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Summary: This paper presents initial results available from the European Commission Horizon 2020 5G Public Private Partnership Phase 2 project "SaT5G" (Satellite and Terrestrial Network for 5G). After describing the concept, objectives, challenges, and research pillars addressed by the SaT5G project, this paper elaborates on the selected use cases and scenarios for satellite communications positioning in the 5G usage scenario of enhanced mobile broadband. This paper presents initial results available from the SaT5G project. It describes the concept, objectives, challenges, and research pillars addressed by the SaT5G project. It also defines how satellite can be seamlessly integrated into the eMBB usage scenario for 5G, by elaborating on the SaT5G use cases and scenarios for satellite positioning in eMBB. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on millimeter-wave-based mobile hotspot network (MHN) system for high-speed train (HST) communications, including system design, field trial, channel modeling based on measurement campaign, simulation, and validation. First, an overview of the MHN system and the design of an MHN enhanced (MHN-E) system including physical layer specification and single frequency network are provided. Second, the overall design of prototypes for MHN conventional (MHN-C) and MHN-E systems is presented, and then the recent experimental results of a field trial conducted at Seoul subway line 8 with the MHN-C prototype and demonstrations with the MHN-E prototype are analyzed. Third, this paper presents a measurement campaign investigating channel characteristics of a rural HST environment and a QuaDRiGa-based channel model developed based on the parameters extracted from the measurement. Finally, a computer simulation is conducted to validate the performance of the MHN-E system at high mobility of up to 500 km/h under the QuaDRiGa channel model, which suggests a good methodology for the validation of HST communication systems at the highmobility since it is impractical to be tested by real testbeds as of now. The simulation results revealed that the MHN-E system is capable of providing a broadband mobile wireless backhaul with a peak data rate exceeding 5 Gb/s at a speed of 500 km/h. [ABSTRACT FROM AUTHOR]

This paper describes the novel design concept of a wideband noncircular choke flange for connecting two contactless waveguide joints with the variable air gap. Resonant enhancement of transmission loss is observed in the experiment as well as the numerical simulation in Ansys HFSS software when a 2-D standing wave is excited in the narrow air gap. The shape of the choke groove is designed in such a way that ensures standing waves cannot be excited in the frequency band of interest, even considering possible linear and rotational misalignments between the connecting joints during practical operation, thereby making the design very robust. The eigenmode analysis is performed to decompose the mixed excitation mode into the fundamental and higher order modes, and for the case of misalignment, revealing why the electric field changes the direction of rotation above and below the resonant frequency. Experimental measurement results of the fabricated egg-choke flange showed that the transmission loss is less than 0.1 dB in the 2.5-GHz bandwidth from 8.5 to 11 GHz with possible misalignment which validates the design. Other choke shapes are possible following the same design methodology with different scaling parameters depending on the desired frequency band of the user application. [ABSTRACT FROM AUTHOR]

The capacity of the radio link can be improved a lot by using modern wireless technologies like Multiple Input and Multiple Output (MIMO) technology. Successful and efficient implementation of MIMO is possible only when there is a lot of feedback from the mobile station to the base station from time to time. This continuous feedback consumes a lot of uplink bandwidth. Bandwidth is very expensive in the current scenario. Hence, MIMO became expensive setup and viewed as a major obstacle in the deployment. As of our knowledge, this paper is the first to propose a novel scheme for efficient allocation of periodic feedback channel to the wireless network. In this paper, we defined various practical problems in the optimization of network and provided a solution by efficient algorithms. We defined two problems in the allocation process and given a solution with the help of an optimal polynomial-time algorithm. We also proposed a scheme when the base station should adopt the best algorithm among different algorithms. We also proposed combined scheme when Base station limit the resources and unable to execute the defined algorithms. The performances of the algorithms were shown through simulation results. [ABSTRACT FROM AUTHOR]

The unused millimeter-wave (mmWave) spectrum offers a superb opportunity to increase mobile broadband capacity due to the enormous amount of available bandwidth. Different candidate operating frequencies for 5G wireless networks are available at the mmWave band. For 5G wireless networks, the emergency case is one of the applications. This paper presents the outcome of indoor emergency stairwell measurement campaigns for 5G system at 26 GHz, 28 GHz, 32 GHz, and 38 GHz, which were conducted at the University Technology Malaysia, Kuala Lumpur, Malaysia. To effectively evaluate the performance of 5G wireless systems in these different bands, single- and multifrequency path loss models are proposed for this environment. This paper proposes a new path loss model based on a new physical anchor point referred to as physical-anchor stair (PAS) path loss model. In a single-frequency large-scale case study, the PAS and the floating intercept (FI) path loss model are investigated at the 20 GHz and 30 GHz bands. Moreover, this study is extended to cover the multifrequency path such as the alpha, beta, and gamma model and the close-in free space path loss model with frequency weight (CIF) model. The CIF model is developed in this paper. The proposed PAS model shows high accuracy (physically based model) and less complexity compared with the studied models. Results show that the path loss exponent values vary between 6.6 and 7.9 for all measured frequencies using the proposed PAS model and between 9.1 and 10.9 using the FI model. [ABSTRACT FROM AUTHOR]

Four novel architectures of wideband five-port single-ended-to-balanced power dividers with broadband common-mode suppression are proposed in this paper. The bandpass filtering capability with/without close-to-passband transmission zeros are also incorporated in some of them to obtain multifunctional single-ended-to-differential-mode filtering/power division operation. Two ideal 180° phase inverters are used to replace the conventional half-wavelength transmission line-based inverters in the basic power divider structure so that wideband common-mode rejection and a smaller circuit size are achieved. Quarter-wavelength transmission lines and coupled-line sections are exploited to simultaneously realize the bandpass filtering and wideband power division functionalities. Each five-port power divider exhibits broadband 3-dB single-ended-to-balanced power division, high in-band input–output power-matching levels, high in-band power isolation levels between the two balanced outputs and wideband common-mode rejection. The theoretical analysis, parametric study, and design procedure for the conceived single-ended-to-differential-mode power dividers are provided. Furthermore, for experimental and demonstration purposes, four microstrip prototypes designed at 1 GHz are manufactured and characterized. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to describe the current status of open rotor noise prediction methods and to highlight future challenges in this area. A number of analytic and numerical methods are described which can be used for predicting 'isolated' and 'installed' open rotor tonal noise. Broadband noise prediction methods are also described and it is noted that further development and validation of the current models is required. The paper concludes with a discussion of the analytical methods which are used to assess the acoustic data collected during the high-speed wind-tunnel testing of a model scale advanced open rotor rig. [ABSTRACT FROM AUTHOR]

Regenerating codes and codes with locality are two coding schemes that have recently been proposed, which in addition to ensuring data collection and reliability, also enable efficient node repair. In a situation where one is attempting to repair a failed node, regenerating codes seek to minimize the amount of data downloaded for node repair, while codes with locality attempt to minimize the number of helper nodes accessed. This paper presents results in two directions. In one, this paper extends the notion of codes with locality so as to permit local recovery of an erased code symbol even in the presence of multiple erasures, by employing local codes having minimum distance >2. An upper bound on the minimum distance of such codes is presented and codes that are optimal with respect to this bound are constructed. The second direction seeks to build codes that combine the advantages of both codes with locality as well as regenerating codes. These codes, termed here as codes with local regeneration, are codes with locality over a vector alphabet, in which the local codes themselves are regenerating codes. We derive an upper bound on the minimum distance of vector-alphabet codes with locality for the case when their constituent local codes have a certain uniform rank accumulation property. This property is possessed by both minimum storage regeneration (MSR) and minimum bandwidth regeneration (MBR) codes. We provide several constructions of codes with local regeneration which achieve this bound, where the local codes are either MSR or MBR codes. Also included in this paper, is an upper bound on the minimum distance of a general vector code with locality as well as the performance comparison of various code constructions of fixed block length and minimum distance. [ABSTRACT FROM PUBLISHER]

The thirteen articles in this special section are devoted to mobile multimedia communications with a focus on green-based services. The objective of this special section is to cover the most recent research and development on the enabling technologies for green mobile multimedia communications and to stimulate discussions on state-of-the-art and innovative aspects in the field. [ABSTRACT FROM PUBLISHER]

Editorial. Discusses the articles on broadband Internet and electronic commerce published in the December 2003 of the "Journal of Information Technology". Counter-intuitive result regarding broadband impact on users' buying behavior; Broadband developments in South Korea.

Metamaterial absorber (MA) is a hot spot in the research on electromagnetic absorbers. In this paper, a metamaterial based broadband polarization-insensitive absorber is proposed. The absorber is fabricated with FR-4 dielectric substrate foiled with copper. The top layer of the unit cell of the MA is composed of resistors mounted crosswire and gradient split ring resonator (SRR) with a square metal patch (SMP) in it. The overall structure is symmetrical, which makes the MA polarization-insensitive. The gradient SRRs and SMPs resonate at adjacent frequencies resulting in broadband property. The absorption rates of the MA for TE and TM wave are calculated through the simulated S-parameters. The bandwidth is 9.9 GHz, where the absorption rate maintains 60% up to 98.28% in both cases and the relative bandwidth is 57.13%. Both broadband and polarization-insensitivity properties are achieved, which demonstrate promising application prospect of the proposed MA in shielding and stealth technology. [ABSTRACT FROM AUTHOR]

This paper presents a review study on the data communication over power-lines, commonly referred to as power-line carrier, power-line communication (PLC), mains communications, or power-line digital subscriber line (PDSL). This study examines the technical and application advantages and challenges associated with adopting PLC as a preferred alternative technology for wideband or broadband data communication. The broader coverage area of the PLC network gives it a distinct advantage over other communication network technologies. Additionally, implementing a communication system using the existing power-line network is more cost-effective and less time-consuming compared to constructing a new network from scratch. However, the primary challenge lies in the fact that the power-line network is primarily designed for the distribution of electrical power within the frequency range of 50-60 Hz including the harmonics. This poses various obstacles such as electrical noise from appliances, signal distortions caused by the unregulated nature of the wiring, transformer bypassing, interference from high-frequency modulation, and variations in characteristic impedances, among others. Despite these challenges, the emergence of robust modulation techniques like Orthogonal Frequency Division Multiplexing (OFDM) and Direct-Sequence Spread Spectrum (DSSS), along with the development of Application-Specific Integrated Circuit (ASIC) density with improved processing speeds, as well as advancements in signal processing and error control coding techniques, have made the PLC network the most promising telecommunications access network. [ABSTRACT FROM AUTHOR]

The article lists the topics for publication in the forthcoming issues of the journal "Econometrica" including model-free tests for the housing markets, residential broadband demand and pricing.

To disguise man-made communications as natural signals, underwater transceivers have the option to pre-record animal vocalizations, and play them back in a way that carries meaningful information for a trained receiver. This operation, known as biomimicking, has been used to perform covert communications and to emit broadband signals for localization, either by playing pre-recorded animal sounds back into the environment, or by designing artificial waveforms whose spectrum is close to that of bioacoustic sounds.However, organic sound-emitting body structures in animals have very different trans-characteristics with respect to electro-acoustic transducers used in underwater acoustic transceivers. In this paper, we observe the distortion induced by transmitting pre-recorded animal vocalization through a transducer's front-end, and argue that such distortion can be detected via appropriate entropy metrics. We test ten different metrics for this purpose, both via emulated transmission and in two field experiments. Our result indicate which signals and entropy metrics lead to the highest probability of detecting transducer-originated distortions, thus exposing ongoing covert communications. Our research emphasizes the limitations that man-made equipment incurs when reproducing bioacoustic sounds, and prompts for the choice of biomimicking signals that are possibly suboptimal for communications or localization, but help avoid exposing disguised transmissions. [ABSTRACT FROM AUTHOR]

A very compact waveguide orthomode transducer (OMT) is described in this paper. The design is characterized with a twofold rotationally symmetric cross-section in the probing area, adapted from a side-coupling OMT design, simultaneously enabling low port-to-port coupling and high cross-polarization discrimination (XPD) over a fractional bandwidth of about 15–20%. Compared to previously reported compact waveguide OMTs, the proposed design is simpler, thus facilitating its manufacture at millimeter-wave frequencies. The concept is demonstrated with a design in the K-band for a broadband communication satellite downlink over the frequency band of 17.3–20.2 GHz. For test purposes, transitions to standard waveguide WR42 are included, and the OMT is assembled with a conical horn antenna. The measured reflection and coupling coefficients are below −19.5 dB and −22.9 dB, respectively, over the nominal bandwidth, and they are in good agreement with the simulation's results. The on-axis XPD, measured in an anechoic chamber, is better than 30 dB over the nominal bandwidth, which is also in line with simulations. The proposed waveguide OMT may be designed to fit in a lattice below one wavelength at the highest operating frequency, which is desirable for dual-polarized closely spaced array antennas in low and medium Earth orbit communication satellite systems. The simple mechanical design of the proposed OMT makes it particularly appealing for additive manufacturing techniques, as demonstrated with a variant of the design having folded single-mode waveguides, which preserves the RF properties of the original design. [ABSTRACT FROM AUTHOR]

The design and optimization methodology for CT ΣΔ modulators with hybrid Active-Passive (AP) loop-filters is indicated in this work. From the discussion, by appropriately scaling the passive filter gain and cooperating with a single-bit quantizer, the hybrid AP loop filtering can achieve an approximated noise-shaping function as a fully active ΔΣ modulator with the same order. The ELD effect in the hybrid AP CT ΔΣ modulator which influences the poles and zeros locations of the Noise Transfer Function (NTF) in the modulator is depicted. This paper also investigates the feasibility of applying the ELD compensation techniques that were used to be implemented in the active integrator's case to the hybrid AP CT ΔΣ modulator; however, some of them cannot be practically applied since the passive loop-filter cannot perform proportional feedback signal summation. After the discussion and analysis, the technique similar to Vadipour et al. (In: Symposium on VLSI circuits digest of technical papers, ) can be easily implemented at circuit-level and after applying it, there is one additional zero to compensate the peak in the NTF. With the help of this technique, the maximum quantizer delay tolerance can be a full clock period. The mentioned ELD compensation technique was applied in a 2nd order CT ΔΣ modulator with an active-RC integrator as the 1st stage and a passive RC filter as the 2nd stage, which was verified by transistor-level simulations in 65 nm CMOS. The circuit exhibits either 67.3 dB or 65.3 of SNDR, under the effect of half clock period or one clock period ELD, respectively; by contrast, without compensation, the system is unstable with both half or one clock period ELD effect. The designed hybrid CT ΔΣ modulator achieves 2 MHz signal bandwidth and consumes 2.54 mW of power. [ABSTRACT FROM AUTHOR]

Because of its outstanding performance in extending coverage and reducing transmit power, wireless relay cooperation is deemed as one of the promising techniques to realize green-broadband communication in the future. In such relay cooperative systems, optimal power allocation not only can prolong the lifetime of users, but also is an effective way to reduce radiation in the environment. In this paper, for amplify-and-forward-relay cooperative networks, where multiple communication pairs share a common relay, we propose a novel power allocation scheme, which has considerably lower complexity compared with the existing solution schemes. The objective of this paper is to minimize sum-source-power consumption under the conditions that the transmit power of all nodes in the network is constrained and their predetermined target signal-to-noise ratios are satisfied. By providing sufficient analytical evidence, we study the optimality, convergence, and computational complexity of our proposed scheme. Through numerical simulation, we further justify the effectiveness and efficacy of our scheme compared with the existing works. [ABSTRACT FROM AUTHOR]

Hybrid analog/digital precoding offers a compromise between hardware complexity and system performance in millimeter wave (mmWave) systems. This type of precoding allows mmWave systems to leverage large antenna array gains that are necessary for sufficient link margin, while permitting low cost and power consumption hardware. Most prior work has focused on hybrid precoding for narrow-band mmWave systems, with perfect or estimated channel knowledge at the transmitter. MmWave systems, however, will likely operate on wideband channels with frequency selectivity. Therefore, this paper considers wideband mmWave systems with a limited feedback channel between the transmitter and receiver. First, the optimal hybrid precoding design for a given RF codebook is derived. This provides a benchmark for any other heuristic algorithm and gives useful insights into codebook designs. Second, efficient hybrid analog/digital codebooks are developed for spatial multiplexing in wideband mmWave systems. Finally, a low-complexity yet near-optimal greedy frequency selective hybrid precoding algorithm is proposed based on Gram–Schmidt orthogonalization. Simulation results show that the developed hybrid codebooks and precoder designs achieve very-good performance compared with the unconstrained solutions while requiring much less complexity. [ABSTRACT FROM PUBLISHER]

Phase noise (PHN) and in-phase/quadrature (I/Q) imbalance are two major radio-frequency (RF) impairments in directconversion wireless transceivers. Beamforming and orthogonal frequency-division multiplexing (OFDM) schemes have been adopted in broadband wireless standards due to their significant performance gains. In this paper, we analyze the impact of joint I/Q imbalance and PHN on beamforming OFDM direct-conversion transceivers. We derive an exact normalized-mean-square-error expression (NMSE) and examine several special and asymptotic cases to gain insights. One such insight is that, asymptotically, for both large signal-to-noise ratio (SNR) and the beamforming array size, the PHN and I/Q imbalance effects become decoupled. [ABSTRACT FROM AUTHOR]

In this paper, we present a frequency analysis of a compensated impedance inverter and its effective implementation in the context of high-power Doherty amplifier (DPA) design. On the basis of an idealized DPA model, we calculate the expected operative bandwidth and the corresponding maximum drain efficiency as a function of the modulated signal statistics. In addition, we introduce an effective technique for the implementation of the compensated impedance inverter, suitable for preserving its broadband characteristics in the presence of large device’s output capacitance. The implementation technique is based on the generalized equivalent transmission-line equivalence principle, which considers both shortening and lengthening the equivalent transmission lines. We demonstrate that, by the proposed approach, parasitic absorption is possible maintaining a low $Q$ -factor of the equivalent network. The technique is validated by the development of a silicon laterally diffused metal–oxide–semiconductor DPA with optimized peak power and efficiency for applications in the 650–950-MHz band. The fabricated prototype is characterized by an LTE signal with a 20-MHz bandwidth and peak-to-average-power ratio of 7.5 dB and features an average drain efficiency between 37% and 47%, with an average power of 49 dBm across 37.5% of the bandwidth. [ABSTRACT FROM PUBLISHER]

In this paper, the impact of different setting parameters on the performance of a microwave microscope is evaluated. This study is performed on a homemade near-field scanning microwave microscope built up with a conventional vector network analyzer and a vertical coaxial evanescent probe. A broadband matching network based on an interferometric technique is inserted between the analyzer and the probe to enhance the measurement sensitivity/accuracy in the frequency range 2–20 GHz. The performance of the system in terms of measurement accuracy and stability is derived as a function of different setting parameters. Microwave surface imaging of subwavelength features is evaluated as a demonstration. This paper provides a guide for best practice in microwave microscopy. [ABSTRACT FROM AUTHOR]

This paper describes a new approach for the theoretical design of unequal multisection Wilkinson power dividers, using single-layer microstrip lines. Similar to most multisection structures, the presented unequal divider can provide a broadband performance. To provide the design guideline, closed-form formulas are derived for the divider with odd or even number of sections. In each case, various simulations have been conducted to investigate the performance of dividers over the frequency band. For experimental verifications, two 1:2 power dividers with a center frequency of 1 GHz are fabricated, having three and four sections. The simulated and measured results are presented, and good agreements between them are observed. [ABSTRACT FROM PUBLISHER]

The results of a wideband channel measurement campaign carried at Ku-band and X-band are presented and discussed in this paper. The propagation effects in the satellite-to-mobile radio link due to the environment surrounding the terrestrial terminal have been characterized using a sweep time delay cross-correlation (STDCC) sounder. The campaign was carried out in four different environments: wooded, rural, suburb and urban. From these results, we obtained the root-mean-square delay spread and coherence bandwidth of the radio channel. The low coherence bandwidth values found for urban and suburb environments suggest that channel equalization would be needed for high-data-rate services. The delay spread values for these two environments are also larger than for wooded and rural environments. A detailed analysis of the results shows that three-state semi-Markov narrow-band channel models for satellite communications could be easily extended to wideband. [ABSTRACT FROM AUTHOR]

One way to reduce bandwidth requirement in video-on-demand system is using periodic broadcasting for popular videos. It periodically broadcasts video segments on several channels and clients need to wait some time to access the video. Many periodic broadcasting schemes have been proposed to reduce server’s bandwidth and client’s waiting time. However, most of these schemes assume all clients have enough reception bandwidth which is, in fact, different in various network environment. To solve this problem, two types of broadcasting schemes have been proposed: 1) reception bandwidth adaptable (RBA) and 2) reception bandwidth limited (RBL) approaches. RBA includes HeRO, BroadCatch, CAR, FBR, and MBC. RBL contains CCA, CCA+, CCA++, and GDB. In this paper, we propose a novel RBL approach called delay receiving (DeRe) to accomodate the heterogeneous receiving problem. By limiting client’s reception bandwidth to two or three channels, we achieve relatively low service latency for all users compared to other schemes. Also, DeRe scheme is allowed to adjust buffer requirement directly, which is a unique property among all broadcasting schemes. The performance evaluation results of DeRe scheme with buffer requirement of 15% and 20% of video size are presented in this paper. [ABSTRACT FROM PUBLISHER]

In this paper, we demonstrate ultra-fast millimeter wave beam steering with settling times below 50 ps. A phased array antenna with two elements is employed to realize beam steering. The phased array feeder is implemented with a recently introduced time delay line that provides, at the same time, an ultra-fast tunability, broadband operation, and continuous tuning. Our implementation is used to perform symbol-by-symbol steering. In our demonstration, the beam direction is switched between two sequentially transmitted symbols toward two receivers placed 30° apart. We show the successful symbol-by-symbol steering for data streams as fast as 10 GBd. The suggested scheme shows that the ultra-fast beam steering is becoming practical and might ultimately enable novel high bit-rate multiple access schemes. [ABSTRACT FROM AUTHOR]

This paper introduces a new realization for a phase-domain line model and proposes methodologies to increase its numerical performance. The new realization is based on the management of complex poles that may arise when deriving rational models by means of second-order states. The accuracy and numerical performance of the proposed realization is assessed through its application to representative examples and the comparison against other methodologies. It is demonstrated that the proposed methodology can increase substantially the numerical efficiency of the model. [ABSTRACT FROM PUBLISHER]

This paper addresses a critical gap in telecom regulators' awareness of the climate impact of their policy decisions and highlights the substantial potential of broadband technology to reduce greenhouse gas emissions (GHGe). Empirical evidence shows that broadband can achieve a GHGe reduction of approximately 15–20%, a notable efficiency given its relatively low direct emissions of around 0.4–1.0% of global emissions. This analysis substantiates the premise that effective telecom policy serves as robust climate policy. The paper argues for a global alignment of telecom and climate policies, advocating for an integrated approach that acknowledges the deep interdependencies between these sectors. Key policy recommendations include targeted subsidies for broadband in rural areas, strategic spectrum allocation, and comprehensive incentives for green technology adoption across consumers, industries, and governments. The goal is to prompt a reevaluation of policy frameworks, urging advanced economies to harness the full potential of digital infrastructure to combat climate change. • Broadband technologies contribute only about 0.4–1.0% of direct GHGe within the ICT sector, underscoring their efficiency as sustainable technologies. • Broadband adoption can enable a significant reduction in GHGe, estimated at 15–20%, by facilitating low-carbon consumer behaviors, optimizing industrial practices, and enhancing government services. • There is a significant gap in awareness among telecom regulators about the climatic consequences of their decisions. • Targeted education and collaboration initiatives are essential to increase awareness and integrate climate considerations into telecom policy. • The pressing nature of the climate crisis necessitates translating academic findings into concrete policies. • This includes removing regulatory barriers to network investments, optimizing spectrum allocation for energy-efficient technologies, and developing comprehensive incentive programs for consumers, industries, and governments. [ABSTRACT FROM AUTHOR]

The Affordable Connectivity Program (ACP) represents a historic investment by the federal government to address the digital divide. Its goals are both to increase the rate of broadband adoption and make it easier for low-income households to sustain service. But what have been the drivers of ACP enrollment? We know a great deal about trends in adoption and the geography of enrollment among eligible households. But those metrics – especially a focus on enrollment rates among eligible households – are only so useful in explaining ACP sign-ups. This invites analysis that investigates the drivers of ACP enrollment in a comprehensive way, which this paper proposes to do. The paper hypothesizes that ACP enrollment decisions are not solely individual (i.e., that a household's enrollment decision is structured only by income level), but also influenced by community-wide considerations, such as housing costs, share of occupied houses, presence of anchor institutions such as public libraries, and population density (i.e., whether a place is urban or rural). The paper develops a regression model that predicts ACP enrollment rates among eligible households at the 5-digit zip code geography as a function of the variables discussed above, as well as others such as the racial and ethnic make-up of a zip code area. The analysis also controls for existing levels of broadband subscriptions and computer ownership in a given area. The difference between predicted and actual ACP enrollment rates at the 5-digit zip code level is proposed as a metric of ACP performance. These findings are supplemented with a geographically weighted regression (GWR) model that allows the relationship between each explanatory variable and ACP enrollment to vary by locality. This allows for analyzing and visualizing how these relationships vary across space. The empirical findings show that high levels of economic distress are a strong determinant of ACP enrollment in a given area, but social and community-wide indicators are important as well. The GWR results demonstrate that important differences in these relationships exist across geographies. Understanding spatial variations in ACP performance can help policymakers and other stakeholders better target resources to address the digital divide. • We provide background on the ACP, a recent program that subsidizes broadband service for low-income U.S. households. • We estimate ACP enrollment using both ordinary least squares (OLS) and geographically weighted regression (GWR). • OLS results show that economic distress and local library presence are strongly positively associated with ACP enrollment. • Higher rates of foreign-born or elderly residents are negatively associated with ACP enrollment. • GWR results show that relationships between ACP enrollment and local characteristics vary widely and are context-specific. [ABSTRACT FROM AUTHOR]

The novel idea of integrating Radio Frequency Identification (RFID) with sensors along with other wireless applications by using single tag antenna is implemented, by fabricating proposed antenna using state-of-the-art inkjet printing technology on commercially avail-able paper substrates. For the first time, a parametric analysis is performed for realization of the planar log-spiral antenna on paper for operational range from 0.8 to 3.0 GHz, which also exhibits excellent coverage throughout numerous RFID Industrial, Scientific and Medi-cal (ISM) bands, and for other wireless applications. The ANSYS HFSSTM tool is used to design and predict the performance of the proposed antenna in terms of radiation pattern and input impedance. [ABSTRACT FROM AUTHOR]

Various physical limitations in electromagnetic theory and antenna theory have received considerable attention recently. However, there are no previous limitations on the scattering of higher order electromagnetic vector spherical waves, despite the widespread use of spherical wave decompositions. In the present paper, bandwidth limitations on the scattering matrix are derived for a wide class of heterogeneous objects, in terms of their electrical size, shape and static material properties. In particular, it is seen that the order of the dominating term in the Rayleigh limit increases with the order of the spherical wave. Furthermore, it is shown how the limitations place bounds on the antenna scattering matrix, thus introducing a new approach to physical limitations on antennas. Comparisons to other types of antenna limitations are given, and numerical simulations for two folded spherical helix antennas and a directive Yagi-Uda antenna are included to illuminate and validate the theory. The results in this paper are derived using a general approach to derive limitations for passive systems: First, the low-frequency asymptotic expansion of the scattering matrix of a general scatterer is derived. This gives a set of sum rules, from which the limitations follow. [ABSTRACT FROM PUBLISHER]

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Security is the main concern and bottleneck for widely deployed wireless applications due to the fact that wireless channels are vulnerable to attacks and that wireless bandwidth is a constrained resource. In this sense, it is desirable to adaptively achieve security according to the available resource. In particular, mobile ad hoc networks (MANETs) based on cooperative communication (CC) present significant challenges to security issues, as well as issues of network performance and management. In this paper, we focus on authentication and topology control issues. Although authentication and topology control are separately studied in most existing works, they are, in fact, closely correlated in MANETs. For example, both authentication and topology control schemes have significant impacts on throughput. In this paper, we jointly consider authentication and topology control. Specifically, we analyze the effective throughput with upper layer authentication schemes and physical-layer schemes related to channel conditions and relay selections for CCs. A joint authentication and topology control (JATC) scheme is proposed to improve the throughput. JATC is formulated as a discrete stochastic optimization problem, which does not require prior perfect channel status but only channel estimate. We also mathematically prove the tracking convergence property and the convergence rate of the discrete stochastic optimization approach in this paper. Simulation results show that our scheme can substantially improve throughput in MANETs with CC. [ABSTRACT FROM PUBLISHER]

In this paper, Optimization of Micro-strip patch antenna is presented. Optimization has done by several steps, by the changing the dimensions (L1 and W1) and Width and length of open circuit U-Slot stub of parasitic patches on the top layer, by placing feeding patch at the middle layer of geometry, by indirect coupling between top and middle layer patches. Overall we have performed much possible iteration and find out appropriate geometry. From this appropriate geometry we have achieved large flat gain approx 7dB over 8GHz Bandwidth slot. Broadband frequency of operation demonstrated by single geometry. For broadening the bandwidth and maximum directional gain gap- coupled open circuit U-Slot stub loaded on parasitic. The geometry of a single probe fed rectangular Micro-strip antenna incorporating a slot and gap coupled with parasitic and active patch on left side of geometry have studied. We have investigated height between active and parasitic patch should be .0525λ and height between parasitic patch itself should be .0525λ. We have investigated enhancement in maximum directional gain by stack geometry with one active patch and one parasitic patch of different dimensions. We have achieved 89% of X-Band and 14% of Ku - BAND in all optimizations section. This Optimized antenna is used for X-Band and Ku. [ABSTRACT FROM AUTHOR]

We investigate the problem of downlink user scheduling in multiple-input multiple-output (MIMO) systems with M transmit antennas and K homogeneous multiantenna receiving users. We develop a simple algorithm to schedule a subset of M active users for data transmission.We first identify a set of L candidate users that should provide channel information feedback. We then select M active users among the L candidates based on joint consideration of their effective channel gains and directions. We derive an asymptotic upper bound for the sum rate gap between the maximum sum rate of the M selected active users, achieved by dirty paper coding, and the full sum capacity of the original MIMO broadcast channel. Utilizing the upper bound, we show that the sum rate gap can be reduced to meet user requirement by suitably choosing a large but still finite L. Furthermore, we also investigate the performance of the low complexity zero-forcing beamforming (ZFBF) for the M active users. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including wide-band radio frequency channelizer architecture, optimal two-stage comb decimators, and power efficiency for high-voltage DC-DC converters.

Purpose — This paper aims to give conclusions from the papers in the special issue about "Re-thinking universal service in the digital era". Design/methodology/approach — A summary of the themes, trends and new concepts about universal service is compiled from the varied viewpoints introduced in the issue. The editors also appraise the mobile and broadband universal service candidates under the different perspectives in the issue, point out a number of questionable assumptions and gaps in the universal service stories, and touch on the international currents of influence in universal service policy Finally a succinct vision of a universal service policy for Europe is outlined. Findings — This special issue aims to provide support to the policy process with regard to universal service in a digital context. The papers in the issue highlight developments that are shaking up the current universal service model. They consider universal service from a set of different dimensions, encompassing both demand and supply side considerations. Also a comparative outlook draws lessons from a representative set of existing regulatory models. Originality/value — The paper provides a summary of the main avenues for the upcoming universal service policy debate. [ABSTRACT FROM AUTHOR]

This paper presents an ejJicient discrete-time bandpass sigma-delta (.ZA) modulator and digital in-phase /quadrature (I/Q) demodulator for multistandard wireless applications. The proposed bandpass IA modulator provides higher speed using advanced switched-capacitor resonators which are faster than the conventional ones. The test chip has been implemented in a 0.18 jim CMOS process and occupied with the active chip area of 0.16 mm2. The power consumption of the fabricated chip is 2.34 mWwith a 1.8 Vsupply voltage. The measured peak signal-to-noise ratios (SNR) are 34 dBfor 1.536 MHz (T-DMB), 26 dB for 5 MHz (UMTS), and 20 dB for 10MHz (WiBro) bandwidths, respectively. This paper also covers the simple and robust digital I/Q demodulator which has been realized using a field programmable gate array (FPGA) for digital signal processing'. [ABSTRACT FROM AUTHOR]

Capacity improvement from transmitter and receiver cooperation is investigated in a two-transmitter0 two-receiver network with phase fading and full channel state information (CSI) available at all terminals. The transmitters cooperate by first exchanging messages over an orthogonal transmitter cooperation channel, then encoding jointly with dirty-paper coding. The receivers cooperate by using Wyner-Ziv compress-and-forward over an analogous orthogonal receiver cooperation channel. To account for the cost of cooperation, the allocation of network power and bandwidth among the data and cooperation channels is studied. It is shown that transmitter cooperation outperforms receiver cooperation and improves capacity over noncooperative transmission under most opt, rating conditions when the cooperation channel is strong. However, a weak cooperation channel limits the transmitter cooperation rate; in this case, receiver cooperation is more advantageous. Transmitter-and-receiver cooperation offers sizable additional capacity gain over transmitter-only cooperation at low signal-to-noise ratio (SNR), whereas at high SNR transmitter cooperation alone captures most of the cooperative capacity improvement. [ABSTRACT FROM AUTHOR]

One of the characteristics of ultrawideband (UWB) signals is pulse distortion, which is inherently determined by their huge bandwidth. Using a cylinder model as an example, pulse distortion and its impacts on UWB system performance have been investigated, based on the closed-form impulse response first derived in this paper. Although a lot of papers have addressed the pulse-distortion issue, quantifying the impacts of pulse distortion on system performance appears to be novel. The simulation results show that the SNR loss caused by template mismatch could reach as high as 4 dB. It is also found that the range error caused by pulse distortion is much larger than the Cramer-Rao lower bound; thus, it is another fundamental source of errors limiting the accuracy of times of arrival of a received signal. These results have direct applications in timing synchronization and positioning. [ABSTRACT FROM AUTHOR]

This paper analyzes carrier-signal voltage injection zero-sequence current-based sensorless control techniques for delta-connected three-phase ac machines. The analysis will focus on rotor position estimation (tracking of rotor-position-dependent saliencies), but the method applies equally well to flux position estimation (tracking of flux-dependent saliencies). The paper first develops a theoretical model and then provides analysis of relevant implementation aspects, such as selection of carrier-signal frequency and voltage magnitude, measurement of the zero-sequence carrier-signal current, measurement and compensation of saturation-induced saliencies, and the signal processing needed for position/flux angle estimation. A similar implementation to that proposed in this paper, and with practically the same performance in terms of accuracy and estimation bandwidth, can be obtained for the case of wye-connected machines using the zero-sequence carrier-signal voltage, as shown in IEEE Trans. Ind. Appl., vol. 41, no. 6 pp. 1637-1646, Nov./Dec. 2005. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to examine the widely-held assumption that broadband infrastructure will bring social and economic benefits. Design/methodology/approach - The paper examines the impacts of broadband in Korea, a country with the highest penetration rate of broadband. The current status of broadband in Korea is examined, followed by an assessment of its impact on electronic commerce, overall economic effects and new business opportunities. Findings - There is evidence of positive impacts of broadband development in Korea. Most importantly, broadband internet not only provides a driving force for new businesses for related industries, but also forms a springboard for future infrastructure in the network economy. Research limitations/implications - The paper focuses on positive impacts, which are largely anecdotal, and does not seek to assess negative impacts. Originality/value - There has been little research into the socio-economic benefits of broadband. In addition, the paper provides a snapshot of development in South Korea. [ABSTRACT FROM AUTHOR]

This paper proposes a multi-stages hybrid ARQ/FEC scheme with frame skipping, reference frame selecting and intra-frame refreshing techniques for H.26L real-time video streaming over WLAN. In this paper, adaptive ARQ/FEC is adopted to save unnecessary FEC overhead; conditional frame skipping is adopted to avoid ETE delay inflation due to MA C ARQ/FEC error recovery; reference frame selecting is adopted to save bandwidth; intra-frame refreshing is adopted to prevent residual error propagation among consecutive frames. Through analysis and simulation, we show that multi-stages hybrid ARQ scheme has the following key properties: (1) high error recovery rate for real- time video frames, (2) excellent scalability, (3) high transmission efficiency. In case of severe unreliable channel which causes losing a lot of IP packets, we obtain a peak signal-to-noise ratio improvement up to about 10dB compared to the hybrid ARQ proposed in [1]. [ABSTRACT FROM AUTHOR]

Introduces a series of articles which deals with technological innovations in ultra-broadband wireless communications.

With the ever increasing demand for higher speed internet connectivity that can fulfil the application continuous need for higher bandwidth Google being the pioneer in many web-based services has launched a new UDP-based protocol named quick UDP internet connections (QUIC), which aims at providing faster data delivery without requiring upgrades or modifications to the network infrastructure. The goal of this paper is to provide an overview about QUIC protocol, propose the design and implementation of a test-bed, that is used experimentally to evaluate QUIC protocol under different network conditions and scenarios. In particular, the performance advantage of QUIC in terms of delay and throughput are examined taking into account different network conditions that resemble the real internet environment. Two scenarios are proposed, the first one investigates the protocol performance under a controlled network environment, while the second one tests the protocol in a real uncontrolled network. To achieve that, a test-bed is proposed and implemented that emulates the network impairments encountered in real-network such as packet loss, bit errors, and bandwidth limitation in a controlled manner. After that, QUIC is tested in real operational wired and wireless networks. In both scenarios, QUIC outperforms TCP in terms of delay, which strengthens QUIC position for being a potential alternative to TCP. [ABSTRACT FROM AUTHOR]