Passive Bandwidth Research Articles

Passive Available Bandwidth Estimation Based on Collision Probability and Node State Synchronization in Wireless Networks

In wireless networks, available bandwidth estimation is challenging because wireless channels are used by multiple users or applications concurrently. In this study, we propose a passive measurement scheme to estimate the available bandwidth in 802.12 wireless networks based on the combination and modification of two existing schemes, Distributed Lagrange Interpolation Based Available Bandwidth Estimation (DLI-ABE) and Accurate Passive Bandwidth Estimation (APBE). The proposed scheme uses the channel busy state, which is affected by transmitting or receiving processes caused by carrier sensing. Therefore, the sender and the receiver node should be synchronized using various states that can be affected by other nodes. Moreover, the proposed scheme was developed with the involvement of relevant calculation of possible overhead caused by control messaging that occurs in the Media Access Control (MAC) layer and collision probability caused by data flow from hidden nodes. The result showed that the proposed scheme can estimate the available bandwidth of wireless networks more accurately than DLI-ABE and APBE.

A Comparative Analysis of Universal Filters using Current Conveyors

Objectives: Current mode of operation is drawing the attention of many researchers due to their potential advantages such as wider Bandwidth, greater gain, higher slew-rate, etc., So, the design of Universal filters in current mode is essential keeping in view of power, Bandwidth. Methods: This paper concentrates on the analysis of some of the Universal filter Topologies which are realized using second generation current conveyor. For each Topology, the detailed mathematical analysis is carried out using circuit analysis techniques.The transfer fucntion expressions is derived. The effects of floating and grounded point passive elements is brieffy discussed with respect to hardware complexity, Quality factor and resonat angular frequency. Findings: The main objective of the paper is to analyze and compare various universal filter topologies. The objective of the paper also focus on the selection of the current conveyor by studying various generations in it. The Universal filters are used to act like low pass, High pass Band pass and Band reject filters. The merits and demerits of each Topology is compared.It has been observed that Topology I uses as minimum number of componenets as possible. There is no independent control of Q-factor in all topologies. All current conveyors and different Topologies are simulated in MULTISIM 13.0. Application: The proposed circuits finds applications in many areas such as communication, controls, Signal processing, Instrumentation. The work can be extended to design universal filter circuits with lesser passive componets, better Q and Bandwidth values.

Pattern Prediction and Passive Bandwidth Management for Hand-over Optimization in QoS Cellular Networks with Vehicular Mobility

In wireless networking, the main desire of end-users is to take advantage of satisfactory services, in terms of QoS, especially when they pay for a required need. Many efforts have been made to investigate how the continuity of services can be guaranteed in QoS networks, where users can move from one cell to another one. The introduction of a prediction scheme with passive reservations is the only way to face this issue; however, the deployment of in-advance bandwidth leads the system to waste resources. This work consists of two main integrated contributions: a new pattern prediction scheme based on a distributed set of Markov chains, in order to handle passive reservations, and a statistical bandwidth management algorithm for the reduction of bandwidth wastage. The result of the integration is the Distributed Prediction with Bandwidth Management Algorithm (DPBMA) that is independent from the considered technology and the vehicular environment. Several simulation campaigns were conducted in order to evaluate the effectiveness of the proposed idea. It was also compared with other prediction schemes, in terms of system utilization, accuracy, call dropping, and call blocking probabilities.

Unified routing protocol based on passive bandwidth measurement in heterogeneous WMNs

AbstractThe past few years have witnessed a surge of wireless mesh networks (WMNs)‐based applications and heterogeneous WMNs are taking advantage of multiple radio interfaces to improve network performance. Although many routing protocols have been proposed for heterogeneous WMNs, most of them mainly relied on hierarchical or cluster techniques, which result in high routing overhead and performance degradation due to low utilization of wireless links. This is because only gateway nodes are aware of all the network resources. In contrast, a unified routing protocol (e.g., optimal link state routing (OLSR)), which treats the nodes and links equally, can avoid the performance bottleneck incurred by gateway nodes. However, OLSR has to pay the price for unification, that is, OLSR introduces a great amount of routing overhead for broadcasting routing message on every interface. In this paper, we propose unified routing protocol (URP), which is based on passive bandwidth measurement for heterogeneous WMNs. Firstly, we use the available bandwidth as a metric of the unification and propose a low‐cost passive available bandwidth estimation method to calculate expected transmission time that can capture the dynamics of wireless link more accurately. Secondly, based on the estimated available bandwidth, we propose a multipoint relays selection algorithm to achieve higher transmission ability and to help accelerate the routing message diffusion. Finally, instead of broadcasting routing message on all channels, nodes running URP transmit routing message on a set of selected high bandwidth channels. Results from extensive simulations show that URP helps improve the network throughput and to reduce the routing overhead compared with OLSR and hierarchical routing. Copyright © 2016 John Wiley & Sons, Ltd.

An in-depth study of LTE

With lower latency and higher bandwidth than its predecessor 3G networks, the latest cellular technology 4G LTE has been attracting many new users. However, the interactions among applications, network transport protocol, and the radio layer still remain unexplored. In this work, we conduct an in-depth study of these interactions and their impact on performance, using a combination of active and passive measurements. We observed that LTE has significantly shorter state promotion delays and lower RTTs than those of 3G networks. We discovered various inefficiencies in TCP over LTE such as undesired slow start. We further developed a novel and lightweight passive bandwidth estimation technique for LTE networks. Using this tool, we discovered that many TCP connections significantly under-utilize the available bandwidth. On average, the actually used bandwidth is less than 50% of the available bandwidth. This causes data downloads to be longer, and incur additional energy overhead. We found that the under-utilization can be caused by both application behavior and TCP parameter setting. We found that 52.6% of all downlink TCP flows have been throttled by limited TCP receive window, and that data transfer patterns for some popular applications are both energy and network unfriendly. All these findings highlight the need to develop transport protocol mechanisms and applications that are more LTE-friendly.

A New Markovian Prediction Scheme for Resource Reservations in Wireless Networks with Mobile Hosts

Nowadays, mobile service requests in wireless networking are aimed to the benefit of a good level of satisfaction for the received Quality of Service (QoS) guarantees. In this paper, a new prediction algorithm is proposed, for the pre-reservation of passive bandwidth, when mobile users moves under radio coverage that can be considered as a cellular one (GSM, UMTS, WLAN clusters, etc.). The Hidden Markov Chains (HMC) theory is used to design the predictor, as the main component of the proposed idea, that does not depend on the considered transmission technology, mobility model or vehicular scenario. Mobile ReSerVation Protocol (MRSVP) has been used in order to realize the active/passive bandwidth reservation in the considered network topology. Different simulation campaigns have been carried out in order to appreciate the benefits of the proposed idea.

Available Bandwidth Estimation in Network-Aware Applications for Wireless Campus e-Learning System

The constraint of a wireless network has motivated many researchers to develop network-aware applications that can dynamically adjust the users' demand based on network resources. For this to happen, applications need to have some mechanism that can estimate the network bandwidth by simply adjusting their behavior based on the collected network characteristics information. In the past, there have been several proposals that provide passive and active bandwidth estimation approaches for wired and wireless network. However, little effort has been spent to address the crucial issues of reliability and congestion control especially in a wireless network environment, which stay as a sticking point for the success of network-aware application. This paper focuses on providing accurate, low-intrusiveness, and fast-convergence time bandwidth estimation for network-aware application architecture. The experimental results validate the efficiency of the proposed solution in terms of accuracy, intrusiveness, and timelines.

40-Gb/s Package Design Using Wire-Bonded Plastic Ball Grid Array

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A 40-Gb/s packaging solution that uses low-cost wire-bonded plastic ball grid array (WB-PBGA) technology is presented. Since such a high speed was beyond the reach of conventional package designs, a new design methodology was proposed—discontinuity cancellation in both signal-current and return-current paths. The 3-D structures of bonding wires, vias, solder ball pads, and power distribution networks were optimized for the discontinuity cancellation. Two versions of four-layer WB-PBGA packages were designed; one according to the proposed methodology and the other conventionally. The proposed design methodology was verified with full-wave simulation, passive bandwidth measurement, time domain reflectometry (TDR), eye diagram measurement, and jitter analysis. </para>

Measurement-based TFRC: improving TFRC in heterogeneous mobile networks

As a well-known multimedia stream transport protocol, TFRC provides smooth transfer rate under stable network conditions, and achieves good fairness to TCP. However, it is not flexible in heterogeneous mobile networks because the available bandwidth varies rapidly. This paper proposes a measurement based TFRC (MBTFRC) protocol, which uses passive bandwidth measurements at the receiver to improve the flexibility of TFRC. In addition, a window-based EWMA filter with two weights is used to achieve stability and fairness simultaneously. Simulation results verify the flexibility, stability and fairness of MBTFRC

Continuously tunable external-cavity diode laser with a double-grating arrangement

A new external-cavity diode laser system based on an extended version of the Littman configuration is investigated. In our laser system the tuning mirror is replaced with a second grating mounted at the Littrow angle. This double-grating design provides a smaller passive bandwidth than the grating-mirror configuration, which is used to compensate for the large angle-of-incidence-dependent losses of the grazing-incidence grating. This results in a broader continuous tuning range with an improved mode stability. Because two laser diodes, emitting at 820 and 775 nm, respectively, are used, the external-cavity laser is continuously tunable without mode hops across 35 nm at 820 nm and 27 nm at 775 nm. Such a laser was used to measure the absorption lines of the oxygen A band around 762 nm. The complete R - and P -rotational branches of the b summation operator(g)(1) (+)(nu(??)=0)?X (3) summation operator(g)(-)(nu (?)=0) transition were recorded in a single-wavelength scan.

Development and theoretical modeling of a broadband, tunable, pulsed dye laser

An excimer-laser pumped, tunable dye laser for broadband emission has been constructed for a novel molecular-beam experiment. By using Littrow prisms of different refractions as the dispersive elements, bandwidths from 0.7-1.5 nm with a tuning range of 40 nm were obtained. Pulse-to-pulse spectra were measured with a grating spectrometer-CCD camera combination, and the statistical analysis demonstrated the good stability. A ray-tracing model was used to calculate the passive bandwidth for different configurations. Augmented by dynamic considerations, the model can be used to approximate very well the dependence of the active bandwidth on the pump power, and to estimate the relative active bandwidths for different prism materials.

The Coupled-Cavity Transmission Maser- Engineering Design

The experimental design of an X-band microwave maser amplifier which uses a new type of slow-wave circuit is described. A detailed theoretical analysis of the circuit is presented in a companion paper. The slow-wave circuit consists of a cascade of iris-coupled ruby resonators separated by garnet isolators. This unit provides significant reduction in size and weight over previously reported maser slow-wave circuits. The microwave properties of the solid ruby resonator are treated in detail, and the passive bandwidth of the single transmission cavity and its relation to the iris susceptance are shown. Experimental techniques involved in obtaining and measuring precise iris susceptance are presented. A step-by-step procedure for designing an amplifier having a given gain and tuning range is also presented. Typical performance characteristics include a gain of 30 db, instantaneous bandwidth of 25 Mc and a noise temperature of 15/spl deg/K. An electronic tuning range of 200 Mc has been achieved in one configuration with a 20 db gain and a 25-Mc bandwidth. The weight of the maser-dewar unit, filled with 6 liters of helium for 24 hours of operation is less than 40 pounds. The design of the dewar enables the cryogenic system to work over a wide range of vertical angles, thus facilitating the use of the maser at the feed of a large steerable antenna.

Theoretical and experimental analysis of the cavity maser

An exact analysis of the gain function of the cavity maser is made and is presented in graphical form suitable for correlation with experiment. Combined with measurements of the reflection coefficient of the passive cavity, and gain and bandwidth of the maser, the results yield accurate values for the unloaded, external and magnetic Q-factors of the cavity maser. The analysis also applies to any other resonant one-port device, e.g. a parametric amplifier.