Uniqueness of solutions of piecewise linear resistive networks withtwo terminal resistors

Consider a network comprising two terminal linear, piecewise linear resistors and independent sources. Contrary to widely held belief, it is shown that the determinant sign condition (i.e. the Jacobian determinant is nonzero and has the same sign in all the regions) is both necessary as well as sufficient to guarantee uniqueness of solutions of these networks. For this purpose the existence of a specific hybrid matrix is not required     

Linear filtering and piecewise linear correlation functions

For a class of piecewise linear correlation functions, it is shown that optimal linear mean-square filtering is achieved with a finite number of samples of the process for any finite observation interval. The class of correlation functions is defined by a particular property of the points at which they change slope. Conditions are discussed under which an arbitrary piecewise linear function is a correlation function. An example demonstrating various aspects of the theory is given, and applications of the theory are considered.     

Designing reliable networks with short paths

We present a technique for constructing highly reliable networks in which locations consist of pairs of redundant vertices and in which every pair of locations has a pair of short disjoint paths connecting them. One of the paths between locations has one hop and, in most cases, the other path between locations has two hops. We further show that the networks have as few edges as possible and the vertices in the networks have nearly as small a degree as possible.     

Behavioral and macro modeling using piecewise linear techniques

In this paper we will demonstrate that most digital, analog as well as behavioral components can be described using piecewise linear approximations of their real behavior. This leads to several advantages from the viewpoint of simulation. We will also give a method to store the resulting linear segments in a compact way, in order to avoid storage problems.     

Wireless ultrawideband communications and sensor networks

An actively advancing branch of wireless ultrawideband communications is considered. Direct chaotic transceivers of two types are described. The transceivers were developed at the Institute of Radio Engineering and Electronics, Russian Academy of Sciences. Application of these transceivers in wireless sensor networks is demonstrated.     

Global corporate communications with integrated services digital networks

This paper presents proposals and justification for standards governing the implementation of integrated service digital networks (ISDN). Using several programming protocols in a layered architecture provides continuing service during system evolution. The authors use a corporate communications environment for examples as the most probable initial implementation of the networks described. Some ISDN sites are operating, although not yet on a global scale, and present the building blocks for more advanced services in the near future. The authors present arguments supporting a concerted effort be started now to establish global standards for ISDN, so that design and development can comply in the most time-effective manner.     

Microwave communications systems and networks in Hungary

The approaches of microwave communications in Hungary are surveyed. Microwave communication systems developed over the last several decades are presented and an overview of the Hungarian microwave communications networks is given emphasizing the methods meeting the user's needs. The special features of the Hungarian equipment development and network structure is also discussed     

Modelling and planning fixed wireless networks

Abstract  

This paper describes a mathematical model for the automated design of fixed wireless access networks (FWA) through the automatic selection and configuration of base station sites. An optimisation algorithm is presented which generates the fixed wireless access network infrastructure design, and results are presented to illustrate the use of the model and its implementation. Economic measures based on the net present value (NPV) are defined to assess the financial viability of potential network designs. The NPV is used within the mathematical optimization framework to produce cost-effective deployments that maximize economic performance while maintaining technical constraints on the network. The model takes into account time-varying input parameters on CapEx, OpEx, revenues and subscriber requirements to model the dynamic nature of the market. Technical radio constraints taken into account include downlink area coverage, interference, capacity and availability. The model and optimisation framework are illustrated by considering the deployment and configuration of infrastructure for three scenarios representing urban, suburban and rural regions. Experiments illustrating the staged deployment of infrastructure over a number of time periods are also presented.     

Dynamic TDD and fixed cellular networks

There are many benefits in using time division duplex (TDD) instead of frequency division duplex (FDD) schemes in fixed wireless cellular systems. To name a few; channel reciprocity for the single carrier frequency used on both up and downlinks will allow easy access to channel state information, reduced complexity of RF design, much higher flexibility in handling dynamic traffic, simpler frequency plan, etc. However, there exists a serious limiting factor in using dynamic-TDD (D-TDD) in cellular systems. This is due to a steady interference on uplinks in a cell, caused by downlink transmissions of other cells. Simulation results show in D-TDD cellular systems, performance is unacceptable, when omni-directional antennas are used at base stations. Simulation results have also demonstrated a great potential for smart antennas in fixed D-TDD bandwidth-on-demand wireless systems     

Personal communications services through the evolution of fixed andmobile communications and the intelligent network concept

New telecommunications services tend to consider fixed network subscribers' requirements as well as mobile network subscribers' requirements. On one hand, subscribers of fixed networks would like to benefit from the mobility offered in mobile networks. On the other hand, mobile subscribers would like to access to services inherent in fixed networks. Personal communications services (PCS) meet this trend while allowing fixed and mobile convergence. In this environment, the application of intelligent networks (INs) to fixed and mobile networks is very convenient to realize PCS. Thus, the natural advancement of telecommunications systems (fixed and mobile) consists in the definition of new telecommunications architectures which take into account technologies from both fixed and mobile environments. This article studies how the IN is used to support mobility and interworking for PCS. Although mobility management already exists in cellular networks like GSM, it is desirable to use the IN concept to introduce flexibility. In addition, the IN allows the introduction of new supplementary services in PCS. Furthermore, the IN concept can be utilized to provide necessary networking functions for the integration of fixed and mobile networks. This article also highlights the involvement of IN in the definition of the global communications systems such as Telecommunication Information Networking Architecture (TINA), Universal Mobile Telecommunications System (UMTS), and International Mobile Telecommunications in the year 2000 (IMT2000)     

Designing multihop wireless backhaul networks with delay guarantees

As wireless access technologies improve in data rates, the problem focus is shifting towards providing adequate backhaul from the wireless access points to the Internet. Existing wired backhaul technologies such as copper wires running at DSL, T1, or T3 speeds can be expensive to install or lease, and are becoming a performance bottleneck as wireless access speeds increase. Longhaul, non-line-of-sight wireless technologies such as WiMAX (802.16) hold the promise of enabling a high speed wireless backhaul as a cost-effective alternative. However, the biggest challenge in building a wireless backhaul is achieving guaranteed performance (throughput and delay) that is typically provided by a wired backhaul. This paper explores the problem of efficiently designing a multihop wireless backhaul to connect multiple wireless access points to a wired gateway. In particular, we provide a generalized link activation framework for scheduling packets over this wireless backhaul, such that any existing wireline scheduling policy can be implemented locally at each node of the wireless backhaul. We also present techniques for determining good interference-free routes within our scheduling framework, given the link rates and cross-link interference information. When a multihop wireline scheduler with worst case delay bounds (such as WFQ or Coordinated EDF) is implemented over the wireless backhaul, we show that our scheduling and routing framework guarantees approximately twice the delay of the corresponding wireline topology. Finally, we present simulation results to demonstrate the low delays achieved using our framework.     

Analysis and enhancements to piecewise linear comparametric image registration.

This correspondence details enhancements to previous work on piecewise linear comparametric image registration. The enhancements come in the form of slope constraints and knots' location selection in the comparametric modeling. An analysis of the properties of comparametric functions leads to two general slope constraints that, along with a knot location selection based on the reference image's pixel value distribution, serves to reduce error and sensitivity to the number of segments considered as well as allow for the solution to cases in which there are gaps in the comparagram. Results on real images are presented.     

Mobility management in current and future communications networks

This article describes current and proposed protocols for mobility management for public land mobile networks (PLMNs), Mobile IP, wireless ATM, and satellite networks. The integration of these networks is discussed in the context of the next evolutionary step of wireless communications networks. First, a review is provided of location management algorithms for PCS implemented over a PLMN. The latest protocol changes for location registration and handoff are investigated for Mobile IP, followed by a discussion of proposed protocols for wireless ATM and satellite networks. Finally, an outline of open problems to be addressed by the next generation of wireless network service is discussed     

Parallel,self-organizing,hierarchical neural networks with forward-backward training

A forward-backward training algorithm for parallel, self-organizing hierarchical neural networks (PSHNNs) is described. Using linear algebra, it is shown that the forward-backward training of ann-stage PSHNN until convergence is equivalent to the pseudo-inverse solution for a single, total network designed in the least-squares sense with the total input vector consisting of the actual input vector and its additional nonlinear transformations. These results are also valid when a single long input vector is partitioned into smaller length vectors. A number of advantages achieved are: small modules for easy and fast learning, parallel implementation of small modules during testing, faster convergence rate, better numerical error-reduction, and suitability for learning input nonlinear transformations by other neural networks. The backpropagation (BP) algorithm is proposed for learning input nonlinearitics. Better performance in terms of deeper minimum of the error function and faster convergence rate is achieved when a single BP network is replaced by a PSHNN of equal complexity in which each stage is a BP network of smaller complexity than the single BP network.     

Radio communications: components, systems and networks

Dear readers: As one of us was flying over the Pacific returning from a trip to Asia, this editor recalled a comment from Bob Lucky's speech at the 1992 Conference on Information Sciences and Systems in Princeton - "If I were to start my career again, I would work in wireless communications."Indeed, recent decades in wireless communications have brought nothing less than an explosion in all areas of research and development, followed by a proliferation of devices (we are often reminded that they are not simply phones) that have changed our everyday lives. In any of our disciplines, from physical layer design to networking, we have witnessed how advanced concepts from research laboratories find their way into products in record time - multiuser detectors, multiple input multiple output (MIMO), and turbo decoders to name a few. It is not clear whether our schools can teach graduates fast enough to keep up with the rate of adoption of advanced technologies in the markets. The adoption of wireless technologies such as cellular, WiFi, GPS, and Bluetooth, as well as more recent developments such as WiMAX and near field communications, are transforming the way we interact, communicate, and socialize.     

Radio communications: components, systems and networks

This is an introduction to the special section of papers from DySPAN 2007 - the IEEE Symposium on New Frontiers in Dynamic Spectrum Access Networks that was held on April 17-20, 2007 in Dublin, Ireland.     

Approximation of loss calculation for hierarchical networks with multiservice overflows

This paper studies loss calculation in hierarchical networks with multiservice overflows which have different call arrival rates, mean holding times, bandwidth requirements and share a common link. The loss calculation involves two challenging problems: 1) the computation of the two moment characterizations of multiservice overflow traffic over the shared link, 2) the calculation of the loss probabilities for multiservice non-Poisson overflow traffic in hierarchical systems. An efficient approximation method, known as multiservice overflow approximation (MOA), is proposed to enable multiservice networks designs with hierarchical architecture. Two contributions are included in the MOA method. First, an approximation based on blocking probabilities matching is proposed to compute the variances of multiservice overflows over the shared link. Second, a modified Fredericks & Hayward's approximation is used to calculate the loss probabilities of multiservice non-Poisson over flow traffic. The performance of the MOA method is evaluated in a two-tier hierarchical cellular network and compared with an existing approximation method based on multi-dimensional Markov-modulated Poisson process (MMPP). Verified by simulations, the MOA method achieves better accuracy in the general heterogeneous cases at lower computational cost than the MMPP method.