Controlled thermal kinetics in RTP

Ultra-shallow junction formation is one of the most exciting new challenges for RTP process engineers and vendors. In many cases, reaction rat limited and diffusion limited processes are to be promoted or suppressed in a complementary manner. In the case of reaction rate limited processes, a short time “flash” annealing at higher temperatures is often more advantageous than the conventional temperature-time functions for 10–60 s with linear ramps. We have to optimize two phenomena simultaneously: the most effective dopant activation and defect removal without dopant loss. At the same time dopant profile redistribution is to be limited as much as possible. Beside the thermal kinetics of implant annealing, a proper surface control is also very important. Surface etching due to SiO formation with subsequent implant evaporation is as detrimental as SiO₂ growth with subsequent implant segregation. The importance and possibilities of “controlled thermal kinetics” and “limited concentration” processing mode are shown in some RTA experiments.     

Experimental study on a novel polarization state generator

Duetothe spoilageinduced bythe polarization-relatedeffects (PRE) in high-speed(≥10 Gb/s/channel) opti-cal fiber communication systems ,it is necessary to in-vestigate the effect of PRE on optical components andentire transmission systems .In general , PR…     

On optimal call admission control in cellular networks

Two important Quality-of-Service (QoS) measures for current cellular networks are the fractions of new and handoff “calls” that are blocked due to unavailability of “channels” (radio and/or computing resources). Based on these QoS measures, we derive optimal admission control policies for three problems: minimizing a linear objective function of the new and handoff call blocking probabilities (MINOBJ), minimizing the new call blocking probability with a hard constraint on the handoff call blocking probability (MINBLOCK) and minimizing the number of channels with hard constraints on both of the blocking probabilities (MINC). We show that the well-known Guard Channel policy is optimal for the MINOBJ problem, while a new Fractional Guard Channel policy is optimal for the MINBLOCK and MINC problems. The Guard Channel policy reserves a set of channels for handoff calls while the Fractional Guard Channel policy effectively reserves a non-integral number of guard channels for handoff calls by rejecting new calls with some probability that depends on the current channel occupancy. It is also shown that the Fractional policy results in significant savings (20-50\%) in the new call blocking probability for the MINBLOCK problem and provides some, though small, gains over the Guard Channel policy for the MINC problem. Further, we also develop computationally inexpensive algorithms for the determination of the parameters for the optimal policies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Amplitude and frequency variations of coherent radio signals during probing of the daytime Venusian ionosphere

A new procedure for analyzing the data obtained during radio probing of the Venusian ionosphere is proposed. The experimental results of the two-frequency probing with the use of the “Venera 15” and “Venera 16” orbiters that provide evidence that the daytime Venusian ionosphere has a layered structure are presented. It is shown that there exists a lower part of the daytime ionosphere at altitudes of 80 to 120 km.     

Wireless LANs Systems: An Advanced Resource Assignement Algorithm

The paper describes the design and simulation of a radio modem architecture, which provides wireless access to Internet in a single-hop, ad hoc network.The main emphasis is on the Medium Access Control (MAC) and Dynamic Link Control (DLC) layer’s design, and in particular on the adopted innovative scheduling algorithm, which has been developed to satisfy the system requirements of the WIND-FLEX radio modem. The algorithm is presented and compared to the Earliest Deadline First (EDF) solution.Several software simulation tests have been executed on the network, to test the performance of the system, in order to verify the capability of the scheduler algorithm to satisfy the expected requirements and the efficiency of the implemented solutions. Giuseppe Razzano was born in Roma, Italy, in 1974. He has graduated in Electronic Engineering “summa cum laude” and has received PhD in Communication Systems and Computer Science, in 2004 from University of Rome “La Sapienza”. From 2000 to 2001 he worked as research assistant at VTT electronics, in Finland. From 2004 to 2005 he worked as senior researcher at Forschungzentrum Telekommunikation Wien (Telecommunication Research Centre Vienna) in Austria. Currently, he works as System Engineer for Vitrociset S.p.A., working in a project funded by European Space Agency (ESA), for the development of a new generation space launcher vehicle (VEGA). In the past years, he worked in several projects funded by EC within the IST (Information Societies Technology) program, being also involved in projects in collaboration with Italian companies. His research is focused on resource management algorithms for wireless LANs and cellular networks. He is also interested in object-oriented programming and development methodologies. In these fields, he is author of several papers published in international journals and conferences. Francesco Delli Priscoli was born in Rome in 1962. He graduated in Electronic Engineering “summa cum laude” from the University of Rome “La Sapienza” in 1986. He received the Ph.D. in system engineering from the University of Rome “La Sapienza” in 1991. From 1986 to 1991 he worked in the “Studies and Experimentation” Department of Telespazio (Rome). Since 1991 he is working for the University of Rome “La Sapienza” where, at present, he is “Full Professor” and holds the courses “Automatic Controls”, “System Theory” and “Network Control and Management I and II”. In the framework of his activity, he researches in the nonlinear control theory and in the area of control-based resource management procedures for the third and forth generation of mobile systems. He is the author of about 150 technical papers on the above topics appeared on major international reviews (about 50) and conferences (about 100). In 2000 he has been scientific consultant for the Italian Council of Ministers in the framework of the auction for the assignment of the Italian Universal Mobile Telecommunication System (UMTS) licensees. He is an associate editor of Control Engineering Practice and a member of the IFAC Technical Committee on “Networked Systems”. He is/has been scientific responsible, for the University of Rome “La Sapienza”, of 17 projects financed by the European Union (fourth, fifth and sixth framework programmes) or by the European Space Agency (ESA), dealing with resource management for UMTS and broadband terrestrial and satellite wireless systems. He is also a project evaluator for the European Commission. Roberto Cusani received the “laurea” degree in Electronic Engineering (cum laude) and the Ph.D. in Communication Systems and Computer Science from the University of Rome “La Sapienza”. From 1986 to 1990 he was research engineer at the University of Rome “Tor Vergata”, teaching Digital Signal Processing. In 1991 he joined the University of Rome “La Sapienza” as Associate Professor of Signal Theory. In 2000 he becomes Full Professor and teaches Information Theory and Coding, and Mobile Communications. His former research activities concern transmission and coding of signals and images, with emphasis on random processes, spectral estimation and image coding. Since 1992 he focused his activities in the field of the digital communication systems, with emphasis on channel equalisation and coding for HF and radio-mobile (GSM) links, on the design of CDMA receivers for UMTS and, in general, on the use of digital techniques within telecommunication equipments. More recently his interests also includes the study of MAC (Multiple Access Control) protocols with application to wireless area networks (WLANs), reconfigurable ad-hoc networks and satellite links. He is author of more than 100 publications in international journals and conferences, of the text-book “Teoria dei Segnali” and of five patents regarding telecommunication applications. He was involved in many research programs, both national and international, and in projects with the industrie.     

Characterization of subthreshold MOS mismatch in transistors for VLSI systems

MOS transistor mismatch is revisited in the context of subthreshold operation and VLSI systems. We report experimental measurements from large transistor arrays with device sizes typical for digital and analog VLSI systems (areas between 9 and 400μm²). These are fabricated at different production qualified facilities in 40-nm gate oxide,n-well andp-well, mask lithography processes. Within the small area of our test-strips (3 mm²), transistor mismatch can be classified into four categories: random variations, “edge,” “striation,” and “gradient” effects. The edge effect manifests itself as a dependence of the transistor current on its position with reference to the surrounding structures. Contrary to what was previously believed, edge effects extend beyond the outer most devices in the array. The striation effect exhibits itself as a position-dependent variation in transistor current following a sinusoidal oscillation in space of slowly varying frequency. The gradient effect is also a position-dependent spatial variation but of much lower frequency. When systematic effects are removed from the data, the random variations follow an inverse linear dependence on the square root of transistor area.     

EACLE : Energy-Aware Clustering Scheme with Transmission Power Control for Sensor Networks

In this paper, we propose a new energy efficient clustering scheme with transmission power control named “EACLE” (Energy-Aware CLustering scheme with transmission power control for sEnsor networks) for wireless sensor networks, which are composed of the following three components; “EACLE clustering” is a distributed clustering method by means of transmission power control, “EACLE routing” builds a tree rooted at a sink node and sets the paths from sensor nodes taking energy saving into consideration, and “EACLE transmission timing control” changes the transmission timing with different levels of transmission power to avoid packet collisions and facilitates packet binding. With an indoor wireless channel model which we obtained from channel measurement campaigns in rooms and corridors and an energy consumption model which we obtained from a measurement of a chipset, we performed computer simulations to investigate the performance of EACLE in a realistic environment. Our simulation results indicate that EACLE outperforms a conventional scheme such as EAD (Energy-Aware Data-centric routing) in terms of communication success rate and energy consumption. Furthermore, we fully discuss the impact of transmission power and timing control on the performance of EACLE.     

ATM cell encryption and key update synchronization

This paper presents a data compaction/randomization based approach as a mode of block encryption for ATM (Asynchronous Transfer Mode) cells. The presented approach converts a plaintext into pseudo‐random plaintext before ciphering to conceal patterns in the plaintext. The underlying idea behind this scheme is the Shannon's principles of “confusion” and “diffusion” which involve breaking dependencies and introducing as much randomness as possible into the ciphertext. In this scheme, confusion and diffusion are introduced into the system by first compressing the ATM cell payload and then spreading a continuously changing random data over the entire content of the cell. As a mode of operation for block ciphering, this scheme offers the following attractive features:(i) plaintext patterns are pseudo‐randomized and chained with ciphertext (thereby, preventing against “dictionary”, “known plaintext”, and “statistical analysis” attacks), (ii) it is self‐synchronizing, (iii) cell loss has no additional negative effect, (iv) no IV (Initialization Vector) storage is required, (v) it is encryption‐algorithm independent, (vi) there is no cell‐to‐cell dependency (no feedback from previous cells), and (vii) it is highly scalable (i.e., cells from the same stream can be ciphered and deciphered in parallel). This paper also presents a secure mechanism for in‐band synchronization of encryption/decryption key updates using a “marker‐cell” that is carried within the data channel. An important aspect of both the above mechanisms is that they do not require any changes to the ATM cell header or ATM infrastructure. This revised version was published online in June 2006 with corrections to the Cover Date.     

Wavelet-based multifractal analysis of 1-D and 2-D signals: New results

During the past decade, new tools stemming from fractal geometry and wavelet analysis are meeting with great success in signal image processing. This paper will focus on these two topics: Wavelets and Multifractal. Both themes evolved towards self contained theories, and yet, a host of reasons justify for coupling them in same applications. It is well known that both analyses share the same conceptual backbone of “scale”: it is the “mathematical zoom” commonly associated to wavelet analysis and it is the “scaling laws” that underlie multifractal structures. Very naturally then, wavelets stood as a privileged tool for analyzing and characterizing multifractal signals and images. Hence, the purpose of this paper is to illuminate some of the issue involved in taking advantage of the current advances in wavelets and multifractals analysis. We discuss continuous, discrete, orthogonal wavelets and present applications to fracture processes and medical ultrasound imaging.     

Performance of linear MMSE multiuser detection combined with a standard IS-95 uplink

Current implementation of IS-95 based systems is performance limited due to the use of a “conventional” detection scheme, which is susceptive to inter-user interference. We focus on the uplink, and try to examine the performance enhancement achieved by a suboptimal linear multiuser MMSE pre-filter, applied in front of the “standard” detection mechanism. We demonstrate the limitations of this relatively simple approach, and the constellations in which it may show improved performance. This revised version was published online in July 2006 with corrections to the Cover Date.     

A refined model for performance analysis of output-buffered Banyan networks

In this paper, a new analytical model for performance analysis of output-buffered Banyan networks is proposed. In this model, we consider not only the number of packets stored in a buffer, but also the state of the buffer's Head of Line (HOL) packet (“new” or “blocked”). Simulations are used to verify the model's accuracy. The analytical results show that the maximum throughput decreases when the switch size increases, and that the throughput increases as the buffer size increases. When the buffer size is large enough, say 10, the maximum throughput is close to saturation. The maximum normalized delay increases almost linearly with the increase in buffer size. This revised version was published online in June 2006 with corrections to the Cover Date.     

Mathematical simulation of the processes of generation of “shock waves” in a two-dimensional electron gas in the channel of a ballistic field-effect transistor

The processes of formation of “shock waves” in a two-dimensional electron gas in the channel of a ballistic field-effect transistor are simulated numerically. The “shock waves” are generated due to the ac voltage applied to the gate of the transistor. The results of numerical simulation are used to analyze the structure of the “shock wave” front and the dependence of the structure on the dispersion and dissipation effects.     

Characteristics of radio frequency paths of on-board aviation navigation-landing equipment

Methodologies and results of researching high-frequency paths in on-board navigationlanding equipment of meter frequency band are presented in this article. Recommendations on their design using international recommendations “ARINC” and “Rules of planes’ flight eligibility RPFE-3” are given.     

Transport Protocols in the TCP Paradigm and their Performance

This paper defines a class of “TCP-like” transport protocols, called protocols in the TCP Paradigm. The name indicates the protocols are not TCP, but in some sense similar to it. The class includes TCP and also Tom Kelly's “Scalable TCP”, and more. Most of the protocols in the class require ECN in order to become implementable. Most even require a form of ECN that allows a high rate of marked packets. The paper analyzes performance of protocols in the TCP Paradigm and indicates a subset that is likely to perform as well as, or quite possibly better than, Scalable TCP. Criteria are the ability to achieve high throughput, to maintain a steady flow if the ECN marking probability is constant, and to adapt quickly to a changing marking probability. A main conclusion is that in order to benefit from protocols in this paradigm, “source behavior” (reaction of endpoints to marked and unmarked packets) and “router behavior” (how routers choose marking probabilities) must be investigated together.     

On the fault-tolerant routing in distributed loop networks

Based on their "Theorem 2", an O(δ)-time algorithm of searching for the shortest path between each pair of nodes in a double loop network was proposed by K.Mukhopadyaya, et al.(1995). While, unfortunately, it will be proved that both "Theorem 2" and its proof are in error. A new and more faster O(△)-time, △≤δ, algorithm will be presented in this paper.     

ITERATIVE “ONE－SHOT” DECORRELATION IN DS－CDMA SYSTEMS

In this paper, an iterative “one-shot“ decorrelator for asynchronous code Division Multiple Access(CDMA) systems is proposed. This decorrelator feedbacks the decorrelated symbols of interfering users before decision to mitigate their interferences. As a result, this decorrelator is a linear detector and does not need any amplitude information of users as in decisionfeedback detectors. Compared with existing “one-shot“ decorrelator, it has reduced complexityand provided better performance while eliminating all Multiple Access Interference(MAI). The performance of this decorrelator is analyzed thoeritically, and analytical result is given. Numerical results show near-far resistant capability of this decorrelator in both AWGN and fading channel.     

Utility-Aware Cognitive Network Selections in Wireless Infrastructures

Operators of wireless infrastructures should maintain their users “always-best-connected”. This concept means that applications should be offered to users at the best possible Quality of Service (QoS) level, taking into account profile, context and policy information. The profiles provide the user requirements and preferences, the terminal capabilities, and the application requirements. The policies provide the objectives, constraints imposed by various stakeholders, for instance the network operator (NO). The context of operation designates relevant applications, available networks and their QoS capabilities. The “always-best-connectivity” concept can be achieved by directing user terminals to the most appropriate networks of the heterogeneous infrastructure of the NO. In this respect, advanced terminal management functionality is required. This paper presents management mechanisms for utility-based cognitive network selections. The utility is used for expressing the user desire for a QoS level. Cognition mechanisms are applied for learning the QoS capabilities of candidate networks, and therefore increasing the reliability and seamlessness of the network selections. Extensive results are provided, which show the behaviour of the scheme in terms of network selections made, and computational effort required for the acquisition of the knowledge.     

The asymptotic solution of the diffraction problems of the efectromagnetic waves by a perfect comductor

In this paper, the two dimentional problems of the diffraction of the electromagnetic waves by a perfect conductor are discussed by using the perturbational mapping function in Savin’s form. The general method and asymptotic formulas to solve this problem are presented. Especially, for the asymptotic solutions based on a circular cylindrical conductor, the formulas to calculate “O”—order and “I”—order asymptotic solution are given     

A study of multi-energy ion implantation

A new calculation method of multi-energy ion implantation, i.e, “equivalent area method”, has been studied. An arbitrary density concentration or energy profile can be achieved, according to requirements of the device, by this method. It provides the basis of fabricating thin-film flat impurity profile devices. By use of this method, the Si-RAPD device with rectangular impurity profile, the Si-RAPD device with a particular low-high-low structure and the GaAs MESFET or IMPATT device with “horse head” type structure are designed and calculated. All results are satisfactary and the design of the new type device can be predicted by this method. The calculated results in this paper are well in agreement with the experimental values in literature.     

Express method of finding recombination parameters in technological silicon plates

In this paper a new method of finding recombination parameters, such as surface recombination rate, “effective” and “bulk” lifetime of charge carriers, of a silicon plate based on only one measurement. This method is grounded on injection of charge carriers by pulse illumination of a local region of semiconductor’s fundamental absorption region with light and measuring the time dependence of concentration of non-equilibrium charge carriers. The method is tested in manufacturing conditions on technological silicon plates and may be used for quality control in manufacturing of solar elements.