bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some practical issues in the design and application of a VLSI FEC chip
Authors: Wang Qiang , Nicholson Robert D. , Onotera Larry Y. 
Published: July 2007

AbstractForward error correction (FEC) has become a general requirement for digital satellite communications. The dominant technology is the use of convolutional codes with Viterbi decoding. At MPR (Microtel Pacific Research), a single‐chip VLSI implementation of a convolutional encoder and Viterbi decoder for constraint length 7 has been completed recently. In the design and application of the FEC chip, several practical issues had to be addressed. These include the determination of the maximum variation in path metric, generation of a convolutional encoded sequence with maximum number of transitions for symbol timing recovery, use of a unique word to detect the phase ambiguity, use of a sliding window data quality monitor to resolve an ambiguous state, etc. This paper presents our solutions to these problems. Although specific results are given for the standard constraint‐length 7 code, the methods used to obtain these results are general and can be applied to other codes. Features and implementation of the VLSI FEC chip are also discussed.
Efficient ARQ schemes for error control of satellite channels
Authors: Fantacci Romano 
Published: July 2007

AbstractIn this paper, the performance of some efficient ARQ schemes which make use of repeated transmissions of the same data block and compound detection are analysed. The repeated transmission of the same data block involves repeated transmission of each symbol of the data block. At the receiving end, compound detection formed of a soft detection jointly with a classical hard detection is performed by using all the received copies of the same symbol. The throughput efficiencies for the proposed ARQ schemes are analytically derived in closed form and optimized with respect to the number of copies to be transmitted for each data block. It will be shown that the optimized ARQ schemes proposed in this paper achieve better performance than classical ARQ schemes, in particular under high error rate conditions.
Design of saw filters in SS‐FDMA routers for mobile satellite systems
Authors: Ananasso Fulvio , Deacon John M. 
Published: July 2007

AbstractThe present paper reports the design of a SAW filter bank consisting of 26 linear phase filters with bandwidths ranging from 60 to 2180 kHz, 0·5/40 dB transition width narrower than 30 kHz and stopband rejection as high as possible. Passbank amplitude and phase ripple limits are 1 dB and 4° peak‐to‐peak respectively. Three candidate filters of bandwidth 60 kHz, 400 kHz and 2·180 MHz were selected for detailed design, taking into account spurious effects such as acoustic regeneration and diffraction as well as technology limits. Since the physical length of a SAW filter—as any transversal (FIR) filter—is determined by (i) the required passband amplitude ripple, (ii) the stopband rejection level and (iii) the transition width, the steepness of the required passband‐to‐stop band transitions in these filters dictates their physical size to be unusually large, resulting in an overall size for each packaged filter of 360 × 38 × 17 mm, i.e. 14·2 × 1·5 × 0·7 inches. The electrical specifications are met by all but the 2180 kHz filter, whose shape factor, for a 30 kHz transition band, would be 1·027 : 1, beyond the state of the art. The filter bank has about 27 dB insertion loss per filter, plus roughly 14 dB (1 : 26) power split loss.
Land mobile communications in Ku‐band. Results of a test campaign on eutelsat I‐F1
Authors: Dutronc J. , Colcy J. N. 
Published: July 2007

AbstractThis paper presents and discusses the results of technical tests on land mobile communications conducted in June and July 1989 in Europe using a EUTELSAT satellite. The land mobile communication system under test was that already operated by QUALCOMM in the U.S.A. under the registered name OmniTRACS.The field trial was organized in conjunction with the Signatories who expressed to EUTELSAT an interest in a full‐scale technical investigation of the system. The aim of the field trial was to evaluate the technical characteristics of the system and test its performance in different operating conditions.The results establish the relationship between transmission performance (i.e. essentially the required number of transmission attempts in order to get a message through the communication channel), and the environment of the land mobile, the satellite transponder's mode of operations and the interference conditions.
The joint African radiometric propagation measurement programme
Authors: Arbesser‐Rastburg B. , Zaks C. , McCarthy D. K. , Rogers D. V. , Allnutt J. E. 
Published: July 2007

AbstractThis paper summarizes the principal aspects of a major co‐operative radiowave propagation experiment that was designed to collect data for improving rain attenuation prediction models for tropical Africa. A pressing need for such data had previously been identified by Resolution 79 of the CCIR. In a unique joint arrangement with three African governments, INTELSAT, COMSAT, the U.S. Agency for International Development, the U.S. National Telecommunications and Information Administration and the U.S. Telecommunications Training Institute (USTTI) collaborated in setting up a Ku‐band radiometric measurement campaign in Cameroon, Kenya and Nigeria. A brief historical overview is given, together with the major technical parameters of the sites and the equipment installed there. The anticipated characteristics of the three locations are outlined with regard to meteorological and propagation conditions, and some preliminary indications of the results are presented based on an inspection of the early event data.
Tropical rainfall drop‐size distribution
Authors: Maciel Leandro R. , Assis Mauro S. 
Published: July 2007

AbstractBased on disdrometer measurements carried out in Brazil, this paper discusses the problem of rainfall drop‐size distribution in tropical areas and its effect on radiowave propagation at frequencies above 10 GHz. A comparison between Laws and Parsons and lognormal models is made. In spite of the best fit to the experimental data shown by the lognormal distribution, in the range from 10 to 20 GHz there is no significant difference between the two models. However, as the frequency increases this difference becomes larger and may be an important source of error in the design of both terrestrial and satellite links in low‐latitude regions. Similar results from Nigeria (Africa) are also taken into account.
Preliminary plans for a propagation experiment in Mali
Authors: Haidara Fatim , Pratt Timothy , Bostian Charles W. 
Published: July 2007

AbstractMeasurements of propagation effects on satellite down‐links to tropical locations are rare. This paper describes two experiments that will provide new and useful data for radiowave propagation in tropical Africa. A discussion of the African tropical climate is included that shows the wide range of rainfall patterns throughout the continent. Also, the broad distribution of climate in Mali, the West African country where the experiments will be located, is described. A rain‐rate measurement programme involving autonomous terminals based on tipping bucket rain‐gauges is presented. An experiment measuring the slant‐path attenuation of the 12·5 GHz beacon of the ESA satellite OLYMPUS is described. The paper also discusses how the measured data in both experiments will be relayed daily from Mali to Virginia Tech by the low earth orbit satellite VaSTAR.
M‐ary FSK with limiter discriminator integrator detection and DPSK with differential phase detection in a Rician Fading channel
Authors: Korn I. 
Published: July 2007

AbstractWe derive an expression for the error probability of M‐ary differential phase shift keying with differential phase detection and of M‐ary frequency shift keying with limiter discriminator integrator detection which is valid for Rician. Rayleigh and Gaussian channels.
Radiation analysis and errors associated with the monopulse operation of a satellite direction finder
Authors: Afifi Mostafa S. 
Published: July 2007

AbstractThis work describes the radiation performance of a novel concept for direction and location finding, using stationary satellite beacons. The received signals are processed with a monopulse four‐element array. The monopulse mode is generated using the phase excitation of the radiating elements. For accurate processing the radiation phase should correspond with the bearing angle around the boresight direction. Phase deviations, however, occur in this phase pattern owing to the discrete excitation of the elements. Therefore, detailed analyses are presented for this phase pattern, its attainable gain and the depolarization effects, in order to select the kind of array elements, and their spacings, which minimize the phase pattern deviations. The dipoles and the slots, as array elements, yield better phase performance, smaller size and simpler structures than horn radiators, at the expense of worse depolarization.
Advanced techniques for circuit multiplication: Celtic 3G
Authors: Aboaf P. , Bailly R. 
Published: July 2007

AbstractThe Celtic 3G is Alcatel CIT's new digital circuit multiplication system designed to enhance the cost‐effectiveness of long‐haul links by increasing their capacity by a factor of between 5 and 8. The Celtic 3G offers an effective, versatile solution to congestion problems on 2048 and 1544 kb/s digital transmission links.The paper describes the compression modes used by Celtic 3G family to transmit the various types of signals (speech, voice band data, 64 kb/s digital data), the applications and the operating principles of the equipment.A number of telecommunication administrations and agencies have adopted and will this year deploy the Celtic 3G because of its benefits, technical qualities and the savings which it will achieve on digital links.
The use of digital circuit multiplication equipment in satellite communications
Authors: Viklund Nils‐Erik , Nycander Claes 
Published: July 2007

AbstractThe use, within satellite communications, of low rate encoding (LRE) techniques, based on 24, 32 and 40 kb/s ADPCM coding, coupled with digital speech interpolation (DSI) to form a digital circuit multiplication equipment (DCME), is addressed in this paper. The need for a system simulation tool, in order to plan for and correctly use the DCME concept is identified. Results obtained with this simulation tool are presented. The simulation model makes it possible to predict the behaviour of the system from a quality point of view, with external conditions simulated to be very close to actual operating conditions.
Optimum processing of qpsk signals for site diversity
Authors: Sandström Henrik 
Published: July 2007

AbstractFor satellite communications systems which use frequencies above 10 GHz, rain and clouds attenuate signals severely, leading to an increase in bit error rate (BER) in digital links. This may be coped with by using two or more receivers on the ground, spaced far enough apart to avoid simultaneous rain outages. In this paper, a BER‐minimizing decision processor is derived for two receivers and QPSK modulation. In particular, it is applied to a linear attenuating transmission channel adding independent white Gaussian noise. It is found that gains of nearly 3 dB compared to a switched system are possible in down‐link limited cases.
Modelling direct sequence pseudonoise(dspn) satellite reception with directional antennas in the dense scatterer mobile environment
Authors: Amoroso Frank , Jones William W. 
Published: July 2007

AbstractA geometric propagation model is developed for simulating the reception of direct sequence pseudonoise (DSPN) satellite signals by a directional or omni antenna in the dense scatterer mobile environment. The model is first validated for narrowband signals by a direct comparison of both simulated cumulative signal strength statistics and simulated diffuse Doppler spectra with classical theory. The model is then used to predict fading statistics for DSPN signaling, either with omni or directional antennas. As expected, the mitigation of fading is closely related to the ratio of DSPN chip duration to delay spread of the scatterer medium for both the omni and directional antennas.
Comparison of the simulated performance of a vsat satellite link with measurements
Authors: Mwanakatwe M. , Willis M. J. , Evans B. G. 
Published: July 2007

AbstractThis paper combines a number of features. First the simulation of the transmission performance of a Ka‐band VSAT system (CODE) is presented. The results are used to verify the systems design that was performed for CODE and to demonstrate that the implementation margin due to intermodulation noise, adjacent channel interference, filter ISI, amplifier non‐linearities and phase noise was sufficient. In the design of VSAT systems of this type phase noise was thought to be particularly important, and a new and detailed simulation of its effects is presented in the paper. For the first time, experimental measurements of system degradations have been taken on a VSAT system which have been used to verify simulation results. This was particularly important for the new phase noise simulation results and good agreement was obtained. An overall loop‐back experiment using the Ka‐band VSAT terminal with the Olympus satellite shows good agreement with the simulation results. Finally, the availability of experimental results has enabled us to compare the accuracy of TOPSIM III and BOSS simulations for the VSAT system. The paper indicates some shortcomings in the TOPSIM III simulation of phase noise and highlights the generally good agreement obtained with experimental results by the BOSS simulations.
ISDN and the digital satellite revolution
Authors: Pelton Joseph N. 
Published: July 2007

AbstractThe greatly increased capacity and capabilities of terrestrial fibre networks, current and future satellites bring forth key issues relative to ISDN and other advanced communications concepts. This paper explores a brief history of the development and characteristics of both satellite and fibre, together with a description of advanced satellite concepts. Key advantages and disadvantages of satellites are described and related to future communications environments. These analyses are then discussed relative to their impact and implications on the design and operation of ISDN networks.
Unified approaches to integrated‐service networks–burst and fast packet switching
Authors: Maples Tracy Bradley , Suda Tatsuya 
Published: July 2007

AbstractThe increasing demand for communication services, coupled with recent technological advances in communication media and switching techniques, has resulted in a proliferation of new and expanded services. Currently, networks are needed which can transmit voice, data and video services in an application‐independent fashion. Unified approaches employ a single switching technique across the entire network bandwidth, thus allowing services to be switched in an application‐independent manner. This paper presents a taxonomy of integrated‐service networks, including a look at NISDN, while focusing on unified approaches to integrated‐service networks.The two most promising unified approaches are burst and fast packet switching. Burst switching is a circuit switching‐based approach which allocates channel bandwidth to a connection only during the transmission of ‘bursts’ of information. Fast packet switching is a packet switching‐based approach which can be characterized by very high transmission rates on network links and simple, hard‐wired protocols which match the rapid channel speed of the network. Both approaches are being proposed as possible implementations for integrated‐service networks. We survey these two approaches, and also examine the key performance issues found in fast packet switching. We then present the results of a simulation study of a fast packet switching network.
Video and image applications on narrowband and broadband isdn
Authors: Dewitt Russ , Ramasastry Jay , Kim Kap , Li Peter 
Published: July 2007

AbstractTwo major ISDN applications which will undoubtedly affect world‐wide telecommunications in the coming decade are discussed. They are: (1) video transmission and (2) image transmission.Brief reviews of videophone chronicle and the current video coding technologies are presented. The application of videophones using p × 64 (CCITT coding algorithm up to 1·5 Mb/s) and the DCT (discrete cosine transform) algorithm for narrowband ISDN are discussed. Broadcast TV quality DS3‐45 MB/s video codecs are also briefly discussed as a probable videophone system in the broadband ISDN era.The explosive growth of facsimile services is reviewed, and the progress of image coding technologies and their standards are covered. The prospects of high resolution image transfer systems with ISDN are addressed.
Optimal policies for integrating heterogeneous services on isdn channels
Authors: El dessouki O. , Baraka H. , El sayed S. 
Published: July 2007

AbstractA technique for the classification and evaluation of hierarchical access integration policies of ISDN channels is proposed. The essence of the basic control decisions based on several parameters of the servers and channel is captured in a single priority‐based‐layered model of multiple queues. We solve for the resulting delay of different policies and investigate the performance in one tractable limit of this model. Using our understanding of the problem parameters and their interaction, we propose a number of heuristic policies for the general model. The results of the general problem complexity investigations suggest the use of simulation models. Problem parameters considered are channel acceptable access delay value, number of servers needed, and flow duration time of a request. Preemptive and non‐pre‐emptive policies on queued traffic are considered. Performance considers average delay, delay variation and channel utilization. Simulation data on these policies suggest that policies that favour shorter services given better overall delay over a wide range of system parameters. Policies that favour longer and broadband services, on the other hand, show better quality and smaller delay variation.
Guidelines for a preliminary dimensioning of a transaction‐oriented vsat network
Authors: Zein Tarif , Maral Gérard , Jabbari Bijan 
Published: July 2007

AbstractVery small aperture terminal (VSAT) satellite networks have recently emerged as an attractive and cost‐effective alternative to traditional terrestrial circuit or packet switching networks for transaction enquiry‐response data applications. VSAT star networks are particularly well adapted to this kind of application, offering high link reliability, better flexibility, wide service area coverage and several economic and operational advantages. However, one major drawback associated with satellite links is the relatively high propagation delay, which is about 0·27 s for one hop (ground–satellite‐ground). This requires special design and dimensioning optimization in order to keep the response time of the network within acceptable limits.This paper provides guidelines for the dimensioning of such enquiry‐response star VSAT networks. Dimensioning refers to determining the minimum transmission bit rates required, on the different terrestrial and satellite segments of the network, for a given network configuration and mean delay requirement. The approach presented in this paper allows network designers to determine, in a simple way, the required modem speeds of the network segments.
New formulation and plots for error probability in the pulse position modulation (PPM) photon counting satellite‐to‐earth channel
Authors: Amoroso Frank , Bricker Jacob L. 
Published: July 2007

AbstractIn digital satellite‐to‐earth transmission the entry of substantial undesired solar radiation into the receiver antenna is sometimes unavoidable. When the signal transmission takes the form of incoherent optical pulse position modulation (PPM) the parameters of signal and consequent intense noise can fall outside the range of routinely available classical numerical results on symbol error probability.This paper presents an alternative system for parametrization of signal and noise in the classical PPM channel, i.e. that characterized by Poisson photon arrival statistics for signal itself, the noise itself, and the signal plus noise.The resulting formulation for error probability, the scheme for probability calculation, and the simple, compact plots of error probability versus newly conceived parameters cover the entire range of signal and noise intensities, from weakest to strongest.Of course, when properly interpreted the new results agree entirely with classically available numerical results within the parametric range of the former.
A review of Ka and Ku band propagation measurements on satellite paths made at the bt laboratories in the U.K.
Authors: Howell Robert , Thompson Paul 
Published: July 2007

AbstractMeasurements of slant‐path attenuation and crosspolar discrimination, obtained from four satellite measurement programmes carried out at the BT Laboratories, Martlesham Heath, England, are described. The measurements covered frequencies in the range 11.3 GHz to 30 GHz, path elevations ranging from 8.3° to 29.9°, and were made using both circularly and linearly polarized signals. Cumulative distributions, derived from the measured data, are extrapolated to frequencies of 12.5, 14.3, 19.8 and 29.7 GHz and then combined to give statistics for a database of more than 20 years.
Performance of A prioritized non‐blocking switch under hotspot traffic conditions with head of line resolution
Authors: Bohm Stephan , Elhakeem A. K. , Murthy K. M. S. 
Published: July 2007

AbstractIn this paper, we pursue a performance analysis under hotspot traffic conditions of a four‐level prioritized non‐blocking baseband switch for use on board a switching multibeam satellite. Both finite input and output buffering as well as speed‐up are employed to reduce the loss which is critical in a satellite application. In addition, in order to improve the performance of the two lowest priority users a head of line resolution (HLR) technique is implemented. It is shown that with HLR and the proper adjustment of the switch speed‐up and the input and output buffers the loss can be substantially reduced. It is also shown that the dependence on the switch size which is characteristic of the unbuffered discard case is substantially reduced, even in a prioritized environment, allowing larger switches to be implemented.
A future satellite communications system using millimetre‐wave bands and an on‐board processor
Authors: Endo Minoru , Kumagai Takeo , Yamamoto Tetsuo , Otsu Yuichi , Kikuchi Takaaki , Komiyama Norio 
Published: July 2007

AbstractThis paper proposes the system concept of a personal satellite communications system that will be available in the first decade of the 21st century. Technologies of millimetre‐wave bands and an onboard processor with baseband switching promise to meet the requirements of a personal communications system: portability, low‐cost, and large capacity. Based on the prospects of these technologies, the most likely parameters for the future personal satellite communications system and the configuration of a suitable on‐board processor are proposed. A trial model of such an on‐board processor has been made. In this paper, details of the trial model on‐board processor and its future developments are described.