Home  About us  Contact
 

Telecommunication Systems (telecommunication + system)

Distribution by Scientific Domains
Engineering46%
Information Science and Computing26%

Kinds of Telecommunication Systems

  • mobile telecommunication system
    		•
  • universal mobile telecommunication system
    		•

    Selected Abstracts

    The long term evolution towards a new 3GPP* air interface standard

    BELL LABS TECHNICAL JOURNAL, Issue 4 2007
    Rainer Bachl
    The performance targets for the long term evolution (LTE) of the Universal Mobile Telecommunication System (UMTS) into a 4th generation system have been chosen to be very ambitious. While all of these targets may not be achievable in practice, they have served to motivate the decisions for a particular LTE design. Specifically, we discuss the choice of the multiple access scheme for LTE, provide details on the uplink and downlink transmission formats, analyze the benefits of multiple input multiple output (MIMO), and outline approaches for intercell interference mitigation. The trade-off between usage of MIMO spatial multiplexing and beamforming is shown for a practical system. The required signaling overhead is weighed against the performance improvements available from the additional information. Finally, some examples for the achievable physical layer performance are given. © 2007 Alcatel-Lucent. [source]

    Reactive oxygen species formation is not enhanced by exposure to UMTS 1950 MHz radiation and co-exposure to ferrous ions in Jurkat cells

    BIOELECTROMAGNETICS, Issue 7 2009
    Francesca Brescia
    Abstract This study was designed to assess if radiofrequency (RF) radiation induces oxidative stress in cultured mammalian cells when given alone or in combination with ferrous ions (FeSO4). For this purpose the production of reactive oxygen species (ROS) was measured by flow cytometry in human lymphoblastoid cells exposed to 1950 MHz signal used by the third generation wireless technology of the Universal Mobile Telecommunication System (UMTS) at Specific Absorption Rate of 0.5 and 2.0 W/kg. Short (5,60 min) or long (24 h) duration exposures were carried out in a waveguide system under strictly controlled conditions of both dosimetry and environment. Cell viability was also measured after 24 h RF exposure using the Resazurin and Neutral Red assays. Several co-exposure protocols were applied to test if RF radiation is able to alter ROS formation induced by FeSO4 (RF given before or concurrently to FeSO4). The results obtained indicate that non-thermal RF exposures do not increase spontaneous ROS formation in any of the experimental conditions investigated. Consistent with the lack of ROS production, no change in cell viability was observed in Jurkat cells exposed to RF radiation for 24 h. Similar results were obtained when co-exposures were considered: combined exposures to RF radiation and FeSO4 did not increase ROS formation induced by the chemical treatment alone. In contrast, in cultures treated with FeSO4 as positive control, a dose-dependent increase in ROS formation was recorded, validating the sensitivity of the method employed. Bioelectromagnetics 30:525,535, 2009. © 2009 Wiley-Liss, Inc. [source]

    Cognitive function and symptoms in adults and adolescents in relation to rf radiation from UMTS base stations

    BIOELECTROMAGNETICS, Issue 4 2008
    Ingunn S. Riddervold
    Abstract There is widespread public concern about the potential adverse health effects of mobile phones in general and their associated base stations in particular. This study was designed to investigate the acute effects of radio frequency (RF) electromagnetic fields (EMF) emitted by the Universal Mobile Telecommunication System (UMTS) mobile phone base stations on human cognitive function and symptoms. Forty adolescents (15,16 years) and 40 adults (25,40 years) were exposed to four conditions: (1) sham, (2) a Continuous Wave (CW) at 2140 MHz, (3) a signal at 2140 MHz modulated as UMTS and (4) UMTS at 2140 MHz including all control features in a randomized, double blinded cross-over design. Each exposure lasted 45 min. During exposure the participants performed different cognitive tasks with the Trail Making B (TMB) test as the main outcome and completed a questionnaire measuring self reported subjective symptoms. No statistically significant differences between the UMTS and sham conditions were found for performance on TMB. For the adults, the estimated difference between UMTS and sham was ,3.2% (,9.2%; 2.9%) and for the adolescents 5.5% (,1.1%; 12.2%). No significant changes were found in any of the cognitive tasks. An increase in ,headache rating' was observed when data from the adolescents and adults were combined (P,=,0.027), an effect that may be due to differences at baseline. In conclusion, the primary hypothesis that UMTS radiation reduces general performance in the TMB test was not confirmed. However, we suggest that the hypothesis of subjective symptoms and EMF exposure needs further research. Bioelectromagnetics 29:257,267, 2008. © 2007 Wiley-Liss, Inc. [source]

    Evaluation of genotoxic effects in human leukocytes after in vitro exposure to 1950 MHz UMTS radiofrequency field

    BIOELECTROMAGNETICS, Issue 3 2008
    O. Zeni
    Abstract In the present study the third generation wireless technology of the Universal Mobile Telecommunication System (UMTS) signal was investigated for the induction of genotoxic effects in human leukocytes. Peripheral blood from six healthy donors was used and, for each donor, intermittent exposures (6 min RF on, 2 h RF off) at the frequency of 1950 MHz were conducted at a specific absorption rate of 2.2 W/kg. The exposures were performed in a transverse electro magnetic (TEM) cell hosted in an incubator under strictly controlled conditions of temperature and dosimetry. Following long duration intermittent RF exposures (from 24 to 68 h) in different stages of the cell cycle, micronucleus formation was evaluated by applying the cytokinesis block micronucleus assay, which also provides information on cell division kinetics. Primary DNA damage (strand breaks/alkali labile sites) was also investigated following 24 h of intermittent RF exposures, by applying the alkaline single cell gel electrophoresis (SCG)/comet assay. Positive controls were included by treating cell cultures with Mitomycin-C and methylmethanesulfonate for micronucleus and comet assays, respectively. The results obtained indicate that intermittent exposures of human lymphocytes in different stages of cell cycle do not induce either an increase in micronucleated cells, or change in cell cycle kinetics; moreover, 24 h intermittent exposures also fail to affect DNA structure of human leukocytes soon after the exposures, likely indicating that repairable DNA damage was not induced. Bioelectromagnetics 29:177,184, 2008. © 2007 Wiley-Liss, Inc. [source]

    Split agent-based routing in interconnected networks

    INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 4 2004
    Constandinos X. Mavromoustakis
    Abstract Adaptive behaviour of swarm-based agents (BT Technol. J. 1994; 12:104,113; AAMAS Conference '02, Melbourne, Australia, Month 1,2, 2002; Softcomput. J. 2001; 5(4):313,317.) is being studied in this paper with respect to network throughput for a certain amount of data traffic. Algorithmically complex problems like routing data packets in a network need to be faced with a dynamically adaptive approach such as agent-based scheme. Particularly in interconnected networks where multiple networks are participating in order to figure a large-scale network with different QoS levels and heterogeneity in the service of delay sensitive packets, routing algorithm must adopt in frequent network changes to anticipate such situations. Split agent-based routing technique (SART) is a variant of swarm-based routing (Adapt. Behav. 1997; 5:169,207; Proceedings of 2003 International Symposium on Performance Evaluation of Computer and Telecommunication Systems,SPECTS, Montreal, Canada, July 20,24, 2003; 240,247.) where agents are split after their departure to the next node on a hop-by-hop basis. Packets that are delay sensitive are marked as prioritized which agents recognize-as being a part of a packet- and try to influence the two-way routing tables. Thorough examination is made, for the performance of the proposed algorithm in the network and the QoS offered, taking into account a number of metrics. It is shown that the split agent routing scheme applied to interconnected networks offers a decentralized control in the network and an efficient way to increase overall performance and packet control reducing at the same time the packet loss concept. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    Scheduling streaming flows on the downlink shared channel of UMTS

    INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 2 2007
    Joy Kuri
    In Universal Mobile Telecommunication Systems (UMTS), the Downlink Shared Channel (DSCH) may be used to provide streaming services. The traffic model for streaming services is different from the continuously backlogged model used in much of the literature. Each connection specifies a required service rate over an interval of time. In this paper, we are interested in determining how k DSCH frames should be allocated among a set of I connections. We need a scheduler that is channel-aware, so that channels presently enjoying low fading losses can be exploited to achieve higher aggregate throughput. On the other hand, the scheduler is also required to be fair, so that each connection obtains a throughput as close as possible to what it requires. We introduce the notion of discrepancy to capture the inherent trade-off between aggregate throughput and fairness. We show that the discrepancy criterion provides a flexible means for balancing efficiency, as measured by aggregate throughput, and fairness. Our problem, then, is to schedule mobiles so as to minimize the discrepancy over the control horizon. We provide a simple low-complexity heuristic called ITEM that is provably optimal in certain cases. In particular, we show that ITEM is optimal when applied in the UMTS context. Next, we compare the performance of ITEM with that of other algorithms, and show that it performs better in terms of both fairness and aggregate throughput. Thus, ITEM provides benefits in both dimensions,fairness and efficiency,and is therefore a promising algorithm for scheduling streaming connections. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Trends in the start of the wet season over Africa

    INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2009
    D. R. Kniveton
    Abstract A quarter of a century of daily rainfall data from the Global Telecommunications System are used to define the temporal and spatial variability of the start of the wet season over Africa and surrounding extreme south of Europe and parts of the Middle East. From 1978 to 2002, the start of the wet season arrived later in the year for the majority of the region, as time progressed. In some parts of the continent, there was an annual increase in the start date of up to 4 days per year. On average, the start of the wet season arrived 9,21 days later from 1978 to 2002, depending on the threshold used to define the start of the rains (varying from 10,30 mm over 2 days, with no dry period in the following 10 days). It is noted that the inter-annual variability of the start of the wet season is high with the range of start dates varying on average from 116 to 142 days dependent on the threshold used to determine the start date. These results may have important implications for agriculturists on all levels (from the individual farmer to those responsible for regional food supply), as knowledge of potential future climate changes starts to play an increasingly important role in the agricultural decision-making process, such as sowing and harvesting times. Copyright © 2008 Royal Meteorological Society [source]

    EMC internal patch antenna integrated with a U-shaped shielding metal case for mobile device application

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2006
    Chih-Ming Su
    Abstract A novel integration design of a shorted patch antenna and a U-shaped shielding metal case for application in a mobile communication device is presented. The shorted patch antenna is mounted within the dented portion of the U-shaped shielding metal case, which can provide a coupling-free space for accommodating electronic components such as the RF modules/circuitry and battery in the mobile device. Thus, in this case, the shorted patch antenna can operate as an internal antenna having an electromagnetic compatibility (EMC) property with nearby electronic components. In addition, with the proposed integration design, the shorted patch antenna is isolated from the two side edges of the system ground plane of the mobile device. Hence, it can be expected that the effects of the user's hand on the performances of the antenna will be suppressed. The proposed integration design applied to a smart phone for Universal Mobile Telecommunications System (UMTS, 1920,2170 MHz) operation is studied. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1157,1161, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21552 [source]

    Performance assessment of next-generation wireless mobile systems

    BELL LABS TECHNICAL JOURNAL, Issue 4 2009
    Krishna Balachandran
    The deployment of third generation (3G) systems such as Universal Mobile Telecommunications System (UMTS) and code division multiple access (CDMA) 1X is now ubiquitous. Furthermore, several operators have already deployed evolved 3G systems such as high speed packet access (HSPA) and 1× evolution data optimized (1× EV-DO). These 3G and evolved 3G systems are based on spread spectrum technologies. Now the industry has begun to focus on next-generation wireless systems based on orthogonal frequency division multiplexing (OFDM) technology, flat-Internet Protocol (IP) architectures, and advanced multiple input-multiple output (MIMO) capabilities. These next-generation technologies, primarily are: 3rd Generation Partnership Project (3GPP)-based evolved UMTS terrestrial radio access network (EUTRAN), also called Long Term Evolution (LTE); 3rd Generation Partnership Project 2 (3GPP2)-based Ultra Mobile Broadband (UMB); and Institute of Electrical and Electronics Engineers (IEEE) 802. 16e-based Worldwide Interoperability for Microwave Access (WiMAX). These technologies are in the final specifications to initial deployment phases in selected markets. This paper provides an overview and performance analysis of these next-generation technologies based on their initial releases. Additionally, a comparative performance analysis of these technologies is also presented. © 2009 Alcatel-Lucent. [source]

    Evolution of UMTS toward high-speed downlink packet access

    BELL LABS TECHNICAL JOURNAL, Issue 3 2002
    Arnab Das
    An expanded effort is under way to support the evolution of the Universal Mobile Telecommunications System (UMTS) standard to meet the rapidly developing needs associated with wireless data applications. A new, shared channel,the high-speed downlink shared channel (HS-DSCH),provides support to packet-switched high-speed data users. A number of performance-enhancing technologies are included in the high-speed downlink packet access (HSDPA) system to ensure high peak and average packet data rates while supporting circuit-switched voice and packet data on the same carrier. Lucent Technologies took a pivotal role in specifying many of these techniques, including adaptive modulation and coding (AMC), hybrid automatic repeat request (HARQ), and fat-pipe scheduling. In this paper, we provide system-level simulations results to indicate the achievable performance and capacity with these advanced technologies. We also discuss HSDPA protocol architecture along with the uplink and downlink control channel design and performance. We conclude with a discussion of potential enhancements for the future. © 2003 Lucent Technologies Inc. [source]

    Quality of service in UMTS wireless networks

    BELL LABS TECHNICAL JOURNAL, Issue 2 2002
    Suresh Kumar
    This paper presents the realization of quality of service (QoS) in the Universal Mobile Telecommunications System (UMTS) network. The paper introduces an overview of the UMTS network structure that is an evolution of the Global System for Mobile Communications/General Packet Radio Service (GSM/GPRS) along with the motivation for providing QoS, as well as the QoS model in UMTS. Additionally, relevant considerations in delivering successful end-to-end QoS across a UMTS network are discussed. We also discuss trends toward QoS along with core concepts of QoS. The paper concludes with an outline of ongoing exploration of potential areas for future work. © 2002 Lucent Technologies Inc. [source]

    The support of mobile internet applications in UMTS networks through the open service access

    BELL LABS TECHNICAL JOURNAL, Issue 2 2001
    Musa R. Unmehopa
    Third-generation wireless networks are expected to enable the mobile Internet to become a reality, offering fast Internet access and high-speed data services to mobile subscribers. For network operators to allow for the rapid development of innovative value-added applications on the scale seen in the Internet today, the wireless core network needs to be opened up for third-party applications provided by independent software vendors (ISVs). The Third-Generation Partnership Project (3GPP) is currently working on the production of technical specifications to provide a mechanism that would permit ISVs a standard interface to access network capabilities traditionally available to network operators. Within 3GPP, this mechanism is commonly referred to as the open service access (OSA). This open service access is predominantly targeted at Universal Mobile Telecommunications System (UMTS) networks, allowing application developers to access the feature-rich core network capabilities. This open access enables network operators to offer innovative services to their subscribers allowing the ability to differentiate themselves in a competitive market. With the imminent commercial deployment of the General Packet Radio Service (GPRS), existing fixed-line Internet service providers (ISPs) can now offer mobile Internet to end users in a UMTS environment where the responsibility of the network operator is reduced to providing IP connectivity. The increased competition from ISPs poses a big threat to the revenue stream of the network operator. This paper explores the possibilities of OSA to facilitate network operators in providing the mutual support of network capabilities and Internet content. These possibilities would allow the network operator to become a value-added mobile Internet service provider (VAM-ISP). © 2002 Lucent Technologies Inc. [source]

    Dynamic bandwidth recycle algorithm for OVSF,CDMA systems

    INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2006
    Peng-Jung Wu
    Abstract This paper presents a dynamic bandwidth recycle algorithm in the downlink of a WCDMA system using orthogonal variable spreading factor codes (OVSF). It consists of a bandwidth recycle algorithm and a bandwidth reservation algorithm. The bandwidth recycle algorithm is used to recycle bandwidth from current serviced connections when the system does not have enough available bandwidth to support a bandwidth request. The bandwidth reservation algorithm is used to reduce transmission delay caused by suddenly increasing bandwidth requests. Four traffic classes, conversational, streaming, interactive, and background classes, defined by universal mobile telecommunication system (UMTS) are considered. Simulation results show that the bandwidth utilization and block rate are improved, the bandwidth guaranteed to conversational and streaming classes are protected, and the delay time of interactive and background classes are kept under an acceptable value even when the traffic load is heavy. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Small antennas application in portable phones

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008
    Sheng-Yi Huang
    Abstract The compact antennas are introduced, which are working in universal mobile telecommunication system (UMTS) of 1920,2170 MHz and digital video broadcast-handheld (DVB-H+) of 1452,1492 MHz for portable phones applications. The resonant frequency of UMTS is presented by using a planar inverted-F antenna (PIFA) element. The other resonant frequency of DVB-H+ is presented by using meander-line configurations. The ratio of impedance bandwidth of the PIFA antenna to the center frequency 1500 MHz is 29% (DVB-H+). The ratio of impedance bandwidth of the meander radiator to the center frequency 2100 MHz is 20% (UMTS). The size of the two antennas is shortened to 65% compared to general internal radiators. The total volume of the two radiators is 40 (L) × 5 (W) × 0.2 (H) mm3 (PIFA) and 20 (L) × 5 (W) × 0.2 (H) mm3 (meander radiator), respectively. The experimental results are compared to the numerical simulation, high-frequency structure simulator, for agreement. The good performances of the antennas like wide bandwidth and omnidirectional far-field patterns can be obtained. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3020,3023, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23872 [source]

    Frequency domain equalisation in CDMA detection

    EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 2 2008
    Ihan Martoyo
    The present paper introduces frequency domain equalisation (FDE) as an efficient means for single-user detection (SUD) in universal mobile telecommunication systems (UMTS) handhelds. Such an SUD is, at least partially, able to remove multiple access interference (MAI) like a multi-user detector (MUD), however with several important advantages the operation principle of an FDE-SUD is simple and easy to understand, the FDE-SUD shows low numerical complexity and therefore, it is not power hungry like an MUD. The problem of applying FDE without zero-padding or cyclic-prefix insertion is solved by using the overlap-cut method. In this paper we also prove that the performance of the FDE-SUD is practically identical to that of linear MUD for a fully loaded UMTS cell. Furthermore, armed with the idea of FDE for code division multiple access (CDMA), we can construct a common receiver structure for CDMA, time division multiple access (TDMA), orthogonal frequency division multiplexing (OFDM) and multi-carrier CDMA (MC-CDMA) systems. This is an extremely useful idea in enabling a software-defined radio (SDR) which can operate seamlessly in several environments such as UMTS, the IEEE 802.11a and WiMaX. FDE based receivers could be one important building-block for the next generation mobile communications. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Performance analysis of wireless multihop diversity systems

    INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2008
    Diomidis S. Michalopoulos
    Abstract We study the performance of multihop diversity systems with non-regenerative relays over independent and non-identical Rayleigh fading channels. The analysis is based on the evaluation of the instantaneous end-to-end signal-to-noise ratio (SNR), depending on the type of the relay and the diversity scheme used. A closed-form expression is derived for the average end-to-end SNR, when fixed-gain relays and a maximal ratio combiner are used; also, an analytical expression formula for the average symbol-error rate (ASER) for the above case is presented. The results show that, as expected, multihop diversity systems outperform conventional telecommunication systems in terms of ASER when the same amount of energy is assumed to be consumed in both cases. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    The EMF uncertainty problem related to mobile phones: where do consumers place their trust?

    INTERNATIONAL JOURNAL OF CONSUMER STUDIES, Issue 2 2010
    Lisbet Berg
    Abstract This paper addresses the uncertainty problem, i.e. cases characterized by lack of knowledge or scientific uncertainty. In such situations, it can be hard for consumers to ,voice' or practise consumer power. One field characterized by the uncertainty problem is electromagnetic radiation. An explicit goal of this study has been to articulate Norwegian consumers' practices, attitudes and beliefs regarding electromagnetic radiation from mobile phones to public authorities and consumer policy makers. The study was based on 1000 telephone interviews collected in 2008. Today, experts disagree on the potential health effects of radiation from electromagnetic fields (EMF), as well as standards for safe limits of exposure to mobile phones, base stations and wireless telecommunication systems. In addition, complicated technology and extremely rapid product development and diffusion leave consumers' security considerations to their own beliefs and trust. Whether or not electromagnetic radiation from mobile phones constitutes a health hazard will not be addressed in this paper. Rather, it will focus on how consumers react to this situation of uncertainty. The material reveals four main ways in which consumers can solve what we have named the EMF uncertainty problem: the confident and comfortable way, the sceptical and cautious way, the responsible and good citizen way, and finally, the neglecting way. The paper also discusses the precautionary principle related to EMF. Who should be precautionary: the public authorities, the mobile phone industry or the consumers themselves? We believe that a consistent governmental precautionary policy in combination with consumers taking their own precautionary measures is a viable solution. In this way, all consumers would be addressed and aided when navigating this field of uncertainty. [source]

    Seasonal and diurnal variations of total attenuation measured with the ITALSAT satellite at Spino d'Adda at 18.7, 39.6 and 49.5 GHz

    INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 4 2004
    Carlo Riva
    Abstract The ITALSAT satellite experiment started in January 1991 and ended in January 2001, permitting an extensive program of propagation measurements at 18.7, 39.6 and 49.5 GHz. In these frequency bands, up- and down-links experience severe signal attenuation due to meteorological effects such as those due to gas (oxygen and water vapour), clouds, turbulence and, especially, rain. The propagation measurement campaigns aim mainly at assessing and at modelling the appropriate fade margin compensating propagation attenuation in the design of satellite communication systems. This margin depends significantly on the season and on the time of the day, due to variations of meteorological conditions. This paper reports the results obtained from copolar signal measurements carried out at the Earth station of Spino d'Adda, near Milano (North Italy), at the three frequencies during 7 years (from 1994 to 2000). The measured cumulative distribution functions of total attenuation are compared to ITU-R models' prediction. Moreover the statistics conditioned to single months of the year, seasons and 4 h contiguous periods of the day are also shown. These statistics can be useful for telecommunication systems whose service quality and design must be matched to the season of the year or the time of the day. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    The development and evaluation of a telepsychiatry service for prisoners

    JOURNAL OF PSYCHIATRIC & MENTAL HEALTH NURSING, Issue 4 2004
    S. LEONARD bsc rn (mm) dip ndip b&fdip ptsdcounselling
    The introduction of increasingly sophisticated telecommunication systems seems to offer opportunities to respond to some of the key problems around structural and spatial inequalities in access to health care. There is evidence which suggests that serious mental health problems are common among prisoners and psychiatric comorbidity is the norm. Many prisoners have complex mental health needs, but more often than not these remain unaddressed. Telepsychiatry is one strategy to improve the accessibility and quality of mental health care in the prison setting. This paper firstly reviews the current prison health care system and then describes a research study which is focused on the development and evaluation of a telepsychiatry service for prisoners. This study has investigated what is lost or gained in a psychiatric assessment when it is conducted via telepsychiatry. The researcher compared the inter-rater reliability between two raters interviewing 80 participants in an observer/interviewer split configuration in telepsychiatry and same room settings. The measure used was the Comprehensive Psychopathology Rating Scale. Prisoners and prison staff also took part in semi-structured interviews which focused on their satisfaction and acceptability of the telepsychiatry service. A cost comparison of the telepsychiatry service with the existing visiting service was conducted. This paper outlines the study design and focuses on the potential impact that telepsychiatry may have upon the practice setting. [source]

    Total System Reliability: Integrated Model for Growth and Test Termination

    QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 4 2005
    John Donovan
    Abstract Reliability demonstration testing is not the most efficient method of assuring product reliability prior to shipment. It is costly, time consuming and has inherent technical and social limitations. The dilemma facing the reliability and quality engineer is whether to continue demonstration testing and risk shipping a product late or ship the product and risk warranty and field service returns. Either option can cause the company to lose significant market share and profit. This paper sets out to solve this dilemma by meeting both the time to market constraints and the product reliability goals. The weaknesses of existing reliability demonstration techniques are explored and a comprehensive methodology is introduced involving controlled development processes, stress testing, root cause determination and process change feedback mechanisms. All prototype products are manufactured on the final volume process line resulting in the early identification and correction of process-related problems. Testing commences on the first available prototypes with system stress/robust testing being employed to stimulate failures, determine their root cause and correct them. Reliability growth modelling assesses the ongoing improvements occurring in reliability during the development cycle, while a statistical stopping rule is used to determine the optimal product release time without risking product warranty. The approach is applicable to systems incorporating both hardware and software elements. The methodology has been validated on three development projects of telecommunication systems comprising hardware and software. In addition to enhancing team behaviour and performance, the development times have been reduced by 14% and the ramp-up time to full worldwide product shipments has been reduced by 50%. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    InP DHBT circuits: From device physics to 40Gb/s and 100Gb/s transmission system experiments

    BELL LABS TECHNICAL JOURNAL, Issue 3 2009
    Nils Weimann
    The capacity of fiber-optic telecommunication systems can be increased by higher data rate signaling. We present key analog and digital circuits which find application as building blocks in future very high data rate systems. The circuits are fabricated in our indium phosphide (InP) double-heterojunction bipolar transistor (DHBT) technology. The physical properties of the InP material system, notably high breakdown and high electron mobility, enable functions that are not accessible with current silicon-based high-speed technologies, including SiGe. Device and circuit results are presented, and we report on transmission system experiments conducted with these InP DHBT circuits. © 2009 Alcatel-Lucent. [source]

    Joint spectrum and power optimization in the design of the UMTS satellite component

    INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2001
    Ernestina Cianca
    Abstract The paper provides a power and spectrum joint analysis of the universal mobile telecommunications system (UMTS) satellite component, based on the wideband code division multiple access (W-CDMA) air interface. In fact, power and spectral efficiency may become highly conflicting requirements in a satellite system and a trade-off analysis is needed to drive a proper dimensioning of the satellite. The proposed approach allows a dimensioning of the satellite component either in terms of orbit and power budget or in terms of additional capacity for the terrestrial section, for specified orbit and power limitations. The impact of candidate frequency bands, orbit type and diversity on both spectral and power requirements of the satellite component is evaluated. For given traffic requirements, power-vs-spectrum trade-off is proposed which ensures a proper resources utilization. The efficiency evaluation accounts for: beams overlapping, ortho gonality, voice activity factor, diversity and cross-polarization frequency reuse. Perfect power control is assumed and the effect of the excess power required by the shadowed users is accounted for in the interference calculation. Furthermore, still in the frame of a proper resource exploitation, a possible optimization of capacity through the use of unpaired bands in the two link directions is analysed. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    A dual-band antenna design for GPS and UMTS applications

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2007
    Chow-Yen-Desmond Sim
    Abstract The design of an integrated dual-band antenna for global positioning system (GPS) and universal mobile telecommunications system (UMTS) is presented. A circularly polarized square-ring corner truncated microstrip antenna is designed for GPS application, and a monopolar shorted square patch antenna embedded within the center of the square-ring is designed for UMTS application. Both proposed antenna elements demonstrated desirable isolation, radiation pattern; polarization, and bandwidth requirement. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1935,1939, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22597 [source]

    Generic UMTS test signal for RF bioelectromagnetic studies

    BIOELECTROMAGNETICS, Issue 6 2004
    H. Ndoumbč Mbonjo Mbonjo
    Abstract This report outlines the characteristics of universal mobile telecommunications system (UMTS) signals and discusses the signal parameters with respect to their possible biological relevance in order to define a generic UMTS test signal (GUS) for experiments aiming at the investigation of biological effects of weak electromagnetic fields. The GUS includes features of a real UMTS signal and especially the characteristics of UMTS, which differ from those of already applied second generation mobile communication systems (GSM 900, DCS1800, PCS1900, IS-95). It has been specified on the basis of the recommendations of a working group of the German Forschungsgemeinschaft Funk (FGF) with a focus on the mechanisms of UMTS which are responsible for slow term signal contributions, i.e., low frequency variations of the radio frequency (RF) envelope, since the hypothetical possibility of biological relevance of weak electromagnetic fields is often attributed to time variations of the RF envelope with frequencies close to those of natural processes. In this respect, it is also shown that the mandatory power control loop in UMTS gives rise to very strong 1.5 kHz variations on the air interface. Based upon the concept of the GUS, a UMTS test signal generator (GUS6960S) is described. Bioelectromagnetics 25:415,425, 2004. © 2004 Wiley-Liss, Inc. [source]

    Satellite rural communications: telephony and narrowband networks

    INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2005
    Roberto Conte
    Abstract Rural communications are important for large and developing countries, and telecommunications systems have been implemented depending upon the available technology at the time. Rural users do not generate the same amount of revenue as urban users do, thus lowering incentives for rural telecommunications investment with service to those regions delayed as long as possible. Voice and data communications are essential to the economic development of a region, and it has been shown that traffic increases rapidly as soon as the service is available. Satellite-based digital networks provide efficient long-distance service to rural communities at lower cost than similar land-based wired networks with acceptable quality. Small earth stations along with Wireless Local Loops can provide both local and long-distance service efficiently and at low cost, offering digital multimedia services on a global scale. This paper focuses on the description of different narrowband technologies used to service rural communities, namely basic telephone and low-bit-rate data (<64 kbps) applications through the use of satellite and terrestrial wireless systems. A basic network economic planning description is presented, and important parameters such as satellite network size, topology and multiple access are identified in order to improve the process of effective and cost-efficient rural communications network design. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Microstrip antennas for cellular and wireless communication systems

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2002
    obodzian
    Abstract The Letter describes problems related to use of microstrip antennas in cellular and wireless telecommunications systems. Because of the unique properties, microstrip technology is nowadays often used to manufacture small internal antennas for portable terminals as well as antenna arrays for base stations. It also seems to be a very promising technology for multisystem antennas, for which there is an ever-growing demand. The Letter also presents a short overview of currently available solutions and ones under development by the authors, along with some key problems related to their design. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 380,384, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10468 [source]