frequency division multiple accesses (OFDMA) relay networks have become a mandatory component in the 4G networks. While unicast flows have received reasonable attention in two-hop OFDMA relay networks, but not much has been shed on the design of efficient scheduling algorithm for multicast flows. In this paper, we show that while relay cooperation is critical for improving the multicast flows, it should be carefully balanced to multiplex multicast sessions and hence maximize aggregate multicast performance. Also highlight strategies that carefully group relays for cooperation. Then solve the multicast scheduling problem under two models. Evaluation of proposed method reveals the efficiency of scheduling algorithm and significant benefits obtained from the multicast strategy.
Solar power is a renewable energy interest many researchers around the world to be explored for human life beneficial especially for electric power generation. Photovoltaic (PV) is one of technology developed massively to exploit the solar power for this purpose. However, its performance is very sensitive to environmental condition such as solar irradiance, weather, and climatic behavior. Thus, the hybrid power generation systems are developed to solve this output uncertainty problem. To support this such hybrid system, this paper proposes an ensemble neural network based forecaster of the power output of PV systems which will lead an efficient power management. The object of this research is the PV systems equipped with two axes automated solar tracking with peak power 10Wp. The proposed ensemble forecaster model employs four multi-layer perceptron neural networks with two hidden layers as base forecasters while the input number of historical data is varied in order to exploit the forecaster diversity. The final prediction is calculated both by conventional averaging and simple weighting optimized by the least square fitting technique. According to the research results, the both proposed approaches provide low error rate. Moreover, in term of comparison, the ensemble model with averaging combining technique gives the highest accuracy comparing to the other ensemble and conventional neural network structures.
IEEE 802.11 provides for security via two methods, which are authentication and encryption. The 802.11 standard provides for both MAC layer access control and encryption mechanisms, which is known as WEP, with the objective of providing WLANs with security equivalent to their wired counterparts. For the access control, the WLAN Service Area ID (ESSID) is programmed into each AP and is required knowledge in order for a STA to associate with an AP. In addition, there is provision for a table of MAC addresses called an Access Control List (ACL) to be included in the AP, restricting access to clients whose MAC addresses are on the list. For data encryption, the standard provides for optional encryption using a RC4 stream cipher. All data sent and received while the end STA and AP are associated can be encrypted using a shared key. In addition, when encryption is in use, the AP will issue an encrypted challenge packet to any client attempting to associate with it. The client must use its key to encrypt the correct response in order to authenticate itself and gain network access.
In recent years, a number of isolated and non-isolated DC transformers were suggested for possible use in MTDC grids [17-20]. Most of the existing isolated DC transformers have adopted the basic circuit structure of the dual active bridge (DAB) or front-to-front (F2F) connected AC/DC converters. These DC transformers capable of stopping propagation of DC fault outside the faulted DC side. Such attribute could be utilized to decrease the amount of DC circuit breakers and to split large MTDC grids into a number of self-contained isolated DC networks. The major weakness of the F2F DC transformers is that the HV and LV converters and isolation AC transformer are sized for full power, and this decreases their efficiencies.
The design of the three-port approach had one scope wound measuring around 12 to 15 mm, usually in the 6th to 7th intercostal space. There was another small 5- mm wound used for any grasping instruments needed and another one of 12 to 15 mm for the placement of a linear stapler, one inch beneath the scapular tip. The instruments we used included a 10.5-mm rigid endo- scope with a 0-degree viewing angle, an endoscopic in- strument for confirming and sampling the abnormal lung tissue and a linear stapler from another wound for resection. Mechanical (abrasion) pleurodesis was accom- plished using a small cleansing pad. After the procedure of wedge resection and pleurodesis, we usually placed a chest tube from Fr. 24 to Fr.28 and then removed it when there were no air leaks and the drainage had be- come less bloody. The single-port approach design included a single port wound of approximately 15 mm in length, usually in the 5th or 6th intercostal space be- tween the mid-axillary and anterior axillay line. (Figure 1A) A rigid 5-mm endoscope with a 30-degree viewing angle was used. A rigid endoscope, an endo- scopic grasping instrument and a linear endoscopic stap- ler were placed into the pleural cavity through the same wound (Figure 1B). One key goal here is to make the use of a conventional trocar unnecessary, because the rigid nature and cylindrical lumen of such a trocar nor- mally impedes the manipulation of the other instru- ments. An adequate procedure using multiple straight instruments can not be performed with this sort of tro- car in place. Therefore, we simply avoided the use of a trocar in the procedure. Due to the benign nature of the disease, we did not use any trocar or wound protector in the single-port procedure, because cancer seeding is not
which WSANs often serve makes the deployment of additional resources to replace failed actors impractical, and repositioning of nodes becomes the best recovery option. Distributed recovery will be very challenging since nodes in separate partitions will not be able to reach each other to coordinate the recovery process. Therefore, contemporary schemes found in the literature re-quire every node to maintain partial knowledge of the network state. To avoid the excessive state-update overhead and to expedite the connectivity restoration process, prior work relies on maintaining one- or two-hop neighbor lists and predetermines some criteria for the nodes involvement in the recovery.
wireless media. We have introduced two protocols, SASR and SAAR, to guide the single reusable spatial pathway and anypath routing, respectively. We have also implemented our protocols, comparing current routing protocols with data rates 11 and 54 Mbps. Evaluation results show that SASR and SAAR algorithms can achieve end-to-end end-to-end productivity gains under higher data rates. For the individual case, SASR achieves a 5: 3 gain of under 54 Mbps, while for SAAR, maximum gain can reach 71.6%. Moreover, in case of multiple cases, SASR can also improve the average annual productivity rate by more than 20 percent. In the meantime, significant gains in production only require additional acceptable transport costs. Additional overhead to submit a track request is less than 10 percent in our assessment. In 80 percent of cases, the total number of transmission is increased by no more than two with the SASR, while for SAAR, most increases are less than 1. For future work, one direction is to explore more opportunities to improve performance Author Details
fading, and significantly improve the capacity of channel and the throughput of network below the premise that has not increased power and frequency, MIMO technology based on the idea of spatial diversity was gradually adopted by mainstream protocol of the next generation wideband wireless communication. The perfect MIMO technology may move haltingly in the process of practice because of many problems, especially challenge of setting multi-antenna in mobile wireless sensor terminal. So, cooperative diversity, which is a new technology of space diversity, is proposed by Sendonaris and others, as shown in Figure 1. The basic idea is to create virtual multi-antenna array by the form of sharing antenna and other network resources between multi-user construction, and achieve certain spatial diversity gain through the distributed processing. In this sense, cooperative diversity provides a new path in order to apply MIMO technology to engineering practice.
Figure 5(a) shows the equivalent model of ideal PIN diode which exhibits zero resistance to current ﬂow in the ON state and inﬁnite resistance to current ﬂow in the OFF state. So, it can be used to open and close the connection between two metal strips on a single layer (Type-A) or between two layers (Type-B) as shown in Fig. 5(a). The equivalent model of PIN diode in forward bias and reverse bias is given in Fig. 5(b). In forward bias PIN diode can be replaced by a 2.1 Ω resistance and 0.6 µ H inductance values, and in reverse bias it can be replaced by a 3 kΩ reverse parallel resistance and 0.17 pF capacitance. Ansoft HFSS simulator is used to simulate the structure in which lumped RLC boundary is used to model the equivalent circuit of PIN diode. S parameters of the proposed antenna are measured using Agilent N5222A VNA. The fabricated prototype and measurement setup are shown in Fig. 5(c). The radiation pattern of the antenna is calibrated in an anechoic chamber using a standard horn antenna. The proposed integrated antenna AUT (antenna under test) is used as receive antenna and placed on the positioner with required elevation and azimuth coverage. Diﬀerent radiation patterns in xy -plane and xz -plane are measured by switching the short position on parasitic ring manually. To reconﬁgure the short position high resistivity nichrome wires are used to interconnect portable DC power battery and DC bias pad on AUT. These high resistivity wires reduce the current ﬂow in the transmission lines to avoid reradiation and messing up radiation patterns of antenna. Also portable DC power battery is covered with microwave absorber to mitigate the unwanted eﬀect on the radiation pattern. The transmitted and received powers are measured to calculate the gain of AUT using Friis formula.
The rapid advances in wireless Ad-hoc environment enables a profound of users. The data transmission via multi-hop networks creates huge traffic in opportunistic routing. To overcome from this issue, a devised opportunistic routing with congestion control policy is studied. We have proposed OR based DTMC scheme that deals with behavioral study of cooperative and non-cooperative nodes. The task of opportunistic routing is to deliver the packets in reliable and secured manner. The objective is to design routing protocols that supports non-cooperative nodes of wireless environment. We estimate packet drop ratio to observe the action of nodes and detect the congestion establishing nodes. The set of each node is selected and various parameters are considered to improve the possibility of delivering packets to their final endpoint. An experimental outcome shows the efficacy of the proposed system.
In this paper, we propose an optimal radio resource allocation with sub-carrier pairing and fairness constraints intended for multi-user, multi- carrier (OFDMA) considering single cell, single relay and two way relaying system under rayleigh fading channel environment with focus on half-duplex relaying. The rest of this paper is structured as follow. Section II describes system model, protocol description and sub-carrier pairing schemes. Mathematical analysis is presented in Section III. Problem formulation and constraint details are available in Section IV. We developed resource allocation algorithms in Section V. Performance analysis and simulations results are explained in Section VI and finally the results are concluded in Section VII.
Paolo Bellavista (email@example.com) is an associate professor of mobile and distributed systems at the University of Bologna, Italy. His research activities span from mobile computing to pervasive ubiquitous middleware, from vehicular sensor networks to big data adaptive stream processing and adaptive scalable multimedia, from IoT middleware for cloud integration to resource management in SDN, with specific focus on scalability aspects in wide-scale smart city deployment environments. He has published more than 70 magazine/journal articles and more than 90 conference/workshop papers in those fields, reporting results from several national- and EU-funded projects. He serves on the Editorial Boards of IEEE TNSM, IEEE TSC, Elsevier JNCA, Elsevier PMC, Springer WINET, and Springer JNSM. See also http://lia.disi.unibo.it/Staff/ PaoloBellavista/ for additional details and the complete publications list. Carlo Giannelli graduated from the University of Bologna (Italy), where he received a Ph.D. in computer engineering in 2008. He is now an assistant professor in computer science at the University of Ferrara (Italy). His primary research activities focus on software-defined networking, heterogeneous wireless interface integration, and hybrid infrastructure/ad hoc and spontaneous multi-hop networking environments based on social relationships. See also http://docente.unife.it/docenti-en/carlo.giannelli?se t_language=en for additional details and the complete publications list. Dr. Lagkas is a full-time lecturer at the International Faculty of the University of Sheffield, CITY College, since 2012. He is the research director of the Computer Science Department and leader of the ICT Research Track at the South-East European Research Centre, since 2017. He serves as the Chair of the Faculty ’ s ICT Committee. He has been an adjunct lecturer at the Department of Informatics and Telecommunications Engineering, University of Western Macedonia, Greece, from 2007 to 2013. He has also served as Laboratory Associate and Scientific Associate at the Technological Educational Institute of Thessaloniki from 2004 to 2012. His research and teaching mainly focus on the Computer Networks scientific field. He has worked as a freelancer computer programmer; he is an IEEE and ACM member and fellow of the Higher Education Academy in UK.
large for the considered two approaches. For these two approaches, in order to null every interference (approach 1) and null the total interference (approach 2), the conditions N < 2K 2 + K and N ≥ 2K ( K − 1 )+ 1 should be satisfied, where N is the number of relay nodes and K is the number of the pairs of user nodes. In , the authors propose an optimization problem for the TWR system by using a signal-to-noise ratio (SNR) balancing result. In , the optimal structure of the source and relay precoding matrices for a two-way linear non-regenerative multiple- input multiple-output (MIMO) relay system is studied. In , the authors showed the global optimal solution can be obtained by the branch-and-bound algorithm. Never- theless, the computational complexity is extremely high to find the orthogonal complement to solve the optimiza- tion problem in the above existing works. In order to reduce the computational complexity, [11–14] are inves- tigated by using some effective ways. In , the authors derived the achievable SR upper bound of AF beamform- ing scheme and proposed the achievable SR maximizing relay beamforming scheme when the destination and the relay node have perfect knowledge of the channel state information (CSI) for forward and backward channels. A general power iterative algorithm is proposed which can solve the global optimization problem with low compu- tational complexity when the object function form is a