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This paper proposes a novel dual-mode substrate integrated waveguide (SIW) filter technique. Based on the conventional dual-mode SIW structure, further investigation is performed. Multiple transmission zeros can be obtained at one side or both sides of the passband for an SIW cavity. Therefore, flexible design and high performance response can be available for dual-mode SIW filter. A dual-mode SIW bandpass filter with quasi-elliptic response and a dual-mode SIW diplexer with asymmetric channel response are simulated, fabricated, and measured to demonstrate and verify the novel property. [ABSTRACT FROM PUBLISHER]

A new design of high selectivity wideband bandpass filter based on transversal signalinteraction concepts loaded with open and shorted stubs is proposed in this paper. Two transmission paths are used to realize signal transmission. Path 1 is composed of a T-shaped structure with shorted stub, and Path 2 consists of two open coupled lines loaded with open stubs. A wide five-order passband and high selectivity stopband with four transmission zeros can be achieved in the proposed filter. Finally, a wideband bandpass filter operating at 3GHz with 3-dB fractional bandwidth of 83.3% (1.55 to 4.05 GHz) is designed, fabricated, and measured. Good agreement between the simulation and experiment is obtained. [ABSTRACT FROM AUTHOR]

This paper proposes efficient analytical models to dimension the necessary transport bandwidths for the Long Term Evolution (LTE) access network satisfying the QoS targets required by different services. In this paper, we consider two major traffic types: elastic traffic and real time traffic. For each type of traffic, individual dimensioning models are proposed for both the S1 interface and the X2 interface. For elastic traffic the dimensioning models are based on the Processor Sharing models; while for real time traffic the dimensioning models are based on the fundamental queuing models. For validating these analytical dimensioning models, a developed LTE system simulation model is used. Extensive simulations are performed for various traffic and network scenarios. The analytical results derived from the proposed dimensioning models are compared with the simulation results. The presented results demonstrate that the proposed analytical models can appropriately estimate the required performances for different service classes and priorities. Hence they are suitable to be used for dimensioning of the LTE access network with different traffic and network conditions. [ABSTRACT FROM AUTHOR]

The paper presents an admission approach for IPTV service providers that is designed to minimize QoS violations whilst effectively utilizing available bandwidth. Central to the approach is an empirical method of estimating the effective bandwidth required to satisfy QoS targets for admitted traffic flows. The paper describes this method and specifies two admission control algorithms based on the use of effective bandwidth estimates. The first algorithm employs a simple evaluation of whether there is sufficient bandwidth available to ensure, with an appropriate degree of confidence, that QoS targets will not be violated if a requested flow is admitted. The second algorithm utilizes information relating to the cost, duration and request frequency of specific IPTV content to prioritize higher revenue flows within the admission control process. Results of a simulation study (employing real traffic traces of long-lived flows) indicate that the proposed algorithms ensure that an adequate, but not overly generous, amount of bandwidth is allocated to ensure that QoS targets for accepted flows are met. Furthermore, they demonstrate the potential advantage of using content specific information in the admission control process to maximize generated revenue. [ABSTRACT FROM AUTHOR]

The emerging multiprotocol label switching (MPLS) networks enable network service providers to route bandwidth guaranteed paths between customer sites. This basic label switched path (LSP) routing is often enhanced using restoration routing which sets up alternate LSPs to guarantee uninterrupted connectivity in case network links or nodes along primary path fail. In this paper, we address the problem of distributed routing of restoration paths, which can be defined as follows: given a request for a bandwidth guaranteed LSP between two nodes, find a primary LSP, and a set of backup LSPs that protect the links along the primary LSP. A routing algorithm that computes these paths must optimize the restoration latency and the amount of bandwidth used. In this paper, we introduce the concept of "backtracking" to bound the restoration latency. We consider three different Cases characterized by a parameter called backtracking distance D: 1) no backtracking (D = 0); 2) limited backtracking (D = k); and 3) unlimited backtracking (D = ∞). We use a link cost model that captures bandwidth sharing among links using various types of aggregate link-state information. We first show that joint optimization of primary and backup paths is NP-hard in all cases. We then consider algorithms that compute primary and backup paths in two separate steps. Using link cost metrics that capture bandwidth sharing, we devise heuristics for each case. Our simulation study shows that these algorithms offer a way to tradeoff bandwidth to meet a range of restoration latency requirements. [ABSTRACT FROM AUTHOR]

Passive optical networks are currently the most promising solution for access networks. Increasing bandwidth requirements and big data applications need a huge bandwidth. Nowadays, gigabit passive optical networks do not seem to be suitable for these purposes. This paper is focused on describing the development, parameters and needs for High Speed Access Networks (such as 100G EPON). The simulations with current wavelengths plans are presented. For simulations we used VPITransmissionMakerTM 9.7. Our goal was to create a rudimentary bidirectional PON system with one ONU and do several simulation scenarios by artificially increasing loss in a splitter for simulating more ONUs. Our following results consist of BER values and eye diagrams for each simulation scenario and proof that 100G EPON networks are most promising networks for the future. We proved that the 100G-EPON networks fully support the basic and currently used split ratios. We also created a two-way communication model and evaluated the obtained data from the bit error-rate and system reach point of view. The entire model was compared with the final version of NG-PON2. [ABSTRACT FROM AUTHOR]

Wireless mesh networks (WMNs) are considered to be an economical solution for last-mile broadband Internet access. In this paper, we study end-to-end bandwidth allocation in WMNs with cognitive radios, which involves routing, scheduling, and spectrum allocation. To achieve a good tradeoff between fairness and throughput, we define two fair bandwidth-allocation problems based on a simple max-min fairness model and the well-known lexicographical max-min (LMM) fairness model, respectively. We present linear programming (LP)-based optimal and heuristic algorithms to solve both problems. Extensive simulation results are presented to justify the effectiveness of the proposed algorithms. [ABSTRACT FROM AUTHOR]

This paper reports a wide bandwidth planar bandstop filter with improved RF characteristics. The proposed filter on alumina is realized incorporating tapped open stub along with spurline topology. Further, stepped impedance resonator (SIR) approach has been introduced in the tapped stubs to achieve wider band performance with improved selectivity. The proposed topology effectively controls the transmission poles. Fabrication of this BSF has been carried out on glass substrate showing minimal effect of permittivity variation on bandwidth performance. This validates the applied approach with achievable bandwidth of more than 100% ranging from S- to Ku-band. Close agreement with simulation and practical results have been demonstrated with measured insertion loss of less than 1 dB and attenuation loss better than 30 dB at C-band. [ABSTRACT FROM AUTHOR]

Abstract  As the domain of communication systems grows, heterogeneity among computers and subnetworks employed for a task also increases. Channel bandwidth available for a message on a communication network varies with time and link. This variation can have a significant effect on performance of an individual message and also that of the network as a whole. Therefore, it is important to understand effects of bandwidth heterogeneity on the network performance in order to optimally utilize a heterogeneous communication network. The ability to use such a network optimally is highly desirable in many applications such as network-based data-intensive high performance computing. The main goal of this paper is to analyze effects of temporal and spatial heterogeneity on performance of individual messages in detail via an extensive simulation, in terms of throughput, end-to-end delay, etc. Also, the problems of path selection and multi-path data transfer are considered to illustrate how the analysis results may be used in the future effort of optimizing the network performance by taking channel bandwidth heterogeneity into account. [ABSTRACT FROM AUTHOR]

This paper analyzes the influence of amplitude and phase error of different path on single sideband modulator (SSB) which can be used as an upconverter. Unwanted sideband suppression expression and error variables equation for maximum output sideband suppression are also deduced. The simulation curve shows the variation of sideband suppression with the amplitude and phase error of the components of SSB is given. Simulation results show that components of the amplitude and phase of the highly consistent or inconsistent amplitude and phase which meet the relationship can achieve higher sideband suppression for the SSB. The completed modulator used as an upper sideband upconverter shows -11 dB typical conversion gain with 22-dB sideband suppression. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2590–2594, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23721 [ABSTRACT FROM AUTHOR]

A bandwidth-requirement estimation method to be used for a packet monitoring tool with a queue simulation function is proposed. Queue simulation is implied to be a function for real-time evaluation of the queuing delay by inputting a measured packet flow into a virtual queue (simulating the output buffer of a router). When this function is used, the probability characteristics of the packet flow can be more effectively understood than by the observation of only the arrival time and size of the packet. In this paper, estimation methods for two types of bandwidth requirement are proposed: the bandwidth needed to reduce the maximum value of the queuing delay to within the reference value, and the bandwidth needed to reduce the x% value of the queuing delay to within the reference value. Further, a simple real-time bandwidth-requirement estimation tool is fabricated and is combined with the packet monitoring function and the queue simulation function. The results of an experiment for verification of the estimation accuracy by using real-time traffic are reported. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(12): 75–87, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20291 [ABSTRACT FROM AUTHOR]

The 48 GHz band has been allocated world-wide for fixed service with HAPS. High-capacity broadband access networks can be implemented in this band. The main drawback is the troposphere effects on the propagation, particularly rain attenuation, that may limit the link availability. In this paper, the performance of HAPS-ground links working in this band is analysed by means of simulation. Experimental slant-path propagation data, gathered at 49.5 GHz, are used in the simulations, so that attenuation levels and their temporal evolution may be considered realistic. The simulated system is defined in ITU-R Rec. F-1500. Only urban coverage links are simulated, as the propagation data correspond to a 400 elevation link. The use of Fade Mitigation Techniques (FMT) is shown to be useful to improve the link performance. The improvement is evaluated for two different FMTs: Power control and adaptive coding. Results are presented regarding link availability and other parameters related to the particular FMT, as well as outage dynamics. [ABSTRACT FROM AUTHOR]

Relative motion (rm) between a signal source and a receiver causes a time scaling of the signal arriving at the receiver. When estimating the time-difference-of-arrival (TDOA) of a signal at two receivers, time scaling, when not properly accounted for, can introduce a bias that could dominate the estimation errors. Segmentization processing cannot reduce this bias. Following the derivation of the formulae for bias and mean-square errors of TDOA estimation under rm, this paper moves on to the joint estimation of TDOA and time scale. It proposes an iterative search for the maximization of the cross-ambiguity function (CAF), which is also the maximum likelihood function for additive Gaussian bandlimited white noise disturbance. In addition, a quadratic Lagrange interpolator is also proposed to obtain the initial parameter values for the iterative search, which can increase the chance of converging to the global minimum solution. It is necessary to time scale a digital sequence by a noninteger in the maximization process. For an N-point sequence, this operation, which first interpolates the samples by sinc functions and then resamples, is in the order O(N²). Noting that the magnitude of the sinc function decreases rapidly from its peak, this paper uses a fast approximation (FA) method that applies only five sinc coefficients for the interpolation, reducing the computation to O(N). Simulation results have corroborated that the maximization of the CAF does provide estimates that reach the Cramer-Rao lower bound and that the degradation in accuracy is negligible when FA is applied. [ABSTRACT FROM AUTHOR]

Ultra wide bandwidth (UWB) wireless technology will play a key role in short-range wireless connectivity supporting very high bit rates availability, low power consumption, and location capabilities. UWB can be conveniently deployed in the design of wireless local and personal area networks, providing advanced integrated multimedia services to nomadic users within hot-spot areas. The very large bandwidth required by the UWB signals cannot be exclusively allocated; thus, UWB band overlaps with the bands allocated to many other narrow-band systems. Therefore, the assessment of the interference caused by UWB devices on already- existing systems is of primary importance to ensure coexistence and, therefore, to guarantee acceptance of UWB technology worldwide. In this paper, we study the coexistence issues between an UWB-based system and universal mobile telecommunication systems, global positioning systems, OCS 1800, and fixed wireless access systems and point-to-point (PP) links terminals. UWB interference is evaluated accounting for the UWB signal model, a realistic UWB master/slave system architecture with power-controlled terminals. Furthermore, we analyze the dependence of the UWB interference from the UWB signal parameters and demonstrate through computer simulation that, in all practical cases, a UWB system can coexist with the selected victim terminals without causing any dangerous interference. [ABSTRACT FROM AUTHOR]

Bandwidth is an extremely valuable and scarce resource in a wireless network. Therefore, efficient bandwidth management is necessary in order to provide high-quality service to users in a multimedia wireless/mobile network. In this paper, we propose new online bandwidth-management algorithms for bandwidth reservation, call admission, bandwidth migration, and call-preemption strategies. These techniques are combined in an integrated framework that is able to balance the traffic load among cells accommodating heterogeneous multimedia services while ensuring efficient bandwidth utilization. In addition, our online framework to adaptively control bandwidth is a cell-oriented approach that has low complexity, which makes it practical for real cellular networks. Simulation results indicate the superior performance of our bandwidth-management framework to strike the appropriate performance balance between contradictory quality-of-service requirements. [ABSTRACT FROM AUTHOR]

In this paper, we design and evaluate an Internet friendly transport-level protocol (IFTP) for solving the TCP-friendly problem. IFTP has two modes of operation. In the standard mode, the IFTP connection faithfully emulates the behaviour of TCP in order to roughly obtain a bandwidth equal to that of a TCP connection. In the extended mode, a simple modification is used to grant QoS-differentiated services to selected connections. Connections running in the extended mode can get enhanced bandwidth while still emulating the general behaviour of TCP. We develop an analytical model for the congestion control mechanism of IFTP. We also derive analytically the amount of bandwidth that IFTP may be able to claim from TCP in ideal and non-ideal environments. We evaluate IFTP through simulation and prove its TCP friendliness as well as provide performance results on some of the important metrics such as packet delay, delay jitter, packet loss and link utilization. Copyright © 2002 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In the SLC (sidelobe canceler) which automatically suppresses the interference signals received by the sidelobe of the main antenna, there is a problem of suppression of the desired signal in addition to the interference signal if the desired signal power in the auxiliary antenna is larger than the receiver noise power and if the number of received interference signal is smaller than that of the auxiliary antennas. In this paper, an SLC is proposed in which the number of auxiliary antennas is adjusted automatically to be equal to that of the interference signals so that the problem of suppression of the desired signal is prevented. It is assumed here that both the desired signal and the interference signals have narrow bandwidths. In this SLC, with a view to adjusting the number of auxiliary antennas and the weights at the same time, the Gram-Schmidt SLC (GS-SLC) is used so that a sudden change of the input-output signal power ratio of the Gram-Schmidt processor is detected and the number of auxiliary antennas are made to coincide with that of the received interference signals. By way of a computer simulation, the fundamental characteristics of the present GS-SLC are evaluated. It is confirmed that the desired signal preservation property is improved in comparison with the conventional SLC. [ABSTRACT FROM AUTHOR]

SUMMARY Broadband communication via satellite systems finds applications in several contexts where other technologies are not available or economically not convenient. Examples are remote areas, disaster struck areas, or vessels/ships. The scarce availability and the high cost of the bandwidth impose to improve flexibility in bandwidth management and dynamic allocation, especially on the shared return link. Typically, this capability is available only to the satellite operator (SO). An innovative dynamic bandwidth management of satellite capacity for the return link has been developed and prototyped as an Internet protocol-based solution. This solution allows small operators renting bandwidth from the satellite operator and providing services to final customers, managing the permanently assigned resources in a flexible and efficient way. The scope of the paper is to illustrate this technique to achieve the dynamic bandwidth management for a subgroup of satellite terminals (subdomain) by using a centralized controller and distributed software with IP shaping capabilities, without interacting with the satellite operator. This approach has been applied in particular to a satellite maritime ship owner, which is thus able to dynamically distribute capacity among satellite terminals installed onboard of its ship fleet as required, as a network operator. The presented results are the outputs of simulations performed with the NS2 simulator and tests by using real hardware. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The compact C-shaped microstrip antenna derived from rectangular microstrip antenna has been mainly analyzed at its fundamental mode. In this paper, fundamental and higher order modes of proximity fed C-shaped microstrip antennas are discussed. The broadband proximity fed C-shaped microstrip antenna is proposed. At its fundamental mode, it yields bandwidth of more than 230 MHz (> 23%) with broadside radiation pattern and peak gain of more than 7 dBi. Further increase in its bandwidth is realized by cutting rectangular slot on the edges of the patch. The slot reduces TM01 mode frequency of C-shaped patch and along with its TM10 mode, yields bandwidth of more than 260 MHz (> 28%). To increase the gain, gap-coupled configuration of two C-shaped microstrip antennas is proposed. This gives bandwidth of more than 300 MHz with peak gain of 7.7 dBi. Further to enhance the bandwidth, gap-coupled configuration of two rectangular slot cut C-shaped microstrip antennas is proposed. The slot reduces TM01 mode frequency on each of the C-shaped patches and along with TM10 modes, yields bandwidth of more than 400 MHz (~40%) with broadside radiation pattern and peak gain of more than 8 dBi. [ABSTRACT FROM AUTHOR]

This paper describes a methodology to design a switched oscillator (SWO) together with its experimental validation. The dependence of the SWO resonance frequency, bandwidth, and quality factor upon spark-gap pressure, interelectrode distance, and transmission-line (TL) length is evaluated. The SWO simulation results obtained with both the TL model developed in the computer program EMTP-alternative transient program (ATP) and the electromagnetic (EM) model developed in the computer program Computer Simulation Technology (CST) Microwave Studio are compared. An SWO based on simulation results, connected to an impedance of 100 \Omega, was constructed and tested in the laboratory. Simulations and laboratory test results fit well. The proposed methodology, which combines TL and EM simulations, was experimentally validated, and it can be used to design SWO systems for different applications. [ABSTRACT FROM PUBLISHER]

Motivated by the need of resource flexibility in high throughput satellite systems, a hot-spot cell configuration is introduced and analyzed in terms of throughput performance. Cell partitioning and user scheduling are also addressed in conjunction with the application of different types of linear precoding algorithms. The analysis is based on a real satellite system design and uses a system simulation approach, encompassing the random user distribution inside the hot-spot cell area. Results provide guidelines on the design of the hot-spot cell partitioning and show the achievable gains of precoding with respect to conventional, non precoded, transmission. [ABSTRACT FROM AUTHOR]

This paper presents the design of a new dual band power divider realized on double-sided parallel-strip line (DSPSL). The proposed structure mainly features a simple planar structure with extreme power dividing ratio, wide bandwidth, excellent isolation and frequency-independent output phase performance for dual band application. Closed-form equations are derived for design parameters. For verification purpose, the simulated and measured results of a dual band power divider with power dividing ratio of 20:1 are shown. [ABSTRACT FROM AUTHOR]

The heavily loaded flows usually occupy more bandwidth than that of the lightly loaded flows under congested traffic conditions. Without effective bandwidth management mechanisms, malicious users may violate congestion control principles in order to get maximum bandwidth. Therefore, how to provide fair bandwidth sharing with low implementation complexity is a critical issue for high-speed networks. An active queue management mechanism, stateless fair admission control (SFAC), is proposed in this paper, which can provide good fairness on bandwidth allocation. Furthermore, the SFAC does not have to maintain per-flow state in each router. The main idea of the SFAC is that two admission thresholds can optimally change according to traffic variations. By comparing the admission thresholds with the hit number of each arrival packet, the SFAC is able to guarantee fair buffer occupancy for each flow. The SFAC employs a single first in, first out buffer, so that it can provide fair bandwidth sharing. In a word, the SFAC is completely stateless, so it possesses the great advantage of being easy to implement. Computer simulations concluded that the SFAC is capable of providing good fair bandwidth sharing under a range of traffic conditions. [ABSTRACT FROM PUBLISHER]

A compact broadband patch antenna is proposed in this paper for global ultra-high-frequency (UHF) RF identification (RFID) applications. The antenna is composed of four synchronous shorted patches that resonate at four different frequencies, broadening its impedance bandwidth. A central loop is incorporated to feed the four patches simultaneously, which provides the required input reactance for matching to the chip as well. Since the current of neighboring patch is vertical to each other that they can radiate well without canceling each other, the gain is stable over the whole frequency band. Prototype is fabricated and tested, which shows that the impedance bandwidth can cover the whole UHF RFID band (840 MHz - 960 MHz), and the read range is over 3 meters when EIRP is set to 30 dBm at the reader. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2653-2657, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25560 [ABSTRACT FROM AUTHOR]

This paper proposes a joint source channel coding scheme for robust real time transmission of H.264/AVC coded video over noisy channels and under bandwidth limitations. A new method of rate adaptation to the allowed maximum channel transmission rate which does not assume source rate control in the source coder has been proposed. This keeps system complexity reasonable and improves the perceived decoded video quality. These are desirable features for two-way video-conferencing using mobile hand-held devices. Data partitioning is used to code the source data. Then, unequal error protection is applied at the network abstraction layer. For robustness, we use joint optimization of forward error correction at the transmitter and error concealment at the source decoder. A low complexity and efficient algorithm of channel code rate allocation to the network abstraction layer units is then developed. Simulation results show that the perceived decoded video quality is improved for small levels of signal-to-noise ratio. [ABSTRACT FROM AUTHOR]

In this paper, TCP performance issues in bandwidth asymmetric networks are investigated. Related works to improve TCP performance in bandwidth asymmetric networks are introduced and analyzed. A new mechanism to improve TCP performance in two way traffic over asymmetric networks is also proposed in this paper, which can further improve TCP performance by assigning the bandwidth rates over the reverse link dynamically. Simulation results show that the new mechanism has better performance compared to existing algorithms in terms of good utilization of the existing resources and higher throughput. [ABSTRACT FROM AUTHOR]

The fairness concept has been widely studied in the area of data networks. The most well-known fairness criterion (max-min fairness) gives priority to the minimum-rate session. Kelly questioned its appropriateness in his works on the bandwidth sharing among the end-to-end flows and proposed another fairness criterion preferring short-distance flows to enhance the overall throughput, which is called the proportional fairness (PF). A simple scheduler achieving this objective was introduced in wireless access networks and revealed that it can achieve a good compromise between cell throughput and user fairness. Although it has received much attention for some time, research on its performance mainly depended on computer simulations. In this paper, we analyze the PF scheduler to obtain the cell throughput, which is a primary-performance metric, and extend the result to analyze the capacity of multiple-input-multiple-output systems. We evaluate the effect of various parameters on the throughput of the PF scheduler through the numerical analysis. [ABSTRACT FROM AUTHOR]

A novel meander coupled line power divider for wide band operation from 0.5 GHz to 2.5 GHz with reduced size for mobile application is proposed in this paper. The wide band operation of the coupled line power divider is obtained using open stubs and defected ground structures. The folding of the coupled line reduces the size of the power divider. The proposed power divider has 65% of size reduction in comparison with the existing power divider. All the S-parameters such as return loss, insertion loss, and isolation at different ports are simulated and measured. Bandwidth of 2 GHz is obtained. Both the simulated and measured results agree with each other. Hence it is useful for mobile phone application up to 4G. [ABSTRACT FROM AUTHOR]

The design of a frequency selective surface (FSS) screen constructed using a coupling configuration to implement a broadband microwave absorber is presented in this paper. The reflectivity representation recognizes the characterization of the absorber. Simulation and measurement results are presented and analyzed. A coupling FSS screen is introduced in order to obtain a better bandwidth and absorption. The bandwidth with the reflectivity below −10 dB could get 5.45-18 GHz, compared with the 6.28-18 GHz of the absorber with square patches FSS, provided that the thickness of the absorber is 4 mm. [ABSTRACT FROM AUTHOR]

Two planar metallic patch (MP) antennas with low profiles are investigated and compared in this paper. The MP of each antenna consists of metallic patch cells and it is centrally fed by a rectangular slot. Two modes with close resonance frequencies are excited, providing a quite wide bandwidth. The antenna principle is explained clearly through a parametric study. Simulated and measured results show that the MP antennas with profile of 0.06λ0 can obtain a 10 dB impedance bandwidth of ~32% and an average gain of ~10 dBi. [ABSTRACT FROM AUTHOR]

Novel double-sided printed dipole antennas are proposed and investigated in this paper. Two pairs of identical T-shape metallic loadings are connected to the traditional double-sided printed dipole, enhancing the operating bandwidth. Simulations show that the proposed printed dipole without the reflecting ground plane gives a bandwidth of up to 90.7% for |S11 | < -10 dB or 84.9% for |S11| < -15 dB, which is significantly greater than those of the traditional printed dipole. The proposed dipole is then applied to design a dual-polarized printed dipole antenna, mounted on a ground plane. Measurements for the prototype show a bandwidth of 68.8% for |S11 | < --10 dB, covering the entire TD-LTE band. The gain is about 6-8 dBi and the isolation is over 24 dB over the bandwidth. [ABSTRACT FROM AUTHOR]

This paper proposes the design and implementation of high gain array antenna suitable for GSM1800 and UMTS base stations. For this purpose, previously developed wideband, dual polarised antenna module has been used as the basic element of array antenna. The array antenna structure is designed, simulated, manufactured and measured. Network parameters (S-parameters) and radiation characteristics (pattern, gain) of the array antenna have been investigated. The operation bandwidth spans GSM1800 (1710-1880 Mhz) and UMTS (1910-2170 Mhz) bands. The simulations show good agreement with the measurement results that the array antenna has return losses of less than -15 dB and the channel isolation between ± 45° linearly polarised channels is below -25 dB within the operation band. Azimuth and elevation half power beamwidths (HPBW) are 63° and 7° respectively. Gain is around 18 dBi. [ABSTRACT FROM AUTHOR]

With the emergence of various broadband services, a lot of bandwidth fragments will be generated during the operation of services being mapped into optical channels, which will waste too many bandwidth resources and decrease the transmission performance of optical networks. Traffic grooming strategy in dynamic optical networks can optimise the utilisation of bandwidth resources and reduce the blocking probability. However, in the distributed control plane of automated switched optical networks, all the traffic grooming strategies are implemented in each control node, and resource collision will still occur because the same link resource may be used by two path computation requests or traffic engineering information flooded by open shortest path first-traffic engineering protocol may be not synchronous at each control node or signalling delay time is too long. To reduce the collision of resource, a unified control plane is designed based on path computation element (PCE) for Internet protocol over wavelength division multiplexing networks, and a novel PCE-based traffic grooming strategy is proposed in the framework of unified control plane. Based on this strategy, four PCE-based traffic grooming algorithms are proposed and compared with the distributed traffic grooming strategy without PCE on a simulation platform implemented using disperse event simulation tool OMNET++. [ABSTRACT FROM AUTHOR]

This paper presents a design of T-shaped slot antenna for ultrawideband (UWB) communications. Multiple resonances are generated and unified to form a large bandwidth from 2.5 to 10.5 GHz for S11 < -10dB by constructing open ended modified T-shaped slot antenna and by extending a small section of the microstrip feed line. The simulated result shows that it has good radiation patterns and pulse handling capabilities within the band of interest. [ABSTRACT FROM AUTHOR]

In this literature, we present a new method for estimating the coarse frequency offset in multi-band orthogonal frequency division multiplexing (MB-OFDM) based ultra-wideband (UWB) communication systems. The proposed training based coarse frequency offset (CFO) estimator performs an averaging of initial estimate over the multiple bands of transmission during estimation process. The proposed multi-band averaging provides an improved estimation of approximately three times for band group 1 (BG1) compared to our earlier proposed scheme. To prove the efficiency of the proposed scheme, the Cramer Rao lower bound (CRLB) of the estimation error is calculated and compared with the simulation results. We illustrate the performance of MB-OFDM system in terms of bit-error rate (BER) with multi-band averaged frequency synchronization (MBAFS) and compare with earlier reported results for 100,000 noisy realizations in UWB channel model 2 (CM2). [ABSTRACT FROM AUTHOR]

The effect of crosstalk avoidance codes on the throughput of fixed width communication channels is studied. Closed form expressions of the throughput which incorporate the dimensions of the interconnects and the wiring overheads incurred by such techniques are derived for lines under different buffering conditions. These formulae are utilized to optimize the bandwidth of constrained-area parallel buses under different latency and power constraints. Our results are confirmed by the simulations we have performed in Spectre for a UMC CMOS 90-nm technology. [ABSTRACT FROM AUTHOR]

Abstract: In this paper a novel prediction method and a communication protocol is proposed for distributed motion tracking systems, for example robot control system over the Internet based on on-line visual information. It is assumed that the trajectory generator part of the control system is connected to the low level controller through wide area network (WAN). In this case the variable network delay, packet losses, irregular packet arrival can severely influence the control characteristics (transient behavior and tracking performance) in a negative sense. The proposed prediction method is based on dynamic filters and it generates the trajectory on the control system side in the control periods when no new information on the time varying reference trajectory arrives through the network. The developed application level communication protocol is meant to keep the packet loss under a predefined limit even if the network bandwidth varies below the value required by the control application. Simulations and real-time experiments show that the prediction algorithm applied jointly with the proposed communication protocol can effectively compensate the effect of networked communication on control characteristics. [Copyright &y& Elsevier]

In this paper, we propose an expanded patching technique in order to reduce the server network bandwidth requirements to support true VoD services in VoD Systems. Double Patching, which is a typical multicast technique, ensures that a long patching stream delivers not only essential video data for the current client but also extra video data for future clients. Since the extra data may include useless data, it results in server network bandwidth wastage. In order to prevent a server from transmitting useless data, the proposed patching technique uses a new kind of stream called a linking stream. A linking stream is transmitted to clients that have received short patching streams, and it plays a linking role between a patching stream and a regular stream. The linking stream enables a server to avoid transmitting unnecessary data delivered by a long patching stream in Double Patching, so the server never wastes its network bandwidth. Mathematical analysis shows that the proposed technique requires less server network bandwidth to support true VoD services than Double Patching. Moreover, simulation results show that it has better average service latency and client defection rate compared with Double Patching. [ABSTRACT FROM AUTHOR]

Broadcast is an efficient and scalable method for resolving the bandwidth limitation in a wireless environment. There is a trade-off between clients' access time and throughput for update mobile transactions in on-demand data dissemination environments. Data scheduling at the fixed server can allow more transactions to commit while retaining the access time for each transaction. In this paper, we present a data scheduling scheme for both read only and update mobile transactions in pull-based broadcasting environments. Rather than consider access time, which is well studied elsewhere in [1, 2, 3], our concern is to examine the probability that a mobile transaction is able to avoid conflict and commit. Specifically, a set of formulas giving an analysis of this probability is examined. Furthermore, a report of a simulation study for validating these formulas is also provided. [ABSTRACT FROM AUTHOR]

Hybrid substrate integrated waveguides (SIWs) are proposed as an alternative low-cost interconnect solution to enable ultra-high-speed signal transmission. The SIW serves as a band-pass data transmission channel providing 15-GHz bandwidth. The hybrid structure utilizes the available low-pass frequency region below the cutoff frequency by adding striplines inside the waveguide. This technique of substrate reuse allows several independent data channels to be transmitted simultaneously through the hybrid structure. Hence, the channel capacity is increased without changing the overall waveguide footprint. Transition structures for routing striplines in the waveguide are designed and optimized through full-wave simulations. A number of test structures are fabricated to investigate data transmission using single and hybrid SIW interconnects. Experiments, as well as system simulations, demonstrate the capability of these interconnects for achieving ultra-high-speed data transmission. The hybrid waveguide system yields 15-Gb/s aggregate data transmission with excellent signal integrity characteristics. The proposed hybrid structure suggests an alternative solution for implementation of parallel data transmission systems with significant increase in the total channel throughput. [ABSTRACT FROM AUTHOR]

A novel broadband L-band patch antenna is presented. The proposed antenna consists of three layers, each containing a triangular patch of a different size. The layers are separated by substrates of equal thickness and permittivity. The antenna is fed through the lowest patch, with the upper patches fed parasitically. Both simulation and experimental results show relatively broadband characteristics. The antenna has a fair gain, comparable to that of single-layer patch antennas. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 66–70, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11286 [ABSTRACT FROM AUTHOR]

When designing printed wide-slot antennas, the shape or profile of the tuning stub is a key geometric structure that affects the impedance bandwidth of the antenna. This article introduces a new process for designing tuning stub shapes, which are the blended results of a diamond and a circle. By using different geometry shapes, the design could generate a series of bandwidths with a regular trend. Detailed investigations and analysis were conducted on some key geometry parameters to explore their impact on the impedance bandwidth of the antenna. To certify the new design method, several prototypes were simulated, developed, and measured. The experimental and simulated results showed good agreement with each other. The results indicate that by properly selecting various blended shapes, a BW range from 80.1 to 117.3% for a VSWR of less than 2 could be obtained, which provides a convenient model for a wideband antenna design. [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents the design of an ultra-wideband monopole antenna with a gain enhanced performance using a novel double split ring metasurface reflector. A circular patch configuration is used here as the radiating element for the simplicity and reliability of such structures. The antenna radiates well beyond the ulta wideband (UWB) frequencies but the performance enhancement using double split ring Metasurface reflector is within UWB frequency. The periodic array of dual split ring patches with varying split angles placed in a columnar arrangement is responsible for the metasurface structure to reflect effectively in phase-agreement over a broadband without affecting the impedance bandwidth of the principal radiator. With such a low profile setup (gap between antenna and reflector is in the order of at the lowest operating frequency of the antenna) the wideband gain-enhanced characteristic makes the design versatile enough for numerous practical applications. A high increment in the antenna gain performance (nearly 5.5 dB) is recorded over the UWB frequency range. Experimental results are found to be in good agreement with the simulations. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1296-1300, 2017 [ABSTRACT FROM AUTHOR]

These days there is a clear trend toward extending the reach of passive optical networks to cover large geographical areas, which enables reduction of the number of central offices and hence has the potential of cost saving in network operation. On the other hand, this reach extension necessitates the design of efficient dynamic bandwidth allocation schemes in order to tackle performance degradation caused by the increased propagation delay in long reach PONs. Among many existing approaches, the multithread- based DBA scheme where several bandwidth allocation processes are performed in parallel is considered one of the most effective options to improve network performance in LRPONs. We have found that without proper intercommunication between the overlapped threads, multi-thread DBA may lose efficiency and even perform worse than the conventional singlethread algorithm. With this in mind, this article reviews different inter-thread scheduling schemes for LR-PONs, and proposes a novel approach of integrating the key ideas of the existing ones. Extensive simulation results confirm that our proposed scheme can significantly improve DBA performance for LR-PONs under a variety of scenarios with consideration of different values of network load and reach. [ABSTRACT FROM PUBLISHER]

In this study, a wideband folded mushroom zeroth-order resonance (ZOR) antenna is presented. To obtain a wide bandwidth, the frequency of the TM010 (λ0/2) mode is down-shifted to the frequency of the ZOR mode by folding a mushroom structure without any additional structure. Thus, the folded mushroom antenna operates over two modes, resulting in a wide bandwidth. The antenna has a dimension of 0.365λ0 × 0.247λ0 × 0.182λ0 at the centre frequency. Its 10 dB fractional bandwidth is measured as 68.3%. The maximum gains of 3.32 and 3.41 dBi are measured at the ZOR mode and the TM010 mode, respectively. Finally, the measured results show good agreements with the simulated results. [ABSTRACT FROM AUTHOR]

A compact wideband 90^\circ differential phase shifter is developed by modifying ports termination in the Abbosh phase-shifter configuration. This novel phase-shifter arrangement consists of a 3-dB directional coupler with the coupled and transmission ports terminated with reactive loads. The proper reactance is found at the input of the coupled line section in which the remaining ports are open circuited. Both coupled sections utilize a multilayer broadside coupling microstrip–slot–microstrip tight coupler. A theoretical model is presented to explain the performance of the proposed phase shifter and design procedure. Further, the phase shifter was designed and manufactured. Results of calculation and measurement show that the developed circuit provides a 90^\circ differential phase shift with deviation less than \pm\4^\circ across the 3–7-GHz frequency band. [ABSTRACT FROM AUTHOR]

A sectoral Sierpinski Gasket fractal (SSGF) antenna is proposed for dual-band operation with wide-bandwidth covering GPS, DCS-1800, PCS-1800, UMTS, IMT-2000, Wireless broadband Internet Services (WiBro), Bluetooth, and WLAN bands. The SSGF antenna consists of volume 65.5 × 27 × 1.6 mm3. To analyze its performance, measurements are carried out. The proposed antenna model exhibits resonances in 1.51-3.39 GHz (2:1 VSWR BW 76.6%) and 5.31-6.32 GHz (2:1 VSWR BW 17.3%) bands with 2.5-5 dBi gain. Very good agreement is obtained between simulation and experimental results. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012. [ABSTRACT FROM AUTHOR]