Search

This paper deals with an approach to detect face from image with complex background. That can be use in many areas (eg. security systems, biometrics, telecommunications, etc.).In the first part there is presented brief overview of common used method for face localization in image. On the basis of comparison of its properties there was developed appropriate combination of several methods with particular improvements. The goal was to find suitable accuracy to speed rate. Methods were implemented in MATLAB and accuracy rate was tested on Georgia Tech face database. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel mechanism for the multicast congestion control over UMTS networks. The proposed mechanism is based on the well known TCP-Friendly Multicast Congestion Control (TFMCC) scheme. The key challenge in the design of the new scheme lies in improving the TFMCC mechanism to cope with the packet losses caused by either the temporary or the permanent degradation of the wireless channels. The proposed scheme introduces minor modifications in the UMTS nodes with respect to the computing power of the mobile terminals. Finally, our approach is implemented in the ns-2 network simulator and is evaluated it under various conditions. [ABSTRACT FROM AUTHOR]

In practice, different methods for enhancing speech hidden in noise are used but none of the available methods is universal; it is always designed for only a certain type of interference that is to be suppressed. Since enhancing speech masked in noise is of fundamental significance for further speech signal processing (subsequent recognition of speaker or type of language, compression, processing for transmission or storing, etc.), it is necessary to find a reliable method that would work even under considerable interference and will be modifiable for different types of interference and noise. The methods known to date can basically be divided into two large groups: single-channel methods and multi-channel methods. The basic problem of these methods lies in a rapid and precise method for estimating noise, on which the quality of enhancement method depends. If the noise is of stationary or quasi-stationary nature, its determination brings further difficulties. A method is proposed in the article for enhancing the estimation of power spectral density of noise using the wavelet transform. [ABSTRACT FROM AUTHOR]

Localization positioning is one of the basic problems in wide wireless sensor networks. The main objective of positioning process is to define the location of a sensor (node or device) from the relevant information obtained from reference nodes. These nodes already know their location. In many cases, these reference nodes are called beacons. The paper deals with proximity based location technique and their modifications. It does not belong to the most accurate techniques, but on the other hand it is low cost alternative to more expensive techniques. The objective of the paper is to give a survey of various proximity based location techniques performance. We analyze the influence of various design choices on the accuracy of localization techniques. The results of basic proximity based localization techniques are compared with modified proximity technique, which is proposed in this paper. [ABSTRACT FROM AUTHOR]

A cost effective ZigBee-based wireless parking sensor system is presented in this article. Ultrasonic transmitter and receiver are used for distance measurement. An evaluation, control and wireless data transfer are realized by one chip - Panasonic hybrid chip PAN4450 (8-bit microcontroller + IEEE 802.15.4 radio). System consists of four independent distance sensors and one central display and control unit. [ABSTRACT FROM AUTHOR]

This paper describes design and computer simulation of a new architecture of a node active network element, based on artificial neural network technology with the support of priority processing for different connection types. As an example of a network element was selected switching area. This network element with optimized switching area is able to transfer large data quantity with minimum delay. Architecture of network element, that contains artificial neural network for optimized priority switching is described in this paper. It describes implementation of neural network in control process for data units switching. The programming language MATLAB 7.0 was used for software simulation. Network elements with new architecture, which uses a neural network, as well as intimated simulation, are suitable for working for example in personal wireless network communication systems. [ABSTRACT FROM AUTHOR]

A planar structure of the electrodes employed in conductivity measurements is utilizable at small range of conductivity measurement because of small sizes, planar ordering and technology which significantly influence the impedance behavior. The paper presents new approach in the field of precise electrolytic conductivity measurements with planar sensors. This novel measuring method was suggested for measurement using thick-film screenprinted interdigital electrodes (IDEs). Correction characteristics over a wide range of specific conductivities were determined from an interface impedance characterization of the IDEs. A local minimum of the imaginary part of the interface impedance is used for corrections to get linear responses. The method is seeking the optimal frequency for determination of specific conductivity of the solution by IDEs in order to achieve a highly accurate response. The method takes precise conductivity measurements in concentration ranges from 10-6M to 1 M without cell replacement. [ABSTRACT FROM AUTHOR]

The paper describes new approach of potentiostat for very low sensor current measurements. Recent potentiostats were used as measurement devices which were standalone and sensors were connected by a screened wire. These concepts are inconvenient for the presented very low current measurements. The new approach is based on the potentiostat circuitry integrated on a chip that should be directly contacted to a Thick Film Technology (TFT) sensor. [ABSTRACT FROM AUTHOR]

This paper demonstrates that the addition of chemical agents and carbon fibers to cement can greatly enhance the shielding effectiveness of the concrete. In addition to improving the shielding effectiveness, carbon fibers and chemical agents enhance the tensile and flexural strengths significantly. As both carbon fibers and steel fibers are electrically conductive, both can be added to cement to enhance the shielding effectiveness, but steel fibers tend to rust whereas carbon fibers are chemically stable and inert. [ABSTRACT FROM AUTHOR]

The paper deals with a bandpass sigma-delta modulator (BP SDM), which is used for conversion of signal from capacitive pressure sensor. This approach is absolutely new and unique, because this kind of modulator is utilized only for wireless and video applications. The main advantage of BP SDM is due to its defined band. That is why it is resistant against offsets of its sub-circuits. Another important advantage is low power consumption, since the BP SDM digitizes only narrow band instead of whole Nyquist band with similar dynamic range. The paper shows basic ideas of this approach and simulation results. The main stages are implemented in switched-capacitor (SC) technique. The paper presents two possibilities how to design PLL block. The first one is conventional approach and the other one is with digital sigma-delta modulator as generator of input harmonic signal. [ABSTRACT FROM AUTHOR]

Field Programmable Mixed-Signal Arrays (FPAA) designs are reviewed and standard building blocks described with respect to circuit parameters and design limitations. The second-generation current conveyor is introduced as an analog building block with properties similar to those of an operational amplifier, and which has the potential for high frequency operation. A current conveyor can be implemented in an area similar to that of a simple operational amplifier. Potentially greater bandwidths are achieved, while using CMOS technology instead of bipolar technology and test circuit design is proposed. [ABSTRACT FROM AUTHOR]

In the area of analog techniques and primary processing of analog signals in the last decade, some authors have focused on circuits with current or voltage conveyors. Most of them have concentrated on filters with current conveyors, their design and properties, different connections, sensitivity analysis, etc. The present paper is devoted to the basic theoretical description of non-linear circuits with CCII+/-current conveyors in non-filter applications. The basic connections of circuits with current conveyors are chosen, in which a non-linear three-pole is considered, and the functional relations of these connections are established. The applications of non-linear circuits given in the paper are half-wave and full-wave precise rectifiers, which are an analogy to precise measuring rectifiers with operational amplifiers. Rectifiers with current conveyors operating in the current mode can exhibit some positive properties. Only the basic connections are given and the basic functional computer simulations are made here. The active element chosen for the practical rectifier realization was an appropriately connected OTA amplifier. In conclusion, some measurement results are given. [ABSTRACT FROM AUTHOR]

Research and development of Spectrum Administration for metallic access networks analyzed possibilities of matrix representation for transmission circumstances. Some interesting remarks were gained as a side output of this work. [ABSTRACT FROM AUTHOR]

The paper presents complex treatment and measurement system based on USB and its enhancements. The article is divided into two parts. The first one deals with up-to-date USB enhancements which are USB On-The-Go, USB Test & Measurement Class, Wireless USB, PictBridge, PoweredUSB, Inter-Chip USB, Battery charging specification. The second part presents the practical usage for measurement and therapeutical system. [ABSTRACT FROM AUTHOR]

Contemporary optical fibers can deal with almost all of the unfavorable effects which are known these days. They have sufficiently low specific slump, they can handle a slump caused by OH-ions, they can restrain the multimode effect and finally they can compensate a chromatic dispersion. But there is one problem, which the present science can't solve and this problem is the Polarization Mode Dispersion (PMD). This effect is a restricting factor of high-speed long-distance optical routes. The capacity increase of the existing optical routes is more often realized by multiplexing methods. Using more wavelengths makes multiplication of the optical fiber transfer rate possible. It evokes not only the advancement of fiber letting (known as "Dark Fiber" service), but more often also a single wavelength letting. [ABSTRACT FROM AUTHOR]

This article deals with active frequency filter design using signalflow graphs. The procedure of multifunctional circuit design that can realize more types of frequency filters is shown. To design a new circuit the Mason-Coates graphs with undirected self-loops have been used. The voltage conveyors whose properties are dual to the properties of the well-known current conveyors have been used as the active element. [ABSTRACT FROM AUTHOR]

Novel second-order multifunction filters operating in current mode are described. Their structure is based on three current operational amplifiers connected in a feedback loop. These active elements are dual to the well-known operational amplifiers and are suitable for high-frequency signal processing. The designed filters offer low-pass, band-pass and high-pass transfer functions simultaneously. Computer simulation is carried out to prove the functionality of a filter variant. The influence of real properties of active elements is analyzed. [ABSTRACT FROM AUTHOR]

Increasing demands on circuits with low supply voltage and low power consumption lead to the realization of analogue circuits working in the current-mode. In this paper a new topology is presented of multifunctional frequency filter SIMO (Single Input Multiple Output) working the in currentmode. The proposed circuit is realized using four second-generation current conveyors and six passive elements. A high value of quality factor can be achieved, changeable independently of the characteristic frequency. The results of sensitivity and tolerance analyses of the proposed filter are given. The properties of the designed filter were also experimentally verified. [ABSTRACT FROM AUTHOR]

In this paper the procedure of RF filter design using two active elements OTA is shown. The general method of filter design using OTA amplifiers, when the fully connected feedback network was designed around the two OTA elements, is shown. Autonomous circuits were gradually picked out from this general arrangement, using two to five passive elements. These autonomous circuits then serve as an initial circuit in designing different types of frequency filters. On a selected autonomous circuit, all the procedure of multifunction filter design is shown. The properties of the proposed secondorder multifunction filter were subjected to an AC analysis in the PSpice software [8], a generalized sensitivity analysis and experimental measurement. [ABSTRACT FROM AUTHOR]

In this paper the design method leading to the radio-frequency (RF) filters working in the pure current mode is shown. New active elements called current mirrors and inverters (CMI) are presented, a generalized variant (GCMI) is used for the design purposes, and a universal version (UCMI) is fitted to the filtering-circuit final solution. Initial autonomous circuits are derived from the full admittance network, which is defined. In this paper, a few autonomous circuits with five passive elements are presented. An illustration of the filter design with independent quality factor adjustment with respect to the characteristic frequency is given. Results obtained from the measurement of samples are shown. [ABSTRACT FROM AUTHOR]

This paper presents a proposal of a routing protocol to Wireless Sensor Networks, called SHRP (Simple Hierarchical Routing Protocol), whose primary objective is to save battery energy. SHRP also provides both reliability and a load balance solution. As a novel proposal, it is a proactive protocol that chooses efficient routes, by selecting just the nodes that can contribute to extend the network lifetime. In addition this protocol is also able to inform to a central point about any possible disconnection caused by a reduction of battery power or a long interference period. The data defined by SHRP protocol can be aggregated during the sending and forwarding tasks. Redundant data are not sent, which contributes to energy saving. This protocol uses the IEEE 802.15.4 under of CC2420 radio chips and it has been implemented on TinyOS operation system. [ABSTRACT FROM AUTHOR]

In this paper, we propose optimized method of discrete wavelet transform. There is many use of wavelet transform in digital signal processing (compression, wireless sensor networks, etc.). In those fields, it is necessary to have digital signal processing as fast as it possible. The new segmented discrete wavelet transform (SegWT) has been developed to process in real-time. It is possible to process the signal part-by-part with low memory costs by the new method. In the paper, the principle and benefits if the segmented wavelet transform is explained. [ABSTRACT FROM AUTHOR]

Some ad hoc protocols allow the discovery and/or storage of multiple routes to the same destination node. The selection of the path to utilize is commonly based on the criterion of the minimum number of hops. However, other strategies could be more appropriate to improve the network performance. In this sense, this paper proposes the criterion based on the estimation of the Mean Residual Path Lifetime. In order to compute this metric, a formal description of link duration in mobile ad hoc networks is presented. The model has been verified by means of simulations enclosing different mobility and transmission conditions. From the link duration model, an analytical expression for path duration and mean residual lifetime is then derived. Finally, the authors show that selected ad hoc routing paths live longer when the proposed criterion is employed [ABSTRACT FROM AUTHOR]

This paper presents an error concealment technique for image transmission in JPEG2000 for the lowest frequency coefficients. The proposed method uses the layer structure that is a feature of the JPEG2000. The most significant layer is hidden in place of the lowest layer of the bit stream. After transmission this embedded layer is used for error concealment. The bit stream encoded using the proposed method has the same data structure as the standard JPEG2000. Experiments show the effectiveness of these algorithms. [ABSTRACT FROM AUTHOR]

This paper deals with a new watermarking scheme in the time domain. The method tested follows up on a method that was presented in [1]. Compared with the method from [1] there are some changes in the new one, which improve the detection and extraction process. The watermark is embedded into the red and green components of a colour image. This has, on the one hand, an effect on the quality of watermarked image; on the other hand it increases the possibility of extracting the watermark even from very modified images. [ABSTRACT FROM AUTHOR]

Fast lifting wavelet transform is a technique which replaces standard discrete wavelet transform used in computation of wavelet coefficients. The idea of lifting comes from the lifting scheme, a method used in wavelet design. The standard method relies on convolution of the original signal with FIR filter structures. Fast lifting scheme basically breaks up the original filters into a series of smaller structures, providing a very sophisticated and versatile algorithm that is up to 50 % faster than the standard way with no extra memory requirements. This paper discusses an implementation of this algorithm in Java language, comparing both speed and efficiency of standard and fast lifting wavelet transform for CDF 9/7 filters, which are used in lossy image compression in JPEG2000 standard. Java has been chosen for its platform independent character and easy integration in mobile devices. [ABSTRACT FROM AUTHOR]

Images form integral part of interactive services broadcasted in digital television. Natural images compression is always trade-off between visual quality and file size. Annoying artifacts arise in highly compressed images. The scope of this article is to investigate the possibilities of image compression enhancement for interactive services. The aim is to decrease size of the image file in such way that the following post-processing compensates the drop of the visual quality. A low-complex post-processing technique is evaluated. Proposed solution is suitable for decreasing downloading time of the images in digital video broadcasting services. [ABSTRACT FROM AUTHOR]

Any Source Multicast (ASM) called Internet Standard Multicast (ISM) and its extension, Specific Source Multicast (SSM), are two known multicast technologies for delivering a data flow to a great number of customers over IP networks without cumulative bandwidth consumption. ASM technology is suitable for the many-to-many delivering model such as videoconferencing, where more sources are sending the traffic to one multicast group. SSM technology was developed as a solution for one-to-many delivering model such as the Internet Protocol Television (IPTV), where the receiver exactly defines the source of the multicast traffic. ASM and SSM can co-operate together on the network if specific conditions are complied with. The paper deals with describing the experiences and the measurement results from the implementation of these two multicast technologies in an experimental network. [ABSTRACT FROM AUTHOR]

For large-scale multimedia distributions, multicast is the preferred method of communication. ASM (Any Source Multicast) and SSM (Source-Specific Multicast) are the two types of multicast used. ASM is designed for either many-to-many or one-to-many communication. SSM is derived from ASM. SSM is used when only one session member is allowed to send data. An example use of SSM could be an IPTV broadcasting system over fixed or mobile network. The paper deals with describing hierarchical aggregation for feedback transmission in SSM. For the purpose of hierarchical aggregation, multicast receivers are organized into a tree structure. We present a tree structure consisting of end and summarization nodes. End nodes act as multicast receivers and summarization nodes perform feedback aggregation. The proposed MFCP (Multicast Feedback Control Protocol) is used to establish the tree structure and to exchange signalization needed for the feedback hierarchical aggregation. [ABSTRACT FROM AUTHOR]

The Internet Protocol Television has received much attention in recent years. It is a service that delivers media contents to costumers using the Real-time Transport Protocol and RTP Control Protocol. It brings many benefits for consumer and even for media distributors. IPTV is a specific application. It has only one sender and it should be able to offer its content to a huge number of receivers. As it is a new kind of service, there are still some problems to be solved. One of the most important is the Quality of Service (QoS) reporting delay and its dependence on the number of receivers in the session. The conventional RTP/RTCP architectures exceed acceptable range of the reporting interval with a relatively small number of receivers. This paper surveys the newest RTP/RTCP topologies and proposes a simulation model for further optimizations of algorithms and mathematical models for IPTV systems. [ABSTRACT FROM AUTHOR]

There exist a lot of methods for vision through an opaque medium. At present UWB (Ultra-Wideband) technology is used more and more because it is suitable for localization and detection of a human body behind a wall. First of all this paper describes known methods for vision through walls, which can be divided into two general groups - imaging and non-imaging systems. Secondly it describes the state of the art UWB radar for this application and its specifics. Finally it depicts our UWB radar system (centre frequency 4,7GHz) and our practical procedures relevant to the detection of a human body presented behind a concrete wall. [ABSTRACT FROM AUTHOR]

IMS is a good candidate to become the service platform for next generation networks (NGN). Among one of its key characteristics is the ability to keep the Internet paradigm of application and transport separation while designing interfaces between the two layers. In IMS there is an interaction between the CSCFs (call session control function), SIP proxies managing the application setup, and the PDF (Policy Decision Function), controlling the transport network. Still, the terminals have to perform the transport resource allocation (activating the PDP context). In future networks, a similar behavior is possible but also another approach can be followed: the PDF is in charge of allocating the transport resources between the terminals, allowing to reinforce the network control. In this paper we analyze and compare both approaches, including by resorting to simulation. [ABSTRACT FROM AUTHOR]

This paper proposes a door access control system with mobile phones which allows off-line delegations of an access. A model of door access control with mobile phones is introduced, and then the delegation is formalized as a copy of a door-key. On the previous model, secure copy by off-line is realized using the essential idea of the proxy signature. Moreover, the proposed system is implemented on mobile phones, and then the execution time of a copy and a verification are estimated. As a result, it is shown that the proposed system is feasible. [ABSTRACT FROM AUTHOR]

This paper deals with Radio Link Control protocol (RLC) in UMTS mobile network. It describes in brief the RLC protocol, its functions, properties, parameters, data structure and functional modes. In detail this study reports the acknowledged mode SDU discard procedure and its effect on the protocol performance. For the purpose of monitoring behavior of two RLC entities and performance evaluation of the RLC protocol with different values of RLC parameters a simulation program was developed. Graphic simulation outputs reporting the effect on performance are attached in the paper. [ABSTRACT FROM AUTHOR]

Knowledge of temperature-time curve for a certain time interval is needed in many scientific, medical and industrial applications. In some applications, however, the recorded temperature values in monitored time should be read wirelessly. Both requirements are defined especially for the transport of biological active substances. This set was applied in case study for continuous temperature data logging during a transport of chilled electrochemical TFT sensors with applied enzymes, highly sensitive to higher temperature limit exceeding. [ABSTRACT FROM AUTHOR]

RFID is automatic object identifying technology via radio frequency. And its application areas are un-describable for its convenience and pervasiveness. However, because the communication channel between the verifier and the tag is wireless, serious privacy problems such as the data leakage and the data traceability can be occur. Without resolving these privacy problems, RFID system cannot be adapted fully in any area. Many kinds of security protocols have been proposed to resolve these problems. However, previous proposals did not satisfy security requirements and still leaved vulnerabilities. In this paper, we describe the security vulnerabilities of previous works for RFID systems. Finally, we propose a security protocol which based on one-time pad scheme using random nonce and shared secret values. The proposed protocol satisfies security requirements such as the data secrecy, data anonymity and the data authenticity between the verifier and the tag. We have proved security requirements satisfaction formally by using GNY logic. [ABSTRACT FROM AUTHOR]

The plan of transmission parameters or the network plan was created for Czech Republic in 2005 and this plan has had key effect on traffic in the telecommunication networks providing public telephone service, including mobile networks, NGN networks based on IP protocol and private networks connected to public telephone network. This paper describes practical effects of aforesaid plan on some typical situations in the network. Related research projects of the Department of Telecommunications Engineering, Faculty of Electrical Engineering, CTU in Prague are presented here, such as tandem arrangement of codecs and non-intrusive monitoring of voice quality. [ABSTRACT FROM AUTHOR]

Diffserv, the most often used Quality of Service support technology, offers fast and efficient data flow processing. On the other hand these advantages are achieved at the cost of static, network-driven data-flow metering, classification, marking and queue management, which does not support any interaction with the end-user services. The following work offers a solution how to allow the end-user or end-system to cooperate with the edge router of a Diff-Serv domain and further increase the efficiency of the available QoS-support system. [ABSTRACT FROM AUTHOR]

When a peer in a public network opens a connection to another one being behind a network address translator, it encounters the network address translation problem. So called "UDP hole punching" approach allows to open a public-to-private or private-to-private network connection. This article deals with this approach to propose new security architecture for IPv4 communication introducing so called "implicit security" concept. Main contributions are ability to interconnect to any host behind NAT using just a host's domain name, enhanced mobility, and encryption and authentication of all data transmitted through this connection right from a packet sender to a local receiver. Secure channel is established on-demand automatically and is independent on any application. No additional modification of current NAT, IPv4 or DNS is required. [ABSTRACT FROM AUTHOR]

This paper is focused on the secure roaming problematic in wireless automation applications. Description of a roaming procedure and security issues is presented along with the newest techniques for fast roaming according to prepared network roaming standard IEEE802.11r and security trends defined in IEEE802.11i. Methods for minimizing handoff delay for wireless automation applications and requirements on the sufficient security level are also presented in this paper. [ABSTRACT FROM AUTHOR]

In this paper a new method of modulation classification is proposed. For the analysis, modulation signals and their spectrograms were obtained in the Matlab program. The classification method is based on spectrogram image recognition and it can discriminate between various digital signal modulations, such as FSK, BPSK, MSK, QPSK and QAM. The new method was tested using modulated signals corrupted by Gaussian noise, and it is well usable with signal-to-noise ratios as low as 10 dB. [ABSTRACT FROM AUTHOR]

The local and premises wireless networks have been expanding into many areas. The core network access point or basic station infrastructure can be made on wireless systems, on fixed cable systems with metallic twisted pairs, and, prospectively with optic fibers. The VDSL2 line systems with VDMT modulation and line bounding will be used for a data speed of hundreds Mb/s and distance between active nodes can be measured in hundreds meters. A suggestion of active access network and simulation of data bit rate is presented. [ABSTRACT FROM AUTHOR]

The paper discusses the NATO Network Enabled Capability concept, mainly from the communication point of view. The changes involve complete new requirements on the role of command and control to increase flexibility and effectiveness. Integration of Modeling and Simulation with Command, Control, and Information Systems increases the number of risks but it promises to leverage the projected capability and interoperability. [ABSTRACT FROM AUTHOR]

Institute of Computer Science of Masaryk University is working on the field of supporting medicine multimedia data transport archiving and processing more than ten years. Since first steps like transport of ultrasound and CT images across private fibre optics network these activities have grown up to regional PACS archive. Today more and more hospitals are participating on this project know under the name MediMed. For deployment of MediMed to some remote locations and especially to residence users (medicine specialists) it was necessary to utilise wireless and microwave technologies. Experiences with usage of wireless technology for delivery of medicine picture data are described in this paper. [ABSTRACT FROM AUTHOR]

Dynamic open environments demand trust negotiation systems for unknown entities willing to communicate. A security context has to be negotiated gradually in a fair peer to peer basis depending on the security level demanded by the application. Trust negotiation engines are driven by decision engines that lack of flexibility: depend on the implementation, policies languages or credentials types to be used. In this paper we present an agnostic engine able to combine all that information despite its origin or language allowing to select policies or requirements, credentials and resources to disclose, according to user preferences and context using iterative weighted Multidimensional Scaling to assist a mobile device during a trust negotiation. [ABSTRACT FROM AUTHOR]

This paper presents the saturation throughput analysis of IEEE 802.11g (ERP-OFDM) networks. The presented work is based on the Markov model previously introduced and validated by the authors in [7]. In the present paper the saturation throughput is evaluated in different channel conditions as a function of frame length. [ABSTRACT FROM AUTHOR]

The Faculty of Electrical Engineering and Communication of the Brno University of Technology offers several subjects focused on mobile communication networks. For practical exercises the experimental mobile network has been building at our faculty. As we do not have OMC or NMC in our network and as the low level network management is quite complex we designed the software that is useful tool for configuration and management of the network on the higher level. The paper deals with our experimental network and with software we have developed. [ABSTRACT FROM AUTHOR]

Modern communication services are more and more focused towards real time mobile multimedia applications like mobile video and Voice over IP. To assure sufficient Quality of Service control, appropriate measurements are needed. One of the most difficult tasks is to measure the exact value of one way delay, because very precise time synchronization between host and peer is needed. Most multimedia applications use JavaME platform and GPRS or EDGE technologies without any additional services or hardware. This leads to the very challenging task: To assure precise time synchronization using application layer and high latency networks. [ABSTRACT FROM AUTHOR]

Scheduling algorithms are fundamental components in the process of resource management in mobile communication networks with heterogeneous QoS requirements such as delay, delay jitter, packet loss rate or throughput. The random characteristics of the propagation environment and the use of complex physical layers in order to combat this random behavior further complicates the design of simple, efficient, scalable and fair scheduling algorithms. This paper presents the main criteria used in the design of scheduling algorithms for 3G/4G mobile communications networks and provides a survey of scheduling mechanisms proposed for use in TDMA and CDMA based systems. [ABSTRACT FROM AUTHOR]