Satellite Communication

The use of rock bolts in the mining industry is a widely used approach for increasing mine stability. Here we demonstrate an IoT rockbolt with strain and accelerometer sensors. By utilizing the real-time monitoring capabilities of a network of IoT rockbolts, open up for drastically improve monitoring of mining activities and thereby providing real time logistics and operational information while at the same time provide working safety information.

Signal-to-noise ratio (SNR) estimation for linearly modulated signals is addressed in this letter, focusing on envelopebased estimators, which are robust to carrier offsets and phase jitter, and on the challenging case of nonconstant modulus constellations. For comparison purposes, the true Cramér-Rao lower bound is numerically evaluated, obtaining an analytical expression in closed form for the asymptotic case of high SNR values, which quantifies the performance loss with respect to coherent estimation. As the maximum-likelihood algorithm is too complex for practical implementation, an expectationmaximization (EM) approach is proposed, achieving a good tradeoff between complexity and performance for mediumto-high SNRs. Finally, a hybrid scheme based on EM and moments-based estimates is suggested, which performs close to the theoretical limit over a wide SNR range.

This paper discusses the design of Low Cross Polarized feed for offset parabolic reflector antenna and its application. Conical corrugated horn antenna consists an input mode TE11 and the corrugation part requires a transition to HE11 mode for propagation. The paper presents the widely used design of mode converter-Variable depth slot mode used for TE11-HE11 conversion. Three different design of Corrugated horn antenna is presented for optimizing the value of Cross Polarization. The choice of the delta is the most important parameter for optimizing the value of cross polarization. The value of f/D is chosen 0.4 for offset parabolic reflector antenna. This design also provides high gain, good beam symmetry, and high bandwidth performance.

A realistic analysis of media access control protocols for wireless applications must incorporate the affects of physical layer phenomena such as Rayleigh fading, shadowing and other processes that cause signal attenuation. In this work we present an innovative technique where the effects of the physical layer are embedded in the link layer by creating a fictitious user that blocks channel access from other users similar to the way fading inhibits real users from channel access. We match the fading process with the user's status, by minimizing the cross entropy prior to analyzing message delay. Simulations are used to assess the accuracy of the approach.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at anytime. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." Abstract This document describes the messagesand procedures of the Negative-acknowledgement (NACK) Oriented Reliable Multicast (NORM) protocol. This protocol is designed to provide end-to-end reliable transport of bulk data objects or streams over generic IP multicast routing and forwarding services. NORM uses a selective,negative acknowledgement mechanism for transport reliability and offersadditional protocol mechanisms to allow for operation with minimal "a priori" coordination among sendersand receivers. A c...

Two prototype antenna pointing units (APUs) for controlling different antennas tracking geostationary satellites have been built using an 8080 microprocessor. The use of the microprocessor has allowed the same basic hardware to control two separate and different parabolic dish antennas with minimal circuitry changes and has provided significant flexibility in the performance of the units. This paper describes the APU design, which optimizes hardware and software to provide the flexibility necessary during initial testing and subsequent operation of the prototypes.

Ineffective systems engineering practices continue to jeopardize aerospace missions, resulting in multi-billion-dollar losses, delays, and fragmented development outcomes. As complexity intensifies and timelines shrink, conventional document-based methods increasingly fail to support early validation, cross-domain traceability, and synchronized tool usage. This research presents an integrated approach that addresses three critical gaps: synchronizing executable and traceable MBSE models across structural, behavioral, and requirements domains; applying scalable requirements prioritization techniques tailored for Complex Adaptive Systems; and establishing automated simulation feedback loops through digital toolchain integration. Central to this strategy is the Digital Trinity, which connects system models, simulations, and lifecycle data through a continuous digital thread. The proposed methodology begins with SysML-based modeling in Cameo Systems Modeler, followed by a multi-phase prioritization process using filtration, metadata scoring, and comparative weighting to evaluate over one hundred mission requirements. The approach is applied to the SidSat mission, a 4U CubeSat featuring a modular architecture with core avionics, a robotic arm payload, and an onboard AI/ML experimentation module. Requirements were allocated to model components, then verified using parameterized simulations. MATLAB was employed for mass, power, and thermal margin calculations; STK for orbital behavior assessment; Excel for value propagation and I/O management; and Teamcenter with AWS for model control and data traceability. Simulation outputs were dynamically linked to SysML constraint blocks and displayed through interactive dashboards in Cameo, ensuring transparency of compliance and coherence of the architecture state. Results demonstrate enhanced early-stage validation, improved stakeholder alignment, and reduced risk of misalignment between model logic and simulated performance. The final system model operates as a live digital reference across design and analysis phases, enabling iterative updates and real-time feedback. Although demonstrated on a CubeSat platform, the framework is extensible to larger systems where agility, traceable decision-making, and model-simulation convergence are essential for mission assurance.

A number of serious consortiums develop satellite communication networks. The objective of these communication projects is to service personal communication users almost everywhere on earth. The intersatellite links in those projects use microwave radiation as the carrier. Free-space optical communication between satellites networked together can make possible high-speed communication between different places on earth. Some advantages of an optical communication system over a microwave communication system in free space are 1) smaller size and weight, 2) less transmitter power, 3) larger bandwidth, and 4) higher immunity to interference. The pointing from one satellite to another is a complicated problem due to the large distance between the satellite, the narrow beam divergence angle, and vibration of the pointing system. Such vibration of the transmitted beam in the receiver plane decreases the average received signal, which increases the bit error rate. In this paper, we review 1) the present status of satellite networks, 2) developing efforts of optical satellite communication around the world, 3) performance results of vibration effects on different kinds of optical communication satellite networks, and 4) seven approaches to overcome the problems caused by transmitter pointing vibration.

We derive a model that optimizes the performance of a laser satellite communication link with an optical preamplifier in the presence of random jitter in the transmitter-receiver line of sight. The system utilizes a transceiver containing a single telescope with a circulator. The telescope is used for both transmitting and receiving and thus reduces communication terminal dimensions and weight. The optimization model was derived under the assumption that the dominant noise source was amplifier spontaneous-emission noise. It is shown that, given the required bit-error rate (BER) and the rms random pointing jitter, an optimal transceiver gain exists that minimizes transmitted power. We investigate the effect of the amplifier spontaneousemission noise on the optimal transmitted power and gain by performing an optimization procedure for various combinations of amplifier gain and noise figure. We demonstrate that the amplifier noise figure determines the optimal transmitted power needed to achieve the desired BER but does not affect the optimal transceiver telescope gain. Our numerical example shows that for a BER of 10 Ϫ9 , doubling the amplifier noise figure results in an 80% increase in minimal transmitted power for a rms pointing jitter of 0.44 rad.

In this paper, we analyze the effects of vibrations and the atmosphere on the performance of a broadband laser inter-satellite link (BLISL) which was studied within the framework of the BLISL joint Israeli-German applied research project. The use of optical radiation as a carrier between satellites and in satellite-to-ground links enables transmission using very narrow beam divergence angles. Due to the narrow beam divergence angle and the large distance between the satellite and the ground station or airplane the pointing is a complicated process. Further complication results from vibration of the pointing system caused by two fundamental mechanisms of a stochastic nature: 1) tracking noise created by the electro-optic tracker and 2) vibrations caused by internal satellite mechanical mechanisms. Additionally an inhomogeneity in the temperature and pressure of the atmosphere leads to variations of the refractive index along the transmission path. These variations of refractive index as well as pointing vibrations can cause fluctuations in the intensity and the phase of the received signal leading to an increase in link error probability. In this paper, we develop a bit error probability (BEP) model that takes into account both pointing vibrations and turbulence-induced log amplitude fluctuations (i.e., signal intensity fading) in a regime in which the receiver aperture D o is smaller than the turbulence coherence diameter d o . Our results indicate that BLISL can achieve a BEP of 10 -9 and data rate of 1Gbps with normalized pointing vibration of G T *σ 2 θ =0.05 and turbulence with σ X =0.3.

Free-space optical communication between satellites networked together can enable a high data rate between the satellites. Coherence multiplexing (CM) is an attractive technique for satellite networking due to its ability to cope with the asynchronous nature of communication traffic and the dynamic changes taking place in the satellite constellation. The use of optical radiation for intersatellite links creates very narrow beam divergence angles. Due to the narrow beam divergence angle, the vibration of the pointing system, the movement of the satellite, and the large distance between them the pointing from one satellite to another is a complicated task. The vibration of the pointing system is caused by two stochastic fundamental mechanisms: 1) tracking noises created by the electrooptic tracker and 2) vibrations created by internal satellite mechanical mechanisms and external environments. We derive mathematical models of signal, noise, the approximate signal-to-noise ratio, and the approximate bit-error rates of optical communication satellite networks as functions of the system's parameters, the number of satellites, and the vibration amplitude for frequency-shift keying coherence multiplexing (FSK-CM). Based on these models, we can calculate the negative impact of both the number of satellites and the optical terminal vibration on the system's performance.

To establish optical communication between any two satellites, the lines of sight of their optics must be aligned for the duration of the communication. The satellite pointing and tracking systems perform the alignment. The satellite pointing systems vibrate because of tracking noise and mechanical impacts ͑such as thruster operation, the antenna pointing mechanism, the solar array driver, navigation noise, tracking noise͒. These vibrations increase the bit error rate ͑BER͒ of the communication system. An expression is derived for adaptive transmitter power that compensates for vibration effects in heterodyne laser satellite links. This compensation makes it possible to keep the link BER performance constant for changes in vibration amplitudes. The motivation for constant BER is derived from the requirement for future satellite communication networks with high quality of service. A practical situation of a two-low-Earth-orbit satellite communication link is given. From the results of the example it is seen that the required power for a given BER increases almost exponentially for linear increase in vibration amplitude.

In this paper, a novel optimization methodology is investigated to optimize the resource allocation in a satellite system where variations of fading conditions are added to those of traffic load. A neural approximation technique is studied to exploit on line optimal reallocation laws, as functions of the state of the network. No closed-form expressions for the system dynamic equations and the functional cost are needed. Simulation results show how the proposed technique outperms two other optimization strategies, based on a certainty equivalent assumption and on the application of Perturbation Analysis, respectively.

The paper compares two alternative hierarchical bandwidth allocation and admission control schemes suited for the multiservice Ka-band satellite environment, where the attenuation of the transmitted signals due to bad weather conditions has a heavy impact on the system's performance. The two schemes are compared by using data derived from a real case study. The aim is to demonstrate that a high level control mechanism for the assignment of the satellite bandwidth to earth stations, which takes into consideration the rain attenuation probabilities of a certain geographical area, improves the system's performance, with respect to an assignment mechanism insensitive to the geographical fade probabilities.

Solar power has the ability to play a main role in the electrification of the developing world. Autonomous energy systems based on solar photovoltaic is, for some cases, a feasible alternative to a grid connection. Solar power can also be used as a complement to a weak grid, for facilities that requires a higher reliability of power. The main objectives of this thesis were to know the economic effect of connecting solar power system to grid station, based on existing but nonoperational solar panels, and to present a cost-effective autonomous energy system, with a good reliability The performance of solar power plant is evaluated based on a developed model comprise photovoltaic array, battery storage, controller and converters. The model is implemented using MATLAB/SIMULINK software package. Perturb and observe (P&O) algorithm is used for maximizing the generated power based on maximum power point tracker (MPPT) implementation. The outcome of the developed model are validated and sup...

During the first two decades of the 21st century, the interest in the Moon missions' realization has been updated from the side of states and commercial operators. Many governmental, commercial and academic Moon's missions are under development now. The development of the information system for researching the Moon's surface and supporting the Lunar human and unmanned missions is actual. The Conceptual approach in the development of the Selena-Information System is presented. The Selena-Information system is intended to provide the Earth's and Moon's consumers with multi-layer information about the Moon's surface and distribution of the soils including minerals and water. The Selena-Information System combines three parts: the Moon segment, the Earth segment, and the Telecommunication segment. The raw Moon remote sensing information could be obtained by the constellation of small satellites for remote sensing of the Moon in the low Moon Orbit. Taking into account the low power capacity of the small satellite the huge information volume can be transmitted in a short distance. It is proposed to put the two Lunar Landing Modules in the Moon's polar regions. These Modules provide control of the small satellite in the Low Moon Orbit, receiving raw data, processing, and storage of it. The Earth segment includes the system control mission center, Data Centers of the Selena-Information System Information consumers, control mission centers of consumer's systems. The telecommunication segment provides the connection between the Moon and Earth segments and uses Big Antennas and ground communication systems.

Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) program plays a key part in helping NASA maintain this important role. The NASA STI Program operates under the auspices of the Agency Chief Information Officer. It collects, organizes, provides for archiving, and disseminates NASA's STI. The NASA STI program provides access to the NASA Aeronautics and Space Database and its public interface, the NASA Technical Reports Server, thus providing one of the largest collections of aeronautical and space science STI in the world. Results are published in both non-NASA channels and by NASA in the NASA STI Report Series, which includes the following report types: TECHNICAL PUBLICATION. Reports of completed research or a major significant phase of research that present the results of NASA programs and include extensive data or theoretical analysis. Includes compilations of significant scientific and technical data and information deemed to be of continuing reference value. NASA counterpart of peer-reviewed formal professional papers but has less stringent limitations on manuscript length and extent of graphic presentations.

The future development of broadband satellite systems providing services based on the Internet Protocol (IP) needs to be stimulated by means of common standards. This paper presents the ETSI BSM PEP terminal architecture and PEP usage scenarios. In addition this paper shows the benefits of cross-layer improvements, where the TCP traffic sent by STs through an NCC/Gateway that acts as a PEP-spoofer on ACKs going in the opposite direction.

This paper deals with a NP-Hard resource allocation problem for a satellite network. An approach based on the estimation of the gradient of a cost function, obtained through a "relaxed continuous extension" of the discrete constraint set, is proposed. Since neither closed forms of the performance measure, nor additional feedbacks on the statistical properties of the traffic sources are requested, the proposed approach reveals to be suitable for optimizing the resource allocation in real life case studies, where the application of specific certainty equivalent assumptions is impractical.

Full dimension MIMO (FD-MIMO) is one of the key technologies presently studied in the 3GPP for the next generation long-term evolution advanced (LTE-A) systems. By incorporating FD-MIMO into LTE/LTE-A systems, it is expected that system throughput will be drastically improved beyond what is possible in conventional LTE systems. This paper presets details on the 2D active antenna array design for FD-MIMO systems supporting 32 antenna elements. The FD-MIMO system allows for dynamic and adaptive precoding to be performed jointly across all antennas thus achieving more directional transmissions in the azimuth and elevation domains simultaneously, to a larger number of users. Finally, we discuss 2D antenna array port virtualization techniques for creating beams with wide coverage, necessary for broadcasting signals to all users within a sector, such as the CRS (Common Reference Signal).

In this paper, we consider an adaptive single dwell serial search system of pseudo-noise (PN) sequence s for direct sequences spread-spectrum (DS-SS) systems in no fading additive white Gaussian noise channels. Since the received signal levels in mobile communications are unknown and location varying, the acquisition schemes for pseudo-n oise (PN) sequences with fixed thresholds may cause too many false alarms. Therefore, adaptively varying thresh old schemes are proposed through the use of a constant false alarm rate (CFAR) algorithm. From the simulation results, w e observe that the DS/CDMA systems with CFAR processor outperforms the conventional scheme with fixed threshold.

This paper has two major parts. In the first part, a brief review of satellite communication is shown by mentioning types of orbit, frequency bands and a block diagram of satellite communication. Here, the block diagram reflects a general view of uplink, transponder and downlink section of a communication satellite. Description of each section has been given by explaining the function of every unit. The second part focuses solely on ‘Bangabandhu Satellite-1’, the first GEO satellite of Bangladesh, analyzing its costs, specifications and ground control stations. The footprint of the satellite including its primary and secondary coverage areas is shown in a figure. Finally, the impacts and applications of the satellite are given.

A study of the effects of human proximity on the polarization purity of two types of circularly-polarized handset antennas for personal satellite communications was investigated using the hybrid method of moments (MoM)/finite-difference time-domain technique. Associated with this, assessments of specific absorption rate in the head were made. The method gave stable results, in accordance with physical expectations; good agreement with the pureMethod of Moments was shown in simplified cases omitting the head. The quadrifilar spiral antenna (QSA) was shown to be a propitious design for personal satellite communications.

This paper reports on a preliminary study using EutelSat Hotbird 13A beacon data at 19.7 GHz and 29.5 GHz (scaled data) to evaluate the benefit of using Time Diversity (TD) and Maximal Ratio Combining (MRC) on an experimental next generation satellite link in the UK. The authors have used the 2nd generation of video broadcasting via satellite (DVB-S2) as the broadcasting standard to investigate the novel integration of TD and MRC. The benefit of the TD and MRC scheme was quantified in terms of percentage enhancement of the link availability. Long-term statistics of rain and atmospheric attenuation were derived from a period of three year's measurements made in Pontypridd, South Wales and in Chilbolton, England, at 19.7 GHz. A hypothetical Ka-band satellite broadcast link between Pontypridd and Chilbolton has been designed to use 29.5 GHz as the uplink frequency while 19.7 GHz is used as the downlink frequency. The paper discusses the performance enhancement provided by TD and MRC during different types of fading events. The integration of TD and MRC into the DVB-S2 standard provides the capability to continue delivering services at lower carrier-to-noise (C/N) levels by lowering the bit error rate (BER).

In this paper, we propose an Automatic Repeat reQuest (ARQ) technique for enhancing the reliability and throughput of broadband wireless Internet access applications, and provide examples of its performance. ARQ is a method for making a link and flow more robust to errors. Other than enhancing link quality, ARQ provides early error recovery, so that the transport layer does not lower the data throughput. The cost of these enhancements is additional overhead. In this work, we have extensively analyzed our proposed ARQ scheme along with realistic wireless channel and protocol stack models. We have quantified the performance gains of our ARQ scheme as reduced end-to-end delay, increased throughput, SNR gain and fade margin, also providing the overhead costs. We have proposed and analyzed enhanced features, namely, Segmentation and Reassembly (SAR) and Bitmap Compression. We showed that these features reduce the overhead, the extent of which depends on the nature of the errors.

The link margin for satellite communication services targeting mobile users is tight. This leads to reception problems in areas with strong fading scenarios like urban areas or forested areas with dense foliage. In order to avoid loss of service in urban areas with week coverage by satellite signals, terrestrial repeaters are used. Therefore in the design of antennas for mobile reception of satellite services, an optimized characteristics for the satellite constellation, as well as an adequate coverage of the terrestrial repeaters has to be accounted for. In this paper an antenna with optimum shaped pattern for the satellite mode and adjustable gain for vertical polarization is investigated. Beside constraints regarding the radiation pattern, measurements concerning the dependence of the antenna on noise temperature and therefore the behavior in real noisy environments are carried out. A comparison with a conventional antenna shows the high performance of the new antenna in combination with a very low volume requirement.

The RF behavior of YBa2Cu3O7-x is being evaluated for its potential as a material used to make microwave cavities for particle accelerators. Single crystals and thin films are under study at 1.5 and 6 GHz. The best results have been obtained using the crystals of Schneemeyer, et al., which show a residual resistance below 5×10-4 Ω at 6 GHz at 77K. This is substantially below the resistance of 77K copper. The resistance of these crystals at the superconducting transition drops more than two orders of magnitude within a few degrees of Tc. The sharpness of this drop is comparable to that of niobium. It is believed that these crystals are still far from ideal and that their properties deteriorate with time, but they are of much higher quality than the other forms of YBCO studied. Progress is being made by our collaborators towards producing thin films with useful RF properties. Compared with films of a year ago the sharpness of the superconducting transition has increased substantially although the residual losses are still high. Our measurement techniques are now sensitive to as little as 20 mm 2 of material with a resistance of 20μΩ.

This paper presents an insight into network performance evaluation and quality of service (QoS) improvement of GSM cellular system services during rainfall. The components of QoS and mechanisms of analyzing and evaluating them are discussed. The paper also identifies the important key performance indicators (KPIs) for QoS evaluation which are used in evaluating the poor GSM network during rainfall. Five assessment parameters (i.e. network accessibility, service reliability, connection quality, and radio propagation and rain attenuation) for evaluating QoS on the network were employed. Prior to the development of this research, result shows that QoS of GSM system in the country is unreliable. It is also found that GSM network accessibility and reliability in the country are unsatisfactory during rainfall. The paper is concluded with recommendations which include the GSM link budget that incorporated the rain attenuation factor that would definitely improve the QoS of poor GSM network services in order to enhance effective and efficient telecommunication system in the country.

Youth for GNSS (YGNSS) is a team created by the Space Generation Advisory Council on GNSS and the International Committee on GNSS (ICG). Composed of students and young professionals, Youth for GNSS aims to recognize and promote the ways in which Global Navigation Satellite Systems (GNSS) and Satellite Based Augmentation Systems (SBAS) can benefit society. With the future and health of our planet and its citizens a primary concern, YGNSS aims to secure and optimize how GNSS -based applications and technology will benefit society by promoting compatibility and interoperability of GNSS through a network of systems. In addition to the development and improvement of technology, applications, education, and outreach in regions where GNSS is already established, it is the goal of YGNSS to analyze and promote the importance and impact of GNSS technology in areas with less developed infrastructure, such as in developing countries and in the Arctic. In this paper, drivers of change in the Arctic are discussed based on the impact of GNSS as tools for scientific applications and for strengthening and promoting interoperability of navigation, positioning, and timing systems. Topics such as surveying, mapping, engineering and construction, aviation, maritime and space weather monitoring are discussed. Due to the high ecological sensitivity and extreme weather conditions in Arctic regions, accidents there could cause great environmental damage and also threaten human lives. Navigation integrity is therefore of particular importance in this region.

The rapid growth in wireless technologies has intensified the demand for the radio spectrum. On the other hand, the research studies reveal that the spectrum utilization is unevenly distributed, which leads to the conclusion that there is a problem with the spectrum management and allocation rather than the scarcity of the spectrum itself. This inefficiency in spectrum usage in addition to the escalating demand for the radio spectrum fostered the research studies that focus on new communication paradigms referred to as Dynamic Spectrum Access (DSA) and cognitive radio networks, which are based on opportunistically utilizing the radio spectrum. IEEE 802.22 is the first standard for cognitive radio networks, in which, however, network entry and initialization, as well as the hidden incumbent problem have not yet completely been addressed. On the other hand, mobility is also an unexplored issue in cognitive radio networks. In this paper, we propose a novel protocol that combats the hidden incumbent problem during network entry, initialization and handover, while at the same time taking the mobility pattern of the cognitive devices into consideration. Our proposed scheme is based on a satellite assisted cognitive radio architecture. Our model outperforms the current IEEE 802.22 scheme and other work in the literature in terms of connection setup delay 1 .

American military satellite GPS system is an element of the global GNSS. It emits two codes: the precise and civil one. As late as in 2000, intentional interference that decreased precision of localization was introduced, allowing navigation accuracy of 20 m. GPS was made available to civil users, however, at their own responsibility. So, if we use GPS for our own goals, we must consider the errors that occur and their consequences. Nonetheless, commercial and operational needs determine the necessity of permanent access to satellite signal with appropriate consistency, accessibility, reliability and precision. Hence, natural and intentional errors are compensated for, using appropriate methods, based on a given activity.

A new optically controlled reconfigurable antenna for cognitive radio is presented. The antenna can operate at an ultra-wideband and three narrow bands by controlling four photoconductive switches. The bandwidth of the ultra-wideband is 2.65 to 10.3 GHz. The bandwidths of three narrow bands are 7.10 to 8.01 GHZ, 3.55 to 5.18 GHz, and 5.12 to 6.59 GHz, respectively.

A new optically controlled reconfigurable antenna for cognitive radio is presented. The antenna can operate at an ultra-wideband and three narrow bands by controlling four photoconductive switches. The bandwidth of the ultra-wideband is 2.65 to 10.3 GHz. The bandwidths of three narrow bands are 7.10 to 8.01 GHZ, 3.55 to 5.18 GHz, and 5.12 to 6.59 GHz, respectively.

Using the JCSAT-1B satellite and several VSATs installed at three different locations approximately 100 km far away from each other, experimentally rainfall effects on Ku-band satellite channels have been studied. Worst month and yearly distribution of Ku-band rain attenuation and their relation at those locations are discussed.

In satellites, nonlinear amplifiers used near saturation severely distort the transmitted signal and cause difficulties in its reception. Nevertheless, the nonlinearities introduced by memoryless bandpass amplifiers preserve the symmetries of the M-ary quadrature amplitude modulation (M-QAM) constellation. In this paper, a cluster-based sequence equalizer (CBSE) that takes advantage of these symmetries is presented. The proposed equalizer exhibits enhanced performance compared to other techniques, including the conventional linear transversal equalizer, Volterra equalizers, and RBF network equalizers. Moreover, this gain in performance is obtained at a substantially lower computational cost.

Navigation in harsh environments mostly encounters many problems such as signal blocking due to a variety of obstacles around the receiver. Vectorised receiver has an architecture in which the channels can share the information. As a result, the strong channels aid the blocked one to reacquire the signal immediately after returning. However, if the output of a channel is undesirable, it may disrupt the operation of the system especially for the weak blocked channels. In this paper, an intelligent vectorised architecture is proposed to solve this problem. Three popular architectures including federated, adaptive, and vectorised are combined and then evidence theory is utilised to select the result with higher certainty. The experimental results in urban canyons show the improvements in signal availability and thermal noise performance.

The prediction of rain fade slope on satellite link is currently an essential parameter used by system designers for the development of communication power control and error-correction schemes, which mini-mize effects of the link outages for their systems. It is also useful for the implementation of computer generated received signal for primary experiments. Due to its time variation and dependence on the rain type and characteristics, it will be useful to develop an efficient model that fits the fade slope evaluated from the link. Fade slope indicates the rate of change of rain attenuation. The knowledge of fade slope of attenuation caused by rain or other meteorological events are very important for fade mitigation techniques. Knowledge of this parameter is important for determining the required tracking speed of fade mitigation techniques. The fade slope depends on attenuation level, on sampling time and on climatic parameters (drop size distribution and therefore on the type of rain).

When using γ-ray coded-mask cameras, one does not get a direct image as in classical optical cameras but the correlation of the mask response with the source. Therefore the data must be mathematically treated in order to reconstruct the original sky sources. Generally this reconstruction is based on linear methods, such as correlating the detector plane with a reconstruction array, or non-linear ones such as iterative or maximization methods (i.e. the EM algorithm). The latter have a better performance but they increase the computational complexity by taking a lot of time to reconstruct an image. Here we present a method for speeding up such kind of algorithms by making use of a neural network with a back-propagation learning rule.

The policy based management is a technique to coordinate the configuration of several equipments in a network based on Service Level Agreements(SLAs). These abstract policies are difficult to be interpreted and implemented by network equipments, that requires absolute values, and fuzzy logic has been showed to be efficient to represent abstract values. A fuzzy controller should implement a dynamic provisioning mechanism used to reconfigure all nodes according ingress traffic. This work proposes a methodology to map policies in fuzzy parameters to achieve the desired QoS in a DiffServ domain. The functionality are demonstrated by simulation of an IP Telephony application crossing a DiffServ domain.

The large development of multimedia clinical applications and the use of inter and intra-hospital communication networks imply particular analysis for each one. The study and evaluation of new health services based on telemedicine requires a technical methodology. In this paper we propose a complete methodology implemented by an automated process that includes the system and network modelling and a test prototype for real and simulated measurements. The proposed method can be used to adjust traffic parameters (e.g. transferred clinical file sizes or signal transmission rates), to guarantee desirable Quality of Service (QoS) requirements, under different network resources.

Near future satellite and terrestrial telecommunication (TLC) systems are expected to benefit from the use of operational frequencies spanning the Ka, Q, V and W bands, the main advantages being the availability of larger bandwidths and the smaller antenna size for a given gain. Moreover, the possibility of using on-board antennas with enhanced directivity is attractive for satellite systems whose coverage area is subdivided into spot beams for frequency reallocation or regional services. For example, the W band is attractive for fixed satellite services (FSS), especially for geostationary high-throughput systems (HTSs), in which the use of such frequencies for the feeder link (i.e. large available bandwidth) could reduce significantly the number of gateways with respect to Ka and Q/V bands. As for deep space missions, the main driver for the interest in using frequencies in the Ka to W bands is the possible increase in the on-board antenna gain with respect to the values at X band considered for current or planned missions. The drawback of using electromagnetic waves at frequencies in Ka, Q, V and W bands is the definite impact of the impairments caused by the troposphere. As a consequence, the design of TLC systems at such frequencies, and in particular satellite-based ones, cannot rely on the classical approach of simply assigning an extra power margin to counteract atmospheric fades. The extensive use of fade mitigation techniques (FMTs), such as link power control (LPC), site diversity or on-board adaptive power allocation, from the propagation side, adaptive coding and modulation (ACM) and data rate adaptation (DRA), from the telecommunication side, is mandatory. A reduction of the quality of service (QoS) should also be considered. This chapter deals with all these aspects characterizing the propagation of electromagnetic waves in the Ka, Q, V and W bands, spanning from the main impairments induced by the troposphere (and how they change as the frequency increases), to how extreme atmospheric conditions can be handled making use of suitable FMTs.

Actual Ka-band SATCOM systems provide wide-band access to users located in areas unserved or underserved by the terrestrial infrastructure. The rapid development of terrestrial systems is pushing SATCOM companies to assess the exploitation of higher frequency bands (Q/V and maybe W) where larger bandwidths are available. This contribution proposes a possible configuration of a SATCOM system with European coverage featuring feeder link operation in the V-band. A time-series synthesizer has been used to model the propagation impairments produced by rain, whereas clear-sky attenuation is calculated by standard ITU-R formulas. A space diversity configuration of 18+2 gateways (including a clustered version made of two 9+1 sub-systems) would provide capacity values five times higher than actual Ka-band satellites, requiring an additional power margin against rain fades around 9-12 dB.