ATM Environment Research Articles

Pixel level vacuum packaging for single layer microbolometer detectors with on pixel lens

Abstract This paper presents a new approach for fabrication of single layer microbolometer detectors featuring pixel level vacuum packaging together with a lens on the pixel. The proposed lens structure can be used to increase the fill factor of the detector so that the pixel size can be decreased without decreasing the minimum feature size in the detector which is a problem in single layer microbolometers. The designs of the lens and the fabrication process of pixel level vacuum packaged microbolometer detector together with this lens are given in the framework of this study. The optical and mechanical simulations of the structure are performed. The radius of curvature of the lens is optimized to be 25 μm and it is shown that the condensing efficiency is 100% for 3 μm lens-detector distance. The deflection in the lens structure is found approximately as 0.8 nm in 1 atm environment pressure, showing that the proposed structure is durable. The proposed structure increases the fill factor to twice of the original value without decreasing the minimum feature size in the fabrication processes, resulting in the same amount of improvement in the performance of the detector. This approach can also be used to increase the yield and decrease the fabrication cost of single layer and also standard microbolometers with small pixel sizes, as it integrates the vacuum packaging in the fabrication steps.

Analyzing buffer contents of space division output buffered multichannel switches

In digital communication systems, buffers are used for the temporary storage of digital information awaiting transmission via some communication channel(s). In this article, buffer analysis of space division output buffered switches operating in an ATM environment is presented. The switch is modeled as a discrete-time, batch arrival, multiserver queuing system, with infinite buffer and geometric service time. Probability Generating Functions (PGFs) of the system occupancy are derived for single server, two servers, and a general form for multiserver systems. Expectations for the corresponding random variables are obtained for different cases. Many numerical examples, which verify the results, are presented.

A Cockpit Point of View on "Human Factors" for a Changing ATM Environment

A Cockpit Point of View on "Human Factors" for a Changing ATM Environment

Effect of Non-Luminous Flame Radiation During Methanol Droplet Combustion

The effect of non-luminous thermal radiation on the combustion of a suspended methanol droplet in a low temperature (300 K) and low pressure (1 atm) environment is discussed in detail. Numerical results are obtained using a predictive, transient, two-phase, axisymmetric numerical model that includes surface tension effects. Radiation is modeled using the optically thin approximation with the product species CO2 and H2O as the radiating species. Results for combustion in a nearly quiescent atmosphere (initial Reynolds number 0.01) and initial droplet diameters in the range of 0.43 mm to 3 mm are presented. In agreement with the reported literature, it is shown that the effect of flame radiation is negligible when the initial droplet diameter is less than approximately 1 mm and becomes increasingly important for larger droplets. As a result, the average evaporation constant decreases with the initial droplet diameter. Radiation and surface tension combined as well as surface tension alone have a significant effect on the predicted extinction diameters of methanol droplets. However, when surface tension is neglected, radiation alone has a negligible effect on the prediction of the extinction diameter. The extinction diameter presents a non-linear variation with the initial droplet diameter for initially large droplets. The agreement with experimental results available in the literature is very good.

Performance analysis of an AAL multiplexer with dynamic bandwidth allocation in an IP/ATM environment

In this paper, we present a discrete-time queueing model with a Markov modulated batch Bernoulli process (MMBBP) as a bursty input traffic model of internet protocol packets in order to investigate the performance of a ATM adaptation layer (AAL) multiplexer with a finite buffer and a threshold-based dynamic bandwidth allocation scheme (DBAS). As a deterministic service time, we use the segmentation processing time devoted to a cell payload in the AAL multiplexer. This service time consists of several slot times and varies in line with threshold levels of the buffer contents. In an MMBBP process, the arrivals during a slot time occur as batch Bernoulli processes with a general distribution of batch sizes varying according to the phases of a Markov chain. We obtain the loss probability and the mean delay of an arbitrary packet. We present some numerical results to show the effects of the burstiness and thresholds on the performance of the AAL multiplexer with a DBAS. Scope and purpose The model which we present takes its origin in the research of appropriate traffic management schemes for carrying Internet protocol (IP) traffic on ATM networks. Due to the connection-oriented nature of ATM and unpredictable bursty characteristics of IP traffic, we need some dynamic schemes in the AAL multiplexer of an interworking unit such as a router in order to support a bandwidth allocation algorithm for IP traffic over ATM backbone networks. Discrete-time finite queueing model has gained to describe queueing multiplexer in an ATM environment where time is slotted into one cell transmission time. Recently, many works reveal the bursty nature of packet arrivals to the IP packet multiplexer. Therefore, we focus on a discrete-time finite queueing model MMBBP/D/1/K of the AAL multiplexer with a threshold-based DBAS in order to control the bursty IP traffic transferred to ATM networks. We analyze the presented model by using the classical supplementary variable method in queueing theory. As a result, we obtain the steady-state queue size distribution at an arbitrary time point and the loss probability and the mean delay of an arbitrary packet.

Analysis of a finite‐buffer bulk‐service queue with discrete‐Markovian arrival process: D‐MAP/Ga,b/1/N

AbstractDiscrete‐time queues with D‐MAP arrival process are more useful in modeling and performance analysis of telecommunication networks based on the ATM environment. This paper analyzes a finite‐buffer discrete‐time queue with general bulk‐service rule, wherein the arrival process is D‐MAP and service times are arbitrarily and independently distributed. The distributions of buffer contents at various epochs (departure, random, and prearrival) have been obtained using imbedded Markov chain and supplementary variable methods. Finally, some performance measures such as loss probability and average delay are discussed. Numerical results are also presented in some cases. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 345–363, 2003.

Performance analysis of finite buffer discrete-time queue with bulk service

Discrete-time queues are extensively used in modelling the ATM environment at the cell level. In this paper, we model a single-server queue with finite buffer space in a discrete-time environment where the services are performed in batches of maximum size ‘b’ with a minimum threshold value ‘a’. The analytic analysis of the model is carried out for the both arrival first (AF) and departure first (DF) management policies and distributions of buffer content at various epochs have been obtained. The system performance measures such as average buffer content, average delay and probability of blocking are discussed. A comparative study of AF and DF management policies on certain performance measures is also presented. Scope and purpose B-ISDN and in particular ATM networks are designed in order to transfer and switch all type of information services such as voice, data and video communications. As these systems operate on a discrete-time basis, many classical results of queuing theory which are used in performance analysis cannot be applied and hence require a fresh investigation. The purpose of this paper is to analyse a discrete-time finite buffer queue with general bulk service rule which may be useful to system designers and other practitioners involved in investigating the performance of communication systems based on B-ISDN.

Error Resilient Two-Layer H.263-based Codecs for ATM Environments

The introduction of new multi-media services and the enhancement of the existing services forced the existing networks to their performance limits. Most of the networks today face the problem of bandwidth limitation. ATM networks solve the problem of bandwidth bottleneck by the introduction of statistical multiplexing and priority switching. Many video coders/decoders (codecs) have been designed to suit this new technology [1–6]. Some of these codecs are designed to increase the resilience of the codec to cell loss as well as the sharing ability of the assigned bandwidth by implementing various layering techniques. Other multi-media services designers prefer to implement cell concealment techniques at the decoder side to combat cell loss [7]. This paper presents new two-layer error resilient video codecs based on the classical TWIN-H.261 and the Inter-Enhance H.261 video codecs [2–4]. A study of the performance of the proposed codecs is included in this paper with a comparison with the other classical two-layer codecs in terms of the reconstructed image quality, the resilience to cell loss, the bit rate produced and the codec complexity.

A comprehensive approach to signaling, transmission, and traffic management for wireless ATM networks

We propose and evaluate a signaling and transmission algorithmic system for wireless digital networks, in conjunction with a Traffic Monitoring Algorithm (TMA) for dynamic capacity allocation in multimedia ATM environments. The deployed signaling protocol is stable, and two transmission techniques are compared: a Framed Time-Domain Based (FTDB) technique and a Framed CDMA (FCDMA) technique. The overall signaling/transmission/traffic monitoring proposed system has powerful performance characteristics, while the TMA-FTDB combination is superior to the TMA-FCDMA combination in environments where message lengths are relatively short and the speed of the transmission lines is relatively low. We also evaluate a system deploying the Ethernet protocol as a signaling protocol, instead. In the presence of relatively tight admission delay constraints in signaling, the latter is significantly inferior to our proposed signaling technique. As the above admission delay constraints diminish, the Ethernet protocol breaks down, while our proposed signaling technique maintains its high performance characteristics.

Large impact of temporal/spatial correlations on per-session performance measures: single and multiple node cases

The problem of evaluating the end-to-end performance in an ATM environment is known to be difficult and largely open. Since applications may have very different quality of service (QoS) requirements, a performance measure associated with a random cell would not necessarily reveal the impact of multiplexing on the QoS of a specific application. For this reason, it is important that the traffic stream of interest be tagged and its distortion due to multiplexing be evaluated; for analysis purposes the co-existing traffic is aggregated and forms the background traffic. In the past studies the background traffic has been assumed to be uncorrelated and be diverted after a single multiplexing stage. The objective in this work is to evaluate the impact of temporal and spatial correlations on the end-to-end performance of a tagged traffic stream. Such correlations can be significant due to temporal correlation in the background traffic or partial commonality in the routing path (background traffic is not necessarily diverted). A binary queuing activity indicator (QAI) is proposed in this work to provide for a simple mechanism to capture these correlations. Results derived for various delay metrics of a tagged traffic stream associated with single and multiple nodes show the substantial impact of the spatial/temporal correlations. Furthermore, they suggest that the proposed QAI indicator is capable of capturing such correlations.

ATM connection admission control using pRAM based artificial neural networks

As they learn from observed data, neural networks have found many applications in communication networks. Here, a neural network for connection admission control (CAC) based on the probabilistic-RAM (pRAM) neuron model is presented. Because pRAM neural networks can be implemented in hardware easily and at a low cost, they make excellent controllers in the ATM environment. The performance of such a controller is analysed through simulations, and the results are compared with the Equivalent Capacity of Connections CAC algorithm. The results show that, the proposed hardware-based controller guarantees the required quality of service (QoS) and at the same time provides an improvement in network utilization.

TCP ACK Pacing in ATM networks

An important concern in today's networks is the performance of the TCP/IP transport protocol. Since studies have shown that TCPs throughput and fairness levels can be low in various network scenarios, it is necessary to devise efficient, robust schemes to enhance its performance. Although changes to the protocol's functionality itself are being considered, this may not be a feasible alternative in the short-to-medium term. Recently, various ACK pacing algorithms have been developed for ATM environments and initial findings indicate significant overall benefits. Nevertheless, the performance of such schemes under dynamic link conditions arising from heterogeneous (interfering) traffic profiles needs to be studied. Here, the performance of a robust ACK pacing scheme is analysed under such conditions. Results for a wide range of network scenarios show significantly improved fairness levels and reduced buffer size requirements, even under very challenging conditions.

Multicast forwarding over ATM: Native approaches

Multicasting is growing in importance as new multimedia applications are devised. Throughout this article, multicasting is understood as the efficient multipoint-to-multipoint transmission of information (in terms of network resource consumption) between the members of a group. Most multicast services have been designed up to now to work over connectionless environments. The approach adopted by connection-oriented networks has been to try to imitate these connectionless multicast schemes with the aim of supporting IP multicast or network-layer broadcast. However, these solutions present drawbacks in terms of delay or signaling overhead. The goal of native ATM multicasting is to provide multicast communications support by taking into account the characteristics of ATM. Therefore, the design philosophy of multicast must be rethought by making it more suitable for connection-oriented networks. Native ATM multicasting is based on mechanisms implemented at the switches to allow the correct ATM-layer multicast forwarding of information. These mechanisms seek to avoid the delay and signaling problems of current solutions, e.g., LAN emulation and IP multicast over ATM. This article provides a survey of the literature on the strategies that offer multicast communications in ATM environments, with special stress on native ATM multicast forwarding mechanisms. Other aspects, such as signaling, quality of service, traffic control, and routing, are not addressed in detail in this article.

Multiservices MAC-protocol for wireless ATM

ATM is the future networking technology in the area of broadband networks. Using fiber optical cabling offers high bandwidth and low error rates. It is supposed to support different kinds of services, e.g., file transfer, videoconferencing, and speech transmissions. To support seamless end-to-end quality of service in a mobile environment a suitable extension to the fixed network part is necessary. In a wireless ATM environment the medium access protocol takes a prominent position. It is responsible for an efficient and fair media access on the shared radio resource. Due to the limited available bandwidth and the much higher error rates on the radio link special provisions must be provided. The compliance of traffic contracts for connections with different quality of services is the aim of our proposed protocol. This is the base of true end-to-end services with quality of service assurance in wireless ATM.

Call–burst blocking and call admission control in a broadband network with bursty sources

In this paper we consider call–burst blocking and call admission control in a broadband network with bursty sources. We assume a multiple-link network with several classes of calls, each class following a fixed path in the network and requiring a fixed number of channels from the links on its path. The arrival of each class of calls is according to a Poisson process and the calls alternate between On and Off periods during the time that they are in the system. At the end of each On period, a call either terminates or begins a new Off period according to a Bernoulli trial. During the Off periods calls release the channels that they are holding which might be assigned to the other On calls, a form of burst multiplexing. A new call is accepted to the system only if the burst-blocking probabilities remain acceptable. It is shown that the product-form solution still applies in the new system and we derive a multi-dimensional recursion to calculate the joint link occupancy distribution. Call and burst blockings as well as probability distribution of the number of burst blockings experienced by each class of calls have also been determined. We determine a simple decision mechanism for call admission. The numerical results show that the burst multiplexing increases the maximum load that the system may handle substantially compared to permanent assignment of the channels. We also discuss the implementation of this model in an ATM environment.

Multicast for RSVP switching: An extended multicast model with QoS for label swapping in an IP over ATM environment

The ubiquity of IP associated with the acknowledgment of ATM as a key switching technology has motivated an increasing interest towards the design of a more efficient way of operating IP over ATM networks. This approach is known under the name Label Swapping. A few studies have addressed the primary issue of providing simultaneously quality of service and multicast. We propose a solution where we mix an RSVP architecture with one Label Swapping technique called IP Switching. We discuss problems that arise when using cut-through associated with an RSVP multicast model and propose an application for an IPv6 environment over an ATM switching hardware.

Low-bit-rate voice and telephony over ATM in cellular/mobile networks

A new ATM AAL2 to support low-bit-rate and delay-sensitive applications in an ATM environment has been approved by the ITU-T and ATM Forum. AAL2 allows multiplexing of voice/data packets (minicells) from different users in a single ATM connection, thus improving the utilization of the network resources. This article identifies issues related to AAL2 such as the application environment, the gain obtained by multiplexing voice packets from different users on a single ATM connection, buffer requirements, and cell assembly delay. To analyze these issues, we modeled and simulated ATM trunking between a base transceiver station and the mobile switching center. The performance simulations show that the multiplexing gain obtained by AAL2 is significant, and the output buffer requirement at the ATM node is small. In addition, the results show that a timeout mechanism is needed to limit the ATM cell assembly delay in order to meet the delay requirements of real-time traffic such as voice.

Congestion detection in ATM networks

Many systems in ATM environments require the queue to be monitored for impending congestion before it happens. In this paper, we characterize impending congestion by measuring how long the queue length has exceeded a certain threshold. We present a new performance measure called the conditional overflow probability which gives a quantitative measure on the congestion state. We develop a matrix analytic model to compute the conditional overflow probability and the profile curve.

Performance analysis of a multiplexer with the threshold based overload control in ATM networks

In this paper we analyze the performance of a statistical ATM multiplexer with bursty input traffic and two thresholds in the buffer by using queueing model. Two priority levels are considered for source traffic, which is modeled by Markov Modulated Poisson Process to represent the bursty characteristics. Service time distributions of two priority sources are assumed to be same and deterministic for ATM environment. The partial buffer sharing scheme with one threshold may experience a sensitive state change around the threshold. But the proposed multiplexer with two thresholds avoids this hysterical phenominon to improve the system operation.

BLAST: broadband lightweight ATM secure transport for high-performance distributed computing

This paper investigates the use of ATM for cluster-based computing. The need for a native ATM API is discussed as well as the performance of message passing libraries (MPL) that are written to use such an API to exploit the advantages of a high-speed network for cluster-based computing. The MPLs offer a standard interface, such as PVM or MPI, and interoperate with existing TCP/IP- and UDP/IP-based versions in addition to the ATM API environment. The interoperability extensions made to two MPLs, MPI and Prowess, which allow a hybrid environment of both ATM and TCP-based legacy network technology will be described. Shared object space (SOS), an extension to the MPLs, is described that helps support the geographically distributed computing (GDC) environment through latency hiding. It allows a user to develop applications in a shared memory type of environment. The native ATM API which supports cluster-based computing is described in this paper. This API provides a reliable transport interface to the MPL which has been optimized for an ATM environment. The transport protocol is a low-state design that optimizes the performance based on the available bandwidth, buffer constraints, propagation delay characteristics and security requirements of a particular connection. © Elsevier Science B.V.